Methods and systems for delivering oxygen to a patient

Abstract

A system (100) for delivering oxygen comprises: an oxygen source (102); a ventilator (104) operatively connected to the oxygen source to receive a supply of oxygen from the oxygen source; a valve (109) having: a) an open position in which the ventilator receives the supply of oxygen from the oxygen source, and b) a closed position in which the ventilator is not in fluid communication with the oxygen source; a sensor (112) configured to measure respiratory flow information for the patient; and a computer system (114) for: determining a volume of gas delivered to the patient during a breathing cycle of the patient and a volume of inspiratory gas delivered to the patient during an inspiratory phase of the breathing cycle by using the respiratory flow information; and providing input to the valve based on the determined volumes, the provided input causing the valve to move between the open position and the closed position.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority under 35 USC §119(e) to U.S. Provisional Application No. 62 / 786,572, filed on December 31, 2018, the contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to methods and systems for delivering oxygen to a patient. Background Art

[0004] When a patient is mechanically ventilated, the patient is typically attached to a ventilator with a lightweight plastic breathing tube or circuit. With the advent of pressure support ventilation, the simplest and most commonly used patient circuits employ a passive exhalation valve near the patient, which is essentially just a hole in the patient circuit. This hole continuously vents gas from the patient circuit, allowing the exhaled CO2 to be removed from the patient circuit to avoid being re-breathed. Due to this leakage, the ventilator continuously produces considerable bias flow during use. This leakage is normal for normal ventilation, but if additional gas is added to the large gas flow from the ventilator, much of the potentially significant gas is either wasted or diluted or both because it never reaches the patient's airway. Two gases of particular interest are supplemental oxygen and water vapor (humidification).

[0005] When an oxygen concentrator is used to deliver a constant flow of oxygen to the low flow port of a pressure support ventilator, the effective FiO2 delivered to the patient will be reduced because most of the gas in the usual gas is discharged into the atmosphere via the exhalation valve. That is, when an oxygen concentrator is used with a non-invasive (NIV) mechanical ventilator, the gas will be delivered to the low flow port on the ventilator. The oxygen concentrator is set to a constant flow rate so that the oxygen it delivers is mixed with the air from the NIV ventilator. Most NIV ventilator circuits are passive, which means that the exhalation valve will leak continuously, resulting in only a small portion of the oxygen delivered by the ventilator being actually inhaled by the patient. Most of the gas leaves from the exhalation valve.

[0006] The waste of oxygen concentrators is not a problem, since the oxygen comes from the air in the room anyway. However, a flow rate of, for example, 5 liters per minute (L / min) is very low compared to typical gas flows down a passive flow loop, resulting in a limited FiO2 that can be delivered. On the other hand, increasing the FiO2 would be valuable.

[0007] Pressure support mechanical ventilators can also have an accessory oxygen mixing module (OBM) that has an oxygen diameter index safety system (DISS) accessory to receive wall or bottled gas with an average supply pressure of 50 pounds per square inch (psi). The ventilator then uses the oxygen mixing module to maintain the oxygen fraction of all gases leaving the ventilator to the value dialed in by the user. The only potential problem with this arrangement is that a lot of oxygen is wasted, especially when using a passive patient circuit that uses a fixed orifice to leak gas directly into the atmosphere. In such a configuration, oxygen is constantly discharged from the exhalation valve even during the exhalation phase of breathing. During normal operation in a hospital or other facility, if the patient cannot move, wall gas can be used. The oxygen entering the oxygen mixing module will be supplied from a wall source. In general, there is little worry about oxygen waste because the wall oxygen supply is sufficient. That is, when using wall gas, oxygen waste is not a big problem. However, when transporting patients in and out of the hospital and using bottled gas, the result is that the cylinder is quickly exhausted. That is, if during transport the patient requires controlled supplemental oxygen at a specific FiO2 and cannot be connected to wall oxygen, the ventilator will be connected to bottled gas. In this case, the waste of expensive, bulky, and space-consuming bottled gas is highly undesirable and, frankly, is the source of many complaints from users of such systems.

[0008] Furthermore, when bottled oxygen is used to deliver a constant flow of oxygen to the low-flow port of a pressure support ventilator, a significant amount of oxygen is wasted, particularly when using a passive patient circuit that employs a fixed orifice to leak exhaled gases directly to the atmosphere. In such a configuration, oxygen is continually exhausted from the exhalation valve even during the exhalation phase of the breath. The result is rapid depletion of the cylinder. Summary of the invention

[0009] Therefore, one or more embodiments of the present patent application provide a system for delivering oxygen. The system includes: an oxygen source; a ventilator operatively connected to the oxygen source to receive an oxygen supply from the oxygen source, the ventilator being configured to provide a gas comprising a mixture of the oxygen supply and air to a patient through a breathing circuit; a valve operatively connected to the ventilator and the oxygen source, the valve having: a) an open position in which the ventilator receives the oxygen supply from the oxygen source, and b) a closed position in which the ventilator is not in fluid communication with the oxygen source; and a computer system including one or more physical processors operatively connected to the sensor and the valve, the one or more physical processors being programmed with computer program instructions that, when executed, cause the computer system to: determine a volume of gas delivered to the patient during a breathing cycle of the patient and a volume of inspiratory gas delivered to the patient during an inspiratory phase of the breathing cycle by using respiratory flow information; and provide input to the valve based on the determined volume, the provided input causing the valve to move between the open position and the closed position.

[0010] Another aspect of one or more embodiments of the present patent application provides a method for delivering oxygen. The method is implemented by a computer system, the computer system including one or more physical processors, the one or more physical processors running computer program instructions, the computer program instructions when being executed to perform the method. The method includes: obtaining respiratory flow information for a patient from a sensor; using the computer system, determining the volume of gas delivered to the patient during the patient's respiratory cycle and the volume of inspiratory gas delivered to the patient during the inspiratory phase of the respiratory cycle by using the respiratory flow information; and using the computer system, providing an input to a valve based on the determined volume, the input provided causing the valve to move between an open position and a closed position, in which the ventilator receives an oxygen supply from an oxygen source, and in which the ventilator is not in fluid communication with the oxygen source.

[0011] Another aspect of one or more embodiments provides a system for delivering oxygen. The system includes: a unit for supplying oxygen; a unit for providing gas to a patient through a breathing circuit unit, the gas comprising a mixture of air and an oxygen supply from the unit for supplying oxygen; an opening and closing unit having: a) an open position, in which the unit for providing gas receives the oxygen supply from the unit for supplying oxygen, and b) a closed position, in which the unit for providing gas is not in fluid communication with the unit for supplying oxygen; and a unit for running machine-readable instructions using at least one processor. The machine-readable instructions include: obtaining respiratory flow information for the patient from a unit for sensing; using the unit for running, determining the volume of gas delivered to the patient during the patient's breathing cycle and the volume of inspiratory gas delivered to the patient during the inspiratory phase of the breathing cycle by using the respiratory flow information; and using the unit for running, providing an input to a valve based on the determined volume, the input provided causing the opening and closing unit to move between the open position and the closed position.

[0012] These and other objects, features and characteristics of the present patent application, as well as the function and economy of manufacture of the method of operation and related structural elements and combinations of parts, will become more apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals refer to corresponding parts in the various drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration and description only and are not intended as a definition of the limits of the present patent application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A system for delivering oxygen to a patient according to an embodiment of the present patent application is shown;

[0014] Figure 2 An exemplary ventilator with a low flow inlet according to an embodiment of the present patent application is shown;

[0015] Figure 3 An exemplary ventilator with a low flow inlet according to another embodiment of the present patent application is shown;

[0016] Figure 4 An exemplary system for delivering oxygen to a patient according to another embodiment of the present patent application is shown;

[0017] Figure 5 is a graphical representation of flow and pressure measurements for various lengths of patient circuits according to an embodiment of the present patent application;

[0018] Figure 6 is a graphical representation of delivered oxygen volume and expected FiO2 as a function of the length of the patient circuit according to an embodiment of the present patent application;

[0019] Figure 7 An exemplary system for delivering oxygen to a patient according to an embodiment of the present patent application is shown;

[0020] Figure 8 An exemplary model of a ventilator, exhaust valve, and lung showing anatomical dead space volume according to an embodiment of the present patent application is shown;

[0021] Fig. 9 shows an exemplary representation of the insertion of fresh gas from a ventilator into the lungs during one inspiratory phase according to an embodiment of the present patent application;

[0022] Fig.10 shows volume and flow traces for one breath according to an embodiment of the present patent application;

[0023] Fig.11 shows a pressure and flow rate curve according to an embodiment of the present patent application;

[0024] Fig.12 is a table showing the relationship between flow rate and circuit pressure according to an embodiment of the present patent application;

[0025] Figures 13a-13c The discharge flow and the bias flow according to the embodiment of the present patent application are shown;

[0026] Fig.14 An exemplary schematic diagram showing patient circuit hardware and flow paths according to an embodiment of the present patent application;

[0027] Fig.15 shows a flow signal corresponding to equation (7) described in the specification according to an embodiment of the present patent application;

[0028] Fig.16 A timing diagram for illustrating a timing method for on-demand delivery according to an embodiment of the present patent application is shown, wherein the top colored strips indicate the span of integrated circuit flow through the patient circuit tubing volume, and the bottom colored strips each show the duration of one complete breathing cycle;

[0029] Fig.17 shows an exemplary graphical representation of patient flow and pressure signals according to an embodiment of the present patent application;

[0030] Fig.18 FIG. 1 shows an exemplary graphical representation of the total flow of a patient circuit according to an embodiment of the present patent application, wherein V is shown within a breathing cycle. inspThe location and quantitative results;

[0031] Fig.19 FIG. 1 shows an exemplary graphical representation of the total flow of a patient circuit according to an embodiment of the present patent application, wherein the total respiratory volume V for one respiratory cycle is shown. tot The location and quantitative results;

[0032] Fig. 20 FIG. 1 shows an exemplary graphical representation of the total flow of a patient circuit according to an embodiment of the present patent application, wherein the tube volume V is shown. tube With the total volume V tot The volume contained in the difference;

[0033] Fig.21 FIG. 1 shows an exemplary graphical representation of the total flow of a patient circuit according to an embodiment of the present patent application, wherein the inspiratory gas volume V insp The delivery of is illustrated as starting at turn_on and stopping at turn_off;

[0034] Fig. 22 shows an exemplary graphical representation of the total flow of a patient circuit with a margin added to turn_on according to an embodiment of the present patent application;

[0035] Fig.23 is a table showing a sample of pipeline gas compression compliance results according to an embodiment of the present patent application;

[0036] Fig.24 In the left figure, the gas volume movement during the inhalation phase according to an embodiment of the present patent application is shown, while in the right figure, the gas volume movement during the exhalation phase according to an embodiment of the present patent application is shown;

[0037] Fig.25 An exemplary graphical representation of pressure versus flow information according to an embodiment of the present patent application is shown;

[0038] Fig.26 An exemplary graphical representation showing the percentage of water saved as a function of continuous positive airway pressure (CPAP) according to an embodiment of the present patent application is shown;

[0039] Fig. 27 An exemplary graphical representation of the percentage of water saved as the inspiratory positive airway pressure (IPAP) varies according to an embodiment of the present patent application is shown;

[0040] Fig.28 An exemplary graphical representation of the percentage of water saved as expiratory positive airway pressure (EPAP) pressure varies according to an embodiment of the present patent application is shown;

[0041] Fig.29 An exemplary graphical representation of the percentage of water saved as tidal volume varies according to an embodiment of the present patent application is shown;

[0042] Fig.30 An exemplary graphical representation showing the percentage of water saved as a function of breathing rate according to an embodiment of the present patent application is shown;

[0043] Fig.31 An exemplary graphical representation of the percentage of water saved as a function of I:E (inspiratory:expiratory ratio) according to an embodiment of the present patent application is shown;

[0044] Fig.32 An exemplary graphical representation showing the percentage of water saved with additional leakage according to an embodiment of the present patent application is shown;

[0045] Fig.33 is a table showing a summary of the range of percentage savings for each of the parameters used in the model according to an embodiment of the present patent application; and

[0046] Fig.34 A method for delivering oxygen to a patient according to an embodiment of the present patent application is shown. DETAILED DESCRIPTION

[0047] As used herein, the singular forms of "a", "an" or "the" include plural references unless the context clearly indicates otherwise. As used herein, the expression that two or more parts or components are "coupled" will mean that as long as the connection occurs, these parts are directly or indirectly (i.e., through one or more intermediate parts or components) joined or operate together. As used herein, "direct coupling" means that two elements are directly in contact with each other. As used herein, "fixed coupling" or "fixed" means that two components are coupled so as to move as a whole while maintaining a constant orientation relative to each other. As used herein, the term "or" means "and / or", unless the context clearly indicates otherwise.

