Systems and methods for metabolic monitoring

Abstract

The present disclosure describes a system for metabolic monitoring having: a collection of exhaled gas from a subject's nasal airway; a mixing chamber that receives a portion of the exhaled gas; a plurality of sensors that output signals related to gas parameters associated with inhalation and exhalation during one or more breaths; and a processor configured to: determine a flow rate of gas in an interface appliance; determine pressure changes near the subject's mouth to detect mouth breathing by the subject; determine O2 and CO2 concentration measurements of the portion of the exhaled gas in the mixing chamber; discard concentration measurements corresponding to mouth breathing; and determine a ratio of oxygen consumption, VO2, to carbon dioxide production, VCO2, of the subject based on the determined flow rate, CO2 concentration, and determined O2 concentration.

Description

[Technical Field]

[0001]

[01] The present disclosure relates to systems and methods for metabolic monitoring. [Background technology]

[0002]

[02] This disclosure relates to systems and methods for metabolic monitoring. Existing commercial devices cover several applications, including critically ill patients on ventilators, specialty visits (e.g., by dietitians and nutritionists), and spot checks in healthy subjects. Better devices for metabolic monitoring are needed. Summary of the Invention

[0003]

[03] Accordingly, one or more aspects of the present disclosure include an interface apparatus configured to collect exhaled gas from a subject's nasal airway; a mixing chamber operatively connected to the interface apparatus, the mixing chamber configured to receive at least a portion of the exhaled gas from the interface apparatus; a plurality of sensors configured to output signals related to one or more gas parameters associated with inhalation and exhalation by the subject during one or more breaths; and one or more physical computer processors operatively connected to the sensors to receive the output signals, the one or more physical computer processors configured to calculate the one or more inhaled and exhaled gases based on the output signals from the sensors. a measuring unit configured to measure a flow rate of gas in an interface device during breathing; a pressure change near the subject's mouth during one or more breaths based on signals output from a sensor to detect mouth breathing by the subject; a measuring unit configured to measure O and CO concentrations of a portion of the exhaled gas in a mixing chamber based on signals output from the sensor, discarding the concentration measurements corresponding to the mouth breathing; and a measuring unit configured to measure a ratio of oxygen consumption (VO) to carbon dioxide production (VCO) of the subject based on the determined flow rate of gas, the determined carbon dioxide concentration of the exhaled gas in the mixing chamber, and the determined oxygen concentration of the exhaled gas in the mixing chamber.

[0004] Another aspect of the present disclosure is a method for detecting mouth breathing by a subject, the method comprising: collecting exhaled gas from a nasal airway of the subject with an interface appliance; receiving at least a portion of the exhaled gas from the interface appliance in a mixing chamber operatively connected to the interface appliance; receiving output signals from a plurality of sensors related to one or more gas parameters associated with inhalation and exhalation by the subject during one or more breaths; determining, using one or more physical computer processors, a flow rate of gas in the interface appliance during the one or more breaths based on the output signals from the sensors; and using the one or more physical computer processors, detecting mouth breathing by the subject. determining, using one or more physical computer processors, O2 and CO2 concentration measurements of a portion of the exhaled gas in the mixing chamber based on the output signals from the sensor and discarding concentration measurements corresponding to mouth breathing; and determining, using one or more physical computer processors, a ratio of oxygen consumption VO2 to carbon dioxide production VCO2 of the subject based on the determined gas flow rate, the determined carbon dioxide concentration of the exhaled gas in the mixing chamber, and the determined oxygen concentration of the exhaled gas in the mixing chamber.

[0005]

[05] Yet another aspect of the present disclosure is an apparatus comprising: means for collecting exhaled gas from a subject's nasal airway; means for receiving at least a portion of the exhaled gas from an interface appliance; sensing means for outputting signals related to one or more gas parameters associated with inhalation and exhalation by the subject during one or more breaths; means for determining a flow rate of gas in the means for collecting exhaled gas during one or more breaths based on the signals output from the sensing means; and means for determining pressure changes near the subject's mouth during one or more breaths based on the signals output from the sensing means to detect mouth breathing of the subject. means for determining O2 and CO2 concentration measurements of a portion of the exhaled gas at the means for receiving at least a portion of the exhaled gas based on signals output from the sensing means and discarding concentration measurements corresponding to mouth breathing; and means for determining the ratio of oxygen consumption VO2 to carbon dioxide production VCO2 of the subject based on the determined gas flow rate, the determined carbon dioxide concentration of the exhaled gas at the means for receiving at least a portion of the exhaled gas, and the determined oxygen concentration of the exhaled gas at the means for receiving at least a portion of the exhaled gas.

