HIGH-SPEED RESPIRATORY THERAPY UNIT WITH CONTACTLESS DETECTION AND CONTROL.

Abstract

The systems, devices, and methods described herein relate to the delivery of breathable gas at high velocity to a patient using a base unit and an auxiliary unit configured to be removably mounted on or at least partially mounted within the base unit. The base unit has several couplings for enhanced control and sensing of the auxiliary unit and its components, wherein the couplings are configured to be non-contacting with the corresponding components of the auxiliary unit and / or otherwise configured to minimize operational defects or improve efficiency. The non-contact couplings include induction heating, capacitive level sensing, a magnetically coupled rotor pump, an RFID tag and reader, and Hall effect sensing.Breathable gas can be delivered at high speeds by adjusting the breathable gas flow rates based on the dimensions of a nasal cannula used to direct the breathable gas to the patient's nose.

Description

High-speed respiratory therapy unit with contactless detection and control Cross-reference to related applications This application claims priority to and the benefit of each of U.S. Provisional Patent Application No. 62 / 988,583, filed March 12, 2020, and entitled “SYSTEMS AND METHODS FOR HIGH-VELOCITY RESPIRATORY THERAPY”; U.S. Patent Application No. 16 / 901,902, filed June 15, 2020, and entitled “RESPIRATORY THERAPY UNIT WITH NON-CONTACT SENSING AND CONTROL”; and U.S. Provisional Patent Application No. 63 / 125,005, filed December 14, 2020, and entitled “RESPIRATORY THERAPY UNIT WITH NON-CONTACT SENSING AND CONTROL,” the entire contents of which are each incorporated herein by reference. Background of the invention Respiratory distress can impact patients in a wide variety of ways, from a variety of causes, and with indications that can range from mild to moderate to severe. In some situations, respiratory distress arises from the progression of typical asthma or temporary airway deterioration; in other cases, it may arise from hereditary sources, the result of ongoing environmental exposure, or the consequence of non-pulmonary diseases. Chronic obstructive pulmonary disease (COPD) is a major contributor to respiratory distress as it can cause limitations through inflammation, changes in small airways, or parenchymal destruction. Lung elasticity may be decreased, which can inhibit the lungs' ability to expand and distend during breathing.The portion of the lung responsible for gas transport (oxygen and carbon dioxide) can also be damaged, with a substantial reduction in breathing efficiency. As a result, a patient may experience numerous harmful symptoms, which may increase in severity as the condition worsens. Hypercapnia and hypoxemia are common clinical signs of acute or chronic respiratory conditions, and shortness of breath (dyspnea) is a common symptom of these conditions. Given the rising costs of healthcare, patients with serious conditions can place a particularly high burden on the healthcare system, especially if there is a need for long-term care. Another important clinical cause of respiratory distress is acute respiratory distress syndrome (ARDS), which is the severe impairment of pulmonary oxygenation. The level of severity of ARDS depends on the stages of hypoxemia experienced by the patient (measured by the ratio of blood oxygen level to the amount of inspired oxygen required to achieve that blood oxygen measurement) and can range from mild (200 mm Hg < PaO2 / FIO2 < 300 mm Hg), to moderate (100 mm Hg < PaO2 / FIO2 < 200 mm Hg), and severe (PaO2 / FIO2 < 100 mm Hg). ARDS is often triggered by the body’s immune response to infection or injury to the lungs. In the case of COVID infection, the host’s immune system produces an inflammatory response in an attempt to kill the virus, leading to a cytokine storm and organ damage, with a particular effect on the lungs. Common causes of ARDS include sepsis (serious infection in the lungs and other organs), pneumonia, pancreatitis, side effects of blood transfusions, severe trauma and burns (especially inhalation injury due to exposure to high concentrations of fumes or smoke), and drug overdoses. A common pathology of ARDS is a leak in the tissue barrier between the alveoli of the lungs and the capillaries of the lungs, causing fluid from the capillaries and interstitial fluid to leak into the lungs, preventing the affected area of ​​the lung from performing proper gas exchange. In the case of ARDS, the diffusion barrier may break down, allowing fluid to leak into the alveoli of the lung.The consequences of a breach in the barrier can be severe, including pulmonary edema through the disrupted diffusion barrier, pressurization and collapse of the affected alveoli, fibrosis, and additional inflammation (cytokine storm) as the body rushes cytokines to the affected area in an attempt to contain the injury, further exacerbating the condition. Patients can progress very rapidly after an incident and may die from multiple organ failures (lung, heart, kidney). The body responds to these challenges by increasing the work of breathing, which will eventually result in fatigue and failure. Patients with COPD are also prone to developing ARDS, caused by increased work of breathing due to symptoms of shortness of breath or chronic cough, hyperventilation, and inflammation of the lungs and airways. Individuals with end-stage or stage 4 COPD, who are more likely to develop a lung infection, are at high risk for ARDS. ARDS is one of the most severe complications caused by COVID-19-related pneumonia due to infection with the SARS-CoV-2 virus. Early symptoms may include increased respiratory rate, flushing and other color changes around the mouth and airways, difficulty exhaling, nasal congestion, sweating, wheezing, and other symptoms. This constellation of presenting signs and symptoms is common among patients with respiratory distress and represents the underlying requirement to relieve the work of breathing. Patients with respiratory distress or other respiratory conditions, whether mild, moderate, or severe, are frequently treated with respiratory assist devices (VADs) that deliver supplemental breathing gas to the patient to support oxygenation or ventilation, or to provide medication. Such devices may deliver gas to the patient using high-flow therapy (HFT). HFT devices deliver breathing gas at a high (usually supraphysiological) flow rate via an interface such as an open nasal cannula to increase the patient's fraction of inspired oxygen (FiO2), decrease the patient's work of breathing, or both.Increasing FiO2 or decreasing the work of breathing helps the patient recover from respiratory complaints, such as shortness of breath or bronchospasm, or provides support for non-pulmonary etiologies of respiratory distress, such as acute decompensated heart failure. Some HFT devices warm and humidify the delivered breathing gas for medical reasons (e.g., to maintain tissue flexibility in surfactant-deficient patients, or to preserve mucosal integrity) or to reduce patient discomfort. HFT systems typically operate at a high volumetric flow rate but are wide-bore cannula designs, so the therapeutic breathing gas is delivered at a low velocity. Some HFT systems use membrane humidification to humidify the breathing gases. The use of a membrane humidifier increases the system's pressure requirements because membrane humidifiers resist airflow more than non-membrane humidifiers. Additionally, some HFT systems use nasal cannulae with small-bore nasal prongs to increase the velocity of the breathing gases entering the patient's airway. However, such cannulae further increase the required pressure compared to a system using large-bore nasal prongs or a face mask.These increased pressure requirements of such HFT systems necessitate the use of wall air or a large compressor which may limit HFT from being delivered at a high velocity sufficient to address moderate or severe respiratory conditions. Some respiratory therapy devices use a ventilator and a non-membrane humidifier to create humidified high-flow therapy, typically at low velocities for the treatment of patients with mild conditions. Such non-membrane humidifiers are essentially heated water vessels through which gases are channeled. These ventilator-based systems use larger-bore cannulas to reduce pressure requirements. However, large-bore cannulas do not flush CO2 from a patient's airway as effectively as small-bore cannulas and are often unsuitable for use in treating patients with moderate to severe respiratory conditions. Additionally, HFT devices typically include a display showing the current breathing gas flow rate, but do not make other system parameters available to the user.Accordingly, the user is able to adjust the breathing gas flow rate, but cannot control other system parameters. These respiratory therapy devices can be configured to allow the gases to be humidified before delivery to the patient to avoid drying out the airway. Conventional humidifiers for breathing gas suffer from several disadvantages. The water used to humidify the gas must be heated. Traditionally, this has required a resistive heater in a main unit that is in contact with a conductive plate on the outer surface of an auxiliary unit, which is also in contact with the water inside the auxiliary unit. Either the heater in the main unit or the heater plate in the auxiliary unit can be hot enough to injure a caregiver if the auxiliary unit is removed without sufficient time to cool. In such configurations, heat is generated in the main unit and conducted to the water.By definition, the heater must be warmer than the desired water temperature, and the heater may not only heat the water. Conduction in the main unit and convection with the surrounding air are both sources of heat loss to the environment. Proper function of this type of system also typically relies on a good conduction path for heat from the resistive heater to the heater plate and onward to the water. The conduction path typically works best when both plates are flat to achieve intimate contact. Any surface anomalies or surfaces that are not flat and pressed together tightly enough can increase the temperature the heater must reach to achieve the desired heat transfer rate. This also increases heat loss from the system and can endanger users and caregivers. Humidifier systems require a water reservoir that can refill the device as water is consumed. In most devices, the water flow is controlled by a float that allows water to enter when the device has depleted water. These are prone to failure, which can allow too much water to enter. Additionally, when the device is inactive for extended periods, the floats tend to leak water into the system. This water can end up in the gas passages and then be administered to the patient through the patient interface when the device is turned on, which can be uncomfortable or dangerous. The water chamber in the device should be vented to allow air to escape as water enters. The vent is typically a membrane material that allows air to pass through while preventing water from entering.A float failure can cause the membrane material to become submerged in water, which over time can deteriorate the membrane and prevent air from escaping. This can eventually prevent water from entering the system and humidifying the gas, or it can cause the machine or gas to overheat. These devices can be designed to monitor the presence of water in the system. Running out of water can be dangerous for the patient or damage the device. Typically, a sensor that detects the position of a float provides this detection. Sensor systems often only detect when the water runs out, at which point the operator must immediately replenish the water supply to continue therapy. In some devices, water from the water reservoir may enter the main unit, particularly if the device is in standby mode for extended periods while connected to a water source. In some cases, the user must manually turn off the water source to prevent this from happening. Failure to do so can allow water to flood the humidification chamber and push water into the air path. Requiring the user to monitor and control the water in the system leads to an increased risk of damage or misuse. Conventional systems detect the presence of an auxiliary unit in the main unit using sensors. Position switches and optical sensors are frequently used. In some cases, these may be adequate, but they provide only limited information about the installed auxiliary unit. Some devices may have different versions of an auxiliary unit that require the main unit to know which auxiliary unit is installed so that the correct settings or functions can be enabled. Conventional systems rely on user input to ensure the correct settings are implemented, but users can make mistakes or become confused. In some devices, the auxiliary unit must be fully seated to ensure correct function, but conventional systems have no way to detect if the device is slightly out of position. Most conventional humidifiers do not measure the humidity of the respirable gas supplied to the patient. Measuring humidity in near-saturated conditions is known to be very difficult and requires special sensors. Capacitive humidity sensors operate on the principle of hygroscopic materials absorbing moisture from the air and are sometimes used in conventional systems. However, these sensors can fail if they come into contact with liquid water, which is common in humidifier flow paths. Chilled mirror systems, used in other humidifiers or conventional laboratory testing, can be bulky and not cost-effective. They are also prone to false readings in the presence of liquid water. The use of a ventilator as a gas source for HFT has limitations, as suggested above, notably the limited capacity to generate pressure, so its use to deliver breathing gas is limited by the flow resistance of the system. In particular, ventilators have been considered unsuitable for use with high velocity nasal insufflation (HVNI) systems, which use small-bore restrictive cannulae to create high-velocity gas flow and therefore have high pressure requirements. Accordingly, HFT systems based on familiar low-speed ventilators are particularly unsuitable for use in treating severe conditions. Many systems use a large-diameter delivery tube with a heated wire to reduce precipitation, typically at least 15 or 22 mm in diameter.The flow rate in these systems is very low, so the pressure drop is minimal, making it more suitable for use with a ventilator. The low flow rate in the supply tube can allow condensation to accumulate in the supply tube. This could be transmitted to the patient if the supply tube is moved to allow water to flow downhill. Brief description of the invention To address the foregoing and other problems, systems and methods for high-velocity respiratory therapy are provided herein. The system includes a ventilator, a conduit, and an open nasal cannula. The ventilator delivers respirable gas to the conduit, which transmits a flow of respirable gas to the nasal cannula at a high flow rate and high velocity. The nasal cannula has at least one nasal prong which delivers the respirable gas to a patient's nose. The system is configured such that respirable gas exits the at least one nasal prong at a velocity of at least about 40 m / s and less than about 75 m / s, and in particular at least 50 m / s, at least 55 m / s, or at least 60 m / s. The system also provides breathing gas at a high flow rate, for example, at least 5 L / min, at least 10 L / min, at least 20 L / min, at least 30 L / min, at least 40 L / min, at least 50 L / min, or at least 60 L / min.High-flow, high-velocity respiratory therapy using the systems and methods provided herein offers many advantages. First, heated and humidified gas can be delivered to a patient, allowing for clearance of secretions and decreased development of bronchial hyperresponsiveness symptoms and minimizing the impact of dry air on lung tissue. Another advantage is that high-flow respiratory therapy systems and methods can better meet high peak inspiratory flow demands compared to conventional systems. These high-flow systems and methods can increase the functional residual capacity of a patient's lungs via the delivery of positive end-expiratory pressure. High-flow therapy via open nasal cannula provides greater comfort and is more tolerable for a patient relative to conventional systems.Oxygen dilution of the patient's upper airway can be minimized, and carbon dioxide can be removed by meeting the flow and dead space washout demands of the respiratory tract. The systems and methods herein can be configured to treat severe respiratory diseases and conditions, such as COPD and ARDS. Another advantage provided herein is the portability of these systems, which provides the option of completely eliminating the need for external sources of power and materials, providing a device at home or on the go for continuity of care. The systems can therefore be used to provide home or longer-term care for patients, particularly patients with moderate to severe respiratory conditions. The systems and methods presented herein may be configured with a system architecture that allows the system to be operated by a lower pressure source (e.g., <270 hPa, <200 hPa, <150 hPa, <100 hPa, <50 hPa, <30 hPa, <20 hPa, <10 hPa, or any suitable gauge pressure). By using a ventilator or similar low pressure source, the system optionally does not require an external source of high pressure gas. Instead, the system may accept gas (ambient air or gas from another source) at ambient pressure and then pressurize the gas (e.g., internally). This allows the system to operate in environments where pressurized gas sources are unavailable (e.g., at home, in an ambulance, and / or an outpatient care facility). In some implementations, the ventilator is a centrifugal fan.In some implementations, the nasal cannula includes one or two nasal prongs with distal openings positionable within the patient's nostrils for delivering high-velocity respirable gas. A non-sealing cannula may be used, and in particular, the cannula may be open to the atmosphere at the nasal prong outlet. In some implementations, the gas provided at the prong outlet has a non-zero dynamic pressure. In some implementations, the respirable gas is humidified within the system. The gas flow path may have a connector between the nasal cannula, the delivery tube, and the prong outlet, which may be opened or closed to allow or close the flow of respirable gas to the prong outlet. In some implementations, the system is configured with a target flow set point for the flow rate of the respirable gas. The target flow set point can be configured and coordinated with the inner diameter of the cannula nasal tip in order to deliver high velocity respirable gas via the ventilator. In some implementations, the respirable gas output velocity from the nasal tip is a function of the inner diameter of the at least one nasal tip and the target flow set point. In order to achieve the desired high output velocity, the combination of nasal tip inner diameter and target flow set point are selected so as to convert the output energy of the respirable gas from the ventilator (after heating and humidification, as disclosed herein) to high velocity respirable gas exiting the nasal tip.For example, to achieve high velocity breathing gas, the nasal cannula may be configured with a nasal tip having an inside diameter greater than or equal to about 1.4 mm and less than about 1.8 mm, and the ventilator set with a peak flow set point greater than or equal to about 9 L / min and less than or equal to about 28 L / min. In another example, the nasal tip inside diameter may be greater than or equal to about 1.8 mm and less than about 1.9 mm, and the peak flow set point is greater than or equal to about 13 L / min and less than about 31 L / min, thereby achieving the high velocity breathing gas. For another example of generating high velocity breathing gas, the nasal tip inside diameter may be greater than or equal to about 1.9 mm and less than about 3 mm, and the peak flow set point is greater than or equal to about 21 L / min and less than about 60 L / min. For another example, the nasal tip inner diameter may be greater than or equal to about 3 mm and less than about 4 mm, and the peak flow set point is greater than or equal to about 34 L / min and less than about 80 L / min. In some implementations, the exit velocity is at least about 40 m / s and less than about 70 m / s, at least about 40 m / s and less than about 65 m / s, at least about 40 m / s and less than about 60 m / s, at least about 40 m / s and less than about 55 m / s, at least about 40 m / s and less than about 50 m / s, at least about 40 m / s and less than about 45 m / s, or about 40 m / s. In some implementations, the exit velocity is at least 50 m / s, at least 55 m / s, at least 60 m / s, at least 65 m / s, or at least 70 m / s. In some implementations, the exit velocity is greater than a velocity measured at any point along a flow path between the ventilator and the nasal cannula extension. As used throughout this disclosure, any of the speeds referred to above are considered “high speed.” In some implementations, the cannula used with the system is configured with a diameter (or diameter-to-length ratio) that allows the cannula to provide a pressure drop necessary for the system to operate at specified high flow rates with high velocity. For example, if a cannula with a nasal tip having an inside diameter greater than or equal to about 1.1 mm and less than about 1.6 mm is used, the pressure drop of the cannula is less than 80 hPa when opened to a flow set point of 8 L / min, while still providing the respirable gas at a high velocity. As another example, if a cannula with a nasal tip having an inside diameter greater than or equal to about 1.5 mm and less than about 2 mm is used, the pressure drop of the cannula is less than 100 hPa when operating at a flow set point of 20 L / min and a high velocity.As another example, if a cannula is used with a nasal tip that has an inside diameter greater than or equal to about 1.9 mm and less than about 3.5 mm, the cannula pressure drop is less than 80 hPa when operating at a flow set point of 40 L / min and a high velocity. According to one aspect, the system comprises a ventilator, a conduit, a nasal cannula configured to deliver HFT respirable gas at a high velocity and having at least one nasal prong, a controller, and a processor. The ventilator is configured to deliver respirable gas to the conduit, which transmits respirable gas to the nasal cannula. From the nasal cannula, the nasal prong delivers respirable gas to a nostril of a patient. The system is configured such that respirable gas exits the nasal prong at a high velocity, e.g., at least about 40 m / s and less than about 75 m / s, or in particular at least 50 m / s.The processor is configured to receive first data indicative of one or more dimensions of the nasal cannula, receive second data indicative of a flow rate of the respirable gas, and calculate an output velocity based on the first data and the second data, which may be further adjusted (e.g., by adjusting the flow rate relative to the cannula size) to achieve relevant therapy goals. In some implementations, the system further comprises a display, and the processor is further configured to generate for display at least one of: the breathing gas flow rate, the output velocity, a target flow setpoint, and a system pressure drop. In some cases, both the output velocity and the flow rate are displayed to the user (e.g., a physician or patient at home). The user may view the display and decide to change one or more parameters. For example, the user may desire to change the output velocity. In some implementations, the system receives user input indicating a change to at least one of the breathing gas flow rate and the output velocity. For example, a user input may indicate a modified flow rate, at which the user may desire to operate the system.For example, a user input may indicate a modified rate at which the user may desire to operate the system. In some implementations, after receiving a user input, the controller is configured to change the flow rate to account for the user input indicating a change in the flow rate or output velocity. This step may require calculating a modified flow rate if the user input is a desired rate, such that the modified flow rate corresponds to the desired rate. In some implementations, the processor calculates a modified rate based on the user input and the first data. For example, the user input may be a desired flow rate, and the processor calculates the modified rate based on the dimensions of the nasal tip (whether single or double pronged) and the desired flow rate. In some implementations, the ventilator, controller, and processor are housed in a base unit. The system may comprise an auxiliary unit configured to be reversibly connected to the base unit. In some implementations, the conduit is configured to be reversibly connected to the auxiliary unit, such that the conduit is in fluid communication with the auxiliary unit, which is in fluid communication with the ventilator when the auxiliary unit is connected to the base unit. The ventilator may provide the flow of respirable gas to the auxiliary unit while connected to the base unit, and the conduit may receive respirable gas from the auxiliary unit. The nasal cannula may be reversibly connected to the conduit to receive the respirable gas. According to another aspect, a method for providing high velocity respiratory therapy uses the system of the first aspect for treating a patient having a respiratory condition. The method includes sending a flow of respirable gas from a ventilator through a conduit and into a nasal cannula, and providing the respirable gas to a nose of the patient from the nasal prong of the nasal cannula. The ventilator may be a low pressure ventilator configured to send respirable gas at an outlet pressure of less than 30 kPa (or less than 25 kPa, less than 20 kPa, less than 15 kPa, or less than 10 kPa). The nasal cannula is in fluid communication with the conduit and is configured to receive the respirable gas from the conduit.The nasal cannula has a nasal tip configured with a cross-sectional diameter sized to provide respirable gas from its distal end at an exit velocity of at least about 40 m / s and less than about 75 m / s, or in particular at least 50 m / s. The patient may be suffering from a mild, moderate, or severe shortness of breath condition. The patient may have COPD or ARDS. In some implementations, the method provides therapy for a patient having COPD or ARDS by generating NIH using a ventilator, in a mobile respiratory care system that is adapted to take in ambient air, pressurize it to a high pressure, and deliver it through an open nasal cannula at a high velocity. In some implementations, the method further comprises receiving first data indicative of one or more dimensions of the nasal cannula, receiving second data indicative of a respirable gas flow rate, and calculating the exit velocity based on the first data and the second data. In some implementations, the method further comprises generating for display at least one parameter selected from the group of: the flow rate, the exit velocity, a target flow set point, and a pressure drop. In some implementations, both the flow rate and the exit velocity are displayed.The method may further involve receiving a user input to increase or decrease the flow rate of the breathing gas, changing the flow rate to a modified flow rate of the breathing gas, calculating a modified velocity based on the modified flow rate and the first data, and generating for display at least one selected from the group of: the modified flow rate and the modified velocity. In another aspect, a system is provided for providing respiratory therapy to a patient, the system comprising a base unit comprising: a ventilator configured to deliver respirable gas at a high velocity and a controller; an auxiliary unit configured to be reversibly coupled to the base unit, wherein the auxiliary unit comprises an auxiliary unit outlet; and an inlet tube configured to receive the respirable gas from the auxiliary unit outlet and transmit the respirable gas to the patient. The base unit may further comprise a measuring device comprising a first flow sensor, a second flow sensor, and a device conduit in fluid communication with the ventilator, wherein the first flow sensor and second flow sensor are positioned in series along the conduit.The controller may be configured to adjust a respirable gas flow rate of the ventilator based on at least one of the first measurement or the second measurement. The system may comprise a supplemental gas inlet configured to receive a supplemental gas from an external gas source and add the supplemental gas to the respirable gas, wherein the supplemental gas inlet is in fluid communication with the device conduit and disposed between the first flow sensor and the second flow sensor. At least one advantage is that the dual-sensor adjustment allows for the detection of very small changes in the flow rate, such that the amount of supplemental gas added may be finely tuned. The base unit may comprise a seat configured to receive the auxiliary unit when the auxiliary unit is coupled to the base unit. The base unit may comprise at least one alignment sensor (e.g., a radio frequency identification (RFID) reader or a Hall effect sensor), and the auxiliary unit comprises at least one alignment marker (e.g., an RFID or other tag, or a magnet). The system may include an occlusion valve operatively configured to simultaneously control the breathing gas output and liquid flow into the auxiliary unit, e.g., using three valve positions. The auxiliary unit may comprise a liquid container and a vapor transfer cartridge (VTC) configured to humidify the breathing gas.The base unit may comprise a level sensor configured to output at least one liquid level measurement indicating a liquid level in the liquid container. The auxiliary unit may include a pump configured to pump the liquid into the auxiliary unit, the pump being magnetically coupled to the base unit. The auxiliary unit may comprise a heating plate in a heating section, and the base unit may comprise a heat actuator configured to couple to the heating plate in a non-contact manner. One or more temperature sensors may be provided on the base unit to monitor the liquid temperature or heat plate temperature. These various sensors and components allow for contactless coupling between the auxiliary unit and the base unit.These contactless couplings can minimize fluid contamination of the base unit or cross-contamination between the base unit and the auxiliary unit. In some implementations, the delivery tube includes a jacket for insulating or heating the breathing gas carried within the delivery tube. The jacket may also be constructed to prevent the delivery tube from kinking. In some implementations, the base unit may comprise a removable battery and a backup battery and may be configured to operate in a standby or low power mode when the removable battery is removed. One or more external devices may be coupled to the base unit; for example, a pulse oximeter or transcutaneous carbon dioxide sensor may be coupled to provide real-time oxygen or carbon dioxide measurements of a patient. Methods for closed-loop monitoring of the patient's oxygen or carbon dioxide may be implemented in the system. In another aspect, provided herein is a method for measuring respirable gas flow in a respiratory therapy system, the method comprising generating a first measurement of the respirable gas flow using a first flow sensor, generating a second measurement of the respirable gas flow using a second flow sensor, and adjusting one or more parameters of the respiratory therapy device based on at least one of the flow measurement and the second measurement. The method may further involve mixing the respirable gas flow with supplemental gas flow to form a mixed flow after taking the first measurement. The method may further comprise pausing the flow of the supplemental gas; and calibrating the first flow sensor and the second flow sensor to each other while the supplemental gas flow is paused, wherein calibrating reduces an error of the calculated flow difference to an error of the second flow sensor.The method may further involve receiving SpO-2 data from a pulse oximeter; from the SpO-2 data, determining PaO-2 data; calculating an appropriate oxygen concentration of the breathing gas; performing adaptive feedback control of the breathing gas based on the SpO-2 level signals, wherein the adaptive feedback control is provided by a proportional integral derivative (PID) controller; receiving a signal indicating that the breathing gas supplied by the measuring device has been manually changed; and upon receiving the signal, entering a manual override mode and stopping the adaptive feedback control. In another aspect, a method is provided for controlling operation of a respiratory therapy unit, the method comprising receiving a first signal from an alignment sensor in a base unit of the respiratory therapy unit, the first signal being indicative of an alignment of the alignment sensor with an alignment marker of an auxiliary unit of the respiratory therapy unit; initiating operation of the respiratory therapy unit; receiving a second signal from the alignment sensor, the second signal being indicative of misalignment of the alignment sensor with the alignment marker; and stopping operation of the respiratory therapy unit. In another aspect, a method is provided for controlling operation of a respiratory therapy unit, the method comprising receiving a temperature measurement from a temperature sensor in a heating section of the respiratory therapy unit; comparing the temperature measurement to a reference temperature; and if the temperature measurement is greater than the reference temperature, stopping operation of the respiratory therapy unit. In another aspect, a method is provided for controlling power in a respiratory therapy unit, the method comprising receiving a first signal indicating that a removable battery has been removed from the respiratory therapy unit; changing operation of the respiratory therapy unit from a regular power mode to a low power mode; and operating the respiratory therapy unit using a backup battery in the respiratory therapy unit. In another aspect, a method is provided for operating a respiratory therapy unit, the method comprising receiving a liquid level measurement from a level sensor, the liquid level measurement indicating a liquid level in a liquid container of the respiratory therapy unit; receiving a flow measurement from a flow sensor, the flow measurement indicating a flow rate of respirable gas in the respiratory therapy unit; and calculating humidity of the respirable gas based on the liquid level measurement and the flow measurement. Multiple flow rate and liquid level measurements may be used in the methods. In another aspect, a measuring device is provided for a respiratory therapy unit, the measuring device comprising a first flow sensor, a second flow sensor, and a conduit in fluid communication with the respiratory therapy unit, wherein the first flow sensor and second flow sensor are positioned in series along the conduit. The measuring device may further comprise a supplemental gas inlet configured to receive a supplemental gas from an external gas source and add the supplemental gas to the respirable gas, wherein the supplemental gas inlet is disposed between the first flow sensor and the second flow sensor. In another aspect, a respiratory therapy system is provided comprising a base unit configured to output respirable gas; and an auxiliary unit configured to receive the output respirable gas, the auxiliary unit comprising a liquid container; and a vapor transfer cartridge (VTC), configured to humidify the respirable gas; wherein the liquid container comprises an outlet conduit in fluid communication with a cartridge inlet of the VTC. The base unit may comprise a level sensor configured to output a liquid level measurement indicative of a liquid level in the liquid container. In some implementations, the system comprises a port configured to connect to a nebulizer from which aerosolized medicament is introduced and entrapped in the respirable gas.For example, the port is located along a system supply tube, on a nasal cannula or patient connector at the end of the supply tube, or at the inlet or outlet of the VTC. In some aspects, provided herein is a method of treating a respiratory disease or a viral disease. For example, the systems and methods described herein are used to treat coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These systems configured with a high-flow nasal cannula can be used for mechanical ventilation of patients with respiratory failure (e.g., related to COVID-19). Treatment of COVID-19 may involve introducing supplemental oxygen into the breathing gas via a supplemental gas inlet. A pulse oximeter may be connected to the patient during treatment such that SpO2 is monitored and the supplemental oxygen flow rate can be adjusted to provide sufficient oxygen to achieve a therapeutic oxygen level in the patient. In some aspects, a mobile respiratory therapy system is provided herein. For example, a respiratory therapy system is placed on a rolling cart, in a vehicle, or in a patient's home. The system may be configured to ingest ambient air and pressurize it via the ventilator, in addition to or instead of an external source of pressurized gas. The system may include one or more sensors in the air inlet to measure the temperature or humidity of the incoming air. The system may also be configured to operate on internal battery power, without an external power source. In another aspect, provided herein is a system for delivering high-velocity respiratory therapy to a patient's nose. As mentioned above, known low-velocity ventilator-based HFT systems are particularly unsuitable for use in treating severe conditions. Because of this, all components of the air path must have a minimal pressure drop so that the maximum amount of blower pressure possible is reserved to accelerate flow through the cannula tips. The system described here optimizes pressure drop along the air path to maintain sufficient pressure for high-velocity output.The system comprises a respirable gas source configured to deliver a flow of respirable gas at a flow rate of 8-60 L / min (or greater than 60 L / min) and an outlet pressure; a gas passageway in fluid communication with the respirable gas source and configured to convey the flow of respirable gas from the respirable gas source; and a nasal cannula in fluid communication with the gas passageway and having a nasal tip with an outlet orifice having a tip cross-sectional area, the nasal cannula defining a first flow path length and configured to receive the flow of respirable gas from the gas passageway and transmit the flow of respirable gas through the outlet orifice at a high velocity.The gas passageway defines a second flow path length between the source of respirable gas and the nasal cannula, the gas passageway having a minimum passage cross-sectional area at a point along the second flow path length such that a ratio of the minimum passage cross-sectional area to the tip cross-sectional area is about 2.5 to 5. As respirable gas flows through the nasal cannula, a pressure drop occurs in an amount corresponding to less than about 35% of the outlet pressure. The nasal tip outlet orifice is configured with an internal diameter sized such that respirable gas exiting the outlet orifice has an exit velocity of at least 40 m / s, or in particular at least 50 m / s. In some implementations, the source of breathing gas is any of a ventilator, a compressor, a portable gas tank, or a wall outlet. In some implementations, the system further comprises a humidifier positioned along the gas passage and configured to humidify the breathing gas flow. The humidifier may be a vapor transfer unit comprising a plurality of permeable fibers, a liquid inlet, and a liquid outlet, wherein the liquid inlet is configured to convey a heated liquid into the vapor transfer unit such that the heated liquid flows around the plurality of permeable fibers. Alternatively, the humidifier may be a hot pot humidifier comprising a heating plate and a fluid reservoir, wherein the heating plate heats a liquid in the fluid reservoir. In some implementations, the tip cross-sectional area is substantially circular. In some implementations, the tip cross-sectional area has an oval shape. In some implementations, the tip cross-sectional area has an inner diameter of 1.2 to 3.8 mm. In some implementations, the exit pressure is approximately 14 kPa. In some implementations, the pressure drop of the respirable gas through the nasal cannula is 1 to 4.5 kPa. In some implementations, the exit velocity is 40 to 80 m / s. In some implementations, the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 2.5, and the flow rate is 40-60 L / min. In some implementations, the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 3, and the flow rate is approximately 20 L / min.In some HFT adaptations, the exit velocity is high velocity and the pressure drop across the nasal cannula is 1 to 4.5 kPa. In some implementations, the system further comprises an oxygen source configured to provide a flow of oxygen, such that the respirable gas flow comprises the oxygen flow. In some implementations, the gas passage comprises a supply tube having an inlet port coupled to the respirable gas source, an outlet port coupled to the nasal cannula, and a lumen configured to convey the respirable gas from the inlet port to the outlet port. In some implementations, the nasal cannula comprises a facial tubing section. In some implementations, the respirable gas source is a centrifugal fan. In another aspect, provided herein is a method for providing high velocity respiratory therapy to the nose of a patient, e.g., a patient suffering from moderate to severe respiratory disease, such as COPD or ARDS. The method comprises the steps of: sending a high velocity flow of respirable gas from a respirable gas source at a flow rate of 8-60 L / min and a first outlet pressure; conveying the respirable gas flow from the respirable gas source along a gas passageway to a nasal cannula; and delivering the respirable gas flow to the nose of a patient through an outlet port at an exit velocity of at least 40 m / s, or in particular at least 50 m / s. The gas passageway defines a first flow path length between the respirable gas source and the nasal cannula.The nasal cannula has a nasal tip with the outlet orifice having a tip cross-sectional area, the nasal cannula defining a second flow path length. The gas passageway has a minimum passage cross-sectional area along the first flow path length such that the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is 2.5 to 5. As respirable gas flows through the nasal cannula, a pressure drop occurs in an amount corresponding to less than about 35% of the first outlet pressure. In some implementations, the source of breathing gas is any of a fan, a compressor, a portable gas tank, or a wall outlet. In some implementations, the method further comprises: humidifying the breathing gas flow with a humidifier positioned along the gas passageway. In some implementations, the humidifier may be a vapor transfer unit comprising a plurality of permeable fibers, a liquid inlet, and a liquid outlet, wherein the liquid inlet is configured to convey a heated liquid into the vapor transfer unit such that the heated liquid flows around the plurality of permeable fibers. In other implementations, the humidifier may be a hot pot humidifier comprising a heating plate and a fluid reservoir, wherein the heating plate heats a liquid in the fluid reservoir. In some implementations, the tip cross-sectional area is substantially circular. In some implementations, the tip cross-sectional area has an oval shape. In some implementations, the tip cross-sectional area has an inner diameter of 1.2 to 3.8 mm. In some implementations, the exit pressure is approximately 14 kPa. In some implementations, the pressure drop of the respirable gas through the nasal cannula is 1 to 4.5 kPa. In some implementations, the exit velocity is 40 to 80 m / s. In some implementations, the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 2.5, and the flow rate is 40-60 L / min. In some implementations, the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 3, and the flow rate is approximately 20 L / min.In some implementations, the respirable gas is delivered at a second outlet pressure equal to the first outlet pressure less a cumulative pressure drop comprising the pressure drop that occurs across the nasal cannula. In some implementations, the method further comprises mixing the respirable gas flow with a supplemental oxygen flow provided by an oxygen source configured to provide an oxygen flow. In some implementations, the first gas passage comprises a supply tube having an outlet port coupled to the respirable gas source, an outlet port coupled to the nasal cannula, and a lumen configured to convey the respirable gas from the inlet port to the outlet port. In some implementations, the nasal cannula comprises a facial tubing section. In some implementations, the respirable gas source is a centrifugal fan. In another aspect, provided herein is a method for providing high velocity respiratory therapy to the nose of a patient. The method comprises the steps of: sending a flow of respirable gas from a respirable gas source at a flow rate of 8-60 L / min and a first outlet pressure; conveying the flow of respirable gas from the respirable gas source along a gas passageway to a nasal cannula; and delivering the flow of respirable gas to the nose of a patient through an outlet port of a nasal prong at a high velocity, such as an outlet velocity of at least 40 m / s, or in particular at least 50 m / s. As the respirable gas flows through the nasal cannula, a pressure drop occurs in an amount corresponding to less than about 35% of the first outlet pressure. In some implementations, the gas passageway defines a first flow path length between the respirable gas source and the nasal cannula.In some implementations, the exit orifice of the nasal tip of the nasal cannula has a tip cross-sectional area, the nasal cannula defining a second flow path length. In some implementations, the gas passageway has a minimum passage cross-sectional area along the first flow path length such that the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is 2.5 to 5. The nasal tip used with the cannula may be a single tip or a dual tip. Those skilled in the art will devise variations and modifications after reviewing this disclosure. The disclosed features may be implemented in any combination and subcombination (including multiple dependent combinations and subcombinations) with one or more features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated into other systems. In addition, certain features may be omitted or not implemented. Incorporation as a reference All publications, patents, and patent applications mentioned in this specification are incorporated herein by reference to the same extent as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference. To the extent that publications, patents, or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and / or prevail over any such conflicting material. Brief description of the drawings The foregoing and other objects and advantages will become apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: Figure 1 shows a block diagram of a high-speed respiratory therapy system, according to an illustrative implementation. Figure 2 shows a block diagram of a control system for a high-speed respiratory therapy system, according to an illustrative implementation. Figure 3 shows a flow diagram describing a method for calculating and displaying the output velocity of a respiratory therapy system, according to an illustrative implementation; Figure 4 shows a respiratory therapy system including a base unit and an auxiliary unit, according to an illustrative implementation; Figure 5 shows a cross-section of a respiratory therapy system including an auxiliary unit seated on a base unit, according to an illustrative implementation; Figure 6 shows a cross-section of an occlusion valve for linking a base unit and an auxiliary unit, according to an illustrative implementation; Figures 7A to 7F show various views and cross-sections of an auxiliary unit, in accordance with an illustrative implementation; Figures 8A and 8B show cross-sections of an occlusion valve for linking a base unit and an auxiliary unit, according to an illustrative implementation; Figure 9 shows a heating section of an auxiliary