Gas monitoring

Abstract

To provide a device and / or a method for obtaining an estimated value of a parameter of gas exhaled by a patient.SOLUTION: Disclosed herein are methods and devices for determining a parameter of a gas present in an exhalation gas flow, comprising providing a device gas flow having a time-varying parameter to a patient, measuring a parameter of a gas present in a combined gas outflow from the patient, and determining the parameter of the gas present in the exhalation gas flow using the measured parameter of the gas present in the combined gas outflow and the time-varying parameter.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to a method and apparatus for determining parameters of the gas flow exhaled by a patient when using a breathing apparatus. [Background technology]

[0002] Background of the Invention When providing flow support / therapy to a patient, clinicians often monitor patient exhaled gas parameters such as O fraction and / or CO fraction. Due to the mixing of various flows, the monitored gas parameters often do not truly reflect the actual exhaled gas parameters. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present invention to provide an apparatus and / or method for obtaining estimates of parameters of gases exhaled by a patient. [Means for solving the problem]

[0004] In one aspect, the present invention may include a method for determining a parameter of gas present in an exhalation gas flow, the method comprising providing a device gas flow having a time-varying parameter to a patient, measuring a parameter of gas present in a combined gas outflow from the patient, and using the measured parameter and the time-varying parameter of gas present in the combined gas outflow to determine the parameter of gas present in the exhalation gas flow.

[0005] In another aspect, the invention may include an apparatus for providing a system gas flow and determining parameters of an exhaled patient gas flow, the apparatus including a flow source, a sensor for sensing a combined gas outflow, and a controller, the apparatus configured to provide a system gas flow having a time-varying parameter, determine parameters of gases present in the combined gas outflow from the patient, the combined gas outflow including a leak gas flow from the system gas flow and an exhaled gas flow from the patient including gas, and determine parameters of gases present in the exhaled gas flow using the determined gas parameters and the time-varying parameter.

[0006] Optionally, the time varying parameter is one or more of a flow rate of the system gas flow, or a gas ratio, and optionally the gas ratio is the fraction of a gas present in the system gas flow, or the partial pressure of a gas present in the system gas flow.

[0007] Optionally, the gas ratio is a gas fraction, preferably an O2 fraction, or a gas partial pressure, preferably an O2 partial pressure.

[0008] Optionally, the method or device includes providing a device gas flow during an anesthesia procedure.

[0009] Optionally, device gas flow is provided via a non-sealing patient interface, preferably a non-sealing cannula.

[0010] Optionally, the system gas flow is a high flow gas flow.

[0011] Optionally, the method or apparatus further comprises humidifying the apparatus gas flow.

[0012] Optionally, determining a parameter of a gas present in the exhalation gas flow using a measured parameter of a gas present in the composite gas outflow includes measuring only one gas and only a time-varying parameter, the time-varying parameter being flow rate.

[0013] In another aspect, the invention may include a method for determining a parameter of gas present in an exhalation gas flow, the method including providing a system gas flow having a time-varying flow rate to a patient; determining a parameter of gas present in a combined gas outflow from the patient, the patient combined gas outflow including a leak gas flow from the system gas flow and an exhalation gas flow from the patient including gas; and determining the parameter of gas present in the exhalation gas flow using the determined parameter of gas present in the combined gas outflow and the time-varying flow rate.

[0014] Optionally, the device gas flow having a time-varying flow rate includes at least a first flow rate at a first time and a second flow rate at a second time, and determining parameters of gases present in the expiratory gas flow using the determined parameters of gases present in the composite gas outflow and the time-varying flow rates includes using determined parameters of gases present in the composite outflow determined at the first flow rate and determined at the second flow rate.

[0015] Optionally, the parameter includes the fraction of the gas component in the exhaled gas flow.

[0016] Optionally, the gas is an anesthetic agent such as CO2, O2, nitrogen, helium, and / or sevoflurane, and / or the sensor is configured to detect one or more of the following in the combined gas outflow: CO2, O2, nitrogen, helium, and / or an anesthetic agent such as sevoflurane.

[0017] Optionally, parameters of the gases present in the combined gas outflow are determined during the inspiration and / or expiration phase of the patient's breath.

[0018] Optionally, the parameter of the gas present in the exhalation gas flow is a gas fraction, and the determined parameter and the time-varying flow rate of the gas present in the combined gas outflow are used to calculate the fraction of the gas present in the exhalation gas flow (F E ) is determined by

number

[0019] Optionally, the parameter of the gas present in the exhalation gas flow is a gas fraction, and the determined parameter and the time-varying flow rate of the gas present in the combined gas outflow are used to calculate the fraction of the gas present in the exhalation gas flow (F E ) is determined by the gas fraction F E (t), Q o (t), Qo (t+Δt),F m (t+Δt),F m (t) [In the formula, F m (t), the volume fraction of gas components measured in the patient combined gas outflow 15′ from the patient at time t (which is preferably the measured CO2 / O2 fraction parameter of the combined gas outflow 15′ measured by sensor 14); F m (t) is preferably measured at the patient's mouth when the patient's mouth is open and / or at the nose when the patient's mouth is closed; Q o (t), the flow rate of the system gas flow 11′ provided to the patient from the breathing apparatus (system gas flow rate) at time t; F m (t+Δt), the volume fraction of the gas components measured in the patient combined gas outflow 15′ at time t+Δt (which is preferably the measured CO2 / O2 fraction parameter of the combined gas outflow measured by sensor 14), F m (t+Δt) is preferably measured in the patient's mouth; Q o (t+Δt), the flow rate of the system gas flow 11′ provided to the patient from the breathing apparatus at time t+Δt (system gas flow rate)] as a function of

[0020] Optionally, the parameter of the gas present in the exhalation gas flow is a gas fraction, the gas preferably being CO2, and the determined parameter and time-varying flow rate of the gas present in the combined gas outflow are used to determine the gas fraction (F) in the exhalation gas flow. E ) is determined by

number

[0021] Optionally, parameters of the gases present in the combined gas outflow from the patient are measured at or near the patient's mouth and / or nose.

[0022] Optionally, the first flow rate and the second flow rate are different flow rates.

[0023] Optionally, the first flow rate and the second flow rate are high flow rates.

[0024] Optionally, the first flow rate and the second flow rate are about 0 L / min or greater, preferably about 20 L / min or greater, more preferably about 20 L / min to about 90 L / min.

[0025] Optionally, the time-varying flow rate is a fluctuation having a varying flow rate of about 0 L / min or greater, preferably about or greater than about 20 L / min, more preferably between about 20 L / min and about 90 L / min.

[0026] Optionally, the method includes providing a device gas flow during an anesthesia procedure.

[0027] Optionally, device gas flow is provided via a non-sealing patient interface, preferably a non-sealing cannula.

[0028] Optionally, the system gas flow is a high flow gas flow.

[0029] Optionally, the method further comprises humidifying the apparatus gas flow.

[0030] Optionally, determining a parameter of a gas present in the exhalation gas flow using a measured parameter of a gas present in the composite gas outflow includes measuring only one gas and only a time-varying parameter, the time-varying parameter being flow rate.

[0031] In another aspect, the present invention may include a method for determining a parameter of gas present in an exhaled gas flow, the method including providing a patient with a system gas flow having a time-varying gas ratio (e.g., gas fraction); determining a parameter of gas present in a combined gas outflow from the patient, the patient combined gas outflow including a leak gas flow from the system gas flow and an exhaled gas flow from the patient including gas; and using the determined parameter of gas present in the combined gas outflow and the time-varying gas ratio (e.g., gas fraction) to determine the parameter of gas present in the exhaled gas flow.

[0032] Optionally, the device gas flow having a time-varying gas fraction includes at least a first gas fraction at a first time and a second gas fraction at a second time, and determining parameters of gas present in the exhalation gas flow using the determined parameters of gas present in the combined gas outflow and the time-varying gas fraction includes using determined parameters of gas present in the combined outflow determined at the first gas fraction and determined at the second gas fraction.

[0033] Optionally, the parameter includes the fraction of the gas component in the exhaled gas flow.

[0034] Optionally, the gas is CO2, O2, nitrogen, and / or helium, an anesthetic such as sevoflurane.

[0035] Optionally, parameters of the gases present in the combined gas outflow are determined during the inspiration and / or expiration phase of the patient's breath.

[0036] Optionally, the parameter of the gas present in the exhalation gas flow is a gas fraction, and the determined parameter of the gas present in the combined gas outflow and the time-varying gas fraction F E (t) is used to calculate the fraction of gas present in the exhaled gas flow (F E ) is determined by the gas fraction, F o (t),F o (t+Δt),F m (t+Δt),F m (t) F E (t) is the CO2 and / or O2 gas fraction in the expired patient gas flow (volume fraction of expired gas) at time t; F m (t), the fraction of CO2 measured in the combined gas outflow at time t; F o (t), the gas fraction of the device gas flow delivered to the patient at time t (Device Gas Flow Gas Fraction); F m (t+Δt), the fraction of CO2 measured in the combined gas outflow at time t+Δt, F o (t+Δt), the gas fraction of the machine gas flow delivered to the patient at time t+Δt (machine gas flow gas fraction); Q o is the flow rate of the device gas flow, F E is the fraction of gas in the expiratory gas flow as a function of

[0037] Optionally, the parameter of the gas present in the exhaled gas flow is a gas fraction, the gas preferably being CO, O, nitrogen, helium, and / or an anesthetic agent such as sevoflurane, and determining the gas fraction in the exhaled gas flow using the determined parameter and the time-varying gas fraction of the gas present in the combined gas outflow comprises:

number

[0038] Optionally, parameters of the gases present in the combined gas outflow from the patient are measured at or near the patient's mouth and / or nose.

[0039] Optionally, the first gas fraction and the second gas fraction are different gas fractions.

[0040] Optionally, the gas is O2 and the method comprises determining the O2 ratio, and F mCO2 ,k,Q o ,Q E [In the formula, F mCO2 is the fraction of CO2 in the patient combined gas outflow from the patient, k is the fraction of system gas flow exiting the patient's mouth (and (1-k) is the fraction through the nose); Q o is the flow rate of the device gas flow, Q E is the patient's expiratory gas flow rate] and determining the fraction of CO2 present in the exhaled gas flow using a function of

[0041] Optionally, the gas is O2 and the method comprises determining the O2 ratio and

number

[0042] Optionally, the gas is O2 and the method comprises determining the O2 ratio and F mCO2 ,F mO2 ,F EO2 ,F oO2 [In the formula, F mCO2 is the measured fraction of CO2 in the patient combined gas outflow from the patient, F mO2 is the measured fraction of O2 in the patient combined gas outflow from the patient, F EO2 is the fraction of O2 in the exhaled patient gas flow F oO2is the fraction of O2 in the system gas flow delivered to the patient from the respiratory system] and determining the fraction of CO2 present in the exhaled gas flow using a function of

[0043] Optionally, the gas is O2 and the method comprises determining the O2 ratio and

number

[0044] In another aspect, the invention may include an apparatus for providing a system gas flow and determining parameters of gases present in an expired patient gas flow, the apparatus including a flow source, a sensor for sensing a combined gas outflow, and a controller, the apparatus configured to provide a system gas flow having a time-varying flow rate and determine parameters of gases present in the combined gas outflow from the patient, the combined gas outflow including leakage gas flow from the system gas flow and an expired gas flow from the patient including gas, and to determine the parameters of gases present in the expired gas flow using the determined parameters of gases present in the combined gas outflow and the time-varying flow rate.

[0045] Optionally, the apparatus further comprises a humidifier for humidifying the apparatus gas flow.

[0046] Optionally, the device further comprises a non-sealing patient interface, preferably a non-sealing nasal cannula, for providing device gas flow to the patient.

[0047] Optionally, the system gas flow is a high flow gas flow.

[0048] Optionally, the device gas flow having a time-varying flow rate includes at least a first flow rate at a first time and a second flow rate at a second time, and determining parameters of gases present in the expiratory gas flow using the determined parameters of gases present in the composite gas outflow and the time-varying flow rates includes using determined parameters of gases present in the composite outflow determined at the first flow rate and determined at the second flow rate.

[0049] Optionally, the parameter includes the fraction of the gas component in the exhaled gas flow.

[0050] Optionally, the gas is an anesthetic agent such as CO2, O2, nitrogen, helium, and / or sevoflurane, and / or the sensor is configured to detect one or more of the following in the combined gas outflow: CO2, O2, nitrogen, helium, and / or an anesthetic agent such as sevoflurane.

[0051] Optionally, the parameter of the gas present in the exhalation gas flow is a gas fraction, and the determined parameter and the time-varying flow rate of the gas present in the combined gas outflow are used to calculate the fraction of the gas present in the exhalation gas flow (F E ) is determined by the gas fraction, Q o (t), Q o (t+Δt),F m (t+Δt),F m (t) [In the formula, F E (t) is the gas component concentration in the exhaled patient gas flow (volume fraction of exhaled gas), F m (t), the fraction of gas components measured in the patient composite gas outflow at time t; Q o (t), the flow rate of the device gas flow delivered to the patient at time t (device gas flow rate); F m (t+Δt), the fraction of gas components measured in the patient combined gas outflow at time t+Δt (this is the measured CO2 / O2 fraction parameter of the combined gas outflow); Q o (t+Δt), the rate of device gas flow delivered to the patient at time t+Δt (Device Gas Flow Rate)] as a function of

[0052] Optionally, the parameter of the gas present in the exhaled gas flow is a gas fraction, the gas being preferably CO2, and the determined parameter of the gas present in the combined gas outflow (F E ) and time-varying flow rate to determine the gas fraction in the exhaled gas flow,

number

[0053] Optionally, a sensor is positioned to measure a parameter of the gas present in the combined gas outflow from the patient at or near the patient's mouth and / or nose.

[0054] In another aspect, the invention may include an apparatus for providing a system gas flow and determining a parameter of gas present in an expired patient gas flow, the apparatus including a flow source, a sensor for sensing a combined gas outflow, and a controller, the apparatus configured to provide a system gas flow having a time-varying gas ratio (e.g., gas fraction), determine a parameter of gas present in the combined gas outflow from the patient, the combined gas outflow including a leak gas flow from the system gas flow and an expired gas flow from the patient including gas, and determine the parameter of gas present in the expired gas flow using the determined parameter of gas present in the combined gas outflow and the time-varying gas ratio (e.g., gas fraction).

[0055] Optionally, the device gas flow having a time-varying gas fraction includes at least a first gas fraction at a first time and a second gas fraction at a second time, and determining parameters of gas present in the exhalation gas flow using the determined parameters of gas present in the combined gas outflow and the time-varying gas fraction includes using determined parameters of gas present in the combined outflow determined at the first gas fraction and determined at the second gas fraction.