[0006]

[06] These and other objects, features, and characteristics of the present disclosure, as well as the method of operation and function of the associated elements of structure, and combination of parts and economies of manufacture, will become more apparent from a consideration of the following description and the appended claims, with reference to the accompanying drawings, in which like reference numerals indicate corresponding parts in the various views, all of which form a part of this specification. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the disclosure. [Brief explanation of the drawings]

[0007] [Figure 1]

[07] FIG. 1 illustrates a system for overnight metabolic monitoring, according to one or more embodiments. [Figure 2A]

[08] Figure 1 illustrates an example of an interface appliance, according to one or more embodiments. [Figure 2B]

[09] FIG. 1 illustrates an example of a subject interface, according to one or more embodiments. [Figure 2C] FIG. 10 illustrates an example of a subject interface, according to one or more embodiments. [Figure 3]

[10] FIG. 1 illustrates an example system for overnight metabolic monitoring, according to one or more embodiments. [Figure 4]

[11] FIG. 1 illustrates an example system for overnight metabolic monitoring, according to one or more embodiments. [Figure 5]

[12] FIG. 1 illustrates a method for overnight metabolic monitoring, according to one or more embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0008]

[13] As used herein, the singular includes plural reference unless the context clearly dictates otherwise. As used herein, a statement that two or more parts or components are "coupled" shall mean that the parts are coupled or operate together directly or indirectly, i.e., through one or more intermediate parts or components, to the extent that a link occurs. As used herein, "directly coupled" means that two elements are in direct contact with each other. As used herein, "fixedly coupled" or "fixed" means that two components are coupled such that they move as one while maintaining a fixed orientation relative to each other.

[0009]

[14] As used herein, the term "single" means that a component is fabricated as a single piece or unit. That is, a component that includes parts fabricated separately and joined together as a unit is not a "single" component or body. As applied herein, the statement that two or more parts or components "engage" one another shall mean that the parts exert a force on one another, either directly or through one or more intermediate parts or components. As applied herein, the term "number" shall mean one or an integer greater than one (i.e., multiple).

[0010]

[15] Directional phrases used herein, such as, but not limited to, top, bottom, left, right, above, below, front, rear, and derivatives thereof, relate to the orientation of the elements as shown in the drawings and do not limit the scope of the claims unless expressly stated therein.

[0011]

[16] FIG. 1 illustrates an example of a system 100 for metabolic monitoring according to one or more embodiments of the present disclosure. In some embodiments, system 100 is configured for metabolic monitoring while a subject is inactive (e.g., sleeping). In some embodiments, system 100 is configured for nocturnal metabolic monitoring. System 100 allows a subject's metabolism to be monitored at home (overnight, without the need for skilled personnel) rather than requiring the use of metabolic chambers or other equipment that are expensive and only available in dedicated facilities for sporadic measurements. Continuous monitoring of metabolism and its changes can provide insight into basal energy expenditure and available glycogen stores, which can be used to adjust diet and physical activity to optimize weight and energy management.

[0012]

[17] In some embodiments, system 100 provides information about a subject's metabolic state based on measurements of oxygen consumption (VO2) and carbon dioxide production (VCO2) and their changes overnight. In some embodiments, system 100 includes a mixing chamber used for gas analysis (e.g., CO2 and O2 concentration measurements). The mixing chamber can be small and relatively portable. No subject cooperation is required other than wearing the interface. The VO2 and VCO2 measurements are used to estimate the subject's energy expenditure (EE) and respiratory quotient (RQ). Energy expenditure (EE) is used to assess an individual's caloric needs, while respiratory quotient (RQ) provides information about the nutrients (e.g., carbohydrates, fats, proteins, etc.) primarily used to generate energy.

[0013]

[18] In some embodiments, system 100 includes a subject interface 90 designed to collect all exhaled air in the subject's nose during one or more breaths (e.g., continuously with every breath) for further analysis. In some embodiments, system 100 is configured to detect mouth breathing (e.g., with pressure sensor 44) to discard invalid measurements (measurements including mouth breathing). This provides a more accurate determination of VO2, VCO2, EE, and / or RQ. System 100 then provides a better picture of the subject's metabolic state throughout the night.

[0014]

[19] In some embodiments, the system 100 comprises a subject interface 90, one or more sensors 40, a mixing chamber 30, one or more physical computer processors 60, a user interface 120, electronic storage 130, a network 150, and / or other components.

[0015]

[20] In some embodiments, the subject interface 90 is configured to pass a flow of breathable gas (e.g., ambient air) through the airways of the subject 70. The subject interface 90 is also configured to deliver breathable ambient air to the subject's nares and collect exhaled air from the subject's nares (e.g., using the interface appliance 80). In some embodiments, the subject interface 90 comprises a conduit 50, an interface appliance 80, one or more valves 85, and / or other components. In some embodiments, the interface appliance 80 is configured to removably engage one or more external orifices of the airways (e.g., nares) of the subject 70 to pass gas between the airways of the subject 70 and the subject interface 90. The interface appliance 80 can be removably coupled to the conduit 50 (e.g., the interface appliance 80 can be removed for cleaning, replacement, and / or other purposes). In some embodiments, the interface appliance 80 includes two prongs configured to be positioned in the subject's nares and form a seal with the subject's nasal passages. By sealing the nasal passages, all exhaled air can be collected from the subject's nostrils for further analysis, as described below. Examples of interface device 80 include nasal cannulas or other non-invasive or invasive interface devices that pass a flow of gas through the subject's airways. The present disclosure is not limited to these examples and contemplates using any delivery means to deliver a flow of gas to a subject.

[0016]

[21] In some embodiments, subject interface 90 includes a valve 85 configured to allow breathable gas to flow to the subject's nares. For example, one or more valves are disposed within interface appliance 80. In some embodiments, valve 85 is configured to allow breathable gas (e.g., air from the atmosphere) to flow in one direction. For example, valve 85 is configured to open during inspiration and close during expiration. Examples of such valves include one-way valves, check valves, non-return valves, and / or other valves that allow gas flow in only one direction. In some embodiments, subject interface 90 is configured to deliver breathable gas to the subject from a gas source (e.g., a pressurized gas source for supporting the subject's breathing).