unit of a respiratory therapy system, according to an illustrative implementation; Figure 10 shows a measuring device, according to an illustrative implementation; Figure 11 shows a metering device configured to receive a supplemental gas, in accordance with an illustrative implementation; Figure 12 shows a measurement device configured to receive a supplemental gas and coupled to a PID controller, in accordance with an illustrative implementation; Figures 13A and 13B show graphical representations of carbon dioxide in the patient's airway during high flow therapy, in accordance with an illustrative implementation; Figures 14A to 14C show graphs of a computational fluid dynamics (CFD) study performed for high velocity therapy, in accordance with an illustrative implementation; Figure 14A shows a graph of cannula pressure drop as a function of output velocity; Figure 14B shows a graph of cannula pressure drop as a percentage of total available pressure from a 14 kPa ventilator as a function of output velocity; Figure 14C shows a graph of tubing pressure drop as a function of the ratio of tubing cross section to cannula tip size; Figure 15 shows a graph of heater power as a function of gas flow rates for humidification, according to an illustrative implementation; and Figure 16 shows a flow diagram describing a method for measuring humidity in respirable gas delivered by a respiratory therapy system, according to an illustrative implementation. Detailed description of the invention To provide a general understanding of the assemblies and methods described herein, certain illustrative implementations will be described. Although the implementations and features described herein are specifically described for high-velocity respiratory therapy, it will be understood that all of the components and other features described below may be combined together in any suitable manner and may be adapted and applied to other respiratory therapy systems and devices, including low-flow oxygen therapy, continuous positive airway pressure (CPAP) therapy, mechanical ventilation, oxygen masks, Venturi masks, and tracheostomy masks. The term "approximately," as used herein, should be understood to mean plus or minus 20%. For example, "approximately 40 m / s" should be understood to mean 40 m / s ± 8 m / s. The systems, devices, and methods described herein can be used to deliver high flow therapy (HFT) at a high rate, for example, for the treatment of patients suffering from moderate to severe respiratory conditions, such as COPD and ARDS. HFT systems / devices deliver respirable gas at a high flow rate via an interface such as an open nasal cannula to increase the patient's fraction of inspired oxygen (FiO2), decrease the patient's work of breathing, or both. HFT can create a reservoir of high FiO2 in the nasal cavity, nasopharynx, or oropharynx. Increasing FiO2 or decreasing the work of breathing aids in the patient's recovery from respiratory ailments, such as shortness of breath or bronchospasm.Some HFT devices warm and humidify the delivered breathing gas for medical reasons (e.g., to maintain tissue flexibility in surfactant-deficient patients, or to preserve mucosal integrity) or to reduce patient discomfort (e.g., warmed and humidified nasal oxygen may be better tolerated). HFT can be used to eliminate anatomical dead space, for example, in a patient's upper airway to reduce hypercapnia and hypoxemia. The high-velocity gas maintains a constant flow of fresh gas in the patient's airway, thereby flushing the upper airway dead space. Patients experience assisted exhalation due to the flushing of exhaled air by the constant flow of fresh gas, allowing a reservoir of fresh air to be easily inhaled.This upper airway wash creates a reservoir that reduces ambient air entrainment to provide a more realistic F¡O-2 as set by the system / device, providing more effective oxygenation. Additionally, flow humidification reduces the negative effects of dry air on lung tissue by overcoming the ventilation effects of HFT. As used herein, the term “processor” or “computing device” refers to one or more computers, microprocessors, logic devices, servers, or other devices configured with hardware, firmware, and software to perform one or more of the computing techniques described herein. Processors and processing devices may also include one or more memory devices for storing inputs, outputs, and data currently being processed. As used herein, “user interface” includes, without limitation, any suitable combination of one or more input devices (e.g., keyboards, touchscreens, trackballs, voice recognition systems, etc.) and / or one or more output devices (e.g., visual displays, speakers, touchscreens, printing devices, etc.).Examples of user devices that may implement an interface include, but are not limited to, personal computers, laptops, and mobile devices (such as smartphones, Blackberries, PDAs, tablets, etc.). For example, an interface may be implemented on a web browser or a mobile application installed on the user device. As used herein, the term “liquid” generally refers to water; however, “liquid” may also include liquid drugs and mixtures of water and liquid drugs. As used herein, the term “respirable gas” generally refers to air; however, “respirable gas” may be used to refer to a gas that has oxygen and / or carbon dioxide in proportions different from ambient air. “Respirable gas” may be used to refer to air, oxygen, carbon dioxide, helium, nitric oxide, gases containing vaporized water, gases containing an aerosol, and anesthetic gases, or a mixture of any or all of the foregoing, if configured for inhalation by a patient. “Respirable gas” may be used to refer to gas mixtures, such as mixtures of any of oxygen, carbon dioxide, nitrogen, helium, nitric oxide, gases containing vaporized water, gases containing an aerosol, and anesthetic gases.A “fan” is described as a component of many of the systems described herein; the term “fan” should be understood to encompass centrifugal fans, regenerative fans, side channel fans, vortex fans, positive displacement fans, and any other suitable fans. It should also be understood that in some implementations, a compressor may be used in place of a fan, for example, a centrifugal compressor, a side channel compressor, a ring compressor, or a positive displacement compressor. Parameters for high velocity respiratory therapy Various combinations of system parameters suitable for providing high-velocity respiratory therapy are discussed herein. As discussed above, the system is configured with a respirable gas flow rate controlled by a target flow setpoint, and the cannula is configured to receive the respirable gas flow at the setpoint and output the respirable gas flow to the patient through at least one nasal prong. The nasal prong has an inner diameter suitable for constricting the received flow of respirable gas such that it exits the outlet prong at a high velocity. In some implementations, the respirable gas output velocity from the nasal prong is a function of the inner diameter of the at least one nasal prong and the target flow setpoint.To achieve the desired output velocity, certain combinations of nasal prong inner diameter and target flow setpoint may be desirable and / or permissible. Table 1 shows exemplary combinations of nasal prong inner diameter and peak flow setpoint that achieve high-velocity respiratory therapy. Table 1: Exemplary combinations of nasal tip inner diameter and peak flow set point configured to provide high velocity respiratory therapy in systems of the present disclosure. Nasal tip inner diameter d (mm) Maximum flow set point Q (L / min) 1.4 < d < 1.8 9 < Q < 20 1.8 < d < 1.9 13 <Q<31 1.9 < d < 3 21 < Q < 60 3<d<4 34 < Q < 80 In some implementations, cannula sizes may be used in the high-velocity respiratory therapy systems discussed herein to achieve a desired pressure drop or other system conditions or cannula properties. For example, there may be allowable cannula pressure drops for a given nasal tip inner diameter and flow setpoint. Table 2 shows exemplary ranges of cannula pressure drops for certain pressure drops and flow setpoints. Table 2: Exemplary nasal cannula pressure drops that may allow high velocity respiratory therapy with the described system based on nasal prong inner diameter and flow set points. Nasal tip inner diameter d (mm) Cannula pressure drop (hPa) Flow set point (L / min) 1.1 < d < 1.6 80 8 1.5 <d <2 100 20 1.9<d<3.5 80 40 The parameters discussed above may be implemented in a respiratory therapy system, such as that shown in Figure 1. Figure 1 is a block diagram describing a system 100 for providing high velocity respiratory therapy, according to one illustrative implementation. The system 100 includes ventilator 102, conduit (also referred to as delivery tube herein) 106, and nasal cannula 108 having at least one nasal prong 110. The ventilator 102, delivery tube 106, cannula 108, and prong 110 are sequentially positioned in fluid communication. Accordingly, respirable gas 104 is expelled from the ventilator 102, flows through the delivery tube 106 to the cannula 108, and exits the cannula 108 through the prong 110 at the root 112 of a patient. In certain implementations, the ventilator 102 is housed within a base unit, which may further include a computing device, such as a computing device 200 of Figure 2. This computing device may include a processor and / or a controller, for example, CPU 206 and input / output controller 210 of Figure 2. In some implementations, the supply tube 106 is not directly attached to the ventilator 102; instead, the system 100 further comprises an auxiliary unit configured to reversibly connect the supply tube 106 to the ventilator 102 or the base unit. The supply tube 106 may be reversibly connected at one end to the auxiliary unit, and the cannula 108 may be reversibly connected to an opposite end of the supply tube 106. The supply tube 106 may be any suitable conduit for transmitting air fluid or respirable gas. In some implementations, the system 100 receives the information or data about the cannula 108. The information or data may be received when the cannula 108 is attached to the delivery tube 106 or when the auxiliary unit is connected to the ventilator 102 or the base unit. For example, the system 100 receives data indicative of tip dimensions 110 of the cannula 108. The cannula data may be stored on a chip located on the cannula 108 or the auxiliary unit. In some implementations, the system 100 comprises a transmitter configured to send the data to a receiver or the controller. The transmitter may be an RFID tag or other label within the auxiliary unit or attached to the cannula 108. The label may include information relating to the auxiliary unit, the nasal cannula, the at least one nasal prong, or any other relevant information. The base unit may include a receiver configured to receive the information from the label. In some implementations, the user provides the data. For example, the user may directly enter the data, upload the data from a separate device, or select an installed cannula from a list (e.g., a drop-down menu on a screen), where the selected cannula is associated with certain data in the system. In some implementations, the cannula data may include additional information and may be used to identify the nasal cannula as originating from a specific manufacturer, having certain characteristics, and / or having a history of use. Knowing the cannula dimensions, such as an inner diameter of tip 110, may be useful in calculating the exit velocity of respirable gas 104 from tip 110 into nose 112. Nasal cannula designs consistent with the present disclosure are described in U.S. Pat. No. 10,300,236 , the contents of which are incorporated herein by reference in their entirety. For example, the exit velocity may be determined by the processor based on the tip bore and a measured flow rate of respirable gas 104. The respirable gas flow rate may be measured by one or more sensors in the system. The one or more sensors may be located within the ventilator 102, at an outlet of the ventilator 102, at an inlet or outlet of the delivery tube 106, within the delivery tube 106, within the cannula 108, or at any other suitable location. The one or more sensors may send one or more measurements to the controller or processor. The data or measurements may be stored in a memory, such as memories 202 and 204 in FIG. 2, or in a database, such as database 216 in FIG. In some implementations, the system 100 includes a display, which may be operated by the processor to, for example, display various system parameters or allow user input. For example, the display may display any of the breathing gas flow rate, output velocity (e.g., the rate calculated by the processor), breathing gas humidity, oxygen concentration, target flow set point, pressure drop, temperature, therapy duration, FiOs, and / or battery level. This information may be useful to the user, such as a physician, who may evaluate the system parameters and make a decision to change one or more of the parameters. In some implementations, a user may input a change to any of the system parameters, for example, through the display such as a touch screen or an interface (e.g., interface 208 of FIG. 2 ).The processor may receive user input, calculate changes to one or more parameters, and direct the controller to change the system operating conditions accordingly. For example, the input may include a change from a first flow rate to a second flow rate, and the processor directs the controller to operate the ventilator 102 at the second flow rate. The processor may then calculate a modified output velocity based on the cannula dimensions and the second flow rate. In some implementations, the user may choose an installed cannula from a drop-down list on the screen as discussed above. By enabling the user to control the flow rate, the system may achieve effective flushing of dead space in the patient's upper airway to provide better oxygen delivery to the patient's lungs and provide an easier breathing experience.This effect is shown and described in relation to Figures 13A and 13B. In some implementations, the respirable gas 104 is humidified in the system 100 before reaching the nose 112. For example, the base unit or auxiliary unit may comprise a vapor transfer cartridge configured to humidify or aerosolize water or medicament or a mixture thereof. The respirable gas 104 may be heated to reach an optimal temperature for humidification. A system that allows for control of a gas mixture with dew point and / or humidification management may be used to treat a wider range of patients. Furthermore, the system may be adapted with various gas mixtures and aerosolized medicaments to provide comfortable treatment of a patient.As an alternative to a vapor transfer cartridge, in some implementations, a hot pot humidification chamber or evaporator is used to humidify the breathing gas, where the breathing gas is caused to flow over a reservoir of heated water that may be refilled continuously or intermittently. The water may be heated using an induction heating plate disposed in the reservoir, the plate generating heat due to a resistance against a current in the plate induced by a magnetic coil in the base unit. Figure 2 is a block diagram of a computing device, such as those described in connection with Figure 1, for performing any of the processes described herein, in accordance with an illustrative implementation. Each of the components of these systems may be implemented in one or more computing devices 200. In certain aspects, a plurality of the components of these systems may be included within a computing device 200. In certain implementations, a component and a storage device may be implemented across multiple computing devices 200. The computing device 200 may be included in a base unit of a respiratory therapy unit, such as base units 402, 502, 602, 802, and 1002 (the computing device being sometimes referred to as a controller herein). The computing device 200 includes at least a communications interface unit, an input / output controller 210, system memory, and one or more data storage devices. The system memory includes at least one random access memory (RAM 202) and at least one read-only memory (ROM 204). All of these elements are in communication with a central processing unit (CPU 206) to facilitate operation of the computing device 200. The computing device 200 may be configured in many different ways. For example, the computing device 200 may be a conventional stand-alone computer, or alternatively, the functions of the computing device 200 may be distributed across multiple computing systems and architectures. In Figure 2, the computing device 200 is linked, via a network or local area network, to other servers or systems. The computing device 200 may be configured in a distributed architecture, wherein databases and processors are housed in separate units or locations. Some units perform primary processing functions and contain at a minimum a general controller or a processor and system memory. In distributed architecture implementations, each of these units may be connected via the combination interface unit 208 to a communications hub or gateway (not shown) that serves as a primary communications link with other servers, client or user computers, and other related devices. The communications hub or gateway may have minimal processing capability on its own, serving primarily as a communications router. A variety of communications protocols may be part of the system, including, but not limited to: Ethernet, SAP, SASTM, ATP, BLUETOOTH™, GSM, and TCP / IP. The CPU 206 includes a processor, such as one or more conventional microprocessors, and one or more supplementary coprocessors, such as math coprocessors, for offloading workload from the CPU 206. The CPU 206 is in communication with the communications interface unit 208 and input / output controller 210, through which the CPU 206 communicates with other devices, such as other servers, user terminals, displays, or devices, such as the components of system 100 of FIG. 1. The communications interface unit 208 and input / output controller 210 may include multiple communication channels for simultaneous communication with, for example, other processors, servers, or client terminals. The CPU 206 is also in communication with the data storage device. The data storage device may include an appropriate combination of magnetic, optical, or semiconductor memory, and may include, for example, RAM 202, ROM 204, a flash drive, an optical disk such as a compact disk, or a hard disk or drive. The CPU 206 and the data storage device may each, for example, be located entirely within a single computer or other computing device; or be connected to each other by a communication medium, such as a USB port, serial port cable, coaxial cable, Ethernet cable, telephone line, radio frequency transceiver, or other wired or wireless medium, or combination thereof. For example, the CPU 206 may be connected to the data storage device via the communication interface unit 208.The CPU 206 may be configured to perform one or more particular processing functions. The data storage device may store, for example, (i) an operating system 212 for the computing device 200; (ii) one or more applications 214 (e.g., a computer program code or a computer program product) adapted to direct the CPU 206 in accordance with the systems and methods described herein, and in particular in accordance with the processes described in detail with respect to the CPU 206; or (iii) database(s) 216 adapted to store information that may be used to store information required by the program. The operating system 212 and applications 214 may be stored, for example, in a compressed, uncompiled, and encrypted format, and may include computer program code. The program instructions may be read into a main memory of the processor from a computer-readable medium other than the data storage device, such as from ROM 204 or RAM 202. Although execution of sequences of instructions in the program causes the CPU 206 to perform the processing steps described herein, hard-wired circuitry may be used in place of, or in combination with, software instructions to implement the processes described herein. Thus, the systems and methods described are not limited to any specific combination of hardware and software. Suitable computer program code may be provided to perform one or more of the functions described herein. The program may also include program elements such as an operating system 212, a database management system, and “device units” that allow the processor to interact with computer peripheral devices (e.g., a video display, a keyboard, a computer mouse, etc.) via the input / output controller 210. The term “computer-readable medium” as used herein refers to any non-transitory medium that provides or participates in providing instructions to the processor of the computing device 200 (or any other processor of a device described herein) for execution. Such media can take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media include, for example, optical, magnetic, or opto-magnetic disks, or integrated circuit memory, such as flash memory. Volatile media include dynamic random access memory (DRAM), which typically constitutes main memory.Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, a hard disk, a magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical media, punched cards, paper tape, any other physical medium with hole patterns, RAM, a PROM, an EPROM or EEPROM (electronically erasable programmable read-only memory), a FLASH-EEPROM, any other memory chip or cartridge, or any other non-transitory medium from which a computer can read. Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to the CPU 206 (or any other processor of a device described herein) for execution. For example, the instructions may initially be on a magnetic disk of a remote computer (not shown). The remote computer may load the instructions into its dynamic memory and send the instructions over an Ethernet connection, a cable line, or even a telephone line using a modem. A communications device local to a computing device 200 (e.g., a server) may receive the data over the respective communications line and place the data on a system bus for the processor. The system bus carries the data to main memory, from which the processor retrieves and executes the instructions.Instructions received by main memory can optionally be stored in memory either before or after execution by the processor. Additionally, instructions can be received via a communication port as electrical, electromagnetic, or optical signals, which are exemplary forms of wireless communications, or data streams carrying various types of information. Figure 3 is a flow diagram of a process 300 for processing data relating to high-speed respiratory therapy, in accordance with an illustrative implementation. The process 300 may be implemented in the system 100 of Figure 1, the computing device 200 of Figure 2, or any other suitable system or device. Step 302 involves receiving first data indicative of one or more nasal cannula dimensions. Step 304 involves receiving second data indicative of a respirable gas flow rate. For example, the first data and second data may be received by a processor, such as the CPU 206. Step 306 involves calculating a respirable gas outflow rate based on the first data and the second data. Step 308 involves displaying the calculated outflow rate to a user. The first data may include an inside diameter or cross-sectional area of ​​one or more nasal prongs of a nasal cannula, such as nasal cannula 108 with prong 110. In some implementations, the first data is transmitted to a processor by a transmitter or by an RFID tag or other label associated with the nasal cannula. In some implementations, the second data is indicative of one or more flow rate measurements taken by one or more sensors. Process 300 may include additional steps. For example, a physician or other user may view the displayed rate, other displayed parameters, or the patient's medical status / records and decide to change the therapy conditions. In some implementations, process 300 further includes a step of receiving one or more user inputs. In some implementations, a user input is received indicating a desired change to at least one of the breathing gas flow rate and the output velocity. For example, a user input may indicate a modified flow rate at which to operate the system or device. Alternatively or additionally, a user input may indicate a modified rate. In some implementations, after receiving a user input, process 300 includes a step involving changing the flow rate to account for the user input indicating a change to the flow rate or output velocity.The flow rate may be changed by a controller, such as input / output controller 210. This step may be followed by a step of calculating a modified flow rate if the user input is a desired velocity, such that the modified flow rate corresponds to the desired velocity. In some implementations, an additional step involves calculating a modified velocity based on the user input and the first data. For example, the user input may be a desired flow rate, and the processor calculates the modified velocity based on the dimensions of the at least one nasal prong and the desired flow rate. In some implementations, steps 304 and 306 are altered such that the second data is indicative of the output velocity, and the breathing gas flow rate is calculated based on the first data and the second data. In some implementations, step 306 calculates additional system parameters based on the additional data. For example, the additional system parameters or data may include breathing gas humidity, oxygen concentration, target flow setpoint, pressure drop, temperature, therapy duration, FIO2, and / or battery level. Any of these system parameters / data may be displayed in step 308. System design and architecture A respiratory therapy unit configured to provide high-velocity respirable gas to a patient may include features for improved water management, heating, humidification detection, and automation, among others, resulting in increased patient comfort and safety, as well as improved treatment capacity. Figures 4 through 10 show examples of such respiratory therapy units and components thereof. Although these units and components are shown separately, it is to be understood that the units and / or components may be implemented in any combination or subcombination. It may be desirable to combine certain units and / or components in order to establish interoperability between certain units and / or components, which may lead to additional advantages or technical effects beyond those provided by each individual unit or component. In some implementations, the high velocity breathing gas is provided at a velocity of at least about 40 m / s and less than about 70 m / s, at least about 40 m / s and less than about 65 m / s, at least about 40 m / s and less than about 60 m / s, at least about 40 m / s and less than about 55 m / s, at least about 40 m / s and less than about 50 m / s, at least about 40 m / s and less than about 45 m / s, or about 40 m / s. In some implementations, the velocity is at least 50 m / s, at least 55 m / s, at least 60 m / s, at least 65 m / s, or at least 70 m / s. In some implementations, the velocity is greater than a velocity measured at any point along a flow path between a gas source and a nasal cannula tip configured to deliver the gas to a patient's nose.The systems, methods, and devices may employ a non-sealing cannula, and in particular, the cannula may be open to the atmosphere only at the nasal prong outlet. In some implementations, the gas provided at the prong outlet has a non-zero dynamic pressure. In some implementations, the respirable gas is humidified within the system. The gas flow path may be closed between a connector for the nasal cannula to the delivery tube and the prong outlet. Figure 4 shows a respiratory therapy system 400 for providing respirable gas to a patient, according to an illustrative implementation. The system 400 comprises a base unit 402, an auxiliary unit 404, and a supply tube 406. The base unit 402 contains a controller (not shown), and the base unit 402 is configured to direct a flow of respirable gas toward an auxiliary unit 404 when the auxiliary unit 404 is operatively coupled to the base unit 402. The auxiliary unit 404 directs the respirable gas through the gas path 412 to a vapor transfer cartridge (VTC) 416 disposed within the auxiliary unit 404. The auxiliary unit 404 is configured to receive a liquid (e.g., water) from the external reservoir 410 via the external liquid tube 414. Breathing gas flows from a VTC outlet 416 to supply tube 406 for delivery of the breathing gas to the patient.The supply tube 406 includes a patient connector 408. For operative coupling of the auxiliary unit 404 to the base unit 402, the base unit 402 includes a depression 418 sized to receive the auxiliary unit 404, and the auxiliary unit 404 includes a latch 420 for securing the auxiliary unit 404 in the depression 418. The auxiliary unit 404 includes a pump 424 configured to pump the liquid. The base unit 402 includes various couplings 422, 426 and 428 that are configured to interact with the auxiliary unit 404 or components thereof. A display 430 is included on the base unit 402. The base unit 402 may contain a fan configured to produce a flow of breathable gas. In the following, the system 400 is described using a fan as an example; however, it will be understood that the base unit 402 (and the other base units described herein) may alternatively use a compressor or be connected to an external gas source, such as a wall vent, an air tank, or an external fan. Additionally, a VTC 416 is implemented in the system 400; however, it will be understood that alternatives may be implemented in the system 400 (and the other systems described herein), such as a hot pot humidifier or heated cable. The alternatives may operate by disposing water onto a heating plate in a chamber and flowing breathable gas into the chamber (either over the water or through the water) to be humidified.A heated cable may be disposed in a conduit to further heat the humidified respirable gas prior to delivering the respirable gas to a patient. The system 400 may further include a nasal cannula (not shown) coupled to a patient connector 408. Alternatively, the patient connector 408 may be a nasal cannula or other gas delivery device. In either case, the system 400 may be operated with the system parameters previously discussed for high velocity respiratory therapy (i.e., the parameters in Tables 1 and 2). The nasal cannula or patient connector may be sized accordingly, and / or the ventilator may be operated at certain respirable gas flow rates. By using a ventilator, the system 400 may eliminate the need for an external source of pressurized air or respirable gas such as a pressurized tank or wall vent. The base unit controller 402 may be the computing device 200 of Figure 2. In some implementations, the outer reservoir 410 is a large container (>1 L, >2 L, >5 L, etc.), such as a bag or bottle, and the connector tube 414 may be removably connected to the auxiliary unit 404. The auxiliary unit 404 may be configured such that liquid is completely enclosed within the auxiliary unit 404 flowing from the outer reservoir 410. In this case, the liquid is kept separate from the base unit 402. This may prevent leakage and damage to components within the base unit 402. In some implementations, the gas path 412 is connected to the base unit 402 ventilator, but there is no other fluid communication between the base unit 402 and the auxiliary unit 404. The gas path 412 may be connected to the base unit 402 by a valve, such as the occlusion valves 652, 752, and 852 of FIGS. 6 . 7D, 8A and 8B.Such a valve may be used to control the flow rate of breathable gas entering the gas path 412 of the auxiliary unit 404. The valve may also interact with liquid flow to simultaneously control breathable gas flow rate and liquid flow rate. The valve may comprise components that are separately attached to the base unit 402 and the auxiliary unit 404, such that the valve is operable when the auxiliary unit 404 is fully seated in the depression 418 of the base unit 402, and the base unit control 402 actuates the valve. A gas seal, such as gas seals 660, 760 and 860 of Figures 6, 7A, 7B, 7D, 8A and 8B, may be attached to the auxiliary unit 404, in order to prevent gas leakage from the system 400 and to prevent liquid ingress into the base unit 402 during operation.The gas seal may be a flexible portion surrounding the valve, and the flexible portion is compressed to form a seal when the auxiliary unit 404 is fully seated in the depression 418 of the base unit 402. The flexible portion of the gas seal, throughout this disclosure, may be a film, a gasket, a ring or collar, or other suitable mechanism. Although the base unit 402 and the auxiliary unit 404 are fluidly connected to at least allow breathable gas to flow, it may be advantageous to otherwise minimize fluid connections or contact between the base unit 402 and the auxiliary unit 404. For example, minimizing fluid contact with the base unit 402 can prevent damage to electronic components. As another example, previous systems have relied on conductive liquid heating, which requires precise contact between two plates; thus, conductive heating is inefficient if precise contact cannot be established due to misalignment or deformation. Accordingly, the couplings 422, 426, and 428 are configured to be non-contact or contactless couplings. In general, this allows for a sealed auxiliary unit without any openings and minimal requirements for close tolerances.In some implementations, coupling 422 is a stator configured to magnetically couple to pump 424, which includes a rotor. Pump 424 may be cup-like in shape with a convex side protruding from auxiliary unit 404, and the stator may surround a depression cavity 418 such that pump 424 sits within the cavity when auxiliary unit 404 sits in depression 418. Pump 424 and coupling 422 may each be hermetically sealed, for example, to prevent fluid ingress into base unit 402. When auxiliary unit 404 is fully seated in base unit 402, the controller may operate the stator to magnetically generate rotation of pump rotor 424 to pump liquid through the auxiliary unit or through a supply tube jacket 406.As a result, the auxiliary unit 404 pumps liquid without an internal power source or other electronic components to control the pump 424, and there is no need for liquid to flow through the base unit 402, which separately houses the controller and other components that may be susceptible to, for example, water damage. Pump designs consistent with the present disclosure are described in U.S. Patent Application No. 15 / 783,566 , the contents of which are incorporated herein by reference in their entirety. Similarly, coupling 426 may be a non-contact or non-contact heating actuator, e.g., heat actuator 526 of FIG. 5, used to convey power to auxiliary unit 404 to heat the liquid. In some implementations, coupling 426 is a coil configured to heat a plate disposed in auxiliary unit 404. The plate may be, e.g., heating plates 527, 727, or 927 of FIGS. 5, 7C, 7F, and 9. The coil may heat the plate via induction. This may involve the coil inducing a current in a plate that is circular in shape and submerged in the liquid in auxiliary unit 404. The induced current generates heat in the plate due to a resistance of the plate.Because the heat is generated in the platen surrounded by liquid, the external surfaces of the auxiliary unit 404 and the base unit 402 that can be touched by a user / operator never exceed the temperature of the liquid. This configuration eliminates the need for precisely manufactured flat plates to come into intimate contact between a heat source on the base unit 402 and a conductive plate on the auxiliary unit 404. Inductive heating improves heating efficiency because the generated heat is isolated to the auxiliary unit 404 and does not heat the base unit 402. If the base unit 402 were to overheat, additional cooling would be required to remove the heat; however, the additional cooling is unnecessary with the present inductive heating configuration.Improved efficiency also allows longer operation of the system 400 if power is supplied by a battery (not shown) in situations where wall power is not available, for example, during mobile use or power outages. The heated liquid may be used to, in turn, heat breathing gas. For example, the supply tube 406 may include a jacket configured to receive heated liquid and transport the heated liquid around an inner lumen carrying the breathing gas. The heated liquid may travel along a full length of the supply tube 406 in a first direction toward the patient connector 408, and then return in an opposite direction again to an auxiliary unit 404. Heated liquid may also be transported in VTC 416 and vaporized into the breathing gas. For example, the liquid may be water used to humidify the breathing gas. Accordingly, the liquid may be heated to a target temperature, where the target temperature is a temperature at which the gas is to be delivered to the patient. The liquid may be circulated through the auxiliary unit 404 and the supply tube 406 and back to the inner reservoir.In some implementations, the liquid travels a liquid path from the outer reservoir to the inner reservoir (internal to the auxiliary unit 404), then to a heating section (e.g., where the heating plate may be arranged), then through the pump 424, then into the supply tube heating jacket 406, then into VTC 416, and then any remaining non-vaporized liquid is returned to the inner reservoir. A similar configuration is described in more detail in connection with Figure 5. Similar to coupling 426, coupling 428 may be a non-contact or non-contact level sensor, for example, level sensor 528 of Figure 5, configured to detect a liquid level in auxiliary unit 404. For example, auxiliary unit 404 may contain an inner reservoir, such as that described above, and inner reservoirs 532, 732, and 932 of Figures 5, 7C, 7D, 7F, and 9. Liquid is stored in the inner reservoir for use in, for example, VTC 416 and / or delivery tube heating jacket 406. When the liquid is water that vaporizes into the breathing gas within VTC 416, it may be desirable for the system or user to know the humidity of breathing gas provided to the patient.In some implementations, the inner reservoir has a constant diameter or cross-section (e.g., cross-section 536 of inner reservoir 532 in FIG. 5 ), such that the volume of liquid is linearly proportional to the liquid level in the reservoir. In this implementation, the level sensor 428 is configured to measure the liquid level when the auxiliary unit 404 is fully seated in the base unit 402. The level sensor 428 may be a capacitive sensor circuit positioned along the inner reservoir. In this implementation, the liquid level may be measured because the capacitance of the liquid changes as the liquid level changes. Capacitive sensing provides a non-contact means for sensing the liquid level. The level sensor 428 may output one or more signals indicating the measured liquid level to the controller at the base unit 402. The occlusion valve or a pinch valve disposed along the tube 414 may be used to isolate the volume of liquid in the auxiliary unit 404. In implementations where the liquid only leaves the system 400 when it vaporizes into the breathing gas in VTC 416, the controller may determine the amount of liquid vaporized (i.e., vaporization rate) or otherwise consumed (i.e., consumption rate) over time.In some implementations, this information is used to determine the necessary liquid flow rate from the external reservoir 410 in order to maintain the liquid level at a steady state, where the liquid flow rate from the external reservoir 410 equals the vaporization rate, in order to, for example, prevent the auxiliary unit 404 and the VTC 416 from drying out or ensure that the breathing gas is maintained at a constant vapor concentration (e.g., humidity). In other implementations, the liquid level is not at a steady state, but the controller determines, based on the vaporization flow rate, an appropriate time interval in which to allow a fixed volume of the liquid to enter the inner reservoir from the external reservoir 410 that is approximately equal to the amount of liquid vaporized during that time interval. From the calculated vaporization rate, the controller may also calculate the humidity of the respirable gas exiting the VTC 416 in implementations where the liquid is water. Another device, such as metering device 1086 of FIG. 10 , may be used to determine the flow rate (mass flow rate and / or volumetric flow rate) of respirable gas in the system 400. Such a device may be disposed on the base unit 402 to measure respirable gas entering or exiting the ventilator, or the device may be disposed on the auxiliary unit 404 to measure the flow rate of respirable gas entering or exiting the auxiliary unit 404 or the VTC 416. The device may alternatively be disposed along or within the supply tube 406 or patient connection 408 for proximal patient measurement of the respirable gas flow rate.In either case, the device sends one or more signals indicating the breathing gas flow rate to the controller. Furthermore, by knowing the consumption rate or vaporization rate, the controller can calculate the humidity of the breathing gas based on the liquid consumption / vaporization rate and the breathing gas flow rate, since the liquid in the closed auxiliary unit 404 can only exit the system 400 as vapor in the breathing gas when the flow of liquid from the external reservoir 410 is stopped. Knowing the humidity can serve several purposes. For example, inappropriately low or high humidity may indicate that the auxiliary unit 404, VTC 416, or another component of system 400 has become defective and requires replacement, allowing the controller to stop operation of system 400 and notify the operator before harm is done to the patient. As another example, the performance of system 400 can be monitored over time, using humidity as a monitored variable, in order to detect deterioration and extend the usable lifetime of system 400. In this case, there is no need to limit all devices to outlier performance during lifetime testing. Furthermore, by knowing the humidity, adjusting a temperature within VTC 416 relative to a temperature within delivery tube 406 can allow adjustment of the humidity if the humidity output is monitored for safety.In some implementations, the system 400 stores (e.g., in a memory) a range of safe humidity levels for patient breathing gas, and the controller is configured to determine whether the calculated humidity is within the safe range. If the calculated humidity falls outside the safe range, the controller may adjust pump power 424 to adjust the liquid flow rate and / or adjust ventilator power to adjust the breathing gas flow rate. In some implementations, the VTC 416 comprises a bypass gas passageway, configured to allow a portion of the breathing gas flow to flow through the bypass gas passageway where it is not humidified, and then be added back to the humidified gas outlet by the VTC 416. The gas flow rate through the bypass gas passageway may be controlled in order to control the humidity level in the combined breathing gas flow. The systems and methods described herein may utilize any of the humidity control methods described in U.S. Patent No. 10,596,345 filed December 31, 2014, entitled “Systems and Methods for Humidity Control,” which is incorporated herein by reference in its entirety. The latch 420 is configured to secure the auxiliary unit 404 in the depression 418 of the base unit 402 when the auxiliary unit 404 is properly positioned / seated in the depression 418 for proper operation of the system 400 and interoperability between the auxiliary unit 404 and the base unit 402. A user may press against the latch 420 to unlock the auxiliary unit 404 and remove it from the base unit 402. In order to ensure that the auxiliary unit 404 is fully seated in the depression 418 for proper operation, there may be one or more elements disposed on the base unit 402 and the auxiliary unit 404 configured to detect the presence, or precise alignment of the auxiliary unit 404 in the depression 418.In some implementations, the auxiliary unit 404 includes an RFID tag (e.g., RFID tag 550 of Figure 5) or other label, and the base unit 402 includes an antenna or reader (e.g., RFID reader 551 of Figure 5). The tag may be detected by the antenna or reader in a contactless manner when the tag is positioned near the antenna or reader, essentially when the auxiliary unit 404 is seated in the depression 418. Accordingly, the tag may also include information that can be read by the antenna or reader and transmitted to the controller or a memory of base unit 402. For example, the tag may include information describing the type of or feature of the auxiliary unit 404, such as low flow, high flow, aerosolization, humidification, oxygenation, nitric oxide, helium, and / or closed-loop oxygen control. The tag may also include information relating to the status of the auxiliary unit. 404 and / or its various components. For example, the information may include usage history (including date in use), shelf life or remaining life, embedded license, and / or recommended operating parameters (flow rates or humidity limits). The controller may use any of the information described above to determine and make appropriate adjustments to system 400 and any of its various components. For example, depending on the type or features of auxiliary unit 404, certain operations or features may be enabled or disabled by the controller according to the auxiliary unit 404 in use. RFID tags or other labels can provide additional information about an auxiliary unit, such as the type of auxiliary unit, when it was first used, the expiration date, etc. This can overcome the disadvantages of the aforementioned systems. In some systems, the device needs to be aware of a change in the auxiliary unit even if the primary unit is in standby mode. To detect an auxiliary unit change in these systems, RFID may require the device to use excessive power while in standby. As an example, an active valve may close the air path when the auxiliary unit is removed and close the water fill path when an auxiliary unit is installed. Such features may not function properly if the auxiliary unit is added or removed when the device is off or in standby mode.This can occur if the auxiliary unit is set up in advance to be ready for a patient. The device is off when the auxiliary unit is installed, and water can flow uncontrolled into the device. It would be beneficial for the device to turn on and close the valve. In some implementations, the auxiliary unit 404 includes one or more magnets (e.g., alignment marker 548 of FIG. 5), and the base unit 402 includes a Hall effect sensor (e.g., alignment sensor 549 of FIG. 5) configured to detect the presence of the magnet to determine in a non-contact manner whether the auxiliary unit 404 is fully seated in the depression 418. A Hall effect sensor measures a magnitude of a magnetic field and outputs a voltage proportional to the magnitude of the magnetic field. Accordingly, the Hall effect sensor can detect the magnetic field of the magnet when in close proximity.By using a magnet and the Hall effect sensor, the precise position of the auxiliary unit 404 can be detected, and a change in state can be detected even when the system 400 is in a standby or low power mode, because the Hall effect sensor can operate at a very low power when the system 400 is in standby, and a change in this Hall effect sensor can be used to wake up the system 400 to, for example, read the RFID tag or start operation of certain components, such as the ventilator or pump 424. As another example, the controller can be configured to close the occlusion valve to block the flow of breathing gas from the base unit 402 to the auxiliary unit 404 when the auxiliary unit 404 is removed, even if the system 400 is in standby, to ensure that the gas path is not left open when the disposable is removed.The magnet may be configured to have a narrow range, within which it may trigger the Hall effect sensor. The range may be less than about 5 mm, less than about 4 mm, less than about 3 mm, less than about 2 mm, or less than about 1 mm. In some implementations, the magnet is disposed within the latch 420 such that the Hall effect sensor is triggered by the magnet when the latch 420 is in the secured position. A bar code may be used on the auxiliary unit 404 in addition to or instead of an RFID tag or other label, such that a reader on the base unit 402 reads the bar code when the auxiliary unit 404 is engaged in the depression 418. The