Method and system for controlling oxygen supply in flow therapy devices

Abstract

The present invention provides an improved flow therapy device that enables the adjustment and control of gas flow characteristics, including flow rate, temperature, gas concentration (such as oxygen concentration), humidity, and pressure. [Solution] A control system for flow therapy equipment is provided, which can control the supply of FdO2 (fraction of delivered oxygen) to the patient. The control system can maintain FdO2 at a target level during a treatment session, and the control system can automatically control the oxygen inhalation valve to control the flow of oxygen to the patient.

Description

[Technical Field]

[0001] This disclosure relates to a method and system for controlling oxygen supply within a flow therapy device. [Background technology]

[0002] Respirators are used in a variety of environments, including hospitals, medical facilities, residential nursing, or home settings, to supply a gas flow to a user or patient. Respirators or flow therapy devices may include an oxygen inlet to allow the supply of supplemental oxygen along with the gas flow and / or a humidifier to supply heated and humidified gas. Flow therapy devices may allow for the adjustment and control of gas flow characteristics, including flow rate, temperature, gas concentration such as oxygen concentration, humidity, and pressure. [Overview of the project] [Means for solving the problem]

[0003] According to certain features, aspects, and advantages of the first embodiment disclosed herein, a respiratory device for providing a gas flow to a patient includes: an ambient air intake; an auxiliary intake for receiving auxiliary gas from an auxiliary gas source; a valve configured to control the flow rate of auxiliary gas received by the auxiliary gas intake; a flow sensor configured to measure the total flow rate of gas supplied to a patient; and a controller configured to control the supply of gas to the patient, the controller configured to determine a target auxiliary gas flow rate based at least in part on the total flow rate and to set a valve current based on the target auxiliary gas flow rate.

[0004] In some configurations of the first embodiment, the auxiliary gas includes concentrated oxygen.

[0005] In some configurations of the first embodiment, the controller is configured to determine the target auxiliary gas flow rate based at least partially on the target FdO2 (fraction of delivered oxygen).

[0006] In some configurations of the first embodiment, the controller is configured to determine a target auxiliary gas flow rate based at least in part on the oxygen fraction of the ambient air.

[0007] In some configurations of the first embodiment, the controller is configured to determine a target auxiliary gas flow rate based at least in part on the oxygen fraction of the auxiliary gas source.

[0008] In some configurations of the first embodiment, the controller is configured to set a valve current based on a target auxiliary gas flow using a valve model.

[0009] In some configurations of the first embodiment, the valve model is updated over time.

[0010] In some configurations of the first embodiment, the valve model is updated based at least in part on the measured FdO2.

[0011] In some configurations of the first embodiment, the valve model is updated based at least in part on the total flow rate.

[0012] In some configurations of the first embodiment, the valve model is updated based at least in part on the target FdO2.

[0013] In some configurations of the first embodiment, the valve model includes an estimate of the minimum current required to open the valve.

[0014] In some configurations of the first embodiment, the estimate of the minimum current required to open the valve is updated over time.

[0015] In some configurations of the first embodiment, the valve model includes an estimate of the flow rate of the auxiliary gas passing through the valve.

[0016] In some configurations of the first embodiment, the estimate of the flow rate of the auxiliary gas passing through the valve is determined using at least one of a linear model, an advection-diffusion equation, a Navier-Stokes equation, or a machine learning algorithm.

[0017] According to certain features, aspects, and advantages of the second embodiment disclosed herein, a respiratory device for providing a gas flow to a patient includes: an ambient air intake; an auxiliary intake for receiving an auxiliary gas from an auxiliary gas source; a valve configured to control the flow rate of the auxiliary gas received by the auxiliary gas intake; a gas composition sensor configured to measure the gas composition of a mixed flow of ambient air and auxiliary gas; and a controller configured to control the supply of gas to a patient, the controller being configured to adjust the operation of the valve by controlling the valve current, determine a target auxiliary gas flow rate, set the valve current based on the target auxiliary gas flow rate using a valve model, and update the valve model over time, in part, based on measurements obtained from the gas composition sensor.

[0018] In some configurations of the second embodiment, the auxiliary gas includes concentrated oxygen.

[0019] In some configurations of the second embodiment, the valve model is updated over time, partially based on predicted changes in the measured gas composition.

[0020] In some configurations of the second embodiment, the predicted change in the measured gas composition is at least partially based on the current valve position and the current flow rate.

[0021] In some configurations of the second embodiment, the measured gas composition is measured FdO2 (fraction of delivered oxygen).

[0022] In some configurations of the second embodiment, the valve model is updated over time based in part on the target gas composition.

[0023] In some configurations of the second embodiment, the target gas composition is target FdO2.

[0024] In some configurations of the second embodiment, the valve model is updated over time, partially based on predicted changes in the gas composition.

[0025] In some configurations of the second embodiment, the predicted change in gas composition is at least partially based on recent trends in the measured gas composition.

[0026] In some configurations of the second embodiment, the valve model includes estimating the minimum current required to open the valve.

[0027] In some configurations of the second embodiment, the estimate of the minimum current required to open the valve is updated over time.

[0028] In some configurations of the second embodiment, the respiratory device further includes a flow sensor configured to measure the total flow rate.

[0029] In some configurations of the second embodiment, the controller determines the target auxiliary gas flow rate based at least partially on the total flow rate.

[0030] In some configurations of the second embodiment, the controller determines the target auxiliary gas flow rate based at least partially on the target FdO2.

[0031] In some configurations of the second embodiment, the controller determines the target auxiliary gas flow rate based at least partially on the oxygen fraction of the ambient air.

[0032] In some configurations of the second embodiment, the controller determines the target auxiliary gas flow rate based at least partially on the oxygen fraction of the auxiliary gas source.

[0033] In some configurations of the second embodiment, the controller updates the valve model at various rates depending on the expected range of respiratory rates.

[0034] In some configurations of the second embodiment, the controller updates the valve model at various rates depending on the expected flow amplitude.

[0035] In some configurations of the second embodiment, the controller updates the valve model at various rates depending on the flow rate.

[0036] In some configurations of the second embodiment, the controller updates the valve model using a feedback loop.

[0037] In some configurations of the second embodiment, the coefficient of the feedback loop is adjusted in part based on the flow rate.

[0038] In some configurations of the second embodiment, the valve model includes estimating the flow rate of an auxiliary gas through the valve.

[0039] In some configurations of the second embodiment, the flow rate of the auxiliary gas through the valve is estimated using at least one of a first-order model, advection-diffusion equations, Navier-Stokes equations, or a machine learning algorithm.

[0040] According to certain features, aspects, and advantages of the third embodiment disclosed herein, a respiratory device for providing a gas flow to a patient includes: an ambient air intake; an auxiliary intake for receiving auxiliary gas from an auxiliary gas source; a valve requiring a minimum amount of current to open; a gas composition sensor configured to measure the gas composition of a mixed flow of ambient air and auxiliary gas; a main controller configured to control the supply of gas to a patient, the main controller being configured to adjust the operation of a valve opening by controlling a valve current and to activate a core controller when a target flow rate of auxiliary gas is increased from zero; and a core controller being configured to control the operation of a valve opening by controlling a valve current, the main controller or the core controller being able to control the valve current, to repeatedly increase the current supplied to the valve, and to switch control of the valve operation to the main controller after detecting a flow through the valve.

[0041] In some configurations of the third embodiment, the controller sets the valve current to an initial value before iteratively increasing the valve current.

[0042] In some configurations of the third embodiment, the initial value corresponds to the minimum possible current required to open the valve opening of the valve.

[0043] In some configurations of the third embodiment, the controller performs a stepwise change of the valve current during each iteration of the core controller.

[0044] In some configurations of the third embodiment, the magnitude of the stepwise change increases with each iteration.

[0045] In some configurations of the third embodiment, the magnitude of the stepwise change is at least partially based on the target FdO2.

[0046] In some configurations of the third embodiment, the magnitude of the stepped change is at least partially based on the total flow rate.

[0047] In some configurations of the third embodiment, the respiratory device includes a gas composition sensor.

[0048] In some configurations of the third embodiment, the flow through the valve is detected using a gas composition sensor.

[0049] In some configurations of the third embodiment, the flow through the valve is determined to occur when the concentration of the auxiliary gas exceeds the ambient level.

[0050] In some configurations of the third embodiment, the flow through the valve is determined to occur when the concentration of the auxiliary gas exceeds the ambient level by a greater amount than the potential sensor error.

[0051] In some configurations of the third embodiment, the auxiliary gas includes concentrated oxygen.

[0052] According to certain features, aspects, and advantages of the fourth embodiment disclosed herein, a respiratory device that provides a gas flow to a patient includes a display, an ambient air intake, an auxiliary intake for receiving auxiliary gas from an auxiliary gas source, a valve, a gas composition sensor configured to measure the gas composition of a mixed flow of ambient air and auxiliary gas, and a controller configured to control the supply of gas to a patient, receive input of a target gas composition, adjust the operation of the valve to control the gas composition, display the target gas composition while in target mode, display the measured gas composition while in measurement mode, monitor the difference between the target gas composition and the measured gas composition, and change from target mode to measurement mode if the difference exceeds a first threshold, and change from measurement mode to target mode if the difference falls below a second threshold.

[0053] In some configurations of the fourth embodiment, the auxiliary gas includes concentrated oxygen.

[0054] In some configurations of the fourth embodiment, the measured gas composition is measured FdO2 (fraction of delivered oxygen).

[0055] In some configurations of the fourth embodiment, the gas composition sensor includes an acoustic transducer.

[0056] In some configurations of the fourth embodiment, the first threshold is determined in part on the target gas composition.

[0057] In some configurations of the fourth embodiment, the second threshold is determined in part on the target gas composition.

[0058] In some configurations of the fourth embodiment, the first threshold is equal to the second threshold.

[0059] In some configurations of the fourth embodiment, the first threshold exceeds the second threshold.

[0060] According to certain features, aspects, and advantages of the fifth embodiment disclosed herein, an ambient air intake for receiving ambient airflow, an auxiliary air intake for receiving auxiliary gas from an auxiliary gas source, a valve, and a controller configured to control the supply of gas to a patient, wherein the controller adjusts the position of the valve to control the flow rate of auxiliary gas added to the ambient airflow, calculates a first level, the first level representing the flow rate of auxiliary gas required to achieve a target gas composition with respect to the current total flow rate of gas, calculates a second level, the second level representing the flow rate of auxiliary gas and lower than the first level. A respiratory device comprising a controller configured to: calculate a third level, where the third level represents the flow rate of auxiliary gas and is higher than the first level; analyze the patient's respiratory cycle, where the respiratory cycle comprises continuous respiratory periods, each respiratory period comprising an inspiratory period and an expiratory period; control a valve to supply a first level of auxiliary gas during each first part of the patient's respiratory period; control a valve to supply a second level of auxiliary gas during each second part of the patient's respiratory period; and control a valve to supply a third level of auxiliary gas during each third part of the patient's respiratory period.

[0061] In some configurations of the fifth embodiment, the auxiliary gas includes oxygen.

[0062] In some configurations of the fifth embodiment, the target gas composition is target FdO2 (fraction of delivered oxygen).

[0063] In some configurations of the fifth embodiment, the auxiliary gas includes an aerosolizing agent.

[0064] In some configurations of the fifth embodiment, the target gas composition is the target aerosolizing agent concentration.

[0065] In some configurations of the fifth embodiment, the respiratory device includes a flow generator.

[0066] In some configurations of the fifth embodiment, the flow generator includes a blower.

[0067] In some configurations of the fifth embodiment, the controller is further configured to control the flow generator to supply a target flow rate.

[0068] In some configurations of the fifth embodiment, the controller is further configured to control the flow generator to supply a flow rate that meets or exceeds the patient's inspiratory demand.

[0069] In some configurations of the fifth embodiment, the device provides high-flow nasal oxygen therapy.

[0070] In some configurations of the fifth embodiment, the first portion of the respiratory period includes at least a portion of the inspiratory period of the respiratory period.

[0071] In some configurations of the fifth embodiment, the second portion of the respiratory period includes at least a portion of the beginning of the expiratory period of the respiratory period.

[0072] In some configurations of the fifth embodiment, the third portion of the respiratory period includes at least a portion of the end of the expiratory period of the respiratory period.

[0073] In some configurations of the fifth embodiment, the controller is further configured to take into account the time it takes for gas to move through the breathing circuit between the valve and the patient interface when switching between the first, second, and / or third levels.

[0074] In some configurations of the fifth embodiment, the controller is further configured to estimate the travel time between the valve and the patient interface.

[0075] In some configurations of the fifth embodiment, the controller is further configured to estimate the travel time between the valve and the patient interface based on the current total flow rate of gas.

[0076] In some configurations of the fifth embodiment, the second level is a fraction of the first level.

[0077] In some configurations of the fifth embodiment, the second level corresponds to the absence of an auxiliary gas flow in the ambient airflow.

[0078] In some configurations of the fifth embodiment, the third level is a set multiple of the first level.

[0079] In some configurations of the fifth embodiment, the third level corresponds to the maximum flow rate of the auxiliary gas.

[0080] In some configurations of the fifth embodiment, the controller is further configured to calculate a first value which is a defined multiple of the first level and a second value which is the maximum flow rate of the auxiliary gas, and to set the third level to the lower of the first or second value.

[0081] In some configurations of the fifth embodiment, the maximum flow rate of the auxiliary gas is determined based on the total flow rate.

[0082] In some configurations of the fifth embodiment, the controller is further configured to calculate a moving average of the total auxiliary gas supplied throughout the respiratory period, and generates a conserved metric by comparing the moving average of the total auxiliary gas with an estimate of the auxiliary gas that would be used if the valve were controlled to continuously supply a first level of auxiliary gas.

[0083] In some configurations of the fifth embodiment, the ventilator is configured to display saved metrics on the graphical user interface of the ventilator's display.

[0084] In some configurations of the fifth embodiment, if the stored metric does not meet the stored threshold, the controller is configured to switch to continuously controlling the valve to supply a first level of auxiliary gas.

[0085] In some configurations of the fifth embodiment, the controller is further configured to adjust the length of time for which at least one of the first level, the second level, or the third level is set.

[0086] In some configurations of the fifth embodiment, the controller is further configured to adjust the length of time based at least partially on the flow rate.

[0087] In some configurations of the fifth embodiment, the controller is further configured to adjust the length of time based at least in part on the patient's respiratory rate.

[0088] In some configurations of the fifth embodiment, the controller is further configured to adjust the length of time for which the auxiliary gas at the third level is supplied, at least in part, based on the difference between the first level and the second level.

[0089] According to certain features, aspects, and advantages of the sixth embodiment disclosed herein, a respiratory device comprising an ambient air intake for receiving ambient airflow, an auxiliary air intake for receiving auxiliary gas from an auxiliary gas source, a valve, and a controller configured to control the supply of gas to a patient, wherein the controller adjusts the position of the valve to control the flow rate of auxiliary gas added to the ambient airflow, calculates a first level, the first level representing the flow rate of auxiliary gas required to achieve a target gas composition with respect to the current total flow rate of gas, calculates a second level, the second level representing the flow rate of auxiliary gas and lower than the first level, and the patient The system is configured to analyze the respiratory cycle of a person, where the respiratory cycle includes continuous respiratory periods, each respiratory period including an inspiratory and expiratory period; to determine the appropriateness of a first or second operating mode based on one or more operating parameters and / or patient parameters; and to automatically select the first or second operating mode based on the determination, wherein in the first operating mode, the valve is continuously controlled to supply a first level of auxiliary gas flow throughout the patient's respiratory period; and in the second operating mode, the valve is controlled to supply a first level of auxiliary gas flow during a first part of the patient's respiratory period and a second level of auxiliary gas flow during a second part of the patient's respiratory period.