[0017] In some embodiments, the sensor 40 is configured to generate an output signal communicating information related to one or more respiratory parameters of the subject 70 during one or more breaths. In some embodiments, the one or more respiratory parameters include a gas parameter associated with the breathable gas provided by the subject interface, a respiratory parameter associated with the breathing of the subject 70, a physiological parameter of the subject 70, and / or other parameters. The one or more gas parameters of the breathable gas include, for example, one or more of inspiratory flow rate, expiratory flow rate, inhaled volume, inhaled volume, pressure, humidity, temperature, acceleration, velocity, gas component concentrations (e.g., O2 concentration, CO2 concentration, etc.), and / or other parameters of the breathable gas. Respiratory parameters related to the breathing of the subject 70 include tidal volume, timing (e.g., start and / or end of inspiration, start and / or end of expiration, etc.), inspiratory flow, expiratory flow, respiratory rate, respiratory airflow, duration (e.g., of inhalation, exhalation, respiratory cycle, etc.), respiratory frequency, respiratory effort, exhaled gas component concentrations (e.g., O2 concentration, CO2 concentration, etc.), and / or other respiratory parameters. Physiological parameters include oximeter parameters, pulse, temperature, blood pressure, and / or other physiological parameters.

[0018]

[23] In some embodiments, sensor 40 comprises one or more sensors that measure such parameters directly (e.g., via fluid communication with the subject and / or the subject interface). In some embodiments, sensor 40 comprises one or more sensors that generate output signals related to one or more parameters indirectly (e.g., through measurements from other sensors or other components internal or external to system 100). In some embodiments, sensor 40 includes one or more position sensors for measuring the position of the subject interface, volume sensors for measuring inspired and / or expired gas volumes, pressure sensors for measuring gas pressure inside or outside the subject interface 90, humidity sensors for measuring humidity inside and / or outside the subject interface, and gas temperature sensors for measuring gas temperature. In some embodiments, sensor 40 includes one or more sensors configured to generate output signals related to physiological parameters of subject 70, such as cardiac sensors for measuring cardiac parameters of the subject, motion sensors for detecting subject movement, accelerometers, oximeters, audio sensors, video sensors (cameras), and / or other sensors. For example, in some embodiments, sensor 40 includes one or more flow sensors 42 (shown in FIGS. 3-4 ) configured to measure the flow of inhaled and / or exhaled air to or from the subject. Flow sensors 42 are configured to measure the flow of inhaled air by the subject, the flow of exhaled air by the subject, the flow of exhaled air within interface device 80, conduit 50, mixing chamber 30, and / or gas flow elsewhere in system 100.

[0019]

[24] In some embodiments, sensor 40 includes one or more pressure sensors 44 configured to output a signal related to gas pressure at one or more locations within system 100. For example, pressure sensor 44 may include a pressure line positioned at or near the subject's mouth and configured to measure pressure at or near the subject's mouth. In some embodiments, sensor 40 includes one or more O2 concentration sensors 45 (shown in FIGS. 3-4) configured to output a signal related to O2 concentration in exhaled breath. In some embodiments, one or more O2 concentration sensors 45 are configured to output a signal related to O2 concentration in inspired breath. In some embodiments, one or more O2 concentration sensors 45 are configured to output a signal related to O2 concentration in exhaled breath in a mixing chamber. In some embodiments, sensor 40 includes one or more CO2 concentration sensors 47 (shown in FIGS. 3-4) configured to output a signal related to CO2 concentration in exhaled breath. In some embodiments, one or more CO2 concentration sensors 47 are configured to output a signal related to CO2 concentration in inspired breath. In some embodiments, the CO sensor is a non-dispersive infrared (NDIR) CO sensor, although this should not be construed as limiting, and no other description is implied to be limiting, as other CO sensors may be considered.

[0020]

[25] In some embodiments, one or more CO2 concentration sensors 45 are configured to output a signal related to the CO2 concentration in the exhaled gas in the mixing chamber. In some embodiments, the mixing chamber includes a gas sensor, as well as humidity and temperature sensors necessary to compensate for these factors when calculating the gas concentration from the gas sensor. In some embodiments, the exhaled gas is sampled through an interface and sent to the mixing chamber, where it is mixed with previously sampled gas already present in the mixing chamber.

[0021]

[26] The sensor 40 may include sensors located in multiple locations, such as various locations within (or in communication with) the breathing device, conduit 50, interface appliance 80 on the subject 70 (or in communication with the breathing device, conduit 50), and / or other locations. In some embodiments, the processor 60 detects the status of a seal with the nostril (e.g., based on signals output from the sensor 40). For example, the processor 60 may be configured to detect exhaled air leakage (e.g., based on determining flow rate and / or pressure at the nostril and / or based on the appliance or its position relative to the nostril). During operation, if the seal is broken, the processor 60 may be configured to discard measurements or send an alert to the subject indicating that the seal between the appliance and the nostril has been broken.