[0048] As used herein, the term "integral" means a component that is created as a single workpiece or unit. That is, a component that includes workpieces that are created separately and then coupled together as a unit is not a "unitary" component or entity. As used herein, the expression "engagement" of two or more parts or components one after another means that multiple parts apply force to another directly or through one or more intermediate parts or components. As used herein, the term "several" means one or an integer greater than one (i.e., a plurality).

[0049] Directional phrases used herein (for example and not limited to, top, bottom, left, right, upper, lower, front, rear and derivatives thereof) refer to the orientation of elements shown in the drawings and do not limit the claims unless explicitly stated otherwise herein.

[0050] The present patent application provides a system 100 for delivering oxygen. The system 100 includes an oxygen source 102, a ventilator 104, a valve 108, a sensor 112, and a computer system 114. The ventilator 104 is operatively connected to the oxygen source 102 to receive an oxygen supply from the oxygen source 102. The ventilator 104 is configured to provide a gas including a mixture of the oxygen supply and air to a patient through a breathing circuit 106. The ventilator 104 is configured to mix the oxygen supply with ambient air inhaled by the ventilator 104 and provide the mixed oxygen and air to the patient through the breathing circuit 106. The valve 108 is operatively connected to the ventilator 104 and the oxygen source 102. The valve 108 has: a) an open position, in which the ventilator 104 receives an oxygen supply from the oxygen source 102, and b) a closed position, in which the ventilator 104 is not in fluid communication with the oxygen source 102. The sensor 112 is configured to measure respiratory flow information for the patient. The computer system 114 includes one or more physical processors 116 operatively connected to the sensor 112 and the valve 108. The one or more physical processors 116 are programmed with computer program instructions that, when executed, cause the computer system 114 to: determine the volume of gas V delivered to the patient during the patient's breathing cycle by using the respiratory flow information; tot and the inspiratory gas volume V delivered to the patient during the inspiratory phase of the breathing cycle insp ; and providing an input to the valve based on the determined volume, the provided input causing the valve 108 to move between an open position and a closed position.

[0051] In some embodiments, when the oxygen source 102 is an oxygen concentrator, the system 100 includes an accumulator 110 configured to accumulate the oxygen supply from the oxygen source 102 when the valve 108 is in the closed position and to provide the oxygen supply to the ventilator 104 when the valve 108 is in the open position. In some embodiments, as will be described in detail in the discussion below, when the oxygen concentrator 102 is used (as an oxygen source) through the low flow port 124 of the ventilator 104, the accumulator 110 is functionally required only to enhance the FiO2. In some embodiments, as will be described in detail in the discussion below, when the low flow cylinder gas and oxygen mixing module is used as the oxygen source through the low flow port 124 of the ventilator 104, the low flow cylinder gas and oxygen mixing module is configured to operate without a specific accumulator and obtain the oxygen saving benefits of the method of the present patent application.

[0052] In some embodiments, the computer system 114 is further configured to: obtain the tube volume V tube ; and determining the volume of gas V delivered to the patient during the patient's breathing cycle tot With tube volume V tube In some embodiments, computer system 114 is configured to provide an input to valve 108 to move valve 108 to an open position when the determined volume difference is delivered to the patient from the beginning of the next breathing cycle. In some embodiments, computer system 114 is configured to maintain valve 108 in an open position until the inspiratory gas volume is delivered to the patient during the inspiratory phase of the breathing cycle; and provide an input to valve 108 to move valve 108 to a closed position after the inspiratory gas volume is delivered to the patient.

[0053] In some embodiments, system 100 provides a flow of gas, such as a flow of oxygen, to a non-invasive ventilator (ie, a ventilator with a passive expiratory port) at a location that is not on the patient circuit and uses valve 108 to control the delivery of the gas to ventilator 104 .

[0054] In some embodiments, the system 100 is configured to increase or improve the desired inspired oxygen fraction (FiO2) from the oxygen concentrator 102 to the ventilator 104. In some embodiments, the system 100 is configured to enhance the FiO2 from the oxygen concentrator 102 to the ventilator 104. In some embodiments, the system 100 is configured to enhance the FiO2 associated with using the oxygen concentrator 102 to input to the low flow port 124 of the pressure support ventilator 104 (e.g., see Figure 2 and Figure 3 ) is associated with limited FiO2.

[0055] The present patent application provides a valve 108 that operates in concert with the breathing phase of the patient P via the ventilator 104. The valve 108 is used to shut off the flow of oxygen to the ventilator 104 and to accumulate the oxygen in the accumulator 110 to deliver oxygen the next time the valve 108 is opened to deliver oxygen to the ventilator 104. The present patent application also provides an algorithm (described in detail below) that is used in the ventilator 104 to drive the valve 108 to allow oxygen to be delivered so that oxygen only enters the ventilator 104 if oxygen is to be delivered to the patient P during the inspiratory phase of the patient P. In some embodiments, the algorithm is provided in the ventilator 104. In some embodiments, the algorithm is provided in a separate system other than the ventilator 104.

[0056] In some embodiments, the accumulator or high pressure hose 110 takes advantage of the fact that the oxygen concentrator 102 ultimately delivers gas at a pressure of approximately 8 psi. This pressure never reaches the low flow port 124 of the ventilator 104 because the gas flow to and through the ventilator 104 is unimpeded. Nevertheless, the flow can be stopped using the valve 108, which allows the pressure to accumulate to 8 psi inside the accumulator or high pressure hose 110. This allows the high pressure hose 110 to act as an accumulator, where excess oxygen is stored in the compliance of the tubing when the valve 108 is closed. Once the valve 108 is opened, the excess oxygen is released. If it happens quickly, all of the excess oxygen can be delivered during the inspiratory phase of the patient P, which has the effect of increasing the effective FiO2 compared to a normal constant oxygen flow rate.

[0057] In some embodiments, the system 100 is configured to conserve oxygen. The present patent application proposes an improved method of delivering oxygen to a patient P that also uses a non-invasive ventilator, thereby minimizing the loss (waste) of oxygen.

[0058] In some embodiments, the present patent application was conceived and developed in response to the fact that inhalation-only oxygen delivery from an oxygen mixing module (OBM) is rarely used for home ventilation. This is because home ventilator patients use an oxygen concentrator, which uses the low flow port 124, rather than the OBM. The main problem with using an oxygen concentrator is that it has a limited output (FiO2), unlike the OBM, which provides all the oxygen necessary to provide a user-specified FiO2 (21-100%) up to very high flow rates. With this practical need for an oxygen concentrator in a home ventilator, the present patent application was conceived and developed.

[0059] In some embodiments, the ventilator 104 is configured to provide ventilation support to a patient P. In some embodiments, the ventilator 104 includes a flow generator for providing a flow of gas to the patient P and a conduit 106 for delivering the flow of gas to the airway of the patient P.

[0060] In some embodiments, ventilator 104 is configured as a unit that processes software associated with opening and closing valve 108 as well as providing power to activate solenoid valve 108 .

[0061] Figure 2 A pressure support ventilator 104 is shown. To supplement the oxygen concentration in the pressure support ventilator 104, some devices provide a low flow port 124 on the back of the ventilator 104. Figure 2 The ventilator 104 is shown with a low flow port 124 . Figure 3 Another ventilator 104 having a low flow port 124 is shown.

[0062] The patient or breathing circuit 106 typically includes an inhalation channel and an exhalation channel. The inhalation channel is interconnected with the ventilator outlet so that oxygen-enriched air can be provided to the patient P through the ventilator 104. The exhaled air returns through the ventilator return port and is discharged into the surrounding environment through the exhalation channel. In some embodiments, the ventilator 104 is a portable ventilator.

[0063] In some embodiments, the ventilator 104 may also be referred to as a unit for providing gas (providing gas via the breathing circuit unit 106 to the patient P). In some embodiments, the gas includes a mixture of air and an oxygen supply from the unit for supplying oxygen 102 or oxygen source 102 .

[0064] In some embodiments, the oxygen source 102 is selected from the group consisting of an oxygen concentrator, a portable oxygen concentrator, a pressurized oxygen tank, a compressed oxygen tank, an oxygen generator, an oxygen mixing module, and an oxygen cylinder. In some embodiments, reference numeral 102 is used to refer to any of the above oxygen sources.

[0065] In some embodiments, the oxygen generator is selected from the group consisting of a chemical oxygen generator, a membrane oxygen generator, a molecular sieve oxygen generator, and a ceramic oxygen generator.

[0066] In some embodiments, the oxygen mixing module is a high pressure oxygen mixing module.

[0067] In some embodiments, the oxygen source 102 may also be referred to as a unit for supplying oxygen or a unit for providing oxygen.

[0068] In some embodiments, breathing circuit 106 is referred to as a patient circuit, a conduit, or a circuit. Figure 2 and Figure 3 As shown, the ventilator 104 includes a rear surface including an air inlet in communication with the air flow generator and an oxygen inlet 124 that can be selectively connected to the oxygen source 102 .

[0069] The system 100 includes one or more sensors 112. The sensors 112 are configured to measure respiratory flow information of the patient P. In some embodiments, the sensors 112 include a flow sensor for measuring the respiratory flow information of the patient P. In some embodiments, the respiratory flow information is measured in liters per second or liters per minute. In some embodiments, the sensors 112 include other sensors (one or more) or combinations of sensors for measuring the respiratory flow information of the patient P as will be understood by those skilled in the art.

[0070] In some embodiments, sensor 112 includes a transmitter for sending signals and a receiver for receiving signals. In some embodiments, sensor 112 is configured to communicate wirelessly with computer system 114. Figure 1 and Figure 7 As shown, in some embodiments, the sensor 112 is configured to be operatively connected to one or more physical processors 116 of the computer system 114. In some embodiments, the sensor 112 is configured to communicate with the ventilator 104. In some embodiments, the sensor 112 communicates with a database 132. In some embodiments, respiratory flow information can be obtained from the database 132, which is being updated in real time by the sensor 112. In some embodiments, the sensor 112 is in fluid communication with the respiratory or patient channel / circuit / duct / conduit 106.

[0071] In one case, the sensor 112 may provide the respiratory flow information to a computer system (e.g., including the server 114) for processing via a network (e.g., network 150). In another case, upon obtaining the respiratory flow information, the sensor 112 may process the obtained respiratory flow information and provide the processed respiratory flow information to a computer system (e.g., including the server 114) via a network (e.g., network 150).

[0072] In some embodiments, when valve 108 is in the open position, ventilator 104 is in fluid communication with oxygen source 102 such that the oxygen supply received from oxygen source 102 mixes with ambient air within ventilator 104 to supply a desired fraction of inspired oxygen (FiO2) to the patient during an inspiratory phase of a breathing cycle via breathing circuit 106. In some embodiments, the breathing cycle of patient P includes an inspiratory phase and an expiratory phase.

[0073] In some embodiments, when valve 108 is in the closed position, ventilator 104 is not in fluid communication with oxygen source 102 .

[0074] In some embodiments, valve 108 is a solenoid valve. In some embodiments, valve 108 is a solenoid valve at a low flow port 124 of pressure support ventilator 104. In some embodiments, a solenoid valve is used when the oxygen source comprises an oxygen concentrator or an oxygen cylinder.

[0075] In some embodiments, valve 108 is a servo valve. In some embodiments, valve 108 is a servo valve at a low flow port 124 of pressure support ventilator 104. In some embodiments, a servo valve is used when the oxygen source includes an oxygen mixing module.

[0076] In some embodiments, the solenoid valve 108 is controlled by the ventilator 104 and is located at the inlet of the low flow port 124 of the ventilator 104 .

[0077] In some embodiments, the open position of the valve 108 may also be referred to as an open position or valve turn_on. In some embodiments, the closed position of the valve 108 may also be referred to as a closed position or valve turn_off. In some embodiments, the valve 108 may also be referred to as an opening and closing unit.

[0078] In some embodiments, accumulator 110 is operatively connected to valve 108, oxygen source 102, and ventilator 104. In some embodiments, accumulator 110 is a high pressure hose connected between valve 108 and oxygen concentrator 102.

[0079] In some embodiments, accumulator 100 typically has a length of high pressure hose that provides a conduit connecting oxygen concentrator 102 to valve 108. In some embodiments, other associated connectors on either end of the arrangement may also be necessary.

[0080] In some embodiments, the accumulator 110 comprises any container of any size, shape, or volume. In some embodiments, the accumulator 110 is selected based on limitations associated with the ability to inflate and / or deflate the accumulator 110 within a desired time. In some embodiments, this would include a shorter hose or pipe with a larger inner diameter.