[0056] Optionally, the parameter includes the fraction of the gas component in the exhaled gas flow.

[0057] Optionally, the gas is CO2, O2, nitrogen, helium, and / or an anesthetic such as sevoflurane.

[0058] Optionally, the parameter of the gas present in the exhalation gas flow is a gas fraction, and the determined parameter of the gas present in the combined gas outflow and the time-varying gas fraction are used to determine the fraction of the gas present in the exhalation gas flow (FE ) is determined by the gas fraction, F,F o (t+Δt),F m (t+Δt),F m (t) During the ceremony F E (t) is the gas component concentration in the exhaled patient gas flow (volume fraction of exhaled gas), F m (t), the fraction of gas components measured in the patient composite gas outflow at time t; F o (t), the gas fraction of the device gas flow delivered to the patient at time t (Device Gas Flow Gas Fraction); F m (t+Δt), the fraction of gas components measured in the patient combined gas outflow at time t+Δt (this is the measured CO2 / O2 fraction parameter of the combined gas outflow); Fo (t+Δt), the gas fraction of the machine gas flow delivered to the patient at time t+Δt (machine gas flow gas fraction) as a function of

[0059] Optionally, the parameter of the gas present in the exhaled gas flow is a gas fraction, preferably CO, O, nitrogen, helium, and / or an anesthetic agent such as sevoflurane, and the determined parameter and the time-varying gas fraction of the gas present in the combined gas outflow are used to calculate the gas fraction (F) in the exhaled gas flow. E ) is determined by

number

[0060] Optionally, a sensor is positioned to measure a parameter of the gas present in the combined gas outflow from the patient at or near the patient's mouth and / or nose.

[0061] In another aspect, the invention may comprise a method for determining the O2 and / or CO2 fraction present in an exhaled gas flow, the method comprising providing a humidified high flow device gas flow having a time-varying flow rate to a patient via a non-sealing nasal cannula, measuring the fraction of O2 and / or CO2 present in a combined gas outflow from the patient, and using the measured fraction of O2 or fraction of CO2 present in the combined gas outflow and the time-varying flow rate to determine the fractional O2 and / or CO2 present in the exhaled gas flow.

[0062] In another aspect, the invention may include a non-transitory computer-readable medium having stored thereon computer-executable instructions that, when executed on one or more processing devices, cause the one or more processing devices to implement a method for determining parameters of gases present in an exhaled gas flow, the method including providing a system gas flow having time-varying parameters to a patient, measuring parameters of gases present in a combined gas outflow from the patient, and determining parameters of gases present in an exhaled gas flow using the measured parameters and the time-varying parameters of gases present in the combined gas outflow.

[0063] In another aspect, the invention may include a method of determining a parameter of an exhaled patient gas flow, the method including providing a system gas flow to a patient having a time-varying parameter; determining a parameter of a combined gas outflow from the patient, the combined gas outflow including a leakage gas flow from the system gas flow and an exhaled patient gas flow including gas components, the determined parameter of the combined gas outflow being a ratio of the gas components in the combined gas outflow; and determining a ratio of gas present in the exhaled gas flow using the determined parameter of the combined gas outflow and the time-varying parameter.

[0064] Optionally, the sensor Mouth and nose, mouth, or nose The composite gas flow is detected by detecting the gas flows of the two gases.

[0065] In another aspect, the present invention provides a method for determining the fraction of CO present in an exhaled gas flow, comprising providing a high flow device gas flow to a patient, determining the fraction of O in the patient's exhaled gas flow, and measuring the determined O ratio and F m CO2,k,Q o ,Q E During the ceremony F mCO2 is the volume fraction of CO2 in the device gas flow, k is the fraction of system gas flow exiting the patient's mouth (and (1-k) is the fraction through the nose); Q o is the flow rate of the device gas flow, Q E is the patient's expiratory gas flow rate determining the fraction of CO2 present in the exhaled gas flow using a function of The method may include a method comprising:

[0066] In another aspect, the present invention provides a method for determining the fraction of CO present in an exhaled gas flow, comprising providing a high flow device gas flow to a patient, determining the fraction of O in the patient's exhaled gas flow, and measuring the determined O ratio and

number

[0067] Reference to a range of numerical values ​​disclosed herein (e.g., 1 to 10) also incorporates reference to every rational number within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10), and also to any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and therefore, every subrange of every range explicitly disclosed herein is hereby expressly disclosed. These are merely examples of what is specifically intended, and all possible combinations of numerical values ​​between the lowest and highest values ​​recited are also considered to be expressly disclosed in this application.

[0068] As used herein, the term "comprising" means "consisting at least in part of." When interpreting each statement herein containing the term "comprising," it is possible that features other than those preceded by the term may be present. Related terms such as "comprise" and "comprises" are to be interpreted similarly. Unless the context clearly requires otherwise, throughout the specification and claims, words such as "comprisse," "comprising," and the like shall be interpreted in an inclusive sense, i.e., "including, but not limited to," as opposed to an exclusive or exhaustive sense.

[0069] The phrase "computer-readable medium" should be interpreted to include a single medium or multiple media. Examples of multiple media include centralized or distributed databases and / or associated caches. These multiple media store one or more sets of computer-executable instructions. The phrase "computer-readable medium" should also be interpreted to include any medium capable of storing, encoding, or carrying a set of instructions for execution by a processor of a computing device, causing the processor to perform any one or more of the methods described herein. A computer-readable medium can also store, encode, or carry data structures used by or associated with these sets of instructions. The phrase "computer-readable medium" includes solid-state memory, optical media, and magnetic media.

[0070] Where reference is made herein to patent specifications, other external documents, or other sources of information, this is generally to provide context for discussing features of the present disclosure. Unless otherwise expressly stated, the reference to such external documents should not be construed as an admission that such documents or such sources are prior art or form part of the common general knowledge in the art in any jurisdiction.

[0071] The present invention may also be broadly comprised of the parts, elements, and features individually or collectively referenced or shown in the specification of this application in any or all combinations of two or more of the parts, elements, or features. Where reference is made in the foregoing description to integers or components having known equivalents thereof, those integers are incorporated herein as if set forth individually.

[0072] Numerous modifications in structure and widely different embodiments and applications of the present invention will occur to those skilled in the art to which the present invention pertains without departing from the scope of the present invention as defined in the appended claims. The present disclosure and descriptions herein are purely illustrative and are not intended to be limiting in any sense. Where reference is made herein to specific integers that have known equivalents in the art to which the present invention pertains, such known equivalents are deemed to be incorporated herein as if individually set forth. The present invention consists of the foregoing and also contemplates structures of which the following merely exemplifications are set forth.

[0073] The embodiments will be described with reference to the following drawings. [Brief explanation of the drawings]

[0074] [Figure 1A] 1 shows the flow between the respiratory device, the patient, and the patient's environment. [Figure 1B] A breathing apparatus for providing high flow. [Figure 2] 1 is a trace of CO2 fraction in combined and exhaled gas flows. [Figure 3A] The components of the system gas flow (time varying flow rates) and the combined composite gas outflow are shown. [Figure 3B] 10 shows an alternative system gas flow. [Figure 3C] 10 shows an alternative system gas flow. [Figure 4] 1 is an embodiment of a respiratory device implementing a time-varying device flow and estimating exhaled gas parameters. [Figure 5] 1 illustrates an embodiment of a method implemented by a respiratory device to estimate time-varying flow gas flow and exhaled gas parameters. [Figure 6A] The composition of the device gas flow (time-varying gas fraction) and the combined composite gas outflow are shown. [Figure 6B] 10 shows an alternative system gas flow. [Figure 6C] 10 shows an alternative system gas flow. [Figure 7] 1 is an embodiment of a method implemented by a respiratory device to estimate time-varying gas fractionation device gas flow and exhaled gas parameters. [Figure 8] Illustrates various gas flows into and out of the patient. DETAILED DESCRIPTION OF THE INVENTION

[0075] Detailed Description 1. Overview The present embodiment relates to determining gas parameters of the gas flow exhaled by a patient ("exhaled gas flow") when using a respiratory apparatus that provides (preferably high) flow rates through a non-sealing patient interface, such as a non-sealing nasal cannula. ("Determining a gas parameter" may mean, but is not limited to, determining, obtaining, or otherwise acquiring an estimate, value, indication, or other information of or relating to a gas parameter.)

[0076] The described embodiments provide devices and methods for determining a parameter of a gas flow exhaled by a patient, the parameter relating to the ratio (e.g., concentration / fraction or partial pressure) of a gas component in an exhaled gas flow that includes two or more constituent gas components. In certain situations, the patient is breathing spontaneously (i.e., breathing with their own effort, even if shallow or reduced breathing). For example, the exhaled gas flow may include O, CO, nitrogen, helium, an anesthetic (e.g., sevoflurane), etc., and the parameter may be the ratio (e.g., concentration / fraction or partial pressure) of CO or the ratio (e.g., concentration / fraction or partial pressure) of O in the gas flow exhaled by the patient. Here, the gas component is CO or O, and the parameter is the ratio of the gas components that make up the exhaled gas flow. In some embodiments, the parameter may relate to gases other than CO or O.

[0077] A medical professional may wish to obtain an estimate of the expiratory gas flow parameter, for example, when monitoring a patient during a medical procedure. A medical procedure should be considered broadly and may include all aspects of the delivery of a medical procedure, including pre- and post-operative procedures, any time before, during, or after a surgical procedure, sedation or anesthesia (sedation and anesthesia are more generally referred to herein as "anesthesia procedures"), including the administration of sedatives and / or anesthetics during the oxygenation and pre-oxygenation phase or procedure, or at any other time. A medical procedure may also include providing respiratory assistance, such as high-flow respiratory assistance. In the context of this specification, a medical procedure may also include monitoring a patient, regardless of whether a specific procedure is provided to the patient. The described embodiments are not limited to use solely in medical procedures. The described embodiments may be used in an ICU or any other setting where respiratory assistance is provided.

[0078] In this specification, references to "exhale" may be used interchangeably with "expire."

[0079] As used herein, references to "proportion" in the context of a gas refer to any relative measure of a constituent gas component in a total gas that includes two or more constituent gas components. For example, a ratio can include: ·Volume fraction, fractionation, Volume concentration, ·concentration, Molarity, ·Divider pressure

[0080] The ratio measured may be a parameter measured by the sensor used, whether it be concentration, fraction, partial pressure, or other. The ratio determined may be a parameter desired by the user and / or processed by or associated with a component of the respiratory system.

[0081] References herein to "concentration" may also be referred to as "fraction" and may be expressed as the volume ratio of the gas of interest to the volume of the overall constituent gases in the gas flow, whether it be exhaled gas flow, device flow, or any other flow. However, the parameters may be different measurements and the gases may be different. These are merely examples.

[0082] The gas associated with the gas parameter being determined may be, but is not limited to, oxygen (O), carbon dioxide (CO), nitrogen (N), helium (He), or sevoflurane. Where a particular gas is referred to herein, it will be understood that this is merely an example and that the description may apply to any gas, not just the one referred to.

[0083] As used herein, "high flow" refers to any gas flow having a normal / higher-than-normal flow rate, for example, but not limited to, higher than the normal inspiratory flow rate of a healthy patient. This may be provided by a non-sealing breathing system in which a significant leak occurs at the entrance to the patient's airway due to a non-sealing patient interface, e.g., non-sealing prongs. Humidification may also be provided to improve patient comfort, compliance, and safety. Alternatively or additionally, this may be higher than other threshold flow rates relevant to the context. For example, if a gas flow is provided to a patient at a rate that meets inspiratory demand, that flow may be considered "high flow" because it is higher than the nominal flow rate that could have been provided. Therefore, "high flow" is context-dependent, and what constitutes a "high flow" depends on many factors, such as the patient's health status, the type of treatment / therapy / assistance provided, the nature of the patient (large, small, adult, pediatric), etc. One of ordinary skill in the art knows what constitutes a "high flow" from the context. It is a magnitude of flow that exceeds and exceeds the flow rate that could have been provided.

[0084] However, without limitation, some indications of high flow rates may be as follows: In some configurations, delivery of gas to the patient at a flow rate of about 5 or 10 liters per minute (5 or 10 LPM or L / min) or greater In some configurations, delivery of gas to the patient at a flow rate of about 5 or 10 LPM to about 150 LPM, or about 15 LPM to about 95 LPM, or about 20 LPM to about 90 LPM, or about 25 LPM to about 85 LPM, or about 30 LPM to about 80 LPM, or about 35 LPM to about 75 LPM, or about 40 LPM to about 70 LPM, or about 45 LPM to about 65 LPM, or about 50 LPM to about 60 LPM. For example, according to these various embodiments and configurations described herein, the flow rate of gas supplied or provided to the interface through the system or from the flow source can include, but is not limited to, flows of at least about 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 LPM, or more, and an effective range can be selected to be any of these values ​​(e.g., about 20 LPM to about 90 LPM, about 40 LPM to about 70 LPM, about 40 LPM to about 80 LPM, about 50 LPM to about 80 LPM, about 60 LPM to about 80 LPM, about 70 LPM to about 100 LPM, about 70 LPM to about 80 LPM).

[0085] At "high flow rates," the delivered gas is selected, for example, depending on the therapeutic application. The delivered gas may include a percentage of oxygen. In some configurations, the percentage of oxygen in the delivered gas may be about 15% to about 100%, about 20% to about 100%, or about 21% to about 100%, or about 30% to about 100%, or about 40% to about 100%, or about 50% to about 100%, or about 60% to about 100%, or about 70% to about 100%, or about 80% to about 100%, or about 90% to about 100%, or about 100%, or 100%.

[0086] In some embodiments, the delivered gas may include a percentage of carbon dioxide. In some configurations, the percentage of carbon dioxide in the delivered gas may be greater than 0%, between about 0.3% and about 100%, between about 1% and about 100%, between about 5% and about 100%, between about 10% and about 100%, between about 20% and about 100%, between about 30% and about 100%, between about 40% and about 100%, between about 50% and about 100%, between about 60% and about 100%, between about 70% and about 100%, between about 80% and about 100%, between about 90% and about 100%, about 100%, or 100%.

[0087] "High flow" flow rates for premature babies / infants / children (with body masses ranging from about 1 to about 30 kg) can vary. Therapeutic flow rates can be set at 0.4-0.8 L / min / kg, with a minimum of about 0.5 L / min and a maximum of about 25 L / min. For patients weighing less than 2 kg, the maximum flow is set at 8 L / min.

[0088] The variable flow is set at 0.05-2 L / min / kg, with a preferred range of 0.1-1 L / min / kg, and another preferred range of 0.2-0.8 L / min / kg.