bar code may include information about one or more components, as described in connection with the RFID tag in this disclosure.As another option, base unit 402 includes an infrared (IR) proximity sensor having an IR beam positioned such that latch 420 breaks the beam, triggering the sensor, when auxiliary unit 404 is fully seated in depression 418. Other options for detecting auxiliary unit presence and storing / transferring data include quick response (QR) codes, global positioning system (GPS) chips, Bluetooth®, Bluetooth® low energy, near field communication (NFC), and pattern recognition matching. The system 400 may be configured to automatically switch to a standby or low power mode under certain conditions. For example, the system 400 may switch from standby mode when the auxiliary unit 404 is not detected, when the ventilator is turned off and a user has not interacted with the system 400 for a certain period of time, or when a user enters a command to switch the system 400 to standby mode. When it switches to standby or low power mode, the controller may generate an alert to notify the user of the change. The system 400 may be configured to be powered by a standard wall outlet or a main battery. In either case, the system 400 may include a backup battery. The backup battery may be a rechargeable battery, such as lithium-ion, lead-acid, nickel-cadmium, nickel-metal hydride, lithium-ion polymer, alkaline, or other equivalent.The backup battery may be configured to provide power to the system 400 when the wall outlet becomes unusable (e.g., during a power outage) or when the main battery requires replacement. In some implementations, the system 400 may operate solely on the backup battery for at least about 30 minutes, at least about 1 hour, at least about 2 hours, or at least about 5 hours. The standby or low power mode may limit the power usage of the system 400 to a percentage of the maximum power usage of the system 400 during normal operation (e.g., about 80%, about 70%, about 60%, about 50%, about 40%, about 30%, about 20%). In some implementations, the controller switches the system 400 to the standby or low power mode when the backup battery is in use.When in standby or low-power mode, the controller may disable certain features, for example, to reduce power consumption. For example, the controller may disable heating elements or supplemental gas input, allowing the fan to operate and one or more alarms (e.g., audit trail alarms, on-screen notifications 430). The system 400 may also include one or more temperature sensors, such as temperature sensors 542 and 544 of Figure 5. In some implementations, the base unit 402 includes one or more infrared (IR) temperature sensors configured to measure liquid temperatures in the auxiliary unit 404 by non-contact means. One or more signals indicating the liquid temperature may be transmitted from the sensor(s) to the controller. The controller may be configured to determine if the measured temperature is within a stored safe temperature range. If the temperature is within the safe range, then the controller may alert the user by one or more alarms (e.g., audit trail alarms, on-screen notifications 430) and / or change one or more controllable operational parameters to effect a change in temperature. This may involve changing the fan flow rate.In some implementations, the base unit 402 includes one or more IR temperature sensors configured to measure a temperature of the heater plate that is immersed in liquid in the auxiliary unit 404, for example, to detect overheating of the heater plate. In some implementations, the heater plate includes a tab protruding from the top of the heating plate as shown in Figure 9. The tab may be arranged such that it is the first portion of the heating plate to be exposed (not immersed in liquid) when the liquid is at a low level. When the tab is not immersed, it will heat up rapidly if the heating plate and heating element are in operation.A temperature sensor may be arranged to align with the tab when the auxiliary unit is seated, such that the temperature of the tab may be monitored by sending one or more signals indicating the tab temperature to the controller. When the tab heats rapidly during a low liquid level state of the auxiliary unit 404, the temperature sensor may detect the rapid increase in temperature and alert the controller. In response to detecting a rapid increase in tab temperature indicative of a low liquid level, the controller may be configured to turn off the heating element (e.g., the induction coil). In response to detecting a rapid increase in tab temperature indicative of a low liquid level, the controller may be configured to increase or open the flow of liquid from the external reservoir 410 by, for example, actuating the occlusion valve or pump 424.In response to detecting a rapid increase in reed temperature indicative of a low liquid level, the controller may be configured to completely shut down the system 400 and / or generate an alarm. An alarm may be audible or visual via the display 430. The supply tube 406 conducts the breathing gas to the patient. Jacketed supply tubes are typically smaller in inside diameter than heated wire supply tubes and have fewer associated problems. For example, the weight of liquid required to properly heat a larger tube can result in a poor user experience if the tube diameter is increased too much, because the user may have difficulty moving a tube substantially weighted down by liquid. Smaller jacketed supply tubes may work when the pressure from the source pressure is sufficiently high. In system 400, the breathing gas is pressurized and supplied from the ventilator in the base unit 402, without external pressurization in some implementations, so that limited pressure may be available. With a ventilator, the tube diameter needs to be increased to account for the lower source pressure.It may be advantageous to size the cross-sectional diameter of the delivery tube 406 as large as possible in order to accommodate the lowest back pressure while maintaining functionality. Generally, an increased diameter increases the weight of the delivery tube due to the greater volume of liquid required to heat the gas. Increasing the diameter can also lead to water accumulation in the delivery tube. Unlike larger heated cable tubes, which must be tilted to drain liquid to the patient, the smaller jacketed tube can deliver water to the patient simply by increasing the flow above a certain threshold where the water can be driven along the delivery tube by the breathing gas flow.Accordingly, an upper limit of the diameter may be set based on, when operating at a minimum breathing gas flow rate, the breathing gas velocity is sufficient to carry any liquid that has accumulated on the supply tube 406 such as rain to the patient connector 408 where it may be collected and removed. In some implementations, the breathing gas flow rate is 5 L / min, and the supply tube inner diameter is less than or equal to about 0.26 in (0.6604 cm). The supply tube 406 may be constructed of a flexible material in order to allow a user or operator to manipulate the supply tube 406 without obstructing the flow of breathing gas. The increased diameter may also make the delivery tube more prone to kinking. Accordingly, the delivery tube 406 may be constructed to be kink-resistant. In some implementations, the delivery tube 406 includes a jacket. As discussed above, the heated liquid may be used to, in turn, heat respirable gas. For example, the delivery tube 406 may include a jacket configured to receive heated liquid and transport the heated liquid around an inner lumen carrying the respirable gas. The heated liquid may travel along a full length of the delivery tube 406 in a first direction toward the patient connector 408, and then return in an opposite direction again to an auxiliary unit 404.In some implementations, the jacket includes a plurality of ribs extending in a radial direction through the jacket from a first conduit defining a breathing gas lumen to a second conduit, wherein the jacket is defined as the annular space between the first conduit and the second conduit. The radial ribs define two or more channels in the jacket through which liquid may flow. The radial ribs allow the delivery tube 406 to be bent in any direction without kinking by preventing collapse of the inner breathing gas conduit when the supply tube 406 is bent. In some implementations, under flexing of the supply tube 406, one or more of the channels may collapse, but at least some of the channels and the breathing gas lumen remain open to allow liquid and breathing gas to flow, respectively.The jacket having radial ribs may mimic a thick-walled tube to prevent collapse of the breathing gas lumen. In some implementations, the breathing gas lumen wall has a thickness proportional to the breathing gas lumen's inside diameter. In some implementations, the outer wall, defining the jacket, has a thickness proportional to the outer diameter of the delivery tube 406 minus the inner diameter of the breathing gas lumen. In some implementations, each radial rib has a width proportional to the breathing gas lumen wall thickness. The display 430 may be configured to display one or more parameters of the system 400. For example, the display 430 displays any of: breathing gas flow rate, liquid vaporization / consumption rate, humidity, liquid level, breathing gas velocity, hot plate temperature, and liquid temperature. In some implementations, the display 430 acts as an interface both for alerting the user of system parameters and for accepting user input. User inputs, such as those previously described, may include blank values ​​for any of these parameters. The user inputs may be transmitted to the controller, which is configured to adjust the parameters, for example, by actuating one or more of the components of the system 400. Breathing liquid and gas flow paths As described in Figure 4, the liquid in the systems described herein follows a flow path during the operation of such systems. Since there are various components that may utilize or act upon the liquid, there may be an ordered flow path through which the liquid flows and undergoes various state changes or manipulations. Figure 5 is a cross-section of a respiratory therapy system 500 configured to deliver respirable gas to a patient, in accordance with an illustrative implementation. The system 500 includes a base unit 502 having a depression 518 in which the auxiliary unit 504 sits. The latch 520 secures the auxiliary unit 504 in its current position. Liquid is stored in the inner reservoir 532 of the auxiliary unit 504. The outer reservoir 510 supplies liquid through the outer tube 514 to the inner tube 515 of the auxiliary unit 504. A valve 540 is disposed along the tube 514. Liquid flowing through the inner tube 515 is transported to the inner reservoir 532 through the inner reservoir inlet 534. A vent 538 is provided in the inner tank 532. The liquid flows out of the inner tank 532 and then along the heating plate 527 immersed in the liquid.After heating, the liquid flows into the pump 524 and then out the pump outlet 546. The auxiliary unit 504 also includes an RFID tag 550 and an alignment marker 548. The base unit 502 includes a stator 522, a level sensor 528, a heat actuator 526, an RFID reader 551, an alignment sensor 549, and temperature sensors 542 and 544. The system 500 and its components may be combined with or modified by the systems and devices described in Figures 4, 6, 7A to 7F, 8A, 8B, 9, and 10. The various components in the base unit 502 may be configured to couple corresponding components of the auxiliary unit 504 in a contactless manner. These components may be operatively coupled to a controller in the base unit 502 for actuation and / or electronic communication. In some implementations, the stator 522 is configured to magnetically couple to a rotor of the pump 524. By magnetically coupling to the rotor, the stator 522 may induce rotational motion in the rotor for contactless control of the pump 524. The heat actuator 526 may transport heat by contactless means to or generate heat in the heating plate 527 submerged in the liquid. The heat actuator 526 may be operatively coupled to the controller to allow indirect control of the rate at which heat is transferred to the liquid surrounding the heating plate 527.In some implementations, the heat actuator 526 is a coil configured to generate a current in the heating plate 527 via induction, the current generating heat due to a resistance in the heating plate 527. The generated heat may be transferred from the submerged heating plate 527 to liquid on either side. In some implementations, the level sensor 528 is a capacitive sensor configured to measure capacitance in the inner reservoir 532. The inner reservoir 532 may have a constant cross section 536 such that the measured capacitance is indicative of a liquid level in the inner reservoir 532. By utilizing capacitive sensing, the system may provide early warning of low liquid levels and active control of the water level in the system.Flow rate and humidification measurements can also be made more accurate with the use of capacitive sensing to accurately measure remaining liquid water. In some implementations, RFID reader 551 detects the presence of RFID tag 550 when auxiliary unit 504 is within depression 518. RFID reader 551 may read information stored on RFID tag 550. In some implementations, alignment marker 548 is disposed on latch 520, and alignment sensor 549 is configured to detect the presence of alignment marker 548 when latch 520 is in a closed position. Latch 520 in an unlocked position 521 is shown in FIG. 5 by a dashed outline. In some implementations, alignment marker 548 is a magnet, and alignment sensor 549 is a Hall effect sensor configured to detect the magnetic field of the magnet. Alignment sensor 549 may transmit to the controller a signal indicating that auxiliary unit 504 is fully seated in depression 418 when alignment marker 548 is detected.A bar code may be used on the auxiliary unit 504 in addition to or instead of the RFID tag 550, such that the reader 551 on the base unit reads the bar code when the auxiliary unit 504 is fully engaged in the depression 518 of the base unit 502. The bar code may include information about one or more components, as described in connection with the RFID tag in this disclosure. As an alternative to the alignment marker 548, the base unit may include an infrared (IR) proximity sensor having an IR beam positioned such that the latch 520 breaks the beam, triggering the sensor, when the auxiliary unit 504 is fully seated. In some implementations, the temperature sensors 542 and 544 are IR temperature sensors configured to measure temperatures in the auxiliary unit 504.For example, temperature sensor 542 may be positioned to measure a temperature of heating plate 527, and temperature sensor 544 may be positioned to measure a temperature of liquid flowing away from heating plate 527. Liquid may flow out of inner reservoir 532 to heating plate 527 and pump 524 due to hydrostatic pressure resulting from the height of inner reservoir 532 positioned above heating plate 527 and pump 524. In some implementations, pump 524 generates a suction pressure that draws liquid from inner reservoir 532, past heating plate 527, and into pump 524. Rotational motion of a rotor (not shown) in pump 524 may be used to transport the liquid along a flow path. The flow path may be partially enclosed within auxiliary unit 504. In some implementations, system 500 further includes a jacketed delivery tube (such as delivery tubes 406 and 706 of FIGS. 4 , 7A, 7B, and 7D-7F), and the flow path may extend through the jacket of the delivery tube.In some implementations, pump outlet 546 is in fluid communication with the jacket such that heated liquid is pumped into the jacket for heating of breathing gas in an inner lumen of the delivery tube, the inner lumen being concentrically surrounded by the jacket. Pump 524 may generate sufficient pressure such that liquid is transported through a first lumen of the jacket away in a direction away from the auxiliary unit 504 and through a second lumen of the jacket in a direction away from the auxiliary unit 504. In some implementations, the auxiliary unit 504 houses a vapor transfer cartridge (VTC), such as VTC 416, 716, and 816 of FIG. 4, and liquid is transported from the delivery tube jacket into the VTC for humidification of the breathing gas. In some implementations, pump 524 transports liquid in a cyclical manner, in which liquid ejected from pump outlet 546 is first pumped through the delivery tube jacket, then through the VTC, into inner reservoir 532 (e.g., through a recycled liquid reservoir inlet not shown) and finally past heating plate 527 before returning to pump 524. In this case, pump 524 generates sufficient pressure to transport the liquid through a complete cycle of this flow path so that the liquid returns to pump 524. This ordered flow path may define a fluid flow cycle or circuit. This circuit may be a closed circuit, for example, if valve 540 is closed to prevent fluid flow through outer tube 514. The circuit may be sealed such that, when the circuit is closed, liquid only leaves the circuit as vapor in the VTC.In some implementations, the volume of liquid in the circuit is in a steady state such that the rate of liquid leaving the circuit as vapor at the VTC equals the rate of liquid entering the circuit through tubes 514 and 515 from the external reservoir 510. In other implementations, discrete volumes of the liquid are transported from the external reservoir 510 through tubes 514 and 515 to the inner reservoir 532 at time intervals such that the discrete volume for a given time interval equals the amount of liquid vaporized during that time interval. The valve 540 may be used to isolate the volume of liquid in the circuit, for example, by closing the valve 540 to stop all liquid flow through the tubes 514 and 515 of the external reservoir 510. In implementations, the level sensor 528 outputs one or more signals to the controller in the base unit 502 indicative of the liquid level in the inner reservoir 532. The inner reservoir 532 may have a constant cross section 536, such that the liquid level may be directly proportional to the volume of liquid in the inner reservoir 532. When the liquid flow is occluded by the valve 540, liquid can only exit the circuit by vaporization in the VTC. The controller may determine the vaporization rate (or liquid consumption rate by the VTC) based on a change in the liquid level in the inner reservoir 532 over a period of time.If the controller also knows the breathing gas flow rate, for example, by receiving one or more signals indicating the flow rate (e.g., from the measuring device 1086 of Figure 10), then the controller may be configured to determine the vapor or moisture content of the breathing gas using the breathing gas flow rate measurement(s) and the liquid level measurements. The absolute humidity may also be determined by the controller by also considering temperature measurements, for example, indicated by one or more signals transmitted to the controller by temperature sensors configured to measure the temperature of the breathing gas in the VTC, at the VTC outlet, or in the supply line. Although external valves, such as valve 540, can be used to control the flow of liquid from an external reservoir, it may be advantageous to have a valve built into an auxiliary unit to allow, for example, optimized control of the liquid flow by a controller. Furthermore, as the use of breathing gas and liquid is intertwined, a built-in valve that provides simultaneous control over the breathing gas and liquid flows can allow for further optimization and ease of control. Figure 6 shows a portion of a respiratory therapy system 600 having a base unit 602 and an auxiliary unit 604 joined by an occlusion valve 652, according to an illustrative implementation. The occlusion valve 652 is actuated by an actuator 654, which controls the positioning of the gas path valve seal 655. Respirable gas enters the valve 652 through the base unit gas path 613 and exits the valve 652 through the auxiliary unit gas path 612. Liquid travels through outer tube 614 and into valve 652 through liquid inlet 658, and exits valve 652 through inner tube 615. Valve 652 includes a gas seal 660 that is configured to form a closed annular space around gas path valve seal 655 between paths 613 and 612.Valve 652 includes a flexible portion 656 having a liquid path valve seal 657. System 600 and its components may be combined with or modified by the systems and devices described in Figures 4, 5, 7A to 7F, 8A, 8B, 9 and 10. The actuator 654 is coupled to a controller (not shown) in a base unit 602. The actuator 654 may be configured to move in a linear direction, as shown by the up and down arrows on the actuator 654. The controller may send one or more signals to the actuator 654 in order to adjust the position of the actuator 654. The path valve seal 655 is coupled to the linear actuator 654, such that linear movement of the actuator 654 would also move the gas path valve seal 655 in a linear direction, allowing the gas path valve seal 655 to be positioned in a plurality of positions along the linear direction. The gas path valve seal 655 as shown in Figure 5 is in a middle position, which allows gas flow from the gas path 613 into the annular space defined by the gas seal 660 in the valve 652.Since the position of gas path valve seal 655 may be varied, the flow rate of respirable gas from gas path 613 may be varied as a result of actuating gas path valve seal 655 by actuator 654. From the mid-position of gas path valve seal 655 as shown in Figure 5, actuator 654 may be configured to raise gas path valve seal 655 to enlarge the gap and increase the flow rate of respirable gas through valve 652. Actuator 654 may be configured to lower gas path valve seal 655 to narrow the gap defined by gas path valve seal 655 and decrease the flow rate of respirable gas through valve 652.The actuator 654 may lower the gas path valve seal 655 by a certain distance, such that the gas path valve seal 655 completely occludes the flow of breathable gas from the gas path 613, reducing the flow rate of breathable gas to zero. The flexible portion 656 may similarly have a variable position by virtue of its flexibility. The flexible portion 656 and the liquid path valve seal 657 may move in a linear direction indicated by the up and down arrows on the liquid path valve seal 657. The liquid path valve seal 657 may be integrally formed in the flexible portion 656 or disposed in the flexible portion 656. The liquid path valve seal 657 may be rigid relative to the flexible portion 656, for example, by having a greater thickness than the portion 656 or having a reinforced structure. The gas path valve seal 655 may be lifted by the actuator 654 from its position indicated in Figure 6 such that the gas path valve seal 655 abuts the liquid path valve seal 657.Accordingly, controlling the actuator 654 may allow the system 600 to adjust the position of the liquid path valve seal 657 by biasing it against the gas path valve seal 655. Adjusting the position of the liquid path valve seal 657 either narrows or widens a gap between the liquid inlet 658 and the liquid path valve seal 657, wherein liquid in the outer tube 614 flows through the gap as it enters the valve 652 in its path in the auxiliary unit 604. Narrowing and widening the gap may decrease and increase, respectively, the flow rate of liquid out of the liquid inlet 658. Accordingly, valve 652 may provide simultaneous control of both breathing gas and liquid flow rates into auxiliary unit 604. In some implementations, linear actuation of actuator 654 allows for non-discrete positioning of valve seals 655 and 657. In some implementations, the controller is configured to control actuator 654 between a discrete set of positions. In some implementations, the array includes a variety of positions > 1, > 2, > 5, > 10, or > 20. In some implementations, three distinct positions of valve 652 are enumerated: (1) a retracted position, wherein gas path valve seal 655 is fully lowered, and liquid path valve seal 657 is non-abutting, such that gas path 613 is fully occluded, and liquid inlet 658 is fully open to allow liquid flow from outer tube 614 to tube 615;(2) a middle position (shown in Figure 5), wherein the gas path valve seal 655 is partially raised to allow flow of breathable gas from the gas path 613, and the liquid path valve 657 is unabutted to allow liquid flow from the outer tube 614 out of the liquid inlet 658 into the inner tube 615; and (3) an extended position, wherein the gas path valve seal 655 is fully extended to allow flow of breathable gas from the gas path 613 and to abut the liquid path valve 657 so as to occlude the liquid inlet 658, blocking liquid flow from the outer tube 614. These three positions are summarized in Table 3.; Table 3: Exemplary positions of an occlusion valve for controlling gas and liquid flows in an auxiliary unit described herein. Valve Position Gas Path Liquid Path Retracted Closed Open Medium Open Open Extended Open Closed ! 705*0 / 1 / 7707 / 3 / YILI The three positions described above may be used for certain purposes. For example, the middle position is used to refill an inner reservoir of auxiliary unit 604 while supplying breathing gas. The reservoir may be inner reservoir 532 of Figure 5. The extended position may be used to isolate the inner reservoir to prevent overfilling or when the system 600 is in a standby or low power mode, as described herein. For example, the standby mode may involve only providing breathing gas without vaporizing liquid into the breathing gas through a VTC. The standby mode may be initiated by the controller when a main battery of base unit 602 is removed and the system 600 operates on power from a backup battery in the base unit 602. The retracted position may be used when the auxiliary unit 604 is removed or separated from the base unit 602.In this circumstance, the retracted position may be advantageous in order to protect the gas path 613 of the base unit 602 from ingress (e.g., from liquid, dust, particles, contaminants, cleaning solvents). The controller may be configured to operate the actuator 654 to alternate between the valve positions based on received signals. In some implementations, the auxiliary unit 604 further comprises an inner reservoir (such as an inner reservoir 532 of Figure 5) for holding liquid and a level sensor (such as a level sensor 538 of Figure 5) configured to measure the liquid level in the inner reservoir. The level sensor may transmit a signal to the controller indicating that the liquid level is substantially low, and the controller may respond to the signal by actuating the valve 652 from the extended position to the mid-position, allowing liquid flow to the inner tube 615.A low liquid level may also be indicated to the controller by a temperature sensor (such as temperature sensor 542 of FIG. 5) that measures the temperature of a heating plate immersed in liquid in the auxiliary unit 604, such that a low liquid level is indicated by a rapid increase in heating temperature when at least a portion of the heating plate is no longer immersed in liquid. In response to one or more signals from the temperature sensor, the controller may actuate the valve 652 from the extended position to the mid-position to allow liquid flow in the inner tube 615 to refill the inner reservoir and re-immerse the heating plate.In some implementations, the auxiliary unit 604 comprises an alignment marker (such as alignment marker 548 of Figure 5), and the base unit 602 includes an alignment sensor (such as alignment sensor 549 of Figure 5) configured to detect the presence of the alignment marker when the auxiliary unit 604 is fully seated in the base unit 602. The alignment sensor may transmit a first signal to the controller indicating that the presence of the alignment marker has been detected, indicating that the auxiliary unit 604 is fully seated, and the controller may respond to the first signal by actuating the valve 652 from the retracted position to the mid-position, allowing flow of breathable gas and liquid into the gas path 612 and inner tube 615, respectively, of the auxiliary unit 604. The controller may alternatively respond to the first signal by actuating the valve 652 from the retracted position to the extended position, for example, if the inner tank is filled with liquid.The alignment sensor may transmit a second signal to the controller indicating that it no longer detects the presence of the alignment marker, indicating that the auxiliary unit 604 has been untethered or dislodged, and the controller may respond to the second signal by actuating the valve 652 from the extended or mid-positions to the retracted position. In some instances, the valve 652 remains in the extended position for a fixed period of time, or until the liquid in the interior reservoir of the auxiliary unit 604 is depleted, in order to measure the vaporization rate. The valve 652 may then be moved to the mid-position to refill the reservoir via the liquid flow path 615. The flexible portion 656 separates the liquid flow path from the breathable gas flow path, and its flexibility allows control of the liquid flow rate from the breathable gas side of the flexible portion 656. The flexible portion 656 may be constructed from a material that is substantially flexible to allow the upward force of the gas path valve seal 655 to vary the position of the flexible portion 656 and the liquid path valve seal 657. Suitable materials may include ethylene vinyl acetate, polyethylene, polyethylene-based polyolefin elastomers, polypropylene, polyurethane, styrene butadiene copolymer, thermoplastic polyester elastomer, polypropylene-based elastomers, thermoplastic polyurethane elastomer, polyvinylidene fluoride, fluorinated ethylene propylene, nylon, nylon blends, polystyrene, polyvinyl chloride, polytetrafluoroethylene, and thermoplastic vulcanizate.In some implementations, the gas seal 660 is formed of a flexible material such that it may be compressed when the auxiliary unit 604 is seated in the base unit 602 to form a sealed annular space between the gas paths 613 and 612, as shown in Figure 6 where the gas seal 660 forms an annular space around the gas path valve seal 655. The gas seal 660 may be formed of the same material as the flexible portion 656 or any of the materials listed above. Auxiliary unit design In accordance with the implementations described above and below, an auxiliary unit for a respiratory therapy system is provided herein. Figures 7A through 7F show various views and cross-sections of an auxiliary unit 704, in accordance with an illustrative implementation. The auxiliary unit 704 may be implemented, for example, in the respiratory therapy systems 400, 500, 600, and 800 of Figures 4, 5, 6, 8A, and 8B. Figure 7A shows auxiliary unit 704 having a pump 724, a gas seal 760, and an external tube connector 762, according to an illustrative implementation. A supply tube 706 is connected to auxiliary unit 704, and a patient connector 708 is disposed at a distal end of supply tube 706. The auxiliary unit 704 is configured to be seated in a base unit (not shown) / zQQQn / zznz / q / uil of a respiratory therapy system, which is configured to provide pressurized respirable gas from a ventilator in the base unit to the auxiliary unit 704 during operation. The base unit 402 of Figure 4 is an example of a base unit that can receive the auxiliary unit 704. The gas seal 660, which is part of an occlusion valve, forms a sealed flow path for breathable gas to enter the auxiliary unit 704 of the base unit when the auxiliary unit 704 is seated in the base unit.The external tube connector 762 is configured to connect an external tube (not shown) that provides liquid to the auxiliary unit 704 from an external reservoir (not shown). For example, the external tube 414 and the external reservoir 410 of Figure 4 may be used in this implementation. The pump 724 is configured to transport the liquid from within the auxiliary unit 704. The supply tube 706 is configured to receive a flow of respirable gas from the auxiliary unit 704 and transport the respirable gas to a patient, via a patient connector 708 at the distal end of the supply tube 706. In some implementations, a nasal cannula is connected to the patient connector 708 to provide the respirable gas into at least one nostril of the patient. The respirable gas may be humidified with liquid by a VTC in the auxiliary unit 704. The pump 724 may transport the liquid along a flow path, including through the VTC where at least a portion of the liquid may be vaporized into the respirable gas which is simultaneously passed through the VTC.When the auxiliary unit 704 is seated in the base unit, the pump 724 may be coupled to a pump driver on the base unit, and the pump driver may be operatively coupled to a controller which can control the power supplied to the pump 724. For example, the pump 724 may include a rotor which is configured to be magnetically coupled to a stator on the base unit. Through the magnetic coupling, rotational motion of the rotor is generated and used to transport fluid along the flow path. In some implementations, the flow path includes a supply tube jacket 706. Figure 7B shows an alternate viewing angle of the auxiliary unit 704. From this angle, a ballast 720 is shown on the side of the auxiliary unit 704, in accordance with an illustrative implementation. The latch 720 secures the auxiliary unit 704 to the base unit when the auxiliary unit 704 is fully seated. The supply tube 706 connects to the auxiliary unit outlet 772. The latch 720 allows the auxiliary unit 704 to be locked and unlocked from its fully seated position in the base unit. The latch 720 may allow locking of the auxiliary unit 704 by having a ridge that resides in a notch in the base unit. A user or operator may press against the latch 720 to release the latch 720 from the notch and unlock the auxiliary unit 704 when it is removed from the base unit. The latch 720 may have one or more components embedded therein. For example, a marker, such as an alignment marker 548 of Figure 5, may be embedded in the latch 720, and the base unit may include a sensor, such as an alignment sensor 549 of Figure 5, configured to detect the presence of the marker when the auxiliary unit 704 is fully seated in the base unit and the latch 720 is closed.In some implementations, the marker is a magnet, and the sensor is a Hall effect sensor configured to detect the magnet's magnetic field. In some implementations, the latch 720 includes a tag. RFID, such as RFID tag 550 of Figure 5, and the base unit includes an RFID reader, such as RFID reader 551 of Figure 5, configured to detect the presence of the RFID tag and read information stored on the RFID tag. The information on the RFID tag may identify the auxiliary unit 704 as having certain functionalities, may provide usage history of the auxiliary unit 704, and may provide recommended system parameters, such as flow rates, humidity level, and temperature. A bar code may be used on the auxiliary unit 704 in addition to or instead of an RFID tag or other label, or magnet, such that a reader on the base unit reads the bar code when the auxiliary unit 704 is fully engaged in the depression of the base unit. The bar code may include information about one or more components, as described with respect to labels in this disclosure.As another option, the base unit includes an infrared (IR) proximity sensor having an IR beam positioned such that the latch 720 breaks the beam, triggering the sensor, when the auxiliary unit 704 is fully seated. Other options for detecting auxiliary unit presence include quick response (QR) codes, global positioning system (GPS) chips, Bluetooth®, Bluetooth® low energy, near field communication (NFC), and pattern recognition matching. The auxiliary unit outlet 772 functions as a port for connecting the supply tube 706 to the auxiliary unit 704 for transmission of the breathing gas. The outlet 772 may be shaped such that the supply tube 706 can be bent and rotated in the outlet 772 without being kinked by the edges of the outlet 772. The shape of the outlet 772 may also prevent dislodgement of the supply tube 706 from the auxiliary unit 704. In some implementations, the outlet 772 is tapered. In some implementations, the outlet 772 is beveled. In some implementations, the outlet 772 is threaded. The outlet 772 may be configured to have no hard edges that could kink or damage the supply tube 706; for example, the outlet 772 may be rounded. Figure 7C shows a cross-section of auxiliary unit 704 which includes, in addition to the previously described components, a VTC 716, a heating plate 727, an inner reservoir 732, and a delivery connector 768, according to an illustrative implementation. Liquid is provided to the inner reservoir 732 at a reservoir inlet 734 which receives liquid from an inner tube (not shown), for example, inner tubes 515 and 615 of Figures 5 and 6. The liquid flows out of the inner reservoir 732 past the heating plate 727, which is submerged in the liquid during operation. The liquid is drawn into a pump 724 which expels the liquid through a pump outlet 746. The VTC 716 has a first cap 764 configured to receive breathing gas and a second cap 765 configured to send breathing gas to the supply connector 768. The VTC 716 also includes the VTC liquid inlet 766 and the VTC liquid outlet 767.The supply connector 768 is configured to convey breathing gas from the second cap 765 of VTC 716 to the supply tube 706 via the connector gas outlet 769. The supply connector 768 further includes the connector liquid outlet 770 and the connector liquid inlet 771. Liquid entering the auxiliary unit 704 through the liquid tube connector 762 is directed to the reservoir inlet 734 by an inner tube (not shown), such as the inner tube 515 of Figure 5. Liquid stored in the inner reservoir 732 may flow out of the inner reservoir 732 to a heating section where the heating plate 727 is submerged in liquid. In some implementations, the liquid flows into the heating section due to hydrostatic pressure and / or gravitational flow, a result of the inner reservoir 732 being positioned above the heating section. In some implementations, the pump 724 generates a suction pressure that draws liquid from the inner reservoir 732 and into the heating section before being drawn into the pump 524. When the auxiliary unit 704 is seated in the base unit, the heating plate 727 may be coupled to a heat actuator on the base unit.In some implementations, the heat actuator is a coil configured to generate a current in the heating plate via induction, and the current produces heat due to a resistance in the heating plate. Liquid flows or is drawn into pump 724 from the heating section. The pump expels the liquid out of pump outlet 746, which is in fluid communication with connector liquid outlet 770 of supply connector 768. Supply connector 768 may be an overmolded rubber piece having one or more lumens. Connector liquid inlet 770 conveys heated, pumped liquid from pump outlet 746 into a supply tube jacket 706. The jacket concentrically surrounds an inner gas passage through which breathing gas is conveyed, such that heated liquid flowing through the jacket isolates the breathing gas in the inner gas passage. This feature may be advantageous in maintaining a sufficiently high breathing gas temperature to prevent vapor rain into the breathing gas.Fallout occurs when vapor in the breathing gas condenses to its liquid form during gas delivery. This condensation can cause clogging of supply tube 607, the patient connector 708, or a nasal cannula connected to the patient connector 708. The heated liquid travels in two directions in the jacket, and the jacket accordingly includes at least two lumens or channels, where each lumen or channel connects to either the connector liquid outlet 770 or the connector liquid inlet 771. For example, liquid is pumped through the connector liquid outlet 770 into a first jacket channel which transports the liquid along the supply tube 706 in a first direction toward the patient connector 708.At the distal end of the supply tube 706, where the patient connector 708 is disposed, the liquid may change direction and enter a second channel which transports the liquid along the supply tube 706 in a second direction, which is substantially opposite to the first direction. The second channel transports the liquid to the connector liquid inlet 771 of the supply connector 768. The connector liquid inlet 771 is in fluid communication with the VTC liquid inlet 766 in order to transport the fluid from the jacket to the VTC 716. Within the VTC 716, the liquid may vaporize into the breathable gas transported in the VTC 716 through the first cap 764. For example, the liquid may be water, and the VTC 716 may from the second cap 765 receive a stream of humidified breathable gas containing water vapor. For vaporization to occur, the temperature in the VTC 716 may be at or near the gas therapy temperature. The heating plate 727 may heat the liquid to a sufficiently high temperature, for example, about 100°F (37.78°C). The VTC 716 may contain a plurality of fibers, such as permeable fibers or semi-permeable fibers 884 of Figure 8B, which allow vapor to pass from the liquid flow into the breathable gas flow.Liquid that is not vaporized in the VTC 716 may flow out of the VTC liquid outlet 767, which returns the liquid to the inner reservoir 732. Breathable gas exiting the second cap 765 of VTC 716 is directed through the gas outlet connector 769 of the supply connector 768 into the supply tube 706. The breathable gas, which may be humidified or contain vapor, flows through the interior gas passage of the supply tube 706 and is insulated or heated by liquid flowing through the jacket. At the patient connector 708, the breathable gas may be delivered directly to the patient or at one or more additional devices, such as a face mask or nasal cannula. Suitable nasal cannulae are described above and specifically with reference to FIG. 1. Figure 7D is a cross-sectional view of the auxiliary unit 704, according to an illustrative implementation. In this view, an occlusion valve 752 is shown in the auxiliary unit 704. The supply tube 706 is connected to the supply connector 768 at the auxiliary unit outlet 772. The occlusion valve 752 receives liquid flow through the external tube connector 762. A flexible portion 756 includes a liquid path valve seal 757 disposed downstream of the valve liquid inlet 658. The inner tube 715 is in fluid communication with the valve 752 and the inner reservoir 732. The gas path 712 is in fluid communication with an annular space formed by the gas seal 660 and with the first cap 756 of VTC 716. The occlusion valve 752 may be the occlusion valve 652 of Figure 6. The occlusion valve 752 is configured to engage the base unit when the auxiliary unit 704 is fully seated. As described with respect to Figure 6, the base unit may include a controller, an actuator, and a gas path valve seal. The controller operates the actuator to adjust a position of the gas path valve seal to control the flow of breathing gas from the base unit to the auxiliary unit 704.The gas path valve seal may be lifted against the liquid path valve seal 757 in order to simultaneously control the flow rate of liquid through the occlusion valve 752, because the liquid path valve seal 757 is a rigid piece attached to the flexible portion, which portion may flex to lift the liquid path valve seal 757 to narrow an opening between the liquid path valve seal 757 and the valve liquid inlet 758. The actuator, the gas path valve seal, and the liquid path valve seal may have, but are not limited to, three positions which are summarized in Table 3. The controller may operate the actuator to change between each of these positions based on system inputs or received signals, as described with respect to Figure 6.Breathable gas may be directed by valve 752 into gas path 712, which conveys breathable gas to first cap 764 of VTC 716. Liquid may be directed by valve 752 into inner tube 715 which conveys liquid to inner reservoir 732. The supply tube 706 connects to the supply connector 768 at the auxiliary unit outlet 772 to receive flows of respirable gas and liquid. The supply tube 706 includes an inner gas conduit 707 configured to receive respirable gas from the second cap 765 of VTC 716 through the gas outlet connector 769 of the supply connector 768. The supply tube 706 includes a first jacket channel 774 configured to receive liquid from the pump outlet 764 through the liquid outlet connector 770 of the supply connector. 