Flow-activated gas supply

Abstract

To provide a device and method for monitoring oxygen or other gas and delivering it to a human or other animal, and for effectively conserving the delivery of the gas.SOLUTION: A fluid delivery system 100 provides fluid, such as supplement oxygen, to a patient 114 in response to inhalation. The fluid delivery system includes a valve assembly that is triggered by sensing onset of inspiration by measuring a change in temperature of air flow in a nasal or oral cannula, mask or helmet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to devices and methods for monitoring and delivering oxygen or other gases to humans or other animals and for effectively conserving the delivery of such gases. The present disclosure is particularly useful for the delivery of supplemental oxygen to human or animal patients and will be described with reference to such utility, although other utilities are also contemplated. [Background technology]

[0002] Today in the United States, well over 1.5 million human patients receive supplemental oxygen therapy at a cost estimated to exceed $2 billion annually. Furthermore, acute cases of COVID-19 have exacerbated the demand for supplemental oxygen, to the point that some hospitals are running out of oxygen supplies.

[0003] The majority of patients receiving long-term supplemental oxygen therapy (LTOT) suffer from chronic hypoxemia due to chronic obstructive pulmonary disease (COPD). Currently, there is no cure for this condition. However, the harmful effects of chronic hypoxemia can be mitigated by the administration of long-term oxygen therapy (LTOT). Continuous inspiration of low-flow oxygen, typically 2–3 lpm (liters per minute), through a nasal cannula increases the concentration of oxygen breathed by the patient. It is estimated that for every 1 lpm of flow, the overall inspired concentration increases by 3–4%. The increased oxygen concentration compensates for the inadequate function of the patient's lungs in absorbing oxygen.

[0004] Typically, when a patient is diagnosed with chronic hypoxemia, oxygen is prescribed at a constant flow rate based on a 20-minute titration test in the doctor's office. During the test, the patient's blood oxygen saturation is measured using an invasive blood gas analyzer or a non-invasive device, such as a pulse oximeter. While measuring blood saturation (SpO2), the patient is asked to walk on a treadmill, which can determine the amount of supplemental oxygen they require during exercise. Based on this short test, a constant flow rate of supplemental oxygen is prescribed. The patient may be advised to increase the flow rate of supplemental oxygen during exercise, such as climbing stairs, during sleep, or if they experience shortness of breath. The appropriateness of supplemental oxygen therapy should be confirmed by the patient, with the goal of maintaining the patient's oxygen saturation at 90% or above during all activities, including sleep. Some patients may be prescribed supplemental oxygen for breathing 24 hours a day, or may require supplemental oxygen only while walking, or may only require supplemental oxygen therapy during sleep. Some patients who require LTOT during waking hours often require higher flow rates during sleep. It is common to increase the flow rate by 1 liter per minute while the patient is sleeping.

[0005] If a patient needs to breathe supplemental oxygen even while at rest, they are given a stationary oxygen generating unit in their home, which can be set to produce, for example, up to 5 liters per minute of 93% oxygen. These units are typically set manually today to the prescribed liters per minute flow rate. If a patient needs supplemental oxygen while ambulatory, they usually carry a small hyperbaric oxygen tank or a small, refillable liquid oxygen dewar. Small, portable oxygen generators are also available, which can produce up to 3 liters per minute of continuous oxygen or deliver pulsed oxygen at higher flow rates. All of these portable oxygen delivery systems have drawbacks. Portable concentrators are typically bulky, noisy, and have relatively short battery life. Small hyperbaric oxygen tanks, especially the smaller ones, have limited capacity but do not require batteries or produce the types of noise caused by concentrators. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 9,707,366 [Non-patent literature]

[0007] [Non-Patent Document 1] “Long-term supplemental oxygen therapy” Up-To-Date, January 18, 2013. Brian L Tiep,MD Rick Carter,PhD,MBA [Non-patent document 2] Respiratory Care. February 2003, Vol. 48, No. 2 [Non-patent document 3] "Critical Comparisons of the Clinical Performance of Oxygen-Conserving Devices," Am. J. Respir. Crit. Care Med. May 15, 2010, 181(10), pp. 1061-1071 [Non-patent document 4] Published online, February 4, 2010, doi:10.1164 / rccm.200910-1638OC PMCID, PMC2874449 Summary of the Invention [Problem to be solved by the invention]

[0008] Due to the expense of supplying oxygen to small ambulatory cylinders and dewars, various oxygen conserving devices have been developed to conserve oxygen flow. These prior art oxygen conserving devices only deliver a short pulse of oxygen at the beginning of a patient's inspiration. By not delivering oxygen during exhalation or during the late periods of inspiration, oxygen is conserved that would not affect the patient's oxygen saturation. Currently, both pneumatic and electronic oxygen conserving devices exist, which claim to achieve oxygen conservation at ratios of 2:1 to 7:1 compared to continuous oxygen flow delivery. Such higher conservation rates are achieved by electronic devices, which are programmed to skip breaths so that oxygen pulses are delivered only during every other breath. However, electronic devices cannot be used with all ambulatory patients because such high conservation rates may actually result in a patient's oxygen saturation deficit, especially during periods of increased oxygen utilization, such as brisk walking or stair climbing.

[0009] Additionally, currently available conserving devices measure a drop in nasal air pressure that is insufficient for many patients to trigger oxygen release under a variety of circumstances, including severely compromised respiratory function, predominantly mouth breathing, walking and talking, brisk walking or brisk talking, or sleep. To activate these ambulatory devices, patients are "taught" to focus on nasal breathing to assist in device activation. In many cases, patients must stop their activity and focus on their nasal breathing or place a nasal cannula probe over their mouth to more effectively activate the device.

[0010] Pressure sensing of the start of inspiration in electronic oxygen conserving devices is currently performed in one of two ways. 1. Some prior art designs employ dual lumen cannulas, with one lumen dedicated to pressure sensing and the other dedicated to oxygen delivery. This design is intended to be more sensitive to the onset of inspiration, but has the drawback of only being able to deliver oxygen to one of the nasal passages. 2. Other designs use a single lumen cannula, which usually has a pressure sensor connected to the lower T-shaped sections of the two nasal prongs. The overall pressure drop associated with inspiration is sensed from both nostrils, and oxygen is delivered to both nostrils.