[0081] Figure 5 A graphical representation of data from an experiment is shown in which the oxygen concentrator 102 was set to deliver a constant oxygen flow of 5 liters / minute while the valve 108 was closed for approximately 4 seconds and then the valve 108 was opened for approximately 4 seconds in a sequential cycle. Figure 4 shows the method for collecting data / information (such as Figure 5 and Figure 6 The experimental setup is shown in Figure 2 .

[0082] exist Figure 5 , flow information / data for hose lengths of 0, 10, and 20 feet are shown as different dashed lines (with dashed line levels). The line pressure is also shown. Figure 5 It can be clearly seen that as the hose length increases, the volume of gas delivered increases and the circuit recharge time also increases.

[0083] Figure 5 A graphical representation of low flow oxygen delivery and comparison of pressure and volume data for various hose lengths (e.g., 0 feet, 10 feet, 20 feet) is shown. The pressure data and flow data are shown in Figure 5 The pressure data is measured in centimeters of water column (cmH2O). The volume data is measured in liters per minute (L / min). Time is shown in Figure 5 The x-axis of the graph is in seconds.

[0084] Figure 6 The results from the same experiment as for measuring oxygen volume (as in Figure 4 and Figure 5 and the related description above), in which the FiO2 is estimated for an inspiratory period of approximately 2 seconds and an assumed total inspiratory flow of 30 L / min.

[0085] Figure 6 A graphical representation of oxygen volume and FiO2 for various hose lengths is shown. The oxygen volume data over a 2 second period is shown in Figure 6 The oxygen volume data is measured in milliliters (mL). The FiO2 data for 30 liters / minute is shown in Figure 6 The FiO2 data is measured as a percentage value. The hose length is shown on the right Y-axis of the graph. Figure 6 The x-axis of the graph in the figure. Hose length is measured in feet.

[0086] The algorithm of the present patent application is a predictive algorithm that controls the use of valve 108 to deliver the relevant gas to the patient circuit 106 at the ventilator 104, so that the relevant gas appears at the patient end of the circuit 106 when the patient P begins to inhale, and the delivery of the relevant gas is stopped when the patient P stops inhaling.

[0087] The basis of the algorithm is that it uses volume measurements rather than timing to decide when to deliver gas, which makes the algorithm more robust. It is robust because such an algorithm is easy to implement and more accurate because it is less affected by noise because the volume is obtained by integrating or summing the flow rate (i.e., the integration process always reduces the noise in the system). The volume is calculated by integrating the total flow delivered from the ventilator 104 during a period defined by the beginning or end of the inspiration phase (e.g., referred to as IEState). Therefore, the only continuous input to the algorithm is the total ventilator flow and IEState. In addition, the patient circuit volume (i.e., the volume between the delivery point and the patient P, also referred to as the tube volume) is also known or must be indicated to the algorithm in some way. The output of the algorithm is simply a signal when to open the valve 108 that delivers gas / oxygen and when to close the valve 108.

[0088] The algorithm works by calculating or knowing the following: 1) The total volume V within a breathing phase or cycle tot (See Fig.19 ) ; 2) the total inspiratory gas volume V integrated from the beginning to the end of the inspiratory phaseinsp (See Fig.18 ); and 3) tube volume V tube (e.g., entered by the user or can be calculated by the ventilator—see Fig. 20 ) Based on this, calculate V tot With V tube The volume difference between Fig. 20 ) and when the volume difference (V tot -V tube )(See Fig. 20 ) when the valve 108 is opened. Fig.21 As shown, valve 108 remains open until V insp is delivered into tube 106, at which time valve 108 is closed or shut. The algorithm is predictive, meaning that it uses information from one or more previous breaths to obtain the volume to run the algorithm. Furthermore, there are some special cases, which are described in detail below.

[0089] like Figure 7 As shown, the system 100 for delivering oxygen to a patient P may include a server 114 (or multiple servers 114). In some embodiments, the server 114 includes a total inspired volume determination subsystem 212, a total breathing volume determination subsystem 214, a tube volume subsystem 216, a valve turn_on determination subsystem 218, a valve turn_off determination subsystem 220, or other components or subsystems. In some embodiments, the tube volume V tube The tube volume subsystem 216 is determined or calculated by the system 100 , and in such embodiments, may be referred to as the tube volume determination subsystem 216 .

[0090] In some embodiments, the server 114 includes a total inhaled volume determination subsystem 212, a total respiratory volume determination subsystem 214, a valve turn_on determination subsystem 218, a valve turn_off determination subsystem 220, or other components or subsystems. tube is received by system 100. That is, in some embodiments, the tube volume V tube Entered by the patient P or user / caregiver / healthcare professional.

[0091] In some embodiments, the total inhaled volume determination subsystem 212 is configured to determine the total inhaled volume V inspIn some embodiments, the total inhaled volume determination subsystem 212 is configured to receive the total flow signal Q or the respiratory flow information. In some embodiments, the total flow signal Q or the respiratory flow information is provided to the total inhaled volume determination subsystem 212 by the sensor 112. In some embodiments, the total inhaled volume determination subsystem 212 is configured to integrate the received total flow signal Q or the respiratory flow information to determine the total inhaled volume V insp For example, regarding Fig.18 and Figure 21-22 The determination of the total inhaled volume V is shown and described in detail. insp .

[0092] In some embodiments, total respiratory volume determination subsystem 214 is configured to determine total respiratory volume V tot In some embodiments, the total respiratory volume determination subsystem 214 is configured to receive the total flow signal Q or respiratory flow information. In some embodiments, the total flow signal Q or respiratory flow information is provided to the total respiratory volume determination subsystem 214 by the sensor 112. In some embodiments, the total respiratory volume determination subsystem 214 is configured to integrate the received total flow signal Q or respiratory flow information to determine the total respiratory volume V. tot For example, regarding Figure 19-21 The determination of the total respiratory volume V is shown and described in detail. tot .

[0093] In some embodiments, the tube volume subsystem 216 is configured to determine the tube volume V tube In some embodiments, the tube volume subsystem 216 is configured to receive tube volume information. In some embodiments, the tube volume information is provided to the tube volume subsystem 216 by one or more sensors associated with the tube or patient circuit 106. For example, Figure 20-21 The determined tube volume V is shown and described in detail. tube .

[0094] In some embodiments, the tube volume subsystem 216 is optional. In some embodiments, the tube volume V tube is input into the system 100 by the patient P or the user / caregiver / health care professional. In some embodiments, the tube volume V input by the patient P or the user / caregiver / health care professional tube Received directly by the valve tum_on determination subsystem 218.

[0095] In some embodiments, valve turn_on determination subsystem 218 is configured to determine when to open valve 108 or move valve 108 to its open position. In some embodiments, valve turn_on determination subsystem 218 is configured to calculate total respiratory volume V totWith tube volume V tube In some embodiments, the valve turn_on determination subsystem 218 is configured to deliver the calculated (total respiratory volume V) from the beginning of the next respiratory cycle. tot With tube volume V tube After the volume difference between the two volumes is reached, the valve 108 is opened (e.g., by sending an opening signal to the valve 108). Figure 20-22 A specific valve turn_on is shown and described in detail.

[0096] In some embodiments, the valve turn_off determination subsystem 220 is configured to determine when to close the valve 108 or move the valve 108 to its closed position. In some embodiments, the valve turn_off determination subsystem 220 is configured to determine when to close the valve 108 or move the valve 108 to its closed position after the total inhaled volume V is delivered. insp Then, the valve 108 is closed (e.g., by sending a closing signal to the valve 108). Figure 21-22 The determined valve turn_off is shown and described in detail. That is, the system 100 is configured to: maintain the valve 108 in the open position until the inspiratory gas volume is delivered to the patient during the inspiratory phase of the breathing cycle; and provide an input to the valve 108 to move the valve 108 to the closed position after the inspiratory gas volume is delivered to the patient P.

[0097] In some embodiments, the system 100 includes a valve turn_on margin determination subsystem. In some embodiments, the valve turn_on margin determination subsystem is configured to determine a margin for opening the valve 108. For example, Fig. 22 The determined valve turn_on margin is shown and described in detail with respect to equations (20)-(23).

[0098] As will be apparent from the above and following discussions, in some embodiments, the system 100 includes a computer system 114 having one or more physical processors 116 programmed with computer program instructions that, when executed, cause the computer system 114 to obtain information or data from the sensor 112. In some embodiments, the computer system 114 may also be referred to as a means 114 for executing machine-readable instructions utilizing at least one processor 116.

[0099] In some embodiments, the system 100 is configured to reduce oxygen waste using an oxygen mixing module (OBM). The present patent application includes an algorithm that drives the oxygen mixing module valve to allow delivery of gas so that gas enters the ventilator only when the gas is to be delivered to the patient during the inspiratory phase of the patient's P breathing cycle.

[0100] To supplement the oxygen concentration in a pressure support ventilator, some devices offer a supplemental oxygen mixing module that allows high pressure gas to be fed directly into the ventilator from a wall or bottled gas source. The function of the oxygen mixing module is to use an onboard servo valve and flow meter in conjunction with the control and measurement of the ventilator system to titrate the oxygen flow leaving the ventilator so that it always has a user specified FiO2 of some value between 21% pure air to 100% pure oxygen within a control error range. Figure 3 A rear view of the ventilator 104 with an oxygen mixing module having an oxygen inlet 124 is shown.

[0101] Such ventilators typically use a passive patient circuit, in which a small hole is placed in the circuit near the patient, allowing gases from the circuit to leave the room directly. The purpose of this hole is to remove exhaled gases containing CO2 from the circuit. For users of supplemental oxygen, this hole will vent most of the oxygen not consumed by the patient during each breath directly to the atmosphere.

[0102] The present patent application uses an onboard servo valve in the oxygen mixing module controlled by an algorithm to cut off or greatly reduce the oxygen flow during the patient's exhalation phase. In this way, oxygen waste can be greatly limited. For passive flow circuit applications, oxygen savings can reach around 50% and for active circuits, oxygen savings can reach up to 100%. It should also be noted that most patient circuits in use are of the passive type (>80%) and switching to an active circuit to increase oxygen savings is clinically undesirable and is avoided at all costs. Therefore, the real problem of oxygen waste in ventilators lies with passive patient circuits.

[0103] When operating such an algorithm on a ventilator with an oxygen mixing module, it is important to also consider the effect of intermittently cutting off the oxygen flow on the ventilator alarms and the servo control system of the valve. It turns out that on the ventilator, the controller 114 on the oxygen mixing module is fast enough to change the oxygen output set point of the ventilator more than once per breath, without significantly affecting the FiO2 of the released gas when the supplemental oxygen is released. This patent application is conceived in response to clinicians' complaints about excessive oxygen waste when using ventilators. When bottled gas is input to the oxygen mixing module of a pressure support ventilator, this patent application reduces or eliminates oxygen waste, especially when used with a passive patient circuit. This patent application includes an algorithm that controls the opening and closing of the oxygen mixing module valve (i.e., servo valve) so as to fully and predictively limit oxygen use only during the inspiratory phase of the patient P. The algorithm also takes into account the servo control system of the oxygen mixing module valve and any effect on the alarm.

[0104] The present patent application is a software algorithm that is added to the ventilator to allow control of the oxygen mixing module valve (i.e., servo valve) to verify normal operation, thereby still providing a controlled FiO2 when delivering oxygen. Because the oxygen mixing module is an optional accessory in the ventilator, the software must be available when the oxygen mixing module is present in the ventilator 104.

[0105] The present patent application includes algorithms that function in conjunction with an oxygen mixing module present on ventilator 104. The device can be used with any ventilator having an oxygen mixing module.

[0106] In some embodiments, the system 100 includes a series of off-the-shelf parts or components including a series of connectors, a solenoid valve 108 with ultra-soft fine strands that connect to the ventilator 104, and a length of high-pressure tubing 110. In some embodiments, software is also added to the ventilator 104 to allow control of the valve 108.

[0107] In some embodiments, system 100 includes any ventilator having a low flow oxygen inlet and having a unit that powers an associated solenoid valve 108 using onboard software.

[0108] The system of the present patent application using bottled oxygen / gas as the oxygen source was conceived in response to the fact that inspiratory-only oxygen delivery from an oxygen mixing module (OBM) has little application for home ventilation. This is because home ventilator patients use concentrators and sometimes bottled oxygen / gas (which use low flow ports) instead of oxygen mixing modules. The main problem with using cylinders into low flow ports 124 is the rapid deflation of the cylinders, which is expensive.