[0090] In some configurations of the sixth embodiment, the controller is further configured to determine the patient's respiratory interval.

[0091] In some configurations of the sixth embodiment, determining the patient's respiratory duration includes determining the patient's respiratory rate and respiratory phase.

[0092] In some configurations of the sixth embodiment, determining the patient's respiratory duration includes a respiratory confidence metric, which represents the confidence that the determination of the patient's respiratory rate and / or respiratory phase is correct.

[0093] In some configurations of the sixth embodiment, the controller is further configured to select an operating mode based at least in part on a respiratory confidence metric.

[0094] In some configurations of the sixth embodiment, the controller is further configured to compare the respiratory confidence metric with a threshold and automatically select a first operating mode if the respiratory confidence metric falls below the threshold.

[0095] In some configurations of the sixth embodiment, determining the appropriateness of the first or second operating mode includes comparing the patient's respiratory rate to a threshold.

[0096] In some configurations of the sixth embodiment, determining the appropriateness of the first or second operating mode includes comparing the patient's respiratory rate with a threshold, and automatically selecting the first mode if the patient's respiratory rate exceeds the threshold.

[0097] In some configurations of the sixth embodiment, determining the suitability of the first or second operating mode includes comparing the flow rate to a threshold.

[0098] In some configurations of the sixth embodiment, determining the appropriateness of the first or second operating mode includes comparing the flow rate to a threshold and automatically selecting the first mode if the flow rate falls below the threshold.

[0099] In some configurations of the sixth embodiment, determining the appropriateness of the first or second operating mode includes calculating the ratio of the patient's respiratory rate to the flow rate and comparing that ratio to a threshold.

[0100] In some configurations of the sixth embodiment, determining the appropriateness of the first or second operating mode includes calculating the ratio of the patient's respiratory rate to the flow rate, comparing that ratio to a threshold, and automatically selecting the first operating mode if the ratio meets the threshold.

[0101] In some configurations of the sixth embodiment, the controller is further configured to estimate the average amount of auxiliary gas used in the first and second modes, generate a conserved metric by comparing the two values, and select an operating mode based at least partially on the value of the conserved metric.

[0102] In some configurations of the sixth embodiment, the first portion of the respiratory period includes at least a portion of the inspiratory period of the respiratory period.

[0103] In some configurations of the fifth embodiment, the second portion of the respiratory period includes at least a portion of the beginning of the expiratory period of the respiratory period.

[0104] In some configurations of the sixth embodiment, the controller is further configured to calculate a third level, which represents the flow rate of the auxiliary gas and is higher than the first level.

[0105] In some configurations of the sixth embodiment, in the second operating mode, the controller is further configured to control a valve to supply a third level of auxiliary gas during a third portion of the patient's respiratory period.

[0106] In some configurations of the sixth embodiment, the third portion of the respiratory period includes at least a portion of the end of the expiratory period of the respiratory period.

[0107] In some configurations of the sixth embodiment, the controller is further configured to take into account the time it takes for gas to move through the breathing circuit between the valve and the patient interface when switching between a first level, a second level, and / or a third level.

[0108] In some configurations of the sixth embodiment, the third level is a set multiple of the first level.

[0109] In some configurations of the sixth embodiment, the third level corresponds to the maximum flow rate of the auxiliary gas.

[0110] In some configurations of the sixth embodiment, the controller is further configured to calculate a first value which is a defined multiple of the first level and a second value which is the maximum flow rate of the auxiliary gas, and to set the third level to the lower of the first or second value.

[0111] In some configurations of the sixth embodiment, the controller is further configured to adjust the length of time for which at least one of the first level, the second level, or the third level is set.

[0112] In some configurations of the sixth embodiment, the controller is further configured to adjust the length of time based at least partially on the flow rate.

[0113] In some configurations of the sixth embodiment, the controller is further configured to adjust the duration of time based at least in part on the patient's respiratory rate.

[0114] In some configurations of the sixth embodiment, the controller is further configured to adjust the length of time for which the auxiliary gas at the third level is supplied, at least in part, based on the difference between the first level and the second level.

[0115] In some configurations of the sixth embodiment, the auxiliary gas includes oxygen.

[0116] In some configurations of the sixth embodiment, the target gas composition is target FdO2 (fraction of delivered oxygen).

[0117] In some configurations of the sixth embodiment, the controller is further configured to determine the appropriateness of the first or second operating mode within a predetermined time interval.

[0118] In some configurations of the sixth embodiment, the time interval determined is based on one or more operating parameters and / or patient parameters.

[0119] One or more embodiments or configuration features can be combined with one or more other embodiments or configuration features. In addition, multiple embodiments can be used together during the process of respiratory support for a patient.

[0120] As used herein, the term "comprising" means "to be at least partially composed of." When interpreting each statement herein that contains the term "comprising," other characteristics may exist besides those preceded by the term. Related terms such as "comprise" and "comprises" should be interpreted similarly.

[0121] References to the range of numbers disclosed herein (e.g., 1 to 10) include references to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and so it is intended that all subranges of all ranges expressly disclosed herein are expressly disclosed herein. These are merely examples of what is specifically intended, and all possible combinations of numbers between the lowest and highest values ​​listed should be considered to be similarly expressly described herein.

[0122] It should be understood that alternative embodiments or configurations may include any or all combinations of two or more parts, elements, or features illustrated, described, or referenced herein.

[0123] The present invention can also be broadly said to consist of the parts, elements, and features mentioned or shown individually or collectively in the specification of this application, as well as any or all combinations of any two or more of the aforementioned parts, elements, or features.

[0124] To those skilled in the art, many modifications to the structure of the present invention, as well as vastly different embodiments and applications, will be obvious without departing from the scope of the invention as defined in the appended claims. The disclosures and descriptions herein are purely illustrative and are not intended to be limiting in any sense. Where any particular whole having known equivalents in the art to which the present invention relates is referred herein, such known equivalents shall be deemed to be incorporated herein as if they were separately described. [Brief explanation of the drawing]

[0125] Brief explanation of the drawing [Figure 1A] This diagram illustrates flow therapy equipment. [Figure 1B] This shows a detection circuit board including a flow sensor that may be used in a flow therapy device. [Figure 1C] A schematic diagram of the configuration of an ultrasonic transducer for a sensor system using flow-crossed beams is shown. [Figure 1D] A schematic diagram of the configuration of an ultrasonic transducer for a sensor system using flow-crossed beams is shown. [Figure 1E] A schematic diagram of the configuration of an ultrasonic transducer for a sensor system using a flow-along beam is shown. [Figure 1F] A schematic diagram of the configuration of an ultrasonic transducer for a sensor system using a flow-along beam is shown. [Figure 2] This is a schematic diagram of a closed-loop control system. [Figure 3] This is a first lower perspective view of the main housing of a flow therapy device, showing recesses within the housing for a motor and / or sensor module subassembly. [Figure 4] This is a second lower perspective view of the main housing of the flow therapy device, showing a recess for the motor and / or sensor module subassembly. [Figure 5] This is a perspective view of the motor and / or sensor subassembly below the main housing, as well as the fixed elbow tube of the flow therapy device. [Figure 6]This is an exploded perspective view of the components of a motor and / or sensor subassembly, schematically showing the gas flow paths through the subassembly indicated by arrows. [Figure 7] This is a bottom view of the motor and / or sensor subassembly cover and sensing PCB, showing the location of the sensor. [Figure 8] This is a rear perspective view of a flow therapy device, with a cross-sectional view taken near the rear end of the device, showing a portion of the main housing configuration that includes recesses for receiving motor and / or sensor subassemblies. [Figure 9] This is a left-front perspective view of the flow therapy device. [Figure 10] This is a left-front perspective view of the flow therapy device. [Figure 11] This is a cutaway view showing the valve module and filter module, specifically the front left section. [Figure 12] This is a schematic gas flow diagram for the filter module and valve module, where solid arrows represent the flow of oxygen (or another gas) and dashed arrows represent the flow of ambient air. [Figure 13] This is a cross-sectional view showing the gas flow path through the filter module and valve module. [Figure 14] This is an overhead perspective view of the rear of the valve module in the first configuration. [Figure 15] This is a rear overhead perspective view showing the gas flow path through the valve module of the first configuration, with solid arrows representing the flow of oxygen (or another gas) and dashed arrows representing the flow of ambient air. [Figure 16] This is a cross-sectional view through the valve module of the first configuration. [Figure 17] This is a cross-sectional view showing the coupling of the valve and valve manifold of the valve module of the first configuration and the gas flow path through them. [Figure 18] This is an example of a graph showing the relationship between valve parameters. [Figure 19] An example of a flowchart illustrating the process of adjusting a valve is shown. [Figure 20] An example of a flowchart for the process of updating the valve model is shown. [Figure 21]An example of a measurement flow chart during respiration is shown. [Figure 22] An example chart showing the results of an analysis of oxygen content within a breathing circuit is provided. [Figure 23] An example of a control scheme for oxygen conservation mode is shown. [Figure 24] An example flowchart for implementing oxygen conservation mode during a treatment session is shown. [Figure 25] This is an example flowchart of the process for deciding whether to use oxygen conservation mode during a treatment session. [Modes for carrying out the invention]

[0126] Patients suffering from a variety of health conditions and diseases can benefit from oxygen therapy. For example, patients with chronic obstructive pulmonary disease (COPD), pneumonia, asthma, bronchopulmonary dysplasia, heart disease, cystic fibrosis, sleep apnea, lung disease, respiratory trauma, acute respiratory distress, and other conditions or diseases who receive pre- and post-operative oxygen support can benefit from oxygen therapy. A common way to treat these problems is to supply supplemental oxygen to the patient to prevent their blood oxygen saturation (SpO2) from becoming too low (e.g., below about 90%). However, supplying too much oxygen to a patient can lead to hyperoxygenation of the patient's blood and is considered dangerous. Generally, a patient's SpO2 is kept within the range of about 80% to about 99%, preferably within the range of about 92% to about 96%, although these ranges can vary depending on the patient's condition. Due to various factors such as respiratory rate, tidal volume, heart rate, activity level, height, weight, age, and sex, as well as other factors, there is no single prescribed level of supplemental oxygen that can consistently achieve a target SpO2 response for each patient. Each patient needs regular monitoring and adjustment of the FdO2 supplied to them to ensure they receive the correct oxygen fraction (FdO2) to achieve their target SpO2. Achieving accurate and consistent SpO2 is a critical element in treating patients with various health conditions or diseases. Furthermore, patients suffering from these health problems may find the benefits of automated oxygen saturation control systems appealing. This disclosure can be applied to a wide range of patients requiring rapid and accurate oxygen saturation control.

[0127] The oxygen fraction (FdO2) supplied to the patient can be manually controlled. A clinician can manually adjust the oxygen supply valve to change the flow rate or oxygen fraction supplied to the patient. A clinician can determine the patient's SpO2 level using a patient monitor such as a pulse oximeter. The clinician can continue to manually adjust the amount of oxygen supplied to the patient until the patient's SpO2 level reaches a predetermined level.

[0128] One problem with the current method is that it can be difficult to manually maintain the target FdO2. In addition, clinicians cannot constantly adjust the valve to cope with fluctuating flow rates, such as during a patient's respiration.

[0129] This disclosure provides an FdO2 control system that enables automatic valve control to consistently achieve a target FdO2 even when the total flow rate fluctuates during respiration, etc. This system may also allow the user to more easily set the target FdO2 and maintain the target FdO2 despite changes in flow rate without requiring further input from the user. This FdO2 control system may also be used to more effectively execute closed-loop SpO2 control algorithms.

[0130] This disclosure provides a control system for a flow therapy device. The control system can be configured to ensure that instantaneous FdO2 is maintained at a target level at virtually every point in time during a therapy session. The open-loop control system uses a measured total flow rate and a certain gas characteristic to determine a target flow rate through an auxiliary gas intake valve, such as an oxygen control valve. The target valve flow rate is based on the flow rate required to achieve the patient's target FdO2. The flow therapy device can use the target valve flow rate and a certain assumed valve characteristic to set the valve current. The valve current can control the valve operation, which in turn controls the flow rate of gas through the auxiliary valve. The flow therapy device can use an estimate of the target valve flow rate and the actual valve flow rate to adjust the assumed valve characteristic.

[0131] In some configurations, flow therapy devices can use multiple controllers. A core controller can be used to quickly determine the minimum current required to open the oxygen control valve, and once the minimum current is determined, control of the valve can be transferred to the main controller. The main controller can determine the effective FdO2 measurement based on the average FdO2 over the entire respiration.

[0132] The controller can continuously obtain measurements of effective FdO2. The flow therapy device can alternately display target FdO2 and effective FdO2 based on the difference between the two values. The controller can determine whether the effective FdO2 is close enough to the target FdO2. When the device is displaying effective FdO2, if the difference falls below a first threshold, it switches to displaying target FdO2. When the device is displaying target FdO2, if the difference exceeds a second threshold, it switches to displaying effective FdO2.

[0133] Flow therapy equipment Figure 1A shows a flow therapy device 10. The device 10 may include a main housing 100 which includes a flow generator 11 (e.g., a blower) in the form of a motor / impeller configuration, an optional humidifier 12, a controller 13, and a user interface 14 (including input devices such as a display and buttons, a touchscreen, etc.). The controller 13 can be configured or programmed to control the operation of the device. For example, the controller can control components of the device, including, but not limited to, operating the flow generator 11 to create a flow of gas (gas flow) to be supplied to the patient, operating the humidifier 12 (if any) to humidify and / or heat the generated gas flow, controlling the flow of oxygen into the blower of the flow generator, receiving user input from the user interface 14 for reconfiguration and / or user-defined operation of the device 10, and outputting information to the user (e.g., on a display). The user can be a patient, a healthcare professional, or anyone else interested in using the device. As used herein, "gas flow" may refer to any gas flow that may be used in a respiratory assist device or respiratory apparatus, including ambient airflow, a flow containing nearly 100% oxygen, or a flow containing any combination of ambient air and oxygen.

[0134] One end of the patient breathing conduit 16 is connected to a gas outlet 21 in the housing 100 of the flow therapy device 10. The other end of the patient breathing conduit 16 is connected to a patient interface 17, such as an open nasal cannula having a manifold 19 and nasal prongs 18. In addition, the patient breathing conduit 16 may be connected to a face mask, nasal mask, nasal pillow mask, endotracheal intubation tube, tracheostomy interface, etc. The gas flow generated by the flow therapy device 10 can be humidified and supplied to the patient through the patient conduit 16 via the cannula 17. The patient conduit 16 may have a heating element 16a for heating the gas flow passing to the patient. The heating element 16a may be under the control of a controller 13. The patient conduit 16 and / or the patient interface 17 may be considered part of the flow therapy device 10 or peripheral devices to the flow therapy device 10. The flow therapy device 10, the respiratory conduit 16, and the patient interface 17 together can form a flow therapy system.

[0135] The controller 13 can control the flow generator 11 to generate a gas flow of a desired flow rate. The controller 13 can also control the auxiliary oxygen inlet to enable the supply of auxiliary oxygen, and (if any) the humidifier 12 can humidify and / or heat the gas flow to an appropriate level. The gas flow is delivered to the patient through the patient conduit 16 and cannula 17. To heat the gas to a desired temperature to obtain a desired therapeutic and / or comfort level for the patient, the controller 13 can also control the heating element in the humidifier 12 and / or the heating element 16a in the patient conduit 16. The controller 13 can be programmed with an appropriate target temperature for the gas flow, or can determine an appropriate target temperature for the gas flow. In some embodiments, a gas mixture composition including the administration of auxiliary oxygen and / or therapeutic agents may be delivered via the auxiliary oxygen inlet. The gas mixture composition may include oxygen, heliox, nitrogen, nitrogen oxide, carbon dioxide, argon, helium, methane, sulfur hexafluoride, and combinations thereof, and / or the auxiliary gas may include an aerosolizing agent.