[0011] Both designs suffer from delays in initiating oxygen flow due to the hysteresis inherent in pressure sensing. However, even a slight delay in initiating oxygen flow is easily perceived by the patient. Another drawback of current designs using pressure sensors is that if one of the patient's nostrils becomes blocked, oxygen detection and delivery will be hindered.

[0012] Yet another drawback with current oxygen generation systems is the fact that a patient's ideal oxygen needs change over time, both in the short term as a result of various physical activities and over the long term as a result of improving or worsening health conditions. When a physician prescribes a constant flow of oxygen for a patient, the physician is primarily concerned with ensuring that the patient's blood saturation does not fall below 88-89% oxygen saturation. Physicians do not want patients to experience oxygen desaturations below 90% during any of their activities. Although theoretical concerns exist regarding potential toxicity (e.g., absorption atelectasis, increased oxidative stress, and inflammation) in patients administered high concentrations (greater than 50 percent) of oxygen for extended periods, clinical experience has provided little support for these concerns in the LTOT setting (Non-Patent Document 1).

[0013] Current oxygen treatment plans are prone to error, as reported by a study by Fussell et al. (2011) . In that study, the blood saturation levels of 20 patients suffering from COPD were continuously monitored using pulse oximetry to determine whether each patient's oxygen prescription was adequately maintaining their saturation. The study concluded that there was a low correlation between traditional oxygen administration assessment methods and continuous ambulatory oximetry during LTOT screening of COPD patients. More recently, in a study by Fussell et al. (2011) , the current collection of conserving devices, all based on pressure sensing, was critiqued for failing to meet their efficacy claims. The authors claim that "each device was activated during nasal and mouth breathing, but none performed consistently according to technical expectations."

[0014] When a patient experiences low oxygen saturation while using a conserving or constant oxygen flow, the natural response is to simply increase the flow rate; in fact, the low oxygen saturation results from a delay in activating supplemental oxygen as soon as possible at the beginning of inspiration. Increased nasal flow rates are increasingly costly and generally poorly tolerated. Some COPD patients who use stationary oxygen concentrators at home are financially challenged and concerned about the power costs of running the concentrator continuously. This often leads to compliance issues, where patients choose not to turn on the concentrator and not follow the therapy prescribed by their physician in order to save on electricity costs. Furthermore, these oxygen concentrators emit a significant amount of heat into the room, which can further add to energy costs, for example, for room cooling. Current oxygen concentrator designs typically produce a maximum flow rate of 5 liters per minute. If a patient's resting prescription is 2 liters per minute, they can set the flow rate through their cannula to the desired rate, and the excess oxygen produced may simply be forced into their nostrils and wasted during mouth breathing. Many oxygen therapy patients may spend a significant portion of their time with unacceptable blood oxygen saturation levels while active, talking, napping, or sleeping.

[0015] Current pressure-based oxygen conserving units fail to meet their claims when patients breathe through their mouths during more vigorous activities, such as talking and eating, and / or while sleeping. Often, ambulatory oxygen therapy patients must stop and focus on breathing through their nose, or place the prongs of a nasal cannula over their mouth and inhale to activate the release of oxygen. When oxygen needs are not being met, a simple solution is to increase nasal flow, thereby increasing the problem of uncomfortable dryness of the nasal passages and, sometimes, bleeding of the nasal mucosa. Furthermore, patients often turn off their oxygen delivery systems while eating.

[0016] In my prior U.S. Pat. No. 6,259,999, I describe an improved system, method, and apparatus for controlling the delivery of oxygen to a patient, which includes a nasal cannula or a combined nasal and oral cannula with a valve assembly and a flow sensor that senses "flow leakage" through the patient's nasal cavity while they breathe. This "covert signal," combined with simultaneous monitoring of nasal and / or oral flow patterns, both of which enable an on-demand oxygen delivery system without unreliable or misdirected oxygen that could result in oxygen waste or inadequate oxygen delivery to the patient. More specifically, my prior U.S. Pat. No. 6,259,999 describes a fluid delivery system including at least one source of fluid, at least one valve assembly coupled to the at least one source of fluid, the at least one valve assembly configured to allow flow from the at least one source of fluid during patient inspiration, an outlet end including a nasal or oral cannula in fluid communication with the at least one valve assembly, and a nasal flow sensor for actuating fluid delivery in response to the patient's inspiration. The fluid delivery system further includes a power source configured to operate the at least one valve assembly. The location of the nasal flow sensor may be within or adjacent to the nasal or oral cannula, adjacent to the fluid source, or in an air line between the nasal or oral cannula and at least one source of fluid. [Means for solving the problem]

[0017] The present disclosure improves upon the method and apparatus of my previous patent application, U.S. Pat. No. 6,499,133, by providing an improved trigger mechanism that activates a valve to release fluid from a fluid source for delivery to a patient via a nasal or oral cannula. The fluid delivered by this method may include oxygen. In particular, the present disclosure in one aspect provides a flow sensor that uses heater(s) and temperature sensor(s) to detect the onset of inspiration by measuring the temperature difference caused by convective cooling induced by fluid flow, and initiates flow within less than about 20 milliseconds, typically 10-20 milliseconds, of the onset of inspiration, far better than currently available pressure sensors can provide.

[0018] Also, to allow for the use of a highly sensitive mass air flow sensor, the present disclosure preferably isolates the mass air flow sensor from the oxygen flow line via a diverter valve to protect the sensor from the high pressure oxygen flow.

[0019] One aspect of the present disclosure provides a fluid delivery system for controlling delivery of a fluid to a human or animal, the system comprising: at least one source of fluid; at least one valve assembly coupled to the at least one source of fluid, the at least one valve assembly configured to allow fluid flow from the at least one source during inspiration of the human or animal; an outlet end including a nasal or oral cannula in fluid communication with the at least one valve assembly; and a flow sensor for activating fluid delivery in response to inspiration of the human or animal, the flow sensor including a temperature sensor, such as a thermistor, in fluid communication with and upstream of the nasal or oral cannula and configured to detect a temperature change indicative of the onset of inspiration by the human or animal within less than about 20 milliseconds, typically 10-20 milliseconds, of the onset of inspiration. The system may also include a power source configured to operate the at least one valve assembly.