[0022] 2A illustrates an example 200 of a subject interface 90 according to one or more embodiments. In these embodiments, the subject interface 90 includes an interface appliance 80 configured to engage the subject's nostrils to pass gases between the subject's airway and the subject interface 90. The interface appliance 80 includes two prongs 205, 207 configured to be positioned at the subject's nostrils and form a seal with the subject's nasal passages, thereby collecting all exhaled air from the subject's nostrils for further measurement and analysis. The subject interface 90 includes a conduit 50 operably connected to the interface appliance 80 and configured to direct the exhaled air to the mixing chamber 30 for further measurement and analysis. The subject interface 90 includes a pressure sensor 44 configured to measure pressure at or near the subject's mouth (via a pressure line 204 positioned at or near the mouth) to detect mouth breathing. Mouth breathing can be determined based on a change in the signal output from the pressure sensor 44 (indicative of a change in pressure at or near the subject's mouth).

[0023]

[28] In some embodiments, a rise in pressure (above a predetermined threshold) during exhalation indicates exhalation through the mouth. Exhalation through the mouth invalidates VO2 and VCO2 measurements. Therefore, the processor 60 discards VO2 and VCO2 measurements acquired during the time window in which mouth exhalation was detected (mouth pressure exceeded the threshold). To accurately determine the subject's nocturnal metabolic rate, measurements that include mouth breathing are discarded. For example, the acquired VO2 and VCO2 measurements (as well as the corresponding EE and RQ values ​​derived therefrom) are not displayed to the user.

[0024] As described below, in some embodiments, the processor 60 is configured to discard O2 and CO2 concentration measurements in response to detecting a pressure change at or near the mouth (indicative of mouth breathing) for each breath. For example, O2 and CO2 concentration measurements are determined for each breath (e.g., for one or more breaths). In response to a particular breath of one or more breaths being determined to include mouth breathing, the O2 and CO2 concentrations for that particular breath are discarded (and not used in further analysis and measurement of O2 consumption and / or CO2 production). In other words, O2-consuming VO2 and / or CO2-producing VO2 are measured only for breaths in which exhaled air comes from the subject's nasal airway. In some embodiments, O2-consuming VO2 and / or CO2-producing VCO2 are measured for all breaths (regardless of mouth breathing). In these embodiments, the VO2 and VCO2 corresponding to mouth breathing are subsequently discarded in the measurement of energy expenditure EE and respiratory quotient RQ.

[0025] 2B-2C illustrate an example of an interface device 80 according to one or more embodiments. The interface device 80 is a nasal interface including two prongs 205, 207 configured to fit into a subject's nares and form a seal with the subject's nasal passages. The interface device 80 includes a valve 85 configured to direct ambient gases toward the subject's airways (as indicated by arrow A in FIG. 2C). The valve 85 is a passive inhalation valve (e.g., a one-way valve, a check valve, a non-return valve, etc.). Active valves are also contemplated and compatible with embodiments of the present disclosure. During operation, inhaled gases (e.g., ambient air) enter the one-way inhalation valve 85 and enter the nose (through the prongs as indicated by arrow B). During exhalation, the valve is closed, and the gases are directed into a tube leading to a mixing chamber (not shown) (as indicated by arrow C in FIG. 2C).

[0026] 1, the system 100 includes a mixing chamber 30 operably connected to a subject interface 90. The mixing chamber 30 is configured to collect all or a portion of the exhaled breath. In some embodiments, the mixing chamber 30 is configured to include one or more sensors 40 for measuring gas parameters of the exhaled breath within the mixing chamber, such as O2 concentration, CO2 concentration, flow rate, volume, pressure, etc.

[0027]

[32] The processor 60 is configured to provide information processing functionality in the system 100. As such, the processor 60 includes one or more digital processors, one or more analog processors, one or more digital circuits designed to process information, one or more analog circuits designed to process information, a state machine, and / or other mechanisms for electronically processing information. In some embodiments, the processor 60 is operably connected to the sensor 40, the mixing chamber 30, the subject interface 90, the user interface 120, and / or other components of the system 100. While the processor 60 is illustrated in FIG. 1 as a single entity, this is for illustrative purposes only. In some implementations, the processor 60 includes multiple processing units. These processing units may be physically located within the same device (e.g., the sensor 40, the mixing chamber 30, the subject interface 90, the user interface 120, etc.), or the processor 60 may represent the processing functionality of multiple devices operating in concert and located outside the system 100 (e.g., in the cloud). In some embodiments, processor (60) represents the processing functionality of multiple devices located within and / or external to system 100 (eg, communicatively coupled via network 150).

[0028]

[33] Processor 60 is configured to execute one or more computer program components, including one or more of a parameter component 62, a metabolic state component 64, a feedback component 66, and / or other components. Processor 60 is configured to execute components 62, 64, and 66 by software, hardware, firmware, some combination of software, hardware, and / or firmware, and / or other mechanisms for configuring processing functions in processor 60.