768, liquid flows through the first jacket channel 774 and a second jacket channel 775, for example, to heat or insulate the respirable gas in the inner gas conduit 707. In some implementations, the first jacket channel 774 transports liquid in a first direction away from the auxiliary unit outlet 772 and toward the patient connector 708.The first and second jacket channels 774 and 775 each have distal ends disposed within the patient connector 708, which may allow fluid communication between the first and second jacket channels 774 and 775. For example, fluid flows in a first direction through the first jacket channel 774 and, upon reaching the patient connector 708, flows out of the distal end of the first jacket channel 774 and into the distal end of the second jacket channel 775. The fluid may then flow through the second jacket channel 775 in a second direction, which may be substantially opposite to the first direction. The second jacket channel 775 conveys the fluid back to the jacket connector 768 through the connector fluid inlet 771.In some implementations, the first jacket channel 774 covers a first portion of the inner gas conduit 707, the first portion having an approximately semicircular cross-sectional shape. The second jacket channel 775 may cover a second portion of the opposite side of the inner gas conduit 707, the second portion having an approximately semicircular cross-sectional shape. The auxiliary outlet 772 in this implementation has a rounded (threaded) shape which may prevent kinking of the supply tube 706 and occlusion of the inner gas conduit 707, first jacket channel 774, and second jacket channel 775 when the supply tube 706 is bent or flexed. In some implementations, one or more gas temperature sensors (not shown) are positioned at the inlet to the supply tube 706 (near the supply connector 768), at the distal end of the supply tube 706, and / or at the patient connector 708. For example, the temperature and humidity sensor may be positioned at the end of the supply tube 706. The gas temperature sensor(s) may have a wireless link to a controller at the base unit for temperature data transmission without an electrical conductor running along the supply tube 706. The breathing gas temperature at these points may be transmitted to a controller to control the VTC 716 or the ventilator for feedback control of the breathing gas temperature. In implementations, one or more liquid temperature sensors (not shown) are positioned along the supply tube 706 for monitoring the liquid temperature in the jacket.An ambient temperature sensor or ambient humidity sensor (e.g., at the air intake of the base unit) may be employed to allow environmentally conditioned control of the breathing gas along its flow path. Figures 7E and 7F show different cross-sections of a minor portion of auxiliary unit 704, in accordance with an illustrative implementation. In Figure 7E, supply tube 706 is connected to auxiliary unit 704 at auxiliary outlet 772, and a cross-section of supply tube 706 is shown. The first jacket channel 774 includes four sub-channels 774a, 774b, 774c and 774d. The second jacket channel 775 includes four sub-channels 775a, 775b, 775c and 775d. The plurality of sub-channels surround the inner gas conduit 707. The first jacket channel 774 and the second jacket channel 775 are divided into subchannels 774a to 774d and 775a to 775d by a plurality of radial ribs. Each radial rib extends from an inner wall defining the inner gas passage 707 to an outer wall of the delivery tube 706, wherein the annular space between the inner wall and the outer wall defines the jacket. Each pair of radial ribs defines a subchannel of the jacket through which liquid flows. The radial ribs allow the delivery tube 706 to be bent in any direction without kinking by preventing the inner breathing gas passage 707 from collapsing when the delivery tube 706 is bent.In some implementations, under flexing of the delivery tube 706, one or more of the subchannels 774a to 774d and 775a to 775d may collapse or become occluded, but at least some of the subchannels 774a to 774d and 775a to 775d and the inner gas passage 707 remain open to allow breathable liquid and gas to flow, respectively. The jacket having radial ribs may mimic a thick-walled tube to prevent collapse of the inner gas conduit 707. In some implementations, the inner wall defining the inner gas conduit 707 has a thickness proportional to an inner diameter of the inner gas conduit 707. In some implementations, the outer wall, defining the jacket, has a thickness proportional to the overall diameter of the delivery tube 706 minus the inner diameter of the inner gas conduit 707. In some implementations, each radial rib has a width proportional to the inner wall thickness. In Figure 7F, a cross-section of auxiliary unit 704 shows supply tube 706 disposed in supply connector 768. Subchannels 774a, 774b, 774c and 774d of first jacket channel 774 of supply tube 706 are in fluid communication with connector liquid outlet 770 of supply connector 768. Subchannels 775a, 775b, 775c and 775d of second jacket channel 775 of supply tube 706 are in fluid communication with connector liquid inlet 771 of supply connector 768. A tab 776 is disposed on top of heating plate 727. As described above, the first jacket channel 774 is in fluid communication with the connector liquid outlet 770 in order to receive liquid from the pump outlet 746. The liquid is flowed or pumped through the subchannels 774a to 774d and then through the subchannels 775a to 775d of the second jacket channel 775. The inner gas conduit 707 is in fluid communication with the connector gas outlet 769 to receive the breathable gas from the second VTC cap 765. The tab 776 is disposed on top of the heating plate 727, proximate the inner reservoir 732. In some implementations, the tab 776 is disposed on top of the heating plate 727 such that, when the liquid in the inner reservoir 732 reaches a sufficiently low level, the tab 776 is exposed while the remainder of the heating plate 727 remains submerged in the liquid. When the auxiliary unit 704 is fully seated in the base unit, a temperature sensor (such as temperature sensor 542 of FIG. 5 ) may be positioned such that it aligns with the tab 776 and can measure the temperature of the tab 776. When the tab 776 is not submerged in the liquid, it will heat up rapidly if the heating plate and heating element are in operation.The tongue temperature may be monitored by sending one or more signals indicating the tongue temperature to the controller. When the tongue heats rapidly during a low liquid level state of the auxiliary unit 704, the temperature sensor may detect the rapid increase in temperature and alert the controller. In response to detecting a rapid increase in tongue temperature indicative of a low liquid level, the controller may be configured to turn off the heat actuator (e.g., an induction coil). In response to detecting a rapid increase in tongue temperature indicative of a low liquid level, the controller may be configured to increase or open the flow of liquid from the external reservoir by, for example, actuating the occlusion valve 752 from the extended position to the mid-position to allow liquid flow to refill the inner reservoir 732.In response to detecting a rapid increase in reed temperature indicative of a low fluid level, the controller may be configured to completely shut off the respiratory therapy system. In some implementations, the base unit includes a spring element that can be actuated by the controller to automatically eject the auxiliary unit 704 under certain conditions, for example, when a rapid temperature increase is indicated. In Figure 7D, valve 752 is shown separated from corresponding components in the base unit. Actuation of valve 752 is performed by the controller of the base unit. Accordingly, Figures 8A and 8B show system 800 in which valve 852, which may be analogous to valve 752 of Figure 7D, is in a coupled state when auxiliary unit 804 is seated in depression 818 of base unit 802. Figure 8A shows a cross-section of system 800 which includes an auxiliary unit 804 seated in the base unit 802, according to an illustrative implementation. Valve 852 allows simultaneous control of respirable gas from gas path 813 of base unit 802 to gas path 812 of auxiliary unit 804 and liquid from tube connector 862 to inner tube 815. Respirable gas is provided to gas path 813 from a ventilator (not shown) via ventilator tube 878. Valve 852 includes a rod 854 having a variable position controlled by actuator 882. Valve 852 also includes a gas path valve seat 855 and a liquid path valve seal 857 attached to flexible portion 856. A gas seal 860 defines an annular space around gas path valve seal 855. A rod 854 extends through a bellows 880.The liquid flowing from the tube connector 862 flows to the valve 852 from the valve liquid inlet 858. The actuator 882 is coupled to a controller (not shown) on the base unit 802. The actuator 882 may be configured to move the rod 854 in a linear direction, for example, by pushing against a lower end of the rod 854. In some implementations, the rod 854 is not fixed to the actuator 882. For example, the rod 854 may be fixed to an inner surface of the bellows 880, and the actuator 854 is configured to push against an outer surface of the bellows 880, which is flexible, to move the rod 854. The controller may send one or more signals to the actuator 882 in order to adjust the position of the rod 854.The gas path valve seal 855 is coupled to one end of a rod 854 such that linear movement of the rod 854 would also move the gas path valve seal 855 in a linear direction, allowing the gas path valve seal 855 to be positioned in a plurality of positions along the linear direction. The gas path valve seal 855, as shown in FIG. 8, is in a retracted position which blocks breathable gas from flowing from the gas path 813 into the annular space defined by the gas seal 860 in the valve 852. The rod 854 is secured to the bellows 880 such that the bellows 880 expands and contracts as the rod 854 is lowered and raised, respectively, by virtue of the flexibility of the bellows 880. Since both the position of the gas path valve seal 855 and the volume of the bellows 880 can be varied, the flow rate of respirable gas from the gas path 813 can be controlled by adjusting the position of the gas path valve seal 855 and the volume of the bellows 880 by the actuator 854. From the retracted position of the gas path valve seal 855, as shown in Figure 8A, the actuator 854 can be configured to raise the gas path valve seal 855 to a mid-position to open a gap below the gas path valve seal 855 and allow respirable gas to flow toward the valve 852. The actuator 854 can be configured to further raise the gas path valve seal 855 to an extended position to enlarge the gap below the gas path valve 855 and increase the flow rate of respirable gas toward the valve 852. The flexible portion 856 may similarly have a variable position by virtue of its flexibility. The flexible portion 856 and the liquid path valve seal 857 may move in a linear direction. The liquid path valve seal 857 may be integrally formed in the flexible portion 856 or disposed in the flexible portion 856. The liquid path valve seal 857 may be rigid relative to the flexible portion 856, for example, by having a greater thickness than the portion 856 or having a reinforced structure. The gas path valve seal 855 may be lifted by the actuator 854 from its position indicated in Figure 8A such that the gas path valve seal 855 abuts the liquid path valve seal 857.Accordingly, controlling the actuator 854 may allow adjustment of the position of the liquid path valve seal 857 by urging it against the gas path valve seal 855. Adjusting the position of the liquid path valve seal 857 either narrows or widens a gap between the liquid inlet 858 and the liquid path valve seal 857, wherein liquid flows from the external tube connected to the tube connector 862 through the gap as it enters the valve 852 on its path in the auxiliary unit 804. Narrowing and widening the gap may decrease and increase, respectively, the flow rate of liquid out of the liquid inlet 858. Accordingly, valve 852 may provide simultaneous control of both respirable gas and liquid flow rates into auxiliary unit 804, similar to valve 652 of FIG. 6. In some implementations, linear actuation of actuator 854 allows for non-discrete positioning of valve seals 855 and 857. In some implementations, the controller is configured to control actuator 854 between a discrete set of positions. In some implementations, the set includes a variety of positions >1, >2, >5, >10, or >20. In some implementations, three distinct positions of valve 852 are listed: (1) a retracted position (shown in FIG. 8A ), wherein gas path valve seal 855 is fully lowered and liquid path valve seal 857 is not abutting such that gas path 813 is fully occluded,and the liquid inlet 858 is fully open to allow liquid flow to the inner tube 815; (2) a middle position, wherein the gas path valve seal 855 is partially raised to allow breathable gas flow from the gas path 813, and the liquid path valve 857 is not abutting to allow liquid flow from the liquid inlet 858 to the inner tube 815; and (3) an extended position, wherein the gas path valve seal 855 is fully extended to allow breathable gas to flow from the gas path 813 and abut the liquid path valve 857 such that it occludes the liquid inlet 858, blocking the flow of liquid. These three positions are summarized in Table 3 above. The three positions described above may be used for certain purposes. For example, the middle position is used to refill an interior reservoir of auxiliary unit 804 while supplying breathing gas. The reservoir may be the interior reservoirs 532 and 732 of Figures 5, 7C, 7D, and 7F. The extended position may be used to isolate the interior reservoir to prevent overfilling or when the system 800 is in a standby or low power mode, as described herein. For example, the standby mode may involve only providing breathing gas without vaporizing liquid into the breathing gas through a VTC. The standby mode may be initiated by the controller when a main battery of base unit 802 is removed and the system 800 operates on power from a backup battery in the base unit 802. The retracted position may be used when the auxiliary unit 804 is removed or separated from the base unit 802.In this circumstance, the retracted position may be advantageous in order to protect the gas path 813 of the base unit 802 from ingress (e.g., from liquid, dust, particles, contaminants, cleaning solvents), so that the fan and fan tube 878 are not contaminated. The controller may be configured to operate the actuator 854 to alternate between the valve positions based on the received signals. In some implementations, the auxiliary unit 804 further comprises an inner reservoir (such as inner reservoirs 532 and 732 of Figures 5, 7C, 7D and 7F) for holding liquid and a level sensor (such as level sensor 538 of Figure 5) configured to measure the liquid level in the inner reservoir. The level sensor may transmit a signal to the controller indicating that the liquid level is substantially low, and the controller may respond to the signal by actuating the valve 852 from the extended position to the mid-position, allowing liquid flow to the inner tube 815.A low liquid level may also be indicated to the controller by a temperature sensor (such as temperature sensor 542 of FIG. 5) that measures the temperature of a heating plate immersed in liquid in the auxiliary unit 804, such that a low liquid level is indicated by a rapid increase in heating temperature when at least a portion of the heating plate is no longer immersed in liquid, for example, when the tab 776 of the heating plate 727 of FIG. 7 is exposed. In response to one or more signals from the temperature sensor, the controller may actuate the valve 852 from the extended position to the mid-position to allow liquid flow in the inner tube 815 to refill the inner reservoir and re-immerse the heating plate.In some implementations, the auxiliary unit 804 comprises an alignment marker (such as alignment marker 548 of Figure 5), and the base unit 802 includes an alignment sensor (such as alignment sensor 549 of Figure 5) configured to detect the presence of the alignment marker when the auxiliary unit 804 is fully seated in the base unit 802. The alignment sensor may transmit a first signal to the controller indicating that the presence of the alignment marker has been detected, indicating that the auxiliary unit 804 is fully seated, and the controller may respond to the first signal by actuating the valve 852 from the retracted position to the mid position, allowing flow of breathable gas and liquid into the gas path 812 and inner tube 815, respectively, of the auxiliary unit 804.The controller may alternatively respond to the first signal by actuating the valve 852 from the retracted position to the extended position, for example, if the internal reservoir is full of liquid. The alignment sensor may transmit a second signal to the controller indicating that it no longer detects the presence of the alignment marker, indicating that the auxiliary unit 804 has been disengaged or dislodged, and the controller may respond to the second signal by actuating the valve 852 from the extended or mid-position to the retracted position. The flexible portion 856 separates the liquid flow path from the breathable gas flow path, and its flexibility allows control of the liquid flow rate from the breathable gas side of the flexible portion 856. The flexible portion 856 may be constructed from a material that is substantially flexible to allow upward force of the gas path valve seal 855 to vary the position of the flexible portion 856 and the liquid path valve seal 857. Suitable materials may include ethylene vinyl acetate, polyethylene, polyethylene-based polyolefin elastomers, polypropylene, polyurethane, styrene butadiene copolymer, thermoplastic polyester elastomer, polypropylene-based elastomers, thermoplastic polyurethane elastomer, polyvinylidene fluoride, fluorinated ethylene propylene, nylon, nylon blends, polystyrene, polyvinyl chloride, polytetrafluoroethylene, and thermoplastic vulcanizate.In some implementations, the gas seal 860 is formed of a flexible material such that it may be compressed when the auxiliary unit 804 is seated in the base unit 802 to form a sealed annular space between the gas paths 813 and 812, as shown in Figure 8A where the gas seal 860 forms an annular space around the gas path valve seal 855. The gas seal 860 may be formed of the same material as the flexible portion 856 or any of the materials listed above. Figure 8B shows another angle of system 800, showing a cross-section of auxiliary unit 704, which includes a VTC 816 and an inner reservoir 832, according to an illustrative implementation. The auxiliary unit 804 is fully seated in depression 818 of base unit 802. The VTC 816 includes a cap 864 which directs breathable gas from gas path 812 to a plurality of fibers 884. The inner reservoir 832 stores liquid in the auxiliary unit 804. The inner tube 815 directs liquid from the valve 852 to the inner reservoir 832. The liquid is transported to the VTC 816 where the liquid can vaporize into the breathing gas directed through the lid 864. For example, the liquid can be water, which is vaporized to create a humidified breathing gas. The VTC 816 contains the plurality of fibers 884, which allow vapor to pass from the liquid flow into the breathing gas flow. The fibers can be permeable or semi-permeable in order to only allow vapor to pass through and keep the liquid separate from the breathing gas. Liquid that does not vaporize in the VTC 816 can flow out a liquid outlet of the VTC, which returns the liquid to the inner reservoir 832. The liquid in the auxiliary unit 804 transported to VTC 816 must be heated to or near a boiling point temperature of the liquid in order for at least a portion of the liquid to vaporize. Figure 9 shows a heating section of an auxiliary unit 904, the heating section including a heating plate 927 configured to be submerged in liquid and heat the surrounding liquid, according to an illustrative implementation. The liquid is stored in an inner reservoir 932, to which liquid is supplied from an outer reservoir via reservoir inlet 934. The heating plate 927 includes a protruding tab 976. In accordance with the previously described implementations, the auxiliary unit 904 may be seated in a base unit to form a respiratory therapy system. The heating plate 927 may be configured to couple to a heating element in the base unit when an auxiliary unit 904 is seated. In some implementations, the heating element produces a current in the heating plate 927 via induction. Induction heating allows for focused heating of the heating plate 927 without contact between the heating element and the heating plate 927. The heating element may be a coil. Alternating electrical current, supplied from a power supply of the base unit, may be passed through the coil, creating a varying magnetic field. The coil is formed of a conductive material, such as copper or silver.In this implementation, the heating plate 927 is formed of a conductive material. When the auxiliary 904 is seated, the heating plate 927 is positioned in the magnetic field, which induces eddy currents in the heating plate 927. The induced eddy currents flow against an electrical resistivity of the heating plate 927, generating localized heat in the heating plate 927 without any contact between the heating plate 927 and the coil. Additional heat may be produced in the heating plate 927 in implementations where the heating plate 927 is formed of a magnetic material. The additional heat is produced via hysteresis, which involves internal friction created when the magnetic heating plate 927 is within the magnetic field of the coil, the internal friction producing the additional heat.Suitable materials for the 927 heating plate include, but are not limited to, steel, iron, copper, aluminum, lead, silver, tin, and alloys of the foregoing. The tab 976 is disposed on top of the heating plate 927, proximate the inner reservoir 932. In some implementations, the tab 976 is disposed on top of the heating plate 927 such that, when the liquid in the inner reservoir 932 reaches a sufficiently low level, the tab 976 is exposed while the remainder of the heating plate 927 remains submerged in the liquid. When the auxiliary unit 904 is fully seated in the base unit, a temperature sensor (such as temperature sensor 542 of FIG. 5 ) may be positioned such that it aligns with the tab 976 and can measure the temperature of the tab 976. When the tab 976 is not submerged in the liquid, it will heat up rapidly if the heating plate and heating element are in operation.The tongue temperature may be monitored by sending one or more signals indicating the tongue temperature to the controller. When the tongue heats rapidly during a low liquid level state of the auxiliary unit 904, the temperature sensor may detect the rapid increase in temperature and alert the controller. In response to detecting a rapid increase in tongue temperature indicative of a low liquid level, the controller may be configured to turn off the heat actuator (e.g., an induction coil). In response to detecting a rapid increase in tongue temperature indicative of a low liquid level, the controller may be configured to increase or open the flow of liquid from the external reservoir by, for example, actuating the occlusion valve 952 from the extended position to the mid-position to allow the flow of liquid to refill the inner reservoir 932.In response to detecting a rapid increase in reed temperature indicative of a low fluid level, the controller may be configured to completely shut off the respiratory therapy system. In some implementations, the base unit includes a spring element that can be actuated by the controller to automatically eject the auxiliary unit 904 under certain conditions, for example, when a rapid temperature increase is indicated. Measurement and supplementation of breathing gas It may be advantageous to measure, monitor, and manipulate the flow of respirable gas in a base unit described herein. Figure 10 shows a measurement device 1086 of a base unit 1002, in accordance with an illustrative implementation. The measurement device 1086 is in fluid communication with a gas inlet 1088 and a fan 1003 of the base unit 1002. The measurement device 1086 includes a conduit 1090, a first flow sensor 1092, and first segment 1093, a second flow sensor 1094, and a second flow segment 1095. The metering device 1086 may be implemented in any of the base units described herein, including base units 402, 502, 602, and 802 of Figures 4, 5, 6, 8A, and 8B. The gas inlet 1088 allows breathable gas to enter the base unit 1002 from an external source. In some implementations, the gas inlet 1088 draws ambient air from the surroundings. In some implementations, the gas inlet 1088 is configured to be coupled to a wall air outlet. The gas inlet 1088 is in fluid communication with the fan 1003 via duct 1090. In some implementations, the fan 1003 generates a suction pressure that draws gas into the gas inlet 1088 and through the duct 1090. Gas inlet 1088 directs respirable gas into conduit 1090. First flow sensor 1092 and second flow sensor 1094 are disposed along conduit 1090 and are configured to measure a flow rate of respirable gas traveling through conduit 1090. First flow sensor 1092 and second flow sensor 1094 may be configured to output one or more signals to a controller in base unit 1002, the signals being indicative of the measured flow rates. The controller is operatively coupled to ventilator 1003 and may be configured to adjust one or more parameters of ventilator 1003 based on the received signals indicative of the measured flow rates. Suitable parameters to be adjusted include suction pressure, outlet pressure, and outlet flow rate. The fan 1003 may exhaust breathing gas at a high temperature, such that a heat exchanger may be provided at the outlet of the fan 1003. The heat exchanger may be wrapped around a tube such that heat is dispersed from the breathing gas radially outward toward the breathing gas heat exchanger. The heat exchanger may be configured to lower the breathing gas temperature to a target temperature, e.g., a maximum temperature that prevents malfunction of certain components that come into contact with the breathing gas. For example, a VTC may contain fibers that would be damaged by excessively hot breathing gas. Temperature sensors may be positioned along the flow path before and after the heat exchanger to ensure that it is not too hot before entering other components, such as the VTC.Measurements from the sensors may be used to adjust the operation of fan 1003 (e.g., by limiting the RPM of fan 1003 or turning it off) or to adjust the operation of the heat exchanger (e.g., by adjusting the flow rate of coolant through the heat exchanger or temperature of the coolant). In some implementations, the heat exchanger is an air-to-air heat exchanger with an extrusion of metal fins having an inner path for breathing gas flow and an outer path for cooling air flow. The resulting exchange of thermal energy between the hot breathing gas and the cooling air flow results in a cooled breathing gas flow. In some implementations, the heat exchanger comprises a countercurrent portion and a concurrent portion. In the countercurrent portion, the hot breathing gas flows through the inner path in a direction opposite to a direction in which the cooling air flows through the outer path.In the concurrent portion, the cooler breathing gas flows through the inner path in a direction parallel to the cooling air flow through the outer path, further cooling the breathing gas. The cooling air may be transported through the outer path by a heat exchanger fan. This configuration results in a more compact heat exchanger footprint, with both the breathing gas inlet and outlet on one side. The heat exchanger can have efficiency between 80 and 90%. For example, the heat exchanger efficiency is 88%. In some implementations, the system comprises a gas temperature sensor for monitoring the temperature of the breathing gas at some point in the system. For example, if the system 100 comprises a humidifier as discussed above, then a gas temperature sensor may be positioned at the inlet of the humidifier such that the temperature of the gas entering the humidifier may be monitored. Since a fan is used to move cooling air in the heat exchanger, the fan may be controlled to adjust the rate of thermal energy transfer and regulate the temperature of the breathing gas outlet to the humidifier. When the temperature of the breathing gas at the humidifier inlet is known, the fan may be lowered or even turned off when the temperature is low enough to not damage the fiber. Similarly, the fan may be adjusted.Minimizing fan usage is advantageous as it reduces system noise generation. In some implementations, the first flow sensor 1092 and the second flow sensor 1094 are mass flow sensors configured to output one or more signals indicative of measured mass flow rates of the breathable gas. The conduit 1090 further includes the first segment 1093 and the second segment 1095. The first segment 1093 is disposed adjacent the first flow sensor 1092, and the second segment 1095 is disposed adjacent the second flow sensor 1094. These components are positioned such that breathable gas flowing through the conduit 1090 flows through, in order from first to last, the first segment 1093, the first flow sensor 1092, the second segment 1095, and the second flow sensor 1094. In some implementations, the first segment 1093 and the second segment 1095 may be configured to be approximately straight.By straightening the first and second segments 1093 and 1095, the breathing gas flows entering the first flow sensor 1092 and second flow sensor 1094 are minimized from flow disturbances such that the flow profiles are approximately uniform. For example, the first and second flow sensors 1092 and 1094 may provide the most precise and accurate breathing gas flow rate measurements when the breathing gas flow profiles entering each sensor are approximately uniform. In some implementations, the conduit 1090 also includes straight segments directly downstream of the first and second flow sensors 1092 and 1094 to minimize the downstream effects of flow on the measurements. However, it should be understood that the segments 1093 and 1095 are optional and are not required for accurate flow measurement. In some implementations, the first flow sensor 1092 and the second flow sensor 1094 are configured to be calibrated relative to each other. When no supplemental gas is being introduced into the gas flow, the flow rate through the first and second flow sensors is identical. The first and second sensors may indicate different flow rates, however, due to manufacturing variability, drift over time, or other factors that introduce error to flow sensors. By using the first sensor as a reference point and offsetting the indicated flow of the second sensor, the difference between the sensors can be reduced to zero. When supplemental gas is introduced, the supplemental gas flow rate is calculated as the difference between the indicated flow at the first and second flow sensors. The error in the calculation is thereby reduced to the error of the second sensor. Figure 11 shows a metering device 1186 of a base unit 1102, according to an illustrative implementation. The metering device 1186 includes a conduit 1190 coupled to a gas inlet 1188 and a fan 1103. A first flow sensor 1192 and a second flow sensor 1194 are disposed along the conduit 1190. The conduit 1190 includes a first segment 1193 and a second segment 1195. A supplemental gas inlet 1196 is in fluid communication with the conduit 1190 via a supplemental valve 1197. The base unit 1102 includes a controller 1198 operatively coupled to the valve 1197. Base unit 1102 can use the same components of base unit 1102 in figure 10, but further includes the functionality of introducing a supplemental gas into the conduit 1190. Suitable supplemental gases include, but are not limited to, oxygen, oxygen-concentrated respirable gas, helium, nitric oxide, heliox, anesthetic gas, and gas including aerosolized medicament. The supplemental gas inlet 1196 provides the supplemental gas from an external source, such as a wall gas outlet, a gas concentrator, or a gas tank. The controller 1198 is configured to actuate the supplemental valve 1197 to control the flow rate of the supplemental gas entering the conduit 1190. The supplemental valve 1197 may be, for example, a solenoid valve, a globe valve, or a diaphragm valve. The supplemental gas inlet 1196 may provide oxygen or another breathable gas. As illustrated in Figure 11, the supplemental gas may be inserted into the conduit 1190 and mixed with the breathable gas from the gas inlet 1188 before the mixed gases pass through the ventilator 1103. Because some oxygen sources, such as oxygen concentrators, have a limited pressure output and are designed to deliver at a low flow rate, such sources may not be able to overcome the back pressure of a high velocity flow if the supplemental gas inlet 1196 is positioned after the ventilator 1103 in the system. The supplemental valve 1197 may be a valve with a low pressure drop or minimal pressure loss (e.g., dual disc check valve, butterfly valve, ball valve, diaphragm valve), such that the limited pressure output of the oxygen / supplemental gas source is maintained. The ventilator 1103 may generate a high pressure which accelerates the flow of mixed gases together when oxygen is introduced into the flow before the ventilator 1103. The ventilator 1103 may have an oxygen classification, including appropriate cleaning of surfaces to ensure that there is no oil, anodized parts, use of silicone-based oils, and oxygen cleaning of parts. Alternatively, in some implementations, the supplemental gas inlet 1196 and second flow sensor 1194 are positioned after the breathing gas enters the ventilator 1193, such that oxygen or other supplemental gas does not enter the ventilator 1193. Upon entering conduit 1190, the supplemental gas may mix with the breathing gas in conduit 1190 originating from gas inlet 1188. In some implementations, metering device 1086 is configured such that the breathing gas and supplemental gas are completely or uniformly mixed before flowing to second flow sensor 1194. Second segment 1195 may be of sufficient length to allow for uniform mixing of the breathing and supplemental gases. The supplemental gas inlet 1196 and supplemental valve 1197 are positioned to introduce supplemental gas into the conduit 1190 at a point between the first flow sensor 1192 and the second segment 1195. In some implementations, the first flow sensor 1192 measures the flow rate of breathing gas, and the second flow sensor 1194 measures the flow rate of a mixed flow of breathing gas and supplemental gas. Both the first flow sensor 1192 and the second flow sensor 1194 are configured to send to the controller 1198 signals including a first measurement and a second measurement indicative of the measurements of the breathing gas and the mixed flow, respectively. Upon receiving the signals, the controller 1198 may be configured to calculate a difference between the first measurement and the second measurement. The calculated difference is indicative of the flow rate of supplemental gas introduced via supplemental valve 1197.The controller 1198 may be configured to calculate one or more gas concentrations of one or more components in the mixed flow based on the second measurement and the calculated difference. For example, the supplemental gas may be pure oxygen, and the controller may calculate the oxygen concentration in the mixed flow based on the second measurement and the calculated difference, the calculated difference indicating the amount of oxygen added to the breathing gas over time. As mentioned above, the controller 1198 is configured to actuate the supplemental valve 1197 to control the flow rate of the supplemental gas entering the conduit 1190. The controller 1198 may be configured to adjust the flow rate of the supplemental gas by actuating the supplemental valve 1197 based on the calculated flow difference and / or the one or more calculated concentrations. For example, the controller 1198 may compare a calculated concentration to a target concentration, with the target concentration being stored in a memory (not shown) and / or received as an input. A user may enter the target concentration via an interface, such as a computer link or a display such as display 430 of FIG.In this example, the controller 1198 may, upon determining that the calculated concentration is greater than or less than the target concentration, actuate the supplemental valve 1197 to decrease or increase, respectively, the supplemental gas flow rate, or vice versa. The first flow sensor 1192 and the second flow sensor 1194 may be calibrated relative to one another, allowing the controller to detect small differences in flow rate between the first flow sensor 1192 and the second flow sensor 1194. For example, the calculated flow difference may be less than about 5% of the measurement from the first flow sensor 1192. The calculated flow difference may be less than about 1% of the measurement from the first flow sensor 1192. Calibrating the first flow sensor 1192 and the second flow sensor 1194 relative to one another may reduce an error associated with the flow difference calculation to an error associated with the measurement by the second flow sensor 1184.The controller 1198 may be configured to pause or cease the flow of supplemental gas through the supplemental valve 1197, for example, to calibrate the first flow sensor 1192 and the second flow sensor 1194 relative to each other while there is no flow of supplemental gas. In some implementations, the conduit 1190 is coupled to one or more additional supplemental gas inlets (not shown) configured to introduce one or more additional supplemental gases. There may be an additional flow sensor (not shown) for each additional supplemental gas inlet. These additional flow sensors and additional supplemental gas inlets may alternate in order along the conduit 1190 such that the controller 1198 may calculate the flow rate of each additional supplemental gas added to the breathing gas stream through the conduit 1190 based on the prior methods. The supplemental gas inlet 1196 may include a pressure sensor configured to measure the pressure of the incoming supplemental gas. The measured pressure value may be transmitted to the controller. 1190. Using the measured pressure value, the controller 1190 may determine what type of external source is supplying the supplemental gas. For example, oxygen is supplied at a high pressure, and the controller 1190 determines that it is from a wall outlet, while a relatively low pressure may indicate that the oxygen is supplied from an oxygen concentrator. Each type of source may supply oxygen at different levels (e.g., 100% oxygen from a wall outlet or approximately 93% oxygen from an oxygen concentrator), such that the calculation of flow rate and oxygen concentration in the breathing gas may take into account the determined incoming oxygen concentration from the source. The controller 1190 may include software, hardware, and / or logic to allow closed-loop control of one or more of a respirable gas flow rate, a mixed-flow flow rate, a concentration of a mixed-flow component, temperature, and / or humidity to be enabled based on data received by the controller 1190 from one or more sensors coupled to the controller 1190. Additionally or alternatively, the closed-loop control may be based on data received from one or more external devices, for example, a pulse oximeter or a transcutaneous carbon dioxide sensor. External Monitoring In another aspect of the present disclosure, one or more external monitoring devices may be coupled to a base unit via one or more corresponding interfaces or ports. For example, a pulse oximeter and / or a transcutaneous carbon dioxide sensor may be coupled to a base unit to provide real-time feedback of the patient's oxygen and carbon dioxide, respectively. The use of external monitoring devices in combination with the controller to provide closed-loop feedback or adaptive control to the system is also described in U.S. patent application no. 16 / 722,722, filed December 20, 2019, and entitled “OXYGEN MIXING AND DELIVERY”; U.S. application no. 16 / 008,508 (now U.S. patent no. 10,514,662), filed June 8, 2018, and entitled “OXYGEN MIXING AND DELIVERY”; and U.S. patent application no. 14 / 602,392 (now U.S. Patent No.10,007,238), filed on January 22, 2015, and entitled “OXYGEN MIXING AND DELIVERY”, the entire contents of which are incorporated herein by reference. Figure 12 shows a metering device 1286 configured to receive breathing gas from gas inlet 1288 and supplemental gas from supplemental gas inlet 1296 via supplemental valve 1297, in accordance with an illustrative implementation. The metering device 1286 includes a conduit 1290 coupled to a gas inlet 1288 and a fan 1203. A first flow sensor 1192 and a second flow sensor 1194 are disposed along the conduit 1290. The conduit 1290 includes a first segment 1293 and a second segment 1295. A supplemental gas inlet 1296 is in fluid communication with the conduit 1290 via a supplemental valve 1297. The base unit 1202 includes a controller 1298 operatively coupled to the valve 1297. The controller 1298 includes a mixing controller 1299, a proportional module 1298a, an integral module 1298b, a derivative module 1298c, an error module 1298d, and an output module 1298e.The mixing controller 1299 is coupled to the supplemental valve 1297 and a pulse oximeter 1287. ! 705*0 / 1 / 7707 / 3 / YILI The gas inlet 1288, the conduit 1290, the first flow sensor 1292, the second flow sensor 1294, the first segment 1293, the second segment 1295, and the blower 1203 may be the same as the corresponding components in Figures 10 and 11. Like the metering device 1186 of Figure 11, the metering device 1286 allows for the introduction of supplemental gas from the supplemental gas inlet 1296 via the supplemental valve 1297 which is operatively coupled to the controller 1298. In this implementation, the pulse oximeter 1287 is configured to send data indicative of a percentage of oxygen saturation (SpOa) of the patient's blood to the controller 1298. “SpO2” is an acronym for “peripheral oxygen saturation,” and within related technology, the term SpO2 is often casually referred to as “blood oxygen,” “blood oxygen saturation,” and other similar terms.Some implementations herein use SpO2 as an estimate of blood oxygen concentration and are typically measured with a pulse oximeter. A pulse oximeter is generally a photoelectric device that measures the amount of saturated hemoglobin in tissue capillaries by transmitting light beams through the tissue to a light receiver. A pulse oximeter is generally configured to clip onto a fingertip or earlobe. The amount of saturated hemoglobin affects the wavelength and reflection or transmission of light transmitted through the tissue. By analyzing the received light, SpO2 can be derived. Pulse oximeters may also allow measurement of a pulse rate and generate various alarm condition signals. Although photoelectric pulse oximeters have been described here, it will be understood that other types of pulse oximeters may be substituted for the pulse oximeter 1287. In some implementations, the controller 1298 is configured to actuate the mixing valve 1297 via the mixing controller 1299 based on data from the pulse oximeter 1287. The controller 1298 may also receive an SpO2 as an input, for example, via a computer interface or a display, such as a display 430 of Figure 4 which allows for user interaction. A target SpO2 may also be stored in a memory (not shown). The controller 1298 may be configured to compare a measured SpO2 from the pulse oximeter 1287 to the target SpO2 and determine an appropriate change in supplemental gas flow rate. For example, the comparison may reveal that the measured SpO2 is below the target SpO2, and the controller may calculate the target supplemental gas flow rate that would raise the patient's SpO2 to the target SpO2.The supplemental gas target flow rate may be implemented by actuating valve 1297 and calculating a difference in flow rate between a first flow measurement from the first flow sensor 1292 and a second flow measurement from the second flow sensor 1294, due to supplemental gas being introduced between the first and second flow sensors 1292 and 1294. Controller 1298 may then adjust valve 1297 if the calculated flow rate difference is different from the supplemental gas target flow rate. The controller 1298 may be configured to adjust the flow rate of supplemental gas through the valve 1297 to adjust an oxygen concentration in the mixed flow to a minimum oxygen concentration that is determined to have a therapeutic effect on the patient based on data received from the pulse oximeter 1287. This capability may be especially advantageous when the supplemental gas is supplied from an external tank having limited capacity. The controller 1298 may minimize the amount of supplemental gas needed in order to maximize the life of the external tank, providing effective respiratory therapy to a patient for as long as possible given the restriction. The controller 1298 may generate for the display one or more graphs indicative of SpO2, PaO2, or F¡O2. The controller 1298 includes various components that enable proportional integral derivative (PID) control of the breathing gas and the supplemental gas. The PID controller 1298 enables feedback-based control of various system parameters, such as the breathing gas flow rate, supplemental gas flow rate, and pump flow rate. Similar configurations are described in U.S. Patent Application No. 16 / 722,722, filed December 20, 2019, and entitled “OXYGEN MIXING AND DELIVERY”; U.S. Application No. 16 / 008,508 (now U.S. Patent No. 10,514,662), filed June 8, 2018, and entitled “OXYGEN MIXING AND DELIVERY”; and U.S. Patent Application No. 14 / 602,392 (now U.S. Patent No. 10,007,238), filed January 22, 2015, entitled “OXYGEN MIXING AND DELIVERY.” The entire contents of the aforementioned applications are incorporated herein by reference.A PID controller is a feedback loop controller. A PID controller calculates an error value as the difference between a measured process variable and a desired process variable value (or setpoint). The controller operates to minimize the difference between the measured value and the setpoint. A PID controller achieves this by using an algorithm that uses three separate parameters: proportional (P), integral (I), and derivative (D) values ​​interpreted in discrete time increments, where P depends on the current error, I depends on the accumulation of past errors, and D predicts future errors. The weighted sum of these three actions is used to adjust a process, in this case the oxygen ratio represented by F¡O2. Mathematically, these values ​​are generally represented by the following equations: P = KpeU) = K, I β(τ)άτ / q de(t) υ = κά—— dt where a mixing control signal is derived from the PID control output ut: flde(l) uc= P + I + D = Kpe(l) + K¿ I e(r)dT + Kd—-— and where: Kp: proportional gain coefficient: Kt: integral gain coefficient; Κύ: derivative gain coefficient; e: error, difference between measurement and target; t: time; yt: integration variable, takes values ​​from time = 0 to the present time. Eq. 1 Eq. 2 Eq. 3 Eq. 4 For the purposes of this document, a controller may be referred to as a PID controller for convenience and by way of example, but in practice the controller may not actually use all three control elements of proportional, integral, and derivative. The use of only one or two of the PID control functions is common, and the use of other feedback control mechanisms is also within the scope of the present teachings. For example, in other example implementations, a P1I (proportional-integral) controller or other suitable feedback controller could alternatively be used. In this regard, controller 1298 includes modules for each PID control parameter. Module 1298a uses Eq. 1 for proportional control, module 1298b uses Eq. 2 for integral control, and module 1298c uses Eq. 3 for derivative control. The current PaO2 value (representing the measured SpO2 from pulse oximeter 1287) is received by mixing controller 1299 and subtracted from the set point (i.e., the blank value) in error module 1298d to produce error signal e at the output of error module 1298d. This error signal e is then processed by P, I, and D modules 1298a, 1298b, and 1298c, respectively, according to equations 1-3 above. The outputs of modules 1298a, 1298b and 1298c are summed in output module 1298e to produce output utla which is provided to mixing controller 1299.The mixing controller 1299 processes the output into a format appropriate for effecting supplemental valve control 1297 to establish an appropriate mixture of breathing gas and supplemental gas dictated by the PID controller 1298. An example PID controller equation that can be used for this application is: Pa02=(KL * F¿02) + K2 Eq. 5 where KL is the lung function gain coefficient which relates to the lung’s ability to efficiently transfer oxygen and carbon dioxide. K2 is the offset which relates to a patient’s overall respiratory capacity level. The controller 1298 may use a relatively long sample period, e.g., about 10 seconds, which serves as a type of low-pass to ensure the accuracy of SpO2 calculated from the pulse oximeter 1287. Another type of low-pass filter may be provided by using, e.g., 90% of old data (from a previous sample period) and adding in, e.g., 10% of new data (from a new sample period). Both of these filters improve the controller performance so that it is more sensitive but not overly sensitive. The controller 1298 may also use a “start” value of O2 upon initiation of adaptive control.The initial value can be adjusted by a user or operator and is used by the 1298 controller to ensure that the system starts in a relatively steady state condition, for example, to avoid having PID control that adjusts the patient's O2 level up and down upon startup. To ensure that the system starts operation in a steady-state condition, the system can be initialized using an initial KL calculated by: KL, = (PaO2)i / (FíO2)¡Eq. 6 where KLt, (PaO^i, and (F¿O2)í are all initial values. Additionally, within each sample period, the controller 1298 may use an adaptive algorithm to form new PID gain coefficients. An example algorithm is: KLnew= 0.9 * KLold+ 0.1 * (PaO2 / FiO2) Eq. 7 where KLnew can be used to calculate new PID gain coefficients. The pulse oximeter 1287 measures SpO2; however, the controller 1298 may use PaO2 for its calculations. The term “PaO2” stands for partial pressure of arterial oxygen. Although, in other implementations, control signals may be derived more directly from SpO2 or other measures of a patient's blood oxygen concentration without limitation. The conversion of SpO2 to PaO2 may be effected in a variety of ways. In one example, the measured SpO2 is converted to the corresponding partial pressure of oxygen PaO2 by using an oxyhemoglobin dissociation curve based on the standard conditions of temperature equal to 37°C, pH equal to 7.4, and the Bohr effect not being present. The dissociation curve graphs PaO2 versus SpO2, allowing one to read the PaO2 value off the graph based on a known SpO2 value.Oxyhemoglobin dissociation curves may be shifted to the left by conditions that cause high O2 affinity and to the right by conditions that cause low O2 affinity. The curve generally approaches a sigmoidal shape, and various equations can be devised to closely model the shape of the curve using various curve fitting techniques. Using such equations, the PaO2 value can be calculated directly. Alternatively, data points from the dissociation curve can be cataloged in a look-up table stored in storage or memory (not shown) that can be used by the mixing controller 1299 to convert the SpO2 value to a PaO2 value. If the exact SpO2 value is not in the table, then linear or nonlinear interpolation (any suitable interpolation such as polynomial, piecewise, spline, bilinear, extrapolation, etc.) can be performed.) to approximate the corresponding PaO2 value. The more data points provided in the lookup table, the more accurate the interpolation will be, if necessary. An example workflow for adaptive control is as follows. The mixing controller 1298 receives pulse oximeter data from the pulse oximeter 1287. The pulse oximeter data includes SpO2 data and alarm condition signals. From the SpO2 data, the mixing controller 1299 determines PaO2 data for calculating an appropriate oxygen concentration of the mixed flow output to the patient. The PaO2 data may be determined by referring to a stored look-up table, using interpolation if necessary, where the look-up table may be derived from an oxyhemoglobin dissociation curve. The controller 1298 and its components 1298a to 1298e perform adaptive feedback control of the gas based