System and method for determining a patient's oxygen consumption level

Abstract

According to one aspect, an intake rim configured to carry a first gas for inhalation by a patient, an exhalation rim configured to carry a second gas exhaled by the patient, a patient interface assembly connected to the intake rim and the exhalation rim and configured to carry the first gas to the patient and the second gas from the patient, a first oxygen sensor configured to measure the oxygen concentration in the second gas in a first sampling region, a first carbon dioxide sensor configured to measure the carbon dioxide concentration in the second gas in a second sampling region, a flow sensor configured to measure the flow rate of the first gas or the second gas, and a processor configured to determine the oxygen consumption level of the patient using an indicator of the oxygen concentration in the first gas, an indicator of the carbon dioxide concentration in the first gas, and data obtained via the first oxygen sensor, the first carbon dioxide sensor, and the flow sensor. A system for determining the oxygen consumption level of a patient is provided.

Description

Technical Field

[0001] This patent application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63 / 390,356, filed on Jul. 19, 2022, the content of which is incorporated herein by reference.

[0002] The present invention relates to systems and methods for determining a patient's oxygen consumption level. More particularly, the present invention relates to systems and methods for determining the level of a patient's oxygen consumption using data received from various sensors.

Background Art

[0003] Measurements that enable determination of a patient's oxygen consumption (e.g., the amount of oxygen consumed, VO2) and carbon dioxide production (e.g., the amount of carbon dioxide produced, VCO2) are highly desirable in a variety of medical applications, including, for example, anesthesia, critical care, and nutritional management. Determining a patient's oxygen consumption can be particularly beneficial to a clinician because oxygen consumption can indicate the level of oxygen transport from the patient's lungs to any of the patient's tissues that require oxygen. Thus, measurement of oxygen consumption can provide important insights into a patient's cardiovascular and metabolic status.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The size, cost, and accuracy of existing systems limit the application of measurements that enable determination of oxygen consumption. Conventionally, these types of measurements have used expensive and bulky metabolic carts, which have long startup times and have been used intermittently.

[0005] A more compact system, called a breath-by-breath system, relies on high-frequency measurement of oxygen concentration in a gas stream. The accuracy of a breath-by-breath system depends largely on the precise temporal alignment (timing alignment) of the measured oxygen concentration and the waveform of the gas stream.

[0006] A smaller, less expensive, and more accurate system for determining oxygen consumption and carbon dioxide production is highly desirable.

Means for Solving the Problem

[0007] It is desirable to reduce the complexity and cost associated with determining a patient's oxygen consumption and carbon dioxide production and improve its accuracy. The inventors of the present disclosure have recognized that a patient's oxygen consumption and carbon dioxide production can be determined using measurements of the oxygen concentration in the gas exhaled by the patient (exhaled gas) at a first sampling position and generally available measurements of the carbon dioxide concentration of the exhaled gas in a second sampling region. As a result, the architecture of the device required to determine a patient's oxygen consumption is simplified.

[0008] More specifically, for example, by determining a value of a patient's oxygen consumption using measurements from a generally available carbon dioxide sensor, such as a capnography device, the need for a separate additional carbon dioxide sensor as used in prior art systems is eliminated. In addition, by using a generally available carbon dioxide sensor, such as a capnography device, rich clinical information of a high-frequency volumetric capnography waveform can be preserved.

[0009] According to a first particular aspect, a system for determining a patient's oxygen consumption level is provided. The system includes an intake rim configured to carry a first gas for inhalation by the patient, an exhalation rim configured to carry a second gas having the gas exhaled by the patient, and a patient interface assembly connected to the intake rim and the exhalation rim. The patient interface assembly is for carrying the first gas to the patient and carrying the second gas from the patient. The system further includes a first oxygen sensor configured to measure the oxygen concentration of the second gas in a first sampling region, a first carbon dioxide sensor configured to measure the carbon dioxide concentration of the second gas in a second sampling region, and a flow sensor configured to measure the flow rate of the first gas or the second gas. The system further includes a processor configured to determine the patient's oxygen consumption level using an indicator of the oxygen concentration in the first gas, an indicator of the carbon dioxide concentration in the first gas, and data obtained via the first oxygen sensor, the first carbon dioxide sensor, and the flow sensor. Advantageously, the need for a separate additional carbon dioxide sensor as used in prior art systems is eliminated.

[0010] In some embodiments, the system may further include a first mixing chamber configured to receive a portion of the second gas. The first mixing chamber may include one or more of the first oxygen sensors and a second carbon dioxide sensor configured to measure the carbon dioxide concentration of a portion of the second gas used for verifying the carbon dioxide concentration measured using the first carbon dioxide sensor. Advantageously, using the mixing chamber enables mixing of the second gas, thereby avoiding the need for high-frequency measurements of oxygen concentration that require precise temporal alignment of the measured oxygen concentration and the waveform of the gas flow. Using the second carbon dioxide sensor to verify the measurement of the first carbon dioxide sensor makes a defect in the first carbon dioxide sensor more noticeable.

[0011] In some embodiments, the first mixing chamber is configured to receive a portion of the second gas via connection with the patient interface assembly or via connection with the exhalation rim.

[0012] In some embodiments, the system may further include a mechanical ventilator. The inhalation rim and the exhalation rim may be connected to the mechanical ventilator. The following conditions, The first mixing chamber is configured to receive a portion of the second gas via connection with the exhaust port of the mechanical ventilator, The oxygen concentration in the first gas is determined using the mechanical ventilator, and The carbon dioxide concentration in the first gas is determined using the mechanical ventilator One or more of which can be satisfied. Advantageously, by determining the oxygen concentration and / or carbon dioxide concentration in the first gas using a mechanical ventilator, the need for additional sensors is eliminated, thereby simplifying the device architecture required to determine the patient's oxygen consumption.

[0013] In some embodiments, the system further includes one or more of a second oxygen sensor configured to measure the oxygen concentration in the first gas in a third sampling region and a third carbon dioxide sensor configured to measure the carbon dioxide concentration in the first gas in a fourth sampling region.

[0014] In some embodiments, the system may further include a second mixing chamber configured to receive a portion of the first gas via connection with the inhalation rim or via connection with the patient interface assembly, the second mixing chamber having one or more of the second oxygen sensor and the third carbon dioxide sensor.