[0089] Therapeutic flow rates can be time-varying (e.g., fluctuating), i.e., the therapeutic flow can have a time-varying (e.g., fluctuating) flow component, which can aid in therapy.

[0090] It should be noted that embodiments herein also have a time-varying (e.g., fluctuating) signature flow rate, which may be in addition to the therapeutic flow rate. Thus, when a therapeutic time-varying flow rate is used, the gas flow rate from the device has a therapeutic time-varying gas flow component (portion) and a signature time-varying flow rate component (portion). The therapeutic time-varying flow rate may have a different purpose than the signature time-varying flow rate and may be of a different frequency and / or amplitude (but they may overlap or be the same). The signature flow rate may be lower, the same, or higher than the therapeutic flow rate. The signature flow rate frequency may be lower, the same, or higher than the therapeutic flow rate frequency (if time-varying). In some embodiments, the signature flow rate has a higher frequency than the therapeutic flow rate. The therapeutic time-varying flow rate provides respiratory support, airway clearance, oxygenation, etc., while the signature time-varying flow rate aids in the determination of gas parameters. Signature time-varying flow rates are described in more detail below. Throughout the specification, unless otherwise stated, the focus will be on clinical time-varying flow rates, but this does not exclude the possibility that therapeutic time-varying flow rates for therapeutic reasons may also exist.

[0091] As an example, the signature flow rate can be stepped between a first flow rate and a second flow rate, one or both of which can be in the range of approximately 0 LPM to 70 LPM. The maximum signature flow rate can be a therapeutic flow rate. The signature flow rate can be combined with (e.g., added to) the therapeutic flow rate or can form part or all of the therapeutic flow rate. That is, the therapeutic flow rate itself can be a signature flow rate. In some embodiments, the signature flow rate can be related to the therapeutic flow rate as a percentage. For example, a signature time-varying flow rate (adult) can be: Approximately 0% to approximately 200% of therapeutic flow rate Approximately 0% to 100% of therapeutic flow rate Approximately 100% to 200% of the therapeutic flow rate, or Approximately 50% to 150% of the therapeutic flow rate Within the range of and / or Approximately 0 to 140 LPM Approximately 0 to 70 LPM Approximately 70 to 140 LPM Approximately 40 to 100 LPM, or Approximately 20 to 60 LPM is within the range.

[0092] Note also that these are not limiting flows, and signature flows can be negative, but when combined with therapeutic flows will result in a positive total flow.

[0093] High flow rates have been found to be effective in meeting or exceeding a patient's normal natural inspiratory flow, enhancing a patient's oxygenation, and / or reducing the work of breathing. Additionally, high flow rates can create a flushing effect in the nasopharynx, such that the anatomical dead space in the upper airway is flushed by the high incoming gas flow. This creates a reservoir of fresh gas available for each breath while minimizing rebreathing of carbon dioxide, nitrogen, etc.

[0094] By way of example, a high flow respiratory device 10 will be described, e.g., with reference to Figures 1A and 1B. Generally, the device includes a main housing 10 enclosing a flow generator 50 in the form of a motor / impeller arrangement, an optional humidifier 52, a controller 19, and a user input / output interface (e.g., including a display and input devices such as buttons, a touchscreen, etc.). The controller 19 is configured or programmed to control the components of the device, including operating the flow generator to generate a flow of gas (gas flow) for delivery to the patient, operating the humidifier (if present) to humidify and / or heat the generated gas flow, receiving user input from a user interface for device reconfiguration and / or user-defined operation, and outputting information to a user (e.g., on a display). The user may be a patient, medical personnel, or anyone else interested in using the device. A patient breathing conduit is coupled to the gas flow output of the flow therapy device housing and to a patient interface 51, such as a nasal cannula having a manifold and nasal prongs. The patient breathing conduit may have a heater wire 5 for heating the gas flow delivered to the patient.

[0095] High flow rates can be used as a means to enhance gas exchange and / or respiratory support by delivery of oxygen and / or other gases and by removal of CO2 from the patient's airways. High flow rates can be particularly useful before, during, or after a medical procedure.

[0096] Additional benefits of high-flow gas flow may include that it increases pressure within the patient's airways, thereby providing pressure support that opens the airways, trachea, lungs / alveoli, and bronchioles. Opening these structures enhances oxygenation and assists, to some extent, in the removal of CO2.

[0097] The increased pressure can also prevent structures such as the larynx from obstructing the view of the vocal cords during intubation. When humidified, high-flow gas flow can also prevent airway desiccation, reduce mucociliary damage, and lower the risk of laryngospasm and the risks associated with airway desiccation, such as nosebleeds, aspiration (resulting from nosebleeds), and airway obstruction, swelling, and bleeding. Another advantage of high-flow gas flow is that the flow can remove smoke generated during surgery within the airway. For example, smoke can be generated by laser and / or cauterization devices.

[0098] Referring to FIG. 1A, this embodiment may be used in any suitable situation in which a gas flow is provided to a patient from a respiratory device 10 to provide therapy (such as, but not limited to, a high flow gas flow for high flow therapy). The device 10 provides a device gas flow 11. The device gas flow 11 has a flow rate. The flow rate may be constant (i.e., does not change over time) or may be time-varying, depending on the requirements of the therapy. In these situations, the patient inhales at least a portion of the device gas flow 11 and exhales a gas flow 13, which has constituent gas components such as CO, O, nitrogen, helium, etc. The exhaled gas flow 13 may also include an anesthetic agent, such as sevoflurane.

[0099] It is useful for a medical professional to determine the exhaled patient gas flow 13 (e.g., as measured by a sensor 14) when monitoring a patient. In particular, it is useful for a medical professional to determine parameters of the constituent gas components of the patient's exhaled gas flow 13, such as the ratio (e.g., fraction) of CO or O. This helps to assess how the patient is responding to treatment, the patient's overall comfort, and / or, if the patient is undergoing a medical procedure, when the next stage of the medical procedure may begin. For example, when pre-oxygenating a patient, measuring the O fraction in the exhaled gas flow 13 helps to determine whether pre-oxygenation has been achieved. As another example, measuring the CO fraction helps to determine whether the patient is breathing. However, when device gas flow 11 is provided to a patient, it can be difficult to determine the parameters of the gas components of exhaled gas flow 13 (whether it be the O fraction, the CO fraction, or other gas parameters). This is because leakage ("leak gas flow") 12 from the device gas flow 11 from the respiratory device 10 is added to the exhaled gas flow 13 to produce a total gas outflow ("combined gas outflow") 15 from the patient, as measured, for example, by sensor 14.

[0100] "Leak gas flow" 12 includes excess gas flow from the device gas flow 11 that is not inhaled by the patient and / or does not enter the patient's lower respiratory tract, but leaks into the environment through the mouth and / or nose.

[0101] The "composite gas outflow" is the combination of leak gas flow 12 and exhaled gas flow 13. Thus, exhaled gas flow 13 is not actually measured; rather, a combined gas outflow 15 is measured, which includes the combined leak flow 12 and the patient's exhaled gas flow. Leak gas flow 12 can dilute (e.g., when measuring CO fraction) or increase (e.g., when measuring O fraction), or more generally, "alter" the gas composition of exhaled gas flow 13 measured by sensor 14, providing misleading information regarding the resulting gas composition parameters. This phenomenon is exacerbated at high flow rates, e.g., when providing high-flow therapy. Therefore, instead of measuring exhaled gas flow 13, the sensor actually measures the gas composition of combined gas outflow 15, which includes exhaled gas flow 13 and possibly at least a portion of device gas flow 11 (i.e., leak gas flow 12). The apparent reading of exhaled gas flow is inaccurate because exhaled gas flow 13 is not actually measured, but rather the combined gas outflow is measured. Note that the combined gas outflow 15 may also include other gases, such as those present in the ambient air.

[0102] The exhaled gas flow 13, the leak gas flow 12, and the combined combined gas outflow 15 can exit through the mouth, the nose, or the mouth and / or nose. Several situations exist: 1) the patient's mouth is open, and the exhaled gas flow, the leak gas flow, and therefore the combined combined gas outflow exit primarily (may include entirely) through the patient's mouth; 2) the patient's mouth is open, and the exhaled gas flow, the leak gas flow, and therefore the combined combined gas outflow exit through both the patient's mouth and nose; 3) the patient's mouth is closed, and the exhaled gas flow, the leak gas flow, and therefore the combined combined gas outflow exit through the patient's nose. If the combined gas outflow 15 is measured, this can be done by a suitable sensor positioned to measure either the flow exiting the mouth, the flow exiting the nose, or the flow exiting the nose and mouth. If the sensor measures only the flow exiting the mouth or only the flow exiting the nose, the sensor may not measure the total combined gas outflow. This is because some may exit the other orifice (e.g., the other nose or mouth, depending on which one the sensor is not measuring), in which case the sensor measurement is still relevant and / or provides a sufficient measurement of the combined gas outflow to determine the gas parameters of the exhaled gas flow.

[0103] As an example, Figure 2 shows a patient's exhaled CO fraction measurement. Figure 2 shows the true CO waveform (solid line) X and the measured diluted waveform (dotted line) X. * 1 shows an exemplary carbon dioxide signal compared to the amplitude of the device gas flow 11. In this setup, it can be seen that both the amplitude and shape of the waveform that may be displayed to the medical professional are affected by the dilution of the device gas flow 11. This information indicates to the medical professional that gas exchange is occurring, but denies the medical professional additional insight that could be gained from an accurate reading of the waveform amplitude and shape (e.g., from knowing the patient's end-tidal CO2 (the level of carbon dioxide given off by the patient at the end of exhalation)). This information may be useful to know during anesthesia procedures, such as procedural sedation, where the patient may be breathing shallowly. The actual measured waveform (which is effectively a measurement of the composite gas outflow 15) is shown by the dotted line X* However, this is a misleading waveform because the actual / true CO2 ratio (in this case, fraction) of the exhaled gas flow 13 is higher, as shown by the solid line X. The measured waveform is lower because it actually measures the CO2 fraction in the sum of the leak gas flow 12 and the exhaled gas flow 13 added together to form the combined gas outflow 15. The CO2 fraction in the exhaled gas flow is actually higher, but the measured CO2 fraction in the combined gas outflow is diluted due to the gas contribution from the leak gas flow (which has a lower CO2 fraction). In some cases, the dilution can be so significant that it can sometimes be difficult to detect the CO2 signal at all, for example, when the patient has shallow breathing and a high flow rate is provided to the patient. X * is an accurate measurement, but does not truly reflect the CO2 fraction X of the exhaled gas flow 13', but rather the CO2 fraction X in the combined gas outflow 15'. * Note that this is a measurement of

[0104] A similar situation can be envisaged in measuring the O2 fraction of the exhaled gas flow 13. If the O2 fraction of the patient's exhaled breath is less than the O2 fraction provided by the breathing apparatus, the leak gas flow 12 will increase the O2 fraction of the combined gas outflow 15, resulting in a misleading indication of the actual O2 fraction of the exhaled gas flow 13.

[0105] The present embodiment relates to a non-sealing breathing apparatus that preferably provides a high flow rate of gas to a patient. By non-sealing apparatus, we mean that a portion of the gas flow is not inhaled by the patient but rather "leaks" (leak flow 12) to the environment. The embodiment provides an apparatus and method for determining an actual exhaled gas flow 13 parameter of a desired gas component by measuring a parameter of the gas component in the combined gas outflow 15 at or near ("near") the patient, taking into account the effect of the leak gas flow 12 on the measured parameter, adjusting the measured value accordingly (or otherwise using the measured value and other information), and determining the parameter of the desired gas component in the actual exhaled gas flow 13 from the patient. The apparatus gas flow can be altered with a signature to aid in the determination of the parameter. Note that the combined gas outflow 15 can also include other gases (in addition to CO2 and O2), such as those present in ambient air. The present embodiment describes operation in the presence of such additional gases.

[0106] The respiratory device may include a flow source capable of providing a device gas flow to the patient. The device provides a time-varying device gas flow such that a time-varying parameter of the device gas flow varies over time, thereby providing a signature that can be used to assist in determining a gas parameter of the actual exhaled gas flow 13. As possible examples, the time-varying parameter of the device gas flow could be a flow rate or a gas ratio, such as a gas fraction (e.g., O fraction) and / or a gas partial pressure (e.g., O partial pressure).

[0107] In one embodiment, the flow source provides a time-varying device gas flow having a time-varying flow rate. In another embodiment, the flow source provides a time-varying device gas flow having a time-varying gas ratio (e.g., gas fraction or gas partial pressure). The flow source may be capable of providing gas flow to the patient at two or more flow rates or two or more gas ratios. The flow source may vary (e.g., vary, although not necessarily with a constant frequency) the flow rate provided to the patient, for example, between two or more flow rates or between two or more gas ratios. When varying between two or more gas ratios, preferably the flow rate is not varied by a signature flow rate, and only the therapeutic component is provided without any non-therapeutic flow rate changes being applied.

[0108] The respiratory device may include one or more sensors for measuring desired gas parameters at two or more flow rates and / or two or more gas ratios, and a controller for determining parameters of the exhaled patient gas flow 13. If a target gas, e.g., O2, is delivered to the patient, the respiratory device may include an input for controlling the concentration / fraction or partial pressure of the target gas in the delivered gas flow. The input may be manual (e.g., a dial on a flow meter) or electronic. Reference herein to a controller configured to perform a function may also refer to one or more controllers configured to perform such function, and reference to a controller should not be considered a limitation of the physical device used. A non-transitory computer-readable medium may be provided that stores a program for executing a method on a controller.

[0109] In one embodiment, a gas flow is provided to the patient at first and second gas flow rates, or a time-varying (e.g., fluctuating) flow rate (which varies continuously or discontinuously to create multiple gas flow rates) is provided (having at least first and second gas flow rates). This is the signature time-varying gas flow rate. As noted above, the time-varying gas flow may also have a therapeutic time-varying gas flow portion (as well as a signature time-varying gas flow portion). For purposes of illustration, the embodiments herein are described with reference to only the signature time-varying flow portion, but this does not exclude the possibility that the flow rate also has a therapeutic time-varying portion (or the therapeutic portion also forms the dual purpose of the signature time-varying portion). Gas parameters (of the target gas) (i.e., gas parameters of the composite gas outflow 15) are then measured at the patient at the time of the first flow rate and the time of the second flow rate (or, if varying, at the time of the first and second gas flow rates of the multiple gas flows). The first and second gas flow rates and the gas parameters measured at each time are used to determine an expiratory gas parameter (i.e., the gas parameter of the expiratory gas flow 13), for example using Equation 4. This process can then be repeated over a period of time, and the determined expiratory gas parameter can be extrapolated and presented as a signal. It should be noted that in embodiments, the gas parameter measurements can be received indirectly via input at a user interface from a user, rather than directly by the controller from a sensor.

