# US 2026/0061145 A1 · Carbon-dioxide and Oxygen Respiratory Ventilator Energy Tracker (CORVET) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0061145 A1 - Document ID: US20260061145A1 - Status: Published application - Kind: A1 - Application number: 18/405,392 - Filed: 2024-01-05 - Published: 2026-03-05 - Earliest claimed: 2023-03-07 - Assignees: Massachusetts Institute of Technology; Koninklijke Philips N.V. - Applicants: Massachusetts Institute of Technology - Inventors: Gary A Shaw; Lawrence M Candell; Kyle THOMPSON; Allison Norloff; Donald Johnson; Roberto Buizza; Francesco Vicario - Web page: https://patentgrep.com/patent/US20260061145A1 ## CPC - A61B 5/082: {Evaluation by breath analysis, e.g. determination of the chemical composition of exhaled breath (A61B5/083, A61B5/091 take precedence)} - A61M 16/024: {including calculation means, e.g. using a processor} - A61B 5/0833: {Measuring rate of oxygen consumption} - A61M 16/0003: {Accessories therefor, e.g. sensors, vibrators, negative pressure} - A61M 16/085: {Gas sampling} - A61M 16/0875: {Connecting tubes} - A61M 16/12: by mixing different gases - A61M 16/203: {Proportional} - A61M 39/223: {Multiway valves} - G01N 33/497: of gaseous biological material, e.g. breath - A61M 16/0833: {T- or Y-type connectors, e.g. Y-piece} - A61M 16/161: {with means for measuring the humidity} - A61M 2016/0039: {in the inspiratory circuit} - A61M 2016/0042: {in the expiratory circuit} - A61M 2016/1025: {the O2 concentration} - A61M 2016/103: {the CO2 concentration} - A61M 2202/0007: introduced into the body - A61M 2202/0208: Oxygen - A61M 2205/3327: Measuring - A61M 2205/3334: Measuring or controlling the flow rate - A61M 2205/3368: Temperature - A61M 2205/3379: Masses, volumes, levels of fluids in reservoirs, flow rates - A61M 2205/50: with microprocessors or computers - A61M 2230/42: Rate - A61M 2230/432: partial CO2 pressure (P-CO2) - A61M 2230/435: partial O2 pressure (P-O2) - G01N 33/0006: {Calibrating gas analysers} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A respiratory monitoring system with improved detection of oxygen consumption is described. The system uses one or two mixing chambers and samples gases at selective locations for reliable detection of oxygen over extended periods of time with autonomous detection of calibration drift. The system can be used for indirect calorimetry and monitoring health of a subject. ## Claims ### Claim 1 A respiratory monitoring system comprising: a first multi-way valve; a mixing chamber having an input port fluidically coupled to the first multi-way valve; an oxygen sensor coupled to the mixing chamber; an inhalation input-sampling flow line fluidically coupled at a first end to the first multi-way valve and to fluidically couple at a second end to an inhalation line that is fluidically coupled to breathing apparatus for a subject; and an exhalation input-sampling flow line fluidically coupled at a first end to the first multi-way valve and to fluidically couple at a second end to an exhalation line that is fluidically coupled to the breathing apparatus for the subject, wherein the first multi-way valve is configured to switch coupling of the input port of the mixing chamber between a first configuration where the input port is fluidically coupled to the inhalation input-sampling flow line and a second configuration where input port is fluidically coupled to the exhalation input-sampling flow line. ### Claim 2 (depends on 1) The respiratory monitoring system of claim 1, further comprising: a second multi-way valve fluidically coupled to an output port of the mixing chamber; a first output flow line fluidically coupled at a first end to the second multi-way valve and to fluidically couple at a second end to the inhalation line; and a second output flow line fluidically coupled at a first end to the second multi-way valve and to fluidically couple at a second end to the exhalation line. ### Claim 3 (depends on 2) The respiratory monitoring system of claim 2, wherein the first multi-way valve is a four-way valve and the second multi-way valve is a three-way valve. ### Claim 4 (depends on 1) The respiratory monitoring system of claim 1, further comprising: a carbon dioxide sensor coupled to the mixing chamber to measure a concentration of carbon dioxide in gas contained in the mixing chamber; a relative humidity sensor coupled to the mixing chamber to measure a water vapor content of the gas contained in the mixing chamber; and a temperature sensor coupled to the mixing chamber to measure a temperature of the gas contained in the mixing chamber. ### Claim 5 (depends on 1) The respiratory monitoring system of claim 1, wherein the mixing chamber is a first mixing chamber, the oxygen sensor is a first oxygen sensor, and the input port is a first input port, the respiratory monitoring system further comprising: a second mixing chamber having a second input port fluidically coupled to the first multi-way valve; and a second oxygen sensor coupled to the second mixing chamber, wherein the first multi-way valve is further configured to switch coupling of the first input port between the first configuration where the first input port is fluidically coupled to the inhalation input-sampling flow line and the second input port is fluidically coupled to the exhalation input-sampling flow line and a second configuration where first input port is fluidically coupled to the exhalation input-sampling flow line and the second input port is fluidically coupled to the inhalation input-sampling flow line. ### Claim 6 (depends on 1) The respiratory monitoring system of claim 1, further comprising: a passive flow divider coupled to the exhalation input-sampling flow line and to couple to the exhalation line, wherein the passive flow divider is configured to provide sampled gas from the exhalation line at a flow rate that is proportional to a flow rate of exhaled gas in the exhalation line. ### Claim 7 (depends on 6) The respiratory monitoring system of claim 6, wherein, during operation of the respiratory monitoring system, a volume of gas provided to the mixing chamber from the passive flow divider during an exhalation phase of a breath cycle of the subject is less than one-half the volume of the mixing chamber such that the gas in the mixing chamber sampled by the oxygen sensor represents a physical average of samples of