[0015] In some embodiments, the first carbon dioxide sensor may include a capnography device.

[0016] In some embodiments, the capnography device can be a mainstream capnography device or a sidestream capnography device.

[0017] In some embodiments, the system may include a patient Y-connector having a first port connected to an end of an inspiratory limb, a second port connected to an end of an expiratory limb, and a third port connected to an end of a patient interface assembly.

[0018] According to a second aspect, there is provided a computer-implemented method for determining a patient's oxygen consumption level. The method includes receiving first oxygen concentration data indicative of the oxygen concentration in a first gas inhaled by the patient. The method further includes receiving first carbon dioxide data indicative of the carbon dioxide concentration in the first gas. The method further includes receiving second oxygen concentration data indicative of the oxygen concentration in a second gas having the gas exhaled by the patient, wherein the oxygen concentration in the second gas is measured using an oxygen sensor in a first sampling region. The method further includes receiving second carbon dioxide data indicative of the carbon dioxide concentration in the second gas, wherein the carbon dioxide concentration in the second gas is measured using a first carbon dioxide sensor in a second sampling region. The method further includes receiving flow rate data indicative of the flow rate of the first gas or the second gas. The method further includes determining the patient's oxygen consumption level based on the received data.

[0019] In some embodiments, the method further includes receiving third carbon dioxide data indicative of the carbon dioxide concentration in the second gas measured using a second carbon dioxide sensor disposed at a first sampling position, comparing the second carbon dioxide data with the third carbon dioxide data, and generating a warning in response to determining that the difference between the second carbon dioxide data and the third carbon dioxide data exceeds a threshold level.

[0020] Determining the patient's oxygen consumption level VO2 may involve the following mathematical formula

Number

Number

Number

Number

[0021] In some embodiments, each of the variables V exh , FiO2, FiCO2, FiCO2, and FeCO2 represents an average value over a defined time period.

[0022] In some embodiments, the first carbon dioxide data can have the ambient carbon dioxide concentration. Advantageously, this feature results in a further simplification of the device architecture required to determine the patient's oxygen consumption.

[0023] According to a third aspect, a computer program product is provided. The computer program product can have a non-transitory computer-readable medium having computer-readable code embodied therein, and the computer-readable code is configured to cause a suitable computer or processor to perform the steps of the methods described herein when executed by the computer or processor.

[0024] These and other aspects will be apparent from and will be elucidated with reference to the embodiments described hereinafter.

Brief Description of the Drawings

[0025] Here, by way of mere example, exemplary embodiments will be described with reference to the following drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0026] Determining a patient's oxygen consumption level and carbon dioxide production level can provide insights into the subject's health and health status. For example, measurements that enable determination of a patient's oxygen consumption level and carbon dioxide production level are referred to as metabolic monitoring because these parameters enable the amount of energy consumed by the patient's body to be estimated (e.g., indirect calorimetry). Also, oxygen consumption data can indicate the level of oxygen transport from the patient's lungs to the areas of the patient's tissues that require oxygen, and is thus particularly important when monitoring critically ill patients. Thus, oxygen consumption data can provide important insights into the patient's cardiovascular and metabolic status.

[0027] Oxygen consumption can be defined as the difference between the amount of oxygen V inh O2 inhaled and the amount of oxygen V exh O2 exhaled, and can be determined using the following equation

Equation

[0028] The amount of oxygen inhaled and the amount of oxygen exhaled can be calculated by direct measurement or indirect estimation. In some examples, V exh is directly measured, while V inh can be indirectly estimated, for example, using the Haldane transformation. In this Haldane transformation, the amount of gas V inh inhaled by the patient is estimated from the amount of gas V exh exhaled by the patient. The Haldane transformation is based on the assumption that the amount of nitrogen (inert gas) inhaled is equal to the amount of nitrogen exhaled.

[0029] The following equation

Equation

Number

[0030] In some examples, the patient can breathe with the gas received from a mechanical ventilator. For example, the patient may be connected to an endotracheal tube or a face mask configured to supply the gas flow from the mechanical ventilator to the patient. The oxygen concentration associated with the gas flow received from the mechanical ventilator can be set to a specified value such as a volume percentage of, for example, 20%, 25%, 30%, 40%, 50%, 60%, etc. The FiO2 value used in equations (4) and (5) (and similarly equations (6) and (7)) to determine the oxygen consumption and carbon dioxide production respectively can be the oxygen concentration set by the mechanical ventilator. In some examples, the value of the oxygen concentration in the inhaled gas (e.g., supplied by the mechanical ventilator) is assumed to be constant during the process of the patient's inspiration (e.g., inhaled breath). In some examples, the FiO2 value can be determined using an oxygen sensor (e.g., an oxygen sensor disposed within the mechanical ventilator).

[0031] In some examples, the FiCO2 value can be determined using a mechanical ventilator (e.g., a carbon dioxide sensor disposed within the mechanical ventilator). In other examples, the FiCO2 value can be assumed to be the ambient carbon dioxide concentration in the air in the atmosphere (e.g., 400 ppm). In some examples, the FiCO2 value can be set to a value of zero considering that the carbon dioxide concentration in the gas exhaled by the patient is typically relatively high. In some examples, the FiCO2 value can be measured using a carbon dioxide sensor configured to sample the gas inhaled by the patient or a sample of the gas.

[0032] In some examples, the FeO2 value can be determined using an oxygen sensor configured to sample the gas exhaled by the patient or a sample of the gas. The FeCO2 value can be determined using a carbon dioxide sensor configured to sample the exhaled gas of the patient or a sample of the gas.

[0033] Expired volume V exh can be determined by measuring the gas flow rate in the expiratory phase. The expired volume V exh can be determined using the flow rate Q exh of the exhaled gas. In some examples, V exh is referred to as the average flow (e.g., flow rate) (e.g., average flow rate per minute) of the gas exhaled by the patient. Measuring the gas concentration using a mixing chamber enables the use of the average value of V exh . The advantage of using Equation (2) (or using Equation (3)) to determine the amount of gas exhaled by the patient is that only a single flow measurement (e.g., from a single flow sensor) is required to estimate the oxygen consumption and carbon dioxide production, thereby reducing the contribution of the flow measurement error to the overall error in the determination of oxygen consumption.