[0110] Alternatively, in another embodiment, a gas flow is provided to the patient at first and second gas ratios (e.g., the fraction of oxygen in the device gas flow 11 can be varied), or at a varying (e.g., fluctuating) gas ratio (varied continuously or discontinuously to create multiple gas ratios). A gas parameter (of the target gas) is then measured at the patient at the time of the first gas fraction and the time of the second gas fraction (or, if varying, at the time of the first and second gas ratios of multiple gas ratios). The first and second gas fractions or varying (e.g., fluctuating) fractions are provided (having at least the first and second gas fractions). The gas parameters at the first and second fractions are then measured, and the measured gas parameters at each time are used to determine an exhaled gas parameter, e.g., using Equation 4. This process can then be repeated over a period of time, and the determined exhaled gas parameter can be extrapolated and presented as a signal. This approach is particularly suitable for gases (e.g., oxygen) commonly administered to patients. It should be noted that in embodiments, measurements of gas parameters may be received indirectly by the controller via input at a user interface from a user, rather than directly from a sensor.

[0111] Alternatively, in another embodiment, a gas flow is provided to the patient at a first and second gas ratio (e.g., the oxygen partial pressure in the device gas flow 11 can be varied). Gas parameters are then measured at the patient at a time of the first gas partial pressure and a time of the second gas partial pressure. The first and second gas partial pressures, or varying (e.g., fluctuating) partial pressures, are provided (having at least the first and second gas partial pressures). The gas parameters (of the target gas) at the first and second partial pressures are then measured, and the measured gas parameters at each time are used to determine an expiratory gas parameter, e.g., using Equation 4. This process can then be repeated over a period of time, and the determined expiratory gas parameter can be extrapolated and presented as a signal. This approach is particularly suitable for gases commonly administered to patients (e.g., oxygen). It should be noted that in embodiments, the controller can receive gas parameter measurements indirectly via input from the user at a user interface, rather than directly from a sensor.

[0112] It should be noted that "at" does not need to be exact and can mean "approximately at," and that slight time differences do not alter the validity of the measurement. It should also be noted that if the device changes the flow rate or gas ratio (e.g., gas fraction or gas partial pressure) of the gas flow, there may be a delay between the change in flow rate / gas ratio in the breathing device 10 and the new flow rate / gas ratio reaching the patient due to the distance the gas flow must travel (through the device, conduits, and patient interface). Also, if a sampling line is used to measure a gas parameter (of the target gas) at the patient, there may be a delay due to the time it takes for the sample to enter the sampling line. Thus, when referring to "at the time of the first and second flow rates," "at the time of the first and second gas fractions," "at the time of the first or second partial pressure," or the like, this means the time at which the gas flow at the first and second flow rates reaches the patient (including the sampling line, if necessary). If the delay in the change in flow rate / gas ratio within the gas flow path is not significant, the gas parameter will be measured at the patient approximately simultaneously with the change in flow rate / gas ratio. However, if there is a delay in the flow / gas ratio change propagating through the gas path, the measurement at the patient may be taken some time (i.e., after a delay) after the flow / gas ratio change occurs at the breathing device 10 to account for the time it takes for the new flow / gas ratio to reach the patient. This delay may be ascertained and / or implemented in any suitable manner, such as by experiment, modeling, measurement, calculation, etc. References herein to "at the time of" should be construed conceptually to include the time the flow / gas ratio change reaches the patient and / or any time after the flow / gas ratio change at the device due to the delay in the flow / gas ratio change reaching the patient. This comment applies to all embodiments herein.

[0113] If the target gas is CO2, the present invention can be used to monitor exhaled CO2 and / or to determine end-tidal CO2 if a high flow of gas is being provided to the patient. The CO2 trace currently displayed shows a diluted measurement. If the target gas is O2, the present embodiment can monitor exhaled O2 and / or determine the fraction of exhaled O2 (F E Measurement of O2 can be useful, for example, during the pre-oxygenation phase of a general anesthesia procedure, where the patient is pre-oxygenated to increase their O2 levels before anesthesia apnea (i.e., apnea induced by an anesthetic agent), or during procedural sedation, during the pre-oxygenation phase before sedative agents are administered and during the sedation phase when the patient is sedated and allowed to breathe shallowly. During the pre-oxygenation phase, O2 from the system gas flow 11 is taken in by the patient and contributes to the F in the exhaled gas. E O2 rises from the beginning of the preoxygenation period to the end of the preoxygenation period. F E O2 can provide medical professionals with useful information regarding the O2 level in a patient's blood, particularly in situations where it is impossible and / or impractical to obtain arterial blood gas measurements of the patient. The patient's O2 level preferably increases during the pre-oxygenation period.

[0114] The described embodiments may be applied to any other situation where it may be useful to know any end-tidal or exhaled gas fraction while a patient is receiving respiratory assistance. The invention may be used in anesthesia procedures (i.e., operating rooms), ICUs, hospital wards, emergency departments, etc.

[0115] 2. General Embodiment—Varying Device Gas Flow Rate One embodiment will now be described with reference to the diagram and graph of Figure 3A and the flow chart of Figure 5. Generally, gas parameter determination is accomplished by varying the flow rate of the system gas flow 11' (over time) in a known manner, and using knowledge of that time-varying flow rate and information obtained from the combined gas outflow 15' to determine the parameters of the desired gas components in the actual exhalation gas flow 13'. Reference number 11' is used for the varying system gas flow to distinguish it from the previously used reference number 11, which for illustrative purposes was used for the unchanged system gas flow. Similarly, when the system gas flow is varied, reference numbers for the leak gas flow 12', the exhalation gas flow 13', and the combined outflow 15' are used instead of the reference numbers 11, 12, 13, and 15 used for the same parameters when the system gas flow is unchanged.

[0116] As shown in FIG. 3A, a time-varying device gas flow 11′ is provided to the patient by the respiratory device 10. This device gas flow, having a time-varying flow rate, now includes at least two flow components. The first is a therapeutic flow component 31 according to that required by the therapy. The second is a signature (time-varying) flow component 32 that varies over time and modifies / adjusts the therapeutic flow rate to exceed and exceed that required by the therapy (including any time-varying flow that may be required for therapy) without affecting the effectiveness of the therapy provided by the device gas flow. The two components 31, 32 are summed to provide the overall time-varying device gas flow 11′. In one alternative, the device gas flow may be configured such that the varying flow rate is zero at times. The modified time-varying gas flow may be provided all the time, or optionally only during the patient's exhalation, to reduce any impact the signature may have on respiratory support. Any control may be implemented in a controller or any other suitable device. Note that this is a description of the components of the time-varying flow rate, but not necessarily how the time-varying flow rate is achieved, which can be achieved in many ways, such as those described in applicant's publications, WO 2015033288 or U.S. Patent Application Publication No. 2016 / 0193438, WO 2016157106 or U.S. Patent Application Publication No. 2018 / 0104426, WO 2017187390 or U.S. Patent Application Publication No. 16 / 096660, the entire contents of which are incorporated herein by reference.

[0117] As noted above, the therapeutic flow rate can be a constant flow rate, but it can also have a time-varying flow rate component itself (i.e., a varying gas flow rate with one or more time-varying flow rate components in addition to the signature flow). For example, as shown in FIG. 3B, the therapeutic flow rate 31′ itself includes multiple components, including a constant (e.g., bias / base) component 31A′ and a time-varying component 31B′, which sum to form a time-varying component (hereinafter, references to a varying flow rate will mean time-varying, unless expressly stated, where the context allows). This can then be added to the signature flow rate (i.e., the time-varying therapeutic flow rate 31′ is modified / adjusted by the signature flow rate 32) to create the device gas flow.

[0118] FIG. 3C is yet another example of a therapeutic flow rate 31″ having a time-varying flow rate component (this time a square wave). Also shown is a time-varying device gas flow 11 * Leads to a square wave signature flow rate of 32 inches.

[0119] The signature flow rate can, for example, simply have a flow rate that changes over time from a first flow rate to a second gas flow rate, but can alternatively have any kind of time-varying flow rate, such as a fluctuating flow rate or any other time-varying flow rate, whether periodic (regular or irregular), aperiodic, random, non-repeating, etc. There need not be a regular periodic change (e.g., it need not vary at a constant frequency, and in fact may be at a varying frequency). Nor does it need to have a fixed amplitude. For example, the signature flow rate can be in the form of a square wave, as shown in FIG. 3A. The signature flow rate can also be a step function, a sawtooth, a sine wave, or a more complex random repeating or non-repeating function, or any other option that changes over time between at least two different flow rates. Alternatively, it can be a combination of one or more waves, such as sine waves with various magnitudes and frequencies.

[0120] The signature flow component is added (modified / adjusted) to the therapeutic flow component to provide the varying device gas flow 11'. A varying flow rate, therefore, refers to any flow rate that varies at least once over time. The flow rate of the device gas flow 11' varies and includes a therapeutic flow rate (which may be constant or may itself vary and thus itself include various flow rate components) and a signature flow rate that provides an additional component for varying the therapeutic flow rate of the therapeutic gas flow. Preferably, the frequency of the signature flow rate (if repeating) or the period over which the signature flow rate varies (if not repeating) is higher than the frequency of the patient's breathing and / or higher than the frequency of any variations in the therapeutic flow rate component. This is a description of the components of the time-varying signature flow rate component, not necessarily how the time-varying flow rate component is achieved, although this is also not required. Any suitable device for varying a gas source to obtain a time-varying flow rate with the above characteristics may be implemented. For example, a time-varying flow rate can be achieved in many ways, such as those described in applicant's publications, WO 2015033288 or U.S. Patent Application Publication No. 2016 / 0193438 (e.g., Figures 56-57), WO 2016157106 or U.S. Patent Application Publication No. 2018 / 0104426, WO 2017187390, or U.S. Patent Application Publication No. 16 / 096660, the entire contents of which are incorporated herein by reference. Specific, non-limiting examples can be controllable valves and / or speed-controllable motor / impeller configurations.

[0121] As an example, FIG. 3A shows a varying flow rate of a device gas flow 11', including a therapeutically generated gas flow 31 and a time-varying (signature) component 32. The time-varying signature component is a square wave function, providing a regularly repeating, periodically varying flow rate. When a leak gas flow 12' is added to the patient's exhaled gas flow 13', this creates a composite gas outflow (total flow) 15' having the signature flow 32 as a component. See, for example, item 32 in FIG. 3A. When measuring gas parameters in the composite gas outflow (see the example of measuring CO2 fraction at the bottom of FIG. 3A), the time-varying flow rate 32 of the device gas flow 11' affects the gas parameters in the composite gas outflow 15', which becomes apparent in the measured gas parameters.

[0122] The flow rate of the apparatus gas flow 11' combined with measurements of the gas component parameters of the composite gas outflow 15' of gas outflow parameters over time is a) to determine the effect of the system gas flow on the parameters of the system gas flow 13'; and / or b) to determine the gas parameters of the actual exhaled patient gas flow 13' It can be used.

[0123] Determining a) and / or b) may be accomplished by any suitable means, such as filtering, interpolating, or extrapolating the composite gas outflow 15′ to obtain gas flow parameters for the expiratory flow, modeling gas flow parameters from the composite gas outflow 15′, or calculating or otherwise determining gas flow parameters from the composite gas outflow. Providing the signature flow rate 32 to vary the device gas flow rate 11′ changes the gas fraction (or other measured parameter) in the composite gas outflow 15′, allowing the effects of the gas fraction change to be removed directly or indirectly from the basal expiratory gas signal (expiratory gas flow 13) in a suitable manner. The change in gas fraction may be dilution or an increased fraction of gas. Interpolation, as one example, may be used to recover the waveform and values ​​of the expiratory gas. As another example, measurements of the patient gas flow rate at two time points and parameters of the gas components in the composite gas outflow at the same two time points may be used to determine parameters of the gas components in the expiratory flow. As an example, the proportion (e.g., fraction) of CO2 in the exhaled gas flow can be determined by measuring / knowing the device gas flow (flow rate) at two times and the proportion (e.g., fraction) of CO2 in the combined gas outflow at the same time. This can be performed repeatedly at other times as the device gas flow rate changes over time. Other examples are possible. As another example, as shown in FIG. 3A, the actual gas flow parameters can be extrapolated from the measurements. In one alternative, the device gas flow rate can be configured so that the changing rate is zero at times. This makes the determination easier.

[0124] An apparatus and method for achieving such gas parameter determination is described with reference to Figures 4 and 5. This apparatus may also be used for the other embodiments described herein.

[0125] FIG. 4 illustrates a respiratory device 10 for providing flow therapy or other treatment to a patient. The device is configured to deliver a time-varying device gas flow 11′ and determine parameters of a desired gas composition of an exhaled gas flow 13′. The device 10 may be based on integrated or separate components and is generally shown within a dashed box in FIG. 4 . In some configurations, the device may be a modular configuration of components. Thus, the device may be referred to as a “system,” although the terms may be used interchangeably and without limitation. Although hereafter referred to as a device, this should not be considered limiting. The device may be used to treat patients with respiratory distress, treat patients with sleep apnea, and for any suitable purpose, including preoxygenation during anesthesia procedures, anesthesia procedures, high-flow therapy, ventilation, or anywhere else monitoring of patient respiratory characteristics is required.

[0126] The device includes a flow source 50 for providing a high flow gas 31, such as oxygen or a mixture of oxygen and one or more other gases. Alternatively, the device may have connections for coupling to the flow source. Thus, the flow source may form part of the device, or may be considered separate from the device, depending on the circumstances, or even with part of the flow source forming part of the device and part of the flow source being external to the device.