[0109] In some embodiments, the system 100 is configured to reduce oxygen waste from the bottled gas or gas cylinder 102 supplying the ventilator low flow gas mixing port 124. That is, the system 100 is configured to reduce or eliminate oxygen waste when the bottled gas 10 is input into the low flow port 124 of the pressure support ventilator 104.

[0110] In one configuration, the low flow port 124 of the ventilator 104 is supplied by a high pressure gas cylinder 102. The problem is that most ventilator circuits are passive, meaning that there is a constant leak in the exhalation valve EV, resulting in only a small portion of the oxygen actually delivered by the ventilator 104 being inhaled by the patient P. Most of the gas leaves the exhalation valve EV. Waste of bottled oxygen 102 is a problem due to the cost of filling and operating the cylinders. Therefore, it is undesirable to use bottled oxygen with a low flow port.

[0111] To at least partially address this problem, the present patent application proposes placing a valve 108 / solenoid at the low flow port 124. In some embodiments, the valve 108 can be signaled and powered through an electrical port / connection on the ventilator 104, or the valve 108 can be signaled only by the ventilator 104 when receiving power from some other source.

[0112] The system 100 for use with the bottled gas 102 includes a solenoid valve 108 and a length of high pressure hose / accumulator 110, which is ideally controlled by the ventilator 104 and located at the entrance of the low flow port 124, and the high pressure hose / accumulator 110 provides a conduit connecting the gas bottle 102 to the valve 108. Other associated connectors at either end of this arrangement are also necessary. The ventilator 104 is also configured as a unit capable of processing the software associated with opening and closing the valve 108 and providing power to the active solenoid valve 108.

[0113] In some embodiments, the system 100 includes a valve 108 that operates in concert with the patient's breathing phase via the ventilator 104. In some embodiments, the valve 108 is used to shut off the flow of oxygen to the ventilator 104. In some embodiments, an algorithm is used in the ventilator 104 to actuate the valve 108, thereby allowing gas delivery, such that gas enters the ventilator 104 only when gas is to be delivered to the patient during the inspiratory phase.

[0114] In some embodiments, the accumulator 110 / high pressure hose is connected between the valve 108 and the oxygen source 102 / cylinder. The valve 108 is then opened and closed using an algorithm on the ventilator 104 that ideally delivers oxygen only during the inspiratory phase of the patient P, who is a certain distance (e.g., typically at least 6 feet) from the ventilator 104 and its accompanying oxygen supply. In this way, the valve 108 is used to restrict the flow of oxygen into the patient circuit 106 so that supplemental oxygen flows into the patient P only during inspiration and by default only during the inspiratory phase from the expiratory valve EV, thereby preventing waste of oxygen generated from the expiratory valve EV during the expiratory phase.

[0115] Because bottled gas is typically regulated to 50 psi, it is desirable to limit the size of the connecting tube volume as much as is practicable so that the connecting tube is not significantly inflated when valve 108 is closed. In this way, the volume of the 50 psi inflation that will fill tube 110 when valve 108 is closed will be limited, allowing the gas flow setting on the float flow meter to be more accurate. However, the setting of the float flow meter can also be titrated down to account for the line inflation in order to limit oxygen waste while still providing the same effective FiO2, but delivering oxygen from the gas cylinder 102 at a lower indicated gas flow rate.

[0116] When using a passive flow circuit, the oxygen savings can be as high as 50%, which is certainly significant. For an active circuit, the oxygen savings can be as high as 100% (the only oxygen delivered goes to the patient during inspiration).

[0117] In some embodiments, the system 100 includes a series of off-the-shelf parts or components including a series of connectors, a solenoid valve 108 with ultra-soft fine strands that connect to the ventilator 104, and a length of high-pressure tubing 110. In some embodiments, for example, software is also added to the ventilator 104 to allow control of the valve 108. In some embodiments, the system 100 includes any ventilator that has a low-flow oxygen inlet (e.g., 124) and has a unit that uses on-board software to power the associated solenoid valve 108.

[0118] In the following analysis, a model was developed and used that describes the logic elements associated with when supplemental oxygen is required and when it is not required in airflow to the lungs. Figure 8 A simple ventilator, expiratory valve, and lung model are presented. Figure 8 The anatomical dead space volume is shown. In this model, the following assumptions are made: 1) supplemental oxygen can be accurately added (or interrupted) to the airflow from the ventilator; 2) the exhaust valve has some known leak; 3) the lung has a certain volume V T , and includes 1 / 3 of the anatomical dead space at the connection to the patient circuit; and 4) for simplicity, there is no volume between the ventilator and the lungs. This allows one to think of a system where gas enters and leaves the lungs, where oxygen can be turned on and off precisely as needed at the mouth, without having to consider the volume between the ventilator and the lungs.

[0119] In considering this model, the state of gases in the lungs and circuit during various respiratory phases is reviewed. Fig. 9 Insertion of fresh gas from a ventilator into the lungs during an inspiratory phase is shown and assists in this analysis. Fig. 9 The color depth in the diagram simply indicates the position of each third air mass relative to its starting position in the first row. The first row illustrates the state of the lungs at the end of exhalation. The three blocks on the left are the three 1 / 3V T The ventilated air masses will enter the right lung, which is also divided into three volumes. Each row after the three blocks on the left indicates a third of the ventilator gas moving into the lung. Note that the gas already in the lung does not leave, it just indicates that the gas already in the lung is replaced by fresh gas.

[0120] Fig. 9It shows exactly where the volume delivered by each breathing cycle is delivered during the inspiratory phase. This allows one to clearly understand what portion of the delivered gas requires full oxygen replenishment.

[0121] Next we review in detail the types of gases and their locations during each breathing phase. This analysis requires considering the movement of gases as a mass throughout the system. This means that the mixing of gases along the airflow path is not considered and that gas concentrations are maintained as they move along the ventilation path.

[0122] Before inspiration begins, the anatomical dead space is filled with gas containing the worst quality of inspired air (that is, with the highest oxygen consumption and highest CO2 content), e.g. Fig. 9 This means that the first phase of inspiration (inhalation of poor quality air) is the inhalation of a volume of gas with the worst inspiratory quality and equal to the anatomical dead space. Therefore, it is the gas from the ventilator (that is, the gas just outside this anatomical dead space) that is important. Fig. 9 "Vent1" in the example contains the required oxygen content.

[0123] The anatomical dead space is eventually filled with fresh respiratory gas, which not only does not participate in gas exchange, but is also exhaled and removed from the ventilation circuit. Therefore, this volume is the main source of oxygen waste, since it does not participate in ventilating the patient, but is directly discharged to the atmosphere.

[0124] Only the first 2 / 3 of each tidal volume inspired actually helps gas exchange by providing fresh gas. The first 1 / 3 of the gas inspired into the lungs is poor quality gas left over from the previous expiratory phase residing in the anatomical dead space, and then the first 2 / 3 of the inspired tidal volume becomes the last 2 / 3 of the tidal volume inspired into the lungs. Finally, V T The posterior 1 / 3 does not participate in gas exchange as it simply fills the anatomical dead space.

[0125] During exhalation, unless rebreathed, all tidal volume is exhaled through the exhalation valve. During exhalation, if the flow of exhaled gas exceeds the exhaust capacity of the leaking valve, the gas will be pushed back through the ventilator until the leaking valve flow once again exceeds the patient's exhalation flow. Therefore, any supplemental oxygen entering the patient circuit at this time will be exhausted backward through the ventilator and will therefore be wasted. Finally, with respect to the exhalation valve, no matter what type it is, any oxygen-containing gas that leaves the valve is wasted.

[0126] In view of these considerations, the algorithm of the present patent application has the following goals: 1) do not infuse oxygen during the period of retrograde reflow in the patient circuit; 2) do not infuse oxygen during the period of V representing anatomical dead space; T3) not adding oxygen during the exhalation phase; 4) minimizing the amount of oxygen that simply leaves the exhaust valve; and 5) ensuring that there is adequate oxygenated gas at the beginning of inspiration.

[0127] In this patent application, the algorithm (reference Fig. 9 ), if a] a passive expiratory patient circuit is used and b] anatomical dead space is not enhanced by the delivered gas (representing the last 1 / 3 of the breath), then the theoretical gas usage is 2 / 9 or 22% of the gas usage used when the algorithm is not used (e.g., see Equation 4). Moreover, in the description of the algorithm in this patent application, the model shows a savings of 30-70%, assuming an average of 50%. These two situations do not appear to be contradictory because the latter model does not assume that gas will not be delivered into the anatomical dead space like the first model. The reason is that the latter model is derived with humidity delivery in mind, in which case the dead space will be absolutely humidified. In the former model, the goal is to supplement oxygen, so delivering gas to the anatomical dead space is a waste and an opportunity for savings. The distinction between the two models is provided here to reconcile the differences between the two models.

[0128] Fig.10 Used to develop the mathematical schemes associated with the algorithms of this patent application. Fig.10 Volume and flow traces for one breathing cycle are shown. Fig.10 The dot in the middle indicates V T 2 / 3 position.

[0129] From the information given above, it is clear that supplemental oxygen must be at full flow at the start of inspiration and must continue until at least 2 / 3 of the tidal volume has been inhaled. The only oxygen wasted will be the oxygen that leaves the exhaust valve during this period. This can be written in the form of the following equation (1): O2 open minimum time: Among them, V T = tidal volume; and

[0130] Q L = flow from the exhalation valve; and

[0131] T = 2 / 3V delivered T time period; and

[0132] t0 = breathing start time

[0133] Obviously, supplemental oxygen should be turned off for the remainder of the breathing cycle, which can be written as follows in the form of equation (2):

[0134] O2 off time:

[0135] Among them, V T = tidal volume; and

[0136] t2 = breathing end time.

[0137] An estimate of the maximum theoretical oxygen savings will be determined when the oxygen flow is constant. The analysis is simplified by assuming that the leak flow is constant throughout the breathing cycle. If an oxygen concentrator is used, the oxygen flow is constant during operation of the ventilator. This effectively maintains a constant. This makes it easy to calculate the oxygen savings. For normal operation, the volume of oxygen used per breath is calculated as shown in equation (3a) below.

[0138]

[0139] in,

[0140]

[0141] (t2-t0) = breathing period measured as the difference between the breathing end time and the breathing start time; and

[0142] (T I +T E ) = breathing period measured as the sum of inspiration time and expiration time.

[0143] Using the algorithm as defined in (1) and (2), the volume of oxygen used per breath is given by equation (3b):

[0144]

[0145] in,

[0146] If it is assumed that the inhalation phase can be approximated as a square wave (constant flow), the oxygen flow period (T-t0) represents exactly 2 / 3 of the inhalation phase. Furthermore, for an I:E (i.e., inhalation: exhalation ratio) of 1:2, the oxygen on time is 2 / 3 of 1 / 3 of the total breathing period. This means that the oxygen volume can be expressed using the following equation (4).

[0147]

[0148] in,

[0149] This is indeed a huge potential for saving oxygen.

[0150] When a passive flow circuit is used, the overall goal of the algorithm is to minimize the supplemental oxygen that leaves the expiratory valve EV. To assess the amount of gas that leaves the expiratory valve EV during operation, the flow versus pressure curve of the expiratory valve EV is used. Fig.11 A graphical representation of the flow versus pressure curve for the exhalation valve EV is shown. The pressure data is shown on the left Y-axis, while the flow data is shown on the Fig.11 The pressure data is measured in centimeters of water column (cmH20). The volume data is measured in liters per minute (L / min).

[0151] The forward and reverse flow curve fits were averaged to obtain equation (5) below.

[0152] ΔP=0.008Q 2 +0.148Q-0.290 Equation (5)

[0153] Where Q = EV flow; and

[0154] P=EV pressure

[0155] Using the quadratic formula, equation (5) is inverted so that the flow rate as a function of pressure can be calculated. This results in the following equation (6).

[0156]

[0157] A series of flows is calculated to account for the flow from the expiratory valve EV and is presented in Fig.12 in the table shown. Fig.12 The table in shows the relationship between the flow rate of the exhalation valve EV and the circuit pressure. Fig.12 As can be seen in the table, the volume leaking from the valve during a 2 second period at a given pressure is very large. Furthermore, it should be noted that even with the best algorithms, it is not possible to cut off the exhaust flow EV during the inspiration phase, during which the gas must be oxygenated. Taking this into account and observing Fig.12 , this algorithm still results in significant oxygen losses.