[0136] The oxygen intake port 28 may include a valve through which pressurized gas can enter a flow generator or blower. The valve can control the flow of oxygen into the blower of the flow generator. The valve may be any type of valve, including proportional or binary valves. The oxygen source may be an oxygen tank or a hospital oxygen supply. Medical-grade oxygen is typically 95% to 100% pure. Lower purity oxygen sources may also be used. Examples of valve modules and filters are disclosed in U.S. Provisional Patent Application No. 62 / 409,543, filed on 18 October 2016 and titled “Valve Modules and Filter”, and in U.S. Provisional Patent Application No. 62 / 488,841, filed on 23 April 2017 and titled “Valve Modules and Filter”, which are incorporated herein by reference in their entirety. Valve modules and filters are discussed in more detail below with respect to Figures 17–25.

[0137] The flow therapy device 10 can measure and control the oxygen content of the gas supplied to the patient, and therefore the oxygen content of the gas inhaled by the patient. During high-flow therapy, the supplied high-flow gas meets or exceeds the patient's peak inspiratory demand. That is, the volume of gas supplied to the patient by the device during inspiration meets or exceeds the volume of gas inhaled by the patient during inspiration. Thus, high-flow therapy helps prevent ambient air from being entrained when the patient inhales and helps flush the patient's airways during exhalation. As long as the flow rate of the supplied gas meets or exceeds the patient's peak inspiratory demand, entrainment of ambient air is prevented, and the gas supplied by the device is approximately the same as the gas inhaled by the patient. Therefore, the oxygen concentration measured in the device, FdO2 (fraction of delivered oxygen), is approximately the same as the oxygen concentration the user is breathing, FiO2 (fraction of inspired oxygen), and thus these terms can be considered equivalent.

[0138] Operating sensors 3a, 3b, 3c, such as flow sensors, temperature sensors, humidity sensors, and / or pressure sensors, may be placed at various locations within the flow therapy device 10. Additional sensors (e.g., sensors 20, 25) may be placed at various locations on the patient conduit 16 and / or cannula 17 (e.g., a temperature sensor 29 may be at or near the tip of the inspiratory tube). Outputs from the sensors may be received by the controller 13 to assist the controller in operating the flow therapy device 10 in a manner that provides appropriate treatment. In some configurations, providing appropriate treatment includes meeting the patient's peak inspiratory demand. The device 10 may have a transmitter and / or receiver 15 to enable the controller 13 to receive signals 8 from the sensors and / or control various components of the flow therapy device 10, including but not limited to the flow generator 11, humidifier 12, and heating element 16a, or accessories or peripheral devices associated with the flow therapy device 10. In addition, or / or, the transmitter and / or receiver 15 may send data to a remote server or enable remote control of the device 10.

[0139] After oxygen and ambient air have finished mixing, oxygen can be measured by placing one or more gas composition sensors (such as ultrasonic transducer systems, also called ultrasonic sensor systems). Measurements can be performed within the device, within the supply conduit, within the patient interface, or at any other suitable location.

[0140] The flow therapy device 10 may include a patient sensor 26, such as a pulse oximeter or patient monitoring system, to measure one or more physiological parameters of the patient, such as blood oxygen saturation (SpO2), heart rate, respiratory rate, and perfusion index, and to provide a consistent signal quality. Sensor 26 can communicate with controller 13 via a wired connection or by communication via a wireless transmitter on sensor 26. Sensor 26 may be a disposable adhesive sensor designed to attach to the patient's finger. Sensor 26 may also be a non-disposable sensor. Sensors are available that can be used with flow therapy equipment and are designed for various age groups and to attach to various locations on the patient. Pulse oximeters are attached to the user, typically on the user's finger, but other locations such as the earlobe are also options. The pulse oximeter is connected to a processor within the device and continuously provides a signal indicating the patient's blood oxygen saturation. The patient sensor 26 can be a hot-swappable device that can be added to or replaced during the operation of the flow therapy device 10. For example, the patient sensor 26 can be connected to the flow therapy device 10 using a USB interface or a wireless communication protocol (e.g., near-field communication, WiFi, or Bluetooth®). If the patient sensor 26 is disconnected during operation, the flow therapy device 10 can continue to operate in its previous operating state for a predetermined period. After the predetermined period, the flow therapy device 10 can trigger an alarm, switch from automatic mode to manual mode, and / or completely exit control mode (e.g., automatic mode or manual mode). The patient sensor 26 may be a clinical monitoring system or other patient monitoring system that communicates with the flow therapy device 10 via a physical interface or a wireless interface.

[0141] Flow therapy device 10 may include high-flow therapy devices. High-flow therapy as discussed herein is intended to be given its general and ordinary meaning as understood by those skilled in the art, generally referring to a respiratory support system that delivers a target flow rate of humidified respiratory gas through a patient interface that is not intentionally sealed, with the flow rate generally intended to meet or exceed the patient's inspiratory flow. Typical patient interfaces include, but are not limited to, nasal or tracheal patient interfaces. Typical flow rates for adults often range from, but are not limited to, about 15 liters / minute (LPM) to about 70 liters / minute or more. Typical flow rates for pediatric patients (neonatal, infant, and child, etc.) often range from, but are not limited to, about 1 liter / minute per kilogram of patient body weight to about 3 liters / minute per kilogram of patient body weight or more. High-flow therapy may also include gas mixture compositions that optionally include the administration of supplemental oxygen and / or therapeutic agents. High-flow therapy is often referred to by several common names, including high-flow nasal oxygen therapy (NHF), humidified high-flow nasal cannula (HHFNC), high-flow nasal oxygen therapy (HFNO), high-flow therapy (HFT), or high-flow tracheal therapy (THF: tracheal high flow). The flow rate used to achieve "high flow" can be any of the following rates. For example, in some configurations, "high-flow therapy" for adult patients may refer to supplying gas to the patient at a flow rate of approximately 10 LPM or higher, such as approximately 10 LPM to approximately 100 LPM, approximately 15 LPM to approximately 95 LPM, approximately 20 LPM to approximately 90 LPM, approximately 25 LPM to approximately 75 LPM, approximately 25 LPM to approximately 85 LPM, approximately 30 LPM to approximately 80 LPM, approximately 35 LPM to approximately 75 LPM, approximately 40 LPM to approximately 70 LPM, approximately 45 LPM to approximately 65 LPM, or approximately 50 LPM to approximately 60 LPM. In some configurations, "high-flow therapy" for neonatal, infant, or child patients may refer to supplying gas to the patient at a flow rate exceeding 1 LPM, such as approximately 1 LPM to 25 LPM, approximately 2 LPM to 25 LPM, approximately 2 LPM to 5 LPM, approximately 5 LPM to 25 LPM, approximately 5 LPM to 10 LPM, approximately 10 LPM to 25 LPM, approximately 10 LPM to 20 LPM, approximately 10 LPM to 15 LPM, or approximately 20 LPM to 25 LPM.High-flow therapy devices for adult patients, neonates, infants, or children can supply gas to the patient at flow rates of approximately 1 LPM to approximately 100 LPM or within any of the sub-ranges outlined above. The flow therapy device 10 can supply any oxygen concentration (e.g., FdO2) up to 100% at any flow rate from 1 LPM to approximately 100 LPM. In some configurations, any flow rate can be combined with oxygen concentrations (FdO2) of approximately 20% to 30%, 21% to 30%, 21% to 40%, 30% to 40%, 40% to 50%, 50% to 60%, 60% to 70%, 70% to 80%, 80% to 90%, and 90% to 100%. In some combinations, the flow rate can be between approximately 25 LPM and 75 LPM when combined with oxygen concentrations (FdO2) of approximately 20%-30%, 21%-30%, 21%-40%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, 80%-90%, and 90%-100%. In some configurations, when operating in manual mode, the flow therapy device 10 may include a safety threshold to prevent the user from supplying too much oxygen to the patient.

[0142] High-flow therapy can be administered to the user through the nostrils and / or orally or via a tracheostomy interface. High-flow therapy can deliver gas to the user at a flow rate equal to or exceeding the user's peak inspiratory flow requirement. High-flow therapy can generate a flushing effect in the nasopharynx, thereby flushing the dead space of the upper airway with the incoming high-flow gas. This can create a reservoir of fresh gas that can be obtained with every breath while minimizing rebreathing of nitrogen or carbon dioxide. Meeting inspiratory demand and flushing the airway is even more important when trying to control the patient's FdO2. High-flow therapy can be delivered using an open patient interface, such as a nasal cannula. The nasal cannula may be configured to deliver respiratory gas to the user's nostrils at a flow rate exceeding the user's peak inspiratory flow requirement.

[0143] As used herein, the term “unsealed patient interface” may refer to an interface that provides a gas flow path between the patient’s airway and a gas source (such as a flow generator 11) that does not completely obstruct the patient’s airway. An unsealed gas flow path may involve obstruction of less than approximately 95% of the patient’s airway. An unsealed gas flow path may involve obstruction of less than approximately 90% of the patient’s airway. An unsealed gas flow path may involve obstruction of approximately 40% to approximately 80% of the patient’s airway. The airway may include one or more of the patient's nostrils or mouth. With a nasal cannula, the airway passes through the nostrils.

[0144] The flow generator or blower 11 may include an ambient air intake port 27 for entraining ambient air into the blower. The flow therapy device 10 may also include an oxygen intake port 28 connected to a valve through which pressurized gas can enter the flow generator or blower 11. The valve can control the flow of oxygen into the blower 11 of the flow generator. The valve may be any type of valve, including a proportional valve or a binary valve.

[0145] The blower can operate at motor speeds above approximately 1,000 RPM and below approximately 30,000 RPM, above approximately 2,000 RPM and below approximately 21,000 RPM, above approximately 4,000 RPM and below approximately 19,000 RPM, or any of the above values. The blower's operation allows for mixing of the gas entering the blower through the intake port. Since mixing requires energy, using a blower as a mixer can reduce the pressure drop that would otherwise occur in a system with a separate mixer, such as a static mixer containing a baffle. Having a static mixer can also increase the volume of the gas flow path between the valve and the gas compression sensor, which can further increase the delay between the point at which the valve current changes and the point at which the corresponding change in oxygen concentration is measured.

[0146] Based on user input and treatment provided by a specific device, the controller can determine the target output parameter of the blower. The controller receives the measured value of the target output parameter and can adjust the blower speed based on the difference between the determined flow rate and the measured flow rate.

[0147] The target output parameter can be flow rate. The target flow rate can be a constant value (e.g., nasal high flow). The target flow rate can be a variable value. In some configurations, the controller can control the blower motor speed based on the target flow rate, and in addition, can accelerate or decelerate the motor speed based on the patient's respiratory cycle. The target flow rate does not necessarily change, but the controller increases or decreases the motor speed to add oscillations to the instantaneous flow rate so that the flow rate is synchronized with the patient's respiration. Such a system is described in international application PCT / NZ2017 / 050063, filed on 17 May 2017, titled "Flow Path Sensing for Flow Therapy Apparatus".

[0148] The target output parameter could instead be pressure. The target pressure could be a constant value (e.g., CPAP). Alternatively, the target flow rate could be a value that fluctuates over time with respiration (e.g., bilevel NIV). In both of these scenarios, it is unlikely that the total flow rate will be constant.

[0149] Referring further to Figure 1B, a detection circuit board 2200 that can be implemented within the flow therapy device 10 is shown. The detection circuit board 2200 can be positioned within the sensor chamber so as to be at least partially immersed in the gas flow. The gas flow can exit the blower 11 through the conduit and enter the flow path within the sensor chamber. To measure the gas characteristics in the flow, at least a portion of the sensors on the detection circuit board 2200 may be positioned in the gas flow. After passing through the flow path in the sensor chamber, the gas can exit to the humidifier 12.

[0150] The detection circuit board 2200 can be a printed detection circuit board (PCB). Alternatively, the circuit on the board 2200 can be constructed using wires to connect electronic components rather than being printed on the circuit board. At least a portion of the detection circuit board 2200 can be mounted outside the gas flow. The gas flow can be generated by the flow generator 11 described above. The detection circuit board 2200 may include an ultrasonic transducer 2204. The detection circuit board 2200 may include one or more thermistors 2205. The thermistors 2205 may be configured to measure the temperature of the gas flow. The detection circuit board 2200 may include a thermistor flow sensor 2206. The detection circuit board 2200 may include other types of sensors, such as humidity sensors including humidity-limited sensors and humidity and temperature combined sensors used with a separate temperature sensor, sensors for measuring atmospheric pressure, sensors for measuring differential pressure, and / or sensors for measuring gauge pressure. The thermistor flow sensor 2206 may include a hot-wire anemometer such as a platinum wire and / or a thermistor such as a negative temperature coefficient (NTC) thermistor or a positive temperature coefficient (PTC) thermistor. Other non-limiting examples of the heated temperature sensor include glass or epoxy-sealed or unsealed thermistors. The thermistor flow sensor 2206 may be configured to measure the flow rate of a gas by being supplied with constant power, or to be maintained at a constant sensor temperature or a constant temperature difference between the sensor and the gas flow.

[0151] The detection circuit board 2200 may include a first portion 2201 and a second portion 2202. The first portion 2201 may be positioned within the gas flow path, while the second portion 2202 may be positioned outside the gas flow path. In Figure 1B, the direction of the gas flow is indicated by arrow 2203. The direction of the gas flow may be a straight line or a curve, as shown in Figure 1B.

[0152] The placement of one or more thermistors 2205 and / or thermistor flow sensors 2206 downstream of the combined blower and mixer can take into account the heat supplied to the gas flow from the blower. Furthermore, placing a temperature-based flow sensor in the flow path can improve measurement accuracy because the sensor placed in the flow is more likely to be exposed to the same conditions as the gas flow, such as temperature, and thus can provide a better representation of the gas characteristics.

[0153] The detection circuit board 2200 may include ultrasonic transducers, transceivers, or sensors to measure the gas characteristics of the gas flow, such as the gas composition or concentration of one or more gases in the gas flow. As can be understood, any suitable transducer, transceiver, or sensor may be mounted on the detection circuit board 2200. In this configuration, the detection circuit board includes an ultrasonic transducer system (also called an ultrasonic sensor system) that uses ultrasound or acoustic waves to determine the gas concentration. Various sensor configurations are described below with respect to Figures 1C to 1F.

[0154] An ultrasonic transducer system can determine the relative gas concentrations of two or more gases in a gas stream. An ultrasonic transducer system may be configured to measure the oxygen fraction in a large gas stream consisting of ambient air to which auxiliary oxygen, essentially a two-component gas mixture of nitrogen (N2) and oxygen (O2), has been added. It will also be understood that an ultrasonic transducer system may be configured to measure the gas concentrations of other additive gases, including nitrogen (N2) and carbon dioxide (CO2), mixed with ambient air in a gas stream. An ultrasonic transducer can determine the gas concentrations of gases in a gas stream at relatively high frequencies. For example, an ultrasonic transducer can output measured FdO2 values ​​at or below the sensor's maximum sample rate, such as approximately 1 Hz to 200 Hz, approximately 1 Hz to 100 Hz, approximately 1 Hz to 50 Hz, and approximately 1 Hz to 25 Hz.