[0127] The flow source may be an in-wall supply of oxygen, a tank of oxygen 50A, a tank of other gas, and / or a high-flow therapy device with a blower / flow generator 50B. While FIG. 4 shows the flow source 50 with flow generator 50B, an optional air inlet 50C, and an optional connection to an O source (such as a tank or O generator) 50A via a shut-off valve and / or regulator and / or other gas flow control 50D, this is merely one option. The description from here on can refer to either embodiment. The flow source may be one or a combination of a flow generator, O source, and air source, as described. While the flow source 50 is shown as part of the device 10, in the case of an external oxygen tank or an in-wall source, it may be considered a separate component, in which case the device would have a connection port for connecting to such a flow source. The flow source provides a (preferably high) flow rate of gas that can be delivered to the patient via a delivery conduit and patient interface 51. Depending on the end use, the patient interface 51 may be a non-sealing (also referred to as "non-sealing") interface such as a nasal interface (cannula) (e.g., when used in high-flow therapy), or a sealed interface such as a nasal mask, full-face mask, or nasal pillows (e.g., when used in CPAP). Time-varying flow rate embodiments may be used with non-sealing patient interfaces. The time-varying flow rate gas flow is not routed to or passes through a cavity external to the patient, for example, preferably through a non-sealing nasal cannula. The external cavity may introduce a low-pass filter that may attenuate the time-varying flow signature. Time-varying fractional embodiments may also be used with sealed patient interfaces. The patient interface 51 is preferably a non-sealing patient interface, which helps prevent, for example, barotrauma (e.g., tissue damage to the lungs or other organs of the respiratory tract due to pressure differentials relative to the atmosphere).The patient interface may be a nasal interface (cannula) having a manifold and nasal prongs, and / or a face mask, and / or a nasal pillows mask, and / or a nasal mask, and / or a tracheostomy interface, or any other suitable type of patient interface. The flow source may provide a therapeutic gas flow rate of, for example, about 0.5 liters / minute to about 375 liters / minute, or any range therein, or even a range including an upper or lower limit.

[0128] The time-varying device gas flow may have a therapeutic time-varying (e.g., variable) flow rate, and the controller controls the gas flow modulator to provide a therapeutic time-varying device gas flow having a variable flow rate of about 375 liters / minute to about 0 liters / minute, or preferably about 240 liters / minute to about 7.5 liters / minute, or more preferably about 120 liters / minute to about 15 liters / minute, and / or a variable flow rate having one or more frequencies of about 0.1 Hz to about 200 Hz, preferably about 0.1 Hz to about 6 Hz, more preferably about 0.5 Hz to about 4 Hz, more preferably 0.6 Hz to 3 Hz. The gas flow modulator may be a flow source (which may be a flow generator as described above, an O2 source, ambient air, etc.) and / or a valve or other device for adjusting or otherwise varying parameters of the gas flow (e.g., flow rate, gas ratio).

[0129] The variable flow rate may include a therapeutic flow rate component, where the therapeutic flow rate is from about 375 liters / minute to about 0 liters / minute, or from about 150 liters / minute to about 0 liters / minute, or preferably from about 120 liters / minute to about 15 liters / minute, or more preferably from about 90 liters / minute to about 30 liters / minute.

[0130] The variable flow rate may include a therapeutic gas flow component, and the constant (eg, bias / base) flow rate component of the therapeutic gas flow is between about 0.5 liters / minute and about 25 liters / minute.

[0131] The variable flow rate may include a therapeutic flow rate component, the therapeutic flow rate being from about 0.2 liters / minute / patient kilogram to about 2.5 liters / minute / patient kilogram, preferably from about 0.25 liters / minute / patient kilogram to about 1.75 liters / minute / patient kilogram, more preferably from about 0.3 liters / minute / patient kilogram to about 1.25 liters / minute or about 1.5 liters / minute / patient kilogram, more preferably from about 0.4 liters / minute / patient kilogram to about 0.8 liters / minute / patient kilogram.

[0132] One or more components of the time-varying (eg, fluctuating) gas flow may have one or more frequencies between about 0.3 Hz and about 4 Hz.

[0133] The variable flow rates may include at least one time-varying flow component, each variable flow rate being between about 0.05 liters / minute / patient kilogram and 2 liters / minute / patient kilogram, preferably between about 0.05 liters / minute / patient kilogram and 0.5 liters / minute / patient kilogram, preferably between about 0.12 liters / minute / patient kilogram and 0.4 liters / minute / patient kilogram, and more preferably between about 0.12 liters / minute / patient kilogram and 0.35 liters / minute / patient kilogram. Alternatively, the variable flow rates may include at least one time-varying flow component, each variable flow rate being between 0.05 liters / minute / patient kilogram and 2 liters / minute / patient kilogram, preferably between 0.1 liters / minute / patient kilogram and 1 liter / minute / patient kilogram, and more preferably between 0.2 liters / minute / patient kilogram and 0.8 liters / minute / patient kilogram.

[0134] The above are examples of therapeutic time-varying flow rates. A signature flow rate may also be provided and may be lower, the same as, or higher than the therapeutic flow rate. The frequency of the signature flow rate may be lower, the same as, or higher than the frequency of the therapeutic flow rate (if time-varying). In some embodiments, the signature flow rate has a higher frequency than the therapeutic flow rate.

[0135] As an example, the signature flow rate can be stepped between a first flow rate and a second flow rate, one or both of which can be in the range of approximately 0 LPM to 70 LPM. The maximum signature flow rate can be a therapeutic flow rate. The signature flow rate can be combined with (e.g., added to) the therapeutic flow rate or can form part or all of the therapeutic flow rate. That is, the therapeutic flow rate itself can be a signature flow rate. In some embodiments, the signature flow rate can be related to the therapeutic flow rate as a percentage. For example, the signature time-varying flow rate (adult) can be: Approximately 0% to approximately 200% of therapeutic flow rate Approximately 0% to 100% of therapeutic flow rate Approximately 100% to 200% of the therapeutic flow rate, or Approximately 50% to 150% of therapeutic flow rate Within the range and / or Approximately 0 to 140 LPM Approximately 0 to 70 LPM Approximately 70 to 140 LPM Approximately 40 to 100 LPM, or Approximately 20 to 60 LPM is within the range.

[0136] Note also that these are not limiting flows, and signature flows can be negative, but when combined with therapeutic flows will result in a positive total flow.

[0137] In some embodiments, therapeutic flows may also serve as signature flows, i.e., they serve two purposes.

[0138] The above are merely examples, and other types of time-varying flow rates can be provided, and the controller controls the gas flow modulator to provide a time-varying device gas flow having a time-varying flow rate. The device can have knowledge of the time-varying flow rate and / or can measure the time-varying flow rate provided, for example, by flow sensors (e.g., 53A, 53B).

[0139] A humidifier 52 may optionally be provided between the flow source 50 and the patient to provide humidification of the delivered gas. It may be integrated with the flow source 10 to form an integrated device 59 (see dotted line), or it may be a separate humidifier that is attachable to the flow source 10. Alternatively, the humidifier 52 may be a stand-alone humidifier having a chamber and a base, the humidifier being coupled to the flow source 10 via a conduit or other suitable means. One or more sensors 53A, 53B, 53C, 53D, or other sensors for flow rate, oxygen fraction or other gas fraction, total or partial pressure, humidity, temperature, etc. may be located throughout the device and / or at, on, or near the patient 16. Alternatively or additionally, sensors capable of obtaining such parameters may be used. Additionally or alternatively, sensors 53A-53D may be one or more physiological sensors for sensing a patient's physiological parameters, such as heart rate, oxygen saturation (e.g., pulse oximeter sensor 54E), blood oxygen partial pressure, respiratory rate, blood O2 and / or CO2 partial pressure, etc. Alternatively or additionally, any sensor capable of obtaining such parameters may be used. Other patient sensors may include an electroencephalogram (EEG) sensor, a waist band for sensing respiration, and any other suitable sensor. In some configurations, a humidifier may be optional or may be preferred due to the benefits of humidified gas in helping to maintain airway integrity. Humidification is preferably used in conjunction with high-flow gas flows to enhance patient comfort, compliance, support, and / or safety. One or more of the sensors may form part of the device or may be external to the device, with the device having inputs for any external sensors.

[0140] A sensor 14 is provided for measuring a gas parameter (of the target gas) of the patient combined gas outflow 15. That is, the sensor for detecting the gas in the combined gas outflow is selected depending on the target gas, e.g., oxygen, carbon dioxide, nitrogen, helium, and / or an anesthetic agent, such as sevoflurane. The sensor may be a mainstream or sidestream sensor and may be placed in proximity to the nose and / or mouth (in the nose and / or mouth, above the nose and / or mouth, near the nose and / or mouth). Other locations are also possible. Time-varying flow rate embodiments can operate with one gas parameter sensor, for example, when one gas parameter (e.g., fractional CO or fractional O) is measured. In time-varying flow rate embodiments, it is not necessary to measure more than one gas parameter to obtain the target parameter (e.g., measuring fractional CO and fractional O is not required to practice embodiments herein).

[0141] Output from the sensors is sent to a controller to assist in controlling the device, including, among other things, varying the gas flow. Alternatively or additionally, input can come from the user. The controller is coupled to the flow source, the humidifier, and the sensors. The controller controls these and other aspects of the device, described below. The controller can operate the flow source to provide the delivered gas flow. The controller can also operate the gas flow modulator (including the flow source) based on feedback from the sensors, or optionally without feedback (e.g., using default settings), to control the flow, pressure, volume, and / or other parameters of the gas provided by the flow source. The controller can also control any other appropriate parameters of the flow source to meet oxygenation requirements and / or for CO2 removal. The controller 19 can also control the humidifier 52 based on feedback from sensors 53A-53D, 14. Using inputs from the sensors, the controller can determine oxygenation requirements and provide information to a medical professional (who can control the components of the respiratory apparatus to provide the desired therapy, e.g., flow rate, O2 fraction, humidity, etc.) and / or control parameters of the flow source, gas flow modulator, and / or humidifier, as needed. Alternatively, embodiments may be provided as a stand-alone monitoring device independent of the respiratory apparatus that communicates with and controls components of the respiratory apparatus to provide information to a medical professional and / or provide the desired therapy. The medical professional can then control the respiratory apparatus to provide the desired therapy. Thus, the controller may not necessarily determine oxygenation requirements and control device parameters.

[0142] The controller 19 is also configured to operate the device so that the device gas flow has a time-varying flow rate that provides therapy, and also a signature flow rate as described. The controller 19 can do this by any suitable means, such as a controlled flow generator 50B or any other suitable gas modulator. The gas modulator can be used to regulate (i.e., change, modify, adjust, or otherwise control) the parameters of the gas flow. Each gas flow modulator can be located within the flow source, after the flow source and before the humidifier, after the humidifier, and / or at any other suitable location within the device to regulate the gas flow path (and the flow source itself can be a gas flow modulator). The controller can also operate the gas flow modulator (including the flow source) based on feedback from sensors, or optionally without feedback (e.g., using default settings), to control the flow, pressure, volume, and / or other parameters of the gas provided by the flow source. The controller can also control any other suitable parameters of the flow source to meet oxygenation requirements. The gas modulator may be, for example, one described in International Publication No. WO 2017 / 187390 or U.S. Patent Application Publication No. 16 / 096660, the entire contents of which are incorporated herein by reference.

[0143] The controller can then measure the combined gas outflow and determine the gas parameters using any of the following techniques:

[0144] With respect to other embodiments below relating to varying gas ratios, the controller 19 may additionally or alternatively be configured to operate the device such that the device gas flow has a time-varying gas ratio (such as O fraction or other gas fraction and / or O partial pressure) that provides therapy / respiratory assistance, as described, and also a signature gas ratio (such as gas fraction and / or gas partial pressure). The controller 19 may do this by any suitable means, such as by controlling a proportional valve coupled to an O source 50A or any other means previously described in other patents. The controller may then measure the combined gas outflow and / or determine gas parameters (e.g., obtain estimates of gas parameters) using any of the following techniques: In one embodiment, there are two proportional valves operating 180 degrees out of phase. When one opens, the other closes. One controls the O fraction in the device gas flow and the other controls the air fraction in the gas flow, but together maintain a constant total gas flow rate. In another alternative, a single proportional valve is used with the impeller, where the proportional valve controls the O fraction and the impeller controls the flow rate. In some embodiments, a single proportional valve may be used before or after the impeller. If a single proportional valve is used before the impeller, the proportional valve controls the O fraction entering the impeller inlet along with ambient air. In some embodiments, more than one proportional valve may be used with the impeller and may be located anywhere in the system relative to the impeller. The controller 19 can control the proportional valves to operate as needed to achieve time-varying gas ratios as described herein.

[0145] An input / output interface 54 (such as a display and / or input devices) is provided for receiving information from a user (e.g., a clinician or patient) that can be used to determine, for example, oxygenation requirements, anesthetic gas agents, sensing, flow rates, gas fractions, partial pressures, and / or any other parameters that may be controlled by the device.

[0146] The device may also be operated to determine a patient's dose / oxygenation requirements (hereinafter "oxygen requirements") for / in connection with general anesthesia (i.e., pre-anesthesia oxygen requirements during a pre-oxygenation period, and / or oxygen requirements during anesthesia, which may include when the patient is apneic or when the patient is breathing), as well as after such a procedure, which may include an extubation period. The device 10 is also configured to regulate and provide high flow gas to the patient for an anesthesia procedure, and to regulate parameters (pressure, flow rate, gas volume, gas composition, etc.) of the high flow gas delivered to the patient as needed to meet the oxygenation requirements. The device also includes a display for displaying measured values ​​of the gas parameters of the exhaled gas flow, which may be part of the input and output, as a graph, digital display, or any other suitable means.

[0147] FIG. 5 illustrates a method of operating a respiratory apparatus 10 having a sensor 14 and controller 19 as described above. The following steps may be performed: A time-varying device gas flow 11′ is generated and provided to the patient, the time-varying device gas flow 11′ includes a time-varying flow rate having a signature. In one variation, the time-varying flow rate includes at least a therapeutic flow rate component 31. The therapeutic gas flow rate is modified / adjusted by (e.g., in this case, by adding) a signature gas flow rate component 32 that varies over time to generate a device gas flow 11′ having a time-varying flow rate with at least a second flow rate (at a later time, e.g., 11b′) that differs from a first flow rate (at an earlier time, e.g., 11a′). This may be a simple step change, or, as described above, may be a more complex time-varying flow rate waveform, such as a square wave, a sine wave, or any other wave described or contemplated herein. The “modified” device gas flow 11′ is provided to the patient. A first flow rate 11a' of the device gas flow 11' is provided to the patient (step 40), and a second flow rate 11b' of the device gas flow 11' is provided to the patient some time later (step 42). The flow rates are preferably known, or alternatively, are measured. Simultaneously, the respiratory apparatus 10 monitors over time a combined gas outflow 15', which is a combination of the leak gas flow 12' (having a time-varying flow rate) and the exhaled gas flow 13'. This involves measuring at least a first parameter (in this case, CO2 fraction) of the first flow rate 11a' of the combined gas outflow 15' and relating it to the provided first flow rate 11a' some time later (step 41), and later measuring the same gas parameter (CO2 fraction) of the combined gas outflow of the second gas flow 11b' (step 43).

[0148] The apparatus 10 can compensate for the delay in providing the first flow rate and the measurement of the first parameter 11a' in the composite gas outflow 15' affected by the first flow rate, for example, in the case of sidestream sampling, a correction of "X" seconds can be applied.