[0029]

[34] While components 62, 64, and 66 are illustrated in FIG. 1 as being co-located within a single processing unit, it should be understood that in implementations in which processor 60 includes multiple processing units, one or more of components 62, 64, and 66 may be located remotely from the other components. The description of the functionality provided by various components 62, 64, and 66 described below is for illustrative purposes and is not intended to be limiting, as any of components 62, 64, and 66 may provide more or less functionality than described. For example, one or more of components 62, 64, and 66 may be eliminated, with some or all of its functionality being provided by the other components 62, 64, and / or 66. As another example, processor 60 may be configured to execute one or more additional components that perform some or all of the following functions attributed to one of components 62, 64, and / or 66:

[0030] In some embodiments, parameter component 62 is configured to receive, determine, and / or acquire one or more parameters (e.g., from components internal or external to system 100). The one or more parameters are determined based on signals output from sensor 40. In some embodiments, parameter component 62 is configured to determine one or more respiratory parameters related to the breathing of subject 70, one or more parameters of breathable gas within system 100 (e.g., parameters related to the flow of breathable gas delivered by a breathing device), one or more physiological parameters of subject 70, and / or other parameters. The respiratory parameters related to the breathing of subject 70 include the start and / or end of individual breaths. In some embodiments, the respiratory parameters include tidal volume, timing (e.g., start and / or end of inspiration, start and / or end of expiration, etc.), respiratory rate, duration (e.g., of inhalation, exhalation, a single respiratory cycle, etc.), respiratory airflow, respiratory effort, respiratory frequency, and / or other respiratory parameters. The one or more gas parameters of the flow of breathable gas delivered to the subject may include, for example, one or more of flow rate, heart rate, volume, pressure, humidity, temperature, acceleration, velocity, and / or other gas parameters. The physiological parameters may include oximeter parameters, pulse rate, temperature, blood pressure, movement, and / or other physiological parameters.

[0031]

[36] In some embodiments, the parameter component 62 is configured to determine the flow rate of the exhaled gas based on signals output from one or more sensors 40 (e.g., flow sensor 42). In some embodiments, the parameter component 62 is configured to determine the inspiratory flow rate, the expiratory flow rate, and / or other gas flow rate within the subject interface 90 (or interface appliance 80). In some embodiments, the flow rate of the entire exhaled gas is determined. As explained above, the interface appliance 80 is configured to form a seal with the nostrils to allow the entire exhaled gas to be collected. In some embodiments, the parameter component 62 is configured to determine the flow rate of a portion of the exhaled gas. For example, in some embodiments, the exhaled gas is sampled (after the entire exhaled gas has been collected). For example, in some embodiments, the sample is a percentage of the flow that is directed to a mixing chamber for further measurement (e.g., O2 concentration measurement and CO2 concentration measurement). In some embodiments, the parameter component 62 is configured to determine the volume of the inhaled gas and / or the volume of the exhaled gas. For example, based on signals output from a volume sensor within subject interface 90, mixing chamber 30, and / or elsewhere within or external to system 100. In some embodiments, the inspired and / or expired volume is determined based on signals output from flow sensor 42.

[0032]

[37] In some embodiments, parameter component 62 is configured to determine pressure at one or more locations inside or outside system 100. In some embodiments, parameter component 62 is configured to determine pressure at or near the subject's mouth. In some embodiments, the pressure is determined based on signals output from one or more sensors 40 (e.g., pressure sensor 44). In some embodiments, parameter component 62 is configured to determine pressure changes at or near the subject's mouth.

[0033]

[38] In some embodiments, the parameter component 62 is configured to measure an O2 concentration in breaths exhaled and / or inhaled by the subject. In some embodiments, the parameter component 62 is configured to measure an O2 concentration in a portion of the exhaled breath in the mixing chamber. In some embodiments, the O2 concentration is measured based on a signal output from the O2 sensor 45. As described above, the O2 sensor is located in the mixing chamber or elsewhere in the instrument interface. In some embodiments, the parameter component 62 is configured to measure a CO2 concentration in breaths exhaled from the subject. In some embodiments, the parameter component 62 is configured to measure a CO2 concentration in a portion of the exhaled breath in the mixing chamber. In some embodiments, the CO2 concentration is measured based on a signal output from a CO2 sensor. As described above, the CO2 sensor is located in the mixing chamber or elsewhere in the instrument interface. In some embodiments, the parameter component 62 is configured to discard the O2 and CO2 concentration measurements in response to detecting a pressure change at or near the mouth (indicative of mouth breathing). For example, in some embodiments, the parameter components measure O2 and CO2 concentrations for every breath (e.g., for one or more breaths). If a particular breath of breath is determined to include mouth breathing, the O2 and CO2 concentrations for that particular breath are discarded (and not used in further analysis and measurement of O2 consumption and / or CO2 production). In other words, O2 consumption and / or CO2 production are measured only for breaths in which exhaled air comes from the subject's nasal airway. In some embodiments, O2 consumption VO2 and / or CO2 production VCO2 are measured for every breath (regardless of mouth breathing). In these embodiments, VO2 and VCO2 corresponding to mouth breathing (based on pressure sensor output) are discarded in the measurement of energy expenditure EE and respiratory quotient RQ.

[0034]

[39] In some embodiments, metabolic status component 64 is configured to determine exhaled CO2 production (VCO2) based on the CO2 concentration determined in the mixing chamber. For example, in some embodiments, VCO2 can be calculated as the rate of carbon dioxide production in milliliters per minute. In some embodiments, metabolic status component 64 is configured to determine O2 consumption VO2 by the subject. In some embodiments, O2 consumption VO2 is determined based on the O2 concentration determined in the mixing chamber, the inspired volume, the expired volume, and the concentration of O2 in the inspired gas.