[0155] In some configurations, the detection circuit board 2200 includes a pair of ultrasonic transducers located on either side of the detection circuit board. Various alternative configurations of the ultrasonic transducers may be used to detect the characteristics of a gas flow by transmitting or receiving ultrasonic beams or pulses.

[0156] The distance between the ultrasonic transducers 2204 on either side of the detection circuit board 2200 can affect the measurement resolution. Increasing the distance between each ultrasonic transducer 2204 can reduce proportional or fractional errors because the measured length generally has a certain amount of error, and the ratio of errors that occur during measurement is smaller as the length increases compared to shorter lengths. Therefore, the overall uncertainty of the measurement decreases. Increasing the distance also allows for a longer period of acoustic signal between the ultrasonic transducers 2204, thus improving the measurement resolution and accuracy. However, increasing the distance can lead to a weakening of the signal.

[0157] The ultrasonic transducers 2204 can be positioned such that the spacing between them overlaps the flow path at least partially. In some configurations, the ultrasonic transducers are positioned on the opposite end of the sensing circuit board. Since the entire flow path is exposed to the acoustic path, sound waves propagate through all of the gas in the flow path. Wave averaging can occur over the entire flow path rather than just one section of it. Averaging over longer distances reduces errors and reduces the dependence on the air-oxygen mixture. The ultrasonic transducers can be configured to measure gas properties from any angle to the flow path.

[0158] Placing the sensors inside the flow path or module rather than outside the flow path or module allows the transducers 2204 to operate within a smaller temperature range relative to each other or to operate at approximately the same temperature (i.e., the temperature of the gas flow). Since the transducers are temperature sensitive, keeping the transducers 2204 at a nearly uniform temperature improves accuracy. Furthermore, placing the sensors along the flow path allows for measurements and calculations that take into account the effect of gas velocity, thus eliminating the effect of gas velocity from the sensor measurements.

[0159] The ultrasonic transducer system is configured as an ultrasonic two-component gas detection system. Two-component gas analysis using ultrasound is based on detecting the velocity of acoustic pulses passing through a gaseous sample, in this case the gaseous sample is the bulk or primary flow of gas flowing through the detection channel of the sensor housing. The velocity of sound is a function of the average molecular weight and temperature of the gas. The system can receive sensor signals indicating the temperature of the gas flowing between the beam paths of the ultrasonic transducers. With knowledge of the detected velocity of sound and the detected temperature, the gas composition in the gas flow can be determined or calculated. Specifically, as is known in the field of two-component gas analysis using ultrasound, the ratio of two known gases can be inferred using measured values ​​of the velocity of sound across the detection channel by referring to empirical relationships, standard algorithms, or data stored in the form of reference tables. Alternatively, if a temperature sensor is not used, it will be understood that the estimation of the temperature of the gas flow in the beam path of the ultrasonic transducer can be used in the calculation of two-component gas analysis. In such alternative embodiments, the temperature of the gas flow can be adjusted or controlled within a narrow temperature range in order to enable the use of the estimation of the temperature of the gas flow in the beam path.

[0160] In some configurations, the flow therapy device may also include a humidity sensor, which is located within the flow path and configured to generate a humidity signal indicating the humidity of the gas flow through the sensor assembly. In such embodiments, the gas composition can be determined by the detected sound velocity, and the detected temperature and / or humidity. The humidity sensor may be a relative humidity sensor or an absolute humidity sensor. In some embodiments, the gas composition can be determined based on the detected sound velocity and detected humidity without requiring a temperature sensor.

[0161] An ultrasonic transducer system can be used to measure the individual ratios of any two known gases in a gaseous composition. The ultrasonic transducer system can determine the relative gas concentrations in a mixture of air mixed with auxiliary oxygen, which is approximately equal to a nitrogen / oxygen mixture. In such a two-component gas mixture, the average molecular weight of the gases can be determined by monitoring the speed of sound and taking temperature into account, and thus the relative concentrations of the two gases can be determined. From this ratio, the oxygen or nitrogen fraction of the gaseous flow can be extracted.

[0162] Referring to Figures 1C to 1F, various configurations of ultrasonic transducers for a gas composition detection system that detects the speed of sound passing through a gas flow by transmitting and receiving ultrasonic beams or pulses will be explained. Similar reference numbers represent similar components.

[0163] Referring to Figure 1C, the transducer configuration 2300 gives a configuration in which there is a pair of transducers 2302 and 2304 facing each other and positioned on both sides of the sensing channel 2306, with the direction of the gas channel overall indicated by 2308. In this configuration, each of the transducers 2302 and 2304 is driven as a dedicated transmitter or receiver, so that the ultrasonic pulse 2310 is transmitted in one direction across the gas channel from the transmitter transducer to the receiver transducer. As shown in the figure, the pair of transducers are aligned with respect to the air channel direction 2308 (i.e., not offset upstream or downstream from each other) and are configured to transmit flow-crossing pulses that are approximately perpendicular to the direction of the gas channel.

[0164] Referring to Figure 1D, an alternative transducer configuration 2320 is shown, in which a pair of transducers 2322, 2324 are provided opposite each other on both sides of the sensing path, but each transducer can operate as both a transmitter and a receiver (i.e., the transducer is an ultrasonic transmitter / receiver or transceiver). In this configuration, bidirectional ultrasonic pulses 2326 can be transmitted between the pair of transducers 2322, 2324. For example, the pulses can be transmitted alternately back and forth between the transducers or in any other arbitrary order or pattern. Again, in this case as well, the pair of transducers are aligned with respect to the direction of the gas flow path and configured to transmit flow-crossing pulses that are substantially perpendicular to the direction of the gas flow path.

[0165] Referring to Figure 1E, an alternative transducer configuration 2360 is shown, in which there is a pair of transducers 2362, 2364 facing each other from opposite sides of the sensing path 2306, with the direction or axis of the gas flow path generally indicated by 2308. In this configuration 2360, each of the transducers 2362, 2364 is driven as a dedicated transmitter or receiver, so that flow-along ultrasonic pulses 2366 are transmitted in one direction within a beam path between the transmitter and receiver, which are substantially aligned or parallel to the gas flow path axis 2308 in the sensing path 2306. In the illustrated embodiment, the transmitter is upstream of the receiver, but it will be understood that the opposite configuration can also be used. In this configuration, a flow sensor is provided in the sensing path to provide a flow signal indicating the flow rate of the gas flow in the sensing path. The speed of sound in the sensing path can be derived or determined in the same manner as previously described, and it will be understood that the flow signal is used in signal processing to remove or compensate for the gas flow rate in the calculated speed of sound signal.

[0166] Referring to Figure 1F, an alternative transducer configuration 2370 is shown, in which a pair of transducers 2372, 2374 are provided facing each other from opposite sides of the sensing path, as in Figure 1E, but each transducer can operate as both a transmitter and a receiver, i.e., an ultrasonic transmitter / receiver or transceiver. In this configuration, bidirectional flow-along ultrasonic pulses 2376 can be transmitted between the pair of transducers 2372, 2374. For example, the pulses can be transmitted alternately back and forth between the transducers or in any other arbitrary order or pattern. Again, the pair of transducers are aligned with the gas flow path axis 2308 and configured to transmit flow-along pulses in a beam path that is approximately aligned with or parallel to the gas flow path axis 2308 in the sensing path 2306. This configuration eliminates the need for a separate flow sensor, as the flow component of the sound velocity signal can be directly derived or determined by processing the transmitted and received acoustic pulses.

[0167] In some configurations, as described in international application PCT / NZ2017 / 050119, filed on September 13, 2017, entitled "Thermistor Flow Sensor Having Multiple Temperature Points," flow therapy devices can measure the total flow rate of a gas using a flow bead. While flow beads may have the advantage of providing more accurate flow rate measurements, they may be slow to respond to sudden changes in flow (such as high-frequency vibrations). Ultrasonic transducers can measure sudden changes in flow, but their overall measurement accuracy may be lower. In some configurations, a controller may combine inputs from both the flow bead and the ultrasonic transducer to generate a final measurement of the total flow rate, thereby enabling accurate flow rate measurements that can detect sudden changes in flow.

[0168] Some examples of flow therapy devices are disclosed in International Application No. PCT / NZ2016 / 050193, filed on 2 December 2016 and titled "Flow Path Sensing for Flow Therapy Apparatus," and in International Application No. PCT / IB2016 / 053761, filed on 24 June 2016 and titled "Breathing Assistance Apparatus," which are incorporated herein by reference in their entirety. Examples of flow therapy device configurations that can be used in conjunction with the aspects of this disclosure are discussed in more detail below.

[0169] Closed-loop control Referring again to Figure 1A, the controller 13 can be programmed with or configured to run a closed-loop control system for controlling the operation of the flow therapy device. The closed-loop control system can be configured to ensure that the patient's SpO2 reaches and consistently maintains that level or near that level.

[0170] Controller 13 can receive inputs from the user that can be used by Controller 13 to perform a closed-loop control system. The target SpO2 value can be a single value or a set of values. The value may be preset, selected by the clinician, or determined based on the patient type, where the patient type may refer to the current pain and / or patient information such as age, weight, height, sex, and other patient characteristics. Similarly, the target SpO2 can be two values, each selected in any of the above ways. The two values ​​represent a range of acceptable values ​​for the patient's SpO2. The controller can target a value within the aforementioned range. The target value can be the median of the range or any other value within the range, and may be preset or selected by the user. Alternatively, this range may be automatically set based on the target SpO2 value. When the patient's SpO2 value falls outside this range, the controller may be configured to have one or more preset responses. Responses may include issuing an alarm, switching to manual control of FdO2, changing FdO2 to a specific value, and / or other responses. A controller can have one or more ranges, and when it goes outside each range, one or more different responses occur.

[0171] Generally, SpO2 is controlled between approximately 80% and 100%, or approximately 80% and 90%, or approximately 88% and 92%, or approximately 90% and 99%, or approximately 92% and 96%. SpO2 can be controlled between any two appropriate values ​​from any two of the above ranges. The target SpO2 can be approximately 80% and 100%, or approximately 80% and 90%, or approximately 88% and 92%, or approximately 90% and 99%, or approximately 92% and 96%, or approximately 94% or 94%, or approximately 90% or 90%, or approximately 85% or 85%. The target SpO2 can be any value between any two appropriate values ​​from any two of the above ranges. The target SpO2 can correspond to the midpoint of SpO2 across a defined range.

[0172] FdO2 can be configured to be controlled within a range. As discussed earlier, as long as the flow rate meets or exceeds the patient's peak inspiratory demand, the oxygen concentration measured in the device (FdO2) will be approximately the same as the oxygen concentration the patient is breathing (FiO2), and therefore these terms can be considered equivalent. Each of the range limits may be preset, selected by the user, or determined based on the patient type, where the patient type may refer to current distress and / or patient information such as age, weight, height, sex, and / or other patient characteristics. Alternatively, a single value for FdO2 can be selected, and the range may be determined at least partially based on that value. For example, the range may be a set amount above or below the selected FdO2. The selected FdO2 can be used as the controller's starting point. If the controller attempts to move FdO2 outside the range, the system may have one or more responses. These responses may include issuing an alarm, preventing FdO2 from going outside the range, switching to manual control of FdO2, and / or switching to a specific FdO2. The device may have one or more ranges, and one or more different responses may occur when the limits of each range are reached.

[0173] Referring to Figure 2, a schematic diagram of the closed-loop control system 1000 is shown. This closed-loop control system can utilize two control loops. The first control loop may be implemented by an SpO2 controller. The SpO2 controller can determine the target FdO2 based in part on the target SpO2 and / or measured SpO2. As discussed above, the target SpO2 value may be a single value or a set of tolerances. The value may be preset, selected by the clinician, or automatically determined based on the client's characteristics. Generally, the target SpO2 value is received or determined before or at the beginning of the treatment session, but the target SpO2 value may be received at any point during the treatment session. During the treatment session, the SpO2 controller may also receive the measured FdO2 reading from the gas composition sensor, as well as the measured SpO2 reading and signal quality reading from the patient sensor, as inputs. In some configurations, the SpO2 controller can receive the target FdO2 as input, in which case the output of the SpO2 controller can be directly fed back to the SpO2 controller as input. Based at least partially on the input, the SpO2 controller can output target FdO2 to a second control loop.

[0174] During a treatment session, the SpO2 and FdO2 controllers can continue to automatically control the operation of the flow therapy device until the treatment session ends or until an event triggers a change from automatic to manual mode.

[0175] FdO2 control system Referring again to Figure 1A, the controller 13 can be programmed with or configured to run an FdO2 control system for controlling the operation of the flow therapy device.

[0176] The FdO2 control system can be configured to ensure that instantaneous FdO2 is maintained at a target level at all points during a treatment session. The controller can measure FdO2, compare it to the target FdO2, and adjust the oxygen intake valve accordingly. However, if the FdO2 sensor is located at a significant distance from the valve, there is a delay between when the valve is changed and when the corresponding change in FdO2 is measured. The controller can adjust the valve after the delay. However, if the flow rate is fluctuating, the controller may be able to achieve the target FdO2 on average rather than continuously and nearly instantaneously. To maintain FdO2 at the target level continuously and nearly instantaneously without bringing the FdO2 sensor closer to the valve, the FdO2 controller can incorporate total flow rate measurements into valve control.

[0177] Process for adjusting valve flow rate Further reference is provided in Figures 18 and 19 to illustrate the process for adjusting the flow rate of the oxygen intake valve. The main controller can first determine the valve flow rate required to achieve the target FdO2. This can be based on the target oxygen concentration, the oxygen concentration of the oxygen source, the oxygen concentration of the ambient air, and the current flow rate.

[0178] Target oxygen concentration (F target The oxygen concentration of the ambient air (F) can be set by the user or by the closed-loop SpO2 control algorithm described herein. air ) can be considered a constant. Generally speaking, the oxygen concentration (F) of the oxygen source source ) is a constant parameter. In some cases, the oxygen concentration may be adjustable by the user. The current flow rate (Q) can be measured by one or more flow sensors.

number

[0179] In one configuration, the target valve flow rate changes as the target FdO2 and flow rate change.

number

[0180] Once the target valve flow rate is determined, the controller can determine the required valve current to actuate the valve to achieve the target flow rate, and the required valve current may be determined by the valve model.

[0181] A valve model can determine the valve current using two or more parameters. The first parameter is the valve gain (I gain The valve gain defines the linear element of the relationship between the change in current and the change in flow rate. In some configurations, the value of the valve gain may be a preset constant. Alternatively, the valve gain may be determined based on the pressure of the oxygen source. The pressure of the oxygen source may refer to the pressure upstream of the flow control valve, which may be set by a pressure regulator on the oxygen supply source. The pressure of the oxygen source may be measured by a pressure sensor upstream of the oxygen valve.

[0182] The second parameter can be the current offset required to open the valve (I offset ), below this parameter there is no flow through the valve. The current offset is the minimum value (I offsetMin ) and maximum value (I offsetMax The current offset value can vary within a range having ). The current offset value is initially estimated by the core controller and can be adjusted over time using the main controller. In some embodiments, a single controller can estimate and adjust the value.

number

[0183] Next, the controller controls the valve current (I valve ) can be set to the determined value. This process, which determines the target valve flow rate and then updates the valve current, can be performed continuously. For example, this process can be performed at a rate of 20 Hz.

[0184] Core Controller When the valve is first activated (e.g., the target FdO2 is increased from 21%), the coarse controller can first determine the current offset required to open the valve. As described above, due to the distance between the valve and the gas composition sensor, there is a delay between when the position of the valve is adjusted and when the corresponding change in FdO2 is measured. Therefore, increasing the current too quickly when determining the current offset risks causing the controller to exceed the target FdO2. On the other hand, if the current increase is too slow, it may cause a further delay until the device can start supplying the target FdO2 level to the patient.