[0034] The oxygen consumption and carbon dioxide production can be determined by combining equations (1) and (2).

Number

Number

[0035] Equations (4) and (5) can provide the oxygen consumption and carbon dioxide production respectively, based on the values of V exh , FiO2, FeO2, FiCO2, and FeCO2 (e.g., measured values). For example, the measurements of V exh , FiO2, FeO2, and FiCO2 can be performed every 0.1 seconds, 1 second, 2 seconds, 5 seconds, etc. These measurements are averaged over time scales such as 1 second, 2 seconds, 5 seconds, 10 seconds, 1 minute, etc. V exh , FiO2, FeO2, and FiCO2 measurements can be averaged, and the advantage associated with this is that the signal-to-noise ratio related to these measurements can be increased. V exh , FiO2, FeO2, and FiCO2 measurements can be averaged, and a further advantage is that the temporal alignment of each of these measurements is less important, less time-consuming, and less likely to cause misalignment. Therefore, the accuracy of determining the oxygen consumption and carbon dioxide production can be improved. These advantages are further realized by using a mixing chamber for sampling the gas (e.g., the gas inhaled by the patient or the gas having the gas exhaled by the patient), as will be described in more detail below.

[0036] The oxygen consumption and carbon dioxide production can also be determined by combining equations (1) and (3).

Number

Number

[0037] The decision to use an inhalation or exhalation flow sensor depends on which location provides a more accurate flow measurement value.

[0038] To determine an accurate value of oxygen consumption, Q exh and thus, V exh measurements may be made at the point representing the flow rate, and thus the volume, of the exhaled gas at the point where the oxygen concentration of the exhaled gas is measured. This feature will be described in more detail with reference to FIG. 1 below. Similarly, Q inh and thus, V inh measurements may be made at the point representing the flow rate, and thus the volume, of the inhaled gas at a point corresponding to the point where the oxygen concentration of the exhaled gas is measured. This will be described in more detail with reference to FIG. 1 below.

[0039] According to a first aspect, a system for determining a patient's oxygen consumption level is provided. FIG. 1 is a schematic diagram of an example of a system 100 for determining a patient's oxygen consumption level. The system 100 has an intake rim 102 configured to carry a first gas for inhalation by the patient. In some embodiments, the system 100 can have a mechanical ventilator (not shown in FIG. 1). The intake rim may have a tube. For example, the intake rim can have a tube that is connected to the mechanical ventilator at a first end and to the patient interface assembly at a second end. The first gas can have one or more gases such as, for example, oxygen, nitrogen, or carbon dioxide. The first gas can have an oxygen concentration determined by the settings of the ventilator, such as, for example, 20%, 30%, or 50%. The gas pressure of the first gas can be ambient pressure (e.g., 1 bar) or high pressure (e.g., higher than ambient pressure). This first gas can be at a pressure such as 5 cmH20, 10 cmH20, 15 cmH20, 20 cmH20, or 30 cmH20 or higher. The first gas, which is at a pressure higher than ambient pressure, can facilitate the patient's assisted breathing and / or the first gas can flow along the intake rim 102 in a direction from the mechanical ventilator towards the patient. In some examples, the mechanical ventilator can have a pump to cause the first gas to flow along the intake rim in a direction from the mechanical ventilator towards the patient.

[0040] System 100 further includes an exhalation rim 104 configured to carry a second gas having gas exhaled by a patient. This second gas may have gas exhaled by the patient, or a mixture of gas exhaled by the patient and a first gas (e.g., surplus first gas not required by the patient for breathing). The exhalation rim 104 can have a tube. For example, the exhalation rim 104 can have a tube connected to a mechanical ventilator at a first end and connected to a patient interface assembly at a second end. The second gas can include oxygen, carbon dioxide, nitrogen, water vapor, etc. (e.g., any gas exhaled by the patient).

[0041] System 100 further includes a patient interface assembly 106 connected to the inhalation rim 102 and the exhalation rim 104, and the patient interface assembly 106 is configured to carry a first gas to the patient and carry a second gas from the patient. In some examples, the patient interface assembly 106 may have an endotracheal tube or a face mask. In some examples, the patient interface assembly 106 may be connected to a tube configured to carry a first gas to the patient and carry a second gas from the patient. For example, this tube may be connected to the patient interface assembly 106 at a first end and connected to an endotracheal tube or a face mask at a second end. In some examples, the patient interface assembly 106 may have a Y-piece or a Y-connector having three ports (e.g., inlets or outlets) respectively connected to the inhalation rim 102, the exhalation rim 104, and an end of the patient interface assembly. In some examples, the Y-connector can be respectively connected to the inhalation rim 102, the exhalation rim 104, and a tube, where the tube may be connected to the patient interface assembly 106. The Y-connector may be called a patient wy, or a patient wy connector.

[0042] In some examples, the amount of the first gas supplied to the patient via the intake limb 102 is greater than the amount of gas required for breathing. In some examples, any excess first gas (e.g., the excess first gas that the patient did not require for breathing) flows from the intake limb 102 to the exhalation limb 104 (e.g., using the patient interface assembly 106). In some examples, this excess first gas may be referred to as a bypass flow or a bias flow.

[0043] The system 100 further includes a first oxygen sensor 108 configured to measure the concentration of oxygen in the second gas in a first sampling region. In some examples, the oxygen sensor 108 can measure the concentration of oxygen in the second gas via a sidestream connection. For example, a portion of the second gas moving along the exhalation limb 104 may be separated from the main stream of the second gas, and the oxygen sensor 108 may be configured to measure the oxygen concentration in this portion of the second gas. In some examples, after the oxygen sensor 108 measures the oxygen concentration of this portion of the second gas, the portion of the second gas can return to the main stream of the second gas and be taken in. In some examples, the oxygen sensor 108 can be disposed within a mixing chamber configured to receive the second gas, as described in more detail below.