on the SpO2 data by the mixing controller 1298 interfaced with the valve 1297. The adaptive feedback control is provided by the PID control scheme.The controller 1298 may receive the flow rate data or a flow rate signal indicating that the respirable gas delivered out of the conduit 1290 has been manually switched. This flow data may be received from a user interface, such as a display like display 430 of Figure 4, or from the first or second flow sensors 1292 and 1294. Upon receiving the flow rate data or flow rate signal, the controller 1298 may enter a manual override mode and stop adaptive feedback control (i.e., stop sending signals to the valve 1297). The controller 1298 may be configured to compare the measured SpO2 data to alarm limits and initiate an alarm condition if the measured SpO2 data is outside the alarm limits.An alarm condition may involve stopping the operation of base unit 1202 and / or generating an alert to display to the user (e.g., on a screen such as screen 430 of Figure 4). Another example workflow involves the mixing controller 1299 receiving pulse oximeter data from the pulse oximeter 1287. The pulse oximeter data includes one or more signals indicative of a patient's current blood oxygen level. The controller 1298 receives gas data indicative of measured respirable gas flow rates from the first flow sensor 1292 and the second flow sensor 1294. The measured respirable gas flow rates may be subtracted to determine an amount of supplemental gas added between the first and second flow sensors 1292 and 1294. The controller 1298 may calculate an oxygen concentration (percent oxygen) in the mixed flow (respirable gas and supplemental gas) based on the calculated amount added and the measured second respirable gas flow rate. The controller 1298 compares the one or more current blood oxygen level signals to a target blood oxygen level.The blank may be stored in a memory in the base unit 1202 or entered by a user via a user interface. The controller 1298 calculates an appropriate change to the mixed flow to achieve a change in the oxygen concentration in the mixed flow. The mixing controller 1299 actuates the valve 1297 to alter the oxygen concentration in the mixed flow (e.g., by increasing or decreasing the flow rate of supplemental gas, possibly containing oxygen in the supplemental gas). The mixing controller 1299 may receive new signals from the pulse oximeter 1287 indicative of a current blood oxygen level of the patient. In some implementations, a transcutaneous carbon dioxide sensor is coupled to the controller 1298 of the base unit 1202, and the transcutaneous carbon dioxide sensor is configured to send to the controller 1298 one or more signals indicative of PaCO2. Transcutaneous carbon dioxide sensors generally measure the skin surface partial pressure of carbon dioxide (PtcCO2) to provide an estimate of the arterial partial pressure of carbon dioxide (PaCO2). In some cases, the sensor also measures the partial pressure of oxygen (PtcO2) to estimate the arterial partial pressure of oxygen (PaO2). The controller 1298 may be configured for closed-loop control of patient carbon dioxide based on the received signals, using the methods previously described for closed-loop oxygen control. Using a sensor that measures both PtcCO2 and PtcO2, or using both a pulse oximeter and a transcutaneous carbon dioxide sensor, the controller 1298 may be configured to receive both oxygen and carbon dioxide data and determine an appropriate therapy for the patient based on the received data. For example, the controller 1298 may compare the measured oxygen data and the measured carbon dioxide data to a stored reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value. The controller 1298 may calculate differences between a current blood oxygen level and a reference oxygen level and between a current blood carbon dioxide level and a reference carbon dioxide level.The controller 1298 may be configured to determine whether to provide the patient with high oxygen therapy (e.g., to increase blood oxygen levels) or high washout therapy (e.g., to decrease blood carbon dioxide levels). For example, if the blood oxygen level difference is greater than the carbon dioxide level difference, the controller 1298 may select the high oxygen therapy, or if the blood carbon dioxide level difference is greater than the oxygen level difference, the controller 1298 may select the high washout therapy. Upon selecting the high oxygen therapy, the controller 1298 may direct the mixing controller 1299 to actuate the valve 1297 to increase the flow rate of supplemental gas in the conduit 1290, for example, in cases where the supplemental gas contains a higher concentration of oxygen than the breathing gas from the gas inlet 1288.By selecting high washout therapy, the controller 1298 may increase the flow rate of respirable gas through the gas inlet 1288 by, for example, increasing the suction pressure of the ventilator 1203. Providing high washout therapy may involve increasing an outlet pressure or outlet flow rate of the ventilator 1203. Use with aerosol medications The systems described herein, including systems 100, 400, 500, 600, and 800 of Figures 1, 4 through 6, 8A, and 8B, may comprise or may be configured to be connected to a device configured to produce aerosolized medicaments. For example, these systems include a nebulizer or aerosolizer. Liquid medicaments to be delivered via inhalation may be aerosolized and introduced into the respirable gas delivered by these systems prior to being administered to a patient. This configuration allows for the treatment of certain respiratory diseases by delivering respirable gas with entrained aerosolized medicament which is breathed for direct transport to the lungs. A nebulizer (pneumatic, mechanical, or electrical) may be connected at certain points in the system. For example, a supply tube of the system, such as supply tubes 406 and 706 of Figures 4 and 7A-7E, includes a port configured for attaching a nebulizer, from which aerosolized medicament enters the supply tube and is entrained in the respirable gas flow. As another example, a patient connector or nasal cannula configured at the end of the supply tube includes a port configured for attaching the nebulizer. In other implementations, an auxiliary unit, such as auxiliary units 404, 504, 604, 704, 804, and 904 of Figures 4-9, includes a port configured for attaching the nebulizer, from which aerosolized medicament enters the auxiliary unit and is entrained in the respirable gas flow.In some implementations, the aerosol is introduced into the breathing gas before the breathing gas enters a vapor transfer unit for humidification. In some implementations, the aerosol is introduced into the breathing gas before the breathing gas is humidified by the vapor transfer unit. The system may be configured to adjust the vaporization rate in the vapor transfer unit based on the amount of aerosol entrained in the breathing gas, by monitoring the aerosol flow rate via a flow sensor or level sensor in the nebulizer or a flow sensor in the port or auxiliary unit. An RFID tag or other label, chip, or sensor in the base unit may store information about the type of nebulizer or medication to be delivered via the nebulizer. In some implementations, high-viscosity fluids (i.e., > 6 cP) are used in the nebulizer to be aerosolized and subsequently entrained. The RFID tag may be read, and the stored information is transmitted to a controller in the base unit. Based on the information, the controller may adjust the vaporization rate or heating rate in the base unit. The controller may also be operatively coupled to the nebulizer and use the information to adjust the operation of the nebulizer. For example, if a high-viscosity fluid is indicated to be nebulized, the controller adjusts the vibration frequency, pressure, force, or other parameter of the nebulizer to account for the high viscosity.The controller can be operatively coupled to the nebulizer to perform feedback control of the nebulizer. For example, the nebulization rate can be adjusted by the controller in response to a measured patient parameter (e.g., respiratory rate, blood oxygen concentration). Treatment methods Provided herein are systems and methods for respiratory therapy. In some aspects, these systems and methods are used to treat certain respiratory diseases or conditions. The operation of the systems provided herein can be tailored to the specific respiratory disease or condition being treated. For example, certain supplemental gases or aerosolized medications are used to treat certain conditions. In some implementations, the systems described herein are used for the treatment of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These systems configured with a high-flow nasal cannula may be used for mechanical ventilation of patients with respiratory failure related to COVID-19. In some implementations, this form of therapy, which uses a high-flow nasal cannula and the system parameters described in Table 1 or Table 2, may be performed without intubation. In some implementations, this treatment method further utilizes a face mask to reduce the spread of aerosol particles or contaminants exhaled by the patient. Treatment of COVID-19 may involve introducing supplemental oxygen into the breathing gas via a supplemental gas inlet (e.g., supplemental gas inlets 1196 and 1296 of Figures 11 and 12).A pulse oximeter can be connected to the patient during treatment so that SpO2 can be monitored and the supplemental oxygen flow rate can be adjusted to provide sufficient oxygen to achieve a therapeutic oxygen level for the patient. Mobile use The systems and methods described herein may be used in a mobile configuration. The systems 100, 400, 500, 600, and 800 of Figures 1, 4 to 6, 8A and 8B may be used at home, in a vehicle, on a mobile platform or cart, or in a backpack. The systems and methods, which use a ventilator, are configured to receive and pressurize ambient air, such that they may operate without the need for an external source of gas such as wall air or pressurized tanks. Additionally, the systems and methods are configured to operate on battery power, such that they do not require an external source of power such as an electrical outlet or generator. The battery has sufficient capacity to provide heated and humidified respiratory therapy for hours, e.g., >8 hours, >6 hours, >4 hours, > hours, > 1 hour. For example, respiratory therapy systems are set up on a rolling cart, allowing a patient to move around their home or hospital while receiving respiratory therapy by moving with them. In another example, a patient in a vehicle (e.g., a personal vehicle, an ambulance, an airplane, or a helicopter) receives respiratory therapy via a dedicated auxiliary unit (or a patient circuit including the dedicated auxiliary unit, delivery tubing, and a patient connector or nasal cannula) configured to a first base unit. Upon arrival at a medical facility, the dedicated auxiliary unit is removed from the first base unit. As discussed above, the base unit may be configured to automatically stop operation when the auxiliary unit is removed. The first base unit remains in the vehicle while the auxiliary unit is transported with the patient to the facility. The dedicated auxiliary unit may then be re-docked to a second base unit at the medical facility, resuming respiratory therapy via the second base unit.The second base unit must be adjusted again with the correct therapy and started up, consuming valuable time. To expedite the boot time of the second base unit, the auxiliary unit may comprise an RFID tag, as discussed above, that stores previous operating conditions from when the auxiliary unit was used in the vehicle with the first base unit. The RFID tag may have data written to it by the first base unit. The data may indicate that the auxiliary unit was actively treating the patient and what therapy was being provided. Upon redocking to the second base unit, a reader in the second base unit reads the RFID tag, sending the data or information indicative of the previous operating conditions or therapy to the controller of the second base unit. The controller then adjusts the parameters to match the previous operating conditions, allowing the patient to resume the same respiratory therapy.The same assistive unit is used for the patient, allowing the patient to be transferred from transport to the facility without replacing the assistive unit. The data stored on the RFID tag may indicate: that the auxiliary unit was providing therapy, the time at which the therapy was interrupted, the therapy settings (e.g., respiratory gas flow rate, temperature, oxygen concentration, humidity, pump power, warming rate, valve settings), the state of the patient circuit (e.g., actual respiratory gas temperature compared to a setpoint temperature), and patient data (e.g., age, height, weight, disease type, disease state, concomitant disease, concomitant therapy). The data may be stored continuously such that ejecting the auxiliary unit from the base unit results in the last settings being stored.In some implementations, the RFID tag has limited data storage or writing operations, such that past data is overwritten by current data. An operator may initiate the writing operation before stopping therapy, or the controller may be configured to automatically write data upon receiving a user command to stop the operation. The controller may be configured to include a switch that stores the data and prompts the user to remove the device. In some implementations, data is stored whenever settings are changed, storing the last known settings. Upon redocking the auxiliary unit, the controller of the second base unit may be configured to generate a display prompt for the user to resume therapy if desired.In some implementations, therapy has elapsed for an extended time or the actual temperature was lower than the set point, so the second base unit operates the heating elements to warm the auxiliary unit before resuming therapy. The first base unit used in transport may have limited functions, for example, lacking some or all of the following features: liquid warming, liquid circulation, full range of flow rates, full range of oxygen therapy, liquid level sensing, valve control, and user interface / display. The base unit may include features that provide the minimum therapy needed for the specific patient or specific transport operation. A ventilator of lower pressure or flow rate capability may be used. The auxiliary unit may be correspondingly limited to operate only with the features to which the first base unit is limited. Removing some of the features from the first base unit for transport allows for extended operation in battery power or low power mode and for a more compact unit.When re-docking the auxiliary unit into the second base unit, if the first base unit lacks certain features, the user may be prompted to adjust the settings appropriately. In some implementations, the auxiliary unit may have limited functionality; for example, the delivery tube lacks a water jacket, the delivery tube has a solid insulator instead of a water jacket, and / or the auxiliary unit lacks a liquid pump. This may allow the device to be lighter in weight and less complex, which would be advantageous for mobile use. Example of high flow therapy Figures 13A and 13B show graphical representations (contour plots) of simulated amounts of carbon dioxide in a patient's airway during high flow therapy, in accordance with an illustrative implementation. In these implementations, a ventilator-based respiratory therapy system is used, such as systems 100, 400, 500, 600, and 800 of Figures 1, 4 through 6, 8A, and 8B. A nasal cannula transfers respirable gas from the system to a nostril of the patient. In both Figures 13A and 13B, the respirable gas flow rate through the nasal cannula is 40 L / min, and the patient is breathing at 24 breaths per minute. The amount of CO2 present in the patient's airway is captured in the contour plots when the patient is at peak expiratory flow, the maximum flow rate they reach during exhalation.Darker regions indicate a higher percentage of CO2, and lighter regions indicate a lower percentage of CO2. The simulations differ because Figure 13A uses a large-bore cannula, and Figure 13B uses a small-bore cannula. Using the large-bore cannula (specifically having a 4.13 mm inner diameter), simulated in Figure 13A, high-flow therapy results in a large percentage of CO2 (up to 0.0486 CO2 mass fraction) in the patient's upper airway. Patients typically rebreathe one-third of their previously expired tidal volume, where the previously exhaled breath (low in oxygen and with some CO2) is not completely exhaled and remains in the upper airway. As patients rebreathe, CO2 in this upper airway reservoir is drawn back into the lungs.Patients with acute respiratory failure rebreathe a higher percentage of gas, resulting in rebreathing larger amounts of carbon dioxide as they draw breaths from the upper airway reservoir. Accordingly, it is undesirable for the patient to have higher percentages of CO2 in the reservoir, especially when larger amounts of oxygen are needed for therapeutic effect. Figure 13B shows CO2 percentages based on high flow therapy simulation with a small bore cannula, specifically having an inner diameter of 2.64 mm according to the parameters in row 3 of Table 1 or row 3 of Table 2. The use of the small bore cannula, with the same operating parameters, leads to lower CO2 percentages in the patient’s upper airway compared to the implementation of a large bore cannula. Continuous high flow therapy with the small bore cannula washes the upper airway, because the smaller inner diameter of the nasal cannula tip induces a higher gas outflow velocity when operating at the same volumetric flow rate.A continuous, high flow of fresh gas with this increased outflow velocity flushes the patient's upper airway, effectively creating an upper airway oxygen reservoir (pharyngeal dead space) available for gas exchange upon rebreathing. In this implementation, rebreathing CO2 is avoided; instead, the CO2 is replaced with oxygen-rich gas, improving breathing efficiency. While the small-bore cannula exhibits better CO2 washout in the upper airway, the large-bore cannula may be advantageous for use in oxygen delivery. Accordingly, in some implementations, a large-bore cannula is used for oxygen delivery, and a small-bore cannula is used in situations where washout is more important (e.g., for hypercapnic therapy). Minimum back pressure to achieve high speed Systems and methods for high-velocity respiratory therapy are described herein. These systems and methods may utilize a nasal cannula to deliver respirable gas to a patient's nose. The cannulas used herein have one or more nasal prongs with outlets that are small relative to conventional cannula designs. The small outlet accelerates the flow of respirable gas to a velocity deemed high enough to achieve high-velocity nasal insufflation, which has the effect of flushing the upper airway as described above. The cannula can be designed so that each portion of its flow path has a large cross-section and smooth transitions whenever possible, except at the nasal tip where the tip cross-section tapers to a small diameter of the tip opening. Using such a design, one can assume that most or all of the pressure drop effected on the respirable gas flow through the nasal cannula is due to the taper of the nasal prong(s), such that the entire pressure drop across the nasal cannula contributes to the acceleration of the flow to high velocity. Described herein is a computational fluid dynamics (CFD) study performed to determine the minimum possible nasal cannula pressure drop that could be achieved for any given target velocity. The study uses a nasal cannula designed such that the pressure drop across the nasal cannula is zero until the flow is accelerated through the tip to the final exit velocity, such that the cannula pressure drop is used to accelerate the flow. Example cannula designs have tip inside diameters ranging from 1 mm to 4 mm. In the study, tip inside diameters from 1.27 mm (0.05 in) to 3.81 mm (0.15 in) were studied. Each tip size was simulated at a flow rate that would result in exit velocities of about 40, about 50, about 60, about 70, and about 80 m / s.Any of the ventilator-based respiratory therapy systems described herein, such as systems 100, 400, 500, 600, and 800 of Figures 1, 4 through 6, 8A, and 8B, or systems using other sources of respirable gas (e.g., compressors), can be designed to have the flow path size and pressure drops necessary to achieve the high velocity as described in the study. The complete results of the study are tabulated below in Table 4. Table 4: Results of the CFD study, showing the volumetric flow rate and cannula pressure drop resulting from exit velocities of approximately 40, approximately 50, approximately 60, approximately 70, and approximately 80 m / s, for each tip bore size. Tip ID (in) Tip ID (mm) Volume Flow Rate (L / min) Velocity (m / s) Cannula Pressure Drop [kPa] 0.05 1.27 5.8 38.2 1.04 0.05 1.27 7.3 47.7 1.59 0.05 1.27 8.7 57.5 2.30 0.05 1.27 10.2 67.4 3.14 0.05 1.27 11.8 77.4 4.10 0.06 1.524 8.4 38.6 1.04 0.06 1.524 10.5 48.2 1.61 0.06 1.524 12.7 57.8 2.31 0.06 1.524 14.8 67.7 3.17 0.06 1.524 17.0 77.6 4.15 0.07 1.778 11.6 39.1 1.06 0.07 1.778 14.6 48.9 1.65 0.07 1.778 17.5 58.7 2.38 0.07 1.778 20.5 68.7 3.26 0.07 1.778 23.6 79.1 4.39 0.08 2.032 15.2 39.1 1.06 0.08 2.032 19.0 48.8 1.65 0.08 2.032 22.8 58.6 2.38 0.08 2.032 26.8 68.8 3.31 0.08 2.032 30.7 79.0 4.35 0.09 2.286 19.5 39.7 1.08 0.09 2.286 24.4 49.6 1.68 0.09 2.286 29.3 59.5 2.42 0.09 2.286 34.4 69.8 3.37 0.09 2.286 39.5 80.2 4.43 0.1 2.54 24.2 39.7 1.07 0.1 2.54 30.2 49.6 1.67 0.1 2.54 36.3 59.8 2.44 0.1 2.54 42.5 70.0 3.33 0.1 2.54 48.9 80.4 4.39 0.11 2.794 29.4 40.0 1.07 0.11 2.794 36.7 49.9 1.67 0.11 2.794 44.1 60.0 2.44 0.11 2.794 51.6 70.2 3.33 0.11 2.794 59.2 80.5 4.37 0.12 3.048 35.4 40.4 1.08 0.12 3.048 44.2 50.5 1.70 0.12 3.048 53.2 60.7 2.47 0.12 3.048 62.2 71.0 3.40 0.12 3.048 71.5 81.6 4.51 0.13 3.302 41.3 40.2 1.08 0.13 3.302 51.8 50.4 1.70 0.13 3.302 62.2 60.6 2.46 0.13 3.302 72.8 70.9 3.39 0.13 3.302 83.7 81.5 4.49 0.14 3.556 48.2 40.5 1.11 0.14 3.556 60.5 50.7 1.74 0.14 3.556 72.9 61.2 2.53 0.14 3.556 85.4 71.6 3.47 0.14 3.556 98.1 82.3 4.62 0.15 3.81 55.5 40.6 1.11 0.15 3.81 69.7 51.0 1.74 0.15 3.81 83.6 61.1 2.53 0.15 3.81 98.4 71.9 3.48 Figure 14A shows a graph of cannula pressure drop as a function of exit velocity for each tip size and flow rate studied. For each tip size studied, the flow rate required to achieve a particular velocity is different. For example, to achieve a velocity of approximately 40 m / s, a 1.27 mm (0.05 in) tip requires a flow rate of 5.8 L / min, while a 2.54 mm (0.10 in) tip requires 24.2 L / min. However, in both cases, the pressure required to achieve that velocity is approximately 1 kPa, and this pattern is consistent across the tip sizes and flow rates studied for each velocity. This pattern shows that, in general, the minimum cannula pressure drop to achieve a particular velocity is constant, regardless of the tip diameter size.Figure 14A reflects this pattern, as tip size and flow rate combinations for each velocity cluster at approximately the same cannula pressure drop. When a fan is used to generate airflow, the fan is typically limited to a relatively low pressure, as compared to compressors. Fans sized for use in medical gas delivery generally do not exceed approximately 14 kPa (2 psi). Fans that can achieve these pressures are typically capable of very high flow rates that exceed medical gas supply requirements and are operated at a point on the fan's characteristic curve very close to the maximum available pressure. Operating near the maximum available pressure corresponds to a relatively low flow rate when compared to what the fan can deliver. Fans typically have a very flat characteristic curve at flow rates near their maximum pressure, and this means that at flow rates of 0 to 60 L / min, a fan can be assumed to have a relatively constant maximum pressure.Using this assumption, a combination of the maximum ventilator outlet pressure and the minimum pressure drop required to achieve a particular speed, the pressure required to deliver high velocity nasal insufflation can be expressed as a percentage of the maximum available pressure (assumed herein to be the outlet pressure of the breathing gas source). Accordingly, Figure 14B shows a graph of cannula pressure drop as a percentage of total available pressure of a 14 kPa ventilator as a function of output velocity. There are few ventilators sized for a respiratory therapy device that can deliver more than 14 kPa, and the curve shown in Figure 14B represents an ideal cannula where all of the pressure drop across the cannula is contributing to the acceleration of the respirable gas flow. Therefore, for any given velocity, it is unlikely that a cannula could be designed that requires a lower percentage of the total available pressure than shown in the graph in Figure 14B. In practice, the gas passageway used to transport the respirable gas from the ventilator to the nasal cannula cannot be of unlimited size. Larger tubing is cumbersome and may be uncomfortable for the patient. The additional surface area of ​​the larger tubing can exacerbate humidified gas fallout. Using a subset of the tip sizes and velocities studied in Figures 14A and 14B, another simulation was run to study the impact of gas passageway size on system pressure drop. The cross-sectional area of ​​the gas passageway, expressed as multiples of the tip cross-sectional area, ranged from 1.1 to 5 times the tip cross-sectional area. A gas passageway length of 40.6 cm (16 in) was assumed. The pressure drop across the gas passageway is compared to the minimum pressure drop for each particular tip size and velocity. The results are shown in the graph in Figure 14C. In the graph, when the gas passage cross-sectional area is 1.1 times the tip cross-sectional area, the pressure drop across the gas passage is 200 to 500% of the minimum cannula pressure drop. Increasing the gas passage cross-sectional area to 2.5 to 3 times the tip cross-sectional area reduces the pressure drop to approximately 50% of the minimum cannula pressure drop. Further increasing the gas passage size results in diminishing returns. In the systems described herein, a gas passage may be 2.5 times the tip cross-sectional area when using a cannula sized for adult patients, while a gas passage may be 3 times the tip cross-sectional area when using a cannula sized for pediatric patients.Due to the pressure drop, the respirable gas is delivered from the at least one nasal prong at a prong outlet pressure equal to the outlet pressure of the respirable gas source (e.g., about 14 kPa) less a cumulative pressure drop, which includes the pressure drop caused by the nasal cannula discussed above. The cumulative pressure drop may include the nasal cannula pressure drop and a gas passageway pressure drop. In some implementations, the cumulative pressure drop also includes a pressure drop caused by friction losses. Humidification measurement Described herein is a method for calculating the water content in a humidified gas stream, given a respiratory therapy system (or humidifier) ​​in which the gas stream is fully saturated. The method is based on a relationship between the gas flow rate and a measure of the energy supplied to heat the water used for humidification. The method may be used in any of the systems described herein, for example, those described in connection with Figures 1, 2, 4 through 9, and other humidifiers that rely on electrical energy supplied for water vaporization. The water vapor content of the gas stream delivered to a patient is an important performance measure for medical respiratory humidifiers. Compliance standards provide a minimum water vapor content level in mg / L of gas stream to be classified as a medical humidifier. Output systems use gravimetric methods or a chilled mirror hygrometer to directly measure the humidity of the delivered gas; however, these are manual methods that require an operator to interact with the systems, and collecting humidification data from large sample sets (e.g., during research and development) can be time-consuming. The method described herein provides accurate humidification measurements that can be performed in a fully automated manner, for example, by a controller within the system. One particular use of the method involves collecting humidification data over the period of an extended life test of the humidifier without significant manual labor and risk of data collection errors. In the respiratory therapy system, the breathing gas may be supplied over a range of flow rates (e.g., between 5 and 45 L / min). The humidifier (either within the system or external to the system and receiving the breathing gas from the system) receives electrical power from, e.g., a power supply within the system. A heater in the humidifier, such as the induction heater described above, uses the electrical power to heat water in a reservoir of the humidifier. When the system is operating in a steady state (e.g., the amount of water and the water temperature in the humidifier are approximately constant), it can be approximated that all of the supplied energy (or a known fraction of the supplied energy, based on a heater efficiency) is directed toward vaporizing the water, where the water vaporization energy determines the energy required to generate water vapor in the gas stream. Plotting the energy supplied to the heater over a range of flow rates gives a curve that has a linear region. Figure 15 shows the energy vs. flow graph at a breathing gas temperature setpoint of 39°C, using a respiratory therapy system similar to those described herein. The linear region indicates where the gas stream is fully saturated with water, for example, at 44 mg / L at 37°C gas. The slope and y-intercept of the linear region provide a characteristic of the specific system in which the humidity measurement is being made. A trend line can be calculated using the data in the linear region and extrapolated across the full range of flow rates. The trend line provides the expected energy contribution if the gas stream remained fully saturated.The ratio of the observed energy (indicated by diamond symbols in Figure 15) to the expected energy according to the trend line (indicated by the dotted line in Figure 15) can be used to determine the water content in the gas stream by multiplying the fully saturated state humidification level (e.g., 44 mg of water per L of gas at 37 °C gas) by the ratio. In the example shown in Figure 15, measurements were taken on a sample system similar to those described herein over a range of flow rates using ambient air composite gas having 21% FiCte. The gas temperature set point was 37°C, and ambient conditions were 22°C and 29% RH. At 45 L / min breathing gas flow rate, the water content in the supplied gas stream was calculated to be 30.3 mg / L using the method described herein. A controller in the system or an external computer can programmatically adjust the gas flow rate and then receive and record heater energy data to perform this humidity level calculation. The gas temperature can also be programmatically adjusted by the controller / computer, which can contain memory storage tables or formulas to determine the full saturation level for a given gas temperature. Humidifier reservoirs may be refilled periodically, and the power input to the heater is temporarily high while the temperature of the newly introduced water is raised to meet the setpoint water temperature (assuming the incoming water is coming from a lower temperature source, such as room temperature). The system may be programmed to only determine humidity using this method when the reservoir is in a steady state, which may be approximated by starting a predetermined period of time after refilling has ceased. Alternatively, the amount of water used for refilling may be measured by a level sensor in the reservoir (such as the capacitive sensor described herein) in order to determine a period of time until the refill reservoir has reached the steady state. Humidification calculations may be necessary to account for ambient humidity in order to assess how much water is already present in the breathing gas in the system's air intake. For example, the systems described herein may deliver a mixture of ambient air and pure, dry oxygen to provide elevated oxygen levels to the patient. When the system is set to deliver 100% oxygen, humidification due only to the system is measured. Figure 16 shows a flowchart describing a humidification measurement method 1600, according to one example. The method 1600 includes steps 1602, 1604, and 1606. Step 1602 involves providing breathing gas to a patient at a gas flow rate and a gas temperature using a respiratory therapy system. The system comprises a controller, a humidifier having a reservoir containing water and a heater configured to heat water in the reservoir, and a power supply coupled to the heater and configured to supply power to the heater. Step 1604 involves humidifying the breathing gas by supplying power to the heater and heating water in the humidifier reservoir. Step 1606 involves determining a humidity level of the breathing gas based on (1) a ratio of the supplied power to an expected energy, and (2) a saturated humidity level for the gas temperature. In some implementations, the expected energy is determined based on a linear relationship between the gas flow rate and the energy delivered over a range of flow rate values. For example, the range of flow rate values ​​is between 5 L / min and 25 L / min. In particular, the range of values ​​may be a subset in which the breathing gas is fully saturated due to humidification. The power supply may transmit data indicative of the supplied power to the controller so that the data is used in the humidification calculation. The controller may perform the determining step. The controller may include a memory that stores a table of saturated humidity level values ​​for a range of gas temperature values ​​or one or more formulas for determining saturated humidity level values ​​given a specific gas temperature value. The determining step may include retrieving the saturated humidity level from the memory. The gas temperature may be stored in the memory as a setpoint temperature. The controller may automatically perform the determining step when the respiratory therapy system is in a stable state (e.g., when the water in the reservoir is at a stable level or a stable temperature).The tank can be refilled periodically (either manually or automatically via the controller) at which point the heat demand will be temporarily high for a period of time to bring the newly added water up to the set temperature, so that the humidification measurement can be taken after the period of temporarily high heat demand (e.g. a predetermined period of time or a period calculated based on the amount of water added during refill). Suitable humidifiers for this method include any humidifier that uses supplied electrical power to vaporize water. For example, wick humidifiers, vapor transfer cartridges, hot pot humidifiers, and other suitable humidifiers may be used. In some implementations, the humidifier includes a heating plate disposed within the reservoir and an inductive element configured to receive supplied power and generate a magnetic induction current in the heating plate to transfer heat to the water in the reservoir. The inductive element may be physically separated from the heating plate (e.g., the inductive element is outside the reservoir and not in contact with the water). The foregoing is merely illustrative of the principles of the disclosure, and the apparatus may be practiced by implementations other than those described, which are presented for purposes of illustration and not limitation. It is understood that the apparatus disclosed herein, although shown for use in high-flow therapy systems, may be applied to systems used in other ventilation circuits. Those skilled in the art will devise variations and modifications after reviewing this disclosure. The disclosed features may be implemented in any combination and subcombination (including multiple dependent combinations and subcombinations) with one or more features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated into other systems. In addition, certain features may be omitted or not implemented. / zQQQn / zznz / q / υιλι Examples of changes, substitutions, and alterations are readily apparent to those skilled in the art and can be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and are part of this application. Illustrative modalities: A1. A system for providing respiratory therapy to a patient, the system comprising: a fan configured to: receiving breathing gas from ambient air, a tank, or a wall outlet; and expelling pressurized breathing gas; a conduit in fluid communication with the ventilator, the conduit receiving respirable gas from the ventilator and expelling the respirable gas at a first pressure; and a nasal cannula having at least one nasal prong, the nasal cannula being in fluid communication with the conduit and configured to receive respirable gas from the conduit at the first pressure, the at least one nasal prong being configured to deliver the respirable gas to a nostril of the patient; wherein the nasal tip is configured to provide respirable gas at an exit velocity of at least about 40 m / s and less than about 75 m / s. A2. The system according to A1, wherein a nasal prong has an inner diameter greater than or equal to about 1.4 mm and less than about 1.8 mm, and the system has a maximum flow set point of about 9 L / min and less than about 28 L / min. A3. The system according to A1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.8 mm and less than about 1.9 mm, and the system has a maximum flow set point greater than or equal to about 13 L / min and less than about 31 L / min. A4. The system according to A1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.9 mm and less than about 3 mm, and the system has a maximum flow set point greater than or equal to about 21 L / min and less than about 60 L / min. A5. The system according to A1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 3 mm and less than about 4 mm, and the system has a maximum flow set point greater than or equal to about 34 L / min and less than about 80 L / min. A6. The system according to A1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.1 mm and less than about 1.6 mm, and the nasal cannula has a pressure drop of less than about 80 hPa when operated at a maximum flow set point of about 8 L / min. A7. The system according to A1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.5 mm and less than about 2 mm, and the nasal cannula has a pressure drop of less than about 100 hPa when operated at a maximum flow set point of about 20 L / min. A8. The system according to A1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.9 mm and less than about 3.5 mm, and the nasal cannula has a pressure drop of less than about 80 hPa when operated at a maximum flow set point of about 40 L / min. A9. The system according to any of A1-A8, further comprising a controller and a processor configured to: receive the first data indicative of one or more dimensions of the nasal cannula; receiving the second data indicative of a respirable gas flow rate; and calculating the exit velocity based on the first data and the second data. A10. The system according to A9, further comprising a display, and wherein the processor is further configured to generate for displaying at least one of: the flow rate, the output velocity, a maximum flow set point, and a pressure drop. A11. The system according to any of A9 and A10, wherein the fan, controller and processor are housed in a base unit, the system further comprising an attachable unit configured to be reversibly connected to the base unit. A12. The system according to Al 1, wherein the conduit is configured to be reversibly connected to the dockable unit, wherein the nasal cannula is configured to be reversibly connected to the conduit, and wherein the processor receives the first data when the dockable unit is connected to the base unit. A13. The system according to A12, wherein the processor receives the first data from an RFID tag within the dockable unit. A14. The system according to A9, wherein the first data comprises an inner diameter of the at least one nasal tip. A15. The system according to A9, wherein the processor is configured to identify the nasal cannula based on the first data. A16. The system according to any of A9-A15, further comprising at least one sensor configured to measure the flow rate of respirable gas and send the second data to the processor. A17. The system according to any of A9-A16, wherein the processor is further configured to receive a user input to change at least one of: the breathing gas flow rate at a modified breathing gas flow rate, or the exit velocity at a modified velocity. A18. The system according to A17, wherein the controller is configured to change the breathing gas flow rate to the modified flow rate based on user input. A19. The system according to any of A17 and A18, wherein the processor is further configured to calculate a modified speed based on the modified flow rate and the first data. B1. A method for providing respiratory therapy to a patient, the method comprising: ! 705*0 / 1 / 7707 / 3 / YILI expelling a flow of respirable gas from a ventilator through a conduit and into a nasal cannula; and providing the respirable gas to a nose of the patient from at least a nasal prong of the nasal cannula, the nasal cannula being in fluid communication with the conduit and configured to receive the respirable gas from the conduit; wherein the at least one nasal prong is configured to provide respirable gas from a distal end of the at least one nasal prong at an exit velocity of at least about 40 m / s and less than about 75 m / s. B2. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.4 mm and less than about 1.8 mm, and the ventilator has a maximum flow set point greater than or equal to about 9 L / min and less than about 28 L / min. B3. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.8 mm and less than about 1.9 mm, and the ventilator has a maximum flow set point greater than or equal to about 13 L / min and less than about 31 L / min. B4. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.9 mm and less than about 3 mm, and the ventilator has a maximum flow set point greater than or equal to about 21 L / min and less than about 60 L / min. B5. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 3 mm and less than about 4 mm, and the ventilator has a maximum flow set point greater than or equal to about 34 L / min and less than about 80 L / min. B6. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.1 mm and less than about 1.6 mm, and the nasal cannula has a pressure drop of less than about 80 hPa when the ventilator operates at a maximum flow set point of about 8 L / min. B7. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.5 mm and less than about 2 mm, and the nasal cannula has a pressure drop of less than about 100 hPa when the ventilator operates at a maximum flow set point of about 20 L / min. B8. The method according to B1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.9 mm and less than about 3.5 mm, and the nasal cannula has a pressure drop of less than about 80 hPa when the ventilator operates at a maximum flow set point of about 40 L / min. B9. The method according to any of B1-B8, further comprising: receive the first data indicative of one or more dimensions of the nasal cannula; receiving the second data indicative of a respirable gas flow rate; and calculating the exit velocity based on the first data and the second data. B10. The method according to B9, further comprising: generate to display at least one selected from the group of: flow rate, output velocity, a maximum flow set point, and a pressure drop. B11. The method according to any of B9 and B10, comprising: generate to display flow rate and output velocity. B12. The method according to any of B9-B11, further comprising: receive user input to increase or decrease the breathing gas flow rate; change the flow rate to a modified breathing gas flow rate; calculate a modified velocity based on the modified flow rate and the first data; and generate for display at least one selected from the group of: the modified flow rate and the modified velocity. C1. The system or method according to any of A1-A19 and B1-B12, wherein the breathable gas is configured to be humidified and heated. C2. The system or method according to any of items A1 -A19 and B1 -B12, wherein the output velocity is at least about 40 m / s and less than about 70 m / s. C3. The system or method according to any of items A1 -A19 and B1 -B12, wherein the output velocity is at least about 40 m / s and less than about 65 m / s. C4. The system or method according to any of items A1 -A19 and B1 -B12, wherein the exit velocity is at least about 40 m / s and less than about 60 m / s. C5. The system or method according to any of items A1 -A19 and B1 -B12, wherein the exit velocity is at least about 40 m / s and less than about 55 m / s. C6. The system or method according to any of items A1 -A19 and B1 -B12, wherein the output velocity is at least about 40 m / s and less than about 50 m / s. C7. The system or method according to any of items A1 -A19 and B1 -B12, wherein the exit velocity is at least about 40 m / s and less than about 45 m / s. C8. The system or method according to any of items A1 -A19 and B1 -B12, wherein the exit velocity is at least about 40 m / s. D1. A system for providing respiratory therapy to a patient, the system comprising: a base unit comprising: a ventilator configured to expel respirable gas; and a controller; an auxiliary unit configured to be reversibly coupled to the base unit, wherein the auxiliary unit comprises an auxiliary unit outlet; and a supply tube configured to receive the respirable gas from the auxiliary unit outlet and transmit the respirable gas to the patient. D2. The system according to D1, wherein the base unit further comprises a measuring device comprising: a first flow sensor, a second flow sensor, and a device duct in fluid communication with the ventilator, wherein the first flow sensor and second flow sensor are positioned in series along the duct. D3. The system according to D2, wherein the device duct is configured to: receive the breathing gas from a gas inlet of the base unit; directing the breathing gas through the first flow sensor, wherein the first flow sensor is configured to output a first measurement of the breathing gas; directing the breathing gas through the second flow sensor, wherein the second flow sensor is configured to output a second measurement of the breathing gas; and exhausting the breathing gas to the ventilator. D4. The system according to D3, wherein the controller is configured to adjust a respirable gas flow rate of the ventilator based on at least one of the first measurement or the second measurement. D5. The system according to any of D2-D4, wherein the first flow sensor and the second flow sensor are mass flow sensors. D6. The system according to any of D2-D5, wherein the first flow sensor and the second flow sensor are each configured to be calibrated relative to each other. D7. The system according to any of D2-D6, wherein the device conduit comprises a first segment configured to direct the respirable gas through the first flow sensor and a second segment configured to direct the respirable gas through the second flow sensor, wherein the first segment and the second segment are approximately straight. D8. The system according to any of D2-D7, wherein the system comprises a supplemental gas inlet configured to receive a supplemental gas from an external gas source and add the supplemental gas to the breathing gas, wherein the supplemental gas inlet is in fluid communication with the device conduit and is disposed between the first flow sensor and the second flow sensor. D9. The system according to D8, further comprising a supplemental valve configured to control the flow of supplemental gas through the supplemental gas inlet. D10. The system according to D9, wherein the supplementary valve is a solenoid valve. D11. The system according to any of D9 and D10, wherein the first flow sensor is configured to output a first measurement of the breathing gas, and wherein the second flow sensor is configured to output a second measurement of a mixture of the breathing gas and the supplemental gas. D12. The system according to D11, wherein the controller is configured to calculate a flow difference between the first measurement and the second measurement, wherein the flow difference indicates an amount of one or more components of the supplemental gas added to the breathing gas, and wherein the controller is configured to calculate one or more concentrations of one or more components in the mixture based on the flow difference and the second measurement. D13. The system according to D12, wherein the controller is configured to operate the supplementary valve to control the amount added based on the calculated flow difference. D14. The system according to D13, wherein the controller is configured to: receive as an input a blank concentration, compare one or more calculated concentrations with the blank concentration, and control the amount added based on the comparison. D15. The system according to any of D12-D14, wherein the flow difference is less than approximately 5% of the first measurement. D16. The system according to D15, wherein the flow difference is less than approximately 1 % of the first measurement. D17. The system according to any of D8-D16, wherein the external gas source is one selected from the group of: a wall gas outlet, a gas concentrator, and a gas tank. D18. The system according to any of D8-D17, wherein the supplemental gas is oxygen, oxygen-concentrated respirable gas, helium, nitric oxide, heliox, an anesthetic gas, or a gas containing aerosolized medicament. D19. The system according to any of D8-D18, wherein the controller is configured to operate the supplemental valve to pause the flow of the supplemental gas and to calibrate the first flow sensor and the second flow sensor to each other while the flow of the supplemental gas is paused, wherein the calibration reduces an error of the calculated flow difference to an error of the second flow sensor. D20. The system according to any of D8-D19, further comprising: one or more additional supplemental gas inlets for adding one or more additional supplemental gases; and one or more additional flow sensors, wherein the device comprises an additional flow sensor for each of the additional supplemental gas inlets. D21. The system according to any of D1-D20, wherein the base unit may comprise a seat configured to receive the auxiliary unit when the auxiliary unit is coupled to the base unit. D22. The system according to D21, wherein the base unit comprises at least one alignment sensor, and the auxiliary unit comprises at least one alignment marker. D23. The system according to D22, wherein the at least one alignment sensor is configured to transmit a first signal to the controller when the at least one alignment marker is aligned with the at least one alignment sensor. D24. The system according to any of D22 and D23, wherein the at least one alignment sensor is configured to transmit a second signal to the controller when the at least one alignment marker is not aligned with the at least one alignment sensor. D25. The system according to D24, wherein the controller is configured to stop the operation of the system when the controller receives the second signal. D26. The system according to any of D24 and D25, wherein the controller generates an alarm when the controller receives the second signal. D27. The system according to D26, wherein the alignment of the at least one alignment marker with the at least one alignment sensor indicates that the auxiliary unit is fully seated in the seat. D28. The system according to any of D21-D27, wherein the auxiliary unit comprises a spring return configured to eject the auxiliary unit from the seat. D29. The system according to any of D21-D28, wherein the auxiliary unit comprises at least one tab configured to lock into a depression of the seat. D30. The system according to any of D22-D29, wherein the at least one alignment marker is a magnet, and the at least one alignment sensor is a Hall effect sensor. D31. The system according to any of D22-D29, wherein the at least one alignment marker is an RFID tag, and the at least one alignment sensor is an RFID reader. D32. The system according to D31, wherein the RFID tag comprises information about the auxiliary unit. D33. The system according to D32, wherein the information includes at least one selected from the group of: a usage history of the auxiliary unit, a lifetime of the auxiliary unit, a remaining lifetime of the auxiliary unit, one or more functionalities of the auxiliary unit, integrated license, and recommended operating parameters. D34. The system according to D33, wherein one or more functionalities is selected at least one from the group of: low flow, high flow, aerosolization, humidification, oxygenation, nitric oxide, helium, and closed-loop oxygen control. D35. The system according to any of D32-D34, wherein the controller is configured to adjust a range of acceptable flow rates of the breathing gas based on the information. D36. The system according to any of D1-D35, wherein the base unit further comprises a heat exchanger configured to cool the respirable gas exhausted from the fan. D37. The system according to D36, wherein the heat exchanger is configured to disperse heat radially from the exhausted breathing gas. D38. The system according to any of D36 and D37, wherein the heat exchanger is configured to decrease a breathing gas temperature of the exhaust breathing gas to a target breathing gas temperature. D39. The system according to any of D1-D38, wherein the auxiliary unit is configured to be reversibly coupled to the base unit via one or more couplings, at least one of the one or more couplings being configured to allow fluid communication of breathing gas from the base unit to the auxiliary unit. ! 