[0185] First, the estimated current offset can be set to the minimum expected value [Number] (see, for example, FIG. 18). Then, using the valve model, the current of the valve can be set based on the target valve flow rate. The estimation of the current offset can be continuously updated by the main controller. However, as described above, the main controller may be too slow to find the current offset when the valve is closed, resulting in an extended period during which supplemental oxygen is not supplied.

[0186] The coarse controller can iteratively increase the estimation of the current offset until a gas flow through the valve is detected. The magnitude of the increase at each iteration can be calculated in at least two ways. In some configurations, the larger of the two calculated magnitudes can be implemented.

[0187] The current offset can be adjusted at each time step by increasing the current offset by an exponentially increasing amount (Δl exp ). Alternatively, the current offset can be the minimum amount (Δl minThis can be adjusted at each time step by increasing the current offset by a certain amount. This minimum amount may be proportional to the determined target valve flow rate. A higher target valve flow rate may mean that larger changes to the current offset estimate can be made without the risk of exceeding the target FdO2.

[0188] During each iteration of the core controller, the core controller can increase the current offset estimate by the larger of the two values ​​mentioned above. In some configurations, the controller is Δl min Start by increasing the valve by the amount of Δl exp >Δl min When it becomes Δl exp You can switch to using [this method].

number

[0189] However, Δt is the time step of the controller, and ΔI increase is ΔI exp This is the percentage increase in [the region].

[0190] The core controller is activated when the target FdO2 is first changed or when the target FdO2 is changed from an ambient value to an increment value (e.g., FiO2 target =21% → FiO2 target >21%) can always be activated. The core controller can also be activated when the user enters closed-loop SpO2 control. To prevent the current offset from being reset to the minimum current offset after each activation, the current offset value (I) determined during the treatment session is set. offset The estimation of ) can be stored by the core controller.

[0191] When gas flow from the valve is detected, the flow therapy device can switch from using the core controller to using the primary controller. Gas flow from the valve can be identified by measuring FdO2 using a gas composition sensor. If the measured FdO2 is above the ambient level by a threshold, it can be determined that the valve is open. The threshold can be based on the sensor's error (for example, with a gas composition sensor that has an error of up to 3% in the measured FdO2 value, the valve is determined to be open when FdO2 is above 24%).

[0192] Valve model update To maintain FdO2 at the target level, the process described with respect to Figure 19 relies on the accuracy of the valve model. To improve this accuracy, the main controller continuously evaluates the accuracy of the model and the current offset (I offset The valve current (I) can be adjusted as appropriate. The process for updating the valve model is explained with reference to Figure 20. This process involves adjusting the valve current (I valve This can be done at a slower rate than the process for setting the parameters. For example, in some configurations, the current offset can be adjusted at a rate of 3 Hz. The valve model can be updated at various rates depending on various settings or parameters and / or other settings or parameters, such as the expected respiratory rate range and the expected flow rate amplitude.

[0193] Exponential filtering To adjust for current offset, the controller can compare the average target valve flow rate with an estimate of the actual average valve flow rate (the average of both these values ​​is the average over a single breath). To obtain these averages, the time constant τ is used. filt Several parameters can be filtered over time using an exponential filter with τ. filt This can be selected so that variations in the measured flow rate within a single breath of the patient are filtered out. The filter values ​​for the following parameters can be updated at each iteration of the main controller:

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[0194] Throughout this specification, macrons are used to indicate parameters that represent the average value over a patient's respiration.

[0195] Average target valve flow rate After updating the filter values ​​as described above, the main controller can calculate the estimated average target valve flow rate and the actual average valve flow rate.

number

[0196] The above equation for calculating the average target valve flow rate is similar to the equation for calculating the instantaneous valve flow rate, the only difference being that certain values ​​are replaced by filtered versions of the same parameters.

[0197] Average valve flow rate The mean valve flow rate can be estimated using a model. The mean valve flow rate model can estimate the flow through the valve. The model can take into account the time it takes for oxygen to mix with the ambient air and reach the sensor. In some configurations, this model can be a first-order model, an advection-diffusion equation, or a physically derived differential equation such as the Navier-Stokes equation. This model can be obtained numerically using machine learning algorithms such as neural networks. In some configurations, the mean valve flow rate can be estimated by the following equation.

number

number

[0198] However, F measured This is the oxygen fraction measured by a gas composition sensor, F controlV is the oxygen fraction resulting from the direction the measured oxygen fraction is directed, as well as the current valve position and current flow rate, and V is the effective volume between the valve outlet and the gas composition sensor. When the valve position is adjusted and the gas composition sensor is F measured Due to the delay between detecting the corresponding change in the first equation, F measured F instead control This is used. Valve flow rate (Q valve When estimating the change in valve current and F measured To deal with the delay between corresponding changes, F measured F instead control This can be used. This can be calculated by using the differential term in the second equation. Therefore F control is F measured This can function as a prediction of what it will be. As can be seen in the second equation, when the gas composition sensor is very close to the valve outlet, V will be close to zero, and F control is F measured It will be almost the same as that.

[0199] Next

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number

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[0200] The coefficients used by the controller may be inversely proportional to the time constant used in the exponential filter.

[0201] Considerations for various treatments The FdO2 controller can modify the control of the flow therapy device depending on which treatment is supplied by a particular device. In some configurations, the time constant can be set for exponential filtering based on the treatment, which in turn can set the coefficient of the controller described herein.

[0202] The time constant used for each treatment can be set based on the typical fluctuations in the flow of the treatment described above. Treatments with a more consistent flow rate may have a smaller time constant so that old data can be cleared more quickly. This can in turn result in a larger coefficient for the controller, and therefore I offset The value is adjusted in larger increments. When the total flow rate is more consistent, the current offset can be adjusted more quickly.

[0203] Conversely, treatments with more inconsistent flow rates, which allow older data to disappear more slowly, may have a smaller time constant. This can in turn result in a smaller coefficient for the PI controller, and therefore I offset The value is adjusted in smaller increments. If the total flow rate is less consistent, the current offset can be adjusted more slowly.

[0204] In addition, the filter's time constant (and thus coefficient) can be adjusted based on the flow rate set for a particular treatment. Generally, a higher flow rate results in a smaller filter time constant because the resulting flow rate is more consistent, and thus the delay between the valve and the gas composition sensor is reduced.

[0205] Targeted oxygen alarm In addition to controlling the valve to achieve the target FdO2, the main controller can also continuously evaluate whether the target FdO2 can be achieved. The main controller can set a precision threshold for the FdO2 algorithm. The precision threshold may increase with the value of the target FdO2.

[0206] An alarm can be generated if it is determined that the oxygen level is too high. In some configurations, an alarm is generated if the following two criteria are continuously met for at least a specified period (e.g., 8 seconds or more): (i) the measured FdO2 is greater than the target FdO2 by an amount greater than the precision threshold, and (ii) the estimated current offset is at its minimum expected value. The period can be any specified period.

[0207] If the measured FdO2 remains below the threshold for a specified period (for example, longer than 2 seconds), the determination that oxygen levels are too high and the corresponding alarm are cleared.

[0208] If the following two criteria are continuously met over a specified period (e.g., 5 seconds or more), it is determined that the oxygen level is too low and an alarm is generated. The two criteria are: (i) the measured FdO2 is below the target FdO2 by an amount greater than the precision threshold, and (ii) the estimated current offset is at its maximum expected value.

[0209] If the measured FdO2 then exceeds the threshold for a specified period (for example, longer than 2 seconds), the determination that oxygen is too low and the corresponding alarm are cleared. The period for which each threshold turns the corresponding alarm on or off can be any specified period, and may be different from or the same as other thresholds.

[0210] Oxygen filtering for display The controller can continuously obtain measurements of effective FdO2. Effective FdO2 can be calculated by filtering the measured total amount of oxygen supplied to the patient and dividing that value by the filtered measured amount of all gases supplied to the patient.

number

[0211] The controller can then alternately display the target FdO2 and the effective FdO2. If the effective FdO2 is sufficiently close to the target FdO2, it is preferable to simply display the target FdO2, as this target value is within the defined threshold range. Alternatively, if the effective FdO2 differs significantly from the target FdO2, the effective FdO2 is displayed instead. In this case, the target FdO2 may not be within the defined threshold range and may not be considered an accurate representation of the FdO2 being supplied to the patient.

[0212] If the device is operating in low-pressure mode (for example, if the device is set up to receive oxygen through a low-pressure port), the target FdO2 can be considered to be 21%.

[0213] The controller can determine whether the effective FdO2 is close enough to the target FdO2 by taking the difference between two values ​​and comparing it to a threshold. If the device is displaying effective FdO2, it switches to displaying target FdO2 if the difference falls below a first threshold. If the device is displaying target FdO2, it switches to displaying effective FdO2 if the difference exceeds a second threshold. The second threshold may be higher than the first threshold. For example, the first threshold may be 0.5% and the second threshold may be 2.5%. The first threshold may also be the same as the second threshold. For example, both the first and second thresholds may be 2.5%.

[0214] In addition, the first and / or second thresholds can be determined at least in part based on the precision threshold used for hyper / hypoxia alarms. Using precision thresholds can help ensure that flow therapy devices do not generate hyper / hypoxia alarms while also displaying target FdO2.

[0215] Oxygen storage process Referring again to Figure 1A, the controller 13 can be programmed with or configured to perform an oxygen conservation process for controlling the operation of the flow therapy device 10. The oxygen conservation process can work in conjunction with the closed-loop and open-loop control systems disclosed herein. The oxygen conservation process can be configured to conserve oxygen while ensuring that the patient's SpO2 reaches and consistently maintains that level or near that level.

[0216] The oxygen conservation process described herein reduces total oxygen use without reducing the effective FdO2 obtained by the patient during inhalation. The oxygen conservation process can adjust the oxygen flow control valve so that the FdO2 for at least a portion of the exhalation period is below the target FdO2.

[0217] To ensure that the FdO2 supplied to the patient is quickly returned to the FdO2 target level for the inspiratory period, the oxygen conservation process can adjust the oxygen flow control valve at the end of exhalation and / or the start of inspiration to supply an increased amount of oxygen-enriched gas exceeding the FdO2 target. To ensure that FdO2 is again returned to the FdO2 target level, the oxygen conservation process can adjust the oxygen flow control valve downward.

[0218] The advantage of the oxygen conservation process is that it reduces the amount of auxiliary gas (e.g., oxygen) used by flow therapy equipment without significantly affecting the treatment provided to the patient. The oxygen conservation process can be beneficial in that it allows oxygen to be conserved during the exhalation phase while continuing to provide the desired treatment by achieving the target FdO2 during the inspiratory phase. The oxygen conservation process is also beneficial because it reduces the amount of oxygen dissipated into the surrounding environment, and the reduced amount of oxygen used reduces costs for the user. The oxygen conservation process can also reduce the frequency with which the user has to replenish or replace oxygen sources such as oxygen canisters.

[0219] Determining the duration of respiratory As used herein, “respiratory period” may refer to a complete respiratory cycle of a patient, consisting of an inspiratory period and an expiratory period. The inspiratory period includes the entire inspiratory cycle, and the expiratory period includes the entire expiratory cycle.

[0220] As used herein, “respiratory phase” may refer to discrete time positions within the inspiratory or expiratory period.

[0221] To conserve oxygen without reducing the effectiveness of the treatment, the oxygen conservation process can reduce the oxygen supplied during exhalation while returning the FdO2 at the patient interface to a target FdO2 level by the start of each inspiratory period. To do this, the controller 13 can generate a model of the patient's respiratory cycle. The controller 13 can control and / or receive signals from components of the flow therapy device 10. The controller 13 may be configured to analyze the patient's respiratory cycle and determine the patient's respiratory model. For example, the controller can generate a waveform representing the patient's respiratory period. The controller 13 can also estimate the instantaneous oxygen fraction of the gas leaving the patient interface.

[0222] Figure 21 shows the waveform of the measured flow during respiration in a high-flow system. In a high-flow system, the gas flow rate can be kept at a relatively constant level. However, due to the speed of the blower control algorithm, slight flow fluctuations may still occur, particularly an increase in flow rate during inspiration and a decrease in flow rate during expiration.

[0223] The controller 13 can determine the respiratory period and / or respiratory phase by analyzing the flow rate fluctuations. The respiratory period and / or respiratory phase can be determined using a combination of measurements. For example, by analyzing a combination of flow rate and motor speed, an estimate of the circuit resistance can be calculated. The resistance fluctuates periodically with the patient's respiration. Examples of embodiments of systems and methods for analyzing and determining a patient's respiratory rate are further described in International Publication PCT / IB2018 / 059195 and International Publication PCT / NZ2017 / 050063, which are incorporated herein by reference in their entirety.

[0224] The respiratory period of the patient can be determined by frequency analysis (such as FFT) or time-domain analysis (such as zero-crossing). The control of FdO2 can be performed based on a triggering system, and the controller 13 can identify one or more indications of the transition between inhalation and exhalation (and vice versa), and use that indication to initiate the adjustment of FdO2.

[0225] In some embodiments, the controller 13 can wait until the respiratory cycle of the patient is determined to be consistent, and then start executing the oxygen conservation mode based on the control cycle corresponding to the respiratory period of the patient. Then the controller can adjust or pause the control cycle if the respiratory period of the patient changes.

[0226] Since the conservation of oxygen depends on the accuracy of the characterization of the patient's respiratory cycle, the controller can be configured to execute the operation of the oxygen conservation mode when the characterization of the patient's respiratory cycle meets a certain reliability threshold. The reliability threshold is more likely to be met when the patient is breathing consistently with a sufficiently high tidal volume. In situations where the respiratory cycle of the patient cannot be reliably characterized, the controller 13 can execute a default treatment mode instead of the oxygen conservation mode. In the default treatment mode, as further described herein, the controller is configured to meet the target FdO2 at substantially every point in the patient's respiratory cycle.

[0227] Advection-diffusion calculation If the oxygen conservation process supplies the gas flow with a relatively consistent FdO2 over time, the FdO2 can also be considered to be consistent over the length of the respiratory circuit. However, if the FdO2 varies over time, the FdO2 at a specific moment can be different at various positions within the respiratory circuit. Specifically, the measurement of FdO2 by the gas composition sensor within the device may not match the FdO2 at the patient interface. To ensure that the correct FdO2 is supplied to the patient, an estimation of the FdO2 at the patient interface can be calculated over time based on the FdO2 measured in the device.

[0228] There are two main factors that cause a difference between the FdO2 measured in the device and the FdO2 in the patient interface. The first factor is the delay caused by the movement of gas between two positions that result in peaks and troughs in the FdO2 value in the patient interface, and such peaks and troughs may be offset in the time domain by the corresponding peaks and troughs of the FdO2 measurement in the device. The second factor is that a certain amount of mixing occurs when gas moves through the circuit, causing a reduction in the amplitude of the oxygen concentration waveform at a position further downstream within the breathing circuit.

[0229] Both of these factors can be addressed using the advection-diffusion equation. The advection-diffusion equation includes an advection term to address the aforementioned delay and a diffusion term to address the aforementioned mixing. Equation (1) is an example of an embodiment of the advection-diffusion equation:

Number

[0230] The advection-diffusion equation can be numerically solved, such as by using an upwind difference method together with Crank-Nicolson time stepping. Alternatively, the advection-diffusion equation can be solved using a low-accuracy numerical scheme for the advection equation, with the diffusion term being ignored and instead obtained from the "numerical diffusion" resulting from this scheme. The accuracy of this second method may be low, but it can save computational power.