[0158] Difficulties associated with attempting to reduce oxygen using a passive flow circuit are further noted. Remember that in order to turn oxygen on and off as indicated by equations (1) and (2) above, the major obstacle is that the trigger time and cycle time must be predicted because the gas concentration at patient P must be correct, but patient P is being administered gas at ventilator 104 with a 700 mL patient circuit in between. Other issues include: 1) What is the algorithmic basis for turning oxygen flow on and off with a patient circuit in between? 2) How to address the issue of exhaled gas returning to the patient circuit at the beginning of exhalation? 3) How does mask leak affect oxygen delivery? 4) How to address the issue of variable respiratory volumes? 5) How to address the issue of variable respiratory rates? 6) What is the actual effect of diffusion mixing at the air mass interface? 7) How does tube curvature / orientation affect mixing as the gas travels in the circuit? 8) What are the limitations of such an algorithm when tidal volumes are reduced to pediatric levels? In view of all of these difficulties, other options were considered before attempting to develop an algorithm for a passive flow circuit.

[0159] The first option considered was an active flow circuit. On the surface, the opportunity to improve the oxygen waste problem is much greater because there is no exhaust flow during inspiration. In addition, during exhalation, there is a blowdown phase in which the active exhalation valve (AEV) opens widely, causing the patient to exhale strongly, but also generating flow loss from the ventilator. The amount of volume lost from the ventilator during the blowdown phase is actually unknown, but it can vary widely and can be very large.

[0160] The expiration phase is followed by a continuous "bias" flow from the ventilator that leaves the active exhalation valve for the remainder of the exhalation phase. The bias flow is targeted to be around 10 L / min, which results in a volume loss of only 0.33 L for a 2-second flow, significantly less than in Fig.12 The values ​​are given in the table in .

[0161] use Figures 13a-13c The exhaust phase and bias flow phase are reviewed in more detail. The exhaust behavior and bias flow behavior were examined using three ventilators on multiple different active exhalation valve options. Similar behavior for exhaust flow and bias flow was observed using all three ventilators on multiple different active exhalation valve options. Figure 13b-13c It is shown that they have substantially no excess exhaust flow during the discharge phase, and the flow magnitude changes from the flow level at the end of inspiration (eg, close to 0) to the bias flow level. Fig.13a It is shown having a burst of ventilator airflow that leaves the active exhalation valve during the exhaust phase.

[0162] The key advantage of the active flow circuit is that the exhaust flow is zero during the inspiration phase, which results in no oxygen waste. Figure 13a-13b It can be seen that the ventilator can control the exhaust flow to minimize the flow or frankly the exhaust flow and its accompanying oxygen. Moreover, since the size of the bias flow is controlled, it should be possible to limit this flow in the algorithm to even exceed 10L / min. In summary, the algorithm using an active flow circuit has the following benefits: a) no oxygen loss during the inspiration phase, which is an existing benefit of the active circuit (no additional algorithm is required), b) the (oxygen) flow that is exhausted during the exhaust phase can be reduced or eliminated, c) the bias flow can be adjusted as low as possible; and d) the benefits of the algorithm for the active flow circuit are the same for active PAP or active flow.

[0163] There is another possible approach to improve the oxygen waste during blowdown and bias flow, which is to develop an algorithm that cuts off oxygen to welcome the exhalation phase. This is similar in principle to what was considered above for the passive valve, and it has many of the same issues, but such an approach would allow blowdown control and bias flow to remain intact. Such an approach would allow us to address the problem of not filling the last third of the tidal volume with oxygen in the anatomical dead space.

[0164] In the following sections of this patent application, an initial time-based algorithm as well as a volume-based algorithm and solved special cases are presented.

[0165] This problem is quite complex as it involves compensating for the volume of patient circuit tubing residing between the patient and the humidifier. This requires predicting in advance the time required to enable the humidifier so that moist air is present at the patient's airway at the start of inhalation. Obviously, this is impossible to predict precisely as the turn-on time of the humidification process must actually be predicted, but some assumptions can be used to facilitate this prediction, and the algorithm can always fall back to continuous delivery of humidification as the default setting. These assumptions are outlined below.

[0166] Fig.14 The flow circuit model used as the basis for the algorithm is depicted. Many approaches centered around calculating the volume associated with different flows in the patient circuit were attempted. Calculating the volume is simple in itself, but becomes complicated in the presence of a constant leak flow out of the system. The reason is that the volume is the continuous integral of the flow signal summed over time. However, in the case of a constant leak, the integral always tends to infinity, thus requiring the selection of a time or condition to reset the integral.

[0167] In addition to the difficulties associated with calculating the volume, there are some additional complexities associated with other aspects of the system model that require attention. These complexities initially led us to consider implementing only Fig.14The simplest version of the model described in . Here is a list of these situations: 1) the patient's breathing profile is sinusoidal; 2) the peak expiratory flow magnitude does not exceed the leak flow (no retrograde flow in the patient circuit); 3) constant respiratory rate and minute volume; 4) constant leak flow - the patient is on CPAP.

[0168] As the model evolved, more complex operations were included in the model. Complex operations of the model include 1) the amount of patient exhaled flow exceeding the leak flow, 2) the use of bi-level pressure and its effect on leaks and more complex breathing patterns, 3) patient breathing patterns based on rise and fall times of first order filtering with appropriate I:E, and 4) how to cope with changing respiratory rate and tidal volume.

[0169] After evaluating various volumetric methods, a method based almost entirely on timing was devised. This method requires a single finite integral of the flow rate to evaluate the relationship between the flow rate and the pipe volume V. tube Prior to describing the details of the algorithm, important aspects of this model related to volume calculations are first addressed. Fig.14 The expression for the flow rate shown in FIG is as shown in the following equation (7).

[0170] Q C (t) = Q L (t)+Q P (t) Equation (7)

[0171] Among them, Q C = total circuit flow;

[0172] Q L = leakage flow; and

[0173] Q P = Patient flow

[0174] If the patient flow rate (Q P ) is a sinusoidal curve and the leakage flow (Q L ) is constant, the total circuit flow (Q C )The signal looks like Fig.15 As shown in . Fig.15 A graphical representation of the flow signal corresponding to equation (7) is shown. The flow data is shown on the Y-axis on the left, while time is shown on the Fig.15 The time is measured in seconds. The flow rate data is measured in liters per minute (L / min).

[0175] exist Fig.15 It can be seen that the loop flow signal Q is not equal to one or more complete cycles. CThe integration of a segment of gives different values ​​depending on where the integration starts. The important observation here is that the starting point for integrating the total flow signal to obtain the volume is critical to obtaining an accurate volume calculation result.

[0176] The goal of a perfect algorithm is to turn on the humidification function so that humidified gas appears at the patient when the patient begins to inhale, and then terminate at the end of the inhalation phase. The main difficulty is that the patient circuit volume resides between the patient and the humidification source. How to predict when to turn on the humidification function before the patient begins to breathe has to be determined. To achieve this, three key assumptions are made: 1) the breathing pattern and breathing cycle period remain fairly stable over time; 2) the humidified gas must travel through the patient circuit so that the boundary between the humidified gas portion and the dry gas portion remains essentially separated as they travel along the tube; 3) the patient circuit volume is known a priori.

[0177] With these 3 assumptions, it is possible to integrate the patient circuit flow until the volume of the patient circuit is reached. At this point, it is known how long it takes for that volume to pass through the circuit. This can be used to delay the initiation of humidification until the patient's next inspiration. Of course, it is important not only to integrate the flow, but also to know exactly when to start the integration. To address this latter point, the Fig.16 . Fig.16 A timing diagram illustrating an on-demand delivery timing method is shown. Fig.16 The top colored band in indicates the span over which the circuit flow is integrated over the patient circuit tubing volume. Fig.16 The bottom colored bars in each show the duration of a complete breathing cycle.

[0178] exist Fig.16 The span is defined as The integration for identifying the duration of flow through the patient circuit is started so that the time period is exactly at the beginning of inspiration t trig-1 Although it is not actually known a priori how long this duration is, if a history of flow values ​​is kept for some time, it is possible to calculate how long the last period lasted and then use t trig-1 Integrate backward until V tube Until this time. Then used to predict when to start the humidifier for t trig-2 or trig-3 The next on-demand cycle depends on Duration (if When the duration T2 of the next breathing cycle is exceeded, it may be necessary to start a demand cycle T3) for the next breathing cycle.

[0179] It is assumed that historical values ​​of the circuit flow at each time step have been stored and these flow values ​​are technically counted back in time.The expression for calculating the duration of the flow surrounding the pipe volume is shown in equation (8) below.

[0180]

[0181] Among them, V sum = tube volume;

[0182] is the flow value stored at count i;

[0183] i=0 is the same as in t trig Counts associated with traffic at

[0184] k is the sum of t trig Counts backward until V sum ≥V tube until.

[0185] When the summation in equation (8) is complete, the value of count k corresponds to the delay required to begin delivering moisture for that breath so that once the necessary volume has passed through the tube it reaches the patient in the next breath or breaths.

[0186] About loop volume delay Another point to note is that it would be incorrect to swap the values ​​of time and count. However, since the counts are derived from the constant clock frequency used in the ventilator, each count spans substantially the same duration, thus allowing them to be interchanged.

[0187] The delay associated with the patient circuit tubing is now known. Humidified gas can then be delivered during the inspiratory phase. However, the volume delivery flow pattern into the patient circuit for loading the inspired volume will not correspond to the actual volume delivered during the inspiratory phase unless the patient begins to inhale at the same time as the tubing begins to load with humidified gas from the humidifier. As a result, tubing loading cannot simply be turned on for the same duration as the inspiration time. Therefore, the circuit flow volume delivered during the inspiratory phase is measured in order to deliver a specific volume into the tubing. To measure this volume, equation (9) is used.

[0188]

[0189] Among them, V insp = flow volume delivered during the inspiratory phase;

[0190]

[0191] i=0=with t trigCounts associated with traffic at

[0192] n = in the next t cycle The count at .

[0193] The delivery equation is then written as the following equation (10):

[0194]

[0195] Among them, V sum2 =Instantaneous value of integrated flow;

[0196]

[0197] i=0=with t trig Counts associated with traffic at

[0198] m=at V sum2 ≥V insp The count at .

[0199] Equations (9) and (10) appear to be identical, but Equation (9) is only used to calculate the volume of gas consumed by the patient (V insp ), and equation (10) is used to set trig The delivery of the gas volume into the tube begins at k steps before the next value of V (i.e., where k is obtained according to equation (8)). sum2 ≥V insp completed when ).

[0200] Invariably, there will be some variability in the timing of k and the calculation of the inspired gas volume on a breath-to-breath basis. If the above algorithm is implemented as described, the system may end up chasing small, insignificant perturbations in these parameters. To avoid this, the value of k and V should be kept constant. insp A low pass filter is applied. The parameters of these filters are empirically calculated by those skilled in the art. In some embodiments, other averaging / smoothing processes may be applied as will be appreciated by those skilled in the art.

[0201] One key assumption required for the algorithm to work is that the humidified gas moves as a bolus down the patient circuit. It has been found empirically that bolus flow is actually a good assumption and can be used as an assumption in the applications presented here.

[0202] In summary, when implementing equation (11), Start turning on the water, but don't wait until k shift The delivery of the tidal volume described in equation (10) begins to be counted only when

[0203] Because the method for figuring out when to preload the patient circuit tubing is not volume based, but only time related, it does not matter what shape the patient's inspiratory or expiratory pattern takes. It is also apparent that the algorithm still works even in the presence of bi-level pressure delivery, which changes the expiratory valve flow. The timing method is largely unaffected by this, except for the following effect: if the breathing cycle timing changes, the system is more likely to become inaccurate, because the cycle timing changes may translate into changes in the normal contribution of the leak, which may greatly affect the tube volume duration measurement.

[0204] Invariably, as mask leaks increase (or even changes in the patient's breathing rate or pattern), the circuit timing will become disrupted. A simple way to address this problem is to apply a minimum percentage error band beyond which the system will revert to full-time humidification until the error band can be restored. and the volume of the inhaled gas V insp Such a method is shown by the following equations (12) and (13).

[0205]

[0206]

[0207] Where η is the fractional difference beyond which the system will reset;

[0208] abs=absolute value;

[0209]

[0210] i = index of the current or past breathing cycle;

[0211] V inspi = inspired volume in breath i; and

[0212]

[0213] A second approach to the basic algorithm was conceived. This approach does not require timing and only uses the volume measurements already made, adding a volume measurement in addition to this. This approach also avoids the need to record and use historical data. Figure 17-22 The first is just a real recording of a set of patient flow and pressure signals, which can be used because of the robustness of the algorithm derived above and the fact that the new algorithm here avoids the need for a simple harmonic respiration signal as used before.