[0035]

[40] In some embodiments, the metabolic status component 64 is configured to calculate energy expenditure EE and respiratory quotient RQ based on the VO2 and VCO2 measurements. In some embodiments, EE is used to assess the subject's caloric needs. RQ is used to provide information about nutrients primarily used to generate energy (carbohydrates, fats, proteins). In some embodiments, respiratory quotient RQ is the ratio of VCO2 / VO2. In some embodiments, energy expenditure EE (metabolic rate) is calculated using the following formula: Metabolic rate (kcal per day) = 1.44 (3.94 VO2 + 1.11 VCO2) where VO2 is the rate of oxygen consumption in milliliters per minute and VCO2 is the rate of carbon dioxide production in milliliters per minute. This formula is: Metabolic rate (calories per minute) = 3.94 VO2 + 1.11 VCO2 It can also be written in units of calories per minute, such as:

[0036]

[41] In some embodiments, the feedback component 66 is configured to display the measured parameters (e.g., VO2, VCO2, EE, RQ, and / or other parameters determined by components 62, 64). The measurements and recommendations are displayed via a graphical interface (e.g., user interface 120, a dedicated display, a laptop, a smartphone, or the like). In some embodiments, the feedback component 66 is configured to provide recommendations regarding optimal nutritional and activity behaviors for managing weight (e.g., diet and / or activity based on the measurements as well as goals set by the user (e.g., lose weight, optimize physical performance)).

[0037]

[42] Figure 3 shows an example system 300 for nocturnal metabolic monitoring according to one or more embodiments. In this example, ambient air 302 is directed to a subject's nose 304 (e.g., via a subject interface having a valve similar to the subject interface of Figure 1). Exhaled breath from the subject's nose is directed to a mixing chamber 30, where O2 and CO2 concentrations are measured. A processor 60 determines VO2, VCO2, EE, and RQ based on the O2 and CO2 concentrations measured in the mixing chamber 30. Pressure changes at or near the mouth 310 are measured with a pressure sensor 44 to detect mouth breathing. Measurements that include mouth breathing are discarded to improve metabolic rate determination.

[0038]

[43] Figure 4 shows an example system 400 for overnight metabolic monitoring, according to one or more embodiments. In this example, ambient air 302 is directed to the subject's nose 304. The collected exhaled breath is sampled (after the entire exhaled breath is collected), and a sample 405 is directed to the mixing chamber 30 for further measurement. In some embodiments, a fixed percentage of the flow is collected in the mixing chamber. In some cases, 2% of the entire exhaled breath is directed to the mixing chamber 30, where the O2 and CO2 concentrations are measured. The processor 60 determines VO2, VCO2, EE, and RQ based on the O2 and CO2 concentrations measured in the mixing chamber 30. Pressure changes at or near the mouth 310 are measured with the pressure sensor 44 to detect mouth breathing. Measurements that include mouth breathing are discarded for better metabolic rate determination. The difference between the embodiments in Figures 3 and 4 is that in the embodiment of Figure 3, all of the exhaled air goes to a mixing chamber where O2 and CO2 measurements are made, while in the embodiment of Figure 4, a proportional sample of the exhaled air (i.e., a fixed percentage of the total flow at any one time) goes to the mixing chamber, with the remainder going directly to the ambient. Both configurations allow for measurement of VO2 and VCO2 and offer different tradeoffs between accuracy and size.

[0039]

[44] User interface 120 is configured to provide an interface between system 100 and subject 70 and / or other users, through which subject 70 and / or other users can provide information to and receive information from system 100. Other users include, for example, caregivers, physicians, and / or other users. This allows data, clues, results, and / or instructions, as well as any other communicable items collectively referred to as “information,” to be transmitted between a user (e.g., subject 70), processor 60, and / or other components of system 100. As another example, sleep stages, sleep time, respiratory characteristic distribution, therapy information feedback, subject 70's respiration rate, and / or other information may be displayed to a user (e.g., subject 70) via user interface 120. Examples of interface devices suitable for inclusion in user interface 120 include keypads, buttons, switches, keyboards, knobs, levers, display screens, touch screens, speakers, microphones, indicator lights, audible alarms, printers, tactile feedback devices, and / or other interface devices. In one embodiment, user interface 120 includes multiple separate interfaces.

[0040]

[45] It should be understood that other communication techniques, either hardwired or wireless, are also contemplated by the present disclosure as user interface 120. For example, the present disclosure contemplates user interface 120 being integrated with a removable storage interface provided by electronic storage 130. In this example, information is loaded into system 100 from a removable storage device (e.g., a smart card, flash drive, removable disk, etc.) that allows a user to customize the implementation of system 100. Other exemplary input devices and techniques adapted for use with system 100 as user interface 120 include, but are not limited to, an RS-232 port, an RF link, an IR link, a modem (telephone, cable, or other). In short, any technique for communicating information with system 100 is contemplated by the present disclosure as user interface 120.