[0044] In some examples, the first sampling region can have a volume configured to sample a second gas via a sidestream connection. In some examples, the first sampling region may be located at a point along the exhalation rim 104, a point within the patient interface assembly 106 (e.g., a port of the patient interface assembly), or an exhaust port of a mechanical ventilator. When the first sampling region is located at a port of the patient interface assembly 106, the oxygen sensor is configured to measure the oxygen concentration only during the exhalation phase of the patient's respiration. In some examples, the first sampling region may have a region (e.g., a volume or a mixing chamber, etc.) configured to sample a portion of the second gas. In some examples, the first sampling region may have a chamber or housing that receives a sample (e.g., a portion) of the second gas from the main stream of the second gas (e.g., moving through the patient interface assembly 106 or the exhalation rim 104).

[0045] System 100 further includes a first carbon dioxide sensor 110 configured to measure the concentration of carbon dioxide in the second gas in a second sampling region. In some examples, the second sampling region is disposed at a port of the patient interface assembly 106. In some examples, the first carbon dioxide sensor 110 includes a capnography device (e.g., Capnostat). In some examples, the first carbon dioxide sensor 110 may form part of or be a component of a capnography device. In some examples, the second sampling region can have a sampling region (e.g., volume, housing, etc.) having a carbon dioxide sensor. The second sampling region may have a sampling region (e.g., volume or mixing chamber, etc.) configured to receive a portion of the second gas. In some examples, the second sampling region may have a different volume than the first sampling region (e.g., the first sampling region may have a volume within a first mixing chamber and the second sampling region may have a volume within a second mixing chamber). For example, the mixing chamber may have a first sampling region and the capnography device may have a second sampling region. In some examples, the value of the carbon dioxide production amount is determined based on the measured value of the carbon dioxide concentration measured using the first carbon dioxide sensor 110. In some examples, a processor 114 associated with the carbon dioxide sensor (e.g., capnography device) is configured to determine the value of the carbon dioxide production amount based on the measured value of the carbon dioxide concentration measured using the first carbon dioxide sensor 110. The capnography device can measure the value of the carbon dioxide production amount with an accuracy of ±10%. Measuring the carbon dioxide concentration in the second gas using the capnography device can preserve rich clinical information related to the high-frequency volumetric capnography waveform measured at the port of the patient interface assembly 106.When a capnography device is used to measure the carbon dioxide concentration in a second gas via a port of the patient interface assembly 106, for example, it is possible to determine clinical measurements including end-tidal carbon dioxide and dead space.

[0046] In some examples, the value of the carbon dioxide production amount determined using the measurement of the carbon dioxide concentration of the second gas at the second sampling position using the first carbon dioxide sensor 110 is used to determine the value of the concentration of carbon dioxide in the second gas at the first sampling position. For example, the following formula

Equation

[0047] To accurately determine the patient's oxygen consumption level, the value of V exh corresponds to the flow rate of the second gas at the measurement point of the oxygen concentration of the second gas measured by the first oxygen sensor 108 (for example, the first sampling position). Equation (8) is applicable regardless of the location where the VCO2 measurement is performed (for example, the second sampling position). For example, when the oxygen concentration of the second gas is measured by an oxygen sensor via a connection to the patient interface assembly 106, the measurement of the flow rate of the second gas moving through the patient interface assembly is used in Equation (8). In an example where the oxygen concentration of the second gas is measured by an oxygen sensor via a connection to the exhalation rim 104, the measurement of the flow rate of the second gas moving through the exhalation rim 104 is used in Equation (8). Using the measured value of the flow rate of the second gas at the measurement point of the measurement of the oxygen concentration of the second gas ensures that any additional (e.g., excess first gas or bypass gas) flow rate that can reduce the carbon dioxide concentration in the second gas is taken into account.

[0048] In other words, Equation (8) is used to estimate the concentration of carbon dioxide in a second gas within the expiratory limb 104 (e.g., at a first sampling location) using a value of the patient's carbon dioxide production determined using a measured value of the carbon dioxide concentration within the patient interface assembly 106 (e.g., at a second sampling location). Estimating the concentration of carbon dioxide in the second gas within the expiratory limb 104 in this manner (e.g., using a carbon dioxide sensor at the second sampling location) can eliminate the need for a carbon dioxide sensor (e.g., an additional carbon dioxide sensor) configured to measure the concentration of carbon dioxide in the second gas at the first sampling location.

[0049] In embodiments where the flow rate measurement is performed on the inspiratory side (e.g., the inspiratory limb), V in Equation (8) exh is inh assumed to be. In other words, V exh is inh can be replaced with.

[0050] In some embodiments, a main stream capnography device can be used. A main stream capnography device is a device that measures the carbon dioxide concentration in situ (e.g., using a carbon dioxide sensor placed directly in the flow of the second gas). In some embodiments, a side stream capnography device can be used (e.g., using a carbon dioxide sensor configured to sample a portion of the second gas separated from the main stream of the second gas). In other words, a portion of the second gas is aspirated from or sampled from the main stream of the second gas moving along the inspiratory limb 102.

[0051] Furthermore, in a clinical environment, for example, to monitor a mechanically ventilated patient, a capnography device is commonly used. Advantageously, as opposed to using a separate carbon dioxide sensor disposed at a point along the exhalation rim 104, measuring the carbon dioxide concentration in the second gas using a capnography device simplifies the system design (e.g., does not require a carbon dioxide sensor disposed on the exhalation rim 104). In other words, in prior art systems, a carbon dioxide sensor is required on the exhalation rim 104 (e.g., in addition to a capnography device), whereas in the systems disclosed herein, the need for such a carbon dioxide sensor is eliminated. Further, using a carbon dioxide sensor, e.g., a capnography device, to directly sample the exhaled gas preserves rich clinical information associated with the high-frequency voltmetric capnography waveform. This information is lost if the measurement of the carbon dioxide concentration of the second gas is performed by a carbon dioxide sensor disposed within a mixing chamber configured to sample a portion of the second gas.

[0052] System 100 further includes a flow sensor 112 configured to measure the flow rate of the first gas or the second gas. In some examples, the flow sensor 112 is configured to measure the flow rate of the first gas at a point along the inhalation rim. In other examples, the flow sensor 112 is configured to measure the flow rate of the first gas passing through the patient interface assembly 106 (e.g., during the inhalation phase of the patient's breath). In some examples, the flow sensor 112 is configured to measure the flow rate of the second gas passing through the patient interface assembly 106 (e.g., during the exhalation phase of the patient's breath). In some examples, the flow sensor 112 is configured to measure the flow rate of the second gas at a point along the exhalation rim 104 or at the exhaust of the mechanical ventilator.