7OPQn / 77n7 / 3 / YIL D40. The system according to D39, wherein the at least one coupling configured to allow fluid communication is an occlusion valve. D41. The system according to D40, wherein the occlusion valve is operatively coupled to the controller, and wherein the occlusion valve is configured to simultaneously control the expelled respirable gas and a liquid flow. D42. The system according to D41, wherein the occlusion valve is configured to receive the liquid flow from an external liquid supply and direct the liquid flow to the auxiliary unit. D43. The system according to any of D41 and D42, wherein the occlusion valve is configured to receive the respirable gas expelled from the ventilator and direct the respirable gas to the auxiliary unit. D44. The system according to any of D40-D43, wherein the occlusion valve comprises: an air path valve seal; a bellows; and a valve actuator; wherein the valve actuator is configured to expand and contract the bellows and raise and lower the air path valve seal. D45. The system according to D44, wherein the valve actuator is a linearly actuated rod. D46. The system according to any of D44 and D45, wherein the controller is configured to position the valve actuator in one of at least three actuator positions, and wherein the valve actuator is configured to position the air path valve seal in one of at least three air path positions. D47. The system according to any of D44-D46, wherein the occlusion valve further comprises a gas seal, which forms an annular space around the air path valve seal. D48. The system according to any of D44-D47, wherein the occlusion valve further comprises a flexible diaphragm, wherein the air path valve seal actuates the flexible diaphragm to be in one of the at least three diaphragm positions abutting the flexible diaphragm when the air path valve seal is lifted by the valve actuator. D49. The system according to any of D46-D48, wherein the at least three actuator positions include a retracted position, a partially extended position, and a fully extended position. D50. The system according to D49, wherein the retracted position blocks breathing gas and allows liquid flow, wherein the partially extended position allows both breathing gas and liquid flow through the occlusion valve, and wherein the fully extended position allows breathing gas through the occlusion valve and blocks liquid flow. D51. The system according to any of D49 and D50, wherein when the valve actuator is in the fully extended position, the flexible diaphragm occludes an outlet of a liquid inlet pipe. D52. The system according to any of D49-D51, wherein the controller is configured to position the valve actuator in the partially extended position or the fully extended position when the controller receives the first signal. D53. The system according to any of D49-D52, wherein the controller is configured to position the valve actuator in the retracted position when the controller receives the second signal. D54. The system according to any of D49-D53, wherein when the valve actuator is in the retracted position, the air path valve seal prevents the ingress of liquid into the base unit. D55. The system according to any of D1-D54, wherein the auxiliary unit comprises a liquid container and a vapor transfer cartridge (VTC) configured to humidify the respirable gas, wherein the liquid container comprises an outlet conduit in fluid communication with an inlet of the VTC cartridge. D56. The system according to D55, wherein the base unit comprises a level sensor operatively coupled to the controller and configured to output at least one liquid level measurement indicating a liquid level in the liquid container. D57. The system according to D56, wherein the controller is configured to calculate a VTC output humidity based on the at least one liquid level measurement and the at least one flow measurement. D58. The system according to D57, wherein the controller is configured to adjust the valve actuator based on the outlet humidity. D59. The system according to any of D56-D58, wherein the controller is configured to compare the at least one liquid level measurement with a reference liquid level and at least one to generate an alarm or stop the operation of the system. D60. The system according to any of D56-D59, wherein the level sensor is a capacitive sensor. D61. The system according to any of D1-D60, wherein the auxiliary unit comprises a heating plate in a heating section, and wherein the base unit comprises a heat actuator configured to be operatively coupled to the heating plate and is not in contact with the heating plate. D62. The system according to D61, wherein the heat actuator is a coil that is configured to induce a current in the heating plate. D63. The system according to D62, wherein the induced current generates heat on the heating plate due to a resistance of the heating plate. D64. The system according to any of D61-D63, wherein the heating plate is configured to be submerged within the auxiliary unit and heat the liquid. / zQQQn / zznz / q / υιλι D65. The system according to any of D61-D64, wherein the heating plate does not contact an external surface of the auxiliary unit. D66. The system according to any of D61-D65, wherein the heating plate comprises a protruding tab, and wherein the base unit comprises a temperature sensor configured to output a temperature measurement of the protruding tab. D67. The system according to D66, wherein the controller is configured to receive the temperature measurement and compare the temperature measurement with a reference temperature. D68. The system according to D67, wherein, based on comparing the temperature measurement with the reference temperature, the controller is configured to at least one of stopping the operation of the system or generating an alarm. D69. The system according to any of D61-D68, wherein the actuator is configured to operate while the system operates without an external power supply. D70. The system according to any of D61-D69, wherein the heating plate is specific in orientation relative to the heat actuator. D71. The system according to any of D1-D70, wherein the auxiliary unit comprises a pump configured to pump the liquid into the auxiliary unit. D72. The system according to D71, wherein the pump comprises a rotor cup, and wherein the base unit comprises a stator configured to be magnetically coupled to the rotor cup. D73. The system according to any of D71 and D72, wherein the pump is configured to pump the liquid through a liquid circuit of the auxiliary unit, wherein a bolus of the liquid in the liquid circuit travels sequentially through the pump, the jacket, the VTC, the liquid vessel and the heating section. D74. The system according to any of D1-D73, wherein the supply tube comprises a jacket in fluid communication with the auxiliary unit and a gas conduit in fluid communication with the VTC. D75. The system according to D74, wherein the pump is configured to pump the liquid from the heating section to the supply pipe jacket. D76. The system according to D75, wherein the jacket is configured to transfer heat from the liquid in the jacket to the breathing gas in the gas duct. D77. The system according to any of D55-D76, wherein a VTC temperature of the VTC is lower than a supply temperature of the breathing gas in the gas duct. D78. The system according to D77, wherein the supply temperature is greater than a dew point of the respirable gas in the supply pipe. D79. The system according to any of D74-D48, wherein the delivery tube comprises one or more radial ribs extending through the jacket. D80. The system according to D79, wherein one or more radial ribs prevent kinking or blockage of the gas conduit when the supply pipe is bent. D81. The system according to any of D74-D80, wherein the controller is configured to operate the pump to control a jacket flow rate of liquid into the jacket. D82. The system according to any of D74-D81, wherein the jacket comprises: a first section configured to receive the liquid from the auxiliary unit and transmit the liquid to a distal end of the supply tube, and a second section configured to receive the liquid from the first section and transmit the liquid to the auxiliary unit. wherein the jacket is configured to flow liquid through the first section and through the second section in opposite directions. D83. The system according to any of D1-D82, wherein the respirable gas expelled by the ventilator is characterized by a gas velocity configured to prevent accumulation of liquid in the supply tube. D84. The system according to any of D1-D83, further comprising a nasal cannula configured to be coupled to a patient-proximal end of the delivery tube, wherein the nasal cannula is configured to direct respirable gas into at least one nose of the patient. D85. The system according to any of D1-D84, wherein the auxiliary unit output has a bell shape configured for at least one of: allow bending of the supply tube at the auxiliary unit outlet, prevent kinking of the supply tube at the auxiliary unit outlet, or prevent dislodgement of the supply tube at the auxiliary unit outlet. D86. The system according to any of D73-D85, wherein the auxiliary unit comprises a supply connector configured to connect an outlet cap of the VTC to the gas conduit and a pump outlet to the jacket. D87. The system according to any of D1-D86, wherein the auxiliary unit comprises a housing configured to confine respirable gas and liquid within the auxiliary unit. D88. The system according to any of D1-D87, wherein the base unit comprises a removable battery and a backup battery. D89. The system according to D88, wherein the controller is configured to initiate a low power mode for the system when the removable battery is removed. D90. The system according to any of D88 and D89, wherein the system is configured to operate without the removable battery. D91. The system according to any of D88-D90, wherein the backup battery is configured to provide power to the ventilator and the controller. D92. The system according to D91, wherein the backup battery is configured to provide power for at least about one hour. D93. The system according to any of D89-D92, wherein the lower power mode allows operation of one or more alarms and the ventilator. D94. The system according to any of D1-D93, wherein the base unit comprises one or more interfaces configured to operatively couple one or more external devices to the controller. D95. The system according to D94, wherein one or more external devices includes a pulse oximeter configured to output data to the controller. D96. The system according to D95, wherein the controller is configured for closed-loop control of patient oxygen based on pulse oximeter data. D97. The system according to any of D95 and D96, wherein the controller is configured to adjust the flow rate of supplemental gas through the supplemental gas inlet based on pulse oximeter data, wherein the supplemental gas comprises oxygen. D98. The system according to D97, wherein the supplemental gas flow rate is adjusted to set an oxygen concentration of the breathing gas provided to the patient at a minimum oxygen concentration that is determined to have a therapeutic effect on the patient based on pulse oximeter data. D99. The system according to any of D95 and D96, wherein the pulse oximeter data includes SpO2 data and alarm condition signals, and wherein the controller is configured to: receiving pulse oximeter data through a pulse oximeter interface; From the SpO2 data, determine the PaO2 data to calculate an appropriate oxygen concentration of the breathing gas; performing adaptive feedback control of the breathing gas based on SpO2 level signals via a gas interface, wherein the adaptive feedback control is provided by a proportional integral derivative (PID) controller; receiving data via the gas interface including a signal indicating that the breathing gas supplied by the measuring device has been manually switched; and upon receiving the signal via the gas interface, entering a manual override mode and ceasing to send adaptive feedback control signals to the gas interface. D100. The system according to D99, wherein the controller is configured to compare measurement data with alarm limits and to initiate an alarm condition if the measured data are outside the alarm limits. D101. The system according to any of D99 and D100, wherein the gas interface is operatively coupled to the supplemental valve, and wherein the adaptive feedback control of the breathing gas comprises adjusting the flow rate of supplemental gas through the supplemental gas inlet upon actuation of the supplemental valve. D102. The system according to any of D99-D101, wherein the controller comprises a memory configured to store a look-up table, wherein the controller determines PaO2 data by referencing the look-up table, and wherein the controller is configured to convert a received SpO2 value to a PaO2 value by interpolation upon determining that the received SpO2 value is not present in the look-up table. D103. The system according to D102, wherein the look-up table is derived from a sigmoidal oxyhemoglobin dissociation curve. D104. The system according to any of D95-D103, wherein the pulse oximeter data includes one or more signals indicative of a current blood oxygen level of the patient, and wherein the controller is configured to: receive via a pulse oximeter interface one or more signals indicative of the current blood oxygen level; receive via a gas interface data indicative of the breathing gas and supplemental gas mixture; compare the one or more signals indicative of current blood oxygen level with a target blood oxygen level; calculate an appropriate change to the mixture to achieve a change in a percentage of oxygen in the mixture; alter the percentage of oxygen in the mixture by actuating the supplemental valve; and receive new signals from the pulse oximeter interface indicative of the patient's current blood oxygen level. D105. The system according to any of D95-D104, wherein the one or more external devices include a transcutaneous carbon dioxide sensor configured to output to the controller at least one carbon dioxide measurement of the patient. D106. The system according to D105, wherein the controller is configured for closed-loop control of patient carbon dioxide based on the at least one patient carbon dioxide measurement. D107. The system according to any of D95-D106, wherein the one or more external devices includes a pulse oximeter and a transcutaneous carbon dioxide sensor, wherein the pulse oximeter is configured to output oxygen data to the controller, and wherein the transcutaneous carbon dioxide sensor is configured to output carbon dioxide data to the controller. D108. The system according to D107, wherein the controller is configured to: receive, via the one or more interfaces, oxygen data from the pulse oximeter and carbon dioxide data from the transcutaneous carbon dioxide sensor; Compare the oxygen and carbon dioxide data to a reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value; and determine whether to provide the patient with high oxygen therapy or high flush therapy. D109. The system according to D108, wherein the controller is further configured to, upon determining to provide the patient with high oxygen therapy, increase the flow rate of the supplemental gas through the supplemental gas inlet by actuating the supplemental valve. D110. The system according to D108, wherein the controller is further configured to, upon determining to provide the patient with high flush therapy, increase the ventilator respirable gas flow rate. D111. The system according to any of D1-D110, wherein the base unit comprises a front-end computer operatively coupled to the controller and a display operatively coupled to the front-end computer. E1. A method for measuring respirable gas flow in a respiratory therapy device, the method comprising: generating a first measurement of the breathing gas flow using a first flow sensor; generating a second measurement of the respirable gas flow using a second flow sensor; and adjusting one or more parameters of the respiratory therapy device based on at least one of the flow measurement or the second measurement. E2. The method according to E1, wherein the first flow sensor and the second flow sensor are mass flow sensors, and the first measurement and the second measurement indicate mass flow rates of the respirable gas flow. E3. The method according to any of E1 and E2, wherein adjusting one or more parameters comprises adjusting a gas flow rate of the breathing gas flow based on the second measurement. E4. The method according to E3, wherein adjusting the gas flow rate comprises controlling a fan configured to exhaust the flow of respirable gas. E5. The method according to any of E1-E4, further comprising calibrating each of the first flow sensor and the second flow sensor relative to each other. E6. The method according to any of E1-E5, further comprising mixing the breathing gas flow with supplemental gas flow to form a mixed flow after taking the first measurement. E7. The method according to E6, further comprising calculating a flow difference between the first measurement and the second measurement, wherein the second measurement is indicative of the mixed flow. E8. The method according to E7, further comprising calculating a concentration of one or more components of the mixed flow based on the flow difference and the second measurement. E9. The method according to E8, further comprising: receive as an input a target concentration, and compare the concentration with the target concentration. E10. The method according to E9, wherein adjusting one or more parameters comprises adjusting a flow rate of the supplemental gas flow based on comparing the concentration with the target concentration. E11. The method according to E10, wherein adjusting the supplemental gas flow rate comprises actuating a solenoid valve. E12. The method according to any of E7-E11, wherein the flow differences are less than about 1 % of the first measurement. E13. The method according to any of E7-E12, further comprising: pausing the flow of the supplemental gas; and calibrating the first flow sensor and the second flow sensor to each other while the flow of supplemental gas is paused, wherein the calibration reduces an error of the calculated flow difference to an error of the second flow sensor. E14. The method according to any of E6-E13, further comprising: receiving pulse oximeter data from a pulse oximeter; and adjusting the flow rate of the supplemental gas flow based on the pulse oximeter data, wherein the supplemental gas comprises oxygen. E15. The method according to E14, further comprising: Determine a minimum oxygen concentration that has a therapeutic effect on the patient based on pulse oximeter data; and adjust the flow rate of the supplemental gas flow by adjusting the oxygen concentration of the breathing gas. E16. The method according to any of E14 and E15, wherein the pulse oximeter data includes SpO2 data and alarm condition signals, and further comprising: From the SpO2 data, determine the PaO2 data; calculate an appropriate oxygen concentration of the breathing gas; performing adaptive feedback control of the breathing gas based on the SpO2 level signals, wherein the adaptive feedback control is provided by a proportional integral derivative (PID) controller; receive a signal indicating that the breathing gas supplied by the metering device has been manually switched; and upon receiving the signal, enter a manual override mode and stop adaptive feedback control. E17. The method according to E16, further comprising: compare measured data with alarm limits; and initiate an alarm condition if the measured data are outside the alarm limits. E18. The method according to any of E16 and E17, wherein the adaptive feedback control of the breathing gas comprises adjusting the flow rate of the supplemental gas flow by actuating the supplemental valve. E19. The method according to any of E16-E18, wherein determining the PaO2 data comprises referencing a look-up table, and further comprising converting a received SpO2 value to a PaO2 value by interpolation upon determining that the received SpO2 value is not present in the look-up table. E20. The method according to E19, wherein the look-up table is derived from a sigmoidal oxyhemoglobin dissociation curve. E21. The method according to any of E6-E20, wherein the pulse oximeter data includes one or more signals indicative of a current blood oxygen level of the patient, and wherein the method further comprises: receive one or more signals indicative of the current blood oxygen level; receive indicative data on the breathing gas and supplementary gas mixture; compare the one or more signals indicative of current blood oxygen level with a target blood oxygen level; calculate an appropriate change to the mixture to achieve a change in a percentage of oxygen in the mixture; alter the percentage of oxygen in the mixture; and receive new signals indicative of the patient's current blood oxygen level. E22. The method according to any of E1-E21, further comprising: receive at least one patient carbon dioxide measurement, and control the breathing gas flow rate based on the at least one patient carbon dioxide measurement. E23. The method according to any of E6-E22, further comprising: receive oxygen data from a pulse oximeter and carbon dioxide data from a transcutaneous carbon dioxide sensor; Compare the oxygen and carbon dioxide data to a reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value; and determine whether to provide the patient with high oxygen therapy or high flush therapy. E24. The method according to E23, further comprising, when determining to provide the patient with high oxygen therapy, increasing the flow rate of the supplemental gas flow. E25. The method according to E23, further comprising, when determining to provide the patient with high lavage therapy, increasing the gas flow rate. E26. The method according to any of E1-E25, which uses the system according to any of D1-D111. F1. A method for controlling the operation of a respiratory therapy unit, the method comprising: receiving a first signal from an alignment sensor on a base unit of the respiratory therapy unit, the first signal being indicative of an alignment of the alignment sensor with an alignment marker of an auxiliary unit of the respiratory therapy unit; start the operation of the respiratory therapy unit; receiving a second signal from the alignment sensor, the second signal being indicative of poor alignment of the alignment sensor with the alignment marker; and stopping operation of the respiratory therapy unit. F2. The method according to F1, further comprising generating an alarm after receiving the second signal. F3. The method according to any of F1 and F2, wherein the alignment sensor is an RFID reader, and wherein the alignment marker is an RFID tag. F4. The method according to any of F1 and F2, wherein the alignment sensor is a Hall effect sensor, and wherein the alignment marker is a magnet. F5. The method according to any of F1-F4 using the system according to any of D1-D111. G1. A method for controlling the operation of a respiratory therapy unit, the method comprising: receiving a temperature measurement from a temperature sensor in a warming section of the respiratory therapy unit; Compare the temperature measurement with a reference temperature; if the temperature measurement is higher than the reference temperature, stop the respiratory therapy unit. G2. The method according to G1, further comprising generating an alarm if the temperature measurement is greater than the reference temperature. G3. The method according to any of G1 and G2 using the system according to any of D1-D111. H1. A method for controlling the power of a respiratory therapy unit, the method comprising: receive a first signal indicating that a removable battery has been removed from the respiratory therapy unit; changing the operation of the respiratory therapy unit from a regular power mode to a low power mode; and operating the respiratory therapy unit using a backup battery in the respiratory therapy unit. H2. The method according to H1, further comprising: receive a second signal indicating that the removable battery has been replaced in the respiratory therapy unit; Switch the respiratory therapy unit from low power mode to regular power mode; and operate the respiratory therapy unit using the replaced removable battery. H3. The method according to any of H1 and H2, wherein operating the respiratory therapy unit using the backup battery lasts at least about one hour. H4. The method according to any of H1-H3 using the system according to any of D1-D111. 11. A method for operating a respiratory therapy unit, the method comprising: receiving at least one liquid level measurement from a level sensor, the at least one liquid level measurement indicating at least one liquid level in a liquid container of the respiratory therapy unit; receiving at least one flow measurement from a flow sensor, the at least one flow measurement indicating a flow rate of respirable gas in the respiratory therapy unit; and calculating a humidity of the respirable gas based on the at least one liquid level measurement and the at least one flow measurement. I2. The method according to 11, further comprising actuating a valve based on humidity, wherein the valve controls the flow rate of the breathable gas. I3. The method according to any of 11 and I2, further comprising: comparing the calculated humidity with a reference humidity; and generating an alarm if the calculated humidity is below the reference humidity. I4. The method according to any of 11-13, further comprising: compare at least one fluid level measurement with a reference fluid level; generate an alarm; and stop operation of the respiratory therapy unit. 15. The method according to any of 11-14, wherein the level sensor is a capacitive sensor. 16. The method according to any of 11-15 using the system according to any of D1-D111. J1. A method for providing respiratory therapy to a patient using the system according to any of D1 -D111, the method comprising: expelling a flow of respirable gas from a ventilator through a conduit and into a nasal cannula; and providing the respirable gas to a nose of the patient from at least one nasal prong of the nasal cannula, the nasal cannula being in fluid communication with the conduit and configured to receive the respirable gas from the delivery tube; wherein the at least one nasal prong is configured to provide respirable gas from a distal end of the at least one nasal prong at an exit velocity of at least about 40 m / s and less than about 75 m / s. J2. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.4 mm and less than about 1.8 mm, and the ventilator has a maximum flow set point greater than or equal to about 9 L / min and less than about 28 L / min. J3. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.8 mm and less than about 1.9 mm, and the ventilator has a maximum flow set point greater than or equal to about 13 L / min and less than about 31 L / min. J4. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.9 mm and less than about 3 mm, and the ventilator has a maximum flow set point greater than or equal to about 21 L / min and less than about 60 L / min. J5. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 3 mm and less than about 4 mm, and the ventilator has a maximum flow set point greater than or equal to about 34 L / min and less than about 80 L / min. J6. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.1 mm and less than about 1.6 mm, and the nasal cannula has a pressure drop of less than about 80 hPa when the ventilator operates at a maximum flow set point of about 8 L / min. J7. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.5 mm and less than about 2 mm, and the nasal cannula has a pressure drop of less than about 100 hPa when the ventilator operates at a maximum flow set point of about 20 L / min. J8. The method according to J1, wherein the at least one nasal prong has an inner diameter greater than or equal to about 1.9 mm and less than about 3.5 mm, and the nasal cannula has a pressure drop of less than about 80 hPa when the ventilator operates at a maximum flow set point of about 40 L / min. J9. The method according to any of J1-J8, further comprising: receive the first data indicative of one or more dimensions of the nasal cannula; receiving the second data indicative of a respirable gas flow rate; and calculating the exit velocity based on the first data and the second data. J10. The method according to J9, further comprising: generate to display at least one selected from the group of: flow rate, output velocity, a maximum flow set point, and a pressure drop. J11. The method according to any of J9 and J10, comprising generating to display the flow rate and the output velocity. J12. The method according to any of J9-J11, further comprising: receive user input to increase or decrease the breathing gas flow rate; change the flow rate to a modified breathing gas flow rate; calculate a modified velocity based on the modified flow rate and the first data; and generate for display at least one selected from the group of: the modified flow rate and the modified velocity. J13. The method according to any of J1-J12, wherein the exit velocity is at least about 40 m / s and less than about 70 m / s. J14. The method according to any of J1-J12, wherein the exit velocity is at least about 40 m / s and less than about 65 m / s. J15. The method according to any of J1-J12, wherein the exit velocity is at least about 40 m / s and less than about 60 m / s. J16. The method according to any of J1-J12, wherein the exit velocity is at least about 40 m / s and less than about 55 m / s. J17. The method according to any of J1-J12, wherein the exit velocity is at least about 40 m / s and less than about 50 m / s. J18. The method according to any of J1-J12, wherein the exit velocity is at least about 40 m / s and less than about 45 m / s. J19. The method according to any of J1-J18, wherein the exit velocity is approximately 40 m / s. K1. A respiratory therapy unit comprising: a ventilator configured to expel respirable gas; a controller; a removable battery; and a backup battery. K2. The respiratory therapy unit according to K1, wherein the controller is configured to initiate a low power mode for the system when the removable battery is removed. K3. The respiratory therapy unit according to any of K1 and K2, wherein the system is configured to operate without the removable battery. K4. The respiratory therapy unit according to any of K1-K3, wherein the backup battery is configured to provide power to the ventilator and the controller. K5. The respiratory therapy unit according to K4, wherein the backup battery is configured to provide power for at least about one hour. K6. The respiratory therapy unit according to K2, wherein the low power mode allows operation of one or more alarms and the ventilator. L1. A measuring device for a respiratory therapy unit, the measuring device comprising: a first flow sensor, a second flow sensor, and a conduit in fluid communication with the respiratory therapy unit, wherein the first flow sensor and second flow sensor are positioned in series along the conduit. L2. The measuring device according to L1, wherein the duct is configured to: receive respirable gas from an inlet of the respiratory therapy unit; directing the breathing gas through the first flow sensor, wherein the first flow sensor is configured to output a first measurement of the breathing gas; directing the respirable gas through the second flow sensor, wherein the second flow sensor is configured to output a second measurement of the respirable gas; and exhausting the respirable gas to the respiratory therapy unit. L3. The measuring device according to L2, further comprising a controller operatively coupled to the respiratory therapy unit, and wherein the controller is configured to adjust a respirable gas flow rate of the ventilator based on at least one of the first measurement or the second measurement. L4. The measuring device according to any of L2 and L3, and, wherein the first flow sensor and the second flow sensor are mass flow sensors. L5. The measuring device according to any of L2-L4, wherein the controller is configured to calibrate each of the first flow sensor and the second flow sensor relative to each other. L6. The measuring device according to any of L1-L5, wherein the device conduit comprises a first segment configured to direct the respirable gas through the first flow sensor and a second segment configured to direct the respirable gas through the second flow sensor, wherein the first segment and the second segment are approximately straight. L7. The measuring device according to any of L1-L6, further comprising a supplemental gas inlet configured to receive a supplemental gas from an external gas source and add the supplemental gas to the breathing gas, wherein the supplemental gas inlet is disposed between the first flow sensor and the second flow sensor. L8. The measuring device according to L7, further comprising an inlet valve configured to control a flow rate of supplemental gas through the supplemental gas inlet. L9. The measuring device according to L8, wherein the supplementary valve is a solenoid valve. L10. The measuring device according to any of L8 and L9, wherein the first flow sensor is configured to output a first measurement of the breathing gas, and wherein the second flow sensor is configured to output a second measurement of a mixture of the breathing gas and the supplemental gas. L11. The measuring device according to L10, wherein the controller is configured to calculate a flow difference between the first measurement and the second measurement, wherein the flow difference indicates an amount of one or more components of the supplemental gas added to the breathing gas, and wherein the controller is configured to calculate one or more concentrations of one or more components in the mixture based on the flow difference and the second measurement. L12. The metering device according to L11, wherein the controller is configured to operate the inlet valve to control the added amount based on the calculated flow difference. L13. The measuring device according to L12, wherein the controller is configured to: receive as an input a target concentration, compare one or more calculated concentrations with the target concentration, and control the amount added based on the comparison. L14. The measuring device according to any of L11-L13, wherein the flow difference is less than about 5% of the first measurement. L15. The measuring device according to L14, wherein the flow difference is less than approximately 1 % of the first measurement. L16. The measuring device according to any of L7-L15, wherein the external gas source is one selected from the group of: a wall gas outlet, a gas concentrator, and a gas tank. L17. The measuring device according to any of L7-L16, wherein the supplemental gas is oxygen, oxygen-concentrated respirable gas, helium, nitric oxide, heliox, an anesthetic gas, or a gas containing aerosolized medicament. L18. The measuring device according to any of L11-L17, wherein the controller is configured to operate the supplemental valve to pause the flow of the supplemental gas and to calibrate the first flow sensor and the second flow sensor to each other while the flow of the supplemental gas is paused, wherein the calibration reduces an error of the calculated flow difference to an error of the second flow sensor. L19. The measuring device according to any of L7-L18, further comprising: one or more additional supplemental gas inlets for adding one or more additional supplemental gases; and one or more additional flow sensors, wherein the device comprises an additional flow sensor for each of the additional supplemental gas inlets. L20. The measuring device according to any of L7-L19, wherein the supplemental gas comprises oxygen, and wherein the controller is configured to adjust the flow rate of supplemental gas through the supplemental gas inlet based on pulse oximeter data. L21. The measuring device according to L20, wherein the supplemental gas flow rate is adjusted to set an oxygen concentration of the breathing gas provided to the patient at a minimum oxygen concentration that is determined to have a therapeutic effect on the patient based on pulse oximeter data. L22. The measuring device according to any of L20 and L21, wherein the pulse oximeter data includes SpÜ2 data and alarm condition signals, and wherein the controller is configured to: receive pulse oximeter data; From the SpO2 data, determine the PaO2 data to calculate an appropriate oxygen concentration of the breathing gas; performing adaptive feedback control of the breathing gas based on the SpO2 level signals via a device interface, wherein the adaptive feedback control is provided by a proportional integral derivative (PID) controller; receiving data via the gas interface including a signal indicating that the breathing gas supplied by the measuring device has been manually switched; and upon receiving the signal via the gas interface, entering a manual override mode and ceasing to send adaptive feedback control signals to the device interface. L23. The measuring device according to L22, wherein the controller is configured to compare measurement data with alarm limits and to initiate an alarm condition if the measured data are outside the alarm limits. L24. The metering device according to any of L22 and L23, wherein the device interface is operatively coupled to the supplemental valve, and wherein the adaptive feedback control of the breathing gas comprises adjusting the flow rate of supplemental gas through the supplemental gas inlet by actuating the supplemental valve. L25. The measuring device according to any of L22-L24, wherein the controller comprises a memory configured to store a look-up table, wherein the controller determines the PaO2 data by referencing the look-up table, and wherein the controller is configured to convert a received SpO2 value to a PaO2 value by interpolation upon determining that the received SpO2 value is not present in the look-up table. L26. The measuring device according to L25, wherein the look-up table is derived from a sigmoidal oxyhemoglobin dissociation curve. L27. The measuring device according to any of L20-L26, wherein the pulse oximeter data includes one or more signals indicative of a current blood oxygen level of the patient, and wherein the controller is configured to: receive via a pulse oximeter interface one or more signals indicative of the current blood oxygen level; receive via device interface data indicative of the breathing gas and supplemental gas mixture; compare the one or more signals indicative of current blood oxygen level with a target blood oxygen level; calculate an appropriate change to the mixture to achieve a change in a percentage of oxygen in the mixture; alter the percentage of oxygen in the mixture by actuating the supplemental valve; and receive new signals from the pulse oximeter interface indicative of the patient's current blood oxygen level. L28. The measuring device according to any of L7-L27, wherein the controller is configured to: receive, via the one or more interfaces, oxygen data from a pulse oximeter and carbon dioxide data from a transcutaneous carbon dioxide sensor; Compare the oxygen and carbon dioxide data to a reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value; and determine whether to provide the patient with high oxygen therapy or high flush therapy. L29. The metering device according to L28, wherein the controller is further configured to, upon determining to provide the patient with high oxygen therapy, increase the flow rate of the supplemental gas through the supplemental gas inlet by actuating the supplemental valve. L30. The measuring device according to L28, wherein the controller is further configured to, upon determining to provide the patient with high flush therapy, increase the ventilator breathing gas flow rate. M1. A respiratory therapy system comprising: an auxiliary unit having a heating section and a heating plate disposed in the heating section; and a base unit having a heat actuator configured to be operatively coupled to the heating plate and not in contact with the heating plate. M2. The respiratory therapy system according to M1, wherein the heat actuator is a coil configured to induce a current in the heating plate. M3. The respiratory therapy system according to M2, wherein the induced current generates heat on the heating plate due to a resistance of the heating plate. M4. The respiratory therapy system according to any of M1-M3, wherein the heating plate is configured to be immersed in a liquid within the auxiliary unit and heat the liquid. M5. The respiratory therapy system according to any of M1-M4, wherein the heating plate does not contact an external surface of the auxiliary unit. M6. The respiratory therapy system according to any of M1-M5, wherein the heating plate comprises a protruding tab, and wherein the base unit comprises a temperature sensor configured to output a temperature measurement of the protruding tab. M7. The respiratory therapy system according to M6, wherein the controller is configured to receive the temperature measurement and compare the temperature measurement with a reference temperature. M8. The respiratory therapy system according to M7, wherein, based on comparing the temperature measurement with the reference temperature, the controller is configured to at least one of stopping the operation of the respiratory therapy system or generating an alarm. M9. The respiratory therapy system according to any of M1-M8, wherein the actuator is configured to operate while the respiratory therapy unit operates without an external power supply. M10. The respiratory therapy system according to any of M1-M9, wherein the heating plate is specific in orientation relative to the heat actuator. N1. A respiratory therapy system comprising: a base unit configured to expel respirable gas; and an auxiliary unit configured to receive the expelled respirable gas, the auxiliary unit comprising: a liquid container; and a vapor transfer cartridge (VTC) configured to humidify the breathing gas; wherein the liquid container comprises an outlet conduit in fluid communication with a cartridge inlet of the VTC. N2. The respiratory therapy system according to N1, wherein the base unit comprises a level sensor configured to output at least one liquid level measurement indicating a liquid level in the liquid container. N3. The respiratory therapy system according to N2, further comprising a controller, wherein the controller is configured to: receive at least one liquid level measurement from the level sensor; calculate an outlet humidity of the VTC based at least in part on at least one liquid level measurement. N4. The respiratory therapy system according to N3, further comprising a gas valve configured to actuate a gas flow rate of the respirable gas exhausted from the base unit to the auxiliary unit, wherein the controller is configured to control the gas valve based on the output humidity. N5. The respiratory therapy system according to any of N2-N4, wherein the controller is configured to compare the at least one liquid level measurement with a reference liquid level and at least one of generating an alarm or stopping the operation of the system. N6. The respiratory therapy system according to any of N2-N5, wherein the level sensor is a capaciti...