[0041]

[46] In some embodiments, electronic storage 130 includes an electronic storage medium that electronically stores information. The electronic storage medium of electronic storage 130 includes one or both of a system storage device provided integrally (i.e., substantially non-removably) with system 100 and / or a removable storage device removably connectable to system 100 via, for example, a port (e.g., a USB port, a FireWire port, etc.) or a drive (e.g., a disk drive, etc.). Electronic storage 130 includes one or more of an optically readable storage medium (e.g., an optical disk, etc.), a magnetically readable storage medium (e.g., a magnetic tape, a magnetic hard drive, a floppy drive, etc.), a charge-based storage medium (e.g., an EEPROM, RAM, etc.), a solid-state storage medium (e.g., a flash drive, etc.), and / or other electronically readable storage medium. Electronic storage 130 stores software algorithms, information determined by processor 60, information received via user interface 120, and / or other information that enables system 100 to function properly. The electronic storage 130 may be (in whole or in part) a separate component within the system 100, or the electronic storage 130 may be provided (in whole or in part) integrally with one or more other components of the system 100 (e.g., the user interface 120, the processor 60, etc.).

[0042]

[47] Network 150 may include the Internet and / or other networks, intranets, PANs (personal area networks), LANs (local area networks), WANs (wide area networks), SANs (storage area networks), MANs (metropolitan area networks), local area networks (RF) links, Bluetooth, Wi-Fi, Li-Fi, cellular networks, public switched telephone networks, and / or any type of wired or wireless network. This is not intended to be limiting, and it will be understood that the scope of the present disclosure includes embodiments in which components of system 100 are operatively linked via some other communications medium. In some cases, the network is a secure local area network, such as a wired Ethernet network behind a firewall.

[0043]

[48] ​​Information determined by processor 60 and / or stored by electronic storage 130 includes information related to sensor measurements, subject 70's respiration, metabolic rate, feedback, and / or other information. Information stored by electronic storage 130 can be viewed through user interface 120, by connecting to another computer (wired and / or wirelessly) and / or via other methods. Information stored by electronic storage 130 can be used, for example, to adjust treatment settings, for use by a physician to make medical decisions, and / or for other uses. In some embodiments, system 100 includes a wireless transmitter (not shown), and information determined by processor 60, information stored by electronic storage 130, and / or other information can be communicated to a caregiver, for example, via a wireless network. As a non-limiting example, the caregiver can receive usage information, the subject's condition, and / or other information, allowing the caregiver to remotely track the treatment provided by system 100.

[0044]

[49] In some embodiments, the processing functions of system 100 described herein are accomplished locally in a treatment device (e.g., a sensor, a respiratory treatment device, etc.) that includes the components of system 100 described above. In some embodiments, the processing functions of system 100 described herein are accomplished external to system 100 (e.g., remotely by one or more devices connected to system 100 via network 100). In some embodiments, the processing functions described herein are a combination of locally and remotely performed processing functions.

[0045]

[50] Figure 5 illustrates a method 500 for overnight metabolic monitoring. The operations of method 500 described below are for illustrative purposes. In some embodiments, method 500 is accomplished with one or more additional operations not described and / or without one or more of the operations discussed. Additionally, the order in which the operations of method 500 are illustrated in Figure 5 and described below is not intended to be limiting.

[0046]

[51] In some embodiments, method 500 is implemented in one or more processing devices (e.g., digital processors, analog processors, digital circuits designed to process information, analog circuits designed to process information, state machines, and / or other mechanisms for electronically processing information). The one or more processing devices include one or more devices that perform some or all of the operations of method 500 in response to instructions being electronically stored on an electronic storage medium. The one or more processing devices include one or more devices configured with hardware, firmware, and / or software specifically designed to perform one or more operations of method 500.

[0047]

[52] In operation 502, breathable gas is delivered to the nasal airways of subject 70. In some embodiments, operation 502 is performed by a subject interface the same as or similar to subject interface 90 (shown in FIG. 1 and described herein).

[0048]

[53] In operation 504, exhaled breath is collected from the nasal airway. In some embodiments, operation 504 is performed by a subject interface the same as or similar to subject interface 90 (shown in FIG. 1 and described herein). In operation 506, at least a portion of the exhaled breath is collected. In some embodiments, operation 506 is performed by a mixing chamber the same as or similar to mixing chamber 30 (shown in FIG. 1 and described herein).

[0049]

[54] In operation 508, output signals related to one or more gas parameters related to inspiration and expiration by the subject during one or more breaths are received. In some embodiments, operation 508 is performed by multiple sensors the same as or similar to sensor 40 (shown in FIG. 1 and described herein).

[0050]

[55] In operation 510, the flow rate of gas at the subject interface during one or more breaths is determined based on the output signal. In some embodiments, operation 510 is performed by a physical computer processor that is the same as or similar to processor 60 (shown in FIG. 1 and described herein). In operation 512, pressure changes near the subject's mouth during one or more breaths are determined based on the signal output from the sensor to detect mouth breathing of the subject. In some embodiments, operation 512 is performed by a physical computer processor that is the same as or similar to processor 60 (shown in FIG. 1 and described herein).

[0051]

[56] In operation 514, O2 and CO2 concentration measurements of the portion of the exhaled gas in the mixing chamber are determined based on the signals output from the sensors. Concentration measurements corresponding to mouth breathing are discarded. In some embodiments, operation 514 is performed by a physical computer processor the same as or similar to processor 60 (shown in FIG. 1 and described herein).

[0052]

[57] At operation 516, the ratio of the subject's oxygen consumption, VO2, to carbon dioxide production, VCO2, is determined. In some embodiments, the ratio of the subject's oxygen consumption, VO2, to carbon dioxide production, VCO2, is determined based on the measured gas flow rate, the determined carbon dioxide concentration of the exhaled gas in the mixing chamber, and the determined oxygen concentration of the exhaled gas in the mixing chamber. In some embodiments, operation 516 is performed by a physical computer processor that is the same as or similar to processor 60 (shown in FIG. 1 and described herein).