[0053] System 100 further includes a processor 114 configured to determine a patient's oxygen consumption level using an indicator of the oxygen concentration in a first gas, an indicator of the carbon dioxide concentration in the first gas, and data obtained via a first oxygen sensor 108, a first carbon dioxide sensor 110, and a flow sensor 112. In some examples, processor 114 is configured to determine a patient's oxygen consumption level by implementing Equation (4) (or Equation (6)). In some examples, processor 114 is configured to determine a patient's carbon dioxide production level using an indicator of the oxygen concentration in the first gas, an indicator of the carbon dioxide concentration in the first gas, and data obtained via a first oxygen sensor 108, a first carbon dioxide sensor 110, and a flow sensor 112 (e.g., by implementing Equation (5)). In some examples, processor 114 is configured to determine a patient's body energy consumption level based on the determined values of oxygen consumption and carbon dioxide production.

[0054] In some embodiments, system 100 may have a first mixing chamber configured to receive a portion of the second gas. The first mixing chamber can have a second carbon dioxide sensor configured to measure the carbon dioxide concentration in the portion of the second gas that is used for verification of the carbon dioxide concentration measured using the first oxygen sensor 108 and / or the first carbon dioxide sensor 110. In some examples, the first mixing chamber is configured to receive a portion of the second gas via a connection with the patient interface assembly 106 (e.g., a port of the patient interface assembly). In other examples, the first mixing chamber can be configured to receive a portion of the second gas via a connection with a port of the exhalation rim 104. In some examples, the first mixing chamber can be configured to receive a portion of the second gas via a connection with the exhaust port of the mechanical ventilator. In some examples, the first mixing chamber may be arranged in series with the patient interface assembly 106, the exhalation rim 104, or the exhaust port of the mechanical ventilator. For example, the first mixing chamber may be configured such that all of the second gas passes through the first mixing chamber.

[0055] In some embodiments, system 100 may have a mechanical ventilator. The inhalation rim 102 and the exhalation rim 104 can be connected to the mechanical ventilator. In some examples, the first mixing chamber is configured to receive a portion of the second gas via a connection with the exhaust port of the mechanical ventilator. In some examples, the oxygen concentration in the first gas may be determined using the mechanical ventilator and / or the carbon dioxide concentration in the first gas may be determined using the mechanical ventilator. In some examples, an indicator of the oxygen concentration in the first gas, used by the processor 114 of system 100 to determine the patient's oxygen consumption level, can be received from the mechanical ventilator. In some examples, an indicator of the carbon dioxide concentration in the first gas, used by the processor 114 of system 100 to determine the patient's oxygen consumption level, can be received from the mechanical ventilator.

[0056] In some embodiments, system 100 may include a second oxygen sensor configured to measure the oxygen concentration in the first gas in a third sampling region. The third sampling region is disposed at a point along the intake limb 102 or at a point along the patient interface assembly 106 (e.g., a port of the patient interface assembly). Measuring the oxygen concentration in this way can more accurately determine the oxygen consumption (e.g., rather than depending on the value of the oxygen concentration received from a mechanical ventilator). In some examples, the system may include a third carbon dioxide sensor configured to measure the concentration of carbon dioxide in the first gas in a fourth sampling region. The fourth sampling region is disposed at a point along the intake limb 102 or at a point along the patient interface assembly 106 (e.g., a port of the patient interface assembly).

[0057] In some embodiments, system 100 may include a second mixing chamber configured to receive a portion of the first gas via a connection with the intake limb 102 or via a connection with the patient interface assembly 106. The second mixing chamber may include the second oxygen sensor and / or the third carbon dioxide sensor. In some examples, the third sampling region and the fourth sampling region may be disposed within the second mixing chamber.

[0058] As described above, to determine an accurate value of oxygen consumption, Q exh and thus, V exhThe measurement can be made in terms of the flow rate of the exhaled gas, and thus the volume, at the point where the measurement of the oxygen concentration of the exhaled gas is performed. Referring to FIG. 1, when the first oxygen sensor 108 is configured to sample a portion of the second gas exhaled by the patient through the connection with the exhalation rim 104, the flow sensor 112 is configured to sample a portion of the second gas through the connection with the exhalation rim 104. The flow sensor 112 may be configured to measure the flow rate of the second gas (e.g., all or the main stream of the flow of the second gas). For example, the flow sensor may be configured to measure the flow rate of the gas within the exhalation rim or within the patient interface assembly. The first oxygen sensor 108 can be disposed upstream or downstream of the flow sensor 112. Since the flow rate of the second gas along the exhalation rim 104 does not change, the accuracy of the points along the exhalation rim 104 to which the first oxygen sensor 108 and the flow sensor 112 are respectively connected is not important.

[0059] In some examples, the first oxygen sensor 108 is configured to sample a portion of the second gas through the connection with the patient interface assembly 106. In this case, the measurement of the flow rate is configured to sample a portion of the second gas through the connection with the patient interface assembly 106. The first oxygen sensor 108 and / or the flow sensor 112 may be configured to sample the sample gas only during the exhalation phase of the patient's respiration. In some examples, the first oxygen sensor 108 and / or the flow sensor 112 may be disposed within a mixing chamber connected to the patient interface assembly 106. In some examples, the first oxygen sensor 108 and / or the flow sensor 112 may be connected to the patient interface assembly 106 through the connection with the patient interface assembly. Since the flow rate of the exhaled gas through the patient interface assembly does not change, the accuracy of the position where the first oxygen sensor 108 and / or the flow sensor 112 are configured to sample a portion of the second gas from the patient interface assembly 106 is not important.