exhalation gas from the subject over multiple respiratory cycles. ### Claim 8 (depends on 6) The respiratory monitoring system of claim 6, further comprising: the exhalation line; and a flow sensor to sample gas flow rate in the exhalation line, wherein the passive flow divider is coupled to the exhalation line at a location upstream of the flow sensor and a distance no less than three feet from the subject. ### Claim 9 (depends on 8) The respiratory monitoring system of claim 8, wherein the exhalation line has interior ribbing and/or protruding features to mix gas flowing within the exhalation line. ### Claim 10 (depends on 1) The respiratory monitoring system of claim 1, further comprising: a system controller communicatively coupled to the oxygen sensor and configured to: determine a first concentration of oxygen in the inhalation line based at least in part on a first signal received from the oxygen sensor detecting gas received in the mixing chamber by way of the inhalation input-sampling flow line; determine a second concentration of oxygen in the exhalation line based at least in part on a second signal received from the oxygen sensor detecting gas received in the mixing chamber by way of the exhalation input-sampling flow line; and compute a value relevant to the health of the subject based at least in part on a difference between the first concentration of oxygen and the second concentration of oxygen. ### Claim 11 (depends on 10) The respiratory monitoring system of claim 10, wherein the value is a volume rate of oxygen consumed by the subject. ### Claim 12 (depends on 1) The respiratory monitoring system of claim 1, wherein the mixing chamber has a volume no larger than 50 ml. ### Claim 13 A method of respiratory monitoring with a respiratory monitoring system, the method comprising: during a first interval of time, receiving inhalation gas for a subject in a mixing chamber, wherein the inhalation gas is sampled from an inhalation line of the respiratory monitoring system and the inhalation line connects to breathing apparatus used by the subject; detecting a first concentration of oxygen in the mixing chamber with an oxygen sensor during the first interval of time; changing, with a multi-way valve, coupling of an input port of the mixing chamber from being fluidically coupled to the inhalation line to being fluidically coupled to an exhalation line of the respiratory monitoring system; during a second interval of time, receiving exhalation gas from the subject in the mixing chamber, wherein the exhalation gas is sampled from the exhalation line and the exhalation line is coupled to the breathing apparatus; detecting a second concentration of oxygen in the mixing chamber with the oxygen sensor during the second interval of time; and computing a value relevant to health of the subject based at least in part on a difference between the first concentration of oxygen and the second concentration of oxygen. ### Claim 14 (depends on 13) The method of claim 13, further comprising: coupling an output port of the mixing chamber to the inhalation line; providing a portion of the inhalation gas received in the mixing chamber to the inhalation line during the first interval of time; coupling the output port of the mixing chamber to the exhalation line; and providing a portion of the exhalation gas received in the mixing chamber to the exhalation line during the second interval of time. ### Claim 15 (depends on 14) The method of claim 14, wherein an amount of exhalation gas received in the mixing chamber from the subject during an exhalation phase of a respiratory cycle of the subject is less than one-half the volume of the mixing chamber, such that the mixing chamber physically averages samples of exhalation gas from the subject over multiple respiratory cycles. ### Claim 16 (depends on 14) The method of claim 14, further comprising: during the first interval of time, determining that a concentration of carbon dioxide gas in the mixing chamber reduces to at least a predetermined value before changing from coupling the output port of the mixing chamber to the exhalation line to coupling the output port of the mixing chamber to the inhalation line. ### Claim 17 (depends on 14) The method of claim 14, wherein the mixing chamber is a first mixing chamber, the oxygen sensor is a first oxygen sensor, the input port is a first input port, and the output port is a first output port, the method further comprising: during a third interval of time, receiving exhalation gas from the subject in a second mixing chamber, wherein the exhalation gas is sampled from the exhalation line of the respiratory monitoring system; and detecting a third concentration of oxygen in the second mixing chamber with a second oxygen sensor during the third interval of time, wherein the value relevant to the health of the subject is further based in part on the third concentration of oxygen. ### Claim 18 (depends on 17) The method of claim 17, further comprising: comparing, by a system controller, first data obtained from the first oxygen sensor to second data obtained from the second oxygen sensor to determine whether a first calibration of the first oxygen sensor or a second calibration of the second oxygen sensor has changed; and in response to one of the first calibration or the second calibration changing by more than a threshold amount, ignoring subsequent data obtained from the first oxygen sensor or the second oxygen sensor for which the first calibration or the second calibration has changed more than the threshold amount. ### Claim 19 (depends on 18) The method of claim 18, wherein in response to both the first calibration and the second calibration changing by less than the threshold amount, the value relevant to the health of the subject is computed with an averaging computation that includes the first concentration of oxygen, the second concentration of oxygen, and the third concentration of oxygen. ### Claim 20 (depends on 17) The method of claim 17, further comprising: maintaining respiratory monitoring of the subject with one of the first mixing chamber or the second mixing chamber; and servicing the other of the first mixing chamber or the second mixing chamber without disrupting respiratory monitoring of the subject and without disrupting airflow in the inhalation line and exhalation line to and from the subject.