[0053]

[58] In the claims, any reference signs placed between parentheses shall not be construed as limiting the scope of the claim. The word "comprises" or "includes" does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word "a" or "an" does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination.

[0054]

[59] While the foregoing description provides details for illustrative purposes, based on what are presently believed to be the most practical and preferred embodiments, it should be understood that such details are for that purpose only, and that the disclosure is not limited to the expressly disclosed embodiments, but on the contrary, is intended to cover modifications and equivalent arrangements within the spirit and scope of the appended claims. For example, it should be understood that the present disclosure contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.

Claims

1. 1. A system for metabolic monitoring, said system comprising: an interface device that collects exhaled breath from the subject's nasal airway; a mixing chamber operatively connected to the interface device, the mixing chamber receiving at least a portion of the exhaled air from the interface device; a plurality of sensors that output signals related to one or more gas parameters associated with inspiration and expiration by the subject during one or more breaths; and one or more physical computer processors operatively connected to the sensor to receive the output signal, the one or more physical computer processors comprising: determining a flow rate of gas through the interface device during one or more of the breaths based on the signal output from the sensor; determining a pressure change near the subject's mouth during one or more of the breaths based on the signal output from the sensor to detect mouth breathing of the subject; determining O2 and CO2 concentration measurements of the portion of the exhaled gas in the mixing chamber based on the signal output from the sensor, and discarding concentration measurements from among the determined concentration measurements when it is determined that the breathing includes mouth breathing; 10. A system configured with computer-readable instructions to determine a ratio of oxygen consumption VO2 to carbon dioxide production VCO2 of the subject based on the determined flow rate of the gas, the determined carbon dioxide concentration of the exhaled gas in the mixing chamber, and the determined oxygen concentration of the exhaled gas in the mixing chamber.

2. 10. The system of claim 1, wherein the one or more physical computer processors determine a metabolic state of the subject based on the determined oxygen consumption rate VO2 and the carbon dioxide production rate VCO2.

3. The one or more physical computer processors may calculate the determined oxygen consumption VO ２ and the carbon dioxide production amount VCO ２ The system of claim 1 , wherein the system calculates energy expenditure and / or respiratory quotient based on:

4. The system of claim 1 , wherein the interface appliance seals the subject's nasal passages from the atmosphere.

5. The system of claim 1 , wherein the system monitors the subject's metabolism while the subject is inactive.

6. 2. The system of claim 1, wherein the sensor includes a pressure sensor positioned near the subject's mouth, the pressure sensor outputting a pressure signal related to the pressure near the subject's mouth, and the concentration measurements of O2 and CO2 are discarded based on the pressure signal output from the pressure sensor.

7. The system of claim 1 , wherein the interface appliance provides breathable gas to the nasal airways of the subject.

8. 1. A method of operating a system for metabolic monitoring, the system comprising: an interface device that collects exhaled breath from a subject's nasal airway; a mixing chamber operatively connected to the interface device; a plurality of sensors; and one or more physical computer processors operatively connected to the sensors; The method comprises: collecting exhaled breath from the subject's nasal airway with the interface device; the mixing chamber receiving at least a portion of the exhaled air from the interface appliance; the plurality of sensors outputting output signals related to one or more gas parameters associated with inspiration and expiration by the subject during one or more breaths; determining, by the one or more physical computer processors, a flow rate of gas at a subject interface during one or more of the breaths based on the output signal from the sensor; determining, by the one or more physical computer processors, a change in pressure near the subject's mouth during one or more of the breaths based on the output signal from the sensor to detect mouth breathing of the subject; determining, by the one or more physical computer processors, O2 and CO2 concentration measurements of the portion of the exhaled gas in the mixing chamber based on the output signals from the sensors, and discarding from among the determined concentration measurements, concentration measurements where breathing is determined to include mouth breathing; and determining, by the one or more physical computer processors, a ratio of oxygen consumption VO2 to carbon dioxide production VCO2 of the subject based on the determined flow rate of the gas, the determined carbon dioxide concentration of the exhaled gas in the mixing chamber, and the determined oxygen concentration of the exhaled gas in the mixing chamber.

9. The one or more physical computer processors are configured to: ２ and the carbon dioxide production amount VCO ２ 9. The method of claim 8, further comprising determining a metabolic state of the subject based on:

10. The method of claim 8, further comprising the step of the one or more physical computer processors calculating energy expenditure and / or respiratory quotient based on the determined oxygen consumption rate VO2 and carbon dioxide production rate VCO2.

11. The method of claim 8 , further comprising the step of the interface appliance sealing the subject's nasal passages from the atmosphere.

12. 10. The method of claim 8, further comprising the step of the one or more physical computer processors monitoring the metabolism of the subject while the subject is inactive.

13. 10. The method of claim 8, further comprising: a pressure sensor positioned near the subject's mouth outputting an output signal related to pressure near the subject's mouth; and wherein the O2 and CO2 concentration measurements are discarded based on the pressure-related output signal output from the pressure sensor.

14. 10. The method of claim 8, further comprising the step of the interface appliance providing breathable gas to the nasal airways of the subject.

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