[0060] Similarly, to determine the exact value of oxygen consumption, Q ixh and thus, V inh can be measured at a point corresponding to the point at which the oxygen concentration of the exhaled gas is measured, and thus, representing the volume. Referring to FIG. 1, when the first oxygen sensor 108 is configured to sample a portion of the second gas exhaled by the patient via connection with the exhalation limb 104, the flow sensor 112 is configured to sample a portion of the first gas via connection with the inhalation limb 102. When the first oxygen sensor 108 is configured to sample a portion of the second gas exhaled by the patient via connection with the patient interface assembly 106, the flow sensor 112 is configured to sample a portion of the first gas via connection with the patient interface assembly (or, the measurement of the flow sensor needs to be adapted using information from the ventilation device regarding the bypass flow, as will be explained in more detail below).

[0061] In some examples, the measurement of flow rate and the measurement of oxygen concentration may be performed at different locations (e.g., one via a connection to the exhalation limb and the other via a connection to the patient interface assembly). In this case, the measurement of oxygen concentration and / or the measurement of flow rate are adjusted so that these measurements correspond (e.g., as if these measurements were made at the same location). Similarly, the measurement of carbon dioxide concentration may be performed at a location different from the measurement of flow rate and / or the measurement of oxygen concentration. In this case, the measurement of carbon dioxide concentration, the measurement of oxygen concentration, and / or the measurement of flow rate are adjusted so that these measurements correspond (e.g., as if these measurements were made at the same location). Information regarding the bypass flow rate is used to adjust these measurements so that these measurements correspond. For example, the information regarding the bypass flow rate enables the measurement of the oxygen concentration of the second gas measured via a connection to the patient interface assembly to be adjusted so that it corresponds to the measurement of the flow rate measured at the exhalation limb (e.g., as if the oxygen concentration of the second gas was measured at a point along the exhalation limb or as if the flow rate measurement was made at the patient interface assembly).

[0062] FIG. 2 is a schematic diagram of a further example of a system 200 for determining a patient's oxygen consumption level. The system 200 includes an intake rim 202 configured to carry a first gas for inhalation by a patient 203, an exhalation rim 204 configured to carry a second gas exhaled by the patient, and a patient interface assembly 206 connected to the intake rim and the exhalation rim, the patient interface assembly carrying the first gas to the patient and carrying the second gas from the patient. The system 200 further includes a first oxygen sensor 208 configured to measure the concentration of oxygen in the second gas in a first sampling region 209. The system 200 further includes a first carbon dioxide sensor 210 configured to measure the concentration of carbon dioxide in the second gas in a second sampling region 211. The system 200 further includes a flow sensor 212 configured to measure the flow rate of the second gas in the first sampling region 209. The system 200 further includes a processor 214 configured to determine the patient's oxygen consumption level using an indicator of the oxygen concentration in the first gas, an indicator of the carbon dioxide concentration in the first gas, and data obtained via the first oxygen sensor, the first carbon dioxide sensor, and the flow sensor. The system 200 further includes a mechanical ventilator 216 configured to generate a flow of gas (e.g., the first gas) to the patient 203 and to exhaust the gas carried from the patient. The mechanical ventilator 216 has an exhaust port 218.

[0063] In some examples, the mixing chamber has the first sampling region 209. In some examples, the first sampling region is configured to sample a portion of the exhaled gas from the exhalation rim 204 (as shown in FIG. 2), from the exhaust port 218 of the mechanical ventilator 216 (not shown), or from the patient interface assembly 206 (not shown).

[0064] FIG. 2 shows a particular example of a system for determining a patient's oxygen consumption level. The components of the system shown in FIG. 2 may be positioned elsewhere in accordance with the embodiments disclosed herein.

[0065] According to a second aspect, there is provided a method (e.g., a computer-implemented method) for determining a patient's oxygen consumption level. FIG. 3 is a flowchart of an example of a computer-implemented method 300 for determining a patient's oxygen consumption level. In some examples, a processor is configured to perform one or more steps of method 300. The method includes, at step 302, receiving first oxygen concentration data indicative of the oxygen concentration in a first gas inhaled by the patient. In some examples, the first oxygen concentration data can be received from a mechanical ventilator. For example, the first oxygen concentration data may have a set oxygen concentration of the mechanical ventilator (e.g., a pre-set value of the oxygen concentration set by the user). In other examples, the first oxygen concentration data may have oxygen concentration data generated as a result of measuring the oxygen concentration in the first gas by an oxygen sensor disposed within the mechanical ventilator or an oxygen sensor associated with the mechanical ventilator. In some examples, the first oxygen concentration data may have oxygen concentration data generated as a result of measuring the oxygen concentration in the first gas by an oxygen sensor disposed in a third sampling region. For example, the first oxygen concentration data may have oxygen concentration data measured using an oxygen sensor configured to sample a portion of the first gas within an inspiratory limb or within a patient interface assembly. The oxygen sensor may be configured to indirectly measure the oxygen concentration in the first gas (e.g., via a sidestream measurement). In some examples, the third sampling region may be disposed within a mixing chamber (e.g., a second mixing chamber).

[0066] Method 300 includes, at step 304, receiving first carbon dioxide data indicative of the carbon dioxide concentration in a first gas. The first carbon dioxide data may be received from a mechanical ventilator. For example, the mechanical ventilator may have a carbon dioxide sensor configured to measure the carbon dioxide concentration in the first gas. In some examples, the first carbon dioxide data can be a predefined (e.g., not measured) value. For example, the first carbon dioxide data can have a value of the carbon dioxide concentration in the first gas corresponding to a value of the carbon dioxide concentration in ambient air (e.g., 400 ppm, etc.). In some examples, the first carbon dioxide data has a value of zero for the carbon dioxide concentration in the first gas. Assuming a predetermined value of zero for the carbon dioxide concentration in the first gas is justified in view of the relatively high carbon dioxide concentration produced by the patient during normal breathing. Advantageously, when the first carbon dioxide data is set to a predefined value (e.g., zero or 400 ppm, etc.), the carbon dioxide sensor need not measure the carbon dioxide concentration in the first gas, simplifying the system or architecture required to determine the patient's oxygen consumption level.

[0067] Method 300 includes, at step 306, receiving second oxygen concentration data indicative of the oxygen concentration in a second gas having the gas exhaled by the patient, the oxygen concentration of the second gas being measured using an oxygen sensor in a first sampling region. In some examples, the second oxygen concentration data can have oxygen concentration data measured using an oxygen sensor configured to sample a portion of the second gas within an exhalation limbus, within a patient interface assembly, or at an exhaust port of a mechanical ventilator. For example, the oxygen sensor can be configured to sample the second gas via a connection with the patient interface assembly, via a connection with the exhalation limbus, or via a connection with the exhaust port of the mechanical ventilator. The oxygen sensor may be configured to indirectly measure the oxygen concentration in the second gas (e.g., via a sidestream measurement).