[0020] In another aspect of the present disclosure, the flow sensor is located within or adjacent to the nasal or oral cannula, or within tubing connecting the nasal or oral cannula to at least one source of fluid. The nasal and oral cannula may be coupled together. Preferably, the delivered fluid includes supplemental oxygen, therapeutic gas, or anesthetic gas.

[0021] In one embodiment, the fluid delivery system includes an electronic circuit for controlling the at least one valve assembly based on a signal from the flow sensor. Preferably, the electronic circuit includes a trigger mechanism for actuating the release of fluid through the at least one valve assembly.

[0022] The fluid delivery system may also include a heater configured to heat the flow sensor or the fluid upstream of the flow sensor above ambient temperature.

[0023] In a preferred embodiment, the temperature sensor is configured to detect the start of inspiration and the start of expiration by directional changes in temperature, and the system optionally includes a heater located upstream and optionally downstream of the temperature sensor.

[0024] In another embodiment, the flow sensor is isolated from at least one source of fluid by a piezoelectric actuator valve.

[0025] The present disclosure also provides an apparatus for conserving fluid delivered from a fluid supply to a human or animal, comprising: a fluid conserving device controller connected between the fluid supply and a nasal or oral cannula, the fluid conserving device controller comprising at least one valve that is selectively activated to deliver fluid to the nasal or oral cannula; a flow sensor configured to sense inspiration by the human or animal; and a trigger mechanism in communication with the sensor to activate the conserving device controller, wherein the flow sensor is in fluid communication with the nasal or oral cannula and includes a temperature sensor, such as a thermistor, configured to detect a temperature change indicative of the onset of inspiration by the human or animal within less than about 20 milliseconds, typically within 10-20 milliseconds, of the onset of inspiration.

[0026] In one embodiment of the present disclosure, the flow sensor and the trigger mechanism are remote from each other, and the flow sensor and the trigger mechanism communicate either wired or wirelessly.

[0027] In a preferred embodiment of the present disclosure, the flow sensor and the trigger mechanism are remote from each other, and the flow sensor and the trigger mechanism communicate either wired or wirelessly.

[0028] In a preferred embodiment of the present disclosure, the at least one valve includes at least one valve and the fluid supply preferably includes oxygen, a therapeutic gas, or an anesthetic gas.

[0029] In one embodiment, the apparatus further includes an electrical circuit for controlling at least one valve based on a signal from the flow sensor, and / or a heater configured to heat the flow sensor or a fluid upstream of the flow sensor above ambient temperature.

[0030] In one embodiment, the temperature sensor is configured to detect the start of inspiration and the start of expiration by directional changes in temperature, and the system optionally includes a heater positioned upstream and optionally downstream of the temperature sensor.

[0031] In another embodiment, the flow sensor is isolated from the fluid supply by a piezoelectric actuator valve.

[0032] The present disclosure also provides a method for conserving fluid delivery from a fluid source to a patient, comprising the steps of: providing a valve in communication with the fluid source and a nasal or oronasal cannula worn by the patient; sensing the onset of inspiration by detecting a change in temperature of airflow through the nasal or oral cannula within approximately 15 to 20 milliseconds of the onset of inspiration using a flow sensor including a temperature sensor such as a thermistor in communication with the nasal or oral cannula; and in response to the sensed onset of inspiration, activating the valve to release fluid from the fluid source for delivery to the patient via the nasal or oronasal cannula, preferably the fluid comprising a therapeutic gas such as oxygen or an anesthetic gas.

[0033] In one embodiment, the method includes heating the flow sensor or a fluid upstream of the flow sensor above ambient temperature.

[0034] In another embodiment, the flow sensor includes a temperature sensor configured to detect the start of inspiration and the start of expiration by a directional change in temperature.

[0035] In yet another embodiment, the method includes sensing the onset of inspiration while isolating the flow sensor from the fluid source.

[0036] The present disclosure also provides a fluid delivery system for controlling the delivery of a fluid to a human or animal, comprising: at least one source of said fluid; at least one valve assembly coupled to at least one source of fluid, the at least one valve assembly configured to allow flow of fluid from the at least one source during human or animal inspiration; an outlet end including a nasal or oral cannula, a mask, or a helmet in fluid communication with the at least one valve assembly; a flow sensor for activating fluid delivery in response to human or animal inspiration; wherein the flow sensor includes a temperature sensor in fluid communication with and upstream of the nasal or oral cannula, mask, or helmet, and configured to detect a temperature change indicative of the onset of inspiration by a human or animal within less than about 20 milliseconds, preferably 10-20 milliseconds, of the onset of inspiration; wherein at least one valve assembly is configured to ramp fluid flow delivery to match the breathing pattern of the human or animal.

[0037] In one embodiment, the fluid delivery system includes a power source configured to operate at least one valve assembly.

[0038] In another embodiment, the flow sensor is located within or adjacent to the nasal or oral cannula, mask, or helmet, or within tubing connecting the nasal cannula, mask, or helmet, or oral cannula to at least one source of fluid.

[0039] In yet another embodiment, the nasal and oral cannulae are coupled together.

[0040] In yet another embodiment, the delivered fluid comprises supplemental oxygen, a therapeutic gas, or an anesthetic gas.

[0041] In a fourth embodiment, the fluid delivery system includes an electronic circuit for controlling at least one valve assembly based on a signal from the flow sensor, and the electronic circuit preferably includes a trigger mechanism for actuating the release of fluid through the at least one valve assembly.

[0042] In a particularly preferred embodiment, the at least one valve assembly is configured to ramp the fluid flow rate from a start-up rate of 15-40%, preferably 20-35%, more preferably about 33%, to 100% flow rate at human or animal inspiration.

[0043] In another embodiment, the fluid delivery system further includes a heater configured to heat the flow sensor or the fluid upstream of the flow sensor above ambient temperature, and optionally the temperature sensor configured to detect the start of inspiration and the start of expiration by directional changes in temperature, wherein the system optionally includes a heater positioned upstream and optionally downstream of the temperature sensor.