[0214] Fig.17Typical patient flow and pressure signals are shown. The top solid curve is the total circuit flow Q c , the dotted curve starting from the top is the leakage flow Q l , the second solid curve from the top is the actual patient flow Q p , the third solid curve from the top is the delivered pressure P p (corresponding to the right ordinate). Pressure data are shown in Fig.17 The flow rate data is shown on the right Y-axis of the graph. Fig.17 The pressure data is measured in centimeters of water column (cmH20). The flow data is measured in liters per minute (L / min). Time is shown in Fig.17 The x-axis of the graph is in seconds.

[0215] As mentioned above, it is necessary to calculate the total flow signal Q c Integrate to obtain the total suction flow V insp This is the value of Fig.18 The evaluation V insp The expression for is given in equation (9) above.

[0216] Fig.18 shows the V within the breathing cycle insp location and quantification. Fig.18 shows the total patient circuit flow signal Q c . The flow data is shown in Fig.18 The flow rate data is measured in liters per minute (L / min). Time is shown on the left Y-axis of the graph. Fig.18 The time is measured in seconds. By integrating the total inspired gas volume from the beginning to the end of the inspiratory phase, V insp yes Fig.18 The shaded area in .

[0217] The next step is to integrate the total flow to obtain the volume delivered during the entire breathing cycle. Currently, we ignore what happens when the expiratory flow exceeds the leak flow, thereby allowing retrograde flow in the patient circuit back to the ventilator. The total flow over the entire breathing cycle is Fig.19 Highlighted in yellow. Fig.19 The total respiratory volume V for one breathing cycle is shown tot location and quantification. Fig.19 shows the total patient circuit flow signal Q c . The flow data is shown in Fig.19The flow rate data is measured in liters per minute (L / min). Time is shown on the left Y-axis of the graph. Fig.19 The total volume V of a breathing phase is measured in seconds. tot yes Fig.19 The shaded area in .

[0218] The integral is shown in equation (14) below:

[0219]

[0220] Among them, V tot = total volume delivered by the exhaust port during a breath;

[0221] Q c = total flow rate of the patient circuit;

[0222] i=0=with t trig Counts associated with traffic at

[0223] N = count at the end of the loop, or corresponding to t trig Count.

[0224] From the total volume V tot Subtract V tube When this volume is reached from the beginning of the next breathing cycle or any subsequent breathing cycle, the turn_on time is reached, such as Fig. 20 shown. Fig. 20 shows the tube volume V tube With the total volume V tot The volume of the tube V tube is shown in Fig. 20 In some embodiments, V tube is input by the user. In some embodiments, V tube It is calculated by the ventilator. Fig. 20 shows the total patient circuit flow signal Q c . The flow data is shown in Fig. 20 The flow rate data is measured in liters per minute (L / min). Time is shown on the left Y-axis of the graph. Fig. 20 The x-axis of the graph is in seconds.

[0225] At first glance this may not be intuitive, so be aware that no matter what algorithm is used, historical information is always needed to predict when to turn on oxygen or water. In the previous algorithm, historical flow information was stored and this flow information was integrated backwards from the start of inspiration to find V tubeIn this case, instead of storing old flow values ​​and integrating them, the total volume essentially provides the only historical information needed, which eliminates the need to store more than one element of any type of historical data. In other words, V tot The value of is historical information.

[0226] Then just need to see that the tube volume is subtracted from the total volume. Set on_time because the algorithm requires that the volume be subtracted from t trig Go backward in time until the volume equals V tube However, by tot Subtract V tube , the same time point can be obtained precisely. Therefore, the delivery of oxygen or water starts at turn_on and then at V insp The delivery is then cut off, as described above. This is shown in Fig.21 middle.

[0227] Fig.21 The inspiratory gas volume V is shown starting at turn_on and ending at turn_off insp delivery. Fig.21 shows the total patient circuit flow signal Q c . The flow data is shown in Fig.21 The flow rate data is measured in liters per minute (L / min). Time is shown on the left Y-axis of the graph. Fig.21 The x-axis of the graph is in seconds.

[0228] In other cases, the algorithm described here needs to be slightly modified to make the necessary adaptations. These cases are described below, but it is important to point out for now that a margin is provided for the turn-on inspiration volume in order to provide maximum comfort and safety to the patient. Since the last part during the inspiration phase is delivered only to the anatomical dead space, no adjustment is made to the turn_off end.

[0229] Fig. 22 Adding margin to turn_on is shown. Fig. 22 shows the total patient circuit flow signal Q c . The flow data is shown in Fig. 22 The flow rate data is measured in liters per minute (L / min). Time is shown on the left Y-axis of the graph. Fig. 22 The x-axis of the graph is in seconds.

[0230] At this point it should be noted that in cases where the tidal volume is small and the respiratory rate is high (e.g., in neonates), V tot -Vtube This is problematic because negative values ​​will never create enough delay to compensate for the patient circuit tubing V tube .

[0231] To avoid this problem, it is necessary to ensure that this value exceeds 0. To do this, the total flow is integrated over several breaths until the difference V tot -V tube Until it becomes positive at the end of the breathing cycle. Although this is not required, it is recommended to start a new integration at each new breathing cycle, so that there may be many integrations running in parallel, all with the goal of reaching a positive value for the volume difference at the end of the breathing cycle. Therefore, calculate V tot The algorithm is shown in equation (15) below.

[0232]

[0233] Among them, V tot = total volume delivered by the exhaust port for a given breath;

[0234] Q c = total flow rate of the patient circuit;

[0235] i = time step starting at the beginning of the breathing cycle;

[0236] N = the number of time steps in one complete breath; and

[0237] m = number of complete breaths, and when V tot -V tube It reaches its value when >0.

[0238] The last thing to note here is that the tube volume V tube The value of includes various things depending on the loop configuration and the entity being controlled.

[0239] Humidification is a very simple case, since the only volume that needs to be compensated is the volume between the humidifier outlet and the patient. Assume that this is just the patient circuit tubing. Equation (16) shows that the tube volume is equal to the patient circuit tubing volume.

[0240] V tube =V circuit Equation (16)

[0241] Among them, V tube = tube volume; and

[0242] V circuit =Patient circuit tubing volume.

[0243] For oxygen mixing, the tube volume V tubeThe value of is a little more complicated because it includes a number of different things that may or may not be present in the circuit. These things include: a) Patient circuit tubing V circuit (that is, always present); b) Humidifier bowl V bowl (that is, optional, but possible); 3) Humidifier connection pipe V connect (That is, always have humidifier ~ 175cc); 4) Oxygen mixing module volume V OBM (that is, –XX cc is always present); and 5) the ventilator internal flow path volume V vent If all the components listed above are present, the tube volume V tube This is shown by the following equation (17).

[0244] V tube =V circuit +V bowl +V connect +V OBM +V vent Equation (17)

[0245] Among them, V bowl =humidifier bowl volume;

[0246] V OBM = oxygen mixing module volume;

[0247] V connect =Volume of humidifier connecting pipe;

[0248] V circuit = patient circuit tubing volume; and

[0249] V vent =Volume of the ventilator's internal flow path.

[0250] Another concern with the volume measured as described above is the quantification of the volume of air delivered into the compliance due to the compressibility of air. For the measured parameters, the volume is precisely known, so no compensation for this is required. However, the user must enter the pipe volume V tube is a constant value that is affected by compliance.

[0251] It is known that the patient circuit tubing and additional rigid tubing arrangements within the ventilator can be assumed to be non-flexible, but it is also known that compliance is not the case due to the compressibility of gases. The compliance of air in a certain volume is expressed as equation (18) below.

[0252]

[0253] Where C = compressible gas compliance,

[0254] V = volume of interest, in this case V tube ,and

[0255] P tot = absolute pressure in that volume, which is shown in equation (19) below.

[0256] P tot =P vent +P atm Equation (29)

[0257] Among them, P vent = metered ventilation pressure;

[0258] P tot = absolute pressure in the volume of interest, in this case V tube ;

[0259] P atm =Local atmospheric pressure.

[0260] If in P vent With a 0 to 20 cmH2O and a total pressure of 1000 cmH2O, for a 6 foot, 22 mm patient circuit, the volume is approximately 700 cc. Using these parameters in equation (17), the compressible gas compliance is 0.70 cc / cmH2O. Therefore, if you pressurize a circuit from 0 to 20 cmH2O, additional volume will accumulate due to the gas compression compliance of approximately 14 cc. This volume is only 2% of the total volume of the circuit.

[0261] However, a much worse scenario emerges if a larger tube volume and lower atmospheric pressure are considered. A larger tube volume is present when using a humidifier (1320cc [695+450+175]), and very low pressure is present at 10,000 feet (~700cmH2O). With these parameters, the compliance becomes 1.89cc / cmH2O. A 20cmH2O change in pressure then corresponds to a 38cc change in compliance volume, which is just under 3% of the total volume. If the pressure change was 40cmH2O instead of 20cmH2O, that percentage would double to over 5.5% of the total volume. Arguably, this last value is probably the worst case scenario for compliance. To make this clearer, take a sample value and put it into Fig.23 in the table shown. Fig.23 The table in shows a sample of pipe gas compressibility compliance results. The last column is the percentage of the compliance volume relative to the total volume.

[0262] We can further consider what would happen if the compression volume was not compensated. In the absolute worst case, the error is less than 6% of the total volume. This is not insignificant for a 22mm tube with a volume of 695cc, in which case the error is approximately 40cc. Therefore, it is recommended to compensate for compliance.

[0263] Perfectly optimized delivery of compliance compensation gas is quite complex because delivery of inspiratory gas volume into the circuit may occur when the circuit is at inspiratory pressure or expiratory pressure or both. Therefore, the compliance volume may change even when the inspiratory gas volume is being delivered. To avoid these complexities, it is a mistake to accommodate the patient by increasing the margin volume corresponding to the worst case for a given operating condition. The calculation of the margin volume is shown in equation (20) below.

[0264]

[0265] in, P atm = local atmospheric pressure;

[0266] C = compressible gas compliance; and

[0267] V margin = margin volume;

[0268] Then apply the margin volume V margin ,like Fig. 22 To implement this application, we first have to find out how far we want to move the value of turn_on. To do this, we simply calculate V tot -V tube When the margin volume V margin Add to V tube The volume calculation for turn_on is shown in the following equation (21).

[0269] V turn_on =V tot -(V tube +V margin ) Equation (21)

[0270] Among them, V turn_on = turn_on volume; and

[0271] V tot =Total respiratory volume.

[0272] Therefore, to deliver to cover the inspired gas volume V insp The volume of is shown in the following equation (22):

[0273] V turn_off =Vinsp +V m arg in Equation (22)

[0274] Among them, V turn_off = turn_off volume; and

[0275] V insp = inspired gas volume.

[0276] For a normal adult, the anatomical dead space encompasses approximately 150 cubic centimeters (cc), or slightly less than 1 / 3 of any breath in Cheyne-Stokes breathing. This means that the last third or so of gas provides no ventilatory benefit to the patient and is simply a space filler. With humidification, it is important to keep the dead space gas humidified to avoid drying out the upper airways.

[0277] However, for oxygen delivery, any gas in the anatomical dead space will be wasted. Therefore, the algorithm can include a method to not deliver gas into the anatomical dead space. To do this, the delivery of oxygen is only temporarily stopped for a small portion of the inspired volume. This is written as the following equation (23).

[0278] V turn_off =(1-β DS )(V insp +V m arg in ) Equation (23)

[0279] Among them, β DS = the fraction of the patient's tidal volume representing anatomical dead space.

[0280] Whenever the patient circuit flow is negative, it is necessary to continue to be cognizant of the following facts: for the next inhalation, the patient circuit must contain gas with the following properties: 1) it must be an uninterrupted slug residing in the patient circuit tubing; 2) the gas throughout the gas slug must be enriched to the same level; 3) the volume of the delivered gas slug must be equal to V insp ; 4) if ventilation is insufficient to dissipate excess CO2, the algorithm cannot consider rebreathing; and 5) as long as the leak is > 0, on average, the volume of negative flow V neg must be less than V insp .

[0281] The problem is that this slug of delivered enriched gas can start at any time, a fact that is only complicated by the fact that the exhaled flow exceeds the leak flow (i.e., retrograde flow). If there is retrograde flow, the correct response for how to deal with it depends on the type of situation that exists. In all of these cases, it is assumed that retrograde flow only occurs for a period of certain duration during the delivery of a single tidal volume. The situations considered include: 1) no retrograde flow; 2) enrichment starts after retrograde flow ceases; 3) enrichment starts, after which retrograde flow starts, but the retrograde flow volume does not exceed V UV , i.e., the volume upstream of the enrichment point; and 4) the beginning of enrichment, after which retrograde flow begins, and the retrograde flow exceeds V UV .