[0068] Method 300 has, at step 308, the step of receiving second carbon dioxide data indicative of the carbon dioxide concentration in the second gas, where the carbon dioxide concentration in the second gas is measured using a first carbon dioxide sensor in a second sampling region. In some examples, the first carbon dioxide sensor may comprise a capnography device. In some examples, the first carbon dioxide sensor may be configured to sample a portion of the second gas within an exhalation rim, within a patient interface assembly, or at an exhaust port of a mechanical ventilator. For example, the first carbon dioxide sensor can be configured to sample the second gas via a connection with the patient interface assembly, via a connection with the exhalation rim, or via a connection with the exhaust port of the mechanical ventilator. The first carbon dioxide sensor may be configured to measure the carbon dioxide concentration in the second gas directly (e.g., in-situ) or indirectly (e.g., via a sidestream measurement).

[0069] Method 300 includes, in step 310, receiving flow rate data indicating the flow rate of a first gas or a second gas. The flow rate of the second gas can be measured using any known flow rate sensor known to those skilled in the art. The flow rate sensor may be configured to measure the flow rate of the second gas in a first sampling region. For example, the flow rate sensor can be disposed upstream or downstream of the first sampling region. In some examples, the first sampling region may have a region disposed within a first mixing chamber. In some examples, a flow rate sensor configured to measure the flow rate of the second gas at a first sampling location and an oxygen sensor configured to measure the oxygen concentration in the second gas at the first sampling location may be disposed within the first mixing chamber. In some examples, the flow rate sensor may be disposed upstream or downstream of the first mixing chamber. For example, the flow rate sensor may be disposed at the inlet or outlet of the first mixing chamber, or may be configured to sample the second gas via a connection with an exhalation rim upstream or downstream of the first mixing chamber, and so on. In some examples, the flow rate sensor may be disposed within the first mixing chamber (e.g., between the inlet and outlet of the first mixing chamber).

[0070] Method 300 includes, in step 312, determining a patient's oxygen consumption level based on the received data. In some examples, the received data can be received by a processor (e.g., processor 114). In some examples, the processor can be configured to directly receive data from a mechanical ventilator, one or more of the oxygen sensors, and / or one or more of the carbon dioxide sensors. For example, a processor associated with a mechanical ventilator, one or more of the oxygen sensors, and / or one or more of the carbon dioxide sensors can be configured to send data to processor 114. In other examples, data associated with (e.g., generated by) a mechanical ventilator (or a sensor disposed within or associated with a mechanical ventilator), one or more of the oxygen sensors, and / or one or more of the carbon dioxide sensors can be configured to send data to an intermediate location, such as a server disposed within a cloud computing environment. The oxygen consumption level of a patient can be determined using a processor disposed on a remote server, such as a processor disposed within such a cloud computing environment.

[0071] Figure 4 is a flowchart of an example of a computer-implemented method 300 for determining a patient's oxygen consumption level. In some examples, the processor is configured to perform one or more steps of method 400. Method 400 may have one or more of the steps of method 300. In some embodiments, method 400 includes, at step 402, receiving third carbon dioxide data indicative of the carbon dioxide concentration in a second gas measured using a second carbon dioxide sensor disposed at a first sampling location.

[0072] Method 400 includes, at step 404, comparing the second carbon dioxide data with the third carbon dioxide data.

[0073] Method 400 has, at step 406, a step of generating a warning in response to determining that the difference between the second carbon dioxide data and the third carbon dioxide data exceeds a threshold level. The difference between the second carbon dioxide data and the third carbon dioxide data is caused by a defect in the second carbon dioxide data and / or the third carbon dioxide data. Thus, advantageously, a defect can be identified in the first carbon dioxide sensor and / or the second carbon dioxide sensor. Using the second carbon dioxide sensor to verify the measurement of the first carbon dioxide sensor makes it conspicuous when there is a defect in the first carbon dioxide sensor.

[0074] According to a third aspect, a computer program product is provided. FIG. 5 is a schematic diagram of a non-transitory computer-readable medium 502 communicating with a processor 504. In some embodiments, a computer program product having a non-transitory computer-readable medium 502 is provided, the computer-readable medium having computer-readable code embodied therein, which, when executed by a suitable computer or processor 504, configures the computer or processor to perform the steps of the methods disclosed herein.

[0075] The processors 114, 504 can have one or more processors, processing units, multi-core processors or modules configured or programmed to control the components of the system 100 in the methods described herein. In certain implementations, the processors 114, 504 can have a plurality of software modules and / or hardware modules configured to perform individual or multiple steps of the methods described herein, or for performing such steps.

[0076] As used herein, the term "module" is intended to include, for example, a hardware component such as a processor configured to perform a particular function, or a component of a processor, or a software component such as a set of instruction data having a particular function when executed by a processor.

[0077] Embodiments of the present invention will also be understood to apply to a computer program adapted to implement the present invention, particularly a computer program on or in a carrier. The program can be in the form of source code, object code, intermediate source code, and object code, for example, in a partially compiled form, or in any other form suitable for use in implementing the method according to embodiments of the present invention. It will also be understood that such a program can have many different architecture designs. For example, the program code implementing the functions of the method or system according to the present invention may be subdivided into one or more subroutines. Many different ways of distributing functions among these subroutines will be apparent to those skilled in the art. These subroutines can be stored in one executable file and can form a self - contained program. Such an executable file has computer - executable instructions, for example, processor instructions and / or interpreter instructions (e.g., Java (registered trademark) interpreter instructions). Alternatively, one or more, or all, of the said subroutines can be stored in at least one external library file and can be linked, either statically or dynamically, for example at runtime, to a main program. This main program includes at least one call to at least one of the said subroutines. The said subroutines may have function calls to each other. Embodiments regarding computer program products have computer - executable instructions corresponding to at least one respective processing step of the methods described herein. These instructions are subdivided into subroutines and / or stored in one or more files that are linked either statically or dynamically. Another embodiment regarding computer program products has computer - executable instructions corresponding to at least one respective means of the systems and / or products described herein. These instructions are subdivided into subroutines and / or stored in one or more files that are linked either statically or dynamically.