[0231] FIG. 22 shows an example of a chart 2210 showing the results of an analysis using the above method for determining the oxygen content within the breathing circuit. Airvo2212 gives the measured oxygen percentage at the gas composition sensor within the breathing circuit. Hose end 2214 gives the measured oxygen percentage at the patient interface. Advection diffusion 2216 and cheap diffusion 2218 give the calculated estimates of the oxygen percentage at the patient interface. Chart 2220 shows the measured flow rate over the same period.

[0232] Valve control The controller 13 can use valve control algorithms to estimate the start of the expiratory and inspiratory phases of the patient's respiratory cycle, and to adjust the valve before the start of each phase so that a desired FdO2 is supplied during each phase. In particular, the controller 13 can estimate the transition from the inspiratory to the expiratory phase and adjust the valve so that the FdO2 at the patient interface begins to decrease once inspiration is complete. Similarly, the controller 13 can estimate the transition from the expiratory to the inspiratory phase and adjust the valve so that the FdO2 at the patient interface returns to a target level by the time inspiration begins.

[0233] The top priority is to deliver target FdO2 to the patient, and conserving as much oxygen as possible is a secondary priority. Therefore, FdO2 ramp-up and ramp-down may occur during the expiratory phase, with FdO2 at the patient interface being at the target level at the start of the inspiratory phase and not beginning to decrease until the inspiratory phase is complete.

[0234] There is a delay between adjusting the valve and measuring the change in FdO2 in the device, and a further delay before the change is reflected in the patient interface. The controller can compensate for this delay by predicting the onset of exhalation and adjusting the valve accordingly. In one embodiment, the onset of exhalation is estimated by observing the start of a certain exhalation period and predicting the onset time of the next exhalation period using an estimate of the patient's respiratory rate.

[0235] Based on the current flow rate, the controller can calculate the time it takes for gas to move between the valve and the patient interface. The controller can then use this time to determine when to reduce FdO2 after a certain respiratory cycle. For example, if a patient has a respiratory rate of 20 breaths / minute, one respiratory cycle is 3 seconds. If the time is 0.5 seconds, the controller can close the valve 2.5 seconds after the start of the expiratory phase to begin reducing FdO2 at the end of the next inspiratory phase.

[0236] Raising FdO2 presents a slightly more complex challenge because the controller must ensure that FdO2 at the patient interface is at or near the target level by the start of the inspiratory period. To do this, the controller determines a deadline for FdO2 at the patient interface to return to the target level after the start of exhalation. This deadline can be set to 1 to 1.5 respiratory cycles minus the travel time after the start of exhalation. Setting the deadline closer to 1.5 respiratory cycles minus the travel time increases the amount of oxygen saved, but also increases the probability that FdO2 at the patient interface may not be at the target level in time for the start of inspiration. The deadline should initially be set to a conservative value (e.g., around 1 respiratory cycle minus the travel time) and can be moved closer to the upper limit if the controller determines that the target FdO2 is being supplied to the patient interface by the start of inspiration. In use, the deadline may be approximately 1.4 respiratory cycles minus the travel time.

[0237] To ensure that the target FdO2 threshold is met, the controller can adjust the valve to supply the target FdO2 to the patient interface by the deadline. Due to oxygen diffusion within the system, even if stepwise changes are made in the valve control signal, FdO2 will ramp up over a certain period. Therefore, the controller can compensate for diffusion by adjusting the valve for a time determined based on the calculated time it takes for FdO2 at the patient interface to ramp up to the FdO2 target threshold. The period before the deadline can be called the boost period.

[0238] If FdO2 ramps up more quickly, more oxygen can be saved because oxygen can be cut off over longer portions of each exhalation period. FdO2 can ramp up more quickly by setting a higher target oxygen flow rate for the valve during the boost period. This increased target oxygen flow rate may exceed the oxygen flow rate used to achieve the target FdO2 in the target total flow rate.

[0239] Referring to Figure 23, an example of a control scheme for the oxygen conservation mode is shown. In the illustrated embodiment, the controller can calculate three target levels for operation during the oxygen conservation mode. The first level 2330 is the patient's target FdO2. The patient's target FdO2 can be determined for the patient using processes described herein, such as open-loop control and / or closed-loop control, or determined by the user. The second level 2340 is lower than the first level. The second level 2340 may be called a low level or low period. Preferably, the valve is completely closed to conserve oxygen. The third level 2350 is higher than the first level. The third level may be called a boost level or boost period.

[0240] The boost level can be an increase in the target oxygen flow rate as a multiple of the target FdO2 level of 2330. The target oxygen flow rate can be the oxygen flow rate used to achieve the target FdO2 when oxygen conservation mode is not being performed. In the illustrated example, the target oxygen flow rate is doubled during the boost period. For example, if the target FdO2 level of 2330 is 40%, then the FdO2 at boost level 2350 will be 59%. The increase in the target oxygen flow rate can be any value up to the system's maximum oxygen flow rate, because increasing the oxygen flow rate above the maximum oxygen flow rate will not increase FdO2. For example, if the target FdO2 level of 2330 is 80%, then the FdO2 at boost level 2350 may be 100% (or less than 100% if the O2 concentration of the O2 source is less than 100%).

[0241] Using a multiplier to increase oxygen during boost periods, rather than continuously supplying the maximum amount of oxygen, can help reduce the risk of exceeding the target and may allow for further adjustment of the flow rate if inhalation begins earlier than anticipated.

[0242] The boost period 2350 can extend until the deadline, after which FdO2 can return to the target level 2330. The start of the boost period 2350 can be determined based on the calculated boost period length. The calculated boost period length may depend on a set of factors. In some embodiments, the length of the period is proportional to the following: Length of time oxygen supply is cut off (low period 2340), The difference between the oxygen flow rate at the first level 2330 and the oxygen flow rate at the second level 2340, and The volume of the breathing circuit between the inhalation port and the patient interface.

[0243] The length of the boost period 2350 may be inversely proportional to the difference between the oxygen flow rate at the first level 2330 and the oxygen flow rate at the third level 2350, and to the target total flow rate.

[0244] The length of the boost period 2350 can be slightly adjusted based on a further estimate of the diffusion that may be occurring. This estimate can be based on the total flow rate.

[0245] In Chart 2320 shown in Figure 23, the controller target is the FdO2 target set by the control algorithm, where the oxygen valve is completely closed during the low period 2340, and the FdO2 during the boost period 2350 is twice the FdO2 at the first level 2330. Airvo raw measurement is the signal from the gas composition sensor, and tube end is the estimated FdO2 calculated using the advection-diffusion equation. Respiratory FiO2 is the effective FdO2, which is calculated by taking the total amount of oxygen supplied during the inspiration period and dividing it by the total volume of gas supplied over the same period. Chart 2310 shows the measured flow rates over the same period.

[0246] The example in Figure 23 concerns a patient with a respiratory rate of 20 BPM and a target flow rate of 40 LPM. Effective FdO2 is approximately at the target level, and oxygen consumption is reduced by about 15%.

[0247] In an alternative embodiment, the target oxygen flow rate during the boost period can be set to the same value as the target total flow rate, thereby providing the maximum FdO2 during the boost period. This configuration allows for the steepest possible ramp of FdO2 in the patient interface but also increases the risk of exceeding the target FdO2.

[0248] Determination of Applicability of Oxygen Conservation The controller 13 can determine whether the conditions are suitable for performing the operation of the oxygen conservation mode. The controller can determine whether to execute the oxygen conservation mode based on one or more factors. In addition, the controller can continuously monitor each of the various factors during operation to determine whether to enter or exit the oxygen conservation mode.

[0249] Since the oxygen conservation mode relies on an accurate analysis of the patient's respiratory cycle, one factor is whether the modeling of the patient's respiratory cycle is accurate enough. The controller can execute the oxygen conservation mode only if the determined reliability threshold for the modeling of the patient's respiratory cycle is met by the analysis. The controller can calculate a reliability metric related to the model of the patient's respiratory cycle and compare the calculated reliability metric with the reliability threshold.

[0250] Another factor is the amount of oxygen to be conserved. The oxygen conservation mode conserves oxygen during the low period but also uses an increased amount of oxygen during the boost period. The controller can compare these two values and execute the oxygen conservation mode only if the predicted amount of oxygen savings during the low period exceeds the increase in oxygen use during the boost period. Alternatively, the controller can execute the oxygen conservation mode only if the total reduction in oxygen used meets a determined threshold.

[0251] Another factor may be based on the analysis of target flow rate and respiratory rate. As can be seen in the advection term of the advection-diffusion equation, the transfer time between the device and the patient interface increases when low flow rates are used. Therefore, controlling FdO2 becomes easier at higher flow rates. In addition, as the patient's respiratory rate increases, the length of each respiratory cycle shortens, and consequently the controller must transition between various control periods more frequently, requiring more accurate prediction of inspiratory and expiratory transitions.

[0252] Oxygen conservation becomes even more difficult, especially at low flow rates combined with high respiratory rates, for two main reasons. First, the transfer time begins to become very long relative to the length of the respiratory cycle, requiring valve changes to occur even earlier than the transition between inspiration and expiration, which introduces further potential for error. Second, while frequent transfers of FdO2 are achievable by valves, low gas flow rates allow for increased mixing before reaching the patient interface, thus reducing the resulting fluctuations in FdO2. If the controller maintains the target FdO2 during the inspirational phase, the amount of oxygen that can be conserved becomes very small.

[0253] The controller can further determine whether to execute oxygen conservation mode based in part on the relationship between the target flow rate and the patient's respiratory rate. For example, the execution of oxygen conservation mode may depend on the ratio of flow rate to respiratory rate exceeding a threshold.

[0254] Executing oxygen conservation mode Figure 24 shows one embodiment of a flowchart for performing an oxygen-conserving mode during a treatment session. Process 2400 may be implemented by a controller or control system configured to control the operation of the flow therapy device. For example, process 2400 may be implemented in whole or in part by the controller 13 of the flow therapy device 10.

[0255] In block 2410, the controller can analyze the patient's respiratory cycle. The controller 13 may be configured to determine the patient's respiratory model based on the analysis. For example, the controller can generate a waveform representing the patient's respiratory duration. The respiratory duration and / or respiratory phase can be determined using a combination of measurements. The patient's respiratory cycle can be determined by frequency analysis (e.g., FFT) or time-domain analysis (e.g., zero crossing).

[0256] In block 2420, the controller determines the target FdO2 level for the treatment session. This may be referred to as the first level. The patient's target FdO2 level can be determined for the patient using various processes described herein, such as open-loop control and / or closed-loop control, or by the user. The target FdO2 level may represent the flow rate of an auxiliary gas (e.g., oxygen) required to achieve the target gas composition based on the total gas flow rate.

[0257] In block 2430, the controller determines the low FdO2 level. The low FdO2 level is a second level, lower than the target FdO2 level. The low FdO2 level may be the ambient oxygen level. The low FdO2 level can be achieved by completely cutting off the flow of an auxiliary gas (e.g., oxygen). For example, controller 13 may be configured to completely close a valve.

[0258] In block 2440, the controller determines the boost FdO2 level. The boost FdO2 level is a third level and is higher than the target FdO2 level. The boost level can be an increase in the target oxygen flow rate as a multiple of the target FdO2. For example, the boost level could be twice the target FdO2 level. The increase in the target oxygen flow rate can be any value up to the system's maximum oxygen flow rate. Using a multiple factor to increase oxygen during the boost period rather than always supplying the maximum amount of oxygen can help reduce the risk of exceeding the target and may allow for further adjustment of the flow rate if inspiration starts earlier than expected.

[0259] In block 2450, the controller determines the timing of each level during the respiratory period. The controller can determine the duration and timing of the target FdO2 period, the low FdO2 period, and the boost FdO2 period. Each period may span a portion of the respiratory period.

[0260] In block 2460, the controller controls the valve operation based on the determined level and timing characteristics of the patient's respiratory cycle and the determined characteristics of each level. Controller 13 can adjust the valve in operation based on the determined periods so that the desired FdO2 is supplied during each period. In particular, controller 13 can estimate the transition from the inspiratory to the expiratory period and adjust the valve so that FdO2 drops from the target FdO2 level to the low FdO2 level once inspiration is complete. Controller 13 can identify the transition from the low FdO2 level to the boost FdO2 level and adjust the valve so that FdO2 moves from the low FdO2 level to the boost FdO2 level. Controller 13 can estimate the transition from the expiratory to the inspiratory period and adjust the valve so that FdO2 returns from the boost FdO2 level to the FdO2 target level by the time inspiration begins.

[0261] In addition, the controller can continuously monitor and adjust various level and timing characteristics based on a continuous analysis of the patient's respiratory cycle. The controller can determine whether the conditions are suitable for the continued operation of the oxygen conservation mode. One embodiment of the factors for determining whether to transition to a different operating mode is described further in relation to the process shown in Figure 25.

[0262] Process for selecting oxygen conservation mode Figure 25 shows one embodiment of a flowchart of the process for determining whether to use oxygen conservation mode during a treatment session. Process 2500 may be implemented by a controller or control system configured to control the operation of the ventilator. For example, process 2500 may be implemented in whole or in part by the controller 13 of the ventilator 10.

[0263] In block 2510, the controller can analyze the patient's respiratory cycle. The oxygen conservation process can be configured to run if the characterization of the patient's respiratory cycle meets a certain confidence threshold. The oxygen conservation mode relies on an accurate analysis of the patient's respiratory cycle. The controller can run the oxygen conservation mode only if the analysis meets a defined confidence threshold for modeling the patient's respiratory cycle. The controller can calculate confidence metrics related to the model of the patient's respiratory cycle.

[0264] In block 2520, the controller can determine whether the confidence threshold for implementing oxygen conservation mode is met by comparing the confidence metric with the confidence threshold. If the patient's respiratory cycle cannot be confidently characterized and the confidence threshold is not met, the oxygen conservation process can operate in standard treatment mode, and this process can proceed to block 2550. If the threshold is met, this process proceeds to block 2530.

[0265] In block 2530, the controller can determine the operational characteristics of operation in oxygen conservation mode. These operational characteristics may include oxygen conservation characteristics, which can be used to determine how much oxygen is conserved by operating in oxygen conservation mode. Oxygen conservation mode conserves oxygen during low-flow periods and also uses an increased amount of oxygen during boost periods. The system can determine and compare these two values ​​to assess the predicted amount of oxygen conservation. Operational characteristics may include target flow rate and patient respiratory rate. Oxygen conservation can be particularly challenging at low flow rates combined with high respiratory rates. The controller can determine the flow rate-to-respiratory rate ratio.

[0266] In block 2540, the controller can determine whether the operating threshold for implementing the oxygen conservation mode is met. The controller can compare the oxygen conservation characteristics to the oxygen conservation threshold to determine whether the total oxygen reduction meets the oxygen conservation threshold. In addition, the flow rate and respiratory rate rations can be compared to separate thresholds. If any of the defined thresholds are not met, the process proceeds to block 2550. If the thresholds are met, the process proceeds to block 2560.

[0267] In block 2550, the controller operates the system in standard mode (described in more detail herein), in which the controller is configured to maintain the target FdO2 at almost every point in the patient's respiratory cycle. In block 2510, the controller can continue to analyze the characteristics of the patient's respiratory cycle to determine whether to continue operating in standard mode or switch to oxygen conservation mode.

[0268] In block 2560, the controller operates the system in oxygen-conserving mode, in which the controller operates the valve using three different levels, which are described in more detail in Figure 24. In block 2510, the controller can continue to analyze the characteristics of the patient's respiratory cycle to determine whether to continue operating in oxygen-conserving mode or switch to standard mode.