[0149] Parameters of the combined gas outflow 15" are measured at or near ("near") the patient's mouth and / or nose using sensor 14. In some embodiments, only one gas parameter (the target gas parameter of interest) needs to be measured. Gas parameters in the exhalation gas flow 13' are then determined (step 44) using the (preferably known, but optionally measured) first and second gas flow rates and the gas parameters measured at the first and second time points. In some embodiments, the first or second flow rate is 0 L / min. In some embodiments for adults, the first and second flow rates are about 0 L / min or greater, preferably about or greater than about 20 L / min, and more preferably between about 20 L / min and about 90 L / min. In some embodiments for premature infants / children (with body mass ranging from about 1 to about 30 kg), the therapeutic flow may be set at 0.4-0.8 L / min / kg, with a minimum of about 0.5 L / min and a maximum of about 25 L / min. For patients weighing less than 2 kg, the maximum flow is set at 8 L / min. Variable flow is set at 0.05-2 L / min / kg, with a preferred range of 0.1-1 L / min / kg, and another preferred range of 0.2-0.8 L / min / kg.

[0150] Steps 40-44 can be repeated continuously / periodically to determine gas parameters of exhaled gas flow 13' over time as device gas flow 11' varies its flow rates 11a', 11b' over time due to the varying signature 32 flow rates (step 45). During the exhalation phase of the patient's breath, parameters of the gas components in composite gas outflow 15' can be measured. While the first gas flow rate 11a' and the second gas flow rate 11b' in device gas flow 11' can simply be used, in practice, signature gas flow 32 tends to vary continuously or at least periodically / discontinuously over time, and composite gas outflow 15' can be measured continuously or periodically (e.g., at a sampling rate) to obtain continuous or periodic measurements of exhaled gas flow parameters, which can then be displayed via a graph or display to provide real-time measurements of the exhaled gas flow parameters.

[0151] As described in the summary above, various hardware configurations and methods of operation are capable of implementing the present invention, examples of which, without limitation, are described below.

[0152] 3. Exemplary Embodiment - Varying Device Gas Flow Rate An exemplary embodiment will now be described with reference to Figures 1-5, using the devices and control methods described above. Any control method may be implemented in the controller or any other suitable device. In this embodiment, a medical professional wishes to monitor exhaled CO2 or O2 or an anesthetic agent such as sevoflurane. Measurements of exhaled gas fractions can be used by the medical professional to perform various monitoring functions, including ensuring that gas exchange is occurring within the patient. For example, the exhaled oxygen fraction (F E Fraction of exhaled carbon dioxide (F O2) may be measured to assess the effectiveness of pre-anesthetic pre-oxygenation. E CO2) is an indicator of gas exchange. E Monitoring CO2 is recommended or required by some anesthesia standards. However, as noted above, monitoring FeCO2 and / or FeO2 can be difficult when gas flow is provided to a patient, especially when the gas flow is provided at a high flow rate (as described below). This embodiment addresses this challenge. The embodiment uses a non-occlusive breathing apparatus, for example, with a non-occlusive nasal cannula.

[0153] Nasal high flow (NHF) is typically used to provide respiratory assistance via a non-sealing nasal interface (cannula), such as that shown in FIG. 4. The device may include a CO2 sampler (sensor 14), such as those described in International Publication No. WO 2018070885 or U.S. Patent Application Publication No. 16 / 341767, the entire contents of which are incorporated herein by reference. The nasal cannula includes prongs configured for insertion into the patient's nares during use. The prongs are sized to provide a gap between the prongs and the walls of the patient's nostrils so that the prongs do not seal against the patient's nares. This may, for example, allow for entrainment of ambient gases into the patient's airways in certain circumstances and / or allow exhaled gases to flow around the prongs and out into the environment.

[0154] A sampler is an attachment to a nasal high-flow interface (cannula) that allows for measurement of exhaled gases, such as carbon dioxide. During use, exhaled gases are transported (actively or passively) through a sampling line to a measurement device. While this is sidestream sampling, the embodiments described herein may also be implemented for mainstream sampling, where a CO2 sensor is located in the main flow path. The sampler may also be adapted to deliver and / or sample other exhaled gases, such as O2. The portion of the sampler that captures a portion of the exhaled gas for sampling may be operable between the patient's nose and mouth.

[0155] Leak gas flow 12' from device 10 alters the gas fractions in combined gas outflow 15' (by diluting or increasing the gas fractions). As previously mentioned, reliable measurement of the fraction of exhaled carbon dioxide and / or oxygen in exhaled gas flow 13' at high flow rates is difficult. For example, in the case of preoxygenation, where the fraction of inspired oxygen is typically 1, oxygen from a high-flow device provides an artificially high value, limiting the clinical usefulness of the measurement. The exhaled oxygen fraction provides insight into the effectiveness of preoxygenation, e.g., whether preoxygenation is sufficient and the fraction of oxygen in the patient's lungs is at a level sufficient to provide the desired safe apnea time in the procedure.

[0156] Please note that the following relates to safe apnea duration according to International Publication No. WO 2018 / 185714 or U.S. Patent Application Publication No. 16 / 500329, both of which are incorporated herein in their entirety. A safe apnea duration is defined as the time it takes for a patient to reach a specified oxygen saturation level. Typically, this oxygen saturation level may be 88-90%, preferably 90-92%, although this level may vary depending on the patient and the procedure being performed. Saturations below this level can rapidly drop to dangerous levels (<70%, preferably <80%) on the steep section of the oxyhemoglobin dissociation curve, posing a significant risk to the patient. Alternatively, a safe apnea duration may be defined as the time it takes for a patient to reach a specified level of arterial CO2.

[0157] An objective of the embodiments is to accurately measure and display the waveform and amplitude of exhaled gas in the presence of nasal high flow (NHF) by using a variable flow or a flow that steps between at least two different flow rates.

[0158] The device is operated to provide a device gas flow 11' having a time-varying flow rate, having a therapeutic flow rate component 31 and a signature (time-varying) flow rate component 32, as described above. Preferably, this is a high flow rate (with a therapeutic component) as defined, and more preferably, between 20 and 90 liters per minute. In this example, a constant therapeutic flow rate 31 is provided and added to a square wave signature flow rate component 32 to generate a device gas flow 11' having a time-varying flow rate, as shown in FIG. 3A. In some embodiments, the signature flow rate component 32 can be added to the constant therapeutic flow rate component 31 to generate a device gas flow 11' having a time-varying flow rate, as shown in FIG. 3A. The controller 19 or a user operates the flow source 10 to provide the device gas flow 11' having a flow rate. The controller 19 may be programmed with a desired device gas flow 11' having a varying flow rate, and generates the varying flow rate to provide the required variation in flow rate over time. Other methods of varying the flow rate are also possible, such as those described in International Publication No. WO2018070885 or U.S. Patent Application Publication No. 16 / 341767, the entire contents of which are incorporated herein by reference.

[0159] During use, the patient inhales device gas flow 11' and exhales gas flow 13'. Exhaled gas flow 13' (with a CO2 fraction) is combined with leak gas flow 12' to produce a combined gas outflow 15' (with a diluted CO2 fraction) as shown in Figure 3A.

[0160] Sensor 14 measures the diluted CO (or O in other variations) fraction in the combined gas outflow and passes this information to the controller. The output of the sensor measuring a parameter of combined gas outflow 15' is shown as waveform 15' in Figure 3A. The controller must then process that output to determine the actual CO (or O) fraction in the expired patient gas flow.

[0161] Fraction of exhaled gas components, e.g., CO2, as a percentage of total exhaled gas per volume (i.e., FE CO 2) (or O2- i.e. F E O2) can be determined from the combined gas outflow using a formula that uses knowledge of the change in flow rate of the time-varying device gas flow. This determination can be made based on the premise that the fractions (components) of exhaled gas can be determined from known / measured quantities.

[0162] F m (t), the volume fraction of the gas components measured in the patient combined gas outflow 15' from the patient at time t (this is the measured CO2 / O2 fraction parameter of the combined gas outflow 15', preferably measured by sensor 14).

[0163] F m (t) is preferably measured at the patient's mouth when the patient's mouth is open or at the nose when the patient's mouth is closed.

[0164] Q o (t), the flow rate of the system gas flow 11′ provided to the patient from the breathing apparatus (system gas flow rate) at time t.

[0165] F m (t+Δt), the volume fraction of the gas components measured in the patient combined gas outflow 15′ at time t+Δt (this is preferably the measured CO2 / O2 fraction parameter of the combined gas outflow, measured by sensor 14). F m (t+Δt) is preferably measured at the patient's mouth when the patient's mouth is open or at the nose when the patient's mouth is closed.

[0166] Q o (t+Δt), the flow rate of the system gas flow 11′ provided to the patient from the breathing apparatus (system gas flow rate) at time t+Δt.

[0167] F o (t), the volume fraction of the gas component in the system gas flow 11′ coming from the breathing system at times t and t+Δt.

[0168] Fo (t+Δt), the volume fraction of the gas component in the apparatus gas flow 11′ coming from the breathing apparatus at time t+Δt.

[0169] Formula (4)

number

[0170] The CO2 (or O2) fraction in the combined gas outflow 15' is measured by sensor 14, and the flow rate of device gas outflow 11' is known (or can be measured). Thus, by measuring the CO2 (or O2) fraction in the combined gas outflow 15' using sensor 14 at two (or more) different times, and by knowing / measuring the CO2 (or O2) fraction and the flow rate of device gas outflow 11' at two (or more) different times, the CO2 (or O2) fraction in exhalation gas flow 13' can be determined using equation (4).

[0171] When measuring CO2 or any other gas component exhaled by the patient and not delivered to the patient by a high flow device, Equation 4 can be simplified: CO2, F o (t)=F o For the measurement of (t+Δt)~0, equation (4) becomes

number

[0172] In practice, the CO2 (or O2) fraction is measured continuously or periodically to obtain a real-time output, which can then be used in combination with knowledge / measurements of the device gas flow 11', also continuously or periodically sampled, to determine the real-time CO2 (or O2) fraction of the exhaled gas flow. This can be output as a graph, digital display, or the like on a display. In practice, the flow rate is varied continuously or discontinuously, but periodically or regularly, over a period of time to provide multiple data points. Thus, by varying the flow rate at least once, the difference between the first flow rate 11a' and the second flow rate 11b' can be used. Thus, the controller measures the gas parameter at appropriate times and then calculates F for each measurement. E Calculate.

[0173] The obtained F E CO2 can restore the carbon dioxide waveform seen in Figure 2.

[0174] 4. Mathematical derivation of equations (4) and (5) Equations (4) and (5) are derived as follows.

[0175] Assuming that all or most of the gas exhaled by the patient exits through the mouth, the volume fraction of gas (F) measured as a function of time at the patient's mouth is delivered to the nasal high flow. m )teeth,

number

[0176] The flow is illustrated with reference to a patient in FIG.

[0177] Equation (1) is based on the unknown quantities k and Q E can be rearranged to find the ratio of

number

[0178] For two samples taken at times t and t+Δt, the time between the samples, Δt, is the fraction of the (expired) gas component (volume fraction F of the gas component measured in the patient composite gas outflow 15′) during the patient's expiratory phase. m ), patient's expiratory gas flow rate (Q E ), and is short enough that the rate of device gas flow out the port (k) can be assumed to be approximately constant and can therefore be approximated as:

number

number

number

[0179] This formula can be used to determine exhaled gas flow 13' parameters such as fractions of exhaled oxygen, carbon dioxide, nitrogen, helium, and / or anesthetic agents such as sevoflurane.

[0180] In some configurations, the parameters of the gas flow components in the exhalation gas flow 13′ (F E A correction or compensation can be applied to equation (4) to obtain a better estimate of ( ). For example, a correction or compensation can be applied to equation (4) to account for the fact that the assumption that the ratio of the combined gas outflow and the device gas flow out of the port is approximately constant is not true. Such a correction or compensation can take into account the ratio of the port flow to the patient interface flow as a function of the patient interface flow, for example, as described in applicant's publications WO 2017187391 or U.S. Patent Application Publication No. 2019 / 0150831, the entire contents of which are incorporated herein by reference.

[0181] CO2, F o (t)=F o For the measurement of (t+Δt)~0, equation (4) becomes

number

[0182] The above is a known / measured quantity, F m (t), Q o (t), F m (t+Δt), Q o The equations for oxygen and carbon dioxide in terms of (t+Δt) are given by F E CO2 can restore the carbon dioxide waveform seen in Figure 2.

[0183] In summary, but not by way of limitation, the device is operated (preferably within each breath) to vary the flow administered through a patient interface, preferably a non-sealing nasal interface (cannula). Doing so changes the gas fraction, allowing the effects of the gas fraction changes to be removed from the baseline expiratory gas signal. Interpolation can be used to recover the waveforms and values ​​of the desired gas components in the patient's expiratory gas flow.

[0184] The frequency at which the flow is varied is configured to achieve the results of the present invention. E , k, and F E The oscillation frequency must be fast enough so that the assumption regarding the frequency of the oscillation is maintained, and fast enough so that interpolation can be performed between samples to fully recover the waveform. The actual frequency required depends on the patient's respiratory frequency, but is typically in the range of 1 to 100 Hz. The oscillation frequency is preferably higher than the patient's respiratory frequency or the average patient's respiratory frequency (depending on whether the patient is an adult or an infant). In one embodiment, the frequency may be approximately 5 Hz. In one possible embodiment, the controller can receive input regarding the patient's respiratory frequency (e.g., directly via a sensor or indirectly, e.g., via a person reading the sensor). The controller can determine an appropriate oscillation frequency from that input. In another possible embodiment, the controller can receive input from a user regarding an oscillation frequency based on the patient's known respiratory frequency and / or the patient's respiratory frequency, and the controller can determine an appropriate oscillation frequency from that input.

[0185] Referring to Figure 3A, if a continuous sinusoidal flow waveform (instead of stepping between flows) is used in the device, this can allow for lower frequency fluctuations. In the above embodiment, each time step of the flow allows for the collection of a data point. In the sinusoidal flow embodiment, each time the sine wave causes a measurable difference in CO2 output, another data point can be collected by the device. This fluctuating sinusoidal embodiment also has a good signal-to-noise ratio.