[0282] First consider the case with no retrograde flow. This is the same as the case with no retrograde flow. The enriched flow is simply delivered through volume V insp .

[0283] Next consider the case where enrichment begins after retrograde flow. That is, enrichment begins after retrograde flow ceases. This is the same as the case without retrograde flow. The enriched flow is simply delivered through volume V insp .

[0284] In the case of the onset of enrichment, retrograde flow begins after this, but the retrograde volume does not exceed V UV , that is, the next consideration is the volume upstream of the enrichment point (i.e., V neg ≤V UV ). In this case, the following rules apply: 1) Start volume delivery integration at an appropriate point; 2) Stop volume delivery integration as soon as the flow rate becomes negative and retain the integrator value; 3) Start integrating for negative flow rates V neg (t) Integrate; 4) Once the flow changes direction, store the negative flow volume V neg Once the negative flow integrator returns to 0, a) volume delivery integration is restarted from the point where it was previously stopped; and b) enriched delivery is restarted once again until V insp Finish.

[0285] In the case of initial enrichment, retrograde flow begins after this, and the next consideration is that retrograde flow exceeds V UV (V neg >V UV ).

[0286] In this case, the following rules apply: If V insp_start ≥V neg , then 1) start volume delivery at the appropriate point; 2) measure the inspThe volume of positive flow at the beginning until retrograde flow begins. This will be designated as V insp_start ; 3) When equal to (V insp_start -V neg ) has been delivered into the patient circuit, stop delivering enrichment and stop the volume delivery integration, but retain its value; 4) once the flow becomes negative, start the negative flow integrator; and 5) once the flow changes direction, restart enrichment and restart the volume delivery integrator. If V insp_start <V neg , then 1) gas delivery is not started until positive flow is restored; and 2) the above scenario without retrograde flow is then used.

[0287] In the following section of this patent application, a savings model for a passive flow circuit is presented. For a passive patient circuit, the savings for a passive flow circuit are expected to be approximately 50%, while for an active flow circuit, the savings may be 100%.

[0288] As part of the development of true on-demand humidification delivery, it is important to be able to predict the water savings in such a design. The analysis is outlined below and also provides a prediction of the amount of water that could be saved in perfect on-demand delivery.

[0289] The water savings prediction is based on a simple model that describes the water that is added to the gas as it travels through the humidifier and then down the patient circuit. The model is based on the idea that the flow from the expiratory valve EV is only a function of the circuit pressure and is represented by an inspiratory model and an expiratory model, as Fig.24 shown.

[0290] exist Fig.24 The left figure shows the gas volume movement during the inspiration phase, while the ( Fig.24 The right figure in the figure shows the gas volume movement during the exhalation phase.

[0291] refer to Fig.24 The inspiratory phase model and the expiratory phase model shown in FIG. Fig.24 Summing the connection points in any model in , we obtain the following equations (24) and (25).

[0292] According to equation (24), the volume V passing through the humidifier during the inhalation phase is insp Equal to tidal volume V t The total volume leaving the expiratory valve during the inspiration phase sum.

[0293] According to equation (25), the volume V passing through the humidifier during the exhalation phase is exp Equal to the total volume leaving the exhalation valve during the exhalation phase With tidal volume V t difference.

[0294]

[0295]

[0296] Among them, V insp = volume passing through the humidifier during the inspiration phase;

[0297] V exp = volume passing through the humidifier during the exhalation phase;

[0298]

[0299] V t = tidal volume; and

[0300]

[0301] Here we point out several important assumptions in this analysis (ref. Fig.24 and equations (24) and (25) above). For a given circuit pressure, there will be a specific expiratory flow regardless of what the patient is doing. In this approach, pressure fluctuations are ignored and these pressures are assumed to be constant during both the inspiratory and expiratory phases, but these pressures are not necessarily the same (continuous positive airway pressure (CPAP) vs. bi-level positive airway pressure (BiPAP)).

[0302] Another key assumption in this analysis is that the timing and consistency of pressure are the same during both the inspiration and expiration phases, allowing for effective implementation of Fig.24 Volume matching is inherent in the model.

[0303] Finally, it is assumed that because the volumes passing through the humidifier are being compared, any volume passing through the humidifier will receive the same proportion of water, allowing the water savings to be estimated using volume alone. Since residence time is reduced, it is likely that the greater the gas flow through the humidifier, the less water will be picked up. Therefore, it is difficult to assess the effect in all cases, so the water content is assumed to be proportional to volume. By using this model, the water savings can be written as a percentage using the above model by relating the ratio of the amount of water per breath if no water is delivered during the exhalation phase to the amount of water per breath if water is delivered during the entire breath.

[0304] The water savings are then calculated by assuming perfect operation of the on-demand algorithm, so that water is delivered only during the inspiratory phase and not during the expiratory phase. The water savings is equal to the ratio of the expiratory water loss to the total water loss in normal operation, which can be written as the following equation (26). The volume V that passes through the humidifier during the inspiratory phase insp The volume V that passes through the humidifier during the exhalation phase exp The sum is equal to the total water loss in normal operation (ie, the denominator in equation (26) below).

[0305]

[0306] Among them, V insp = the volume passing through the humidifier during the inspiratory phase; and

[0307] V exp = volume passing through the humidifier during the exhalation phase.

[0308] With respect to leak valve flow rates, exhaust valves are used to predict flow rates as a function of pressure. Fig.25 A graph and curve fit of this relationship are presented in . That is, Fig.25 The relationship between pressure and flow rate and the curve fitting function are shown. The pressure data is shown in Fig.25 The pressure data is measured in centimeters of water column (cmH20). The flow data is shown in Fig.25 The flow / volume data is measured in liters per minute (L / min).

[0309] Fig.25 This curve in follows the shape of a second-order polynomial, so this is the choice Fig.25 The reason for the curve fit is given in . Furthermore, since the original data set has no values ​​below about 12 L / min, the curve fit is forced to pass through 0, so that the calculated flow rate is constrained by this requirement.

[0310] The purpose of using this curve fit in this analysis is to allow one to calculate the unknown leakage flow using the known pressure. However, since the curve fit is second order, a quadratic formula is used to calculate the flow, since the general expression for a second order polynomial has 2 roots in the independent variable "flow". This is shown below in equation (27). In equation (27), the offset pressure P offset Measured in cmH2O; laminar flow resistance R L It is measured in cmH2O / L / min; and the turbulent resistance R T In cmH2O / L 2 / min 2 Measured in units.

[0311] ΔP=R T Q 2 +R L Q+P offset Equation (27)

[0312] Among them, R T = turbulent drag;

[0313] ΔP = pressure change;

[0314] Q = flow rate;

[0315] R L = laminar flow resistance; and

[0316] P offset =Offset pressure.

[0317] To solve for the flow rate Q, all terms on the right side of equation (27) are isolated to obtain the following equation (28). Each term in equation (28) is described above in equation (27).

[0318] 0=R T Q 2 +R L Q+(P offset -ΔP) Equation (28)

[0319] The quadratic formula begins with a polynomial, the form of which is shown in equation (29). In equation (29), Q is the flow rate, and a, b, c are coefficients.

[0320] 0=aQ 2 +bQ+c Equation (29)

[0321] In this model, the curve fit is forced through 0, so the term P offset Has a value of 0. By using Fig.25 By fitting the curve in and combining the coefficients in equations (28) and (29), the coefficients can be in the form shown in equations (30)-(32) below. Each term in equations (30)-(32) is described in equations (27) and (29) above.

[0322] a=R T =7.10875x10 -3 Equation (30)

[0323] b=R L =6.42039x10 -2 Equation (31)

[0324] c=-ΔP Equation (32)

[0325] The values ​​provided in equations (30) and (31) were measured for the exhalation port of one of our sleep masks. The quadratic formula can then be written as equation (33) below.

[0326]

[0327] It is also noted empirically that the significant terms of the solution for flow are the positive terms in the numerator, so equation (33) can be rewritten as equation (34) as shown below. Each term in equations (33)-(34) is described in equations (27) and (29) above.

[0328]

[0329] Variables that affect the water saving percentage include the following: a) I:E (inspiratory: expiratory ratio); b) respiratory rate; c) tidal volume; d) continuous positive airway pressure (CPAP) level; e) bi-level positive airway pressure (BiPAP) combination; and / or f) additional leaks, such as mask leaks, which will be modeled as a constant flow rate. After the model is built, a series of cases are run in which each of the variables listed above is varied within a reasonable range and the impact of each variable on the water saving percentage is calculated.

[0330] Figure 26-32 are plots that look at the model for each of these variables discussed above. In each figure, a list of values ​​associated with all other variables is provided on each plot. Note again that the percentage of water savings is the amount of water not required when using the perfect on-demand algorithm compared to operating with continuous water addition under the same parameters. Also, the span of the ordinate is the same for all plots, and the red markers indicate points associated with the baseline condition.

[0331] Figure 26-32 A graphical representation of the percentage of water saved on demand when varying different parameters is shown. The percentage of water saved is shown in Figure 26-32 The water saving percentage data is measured in percent.

[0332] Fig.26 The percentage of water saved when the CPAP pressure is varied is shown. The CPAP pressure is shown in Fig.26 Continuous positive airway pressure (CPAP) pressure is measured in centimeters of water (cmH20).

[0333] Fig. 27The percentage of water saved when the IPAP pressure is varied is shown. The IPAP pressure is shown in Fig. 27 The inspiratory positive airway pressure (IPAP) pressure is measured in centimeters of water column (cmH20).

[0334] Fig.28 The percentage of water saved when the CPAP pressure is varied is shown. The CPAP pressure is shown in Fig.28 CPAP pressure is measured in centimeters of water column (cmH20).

[0335] Fig.29 The percentage of water saved when the tidal volume is varied is shown. The tidal volume is shown in Fig.29 The tidal volume is measured in milliliters (ml).

[0336] Fig.30 The percentage of water saved when the breathing rate is changed is shown. The breathing rate is shown in Fig.30 The respiratory rate is measured in units of respiratory rate per minute (brpm).

[0337] Fig.31 The percentage of water saved when the I:E (inspiratory: expiratory ratio) is varied is shown. The I:E (inspiratory: expiratory ratio) is shown in Fig.31 on the x-axis of the graph.

[0338] Fig.32 The percentage of water saved when the additional leakage is varied is shown. Fig.32 The excess leakage is measured in liters per minute (L / min).

[0339] To make the analysis easier to evaluate, the ranges for each of these parameters are assembled into Fig.33 in the table shown. Fig.33 The table in shows a summary of the percentage range of water saved for each of the parameters used in the model. Since the parameter ranges are listed in order from low to high, and the upper limit (Upper), lower limit (Lower) and percentage of water saved are listed without indicating the order relative to the parameter range, the curve slope (CurveSlope) is added to indicate the direction of water saving.

[0340] In this analysis, it was assumed that the ranges used for each parameter were reasonable in that they covered the legal range from minimum to maximum values. Given this, the total range of savings was from approximately 30% to as high as 60-70%. It can be further seen that for the ranges chosen, changes in IPAP and additional leakage had less impact on the percentage of water saved than the other parameters, with CPAP, EPAP, and I:E ratio having the greatest impact. Again, this conclusion may be limited in proportion to the reality of the ranges of parameters chosen in this analysis. Also note that only one parameter was varied at a time in this analysis, and the impact of changes in combined variables was not evaluated.

[0341] It must be noted that the model presented here has other limitations which would reduce the percentage savings. These limitations could include, for example, that any on-demand algorithm will not be completely accurate for a number of reasons (e.g., humidified gas mixes with dry gas as it flows down the circuit), and that the algorithm will make errors in ensuring proper humidification during the inspiration phase, which would require a longer than accurately timed "on" phase of operation. However, such errors are likely to represent (in Fig.33 These limitations may include, for example, the following: Because any on-demand algorithm must predict when to turn on the water, assuming that the water delivery mechanism is about 6 feet away from the patient, such an algorithm can only work accurately if the patient is breathing at a constant rhythm. If the patient's rhythm does vary, the algorithm will inevitably err on the side of staying on longer, with the ultimate fallback being that water should be delivered continuously. For patients with widely varying rhythms, in extreme cases, an on-demand algorithm may not be used at all, meaning that some patients may not be able to take advantage of the water savings.

[0342] In some embodiments, water savings in a very accurate on-demand system are on the order of 30%-60-70%, suggesting that a 50% water savings could be targeted. Note that this range is identified by changing only one input at a time, and does not include worse or better cases that may be associated with combined changes in various input values.