[0044] In another embodiment, the flow sensor is isolated from at least one source of fluid by a piezoelectric actuator valve.

[0045] The present disclosure also provides an apparatus for conserving fluid delivered to a human or animal from a fluid supply, comprising: a fluid conserving device controller connected between the fluid supply and the nasal or oral cannula, mask, or helmet, the fluid conserving device controller comprising at least one valve selectively activated to deliver fluid to the nasal or oral cannula, mask, or helmet; a flow sensor configured to sense inspiration by a human or animal; and a trigger mechanism in communication with the flow sensor to activate the conserving device controller, wherein the flow sensor comprises a temperature sensor in fluid communication with the nasal or oral cannula, mask, or helmet and configured to detect a temperature change indicative of the onset of inspiration by the human or animal within less than about 20 milliseconds, preferably 10-20 milliseconds, of the onset of inspiration, wherein the at least one valve assembly is configured to ramp the delivery of fluid flow to coordinate with the breathing pattern of the human or animal.

[0046] In one embodiment of the device, the flow sensor and the trigger mechanism are remote from each other, and the flow sensor and the trigger mechanism communicate either wired or wirelessly.

[0047] In a further embodiment of the device, the fluid supply comprises oxygen, a therapeutic gas, or an anesthetic gas.

[0048] In a preferred embodiment, the apparatus further includes an electrical circuit for controlling at least one valve based on a signal from the flow sensor, and optionally further includes a heater configured to heat the flow sensor or a fluid upstream of the flow sensor above ambient temperature.

[0049] In a particularly preferred embodiment, the at least one valve assembly is configured to ramp the fluid flow rate from a start-up rate of 15-40%, preferably 20-35%, more preferably about 33%, to 100% flow rate at human or animal inspiration.

[0050] In yet another embodiment of the device, the temperature sensor is configured to detect the start of inspiration and the start of expiration by a directional change in temperature, wherein the system optionally includes a heater positioned upstream and optionally downstream of the temperature sensor.

[0051] In yet another arrangement, the flow sensor is isolated from the fluid supply by a piezoelectric actuator valve.

[0052] The present disclosure also provides a method for conserving fluid delivery from a fluid source to a patient, comprising: providing a valve in communication with a fluid source and a nasal or oronasal cannula, mask, or helmet worn by the patient; sensing the onset of inspiration by detecting a change in temperature of fluid passing through the nasal or oral cannula, mask, or helmet using a flow sensor in communication with the nasal or oral cannula, mask, or helmet within less than about 20 milliseconds, preferably 10-20 milliseconds, of the onset of inspiration; and in response to the sensed onset of inspiration, actuating a valve to release fluid from the fluid source and deliver it to the patient via a nasal or oronasal cannula, mask, or helmet, wherein the valve assembly is configured to ramp the delivery of fluid flow to match the breathing pattern of the human or animal.

[0053] In a preferred embodiment of the method, the fluid comprises a therapeutic gas, such as oxygen or an anesthetic gas, and optionally further comprises heating the flow sensor or the fluid upstream of the flow sensor above ambient temperature.

[0054] In another embodiment of the method, the flow sensor includes a temperature sensor configured to detect the start of inspiration and the start of expiration by a directional change in temperature.

[0055] Yet another embodiment of the method includes isolating the flow sensor from the fluid source while sensing the onset of inspiration.

[0056] In yet another embodiment of the method, the valve assembly is configured to ramp the fluid flow rate from a start-up rate of 15-40%, preferably 20-35%, more preferably about 33%, to 100% flow rate at human or animal inspiration.

[0057] The present disclosure will be better understood from a reading of the following detailed description taken in conjunction with the drawings, in which like reference designators designate like elements and in which: [Brief explanation of the drawings]

[0058] [Figure 1] 1A-1D are block diagrams of two different systems for fluid delivery according to the present disclosure. [Figure 2] 1A-1D are block diagrams of two different systems for fluid delivery according to the present disclosure. [Figure 3] FIG. 1 is a block diagram of a remote sensor and control according to a preferred embodiment of the present disclosure. [Figure 4] 1 illustrates a schematic diagram of a start-up algorithm according to a preferred embodiment of the present disclosure. [Figure 5] 1 is a table comparing the onset of gas flow delivery by the system of the present disclosure with a conventional prior art system that uses a pressure flow sensor. [Figure 6] 1 is a flow chart of gas flow delivery of the present disclosure. [Figure 7]1 is a block flow diagram illustrating gas flow delivery according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0059] As used herein, "nasal cannula" is intended to include dual lumen nasal cannulae and nasal or pillow masks, and "oral cannula" is intended to include face masks, breathing tubes, mouthpieces, and the like, as well as diver and hazard helmets and the like.

[0060] Embodiments are described in the following description with reference to the drawings, in which like numbers represent the same or similar elements. Reference throughout this specification to "one embodiment," "one embodiment," "particular embodiment," or similar terms means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of "in one embodiment," "in an embodiment," and similar terms throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0061] The described features, structures, or characteristics of the present disclosure may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are set forth to provide a thorough understanding of embodiments of the present disclosure. However, those skilled in the art will recognize that the present disclosure may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the disclosure.

[0062] The fluid delivery system of the present disclosure provides supplemental oxygen to a human or animal intermittently based on the patient's tidal breathing. The fluid delivery system includes a nasal or oronasal flow-activated valve assembly that opens in response to the patient's inspiration and closes during the inspiratory phase, conserving oxygen that would otherwise be wasted by filling the patient's "dead space" before the end of inspiration. That is, the present disclosure senses the onset of inspiration through a temperature sensor located in the nasal or oral cannula or, in the case of a helmet, in the delivery tube, and activates a control valve to open at the onset of inspiration, i.e., within approximately 15-20 milliseconds or less of the onset of inspiration, and remain open for a time period consistent with the human or animal's tidal breathing.