[0186] An exemplary situation using this method involves procedural sedation, where the patient is able to breathe shallowly. In this situation, the flow can be varied or otherwise changed (e.g., continuously or repeatedly stepped) over a period of time, for example, from a flow rate of approximately 70 LPM to 40 LPM (which may look like the flow in FIG. 3A). If repeatedly stepped, the flow rate at each step can be a single step change in flow rate or a continuous / discontinuous change in various flow rates from one flow rate to another. The fraction of exhaled carbon dioxide (or oxygen) can then be measured at the patient's mouth during high-flow therapy at approximately 70 LPM, and then again at approximately 40 LPM. This measurement is repeated as the flow is continuously stepped up and down. This is a diluted measurement in the context of determining the fraction of CO2. The two flow rates (approximately 70 and approximately 40 LPM) and the fraction of exhaled CO2 at these flow rates can be used to calculate the undiluted fraction of exhaled CO2 in Equation 5. This process is repeated over this time period, and the undiluted CO measurements can be interpolated and presented to show the patient's exhaled CO trace, which may look like the true waveform of FIG. 2. This exhaled CO trace, and the end-tidal CO value that can be inferred or determined from the exhaled CO trace, are useful during procedural sedation because the end-tidal CO value can provide an indication of CO levels in a patient who may be shallowly breathing and therefore have higher CO than expected. In this situation, a diluted waveform, which only provides an indication of gas exchange, does not accurately provide this indication.

[0187] 5. General Embodiment - Varying Device Gas Flow Gas Fraction An alternative embodiment using time-varying gas fractions in the device gas flow will now be described with reference to the device described above. This is an example of a time-varying gas ratio. Any control method can be implemented in the controller or any other suitable device.

[0188] One embodiment will now be described with reference to the diagram and graph of FIG. 6A and the flow diagram of FIG. 7. Generally, parameter determination is accomplished by varying the gas fraction of the system gas flow 11" (over time) in a known manner and using knowledge of the time-varying gas fraction and information obtained from the combined gas outflow 15" to determine the desired gas component parameters in the actual exhalation gas flow 13". Reference numeral 11" is used for a varying system gas flow with varying gas fraction to distinguish it from the previously used reference numeral 11, which was used for a stationary system gas flow, and reference numeral 11', which was used for a varying flow rate gas flow. Similarly, when the system gas flow is varied, reference numerals for leak gas flow 12", exhalation gas flow 13", and combined gas outflow 15" are used instead of 11, 12, 13, 15, which are used for the same parameters but when the system gas flow is unchanged.

[0189] In this embodiment, the gas fraction determined is the CO fraction. However, this is used merely as an example and should not be considered limiting. Alternatively, O could be the gas fraction determined, and the same approach could be taken. However, in this embodiment, if the gas fraction in the device gas flow 11" is time-varying, it is the same gas that must be measured in the combined gas outflow 15". Because O (and not CO) is provided by the device gas flow 11", it is the O fraction that time-varys in the device gas flow 11" and, therefore, it is the O fraction that is measured in the combined gas outflow 15". However, because CO fraction is the desired gas parameter of interest, it is derived from the measured O fraction, as described below. The modified time-varying gas flow may be provided all the time, or optionally only during the patient's exhalation, to reduce any impact the signature may have on respiratory support.

[0190] As shown in FIG. 6A, a device gas flow 11″ having a time-varying gas fraction (preferably an O fraction, but other provided gases may also be effective) is provided to the patient by respiratory apparatus 10. This device gas flow with time-varying gas fraction here includes at least two gas fraction components. The first is a therapeutic gas fraction component 61 according to what is needed for therapy. The second is a signature (time-varying) gas fraction 62 component that varies over time and modifies / adjusts the therapeutic gas fraction in a manner that exceeds and exceeds what is needed for therapy (including any time variations in gas fraction that may be needed for therapy), but cannot affect the effectiveness of the therapy provided by the device gas flow. The two components are summed to provide an overall time-varying device gas flow gas fraction 11″. This is a description of the components of the time-varying gas fraction, but not necessarily a description of how the time-varying gas fraction is achieved. Any suitable device for varying the gas source to obtain a time-varying gas fraction with the above characteristics can be implemented.

[0191] In one embodiment, there are two proportional valves operating 180 degrees out of phase. When one opens, the other closes. One controls the O2 fraction in the system gas flow and the other controls the air fraction in the gas flow, but together maintain a constant total gas flow. In another alternative, a single proportional valve is used with an impeller, where the proportional valve controls the O2 fraction and the impeller controls the flow rate.

[0192] In some embodiments, a single proportional valve may be used before or after the impeller. If a single proportional valve is used before the impeller, the proportional valve controls the O fraction entering the inlet of the impeller along with ambient air. In some embodiments, more than one proportional valve may be used with an impeller and may be located anywhere in the system relative to the impeller. The controller 19 can control the proportional valves to operate as needed to achieve time-varying gas ratios as described herein.

[0193] As noted above, the therapeutic gas fraction may be a constant gas fraction, but it may also have a time-varying gas fraction component itself (i.e., a varying gas flow fraction with various time-varying fraction components). For example, as shown in FIG. 6B, the therapeutic gas fraction itself includes multiple components 31″, including a constant (e.g., bias) component and a time-varying component, which sum to form a time-varying component. (Hereinafter, reference to a varying gas fraction will mean time-varying, unless expressly stated, where the context allows.) This can then be added to the signature gas fraction 62 (i.e., the time-varying therapeutic fraction 61′ is modified / adjusted by the signature gas fraction 62) to create the device gas flow 11″. The device gas flow with a time-varying gas fraction component 11″ may preferably have a non-varying flow rate.

[0194] FIG. 6C is yet another example of a therapeutic gas flow 61″ having a time-varying gas fraction component, this time a square wave. (Therapeutic gas flows can also have time-varying fractions as shown in FIG. 3B and as described above.) Also shown is a time-varying device gas flow 11 ** The square wave signature gas fraction is 62''.

[0195] The signature gas fraction may simply have a time-varying gas fraction, for example, from a first gas fraction to a second gas fraction, but may alternatively have any type of time-varying gas fraction, such as a fluctuating gas fraction or any other time-varying gas fraction, whether periodic (regular or irregular), aperiodic, random, non-repeating, etc. For example, the signature gas fraction may be in the form of a square wave, as shown in FIG. 6A. The signature gas fraction may also be a step function, a sawtooth, a sine wave, or a more complex random repeating or non-repeating function, or any other option for time-varying between at least two different gas fractions. The signature gas fraction component is added (modified / adjusted) to the therapeutic gas fraction component to provide a varying device gas fraction. Alternatively, it may be a combination of one or more waves, such as sine waves with various magnitudes and frequencies. Thus, a varying gas fraction refers to any gas fraction that changes at least once over time. The gas fraction of the device gas flow varies and includes a therapeutic gas fraction (which may be constant or may itself vary and thus itself comprise various gas fraction components) and a signature gas fraction that provides additional components for varying the therapeutic gas fraction of the therapeutic gas flow. Preferably, the frequency of the signature gas fraction (if repeating) or the period over which the signature gas fraction frequency varies (if not repeating) is higher than the frequency of the patient's breathing ("breathing frequency") and / or higher than the frequency of any variations in the therapeutic gas fraction components. However, this is not required. Again, this is a description of the components of the time-varying signature gas fraction components, but not necessarily a description of how the time-varying gas fraction components are achieved. This can be achieved in many ways, such as those described above with respect to varying flow rates.

[0196] As an example, FIG. 6A shows the varying gas fraction of a system gas flow, including a therapeutically generated gas fraction 61 and a time-varying (signature) component 62. The time-varying signature component is a square wave function, providing a regularly repeating, periodic gas fraction. When leak gas flow 12″ is added to the patient's exhaled gas flow 13″, this creates a composite gas outflow 15″ having signature gas component 62 as a component. See, for example, FIG. 3A. When measuring a gas parameter in the composite gas outflow (see the bottom of FIG. 6A), the time-varying gas fraction of system gas flow 11″ affects the gas parameter in the composite gas outflow 15″ and becomes apparent in the measured gas parameter. In this case, the measured gas fraction in the composite gas outflow 15″ is O2, so the bottom graph of FIG. 6A shows O2 fraction versus time.

[0197] The time varying component 62 of the gas fraction of the device gas flow 11'' combined with the time-dependent measurements of the gas component parameters of the patient composite gas outflow 15'' composite gas outflow parameter is: a) to determine the effect of device gas flow on the parameters of exhaled gas flow 13'', and / or b) It can be used to determine gas parameters of the actual exhaled gas flow 13'', in which case the O proportion (in this case the O fraction) in the exhaled gas flow 13'' is estimated, and then from that the CO proportion (in this case the CO gas fraction) in the exhaled gas flow 13'' is determined.

[0198] Determining a) and / or b) is accomplished by any suitable means, such as filtering, interpolating, or extrapolating the composite gas outflow 15″ to obtain a gas flow parameter of the exhalation flow (i.e., O fraction in this example), modeling a gas flow parameter from the patient gas outflow 15″, or calculating or otherwise determining a gas flow parameter from the composite gas outflow. Providing a signature gas fraction 62 to vary the device gas flow gas fraction 11″ changes the gas fraction (or other measured parameter) in the composite gas outflow 15″, allowing the effects of the gas fraction variation to be removed directly or indirectly from the basal exhalation gas signal (exhalation gas flow 13″) in a suitable manner. Interpolation, as one example, may be used to recover the waveform and values ​​of the exhaled gases. As another example, measurements of the device gas flow gas fraction 11″ at two time points and parameters of the gas fraction components in the composite gas outflow 15″ at the same two time points may be used to determine parameters of the gas components in the exhalation flow. As an example, the proportion of O in the exhaled gas flow 13'' can be determined by measuring / knowing the O fraction in the device gas flow at two times and the O fraction in the combined gas outflow at the same times. This can be done repeatedly at other times as the device gas flow O fraction changes over time. Other examples are possible. As another example, as shown in FIG. 6A, the actual gas flow parameter (O fraction) can be extrapolated from the measured value. The CO gas fraction in the exhaled gas flow 13'' can be determined from the O fraction in the exhaled gas flow 13'' in a manner described below.

[0199] An apparatus and method for accomplishing such a determination will be described with reference to Figures 4 and 7. This apparatus was described above in connection with Figure 4 and need not be described again. However, for clarity, the apparatus controller can operate the apparatus to control the oxygen fraction of the apparatus gas flow 13''. The controller can do this in any suitable manner by operating the flow controller, the O2 source, the air source, and any valves, motors, modulators, or other devices that can be used to control the oxygen fraction.

[0200] FIG. 7 illustrates a method of operating a respiratory apparatus 10 having a sensor 14 and controller 19 as described above. The following steps may occur: A time-varying device gas flow 11″ is provided to the patient, including a time-varying gas fraction (in this case, O fraction) having a signature. In one variation, the time-varying fraction includes at least a therapeutic gas fraction (O) component 61. The therapeutic gas fraction is modified / adjusted by (e.g., in this case, by adding) a signature gas fraction component 62 that varies over time to produce a device gas flow 11″ having a time-varying gas fraction having at least a second gas fraction (at a later time, e.g., 11b″) that differs from a first gas fraction (at an earlier time, e.g., 11a″). This may be a simple step change, as in FIG. 6A, or, as described above, may be a more complex time-varying gas fraction waveform, such as a square wave, sine wave, or any other wave described or contemplated herein. The “modified” device gas flow 11″ is provided to the patient. A first gas fraction 11a'' of the device gas flow 11'' is provided to the patient (step 70), and a second gas fraction 11b'' of the device gas flow 11'' is provided to the patient some time later (step 72). The gas fractions are preferably known, or alternatively, are measured. Simultaneously, the respiratory apparatus 10 monitors a combined gas outflow 15'' over time, which is a combination of the leak gas flow 12'' (with its time-varying gas fraction) and the exhaled gas flow 13''. This involves measuring at least a first parameter (in this case, O fraction) of the first gas fraction 11a'' of the combined gas outflow at a time and relating it to the provided first gas fraction 11a'' some time later (step 71), and later measuring the same gas parameter (O fraction) of the combined gas outflow 15'' of the second gas fraction 11b'' (step 73).

[0201] The apparatus 10 can compensate for the delay in providing the first gas fraction 11a'' and the measurement of the first parameter in the composite gas outflow 15'' affected by the first gas fraction, for example, in the case of sidestream sampling, a correction of ``X'' seconds can be applied.

[0202] A parameter (O gas fraction) of the combined gas outflow 15" is measured at or near ("near") the patient's mouth and / or nose using sensor 14. Only one gas parameter (the target gas parameter of interest) needs to be measured. The gas parameter (O fraction) in the exhaled gas flow 13" is then determined (step 74) using the (preferably known, but optionally measured) first and second gas fractions (e.g., O fraction) of the device gas flow 11" and the first and second measured gas parameters (e.g., O fraction) of the combined gas outflow 15" at the first and second time points. As described below, the CO gas fraction in the exhaled gas flow 13" can then be derived from the O fraction of the exhaled gas flow 13".

[0203] Steps 70-74 can be repeated continuously / periodically to obtain measurements of the gas parameter (O fraction) of the exhaled gas flow 13' over time as the device gas flow 11'' changes its gas fractions 11a'', 11b'' over time due to the changing signature gas fraction 62 (step 75). During the exhalation phase of the patient's breath, parameters of the gas components in the composite gas outflow 15'' can be measured. While the first gas fraction 11a'' and the second gas fraction 11b'' in the device gas flow 11'' may simply be used, in practice, the signature gas fraction 62 will likely change continuously or at least periodically / discontinuously over time, and the composite gas outflow 15'' can be measured continuously or periodically (e.g., at a sampling rate) to obtain continuous or periodic measurements of the exhaled gas flow parameter, which can then be displayed via a graph or display to provide a real-time measurement of the exhaled gas flow parameter.

[0204] This embodiment may be particularly useful in the described pre-oxygenation situation where the patient appears to be breathing spontaneously. Varying the oxygen fraction rather than the flow rate may be more comfortable for the patient if they are conscious and / or awake.

[0205] The controller may also use a phase locked loop to synchronize the phase of the varying gas flow and the measured gas parameter.

[0206] 6. Exemplary Embodiment - Varying Device Gas Flow Gas Fraction Referring now to the figures, one exemplary embodiment will be described using the device and control method described above. As with the variable device gas flow rate embodiment, in this embodiment, a medical professional desires to monitor exhaled CO, O, nitrogen, helium, and / or an anesthetic agent such as sevoflurane. The description of the purpose and configuration of the device according to that embodiment (exemplary embodiment - variable device gas flow rate) applies here as well. This embodiment uses a flow rate without a time-varying signature. The flow rate may be a set rate that does not vary. Any control method may be implemented in a controller or any other suitable device.

[0207] For illustrative purposes, the gas fractions to be determined are O and / or CO fractions. However, this is used merely as an example and should not be considered limiting. Alternatively, other gases, such as nitrogen, helium, and / or anesthetics such as sevoflurane, may be the target gas. In such cases, another suitable sensor for detecting the target gas in the combined gas outflow, i.e., a suitable sensor for detecting nitrogen, helium, and / or anesthetics such as sevoflurane, is used.