Claims

1. A system for providing respiratory therapy to a patient, the system comprising: a ventilator configured to: receive breathable gas from ambient air, a tank, or a wall outlet; and expel pressurized breathable gas; a conduit in fluid communication with the ventilator, wherein the conduit receives breathable gas from the ventilator and expels breathable gas at a first pressure; and a nasal cannula having at least one nasal tip, the nasal cannula being in fluid communication with the conduit and configured to receive breathable gas from the conduit at the first pressure, the at least one nasal tip being configured to deliver breathable gas to one of the patient's nostrils; wherein the nasal tip is configured to deliver breathable gas at an outlet velocity of at least approximately 40 m / s and less than approximately 75 m / s.

2. The system according to claim 1, wherein a nasal tip has an inside diameter greater than or equal to approximately 1.4 mm and less than approximately 1.8 mm, and the system has a maximum flow set point greater than or equal to approximately 9 L / min and less than approximately 28 L / min.

3. The system according to claim 1, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.8 mm and less than approximately 1.9 mm, and the system has a maximum flow set point greater than or equal to approximately 13 L / min and less than approximately 31 L / min.

4. The system according to claim 1, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.9 mm and less than approximately 3 mm, and the system has a maximum flow set point greater than or equal to approximately 21 L / min and less than approximately 60 L / min.

5. The system according to claim 1, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 3 mm and less than approximately 4 mm, and the system has a maximum flow set point greater than or equal to approximately 34 L / min and less than approximately 80 L / min.

6. The system according to claim 1, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.1 mm and less than approximately 1.6 mm, and the nasal cannula has a pressure drop of less than approximately 80 hPa when operated at a maximum flow set point of approximately 8 L / min.

7. The system according to claim 1, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.5 mm and less than approximately 2 mm, and the nasal cannula has a pressure drop of less than approximately 100 hPa when operated at a maximum flow set point of approximately 20 L / min.

8. The system according to claim 1, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.9 mm and less than approximately 3.5 mm, and the nasal cannula has a pressure drop of less than approximately 80 hPa when operated at a maximum flow set point of approximately 40 L / min.

9. The system according to any of claims 1 to 8, further comprising a controller and a processor configured to: receive first data indicative of one or more dimensions of the nasal cannula; receive second data indicative of a breathable gas flow rate; and calculate the exit velocity based on the first and second data.

10. The system according to claim 9, further comprising a display, and wherein the processor is further configured to generate and display at least one of: the flow rate, the outlet velocity, a maximum flow set point, and a pressure drop.

11. The system according to any of claims 9 and 10, wherein the fan, controller and processor are housed in a base unit, the system further comprises an attachable unit configured to connect reversibly to the base unit.

12. The system according to claim 11, wherein the conduit is configured to connect reversibly to the attachable unit, wherein the nasal cannula is configured to connect reversibly to the conduit, and wherein the processor receives the first data when the attachable unit is connected to the base unit.

13. The system according to claim 12, wherein the processor receives the first data from an RFID tag within the attachable unit.

14. The system according to claim 9, wherein the first data comprise an inner diameter of at least one nasal tip.

15. The system according to claim 9, wherein the processor is configured to identify the nasal cannula based on the initial data.

16. The system according to any of claims 9 to 15, further comprising at least one sensor configured to measure the breathing gas flow rate and send the second data to the processor.

17. The system according to any of claims 9 to 16, wherein the processor is further configured to receive user input to change at least one of: the breathing gas flow rate to a modified breathing gas flow rate, or the outlet velocity to a modified velocity.

18. The system according to claim 17, wherein the controller is configured to change the breathable gas flow rate to the modified flow rate based on user input.

19. The system according to any of claims 17 and 18, wherein the processor is further configured to calculate a modified speed based on the modified flow rate and the first data.

20. A method for providing respiratory therapy to a patient, the method comprising: expelling a flow of breathable gas from a ventilator through a conduit and into a nasal cannula 108; and delivering the breathable gas to one of the patient's noses from at least one nasal tip of the nasal cannula, the nasal cannula being in fluid communication with the conduit and configured to receive the breathable gas from the conduit; wherein the at least one nasal tip is configured to deliver breathable gas from a distal end of the at least one nasal tip at an outlet velocity of at least approximately 40 m / s and less than approximately 75 m / s.

21. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.4 mm and less than approximately 1.8 mm, and the fan has a maximum flow set point greater than or equal to approximately 9 L / min and less than approximately 28 L / min.

22. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.8 mm and less than approximately 1.9 mm, and the ventilator has a maximum flow set point greater than or equal to approximately 13 L / min and less than approximately 31 L / min.

23. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.9 mm and less than approximately 3 mm, and the fan has a maximum flow set point greater than or equal to approximately 21 L / min and less than approximately 60 L / min.

24. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 3 mm and less than approximately 4 mm, and the ventilator has a maximum flow set point greater than or equal to approximately 34 L / min and less than approximately 80 L / min.

25. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.1 mm and less than approximately 1.6 mm, and the nasal cannula has a pressure drop of less than approximately 80 hPa when the ventilator operates at a maximum flow set point of approximately 8 L / min.

26. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.5 mm and less than approximately 2 mm, and the nasal cannula has a pressure drop of less than approximately 100 hPa when the ventilator operates at a maximum flow set point of approximately 20 L / min.

27. The method according to claim 20, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.9 mm and less than approximately 3.5 mm, and the nasal cannula has a pressure drop of less than approximately 80 hPa when the ventilator operates at a maximum flow set point of approximately 40 L / min.

28. The method according to any of claims 20 to 27, further comprising: receiving first data indicative of one or more dimensions of the nasal cannula; 109 receiving second data indicative of a respirable gas flow rate; and calculating the exit velocity based on the first and second data.

29. The method according to claim 28, comprising: generating to display at least one selected from the group of: the flow rate, the outlet velocity, a maximum flow set point, and a pressure drop.

30. The method according to any of claims 28 and 29, comprising: generating to visualize the flow rate and the outlet velocity.

31. The method according to any of claims 28 to 30, further comprising: receiving a user input to increase or decrease the breathing gas flow rate; changing the flow rate to a modified breathing gas flow rate; calculating a modified velocity based on the modified flow rate and the initial data; and generating for display at least one selected from the group of: the modified flow rate and the modified velocity.

32. The system or method according to any of claims 1 to 31, wherein the breathing gas is configured to be humidified and heated.

33. The system or method according to any of claims 1 to 32, wherein the exit velocity is at least about 40 m / s and less than about 70 m / s.

34. The system or method according to any of claims 1 to 33, wherein the exit velocity is at least about 40 m / s and less than about 65 m / s.

35. The system or method according to any of claims 1 to 34, wherein the exit velocity is at least about 40 m / s and less than about 60 m / s.

36. The system or method according to any of claims 1 to 35, wherein the exit velocity is at least about 40 m / s and less than about 55 m / s.

37. The system or method according to any of claims 1 to 36, wherein the exit velocity is at least about 40 m / s and less than about 50 m / s.

38. The system or method according to any of claims 1 to 37, wherein the exit velocity is at least about 40 m / s and less than about 45 m / s.

39. The system or method according to any of claims 1 to 38, wherein the exit velocity is at least about 40 m / s.

40. A system for providing respiratory therapy to a patient, the system comprising: a base unit comprising: a ventilator configured to expel breathable gas; and a controller; an auxiliary unit configured to be reversibly coupled to the base unit, wherein the auxiliary unit comprises an auxiliary unit outlet; and a delivery tube configured to receive breathable gas from the auxiliary unit outlet and deliver the breathable gas to the patient. 110 41. The system according to claim 40, wherein the base unit further comprises a measuring device comprising: a first flow sensor, a second flow sensor, and a device duct in fluid communication with the fan, wherein the first flow sensor and second flow sensor are positioned in series along the duct.

42. The system according to claim 41, wherein the device conduit is configured to: receive breathing gas from a gas inlet of the base unit; direct the breathing gas through the first flow sensor, wherein the first flow sensor is configured to emit a first measurement of the breathing gas; direct the breathing gas through the second flow sensor, wherein the second flow sensor is configured to emit a second measurement of the breathing gas; and expel the breathing gas to the ventilator.

43. The system according to claim 42, wherein the controller is configured to adjust a ventilator breathing gas flow rate based on at least one of the first or second measurements.

44. The system according to any of claims 41 to 43, wherein the first flow sensor and the second flow sensor are mass flow sensors.

45. The system according to any of claims 41 to 44, wherein the first flow sensor and the second flow sensor are each configured to be calibrated relative to each other.

46. ​​The system according to any of claims 41 to 45, wherein the device conduit comprises a first segment configured to direct breathable gas through the first flow sensor and a second segment configured to direct breathable gas through the second flow sensor, wherein the first segment and the second segment are approximately straight.

47. The system according to any of claims 41 to 46, wherein the system comprises a supplementary gas inlet configured to receive supplementary gas from an external gas source and add the supplementary gas to the breathable gas, wherein the supplementary gas inlet is in fluid communication with the device duct and is disposed between the first flow sensor and the second flow sensor.

48. The system according to claim 47, further comprising an additional valve configured to control the flow of additional gas through the additional gas inlet.

49. The system according to claim 48, wherein the supplementary valve is a solenoid valve.

50. The system according to any of claims 48 and 49, wherein the first flow sensor is configured to emit a first measurement of the breathing gas, and wherein the second flow sensor is configured to emit a second measurement of a mixture of the breathing gas and the supplemental gas.

51. The system according to claim 50, wherein the controller is configured to calculate a flow difference between the first measurement and the second measurement, wherein the flow difference indicates an amount of one or more supplemental gas components added to the breathing gas, and wherein the controller is configured to calculate one or more concentrations of one or more components in the mixture based on the flow difference and the second measurement.

52. The system according to claim 51, wherein the controller is configured to operate the supplementary valve to control the added quantity based on the calculated flow difference.

53. The system according to claim 52, wherein the controller is configured to: receive a blank concentration as an input, compare one or more calculated concentrations with the blank concentration, and control the amount added based on the comparison.

54. The system according to any of claims 51 to 53, wherein the flow difference is less than approximately 5% of the first measurement.

55. The system according to claim 54, wherein the flow difference is less than approximately 1% of the first measurement.

56. The system according to any of claims 47 to 55, wherein the external gas source is one selected from the group of: a wall gas outlet, a gas concentrator, and a gas tank.

57. The system according to any of claims 47 to 56, wherein the supplemental gas is oxygen, oxygen-concentrated breathing gas, helium, nitric oxide, heliox, an anesthetic gas, or a gas containing aerosolized medication.

58. The system according to any of claims 47 to 57, wherein the controller is configured to operate the supplementary valve to pause the flow of the supplementary gas and to calibrate the first flow sensor and the second flow sensor to each other while the flow of the supplementary gas is paused, wherein the calibration reduces an error of the calculated flow difference to an error of the second flow sensor.

59. The system according to any of claims 47 to 58, further comprising: one or more additional supplementary gas inlets for adding one or more additional supplementary gases; and one or more additional flow sensors, wherein the device comprises an additional flow sensor for each of the additional supplementary gas inlets.

60. The system according to any of claims 40 to 59, wherein the base unit may comprise a seat configured to receive the auxiliary unit when the auxiliary unit is coupled to the base unit. 112 61. The system according to claim 60, wherein the base unit comprises at least one alignment sensor, and the auxiliary unit comprises at least one alignment marker.

62. The system according to claim 61, wherein the at least one alignment sensor is configured to transmit a first signal to the controller when the at least one alignment marker aligns with the at least one alignment sensor.

63. The system according to any of claims 61 to 62, wherein the at least one alignment sensor is configured to transmit a second signal to the controller when the at least one alignment marker is not aligned with the at least one alignment sensor.

64. The system according to claim 63, wherein the controller is configured to stop the operation of the system when the controller receives the second signal.

65. The system according to any of claims 63 to 64, wherein the controller generates an alarm when the controller receives the second signal.

66. The system according to claim 65, wherein the alignment of at least one alignment marker with at least one alignment sensor indicates that the auxiliary unit is fully seated in the seat.

67. The system according to any of claims 60 to 66, wherein the auxiliary unit comprises a spring return configured to eject the auxiliary unit from the seat.

68. The system according to any of claims 60 to 67, wherein the auxiliary unit comprises at least one tab configured to lock into a depression in the seat.

69. The system according to any of claims 61 to 68, wherein the at least one alignment marker is a magnet, and the at least one alignment sensor is a Hall effect sensor.

70. The system according to any of claims 61 to 68, wherein the at least one alignment marker is an RFID tag, and the at least one alignment sensor is an RFID reader.

71. The system according to claim 70, wherein the RFID tag comprises information about the auxiliary unit.

72. The system according to claim 71, wherein the information includes at least one selected from the group of: a usage history of the auxiliary unit, a lifetime of the auxiliary unit, a remaining lifetime of the auxiliary unit, one or more functionalities of the auxiliary unit, integrated license, and recommended operating parameters.

73. The system according to claim 72, wherein one or more functionalities are selected, at least one of the following groups: low flow, high flow, aerosolization, humidification, oxygenation, nitric oxide, helium, and closed-loop oxygen control.

74. The system according to any of claims 71 to 73, wherein the controller is configured to adjust a range of acceptable flow rates of the respirable gas based on the information.

75. The system according to any of claims 40 to 74, wherein the base unit further comprises a heat exchanger configured to cool the breathing gas expelled from the fan. 113 76. The system according to claim 75, wherein the heat exchanger is configured to disperse heat radially from the expelled breathing gas.

77. The system according to any of claims 75 and 76, wherein the heat exchanger is configured to decrease the breathable gas temperature of the expelled breathable gas to a white breathable gas temperature.

78. The system according to any of claims 40 to 77, wherein the auxiliary unit is configured to be reversibly coupled to the base unit via one or more couplings, at least one of the one or more couplings being configured to allow fluid communication of the breathing gas from the base unit to the auxiliary unit.

79. The system according to claim 78, wherein the at least one coupling configured to allow fluid communication is an occlusion valve.

80. The system according to claim 79, wherein the occlusion valve is operatively coupled to the controller, and wherein the occlusion valve is configured to simultaneously control the expelled breathing gas and a liquid flow.

81. The system according to claim 80, wherein the occlusion valve is configured to receive the fluid flow from an external fluid supply and direct the fluid flow towards the auxiliary unit.

82. The system according to any of claims 80 to 81, wherein the occlusion valve is configured to receive the breathing gas expelled from the ventilator and direct the breathing gas towards the auxiliary unit.

83. The system according to any of claims 79 to 82, wherein the shut-off valve comprises: an air path valve seal; a bellows; and a valve actuator; wherein the valve actuator is configured to expand and contract the bellows and raise and lower the air path valve seal.

84. The system according to claim 83, wherein the valve actuator is a linearly driven rod.

85. The system according to any of claims 83 to 84, wherein the controller is configured to position the valve actuator in one of at least three actuator positions, and wherein the valve actuator is configured to position the air path valve seal in one of at least three air path positions.

86. The system according to any of claims 83 to 85, wherein the occlusion valve further comprises a gas seal, which forms an annular space around the air path valve seal.

87. The system according to any of claims 83 to 86, wherein the occlusion valve further comprises a flexible diaphragm, wherein the air path valve seal 114 actuates the flexible diaphragm to be in one of at least three diaphragm positions by abutting the flexible diaphragm when the air path valve seal is lifted by the valve actuator.

88. The system according to any of claims 85 to 87, wherein the at least three actuator positions include a retracted position, a partially extended position, and a fully extended position.

89. The system according to claim 88, wherein the retracted position blocks breathing gas and allows liquid flow, wherein the partially extended position allows both breathing gas and liquid flow through the occlusion valve, and wherein the fully extended position allows breathing gas through the occlusion valve and blocks liquid flow.

90. The system according to any of claims 88 to 89, wherein when the valve actuator is in the fully extended position, the flexible diaphragm occludes an outlet of a liquid inlet tube.

91. The system according to any of claims 88 to 90, wherein the controller is configured to position the valve actuator in the partially extended position or the fully extended position when the controller receives the first signal.

92. The system according to any of claims 88 to 91, wherein the controller is configured to position the valve actuator in the retracted position when the controller receives the second signal.

93. The system according to any of claims 88 to 92, wherein when the valve actuator is in the retracted position, the air path valve seal prevents fluid from entering the base unit.

94. The system according to any of claims 40 to 93, wherein the auxiliary unit comprises a liquid container and a vapor transfer cartridge (VTC) configured to humidify the breathing gas, wherein the liquid container comprises an outlet conduit in fluid communication with a cartridge inlet of the VTC.

95. The system according to claim 94, wherein the base unit comprises a level sensor operatively coupled to the controller and configured to emit at least one liquid level measurement indicating a liquid level in the liquid container.

96. The system according to claim 95, wherein the controller is configured to calculate an outlet humidity of the VTC based on at least one liquid level measurement and at least one flow measurement.

97. The system according to claim 96, wherein the controller is configured to adjust the valve actuator based on the outlet humidity.

98. The system according to any of claims 95 to 97, wherein the controller is configured to compare at least one liquid level measurement with a reference liquid level and at least one to generate an alarm or stop the operation of the system.

99. The system according to any of claims 95 to 98, wherein the level sensor is a capacitive sensor.

100. The system according to any of claims 40 to 99, wherein the auxiliary unit comprises a heating plate in a heating section, and wherein the base unit comprises a heat actuator configured to be operatively coupled to the heating plate and not in contact with the heating plate.

101. The system according to claim 100, wherein the heat actuator is a coil configured to induce a current in the heating plate.

102. The system according to claim 101, wherein the induced current generates heat in the heating plate due to a resistance of the heating plate.

103. The system according to any of claims 100 to 102, wherein the heating plate is configured to be submerged within the auxiliary unit and to heat the liquid.

104. The system according to any of claims 100 to 103, wherein the heating plate does not contact an external surface of the auxiliary unit.

105. The system according to any of claims 100 to 104, wherein the heating plate comprises a protruding tab, and wherein the base unit comprises a temperature sensor configured to emit a temperature measurement of the protruding tab.

106. The system according to claim 105, wherein the controller is configured to receive the temperature measurement and compare the temperature measurement with a reference temperature.

107. The system according to claim 106, wherein, based on comparing the temperature measurement with the reference temperature, the controller is configured to at least one of either stop the operation of the system or generate an alarm.

108. The system according to any of claims 100 to 107, wherein the actuator is configured to operate while the system operates without an external power supply.

109. The system according to any of claims 100 to 108, wherein the heating plate is specifically oriented with respect to the heat actuator.

110. The system according to any of claims 40 to 109, wherein the auxiliary unit comprises a pump configured to pump the liquid in the auxiliary unit.

111. The system according to claim 110, wherein the pump comprises a rotor cup, and wherein the base unit comprises a stator configured to magnetically couple to the rotor cup.

112. The system according to any of claims 110 to 111, wherein the pump is configured to pump the liquid through a liquid circuit of the auxiliary unit, wherein a bolus of the liquid in the liquid circuit travels sequentially through the pump, the jacket, the VTC, the liquid vessel, and the heating section.

113. The system according to any of claims 40 to 112, wherein the supply tube comprises a jacket in fluid communication with the auxiliary unit and a gas conduit in fluid communication with the VTC. 116 114. The system according to claim 113, wherein the pump is configured to pump the liquid from the heating section to the jacket of the supply tube.

115. The system according to claim 114, wherein the jacket is configured to transmit heat from the liquid in the jacket to the breathable gas in the gas duct.

116. The system according to any of claims 94 to 115, wherein a VTC temperature of the VTC is lower than a supply temperature of the breathing gas in the gas duct.

117. The system according to claim 116, wherein the supply temperature is higher than a dew point of the breathing gas in the supply tube.

118. The system according to any of claims 113 to 117, wherein the supply tube comprises one or more radial ribs extending through the jacket.

119. The system according to claim 118, wherein one or more radial ribs prevent twisting or blockage of the gas conduit when the supply tube is bent.

120. The system according to any of claims 113 to 119, wherein the controller is configured to operate the pump to control a liquid jacket flow rate in the jacket.

121. The system according to any of claims 113 to 120, wherein the jacket comprises: a first section configured to receive the liquid from the auxiliary unit and transmit the liquid to a distal end of the supply tube, and a second section configured to receive the liquid from the first section and transmit the liquid to the auxiliary unit, wherein the jacket is configured so that liquid flows through the first section and through the second section in opposite directions.

122. The system according to any of claims 40 to 121, wherein the breathable gas expelled by the fan is characterized by a gas velocity configured to prevent the accumulation of liquid in the supply tube.

123. The system according to any of claims 40 to 122, further comprising a nasal cannula configured to be attached to a patient-close end of the delivery tube, wherein the nasal cannula is configured to direct the breathable gas into at least one of the patient's nostrils.

124. The system according to any of claims 40 to 123, wherein the auxiliary unit outlet has a bell shape configured to: allow bending of the supply tube at the auxiliary unit outlet, prevent twisting of the supply tube at the auxiliary unit outlet, or prevent dislodgement of the supply tube at the auxiliary unit outlet.

125. The system according to any of claims 113 to 124, wherein the auxiliary unit comprises a supply connector configured to connect a VTC outlet cap to the 117 gas conduit and a pump outlet to the jacket.

126. The system according to any of claims 40 to 125, wherein the auxiliary unit comprises a housing configured to confine breathable gas and liquid within the auxiliary unit.

127. The system according to any of claims 40 to 126, wherein the base unit comprises a removable battery and a backup battery.

128. The system according to claim 127, wherein the controller is configured to initiate a low-power mode for the system when the removable battery is removed.

129. The system according to any of claims 127 to 128, wherein the system is configured to operate without the removable battery.

130. The system according to any of claims 127 to 129, wherein the backup battery is configured to supply power to the fan and the controller.

131. The system according to claim 130, wherein the backup battery is configured to provide power for at least approximately one hour.

132. The system according to any of claims 128 to 131, wherein the lowest power mode permits the operation of one or more alarms and the fan.

133. The system according to any of claims 40 to 132, wherein the base unit comprises one or more interfaces configured to operationally couple one or more external devices to the controller.

134. The system according to claim 133, wherein one or more external devices include a pulse oximeter configured to transmit data to the controller.

135. The system according to claim 134, wherein the controller is configured for closed-loop patient oxygen control based on pulse oximeter data.

136. The system according to any of claims 134 to 135, wherein the controller is configured to adjust the supplemental gas flow rate through the supplemental gas inlet based on pulse oximeter data, wherein the supplemental gas comprises oxygen.

137. The system according to claim 136, wherein the supplemental gas flow rate is adjusted to set an oxygen concentration of the breathable gas supplied to the patient to a minimum oxygen concentration determined to have a therapeutic effect on the patient based on pulse oximeter data.

138. The system according to any of claims 134 to 135, wherein the pulse oximeter data includes SpO2 data and alarm condition signals, and wherein the controller is configured to: receive pulse oximeter data through a pulse oximeter interface; from the SpO2 data, determine PaO2 data for calculating an appropriate oxygen concentration of the breathing gas; effect adaptive feedback control of the breathing gas based on the SpO2 level signals by means of a gas interface, wherein the adaptive feedback control is provided by a proportional-integer derivative (PID) controller; receive data via the gas interface which includes a signal indicating that the breathing gas supplied by the measuring device has been manually changed;and upon receiving the signal via the gas interface, enter a manual override mode and stop sending adaptive feedback control signals to the gas interface.