[0343] In some embodiments, changes in IPAP and additional leakage appear to have the least impact on water conservation, while CPAP, EPAP, and I:E appear to have the greatest impact.

[0344] In some embodiments, the model of perfect algorithm timing is not really reasonable in reality, which means that even if the patient has a very consistent breathing rhythm, the range will be at least a few percentage points lower. In some embodiments, for patients with poor rhythm, some patients may require the algorithm to deliver water almost continuously.

[0345] In some embodiments, it may be prudent to use the current water chamber size even in an on-demand system to cover patients with poor rhythm. However, if this is the case, an on-demand system may still provide other benefits, such as, but not limited to: a) patients with good rhythm are able to use a single fill of the reservoir longer; b) fewer rain-out terminations due to the drying effect of the algorithm's "off" condition.

[0346] System 100 was conceived in response to clinician complaints about excessive oxygen waste when using ventilators. System 100 reduces or eliminates supplemental gas waste (oxygen or water vapor) when using a pressure support ventilator with a passive flow circuit. For oxygen, any time bottled gas is used there is a savings. For oxygen concentrators, the algorithm increases the FiO2 of the gas for the same concentrator flow rate without the algorithm. When used to limit the delivery of humidity, the benefits include: a) reduced water usage, which can 1] extend water reservoir life, 2] allow for smaller humidifiers to be built; b) reduced rainout in the patient circuit, since dry air is passing through the tube most of the time; and c) reduced power consumption, since only half of the water is delivered as moisture.

[0347] In some embodiments, the system 100 includes an algorithm that controls the delivery of titrated supplemental gas to the patient circuit 106 so that it appears at the patient when the patient begins to inhale and ceases to appear when the patient completes inhalation. In some embodiments, the algorithm is a software algorithm that can be used in the applications described in this patent application. For example, applications of the algorithm include, but are not limited to: 1) reducing CPAP humidifier water usage by using a valve inside the humidifier chamber to allow air to flow through or around the humidifier as directed by the algorithm; 2) reducing oxygen waste in the oxygen mixing module of a pressure support ventilator; 3) reducing oxygen waste from bottled oxygen mixed into the low flow inlet of a pressure support ventilator; and 4) improving the delivery of oxygen fraction mixed into the low flow inlet of a pressure support ventilator from a concentrator.

[0348] In some embodiments, the system 100 is used on any ventilator having an oxygen mixing module or a low flow oxygen port. In some embodiments, the system 100 is used with any humidifier that is operated in conjunction with ventilation.

[0349] In some embodiments, an external flow measurement device may be used in system 100. In some embodiments, the external flow measurement device is configured to be connected to breathing circuit 106 and includes appropriate means for evaluating when valve 108 is opened and closed.

[0350] In some embodiments, the system 100 employs its own low flow port, so the low flow port 124 may not even be needed on the ventilator 104. Such a standalone device allows the present patent application to be used with any ventilator.

[0351] refer to Fig.34 , a method 700 for delivering oxygen is provided. The method 700 is implemented by a computer system 114 that includes one or more physical processors 116 that execute computer program instructions that, when executed, perform the method 700. In some embodiments, method 700 includes: at process 702, obtaining respiratory flow information for the patient from sensor 112; at process 704, using computer system 114, determining, by using the respiratory flow information, a volume of gas delivered to the patient during a breathing cycle of the patient and a volume of inspiratory gas delivered to the patient during an inspiratory phase of the breathing cycle; at process 706, using computer system 114, providing input to valve 108 based on the determined volumes, the provided input causing the valve to move between an open position and a closed position, in which the ventilator 104 receives an oxygen supply from oxygen source 102 and in which the ventilator is not in fluid communication with the oxygen source; at process 708, using accumulator 110 to accumulate an oxygen supply from the oxygen source when the valve is in the closed position; and at process 710, providing the oxygen supply accumulated in the accumulator to the ventilator when the valve is in the open state.

[0352] The method 700 also includes: obtaining the tube volume; and determining the volume difference between the volume of gas delivered to the patient during the patient's breathing cycle and the tube volume. The method 700 includes: providing an input to the valve 108 to move the valve 108 to an open position when the determined volume difference is delivered to the patient from the beginning of the next breathing cycle. The method 700 includes: maintaining the valve 108 in the open position until the inspiratory gas volume is delivered to the patient during the inspiratory phase of the breathing cycle; and after the inspiratory gas volume is delivered to the patient, providing an input to the valve 108 to move the valve 108 to a closed position.

[0353] In some embodiments, Figure 7The various computers and subsystems shown in may include one or more computing devices that are programmed to perform the functions described in the text. The computing device may include one or more electronic storage devices (e.g., database 132 or other electronic storage devices), one or more physical processors and / or other components programmed with one or more computer program instructions. The computing device may include communication lines or ports to enable information to be exchanged with a network (e.g., network 150) or other computing platforms via wired or wireless technology (e.g., Ethernet, optical fiber, coaxial cable, WiFi, Bluetooth, near field communication or other communication technology). The computing device may include multiple hardware components, software components and / or firmware components that operate together to provide the functions that belong to the server in this article. For example, the computing device may be implemented by a computing platform cloud that operates together as a computing device.

[0354] The electronic storage device may include a non-transient storage medium that stores information or data electronically. The electronic storage medium of the electronic storage device may include one or both of a system storage device (e.g., substantially non-removable) provided integrally with the server or a removable storage device that is removably connected to the server via, for example, a port (e.g., a USB port, a FireWire port, etc.) or a drive (e.g., a disk drive, etc.). The electronic storage device may include one or more of the following: an optically readable storage medium (e.g., an optical disk, etc.), a magnetically readable storage medium (e.g., a tape, a magnetic hard drive, a floppy disk drive, etc.), a charge-based storage medium (e.g., an EEPROM, a RAM, etc.), a solid-state storage medium (e.g., a flash drive, etc.), and / or other electronically readable storage media. The electronic storage device may include one or more virtual storage resources (e.g., a cloud storage device, a virtual private network, and / or other virtual storage resources). The electronic storage device may store software algorithms, information determined by a processor, information received from a server, information received from a client computing platform, or other information that enables the server to operate as described herein.

[0355] The processor may be programmed to provide information processing capabilities in system 100. As such, the processor may include one or more of the following: a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information. In some embodiments, the processor may include multiple processing units. These processing units may be physically located within the same device, or the processor may represent processing functionality of multiple devices operating in coordination. The processor may be programmed to execute computer program instructions to execute subsystems 212-220 (e.g., Figure 7The processor may be programmed to execute computer program instructions through software; hardware; firmware; some combination of software, hardware, or firmware; and / or other mechanisms for configuring processing capabilities on the processor.

[0356] It should be understood that the subsystems 212-220 (such as Figure 7 The functional descriptions provided herein are for purposes of illustration and not limitation, as subsystems 212-220 (such as Figure 7 As another example, additional subsystems may be programmed to perform functions that are attributed to subsystems 212-220 (such as Figure 7 Some or all of the functions shown).

[0357] In some embodiments, the system 100 may also include a communication interface configured to send the determined valve turn_on and valve turn_off to the valve 108 or system for further processing via an appropriate wireless communication method (e.g., Wi-Fi, Bluetooth, Internet, etc.). In some embodiments, the system 100 may include a recursive tuning subsystem configured to use available data or information to recursively tune the intelligent decision making subsystem of the system 100 to provide better overall valve turn_on and valve turn_off. In some embodiments, the intelligent decision making subsystem, the communication interface, and the recursive tuning subsystem may be part of a computer system (including the server 102).

[0358] In some embodiments, the subsystems of system 100 are configured to continuously obtain subsequent respiratory flow information. That is, the subsystems can continuously obtain subsequent respiratory flow. As an example, the subsequent information may include additional information corresponding to a subsequent time (after the time corresponding to the information used to determine valve turn_on and valve turn_off). The subsequent information can be used to further update or modify valve turn_on and valve turn_off (for example, new information can be used to dynamically update or modify valve turn_on and valve turn_off), etc. For example, the subsequent information can also be configured to provide further input to determine valve turn_on and valve turn_off. In some embodiments, the subsystems of system 100 can be configured to determine valve turn_on and valve turn_off based on a recursive refinement profile based on previously collected or subsequent respiratory flow information (for example, a profile refined by recursive application of a profile refinement algorithm).

[0359] In the claims, any reference signs placed between brackets shall not be construed as limiting the claim. The words "comprise" or "include" do not exclude the presence of elements or steps other than those listed in the claim. In a device-type claim that lists several units, several of these units may be embodied as one and the same item of hardware. The word "a" or "an" before an element does not exclude the presence of multiple such elements. In any device-type claim that lists several units, several of these units may be embodied as one and the same item of hardware. Although certain elements are recorded in different dependent claims, this does not indicate that these elements cannot be used in combination.

[0360] Although the present patent application is described in detail based on what is currently considered to be the most practical and preferred embodiments for the purpose of illustration, it should be understood that such details are only used for this purpose, and the present patent application is not limited to the disclosed embodiments, but is intended to cover modifications and equivalent arrangements within the spirit and scope of the claims. For example, it should be understood that the present patent application anticipates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.

Claims

1. A system (100) for delivering oxygen, comprising: an oxygen source (102); a ventilator (104) operatively connected to the oxygen source to receive a supply of oxygen from the oxygen source, the ventilator being configured to provide a gas comprising a mixture of the oxygen supply and air to a patient via a breathing circuit (106); a valve (108) operatively connected to the ventilator and the oxygen source, the valve having: a) an open position in which the ventilator receives the supply of oxygen from the oxygen source, and b) a closed position in which the ventilator is not in fluid communication with the oxygen source; a sensor (112) configured to measure respiratory flow information for the patient; and A computer system (114) comprising one or more physical processors operatively connected to the sensor and the valve, the one or more physical processors being programmed with computer program instructions that, when executed, cause the computer system to: determining a volume of gas delivered to the patient during a breathing cycle of the patient and a volume of inspiratory gas delivered to the patient during an inspiratory phase of the breathing cycle by using the respiratory flow information; Get tube volume; determining a volume difference between the volume of gas delivered to the patient during the breathing cycle of the patient and the tube volume; and An input is provided to the valve to move the valve between the open position and the closed position based on the determined volume, wherein the input is provided to the valve to move the valve to the open position i) when the determined volume difference is delivered to the patient from the beginning of a next breathing cycle or ii) when the determined volume difference minus a margin volume is delivered to the patient from the beginning of a next breathing cycle.

2. The system according to claim 1, wherein: The computer system is configured to: maintain the valve in the open position until the inspiratory gas volume is delivered to the patient during the inspiratory phase of the breathing cycle; and after the inspiratory gas volume is delivered to the patient, provide an input to the valve that causes the valve to move to the closed position.

3. The system according to claim 1, wherein: The oxygen source is selected from the group consisting of an oxygen concentrator, a portable oxygen concentrator, a pressurized oxygen tank, a compressed oxygen tank, an oxygen generator, an oxygen mixing module, and an oxygen cylinder.

4. The system according to claim 1, wherein: The oxygen source is an oxygen concentrator and further includes an accumulator configured to accumulate the oxygen supply from the oxygen source when the valve is in the closed position and to provide the oxygen supply to the ventilator when the valve is in the open position.

5. A computer readable storage medium comprising computer program instructions which, when executed, perform a method for controlling oxygen delivery, the method comprising: obtaining respiratory flow information for the patient from a sensor (112); determining a volume of gas delivered to the patient during a breathing cycle of the patient and a volume of inspiratory gas delivered to the patient during an inspiratory phase of the breathing cycle by using the respiratory flow information; Get tube volume; determining a volume difference between the volume of gas delivered to the patient during the breathing cycle of the patient and the tube volume; and Based on the determined volume, an input is provided to a valve (108) to move the valve between an open position in which the ventilator receives a supply of oxygen from an oxygen source and a closed position in which the ventilator is not in fluid communication with the oxygen source, wherein the input is provided to the valve to move the valve to the open position i) when the determined volume difference is delivered to the patient from the beginning of a next breathing cycle or ii) when the determined volume difference minus a margin volume is delivered to the patient from the beginning of a next breathing cycle.

6. The computer-readable storage medium according to claim 5, wherein: The oxygen source is selected from the group consisting of an oxygen concentrator, a portable oxygen concentrator, a pressurized oxygen tank, a compressed oxygen tank, an oxygen generator, an oxygen mixing module, and an oxygen cylinder.

7. The computer-readable storage medium of claim 5, the method further comprising: accumulating the oxygen supply from the oxygen source using an accumulator (110) when the valve is in the closed position; and When the valve is in the open position, the supply of oxygen accumulated in the reservoir is provided to the ventilator.

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