[0269] Analysis to determine whether to continue using oxygen conservation mode or switch to oxygen conservation mode can be performed at predetermined intervals. For example, the predetermined interval may be after each respiratory period, after every other respiratory period, or after a predetermined number of respiratory periods. The analysis may be performed based on any appropriate time increment, such as every second, every 5 seconds, or any predetermined time increment. The determined interval may be based on the operating characteristics of the current mode and / or the patient characteristics.

[0270] Configuration of motor and / or sensor module Figures 3 to 5 show the configuration of the flow therapy device 10. The flow therapy device includes a main housing 100. The main housing 100 has a main housing upper chassis 102 and a main housing lower chassis 202.

[0271] As shown in Figures 3 and 4, the lower chassis 202 has a motor recess 250 for receiving a removable or non-removable motor and / or sensor module 400, as shown in Figures 3 to 5 and described in more detail below. An opening 251 of the recess for receiving the removable or non-removable motor / sensor module 400, as shown in Figures 3 to 5 and described in more detail below, is provided in the bottom wall 230 adjacent to the rear end of the bottom wall 230.

[0272] Figures 5 to 8 show the motor and / or sensor module 400 in more detail. As discussed above, the lower chassis 202 includes a recess 250 for receiving the motor and / or sensor module 400.

[0273] In the configurations shown in Figures 5 to 8, the motor and / or sensor module or subassembly 400 includes a stacked configuration of three main components: a base 403 of the subassembly 400 (on which the motor 402 is placed), an exhaust gas flow path and sensing layer 420 placed on the base 403, and a cover layer 440. The base 403, sensing layer 420, and cover layer 440 combine to form a subassembly housing, which has a shape complementary to the shape of the recess 250 so that the subassembly 400 can be received in the recess 250. The base 403 is configured to close the opening 251 of the recess when the subassembly 400 is placed in the recess 250. The subassembly 400 can be held in place in the recess by any suitable means, such as fasteners, clips, or a quick-release configuration, or by being fixed or non-removable.

[0274] The sensing layer includes a gas channel having one or more sensors, and the gas channel is configured to supply gas to the exhaust port of the housing.

[0275] The motor 402 has a body 408 that defines an impeller chamber containing an impeller. Motor 402 can be any suitable gas blower motor, which may be, for example, the type of motor and impeller assembly described in the published International Publication No. 2013 / 009193. The contents of this specification are incorporated herein by reference in their entirety.

[0276] The gas exhaust port 406 is fluidly connected to the gas intake port of the outlet gas flow path and sensing layer 420, which is stacked on top of the motor. The layer 420 includes a body 422, which includes a plurality of mounting feet 425 that can be inserted into a plurality of mounting openings (not shown) of the base 403 to secure the body 422 to the base 403. In one configuration, the body 422 defines a gas flow path that connects the gas exhaust port 406 to the gas intake port of the gas flow path and sensing layer 420.

[0277] Body 422 defines the lower part 426 of the detection and gas flow path. Cover layer 440 has body 442 that defines the upper part 446 of the detection and gas flow path, and the shapes of the upper and lower parts 426 and 446 are substantially corresponding to each other.

[0278] As shown in Figures 6 and 7, the gas flow path includes linear, elongated gas flow sections 428 and 448. The intake port is located at the inlet end of the linear, elongated sections 428 and 448 of the gas flow path or is fluidly connected to the tangential inlet sections 430 and 450 of the gas flow path that are adjacent to it. Recesses 433, 453 and 434, 454 can be provided on both sides of the linear, elongated sections of the gas flow path.

[0279] The gas flow exhaust port 452 extends vertically through the body 442 of the cover layer 440 and is located at or adjacent to the outlet end opposite the linear elongated portions 428, 448 of the gas flow path. The gas exhaust port 452 is fluidly connected to the upper part of the motor recess 250, and the upper part of the motor recess 250 is fluidly connected to the gas flow path. In this case as well, the configuration of the walls 252 and ceiling 262 of the recess 250 ensures that if there is a gas leak from the motor / sensor module 400, the leak is released into the atmosphere rather than entering the part of the main housing 100 containing a large amount of electronic and control equipment. To maintain adequate spacing for the gas flow from the gas exhaust port 452 and the ceiling 262 of the recess, the recess 250 may include spacers such as projections that protrude downward from the ceiling 262, as shown in Figure 4.

[0280] Figure 6 shows that at least a portion of the gas flow path through and outside the motor and / or sensing module 400 has a meandering or winding configuration. For example, the direction of gas flow through the elongated sections 428 and 448 is generally opposite to the direction of gas flow from the gas exhaust port 452 to the inlet of the gas flow path through the elbow pipe 324.

[0281] As shown in Figures 7 and 8, the cover layer 440 includes a sensing printed circuit board (PCB) 456. The cover layer 440 may also include one or more temperature sensors, such as thermistors, placed within the elongated portions 428, 448 of the gas flow path. One sensor may measure the temperature of the gas, while the other acts as a redundant temperature sensor. Alternatively, one of the thermistors may be used as a reference flow sensor (for example, by using it as a constant-temperature thermistor), and the measured temperature can be used to determine the gas flow rate through portions 428, 448 of the gas flow path. One or more temperature sensors may be located on a portion of the sensing PCB 456 facing the gas flow. The sensing PCB 456 may further include other sensors, including, but is not limited to, pressure sensors, humidity sensors, and dew point sensors.

[0282] One or both of the electronic circuit boards 272 communicate or are coupled to the sensor in order to process the information received from the sensor and to operate the device 10 based on the information received from the sensor.

[0283] In an alternative configuration, the motor / impeller unit can be located away from the equipment 10. In this configuration, the module housed in the recess 250 may include only a fixed elbow pipe 324, a gas flow path for supplying gas to the liquid chamber 300, and various sensors. In an alternative configuration, the module housed in the recess 250 may include only a motor and gas flow path, without sensors.

[0284] In another alternative configuration, the motor and / or sensor module 400 does not have to be detachable from the recess 250, but can instead be permanently mounted within the recess 250. This configuration still provides the advantage of isolating the gas from the electrical / electronic components.

[0285] The flow path is compact and has reduced curves / sharp curves, which reduces flow separation and flow resistance.

[0286] The wall configuration provides a separate isolation layer for the motor and flow path configurations.

[0287] Having modular motor and / or sensor modules allows for the disassembly of various parts of the module when necessary for cleaning and / or maintenance.

[0288] Advantageously, there are no leak pathways within the motor and / or sensor module. While the motor and / or sensor module could be potential leak points, leakage within that area would result in oxygen being ventilated into the atmosphere or into the liquid chamber.

[0289] Valve module Figures 9 to 17 show a first configuration of the valve module 4001. The valve module 4001 controls the flow of oxygen and / or other gases entering the gas passage of the device 10, allowing the device 10 to adjust the ratio of oxygen entrained in the airflow. The valve module is formed as a modular unit to facilitate manufacturing, assembly, service, or replacement, for example, in the event of malfunction, routine maintenance, or future upgrades / improvements.

[0290] The valve module 4001 is inserted vertically upward into the valve module insertion port 306 in the lower chassis 202 of the main housing. In alternative configurations, the valve module may be inserted into the housing in various directions, such as forward, downward, backward, or sideways. The valve module 4001 can be detachably engaged with the main housing of the equipment, so that the valve module 4001 is substantially received within the housing and accessible from outside the housing. In some configurations, the valve module 4001 can be fixed within the main housing and not detachable. When the valve module is detachably engaged with the housing, a portion of the valve module 4001 is configured to be substantially flush with the outer wall of the housing.

[0291] Since the valve module is modular and accessible from outside the housing, the valve module can be replaced without significantly disassembling the equipment 10 and without compromising the seal of the equipment housing. Because the valve module 4001 is almost entirely housed within the housing, when it engages with the housing, it integrates with the housing and does not increase the size or volume of the housing. In addition, the components of the valve module, such as the valve 4003 and valve manifold 4011 described below, are located within the valve carrier 4051 and main housing of the equipment in use and are therefore protected during use. If the equipment 10 is accidentally bumped or dropped, this configuration significantly reduces the likelihood of damage to the valve module and its components.

[0292] The valve module includes a flow control valve 4003 configured to control the flow of gas through the valve manifold 4011. This valve is configured to control the flow of gas into a part of the equipment. For example, this valve may be configured to control the flow of gas to the filter module 1001. Alternatively, valve 4003 may be configured to control the flow of gas to another part of the equipment. The valve module 4001 and the filter module 1001 are located upstream of the blower 402 and the motor and / or sensor module 400. In some embodiments, the valve module 4001 and the filter module 1001 are located downstream of the blower 402.

[0293] The valve 4003 includes a cylindrical body 4005 and a valve member within the body.

[0294] The flow control valve can be, for example, a solenoid valve, and can be motor-driven or piezoelectrically operated.

[0295] In a solenoid valve, the valve member operates between an open position and a closed position. A solenoid valve can be a proportional valve. The degree of gas flow through the valve (i.e., the size of the valve opening) is proportional to the current supplied to the valve.

[0296] Alternatively, the solenoid valve can be controlled by a modulated input signal, thereby adjusting the valve between an open and a closed position.

[0297] Valve 4003 can be a needle valve, plunger valve, gate valve, ball valve, butterfly valve, spherical valve, etc. The valve may be a pressure-compensated type.

[0298] In some configurations, the valve is a normally shut-off valve, meaning it remains closed when the power is off. Using a normally shut-off valve prevents the connected gas supply line from continuously releasing oxygen or other gases when the equipment is powered off. In some alternative configurations, the valve is a normally open valve.

[0299] In some configurations, valve 4003 is an electrically actuated proportional solenoid valve. For example, the valve can be a μProp valve available from Staiger GmbH & Co.KG of Erligheim, Germany, an Asco202 series Preciflow valve available from Emerson / Asco Valves of New Jersey, or any other suitable type of valve.

[0300] The valve may have a coaxial inlet-outlet valve configuration.

[0301] The valve module 4001 includes a valve manifold 4011, which has a body 4013 defining a gas flow path 4015 between a valve manifold gas intake port 4017 and one or more valve manifold gas exhaust ports 4019. The valve manifold gas intake port 4017 is located axially at or toward the end of the valve manifold. In some configurations, the valve manifold 4011 has a single gas exhaust port 4019 arranged radially on the valve manifold. In some configurations, the valve manifold 4011 includes multiple valve manifold gas exhaust ports 4019 arranged radially around the valve manifold. The valve manifold exhaust ports 4019 are configured to supply gas from the valve manifold gas intake port 4017 to the gas intake port of the filter module 1001. The radial configuration of the exhaust port 4019 guides oxygen (or other gas) into the filter module, helping to minimize oxygen loss and improve entrainment efficiency. Valve 4003 is configured to control the flow of gas from the valve manifold gas intake port 4017 to the valve manifold gas exhaust port 4019. When the valve is "closed," the gas flow from the gas intake port 4017 to the gas exhaust port 4019 is obstructed. When the valve is "open," the gas flow from the gas intake port 4017 to the gas exhaust port 4019 is allowed.

[0302] To ensure a fluid connection between the valve and the valve manifold, the end 4018 of the valve manifold 4011 on the opposite side of the gas intake receives the valve 4003 and engages with the valve 4003 in a sealed manner. The end 4018 includes a flange 4023 for mounting to the valve. The flange 4023 has an opening 4023A for receiving a fastener 4023F for fastening the manifold to the valve 4003. To ensure a sealed engagement of the valve with the valve manifold, an O-ring may be provided around the interface between the valve 4003 and the valve manifold 4011.

[0303] The valve manifold 4011 guides / dissipates oxygen from the valve through radially positioned gas exhaust ports 4019. In some embodiments, a single gas exhaust port 4019 is provided within the valve manifold. Noise is generated when oxygen passes through the exhaust ports. Since this device may be used in medical and / or home environments near patients, it is desirable to minimize the noise generated.

[0304] In addition and / or, to reduce noise, a hood, duct, or channel can be formed around the valve manifold exhaust port 4019, in close proximity to the valve manifold exhaust port 4019, or by fluid connection with the valve manifold exhaust port 4019. In addition and / or, to reduce noise, foam or the like can be placed around the valve manifold, in close proximity to the valve manifold exhaust port.

[0305] To prevent dust or particles from entering the valve, a small filter can be installed inside the intake port of the valve manifold gas intake port 4017.

[0306] The end of the valve manifold corresponding to the gas intake port 4015 is configured to receive and connect to the connector 4031. In the illustrated configuration, the connector 4031 is a swivel connector. Alternatively, the connector 4031 may be configured so that the gas intake port 4033 of the connector can move in various ways, such as translational motion or rotational motion.

[0307] Valve module 4001 is located at the beginning of the device's flow path. If valve 4003 is obstructed from remaining open (i.e., by dust, particles, etc.), excess pressurized oxygen or other gases are "released" out through the ambient air inlet opening in valve carrier 4051 (for example, the opening shown below the swivel connector in Figure 26). This prevents any excessive pressure from reaching the patient. Therefore, this system can be considered essentially pressure-controlled without the use of a pressure relief valve.

[0308] An opening 4051O is provided within the valve carrier 4051 to allow ambient air to be drawn into the gas flow path of the equipment. The ambient air flow path passes near or adjacent to the valve. In the illustrated configuration, the opening 4051O is located around the gas intake port of the swivel connector. In addition, or alternatively, the opening may be located elsewhere within the valve carrier. When the equipment's blower motor 402 operates, such operation results in a suction through the filter module and valve module, drawing ambient air into the equipment. The ambient air flow path passes through the valve module, allowing the gas flow from the flow control valve to be accompanied by ambient air. The ambient air flow path has a gas exhaust port adapted to supply ambient air, thereby allowing the ambient air to pass through one or more temperature sensors of the equipment for supplying the gas flow.

[0309] The device can simultaneously draw gas from the gas intake of the valve manifold and ambient air, or pressurizing the gas from the gas intake can force the gas to pass through a filter. The gas exits the valve module and enters the gas intake in the filter. The device may be configured so that the gas from the gas intake and ambient air are dynamically encombined / mixed within the device before being supplied to the device's gas exhaust port.

[0310] The valve module may be configured to minimize pressure drops across the valve module by having a large opening 4051O for ambient air located around the swivel connector and / or elsewhere, and one or more radius / round / slope edges in the flow path (i.e., in the valve manifold) to minimize turbulence and uniform flow.

[0311] The valve module 4001 described herein is configured to be directly coupled to the filter 1001 to provide a gas flow path from the valve module to the filter. No hose connection is required between the valve module and the filter module. This configuration minimizes the size of the components and facilitates the connection and disconnection of the modular valve and filter modules.

[0312] The filter module and valve module described herein can provide a variable gas flow path to the instrument. For example, the valve module can control the flow of oxygen entering the instrument's gas flow path via the valve module and filter module. Alternatively, the valve module can be bypassed by directly connecting an alternative oxygen source to the filter module via a first sub-compartment gas intake (e.g., intake 1011 in Figure 13). This configuration may be practical in situations where the user may want to manually adjust the oxygen supply (i.e., by a wall-mounted supply rotometer, etc.).

[0313] It will be understood that the filter modules and valve modules described herein may be used separately within equipment for supplying gas flow. Alternatively, the filter and valve modules may be used together as a filter and valve assembly to improve functionality.

[0314] In the illustrated configuration, the device 10 obtains oxygen by at least one of the following: via a valve module (for automatic oxygen adjustment by the device) or via an alternative gas intake located above a filter (which allows for the installation of a manually adjustable oxygen supply, i.e., a wall-mounted supply rotometer, etc.).