[0063] The nasal or oral flow and temperature sensor is sensitive enough to detect the onset of inspiration within less than approximately 20 milliseconds, typically within 10-20 milliseconds, and sends a signal to the valve assembly to open, allowing oxygen flow for a set period of time. Opening within approximately 20 milliseconds, typically within 10-20 milliseconds, after the onset of inspiration and then remaining open for a limited time allows for a truly on-demand oxygen delivery system, as there is no uncertain or misdirected oxygen, both of which can lead to oxygen waste or inadequate oxygen delivery to the patient. Flow information at the onset of inspiration eliminates the waste associated with pulsed or continuous flow oxygen, for example. The patient or user has a comfortable sense of synchronization between the onset of breath and oxygen delivery, and by eliminating any perceptible delay in oxygen delivery, they can move about freely and converse naturally without fear of missing an oxygen pulse. Furthermore, the effectiveness of the conserving device can be utilized in hospitalized or bedridden patients in a reliable pulsed oxygen delivery system from a central fluid supply.

[0064] Furthermore, unlike pressure-flow sensors described in the prior art, sensing and activation using a temperature sensor according to the present disclosure is essentially instantaneous, i.e., within less than about 20 milliseconds of the start of inspiration, typically within 10-20 milliseconds. Therefore, there is essentially no delay in the delivery of supplemental oxygen. Also, there is no wasted oxygen compared to conventional pressure-flow sensor detectors. As a result, the flow of supplemental oxygen is essentially turned on with the start of inspiration and timed to remain on for a period of time based on the onset of the patient's tidal breath and / or upon detection of the start of exhalation. As a result, supplemental oxygen is conserved because it is not delivered when the patient does not need oxygen, i.e., to fill the "dead space" (i.e., the volume of inspired air not participating in gas exchange) or during exhalation.

[0065] As used herein, inspiration is used synonymously with inspiration, and expiration is used synonymously with expiration. Inspiration is the movement of air from the external environment through the airways into the lungs. During inspiration, the chest expands and the diaphragm contracts downward, or caudally, creating an enlarged space within the pleural cavity and negative pressure within the thoracic trunk. This negative pressure causes air to flow primarily from the nose or mouth into the pharynx (throat) and trachea, ultimately entering the lungs. By using a flow sensor in the form of a temperature sensor, determination of the onset of inspiration is essentially instantaneous, i.e., within less than approximately 20 milliseconds, typically within 10-20 milliseconds, of the onset of inspiration, utilizing the most critical phase of inspiration to deliver supplemental oxygen. While all bolus or pulsed oxygen delivery systems are set as flow equivalents, there is greater consistency and equivalence between bolus and continuous flow rates. The term "pulse equivalent," which is considered comparable to continuous flow, describes how a flow-saving regulator is set. Continuous flow rates are set to several liters per minute.

[0066] Because pulse units do not output continuous oxygen, they cannot be measured in liters per minute. Instead, they are classified by the size of the individual pulses (boluses)—how often they can be delivered per minute—and when in the inspiratory (breathing) cycle they are delivered. Another problem that can limit pulsed oxygen concentrators is when a patient attempts to breathe more per minute than the unit can produce. When this occurs, the oxygen user may get smaller pulses, fewer pulses of oxygen, or no pulses at all. If the oxygen user is exerting themselves and significantly out of breath, the unit may not be able to meet the user's needs. Using a nasal or oral flow and temperature sensor according to the present disclosure can approximate the equivalent of a continuous oxygen flow because the oxygen is delivered essentially instantly (i.e., after the user begins to inhale air, within about 20 milliseconds of the start of inspiration, typically within the range of 10-20 milliseconds). As previously mentioned, there is no delay inherent in the pressure sensor method of triggering the release of oxygen, so there is no need to increase the bolus amount to compensate for the delay in delivery.

[0067] Furthermore, the use of pulsed oxygen triggered by the onset of inspiratory flow according to the present disclosure improves sensitivity in detecting the onset of inspiration, so the user does not need to think about how they are breathing. The trigger detects the onset of inspiration due to a temperature drop via the flow sensor, even when the patient is mouth breathing, talking, walking, talking, or even eating. It does not matter whether the user has large nostrils or is dozing or asleep in a chair. No training is required; the user simply places the cannula in their nostril or mouth and feels essentially synchronized oxygen delivery. As mentioned above, while conventional pressure-flow-triggered pulsed oxygen delivery has a noticeable delay in the "puff" of delivered oxygen, the onset of inspiratory flow triggered by temperature drop according to the present disclosure has essentially no perceptible delay, providing a more natural feeling. It releases oxygen essentially as the user is inhaling, rather than after the user has begun to inhale. Compared to using conventional chest strain gauges to determine the start of inspiration, the flow sensor of the present disclosure triggered valve opening before any chest movement was detected. This improved synchronization between the start of inspiration and oxygen delivery is more comfortable, more effective, and more reliable, and results in better patient compliance by actually doing what other types of conserving units only claim to do.

[0068] A further application of the present disclosure is in the field of sleep disorder diagnosis. Much attention has been focused on sleep studies to confirm the diagnosis of sleep apnea, which is diagnosed in both sleep laboratories and home sleep studies. Sensing and confirming respiration during sleep can be improved by more accurately measuring inspiratory flow. Thus, the same nasal flow and temperature sensor that can activate pulsed oxygen delivery can also be adapted to efficiently measure respiration during diagnostic evaluations. Patients with sleep apnea or periodic breathing who use supplemental oxygen only can safely use pulsed oxygen delivery. This device could enable patients using C-PAP or Bi-PAP machines to take advantage of the efficiency of pulsed oxygen delivery, which delivers supplemental oxygen only during inspiration. This is an improvement over current methods of simply adding oxygen to a hose running to a mask, which presents a highly inefficient oxygen delivery system given the built-in mask venting and inadvertent mask leaks that occur overnight.

[0069] The presently disclosed oxygen delivery triggered by the onset of inspiration may also free ambulatory patients from the current continuous flow rate of 3 liters per minute. Using portable concentrators to set pulse rates of 4-6+ liters per minute during sleep is completely unreliable (Non-Patent Document 3, Non-Patent Document 4). While these pulsed, high-flow devices claim to be able to oxygenate patients while they sleep, most healthcare providers do not believe that pulsed, high-flow devices reliably deliver sufficient oxygen to sleeping patients.