139. The system according to claim 138, wherein the controller is configured to compare measurement data with alarm limits and to initiate an alarm condition if the measured data is outside the alarm limits.

140. The system according to any of claims 138 to 139, wherein the gas interface is operatively coupled to the supplementary valve, and wherein the adaptive feedback control of the breathing gas comprises adjusting the supplementary gas flow rate through the supplementary gas inlet by actuating the supplementary valve.

141. The system according to any of claims 138 to 140, wherein the controller comprises a memory configured to store a lookup table, wherein the controller determines the PaO2 data by referencing the lookup table, and wherein the controller is configured to convert a received SpO2 value to a PaO2 value by interpolation upon determining that the received SpO2 value is not present in the lookup table.

142. The system according to claim 141, wherein the lookup table is derived from a sigmoidal-shaped oxyhemoglobin dissociation curve.

143. The system according to any of claims 134 to 142, wherein the pulse oximeter data includes one or more signals indicative of the patient's current blood oxygen level, and wherein the controller is configured to: receive via a pulse oximeter interface the one or more signals indicative of the current blood oxygen level; receive via a gas interface data indicative of the breathing gas and supplemental gas mixture; compare the one or more signals indicative of the current blood oxygen level with a target blood oxygen level; calculate an appropriate change to the mixture to achieve a change in a percentage of oxygen in the mixture; alter the percentage of oxygen in the mixture by actuating the supplemental valve; and receive further signals from the pulse oximeter interface indicative of the patient's current blood oxygen level.

144. The system according to any of claims 134 to 143, wherein the one or more external devices include a transcutaneous carbon dioxide sensor configured to output to the controller at least one measurement of the patient's carbon dioxide.

145. The system according to claim 144, wherein the controller is configured for closed-loop control of patient carbon dioxide based on at least one patient carbon dioxide measurement.

146. The system according to any of claims 134 to 145, wherein the one or more external devices includes a pulse oximeter and a transcutaneous carbon dioxide sensor, wherein the pulse oximeter is configured to output oxygen data to the controller, and wherein the transcutaneous carbon dioxide sensor is configured to output carbon dioxide data to the controller.

147. The system according to claim 146, wherein the controller is configured to: receive, via one or more interfaces, oxygen data from the pulse oximeter and carbon dioxide data from the transcutaneous carbon dioxide sensor; compare the oxygen data and carbon dioxide data with a reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value; and determine to provide the patient with high oxygen therapy or high washout therapy.

148. The system according to claim 147, wherein the controller is further configured to, when determining to provide the patient with high oxygen therapy, increase the flow rate of the supplemental gas through the supplemental gas inlet by actuating the supplemental valve.

149. The system according to claim 147, wherein the controller is further configured to, when determining to provide the patient with high washout therapy, increase the ventilator's respirable gas flow rate.

150. The system according to any of claims 40 to 149, wherein the base unit comprises a front computer operatively coupled to the controller and a display operatively coupled to the front computer.

151. A method for measuring the flow of breathable gas in a respiratory therapy device, the method comprising: generating a first measurement of the breathable gas flow using a first flow sensor; generating a second measurement of the breathable gas flow using a second flow sensor; and adjusting one or more parameters of the respiratory therapy device based on at least one of the flow measurements or the second measurement.

152. The method according to claim 151, wherein the first flow sensor and the second flow sensor are mass flow sensors, and the first measurement and the second measurement indicate mass flow rates of the breathable gas flow.

153. The method according to any of claims 151 to 152, wherein adjusting one or more parameters comprises adjusting a gas flow rate of the breathable gas flow based on the second measurement.

154. The method according to claim 153, wherein adjusting the gas flow rate comprises controlling a fan configured to expel the breathable gas flow.

155. The method according to any of claims 151 to 154, comprising further calibrating each of the first flow sensor and the second flow sensor relative to each other.

156. The method according to any of claims 151 to 155, further comprising mixing the breathable gas flow with supplementary gas flow to form a mixed flow after taking the first measurement.

157. The method according to claim 156, further comprising calculating a flow difference between the first measurement and the second measurement, wherein the second measurement is indicative of mixed flow.

158. The method according to claim 157, further comprising calculating a concentration of one or more components of the mixed flow based on the flow difference and the second measurement.

159. The method according to claim 158, further comprising: receiving a blank concentration as an input, and comparing the concentration with the blank concentration.

160. The method according to claim 159, wherein adjusting one or more parameters comprises adjusting a flow rate of the supplemental gas flow based on comparing the concentration with the blank concentration.

161. The method according to claim 160, wherein adjusting the supplemental gas flow rate comprises actuating a solenoid valve.

162. The method according to any of claims 157 to 161, wherein the flow differences are less than approximately 1% of the first measurement.

163. The method according to any of claims 157 to 162, further comprising: pausing the flow of the supplementary gas; and calibrating the first flow sensor and the second flow sensor to each other while the flow of the supplementary gas is paused, wherein calibrating reduces an error of the calculated flow difference to an error of the second flow sensor.

164. The method according to any of claims 156 to 163, further comprising: receiving pulse oximeter data from a pulse oximeter; and adjusting the flow rate of the supplemental gas flow based on the pulse oximeter data, wherein the supplemental gas comprises oxygen.

165. The method according to claim 164, further comprising: determining a minimum oxygen concentration that has a therapeutic effect on the patient based on pulse oximeter data; and adjusting the flow rate of the supplemental gas flow by adjusting an oxygen concentration of the breathable gas.

166. The method according to any one of claims 164 to 165, wherein the pulse oximeter data includes SpO2 data and alarm condition signals, and further comprising: 121 determining PaO2 data from the SpO2 data; calculating an appropriate oxygen concentration of the breathing gas; effecting adaptive feedback control of the breathing gas based on the SpO2 level signals, wherein the adaptive feedback control is provided by a proportional-integral derivative (PID) controller; receiving a signal indicating that the breathing gas supplied by the measuring device has been manually changed; and upon receiving the signal, entering a manual override mode and stopping the adaptive feedback control.

167. The method according to claim 166, further comprising: comparing the measured data with alarm limits; and initiating an alarm condition if the measured data is outside the alarm limits.

168. The method according to any of claims 166 to 167, wherein the adaptive feedback control of the breathing gas comprises adjusting the flow rate of the supplemental gas flow when actuating the supplemental valve.

169. The method according to any of claims 166 to 168, wherein determining the PaO2 data comprises referencing a lookup table, and further comprises converting a received SpO2 value to a PaO2 value by interpolation upon determining that the received SpO2 value is not present in the lookup table.

170. The method according to claim 169, wherein the lookup table is derived from a sigmoidal-shaped oxyhemoglobin dissociation curve.

171. The method according to any one of claims 156 to 170, wherein the pulse oximeter data include one or more signals indicative of the patient's current blood oxygen level, and wherein the method further comprises: receiving the one or more signals indicative of the current blood oxygen level; receiving data indicative of the breathing gas and supplemental gas mixture; comparing the one or more signals indicative of the current blood oxygen level with a target blood oxygen level; calculating an appropriate change to the mixture to achieve a change in the percentage of oxygen in the mixture; altering the percentage of oxygen in the mixture; and receiving further signals indicative of the patient's current blood oxygen level.

172. The method according to any of claims 151 to 171, further comprising: receiving at least one patient carbon dioxide measurement, and controlling the respirable gas flow rate based on the at least one patient carbon dioxide measurement.

173. The method according to any of claims 156 to 172, further comprising: receiving oxygen data from a pulse oximeter and carbon dioxide data from a transcutaneous carbon dioxide sensor; comparing the oxygen data and carbon dioxide data with a reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value; and determining to provide the patient with high oxygen therapy or high washout therapy.

174. The method according to claim 173, further comprising, in order to provide the patient with high oxygen therapy, increasing the flow rate of the supplemental gas flow.

175. The method according to claim 173, further comprising, when determining to provide the patient with high washout therapy, increasing the gas flow rate.

176. The method according to any of claims 151 to 175 using the system according to any of claims 40 to 150.

177. A method for controlling the operation of a respiratory therapy unit, the method comprising: receiving a first signal from an alignment sensor in a base unit of the respiratory therapy unit, the first signal being indicative of alignment of the alignment sensor with an alignment marker of an auxiliary unit of the respiratory therapy unit; starting the operation of the respiratory therapy unit; receiving a second signal from the alignment sensor, the second signal being indicative of misalignment of the alignment sensor with the alignment marker; and stopping the operation of the respiratory therapy unit.

178. The method according to claim 177, further comprising generating an alarm after receiving the second signal.

179. The method according to any of claims 177 to 178, wherein the alignment sensor is an RFID reader, and wherein the alignment marker is an RFID tag.

180. The method according to any of claims 177 to 178, wherein the alignment sensor is a Hall effect sensor, and wherein the alignment marker is a magnet.

181. The method according to any of claims 177 to 180 using the system according to any of claims 40 to 150.

182. A method for controlling the operation of a respiratory therapy unit, the method comprising: receiving a temperature measurement from a temperature sensor in a heating section of the respiratory therapy unit; comparing the temperature measurement with a reference temperature; and if the temperature measurement is higher than the reference temperature, stopping the operation of the respiratory therapy unit. 123 183. The method according to claim 182, further comprising generating an alarm if the temperature measurement is higher than the reference temperature.

184. The method according to any of claims 182 to 183 using the system according to any of claims 40 to 150.

185. A method for controlling the power of a respiratory therapy unit, the method comprising: receiving a first signal indicating that a removable battery has been removed from the respiratory therapy unit; changing the operation of the respiratory therapy unit from a regular power mode to a low power mode; and operating the respiratory therapy unit using a backup battery in the respiratory therapy unit.

186. The method according to claim 185, further comprising: receiving a second signal indicating that the removable battery has been replaced in the respiratory therapy unit; changing the operation of the respiratory therapy unit from low power mode to regular power mode; and operating the respiratory therapy unit using the replaced removable battery.

187. The method according to any of claims 185 to 186, wherein operating the respiratory therapy unit using the backup battery lasts at least approximately one hour.

188. The method according to any of claims 185 to 187 using the system according to any of claims 40 to 150.

189. A method for operating a respiratory therapy unit, the method comprising: receiving at least one liquid level measurement from a level sensor, the at least one liquid level measurement indicating at least one liquid level in a liquid container of the respiratory therapy unit; receiving at least one flow measurement from a flow sensor, the at least one flow measurement indicating a flow rate of respirable gas in the respiratory therapy unit; and calculating a humidity of the respirable gas based on at least the at least one liquid level measurement and the at least one flow measurement.

190. The method according to claim 189, further comprising actuating a humidity-based valve, wherein the valve controls the flow rate of the breathable gas.

191. The method according to any of claims 189 to 190, further comprising: comparing the calculated humidity with a reference humidity; and generating an alarm if the calculated humidity is below the reference humidity.

192. The method according to any of claims 189 to 191, further comprising: 124 comparing at least one liquid level measurement with a reference liquid level; generating an alarm; and stopping the operation of the respiratory therapy unit.

193. The method according to any of claims 189 to 192, wherein the level sensor is a capacitive sensor.

194. The method according to any of claims 189 to 193 using the system according to any of claims 40 to 150.

195. A method for providing respiratory therapy to a patient using the system according to any of claims 40 to 150, the method comprising: expelling a flow of breathable gas from a ventilator through a conduit and into a nasal cannula; and delivering the breathable gas to a nostril of the patient from at least one nasal tip of the nasal cannula, the nasal cannula being in fluid communication with the conduit and configured to receive the breathable gas from the supply tube; wherein the at least one nasal tip is configured to deliver breathable gas from a distal end of the at least one nasal tip at an outlet velocity of at least approximately 40 m / s and less than approximately 75 m / s.

196. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.4 mm and less than approximately 1.8 mm, and the fan has a maximum flow set point greater than or equal to approximately 9 L / min and less than approximately 28 L / min.

197. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.8 mm and less than approximately 1.9 mm, and the fan has a maximum flow set point greater than or equal to approximately 13 L / min and less than approximately 31 L / min.

198. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.9 mm and less than approximately 3 mm, and the fan has a maximum flow set point greater than or equal to approximately 21 L / min and less than approximately 60 L / min.

199. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 3 mm and less than approximately 4 mm, and the ventilator has a maximum flow set point greater than or equal to approximately 34 L / min and less than approximately 80 L / min.

200. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.1 mm and less than approximately 1.6 mm, and the nasal cannula has a pressure drop of less than approximately 80 hPa when the ventilator operates at a maximum flow set point of approximately 8 L / min.

201. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.5 mm and less than approximately 2 mm, and the nasal cannula has a pressure drop of less than approximately 100 hPa when the ventilator operates at a maximum flow set point of approximately 20 L / min.

202. The method according to claim 195, wherein the at least one nasal tip has an inside diameter greater than or equal to approximately 1.9 mm and less than approximately 3.5 mm, and the nasal cannula has a pressure drop of less than approximately 80 hPa when the ventilator operates at a maximum flow set point of approximately 40 L / min.

203. The method according to any of claims 195 to 202, further comprising: receiving first data indicative of one or more dimensions of the nasal cannula; receiving second data indicative of a respirable gas flow rate; and calculating the exit velocity based on the first and second data.

204. The method according to claim 203, further comprising: generating for visualization at least one selected from the group of: the flow rate, the outlet velocity, a maximum flow set point, and a pressure drop.

205. The method according to any of claims 203 to 204, comprising generating to display the flow rate and outlet velocity.

206. The method according to any of claims 203 to 205, further comprising: receiving a user input to increase or decrease the flow rate of the breathing gas; changing the flow rate to a modified flow rate of the breathing gas; calculating a modified velocity based on the modified flow rate and the initial data; and generating for display at least one selected from the group of: the modified flow rate and the modified velocity.

207. The method according to any of claims 195 to 206, wherein the exit velocity is at least approximately 40 m / s and less than approximately 70 m / s.

208. The method according to any of claims 195 to 207, wherein the exit velocity is at least approximately 40 m / s and less than approximately 65 m / s.

209. The method according to any of claims 195 to 208, wherein the exit velocity is at least approximately 40 m / s and less than approximately 60 m / s.

210. The method according to any of claims 195 to 209, wherein the exit velocity is at least approximately 40 m / s and less than approximately 55 m / s.

211. The method according to any of claims 195 to 210, wherein the exit velocity is at least approximately 40 m / s and less than approximately 50 m / s.

212. The method according to any of claims 195 to 211, wherein the exit velocity is at least approximately 40 m / s and less than approximately 45 m / s.

213. The method according to any of claims 195 to 212, wherein the exit velocity is approximately 40 m / s. / zQQQn / zznz / q / uili 126 214. A respiratory therapy unit comprising: a ventilator configured to expel breathable gas; a controller; a removable battery; and a backup battery.

215. The respiratory therapy unit according to claim 214, wherein the controller is configured to initiate a low-power mode for the system when the removable battery is removed.

216. The respiratory therapy unit according to any of claims 214 to 215, wherein the system is configured to operate without the removable battery.

217. The respiratory therapy unit according to any of claims 214 to 216, wherein the backup battery is configured to provide power to the ventilator and the controller.

218. The respiratory therapy unit according to claim 217, wherein the backup battery is configured to provide power for at least approximately one hour.

219. The respiratory therapy unit according to claim 215, wherein the low energy mode allows the operation of one or more alarms and the ventilator.

220. A measuring device for a respiratory therapy unit, the measuring device comprising: a first flow sensor, a second flow sensor, and a conduit in fluid communication with the respiratory therapy unit, wherein the first flow sensor and second flow sensor are positioned in series along the conduit.

221. The measuring device according to claim 220, wherein the conduit is configured to: receive breathable gas from an inlet of the respiratory therapy unit; direct the breathable gas through the first flow sensor, wherein the first flow sensor is configured to emit a first measurement of the breathable gas; direct the breathable gas through the second flow sensor, wherein the second flow sensor is configured to emit a second measurement of the breathable gas; and expel the breathable gas to the respiratory therapy unit.

222. The measuring device according to claim 221, further comprising a controller operatively coupled to the respiratory therapy unit, and wherein the controller is configured to adjust a ventilator respirable gas flow rate based on at least one of the first or second measurements.

223. The measuring device according to any of claims 221 to 222, and wherein the first flow sensor and the second flow sensor are mass flow sensors.

224. The measuring device according to any of claims 221 to 223, wherein the controller is configured to calibrate each of the first flow sensor and the second flow sensor relative to each other.

225. The measuring device according to any of claims 220 to 224, wherein the device conduit comprises a first segment configured to direct breathable gas through the first flow sensor and a second segment configured to direct breathable gas through the second flow sensor, wherein the first segment and the second segment are approximately straight.

226. The measuring device according to any of claims 220 to 225, further comprising a supplementary gas inlet configured to receive supplementary gas from an external gas source and add the supplementary gas to the breathable gas, wherein the supplementary gas inlet is arranged between the first flow sensor and the second flow sensor.

227. The measuring device according to claim 226, further comprising an inlet valve configured to control a supplementary gas flow rate through the supplementary gas inlet.

228. The measuring device according to claim 227, wherein the supplementary valve is a solenoid valve.

229. The measuring device according to any of claims 227 to 228, wherein the first flow sensor is configured to emit a first measurement of the breathing gas, and wherein the second flow sensor is configured to emit a second measurement of a mixture of the breathing gas and the supplemental gas.

230. The measuring device according to claim 229, wherein the controller is configured to calculate a flow difference between the first measurement and the second measurement, wherein the flow difference indicates an amount of one or more components of the supplemental gas added to the breathing gas, and wherein the controller is configured to calculate one or more concentrations of one or more components in the mixture based on the flow difference and the second measurement.

231. The measuring device according to claim 230, wherein the controller is configured to operate the inlet valve to control the added quantity based on the calculated flow difference.

232. The measuring device according to claim 231, wherein the controller is configured to: receive a blank concentration as an input, compare one or more calculated concentrations with the blank concentration, and control the amount added based on the comparison.

233. The measuring device according to any of claims 230 to 232, wherein the flow difference is less than approximately 5% of the first measurement.

234. The measuring device according to claim 233, wherein the flow difference is less than approximately 1% of the first measurement.

235. The measuring device according to any of claims 226 to 234, wherein the external gas source is one selected from the group of: a wall gas outlet, a gas concentrator, and a gas tank.

236. The measuring device according to any of claims 226 to 235, wherein the supplemental gas is oxygen, oxygen-concentrated breathing gas, helium, nitric oxide, heliox, an anesthetic gas, or a gas containing aerosolized medication.

237. The measuring device according to any of claims 230 to 236, wherein the controller is configured to operate the supplementary valve to pause the flow of the supplementary gas and to calibrate the first flow sensor and the second flow sensor to each other while the flow of the supplementary gas is paused, wherein the calibration reduces an error of the calculated flow difference to an error of the second flow sensor.

238. The measuring device according to any of claims 226 to 237, further comprising: one or more additional supplementary gas inlets for adding one or more additional supplementary gases; and one or more additional flow sensors, wherein the device comprises an additional flow sensor for each of the additional supplementary gas inlets.

239. The measuring device according to any of claims 226 to 238, wherein the supplemental gas comprises oxygen, and wherein the controller is configured to adjust the supplemental gas flow rate through the supplemental gas inlet based on pulse oximeter data.

240. The measuring device according to claim 239, wherein the supplemental gas flow rate is adjusted to set an oxygen concentration of the breathable gas supplied to the patient to a minimum oxygen concentration determined to have a therapeutic effect on the patient based on pulse oximeter data.

241. The measuring device according to any of claims 239 to 240, wherein the pulse oximeter data includes SpO2 data and alarm condition signals, and wherein the controller is configured to: receive the pulse oximeter data; from the SpO2 data, determine the PaO2 data for calculating an appropriate oxygen concentration of the breathing gas; effect adaptive feedback control of the breathing gas based on the SpO2 level signals by means of a device interface, wherein the adaptive feedback control is provided by a proportional-integer derivative (PID) controller; receive data via the gas interface which includes a signal indicating that the breathing gas supplied by the measuring device has been manually changed;and upon receiving the signal via the gas interface, enter a manual override mode and stop sending adaptive feedback control signals to the device interface.

242. The measuring device according to claim 241, wherein the controller is configured to compare measurement data with alarm limits and to initiate an alarm condition if the measured data is outside the alarm limits.

243. The measuring device according to any of claims 241 to 242, wherein the device interface is operatively coupled to the supplementary valve, and wherein the adaptive feedback control of the breathing gas comprises adjusting the supplementary gas flow rate through the supplementary gas inlet by actuating the supplementary valve.

244. The measuring device according to any of claims 241 to 243, wherein the controller comprises a memory configured to store a lookup table, wherein the controller determines the PaO2 data by referencing the lookup table, and wherein the controller is configured to convert a received SpO2 value to a PaO2 value by interpolation upon determining that the received SpO2 value is not present in the lookup table.

245. The measuring device according to claim 244, wherein the lookup table is derived from a sigmoidal-shaped oxyhemoglobin dissociation curve.

246. The measuring device according to any of claims 239 to 245, wherein the pulse oximeter data includes one or more signals indicative of the patient's current blood oxygen level, and wherein the controller is configured to: receive via a pulse oximeter interface the one or more signals indicative of the current blood oxygen level; receive via a device interface data indicative of the breathing gas and supplemental gas mixture; compare the one or more signals indicative of the current blood oxygen level with a target blood oxygen level; calculate an appropriate change to the mixture to achieve a change in the percentage of oxygen in the mixture; alter the percentage of oxygen in the mixture by actuating the supplemental valve; and receive further signals from the pulse oximeter interface indicative of the patient's current blood oxygen level.

247. The measuring device according to any of claims 226 to 246, wherein the controller is configured to: receive, via one or more interfaces, oxygen data from a pulse oximeter and carbon dioxide data from a transcutaneous carbon dioxide sensor; compare the oxygen data and carbon dioxide data with a reference table, which includes at least one reference oxygen value and at least one reference carbon dioxide value; and determine to provide the patient with high oxygen therapy or high washout therapy.

248. The measuring device according to claim 247, wherein the controller is further configured to, when determining to provide the patient with high oxygen therapy, increase the flow rate of the supplemental gas through the supplemental gas inlet by actuating the supplemental valve 130.

249. The measuring device according to 247, wherein the controller is further configured to, when determining to provide the patient with high washout therapy, increase the ventilator's breathing gas flow rate.

250. A respiratory therapy system comprising: an auxiliary unit having a heating section and a heating plate disposed in the heating section; and a base unit having a heat actuator configured to be operatively coupled to the heating plate and not in contact with the heating plate.

251. The respiratory therapy system according to claim 250, wherein the heat actuator is a coil configured to induce a current in the heating plate.

252. The respiratory therapy system according to claim 251, wherein the induced current generates heat in the heating plate due to a resistance of the heating plate.

253. The respiratory therapy system according to any of claims 250 to 252, wherein the heating plate is configured to be immersed in a liquid within the auxiliary unit and to heat the liquid.

254. The respiratory therapy system according to any of claims 250 to 253, wherein the heating plate does not contact an external surface of the auxiliary unit.

255. The respiratory therapy system according to any of claims 250 to 254, wherein the heating plate comprises a protruding tab, and wherein the base unit comprises a temperature sensor configured to emit a temperature measurement of the protruding tab.

256. The respiratory therapy system according to claim 255, further comprising a controller configured to receive the temperature measurement and compare the temperature measurement with a reference temperature.

257. The respiratory therapy system according to claim 266, wherein, based on comparing the temperature measurement with the reference temperature, the controller is configured to at least stop the operation of the respiratory therapy system or generate an alarm.

258. The respiratory therapy system according to any of claims 250 to 257, wherein the heat actuator is configured to operate while the respiratory therapy unit operates without an external power supply.

259. The respiratory therapy system according to any of claims 250 to 258, wherein the heating plate is specific in orientation with respect to the heat actuator.

260. A respiratory therapy system comprising: a base unit configured to expel breathable gas; and an auxiliary unit configured to receive the expelled breathable gas, the auxiliary unit comprising: a liquid container; and 131 a vapor transfer cartridge (VTC) configured to humidify the breathable gas; wherein the liquid container comprises an outlet conduit in fluid communication with a cartridge inlet of the VTC.

261. The respiratory therapy system according to claim 260, wherein the base unit comprises a level sensor configured to emit at least one liquid level measurement indicating a liquid level in the liquid container.

262. The respiratory therapy system according to claim 261, further comprising a controller, wherein the controller is configured to: receive at least one liquid level measurement from the level sensor; calculate an outlet humidity from the VTC based at least in part on the at least one liquid level measurement.

263. The respiratory therapy system according to claim 262, further comprising a gas valve configured to actuate a gas flow rate of the respirable gas expelled from the base unit to the auxiliary unit, wherein the controller is configured to control the gas valve based on the outlet humidity.

264. The respiratory therapy system according to any of claims 261 to 263, wherein the controller is configured to compare at least one liquid level measurement with a reference liquid level and at least one to generate an alarm or stop the operation of the system.

265. The respiratory therapy system according to any of claims 261 to 264, wherein the level sensor is a capacitive sensor.

266. The method according to any of claims 20 to 39, wherein respiratory therapy is used for the treatment of coronavirus disease 2019 (COVID-19).

267. The method according to claim 266, wherein the breathable gas comprises supplemental oxygen.

268. The method according to any of claims 266 to 267, wherein the nasal cannula is surrounded by a mask configured to minimize the spread of aerosols from exhaled air.

269. The system, device or method according to any of claims 1 to 268, wherein a nebulizer is configured to introduce aerosolized medication into breathable gas via an adapter or port.

270. The system, device or method according to claim 269, wherein the nebulizer is configured to connect to one of: the delivery tube, the nasal cannula or the auxiliary unit.

271. The system, device or method according to any of claims 1 to 270, wherein respiratory therapy is provided via a mobile platform.

272. The system, device or method according to claim 271, wherein the mobile platform is a rolling cart or vehicle.

273. The system, device or method according to any of claims 271 to 132, wherein the mobile platform allows continuous operation of the system during transport.

274. The system, device or method according to any of claims 271 to 273, wherein respiratory therapy is provided in the patient's home or in an ambulance.

275. The system, device or method according to any of claims 271 to 274, wherein the fan draws in ambient air and operates using energy from an internal battery.

276. The system, device or method according to any of claims 1 to 275, wherein the base unit is a first base unit, and wherein the auxiliary unit is configured to be removed from the first base unit and transferred to a second base unit.

277. The system, device or method according to claim 276, wherein a label on the auxiliary unit is configured to store data indicative of a therapy provided to the patient using the first base unit.

278. The system, device or method according to claim 277, wherein the label is configured to store the data before or during the removal of the auxiliary unit from the first base unit.

279. The system, device or method according to any of claims 277 to 278, wherein the tag is configured to transmit data to a controller of the second base unit.

280. The system, device or method according to any of claims 277 to 279, wherein the second base unit is configured to resume therapy provided to the base unit when the auxiliary unit is transferred.

281. The system, device, or method according to any one of claims 277 to 280, wherein the data are indicative of at least one of: that the auxiliary unit was providing therapy, a time at which therapy was stopped, a breathing gas flow rate, a breathing gas temperature, a breathing gas oxygen concentration, a breathing gas humidity, an actual temperature relative to a set-point temperature, the patient's age, the patient's height, the patient's weight, the patient's illness, the disease status, and one or more concomitant therapies.

282. A system for providing high-speed respiratory therapy to a patient's nose, the system comprising: a breathable gas source configured to expel a breathable gas flow at a flow rate of 8-60 L / min and an outlet pressure; a gas passage in fluid communication with the breathable gas source and configured to carry the breathable gas flow from the breathable gas source; and a nasal cannula in fluid communication with the gas passage and having at least one nasal tip with an outlet orifice having a tip cross-sectional area, the nasal cannula defining a first flow path length and configured to receive the breathable gas flow from the gas passage and transmit the breathable gas flow through the outlet orifice;wherein the gas passage defines a second flow path length between the source of respirable gas and the nasal cannula, the gas passage has a minimum passage cross-sectional area at a point along the second flow path length, such that the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is 2.5 to 5, wherein when the respirable gas flows through the nasal cannula a pressure drop occurs in an amount corresponding to less than 35% of the outlet pressure, and wherein the at least one nasal tip outlet orifice is configured such that the respirable gas leaving the outlet orifice has an outlet velocity of at least 40 m / s.

283. The system according to claim 282, wherein the source of breathable gas is any of a fan, a compressor, a portable gas tank, or a wall outlet.

284. The system according to any of claims 282 to 283, further comprising a humidifier positioned along the gas passage and configured to humidify the breathable gas flow.

285. The system according to claim 284, wherein the humidifier is a vapor transfer unit comprising a plurality of permeable fibers, a liquid inlet, and a liquid outlet, wherein the liquid inlet is configured to carry a heated liquid into the vapor transfer unit, such that the heated liquid flows around the plurality of permeable fibers.

286. The system according to claim 284, wherein the humidifier can be a hot pot humidifier comprising a heating plate and a fluid reservoir, wherein the heating plate heats a liquid in the fluid reservoir.

287. The system according to any of claims 282 to 286, wherein the tip cross-sectional area is substantially circular.

288. The system according to any of claims 282 to 286, wherein the tip cross-sectional area has an oval shape.

289. The system according to any of claims 282 to 288, wherein the tip cross-sectional area has an inside diameter of 1.2 to 3.8 mm.

290. The system according to any of claims 282 to 289, wherein the outlet pressure is approximately 14 kPa.

291. The system according to any of claims 282 to 290, wherein the pressure drop of the respirable gas through the nasal cannula is 1 to 4.5 kPa.

292. The system according to any of claims 282 to 291, further comprising an oxygen source configured to provide an oxygen flow, such that the breathable gas flow comprises the oxygen flow.

293. The system according to any of claims 282 to 292, wherein the gas passage comprises a supply tube having an inlet port coupled to the breathing gas source, an outlet port coupled to the nasal cannula, and a lumen configured to carry the breathing gas from the inlet port to the outlet port.

294. The system according to any of claims 282 to 293, wherein the nasal cannula 134 comprises a facial tube section.

295. The system according to any of claims 282 to 294, wherein the exit speed is 40 to 80 m / s.

296. The system according to any of claims 282 to 295, wherein the source of breathable gas is a centrifugal fan.

297. The system according to any of claims 282 to 296, wherein the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 2.5, and the flow rate is 40-60 L / min.

298. The system according to any of claims 282 to 296, wherein the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 3, and the flow rate is approximately 20 L / min.

299. A method for delivering high-speed respiratory therapy to a patient's nose, the method comprising the steps of: expelling a flow of breathable gas from a breathable gas source at a flow rate of 8-60 L / min and a first outlet pressure; conveying the flow of breathable gas from the breathable gas source along a gas passage to a nasal cannula, wherein the gas passage defines a first flow path length between the breathable gas source and the nasal cannula, wherein the nasal cannula has a nasal tip with an outlet orifice having a tip cross-sectional area, the nasal cannula defining a second flow path length, and wherein the gas passage has a minimum passage cross-sectional area along the first flow path length such that the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is 2.5 to 5, and wherein when the breathable gas flows through the nasal cannula a pressure drop occurs in an amount corresponding to less than 35% of the outlet pressure; and supplying the flow of breathable gas to the nose of a patient through the outlet orifice at an outlet velocity of at least 40 m / s.

300. The method according to claim 299, wherein the source of breathable gas is any of a fan, a compressor, a portable gas tank, or a wall outlet.

301. The method according to any of claims 299 to 300, further comprising: humidifying the breathing gas flow with a humidifier positioned along the gas passage.

302. The method according to claim 301, wherein the humidifier is a vapor transfer unit comprising a plurality of permeable fibers, a liquid inlet, and a liquid outlet, wherein the liquid inlet is configured to carry a heated liquid into the vapor transfer unit, such that the heated liquid flows around the plurality of permeable fibers. 135 303. The method according to claim 301, wherein the humidifier is a hot pot humidifier comprising a heating plate and a fluid reservoir, wherein the heating plate heats a liquid in the fluid reservoir.

304. The method according to any of claims 299 to 303, wherein the tip cross-sectional area is substantially circular.

305. The method according to any of claims 299 to 304, wherein the tip cross-sectional area has an oval shape.

306. The method according to any of claims 299 to 305, wherein the tip cross-sectional area has an inside diameter of 1.2 to 3.8 mm.

307. The method according to any of claims 299 to 306, wherein the outlet pressure is approximately 14 kPa.

308. The method according to any of claims 299 to 307, wherein the pressure drop of the respirable gas through the nasal cannula is 1 to 4.5 kPa.

309. The method according to any of claims 299 to 308, further comprising: mixing the breathable gas flow with an oxygen flow provided by an oxygen source configured to provide an oxygen flow.

310. The method according to any of claims 299 to 309, wherein the first gas passage comprises a supply tube having an inlet port coupled to the breathing gas source, an outlet port coupled to the nasal cannula, and a lumen configured to carry the breathing gas from the inlet port to the outlet port.

311. The method according to any of claims 299 to 310, wherein the nasal cannula comprises a facial tube section.

312. The method according to any of claims 299 to 311, wherein the exit velocity is 40 to 80 m / s.

313. The method according to any of claims 299 to 312, wherein the source of breathable gas is a centrifugal fan.

314. The method according to any of claims 299 to 313, wherein the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 2.5, and the flow rate is 40-60 L / min.

315. The method according to any of claims 299 to 313, wherein the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is approximately 3, and the flow rate is approximately 20 L / min.

316. The method according to any of claims 299 to 315, wherein the breathing gas is supplied at a second outlet pressure equal to the first outlet pressure less a cumulative pressure drop comprising the pressure drop that occurs in the nasal cannula.

317. The method comprises the steps of: expelling a flow of breathable gas from a breathable gas source at a flow rate of 8-60 L / min and a first outlet pressure; conveying the flow of breathable gas from the breathable gas source along a gas passage to a nasal cannula, wherein when the breathable gas flows through the nasal cannula a pressure drop occurs in an amount corresponding to less than 35% of the outlet pressure; and delivering the flow of breathable gas to the nose of a patient through the outlet orifice of at least one nasal prong at an outlet velocity of at least 40 m / s.

318. The method according to claim 317, wherein: the gas passage defines a first flow path length between the breathable gas source and the nasal cannula, the outlet orifice of the at least one nasal tip of the nasal cannula has a tip cross-sectional area, the nasal cannula defines a second flow path length, and the gas passage has a minimum passage cross-sectional area along the first flow path length such that the ratio of the minimum passage cross-sectional area to the tip cross-sectional area is 2.5 to 5.

319. A method for determining the humidity of breathable gas delivered to a patient, the method comprising the steps of: delivering breathable gas to a patient at a gas flow rate and gas temperature using a respiratory therapy system comprising: a controller; a humidifier having a reservoir containing water and a heater configured to heat the water in the reservoir; and a power supply coupled to the heater and configured to supply power to the heater; humidifying the breathable gas by supplying power to the heater and heating the water in the humidifier reservoir; and determining a humidity level of the breathable gas based on (1) a ratio of the supplied power to an expected power and (2) a saturated humidity level for the gas temperature.

320. The method according to claim 319, wherein the expected energy is determined based on a linear relationship between the gas flow rate and the energy supplied over a range of flow rate values.

321. The method according to claim 320, wherein the range of flow rate values ​​is between 5 L / min and 25 L / min.

322. The method according to any of claims 319 to 321, wherein the power supply transmits data indicative of the power supplied to the controller, and wherein the controller performs the determination step.

323. The method according to any of claims 319 to 322, wherein the controller has a memory that stores a table of saturated humidity level values ​​for a range of gas temperature values, and wherein the determining step comprises retrieving the saturated humidity level from the memory for the gas temperature.

324. The method according to claim 323, wherein the gas temperature is a setpoint temperature stored in memory.

325. The method according to any of claims 319 to 324, wherein the determining step is performed automatically by the controller when the respiratory therapy system is in a steady state where the water in the tank is at a steady temperature.

326. The method according to any of 319 to 325, wherein the heater comprises a heating plate disposed in the tank and an induction element physically separated from the heating plate, wherein the induction element receives the supplied energy and generates a magnetic induction current in the heating plate.

327. The method according to any of claims 319 to 326, wherein the heater is an electrically conductive wick disposed in the reservoir and coupled to the power supply.

328. The method according to any of claims 319 to 327, further comprising: periodically refilling the tank, wherein the determination step is not performed during the refilling step.

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