[0208] In a first step, the O gas fraction in the exhaled gas flow is determined. Then, in an optional second step, the CO gas fraction in the exhaled gas flow can also then be determined from the O gas fraction in the exhaled gas flow. However, in this embodiment, if the gas fraction in the device gas flow 11" is time-varying, it is the same gas that is measured in the combined gas outflow 15". Thus, since O (not CO) is provided by the device gas flow 11", it is the O fraction that is time-varying in the device gas flow 11", and therefore it is the O fraction that is measured in the combined gas outflow 15". As described below, the CO fraction can then be derived from the measured O fraction.

[0209] The device is operated to provide a device gas flow 11'' having a time-varying gas fraction (O gas fraction) having a therapeutic gas fraction composition 61 and a signature (time-varying) gas fraction composition 62, as described above. In this example, a constant therapeutic gas fraction 61 is provided and added to a square wave signature gas fraction composition 62 to generate a device gas flow 11'' with a time-varying gas fraction as shown in FIG. 6A. In some embodiments, the signature gas fraction composition 62 can be added to the constant therapeutic gas fraction composition 61 to generate a device gas flow 11'' with a time-varying gas fraction as shown in FIG. 6A. The controller 19 or a user operates the flow source 10 to provide a device gas flow 11'' with a gas fraction. The controller 19 may be programmed with a desired device gas flow 11'' with a varying gas fraction to generate the varying gas fraction to provide a desired variation in gas fraction over time.

[0210] During use, the patient inhales device gas flow 11'' and exhales gas flow 13''. Exhaled gas flow 13'' combines with leak gas flow 12'' to produce a combined gas outflow 15'' as shown in Figure 6A. E The last graph showing O2 is for the expiratory phase.

[0211] Sensor 14 measures the O fraction in the combined gas outflow 15'' and passes this information to controller 19. The output of sensor 14 measuring a parameter of combined gas outflow 15'' is shown as waveform 15'' shown in Figure 6A (showing gas fraction during exhalation). The controller must then process that output to determine the actual O fraction in the exhaled patient gas flow 13''. From this, the actual CO fraction of the exhaled gas flow 13'' can then be obtained.

[0212] The fraction of exhaled gas components, e.g., O2, as a percentage of total exhaled gas per volume can be determined from the combined gas outflow 15'' using a formula that uses knowledge of the change in gas fraction of the time-varying device gas flow. This determination can be obtained based on the premise that the fraction (component) of exhaled gas can be determined from known / measured quantities. F m (t), the volume fraction of the gas components measured in the patient combined gas outflow 15' from the patient at time t (this is the measured CO2 / O2 fraction parameter of the combined gas outflow 15', preferably measured by sensor 14). F m (t) is preferably measured at the patient's mouth when the patient's mouth is open and / or at the nose when the patient's mouth is closed. F o (t), the gas fraction of the system gas flow 11′ delivered to the patient from the respiratory system (system gas flow rate) at time t. F m (t+Δt), the volume fraction of the gas components measured in the patient combined gas outflow 15′ at time t+Δt (this is preferably the measured CO2 / O2 fraction parameter of the combined gas outflow, measured by sensor 14). F m (t+Δt) is preferably measured at the patient's mouth when the patient's mouth is open or at the nose when the patient's mouth is closed. F o (t+Δt), the gas fraction of the system gas flow 11′ provided to the patient from the breathing apparatus (system gas flow rate) at time t+Δt. For varying gas fractions, equation (6), derived from equation (4), can be used.

[0213] The gas fraction changes, but the flow rate Q o If is constant (i.e., does not change), then Q O (t+Δt)=Q O (t) and Therefore, the flow terms cancel out, which can be seen in the simplified equation

number

[0214] This formula makes it possible to recover the fraction of exhaled gas (in this case O2) in the exhaled gas flow 13.

[0215] 1. Used to derive (4)

number

[0216] Additionally, it is possible to further develop the CO2 gas fraction in the exhaled gas flow from the O2 gas fraction in the exhaled gas flow.

[0217] F for oxygenE Knowledge of (t) is given by F for carbon dioxide as follows: E (t) to enable the determination of

[0218] F for carbon dioxide o = 0 (i.e., the fraction of carbon dioxide in the gas from the breathing apparatus is negligible), equation (3) becomes

number

number

[0219] Therefore, the F of oxygen e Since (t) is known, kQ o / Q E is now expressed in terms of a known quantity, in that it is known from equation (3). Thus, the CO fraction of exhaled gas flow 13'' can be determined from the O fraction of exhaled gas flow 13''.

[0220] The O fraction in combined gas outflow 15'' is measured by sensor 14, and the gas fraction of device gas flow 11'' is known (or can be measured). Thus, by measuring the O fraction in combined gas outflow 15' using sensor 14 at two (or more) different times, and knowing / measuring the gas fraction of device gas flow 13'' at two (or more) different times, equations (6) and (8) can be used to determine the O fraction in exhaled gas flow 13'', and therefore the CO fraction in exhaled gas flow 13''.

[0221] In practice, the O2 fraction is measured continuously or periodically / discontinuously to obtain a real-time output, which can then be used in combination with knowledge / measurements of the device gas flow 11'', also continuously or periodically sampled, to determine the real-time CO2 fraction (from O2) of the exhaled gas flow 13''. This can be output as a graph, digital readout, etc. on a display. In practice, the gas fraction is varied continuously or discontinuously, but periodically or regularly, over a period of time to provide multiple data points. Thus, by varying the gas fraction at least once, the difference between the first gas fraction 11a'' and the second gas fraction 11b'' can be used. Thus, the controller measures the gas parameters at appropriate times and then calculates F for each measurement. E Calculate.

[0222] Some general remarks regarding this embodiment follow. The measured gas (i.e., the gas of interest) in the combined gas outflow 15'' is O2, which is ultimately used to obtain a determination of the CO2 fraction of the exhaled gas flow 13'' Time-varying parameters include gas fraction, preferably O2 The time-varying gas fraction includes a therapeutic gas fraction component and a time-varying gas fraction component. Time-varying gas fraction varies from 21% to 100% Preferably, the method is applied to a spontaneously breathing patient. The time-varying gas fraction may be applied throughout the patient's respiratory cycle. Alternatively, the time-varying gas fraction is applied during the patient's exhalation phase. In one variation, the method includes determining whether the O2 fraction has reached a predetermined threshold (useful to indicate the end of the pre-oxygenation phase). Once the O2 fraction for the exhaled gas flow 13'' has been determined, the CO2 fraction in the exhaled gas flow 13'' may optionally be obtained.

[0223] As noted above, once the O2 fraction in the exhaled gas flow is known (determined by measuring O2 in the combined gas outflow and using, for example, Equation (6)), the CO2 gas fraction can be determined. It is not necessary to determine the O2 gas fraction in this manner using Equation (6). Rather, the O2 gas fraction can be determined in another manner, such as by a sensor or other means for determining the O2 gas fraction in the exhaled gas flow. Once this is done, the CO2 gas fraction in the exhaled gas flow can be determined using Equation (8).

[0224] 6.1 Derivation of Equation (8) Using equation (3), F EO2 From F ECO2 is derived.

number

number

number

number

number

number

number

[0225] 7. Other Changes The following changes / additions are possible: The device may be used with any gas sampling device, sidestream or mainstream sampling. The controller may control flow rate, fraction, partial pressure, etc. based on information it receives. Any of the information may be received from a person via user input via a user interface rather than from a sensor. Also, any changes the controller makes may be determined by the controller or based on input received from a user via user input via a user interface. F E O2 also has F E CO2 may be measured in the same manner as described above, but by measuring the patient's O2 fraction. The embodiments are described for determining the exhaled gas flow gas parameter for one gas, e.g., CO or O. However, if a clinician may be monitoring more than one gas parameter (e.g., monitoring O fraction to assess preoxygenation and CO to assess respiration), the above embodiments may be applied to determining accurate exhaled gas flow parameters for all gas parameters of interest. The time-varying gas fraction embodiment can be implemented as a time-varying gas partial pressure embodiment through the use of different sensors and processing. Those skilled in the art will understand the relationship between gas fraction and gas partial pressure and can adapt accordingly. The above embodiments are merely some examples and should not be considered limiting. Generally speaking, any method and / or device that allows for time-varying parameters in the device gas flow 11 can be used to determine the gas fraction in the exhaled gas flow 13 based on the concepts embodied in the above model. As an example: F of the gas (using a time-varying flow rate) E of, Q o ,Q o (t+Δt),F m (t+Δt),F m (t) as a function of or F of gas (using time-varying gas fraction) E of, F o (t),F o (t+Δt),F m (t+Δt),F m (t) as a function of By asking. Although the embodiments refer to O2 and CO2, other gas parameters can also be determined using similar methods and devices, for example, a sensor for the combined gas outflow is a sensor for detecting the target gas parameter of interest in the exhaled gas flow.

Claims

1. 1. An apparatus for providing a gas flow and determining a parameter of a gas present in an exhaled gas flow from a patient, comprising: a flow source; a sensor for detecting a combined gas outflow from the patient; A controller; Including, The device comprises: providing a system gas flow having a time-varying gas ratio; determining parameters of gases present in the combined gas outflow; The combined gas outflow comprises: Leak gas flow from the equipment gas flow, and Exhaled gas flow from the patient Including, determining the parameters of the gases present in the exhalation gas flow using the determined parameters of the gases present in the combined gas outflow and the time-varying gas ratios. The apparatus is configured to:

2. the system gas flow having the time-varying gas ratio includes at least a first gas ratio at a first time and a second gas ratio at a second time; determining the parameters of the gases present in the exhalation gas flow using the determined parameters of the gases present in the combined gas outflow and the time-varying gas ratios; using the determined parameters of the gases present in the combined gas outflow determined at the first gas ratio and determined at the second gas ratio. The apparatus of claim 1 , comprising:

3. The apparatus of claim 2 , wherein the first gas ratio and the second gas ratio are different gas ratios.

4. The apparatus of claim 1 , wherein the parameters of the gases present in the exhalation gas flow include a gas ratio in the exhalation gas flow.

5. The parameter of the gas present in the exhaled gas flow is a gas ratio, and the gas is O 2 and / or CO 2 The device according to any one of claims 1 to 4, wherein

6. The sensor detects O 2 and / or CO 2 The device of any one of claims 1 to 5, configured to sense a ratio.

7. The parameter of the gas present in the exhalation gas flow is a gas ratio, and the determined parameter of the gas present in the combined gas outflow and the time-varying gas ratio are used to determine the gas ratio (F E ) determining the gas ratio as F o (t),F o (t+Δt),F m (t+Δt),F m (t) [In the formula, F E (t) is the gas component concentration in the exhaled gas flow (volume fraction of exhaled gas) at time t; F m (t) is the gas ratio of the gas components measured in the composite gas outflow at time t; F o (t) is the gas fraction of the system gas flow delivered to the patient at time t (system gas flow gas fraction); F m (t+Δt) is the gas ratio of the gas components measured in the combined gas outflow at time t+Δt (which is the measured CO 2 / O 2 ratio parameter), F o (t+Δt) is the gas fraction of the system gas flow delivered to the patient at time t+Δt (system gas flow gas fraction). as a function of An apparatus according to any one of claims 1 to 6.

8. The parameter of the gas present in the exhaled gas flow is a gas ratio, and the gas is CO 2 , O 2 , nitrogen, helium, and / or an anesthetic agent, and using the determined parameters and the time-varying gas ratios of the gases present in the combined gas outflow, determine the gas ratio (F E ) is determined by [Equation 1] [In the formula, F E (t) is the CO in the exhaled gas flow at time t 2 Or O 2 or other gas ratios (volume ratios of exhaled gases), F m (t) is the CO measured in the combined gas outflow at time t 2 gas ratio, F o (t) is the gas fraction of the system gas flow delivered to the patient at time t (system gas flow gas fraction); F m (t+Δt) is the CO measured in the combined gas outflow at time t+Δt 2 gas ratio, F o (t+Δt) is the gas fraction of the system gas flow delivered to the patient at time t+Δt (system gas flow gas fraction); Q o is the flow rate of the apparatus gas flow, F E is the gas fraction of said gas present in said exhaled gas flow] The apparatus according to any one of claims 1 to 7, comprising using

9. 9. Apparatus according to any one of claims 1 to 8, wherein the sensor is positioned to measure the parameter of the gases present in the combined gas outflow at or near the patient's mouth and / or nose.

10. 10. The apparatus of any one of claims 1 to 9, further comprising a humidifier for humidifying the apparatus gas flow.

11. 11. The apparatus of any one of claims 1 to 10, further comprising a non-sealing patient interface for providing the apparatus gas flow to the patient.

12. The apparatus of any one of claims 1 to 11, wherein the apparatus gas flow is a high flow gas flow.

13. The apparatus of any one of claims 1 to 12, wherein the apparatus gas flow has a flow rate of between 20 LPM and 90 LPM.

14. 14. The apparatus of any one of claims 1 to 13, further comprising a proportional valve, wherein the controller is configured to control the proportional valve to deliver the apparatus gas flow having the time-varying gas ratio.

15. An apparatus according to any preceding claim, wherein the time-varying gas ratio is a fluctuating gas ratio.

16. 16. Apparatus according to any one of the preceding claims, wherein the time-varying gas ratio varies from 21% to 100%.

17. Apparatus according to any one of the preceding claims, wherein the parameters of the gases present in the combined gas outflow are determined during the expiratory and / or inspiratory phase of the patient's breathing.

18. The gas is O 2 and The device 2 ratio, and F mCO2 ,k,Q o ,Q E [In the formula, F mCO2 is the measured CO in the combined gas outflow 2 gas ratio, k is the fraction of the device gas flow exiting the patient's mouth (and (1-k) is the fraction through the nose); Q o is the flow rate of the apparatus gas flow, Q E is the flow rate of the exhaled gas flow. The CO present in the exhaled gas flow is calculated using a function of 2 18. The apparatus of claim 1, configured to determine the gas ratio of

19. The gas is O 2 and The device 2 ratio, and [Equation 2] [In the formula, F mCO2 is the measured CO in the combined gas outflow 2 gas ratio, k is the fraction of the device gas flow exiting the patient's mouth (and (1-k) is the fraction through the nose); Q o is the flow rate of the apparatus gas flow, Q E is the flow rate of the exhaled gas flow. using the CO 2 present in the exhaled gas flow 2 and determining a gas ratio of An apparatus according to any one of claims 1 to 18.

20. The time-varying gas ratio is 2 The device according to any one of claims 1 to 19, wherein the ratio is a ratio.

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