[0070] The start of inspiration triggered oxygen delivery of the present disclosure can also be "piggybacked" onto hospital and clinic central liquid oxygen systems at the point of delivery, providing efficiencies that do not currently exist.

[0071] 1-3 of the drawings, Figure 1 is a block diagram illustrating housing components of a fluid delivery system 100 according to a first exemplary embodiment of the present disclosure. In particular, Figure 1 illustrates a fluid delivery system having a manual bypass valve configuration.

[0072] System 100 includes a housing 120, which may be a housing or similar structure containing various components used in fluid delivery, through which a supply of oxygen (O) 110 may be delivered to a patient 114. The oxygen supply 110 may include an oxygen tank 110A, a piped oxygen supply 110B from a hospital or other medical facility, or another device for delivering oxygen. Within housing 120, system 100 includes a pressure regulator 122, which is connectable to the oxygen supply 110 and regulates the pressure at which oxygen is introduced into system 100. The oxygen supply 110 may be removably attached to system 100 using a connector on pressure regulator 122. The pressure of the oxygen supply may be substantially higher, for example, up to 3,000 PSI in some cases, and on the outlet side of pressure regulator 122, the pressure can be reduced to a desired PSI, such as 15 PSI in one example. Receiving oxygen from pressure regulator 122 is a manual bypass valve 124, which allows manual control of oxygen delivery to patient 114. In particular, the manual bypass valve 124 allows the user to select oxygen delivery along a first path, known as a "pulse mode," in which pulsed oxygen delivery is controlled by the electronic controller 126, or along a second path, known as a "bypass mode," in which the controller 126 is substantially bypassed and oxygen is delivered directly or nearly directly to the patient 114.

[0073] In pulsed mode, i.e., when manual bypass valve 124 is configured to deliver oxygen to the patient under the control of controller 126, oxygen is directed to valve 128, which may be a three-port piezoelectric valve or another type. When valve 128 is de-energized, it blocks the flow of oxygen therethrough and, when energized or actuated, opens one or more of the valve ports to allow oxygen to flow therethrough. The oxygen supply to valve 128 may also be in fluid communication with oxygen pressure sensor 130 connected to controller 126 to sense the pressure of the oxygen. The output of valve 128 is connected to oxygen output 132 of system 100, which leads to patient 114. As shown in FIG. 1 , oxygen delivery to the patient may include various tubing with nasal cannula 143, which may be positioned near the patient's nose, although other delivery systems may also be used, including face masks, mouthpieces, etc.

[0074] The controller 126 also includes electronic control components, such as a microcontroller, circuitry, input and output devices, or other components that control the operation and use of the system 100, which are described in more detail with respect to FIG. 3. Generally, the controller 126 is in communication with a valve 128, an oxygen pressure sensor 130, an indicator device 134, an ambient air supply 136, and a power source 138. The ambient air supply 136 may include a port within the housing 120 to draw in ambient air and pass it through an airflow sensor 140. The airflow sensor 140 communicates with a nasal cannula 143 to provide a processor or microcontroller with ambient airflow readings and to sense the start of inspiration, as described below. The output of the ambient air supply 136 may be delivered to the patient 114 using a tube and cannula, a mask, a mouthpiece, or other delivery component, or via an ambient air outlet 142 and a dual lumen cannula as shown in FIG. 2.

[0075] The indicator device 134 may include various types of indicators, such as a keypad with visual indicators in one example. Other types of indicators may also be used. The visual indicators of the indicator device 134 may include visual indicators for operation, including standby, pulse control, sensitivity, bypass or pulsed delivery, power level, and alarms. Typically, the indicator device 134 is substantially integrated into the housing 120, but may also be a completely or partially separate device. The power source 138 may include one or more different power sources, such as a hardwired device, a user-replaceable battery, a rechargeable user-replaceable battery, or an internal rechargeable battery, which may or may not be replaceable. Of course, the power source 138 may include a combination of these or other power sources to ensure continued operation of the system 100 in the event of a failure of one of the power sources. The controller 126 may include additional components, such as an audible alarm system 144, to provide an audible alarm to the patient or another user, if desired. Additional components of the controller 126 are discussed with respect to FIG. 2.

[0076] During operation, a cannula or other delivery device is placed in proximity to the mouth or nose of the patient 114. The system 100 receives oxygen from the oxygen supply 110 and ambient air via the ambient air supply 136. When the patient inhales, negative pressure is applied to the cannula tubing and received at the oxygen output 132 and / or ambient air input 136. In pulse mode, the controller 126 is activated to deliver controlled pulsed oxygen to the patient. Activation of the controller 126 causes the controller 126 to energize the piezoelectric valve 128, thereby opening a path for oxygen to flow from the oxygen supply 110, through the pressure regulator 122, through the bypass valve 124, and to the patient 114. The controller 126 may control the specific oxygen flow to the patient 114, for example, by controlling the initiation of the oxygen pulse length, pulse rate, or other pulse characteristics that allow oxygen to pass through the valve 128, or by controlling the operation of the system 100 or the sensitivity of one or more components. During controlled pulsed oxygen delivery, the patient 114 can continue to receive ambient air through the ambient air input 136 .

[0077] The controller 126 may be activated manually, such as with a button or switch, or, more preferably, automatically by a sensed signal indicating the start of inspiration, in accordance with the present disclosure. In one example, the controller 126 may be activated by sensing a temperature change that occurs when the patient begins to inhale. In this example, a flow sensor in the form of a thermistor 140 located in the path of the ambient air supply 136 is heated to a temperature above ambient, typically 10-20°C above ambient. When the user inhales, the in-line thermistor detects a decrease in temperature due to the flow of ambient air past the heated thermistor 140. When this temperature decrease is detected, an activation signal is sent to the valve 128 to release oxygen. Alternatively, air in the path of the ambient air supply 136 located proximate thermistor 140 can be heated to a temperature above ambient temperature. When the user inhales, the thermistor may be used to detect the increase in temperature of the ambient air supply as it passes the thermistor 140 and use this to send an activation signal. In a preferred embodiment, the thermistor is configured to measure temperature change in either direction, i.e., measuring temperature change during inspiration to trigger oxygen delivery, and measuring temperature change during expiration to trigger cessation of oxygen delivery. By sensing the start of expiration, the system can also send one trigger per inspiration. After sensing inspiration to trigger a pulse of fluid, the system may prevent re-triggering on the same inspiration by inhibiting triggering until expiration is sensed.