[0078] The carrier of a computer program is any entity or device capable of carrying the program. For example, this carrier can include a data storage device, such as a ROM like a CD-ROM or a semiconductor ROM, or a magnetic recording medium such as a hard disk. Further, this carrier is a transmissible carrier such as an electrical signal or an optical signal, which is carried via an electrical or optical cable, or by wireless or other means. When the program is embodied in such a signal, the carrier is constituted by such a cable, or other devices or means. Alternatively, the carrier can be an integrated circuit in which the program is embedded, and this integrated circuit is adapted to perform the relevant method or is used when the relevant method is executed.

[0079] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the principles and techniques set forth herein, from a study of the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the fact that a plurality are recited does not exclude the presence of a plurality. A single processor or other unit can fulfill the functions of several items recited in the claims. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be advantageously used. A computer program can be stored or distributed on a suitable medium, such as an optical storage medium or a solid state medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless electrical communication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A system for determining a patient's oxygen consumption level, comprising: an inspiratory limb configured to carry a first gas for inhalation by the patient; an expiratory limb configured to carry a second gas having the gas exhaled by the patient; a patient interface assembly configured to carry the first gas to the patient and the second gas from the patient, and connected to the inspiratory limb and the expiratory limb; a first oxygen sensor configured to measure the oxygen concentration in the second gas in a first sampling region; a first carbon dioxide sensor configured to measure the carbon dioxide concentration in the second gas in a second sampling region; a flow sensor configured to measure the flow rate of the first gas or the second gas; a processor configured to determine the patient's oxygen consumption level using an indicator of the oxygen concentration in the first gas, an indicator of the carbon dioxide concentration in the first gas, and data obtained via the first oxygen sensor, the first carbon dioxide sensor, and the flow sensor A system having the above components.

2. The system according to claim 1, further comprising a first mixing chamber configured to receive a portion of the second gas, the first mixing chamber having: the first oxygen sensor; a second carbon dioxide sensor configured to measure the carbon dioxide concentration in a portion of the second gas used for verifying the carbon dioxide concentration measured using the first carbon dioxide sensor One or more of the above components.

3. The system according to claim 2, wherein the first mixing chamber is configured to receive a portion of the second gas via a connection to the patient interface assembly or via a connection to the expiratory limb.

4. The system according to claim 2, further comprising a mechanical ventilator, wherein the inspiratory limb and the expiratory limb are connected to the mechanical ventilator, and one or more of the following conditions are satisfied: a. The first mixing chamber is configured to receive a portion of the second gas via a connection to the exhaust port of the mechanical ventilator; b. The oxygen concentration in the first gas is determined using the mechanical ventilator; and c. The carbon dioxide concentration in the first gas is determined using the mechanical ventilator.

5. (a) A second oxygen sensor configured to measure the oxygen concentration in the first gas in a third sampling region, and (b) A third carbon dioxide sensor configured to measure the concentration of carbon dioxide in the first gas in a fourth sampling region The system according to claim 1, further comprising one or more of.

6. Further comprising a second mixing chamber configured to receive a portion of the first gas via a connection to the intake limb or via a connection to the patient interface assembly, the second mixing chamber comprising: The system of claim 5, comprising one or more of the second oxygen sensor and the third carbon dioxide sensor.

7. The system according to claim 1, wherein the first carbon dioxide sensor is a capnography device.

8. The system according to claim 7, wherein the capnography device is a mainstream capnography device or a sidestream capnography device.

9. A first port connected to an end of the intake limb, A second port connected to an end of the expiratory limb, And a third port connected to an end of the patient interface assembly The system according to claim 1, further comprising a patient Y connector having.

10. A computer-implemented method for determining a patient's oxygen consumption level, the method comprising: Receiving first oxygen concentration data indicating the oxygen concentration in a first gas inhaled by a patient; Receiving first carbon dioxide data indicating the carbon dioxide concentration in the first gas; Receiving second oxygen concentration data indicating the oxygen concentration in a second gas having the gas exhaled by the patient, wherein the oxygen concentration of the second gas is measured using an oxygen sensor in a first sampling region; step, Receiving second carbon dioxide data indicating the carbon dioxide concentration in the second gas, wherein the carbon dioxide concentration in the second gas is measured using a first carbon dioxide sensor in a second sampling region; step, Receiving flow rate data indicating the flow rate of the first gas or the second gas; Determining the patient's oxygen consumption level based on the received data Having, method.

11. Receiving, using a second carbon dioxide sensor disposed at the first sampling position, third carbon dioxide data indicative of the concentration of carbon dioxide in the second gas measured; Comparing the second carbon dioxide data with the third carbon dioxide data; Generating a warning in response to determining that a difference between the second carbon dioxide data and the third carbon dioxide data exceeds a threshold level The method according to claim 10, further comprising.

12. The step of determining the oxygen consumption level of the patient is determined using the formula 【Number 13】 Or 【Number 14】 having a step of using, where FeO2 is the oxygen concentration in the first gas, FiCO2 is the carbon dioxide concentration in the first gas, FeO2 is the oxygen concentration in the second gas, FeCO2 is the carbon dioxide concentration in the second gas, V ｅｘｈ is the average flow rate of the second gas at the measurement point of the oxygen concentration in the second gas, V ｉｎｈ is the average flow rate of the first gas, and FeCO2 is the mathematical formula 【Number 15】 Or 【Number 16】 Wherein VCO2 is the carbon dioxide production value determined using the second carbon dioxide data, the method according to claim 10.

13. the variable V ｅｘｈ The method according to claim 12, wherein each of FeO2, FeO2, FiCO2, and FeCO2 represents an average value over a defined time period.

14. The first carbon dioxide data has an ambient carbon dioxide concentration, the method according to claim 10.

15. A computer program product having a non-transitory computer-readable medium embodying therein computer-readable code configured to cause a computer or processor, when executed by a suitable computer or processor, to perform the method according to claim 10.

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