[0315] The various configurations described are merely illustrative. Any one or more features of any configuration can be used in combination with any one or more features of any other configuration.

[0316] For example, swivel connectors used within valve modules can have additional functions. In some configurations, a swivel connector can be configured to pivot around one or more axes so that the gas intake of the swivel connector can rotate around two axes, for example, it may have two adjacent swivel connection parts having swivel axes that intersect each other. In some configurations, the swivel connector may include a ball and socket configuration or similar configuration to allow the gas intake of the swivel connector to rotate in substantially any direction. In some configurations, the swivel connector may be configured to perform both pivotal and translational motion so that the gas intake of the swivel connector can not only pivot around one or more axes but also move linearly, for example. This configuration may be practical for translating the gas intake from one part of a device to another, for example, from one side of the device to the opposite side. In some configurations, the gas intake can be configured to translate rather than rotate.

[0317] As another example, although it was stated that the recess for the motor and / or sensor subassembly is located at the bottom of the main housing, it may instead be located at the rear, side, front, or top of the housing. In such modifications, the air and / or oxygen intake ports may also be positioned differently as needed.

[0318] As another example, instead of configuring the liquid chamber and chamber bay so that the liquid chamber is inserted into and removed from the chamber bay from the front of the housing, the configuration may be such that the liquid chamber is inserted into and removed from the chamber bay from the side, rear, or top of the housing.

[0319] As another example, although the filter module was described as being inserted into the housing from above and the valve module from below, one or both of these components can be inserted into any suitable part of the housing, such as the top, bottom, side, front, or rear.

[0320] Filter modules and valve modules were described for flow therapy devices capable of supplying heated and humidified elements to patients or users. The devices may be suitable for treating chronic obstructive pulmonary disease (COPD). The devices may be configured to supply gas (high-flow therapy), particularly high-flow nasal oxygen therapy, to the patient interface at high flow rates.

[0321] Alternatively, filter modules and / or valve modules may be used within the device for various purposes. The device can be a high-flow therapy device or a low-flow therapy device. Features can also be provided within the device to provide continuous positive airway pressure (CPAP), which can supply gas (such as humidified gas) at positive pressure.

[0322] The filter module and / or valve module can be used in place of equipment that does not require a humidifier, and therefore does not require the features of the liquid chamber 300 or chamber bay 108. For example, a configuration that isolates the motor and gas flow path from electrical and electronic components will be found to have a wide range of applications in other types of gas supply equipment.

[0323] The term "flow therapy device" is intended to encompass all such modified forms.

[0324] No reference to prior art in this specification shall be construed, nor should it be construed, as an endorsement or suggestion in any way that prior art constitutes common general knowledge in any field of focus in any country around the world.

[0325] Where terms indicating direction, such as "up," "down," "forward," "backward," "horizontal," and "vertical," are used herein, they refer to the position of the equipment in its typical use position and are used to illustrate and / or describe relative directions or orientations.

[0326] Throughout this specification and the accompanying claims, unless otherwise specified, words such as “comprise” and “comprising” should be interpreted in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is, “includes but is not limited to.”

[0327] As used herein, the terms “approximately,” “about,” and “nearly” refer to an amount close to the stated amount that still performs the desired function or achieves the desired result. For example, in some embodiments, where the context allows, the terms “approximately,” “about,” and “nearly” may refer to amounts within the range of 10% or less, 5% or less, and 1% or less of the stated amount.

[0328] No reference to prior art in this specification shall be construed, nor should it be construed, as an endorsement or suggestion in any way that prior art constitutes common general knowledge in any field of focus in any country around the world.

[0329] It can also be said more broadly that the disclosed equipment and systems consist of any or all of the parts, elements, and features mentioned or shown individually or collectively in the specification of this application, or any combination of two or more of the aforementioned parts, elements, or features.

[0330] Where the above description refers to a complete set or component having known equivalents, those complete sets are incorporated herein as if they were described separately.

[0331] Depending on the embodiment, any particular action, event, or function of any of the algorithms, methods, or processes described herein may be executed in a different order, and may be added, merged, or omitted as a whole (for example, not all of the actions or events described are necessary to implement the algorithm). Furthermore, in certain embodiments, actions or events may be executed concurrently rather than sequentially, for example, by multithreading, interrupt handling, or by multiple processors or processor cores, or on other parallel architectures.

[0332] It should be noted that various changes and modifications to the preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the disclosed apparatus and system and without diminishing its incidental advantages. For example, various components can be rearranged as desired. Thus, it is intended that such changes and modifications are included in the scope of the disclosed apparatus and system. Furthermore, not all of the features, embodiments, and advantages of the disclosed apparatus and system are necessarily required to put them into practice. Thus, it is intended that the scope of the disclosed apparatus and system is defined solely by the appended claims.

Claims

1. A respiratory device that provides a gas flow to the patient, Ambient air intake and An auxiliary air intake port for receiving auxiliary gas from an auxiliary gas source, A valve configured to control the flow rate of the auxiliary gas received by the auxiliary gas intake port, A gas composition sensor configured to measure the gas composition of a mixed flow of ambient air and auxiliary gas, A controller configured to control the supply of gas to the patient, The operation of the valve is adjusted by controlling the valve current. Determine the target auxiliary gas flow rate, Using a valve model, set the valve current based on the target auxiliary gas flow rate. A controller is configured to update the valve model over time, partially based on measurements obtained from the gas composition sensor. The respiratory system, including the respiratory system.

2. The respiratory apparatus according to claim 1, wherein the auxiliary gas contains concentrated oxygen.

3. The respiratory apparatus according to claim 1 or 2, wherein the valve model is updated over time based in part on the predicted change in the measured gas composition.

4. The respiratory apparatus according to claim 3, wherein the predicted change in the measured gas composition is at least partially based on the current valve position and the current flow rate.

5. The respiratory apparatus according to any one of claims 1 to 4, wherein the measured value of the gas composition is measured FdO2 (fraction of delivered oxygen).

6. The respiratory apparatus according to any one of claims 1 to 5, wherein the valve model is updated over time based in part on the target gas composition.

7. The respiratory apparatus according to claim 6, wherein the target gas composition is target FdO2.

8. The respiratory apparatus according to any one of claims 1 to 7, wherein the valve model is updated over time based in part on the predicted changes in the gas composition.

9. The respiratory apparatus according to claim 8, wherein the predicted change in the gas composition is at least partially based on recent trends in the measured gas composition.

10. The respiratory apparatus according to any one of claims 1 to 9, wherein the valve model includes estimating the minimum current required to open the valve.

11. The respiratory apparatus according to claim 10, wherein the estimation of the minimum current required to open the valve is updated over time.

12. The respiratory apparatus according to any one of claims 1 to 11, further comprising a flow sensor configured to measure total flow rate.

13. The respiratory apparatus according to claim 12, wherein the controller determines the target auxiliary gas flow rate based at least in part on the total flow rate.

14. The respiratory apparatus according to any one of claims 1 to 13, wherein the controller determines the target auxiliary gas flow rate based at least in part on the target FdO2.

15. The respiratory apparatus according to any one of claims 1 to 14, wherein the controller determines the target auxiliary gas flow rate based at least partially on the oxygen fraction of the ambient air.

16. The respiratory apparatus according to any one of claims 1 to 15, wherein the controller determines the target auxiliary gas flow rate based at least in part on the oxygen fraction of the auxiliary gas source.

17. The respiratory apparatus according to any one of claims 1 to 16, wherein the controller updates the valve model at various rates according to the expected range of respiratory rates.

18. The respiratory apparatus according to any one of claims 1 to 17, wherein the controller updates the valve model at various rates according to the expected flow amplitude.

19. The respiratory apparatus according to any one of claims 1 to 18, wherein the controller updates the valve model at various rates according to the flow rate.

20. The respiratory apparatus according to any one of claims 1 to 19, wherein the controller updates the valve model using a feedback loop.

21. The respiratory apparatus according to claim 20, wherein the coefficient of the return loop is adjusted in part based on the flow rate.

22. The respiratory apparatus according to any one of claims 1 to 21, wherein the valve model includes estimating the flow rate of the auxiliary gas passing through the valve.

23. The respiratory apparatus according to claim 22, wherein the estimation of the flow rate of the auxiliary gas passing through the valve is determined using at least one of a first-order model, an advection-diffusion equation, the Navier-Stokes equation, or a machine learning algorithm.

24. A respiratory device that provides a gas flow to the patient, Ambient air intake and An auxiliary air intake port for receiving auxiliary gas from an auxiliary gas source, A valve that requires a minimum amount of current to open, A gas composition sensor configured to measure the gas composition of a mixed flow of ambient air and auxiliary gas, A main controller configured to control the supply of gas to the patient, The operation of the valve opening is adjusted by controlling the valve current. The core controller is activated when the target flow rate of the auxiliary gas increases from zero. The main controller is configured as follows: Controlling the operation of the valve opening by controlling the valve current, wherein the main controller or the core controller can control the valve current, Repeatedly increasing the current supplied to the valve, After detecting the flow through the valve, the control of the valve's operation is switched to the main controller. A core controller and The respiratory system, including the respiratory system.

25. The respiratory apparatus according to claim 24, wherein the controller sets the valve current to an initial value before iteratively increasing the valve current.

26. The respiratory apparatus according to claim 25, wherein the initial value corresponds to the minimum possible current required to open the valve opening of the valve.

27. The respiratory device according to any one of claims 24 to 26, wherein the controller performs a stepwise change of the valve current during each iteration of the core controller.

28. The respiratory apparatus according to claim 27, wherein the magnitude of the stepwise change increases with each iteration.

29. The respiratory apparatus according to claim 27 or 28, wherein the magnitude of the stepwise modification is at least partially based on the target FdO2.

30. The respiratory apparatus according to any one of claims 27 to 29, wherein the magnitude of the stepped change is at least partially based on the total flow rate.

31. A respirator according to any one of claims 24 to 30, comprising a gas composition sensor.

32. The respiratory apparatus according to claim 31, wherein the flow through the valve is detected using the gas composition sensor.

33. The respiratory apparatus according to claim 31 or 32, wherein the flow through the valve is determined to occur when the concentration of the auxiliary gas exceeds the ambient level.

34. The respiratory apparatus according to any one of claims 31 to 33, wherein the flow through the valve is determined to occur when the concentration of the auxiliary gas exceeds the ambient level by an amount greater than the potential sensor error.

35. The respiratory apparatus according to any one of claims 24 to 34, wherein the auxiliary gas contains concentrated oxygen.

36. Ambient air intake ports to receive the flow of ambient air, An auxiliary air intake port for receiving auxiliary gas from an auxiliary gas source, valve and, A controller configured to control the supply of gas to a patient, Adjusting the position of the valve to control the flow rate of the auxiliary gas added to the ambient airflow, Calculating a first level, wherein the first level represents the flow rate of an auxiliary gas required to achieve a target gas composition with respect to the current total flow rate of the gas. Calculating a second level, wherein the second level represents the flow rate of the auxiliary gas and is lower than the first level. Calculating a third level, wherein the third level represents the flow rate of the auxiliary gas and is higher than the first level. The analysis involves analyzing the respiratory cycle of the patient, wherein the respiratory cycle includes continuous respiratory periods, and each respiratory period includes an inspiratory period and an expiratory period. Controlling the valve to supply the first level of auxiliary gas during each first portion of the patient's respiratory period, Controlling the valve to supply the second level of auxiliary gas during each second portion of the patient's respiratory period, and Controlling the valve to supply the third level of auxiliary gas during each third portion of the patient's respiratory period. A controller and The respiratory system, including the respiratory system.

37. The respiratory apparatus according to claim 36, wherein the auxiliary gas contains oxygen.

38. The respiratory apparatus according to claim 36 or 37, wherein the target gas composition is target FdO2 (fraction of delivered oxygen).

39. The respiratory apparatus according to any one of claims 36 to 38, wherein the auxiliary gas contains an aerosolizing agent.

40. The respiratory apparatus according to any one of claims 36 to 39, wherein the target gas composition is the concentration of the target aerosolized agent.

41. A respiratory apparatus according to any one of claims 36 to 40, further comprising a flow generator.

42. The respiratory apparatus according to claim 41, wherein the flow generator includes a blower.

43. The respiratory apparatus according to claim 41 or 42, wherein the controller is further configured to control the flow generator to supply a target flow rate.

44. The respiratory apparatus according to any one of claims 41 to 43, wherein the controller is further configured to control the flow generator to supply a flow rate that meets or exceeds the patient's inspiratory demand.

45. The respiratory device according to any one of claims 36 to 44, wherein the device provides high-flow transnasal oxygen therapy.

46. The respiratory apparatus according to any one of claims 36 to 45, wherein the first portion of the respiratory period includes at least a portion of the inspiratory period of the respiratory period.

47. The respiratory apparatus according to any one of claims 36 to 46, wherein the second portion of the respiratory period includes at least a portion of the beginning of the expiratory period of the respiratory period.

48. The respiratory apparatus according to any one of claims 36 to 47, wherein the third portion of the respiratory period includes at least a portion of the end of the expiratory period of the respiratory period.

49. The respiratory apparatus according to any one of claims 36 to 48, wherein the controller is further configured to take into account the time it takes for gas to move in the respiratory circuit between the valve and the patient interface when switching between the first level, the second level, and / or the third level.

50. The respiratory apparatus according to claim 49, wherein the controller is further configured to estimate the travel time between the valve and the patient interface.

51. The respiratory apparatus according to claim 49 or 50, wherein the controller is further configured to estimate the travel time between the valve and the patient interface based on the current total flow rate of the gas.

52. The respiratory apparatus according to any one of claims 36 to 51, wherein the second level is a fraction of the first level.

53. The respirator according to any one of claims 36 to 52, wherein the second level corresponds to the absence of an auxiliary gas flow in the ambient airflow.

54. The respiratory apparatus according to any one of claims 36 to 53, wherein the third level is a set multiple of the first level.

55. The respirator according to any one of claims 36 to 54, wherein the third level corresponds to the maximum flow rate of the auxiliary gas.

56. The respiratory apparatus according to any one of claims 36 to 55, wherein the controller is further configured to calculate a first value which is a predetermined multiple of the first level and a second value which is the maximum flow rate of the auxiliary gas, and to set the third level to the lower of the first value or the second value.

57. The respiratory apparatus according to claim 56, wherein the maximum flow rate of the auxiliary gas is determined based on the total flow rate.

58. The respiratory apparatus according to any one of claims 36 to 57, wherein the controller is further configured to calculate a moving average of the total auxiliary gas supplied throughout the entire respiratory period, and generates a conserved metric by comparing the moving average of the total auxiliary gas with an estimate of the auxiliary gas that would be used if the valve were controlled to continuously supply the first level of auxiliary gas.

59. The respiratory device according to claim 58, wherein the respiratory device is configured to display the saved metrics on the graphical user interface of the respiratory device's display.

60. The respiratory apparatus according to claim 58 or 59, wherein if the stored metric does not meet a stored threshold, the controller is configured to switch to continuously controlling the valve to supply the first level of auxiliary gas.

61. The respiratory apparatus according to any one of claims 36 to 60, wherein the controller is further configured to adjust the length of time for which at least one of the first level, the second level, or the third level is set.

62. The respiratory apparatus according to claim 61, wherein the controller is further configured to adjust the length of time based at least partially on the flow rate.

63. The respiratory device according to claim 61 or 62, wherein the controller is further configured to adjust the length of time based at least in part on the patient's respiratory rate.

64. The respiratory apparatus according to any one of claims 61 to 63, wherein the controller is further configured to adjust the length of time over which the auxiliary gas of the third level is supplied, at least in part, based on the difference between the first level and the second level.

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