[0078] To protect the flow sensor from the hyperbaric oxygen flow, the valve 128 includes dual-actuator piezo valves 200, 202. The piezo valve 200 is connected in-line between the supplemental oxygen source 110 and the flow sensor base 140, while the piezo valve 202 is connected to the sensor base 140 on one side and opens to ambient air on the other. Isolating the flow sensor from the hyperbaric oxygen flow allows for the use of a highly sensitive flow sensor, which can sense essentially the beginning of inspiration and then initiate an oxygen pulse at the optimal time without waste. Prior art conservators sense and deliver gas flow from the same line, which cannot sense essentially the beginning of inspiration. Isolating the flow sensor also eliminates flow contamination from the user's exhalation.

[0079] The operation of system 100 has been described thus far when the system is in pulse mode, i.e., when oxygen delivery is controlled by electronic controller 126. However, using manual bypass valve 124, a user can change system 100 from pulse mode to bypass mode to deliver oxygen directly to patient 114. As shown in FIG. 1 , in bypass mode, the supply of oxygen 110 from pressure regulator 122 can pass through manual bypass valve 124 and be directed directly or nearly directly to oxygen outlet 132, as the oxygen can pass through one or more split couplings. Thus, in bypass mode, oxygen is delivered to patient 114 without pulse control from controller 126. Using bypass valve 124, a user can control the desired operating mode of system 100 as needed, depending on the patient or application of system 100.

[0080] 3 is a block diagram illustrating an electrical block diagram of the controller 126 of the fluid delivery systems 100 and 102 of FIGS. 1-2, respectively, in accordance with a third exemplary embodiment of the present disclosure. As shown in FIG. 3, the controller 126 includes various controller circuits and processing modules that communicate with the components of the fluid delivery system. All components may communicate with a microcontroller 150, which may receive signals and process data from each component and control processing functions.

[0081] The microcontroller 150 is connected to the oxygen sensor 130 or oxygen transducer resistive bridge, such that the signal from the oxygen sensor 130 is amplified in a bridge signal amplifier and input to the microcontroller 150 via an ADC connection. An optional auxiliary oscillator may be provided in the microcontroller 150. An internal factory CAL switch or jumper may be connected to the microcontroller 150 via a CAL switch circuit. The temperature of the ambient air supply 136 may be sensed by a thermistor 140 and connected to the microcontroller 150 by a flow sensor circuit 152. Within the flow sensor circuit 152, a heater control and one or more heater drivers may be used to heat the thermistor 140 and / or the surrounding ambient supply, and a flow signal from the thermistor 140 is received by the flow sensor circuit 152. The signal may be processed by offset and / or span adjustments and then amplified before being sent to the microcontroller 150.

[0082] The piezoelectric valve 128 receives control signals from an oxygen port piezoelectric valve driver 154 and a flow sensing port piezoelectric valve driver 156, which are connected to the microcontroller 150. The oxygen port piezoelectric valve driver 154 includes a piezoelectric driver DC-DC converter, a voltage selector circuit, and a FET switch control connected to a power source and an on / off signal. The flow sensing port piezoelectric valve driver 156 includes a second piezoelectric driver DC-DC converter, a voltage selector circuit, and a FET switch control. During operation of either driver 154, 156, a signal from the voltage selector circuit is provided to the FB circuit, which provides voltage feedback to the piezoelectric driver DC-DC converter. A signal from the microcontroller received by the FET switch control is sent to the corresponding connection or drain switch of each driver 154, 156. Signals obtained from the oxygen switch of the oxygen port driver 154 and the flow sensor switch of the flow sensing driver 156 are sent to the piezoelectric valve 128 to control its energization and actuation.

[0083] The indicator device 134 may be connected to the microcontroller 150 via one or more keypad button press sensing and LED driver circuits. Similarly, the audible alarm system 144 may be connected to the microcontroller 150 using a buzz driver. A power source 138, including a hardwired or battery power source, may be connected to the microcontroller 150 using a power source selector to control power distribution. Various voltage regulators and converters may be used to power the various circuits and components of the system for fluid delivery, either directly or via the microcontroller 150 as shown in FIG. 3. Additional power supply components may be included, including power input protection circuitry, charging circuitry, battery voltage monitors, etc. An ADC test circuit 158 may also be connected to the microcontroller 150.

[0084] Further details of the present disclosure can be found in FIG. 4, which is a schematic diagram illustrating the operating algorithm of the supplemental oxygen delivery system of the present disclosure, showing how the system can prevent reactivation on the same inspiration after sensing inspiration and activating a pulse of fluid by blocking further triggering until expiration is sensed.

[0085] Table 1 in Figure 5 reports the response time for activation of supplemental oxygen flow following the start of patient inspiration using a temperature sensor in accordance with the present disclosure compared to the response time for activation of supplemental oxygen flow following the start of inspiration using conventional pressure sensors, a Chad Lotus Therapeutic Oxygen Conserver, model OM-700, and a SmartDose Oxygen Conserver, model CTOX-MN02. In testing, the temperature sensor flow sensor in accordance with the present disclosure was found to be 40 times more sensitive than conventional state-of-the-art pressure flow sensors.

[0086] FIG. 6 shows a flow chart of gas delivery according to a preferred embodiment of the present disclosure. In particular, we have discovered that by increasing the delivery of supplemental oxygen flow from the sensed onset of inspiration, supplemental oxygen is better conserved—i.e., there is little or no loss of breath past the mask or cannula—and the user is much more comfortable. This is due to the fact that switching on a fully metered flow of supplemental oxygen from a pressurized source, as is conventionally done, results in oxygen flow to the user at an initial rate far in excess of what the user can tolerate. That is, because the lungs naturally expand during breathing, the user is unable to fully uptake the target flow of supplemental oxygen fast enough for comfort and efficiency. Therefore, rather than impinging on the wearer with the full target flow of supplemental oxygen, upon detection of the onset of inspiration, the flow of supplemental oxygen is increased, essentially matching the user's breathing pattern. Typically, supplemental oxygen delivery is ramped from a start-up flow rate of 15-40%, preferably 20-35%, more preferably 33%, to 100% of the target flow at the user's peak inspiratory capacity, and then turned off or paused when or before the user begins to exhale. As an example, assuming a target flow rate of 16 liters of oxygen per minute, the oxygen flow at the start of inspiration may be initially set at 5 or 6 liters per minute, increased to 16 liters per minute as the user inhales, and then shut off when the flow sensor senses that inhalation has stopped or slowed. This is shown in Figure 7.

[0087] While the present disclosure has been described in detail with reference to certain embodiments, those skilled in the art will understand that the present disclosure can be practiced by other than the described embodiments, and that the described embodiments are presented for purposes of illustration and not limitation. For example, the above-described system can be connected to a conventional fixed flow regulator or a conventional hospital wall unit regulator, converting them into a "smart regulator." The system can also be integrated into or adapted as an add-on feature to a C-PAP mask. The system can be used to control the delivery of therapeutic gases, such as nitric oxide or anesthetic gas, or to regulate the flow of supplemental oxygen or breathing gas in mountaineering or scuba applications, fire and rescue protective equipment, space suit applications, and the like, which may use nasal or oral cannulas or sealed helmets rather than masks. Thus, as used herein, nasal cannulas and oral cannulas are intended to include masks, sealed helmets, and the like. Still other variations are possible. Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein. [Explanation of symbols]

[0088] 100 systems 110 Oxygen Supply 120 cabinet 122 Pressure Regulator 126 Electronic Controller 130 Oxygen pressure sensor 140 Airflow Sensor 143 Nasal Cannula

Claims

1. A fluid delivery system for controlling the delivery of a gas, which is a respiratory fluid, to a breathing human or animal, comprising: a first passageway capable of supplying ambient air taken in by the ambient air supply device to a discharge end portion provided on a nasal cannula, oral cannula, mask, or helmet that can be worn by the human or animal; a second passageway capable of supplying auxiliary gas from at least one auxiliary gas source to the discharge end; a flow sensor disposed on the first path between the ambient air supply and the discharge end; a first heater provided on the first path at a position upstream of the flow rate sensor; a second heater provided on the first path downstream of the flow rate sensor; a valve body provided on the second path between the auxiliary gas supply source and the discharge end portion, the valve body being capable of supplying and blocking the auxiliary gas supplied from the auxiliary gas supply source to a downstream side; Preparation, at least the first heater heats the air in the first passage above ambient temperature at a location upstream of the flow sensor; the flow sensor is capable of measuring the temperature of the gas in the first path and detecting the start of breathing based on a change in the temperature in the first path, and is used to activate the supply of the auxiliary gas in the valve body; Fluid delivery system.

2. The fluid delivery system of claim 1 , further comprising a power source configured to operate the valve element.

3. A fluid delivery system as described in claim 1, wherein the auxiliary gas includes auxiliary oxygen or an anesthetic gas.

4. The fluid delivery system of claim 1 , further comprising a control circuit for controlling the valve element based on a signal from the flow sensor.

5. The fluid delivery system of claim 4 , wherein the control circuit controls activation of the supply of the auxiliary gas by the valve body.

6. The fluid delivery system of claim 1 , wherein the first heater and the second heater are configured to heat the air in the first passage to a temperature 10 to 20° C. above ambient temperature.

7. A fluid delivery device for controlling the delivery of a gas, which is a respiratory fluid, to a breathing human or animal, comprising: a first passageway capable of supplying ambient air taken in by the ambient air supply device to a discharge end portion provided on a nasal cannula, oral cannula, mask, or helmet that can be worn by the human or animal; a second passageway capable of supplying auxiliary gas from at least one auxiliary gas source to the discharge end; a flow sensor disposed on the first path between the ambient air supply and the discharge end; a first heater provided on the first path at a position upstream of the flow rate sensor; a second heater provided on the first path downstream of the flow rate sensor; a controller including a valve body provided on the second path between the auxiliary gas supply source and the discharge end portion, the valve body being capable of supplying and blocking the auxiliary gas supplied from the auxiliary gas supply source to a downstream side; a control circuit for controlling the valve element based on a signal from the flow rate sensor; Preparation, At least the first heater is capable of heating the air in the first path above ambient temperature at a location upstream of the flow sensor; the flow rate sensor is capable of measuring the temperature of the air in the first path; the control circuit is capable of detecting the start of breathing based on a change in temperature of the air in the first path detected by the flow rate sensor, and activates the supply of the auxiliary gas through the valve body in response to the detection of the start of breathing. Fluid delivery device.

8. The fluid delivery device of claim 7 , wherein the flow sensor and the control circuit are remote from each other, and the flow sensor and the control circuit communicate either wired or wirelessly.

9. A fluid delivery device as described in claim 7, wherein the auxiliary gas includes auxiliary oxygen or an anesthetic gas.

10. A method of delivering a gas that is a respiratory fluid to a breathing animal (excluding humans), comprising: a step of cutting off the supply of the auxiliary gas to the discharge end by a valve element provided on a second path between at least one auxiliary gas supply source capable of supplying the auxiliary gas and a nasal cannula, oral cannula, mask, or helmet wearable by the animal (excluding humans), the valve element being capable of supplying and cutting off the auxiliary gas supplied from the auxiliary gas supply source to a downstream side; measuring at least the temperature of the air in the first passage by a flow sensor that is provided on a first passage capable of supplying ambient air taken in by an ambient air supply device to the discharge end, the flow sensor being capable of measuring the flow rate and temperature of the air in the first passage; heating the air in the first passage to a temperature higher than ambient temperature by a first heater disposed upstream of the flow sensor and a second heater disposed downstream of the flow sensor; detecting the start of respiratory inspiration by detecting a temperature change of the air in the first passage using the flow sensor; a delivery step of activating the valve body in response to the detected start of inspiration and delivering the auxiliary gas supplied from the auxiliary gas source to the animal (excluding humans) through the discharge end. Fluid delivery method.

11. The fluid delivery method of claim 10, wherein the auxiliary gas comprises oxygen or an anesthetic gas.

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