WO2004041084A1 - Calorimetre indirect - Google Patents

Calorimetre indirect Download PDF

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Publication number
WO2004041084A1
WO2004041084A1 PCT/US2003/035428 US0335428W WO2004041084A1 WO 2004041084 A1 WO2004041084 A1 WO 2004041084A1 US 0335428 W US0335428 W US 0335428W WO 2004041084 A1 WO2004041084 A1 WO 2004041084A1
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WO
WIPO (PCT)
Prior art keywords
user
exhalation
exhalation gas
metabolic rate
measuring
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PCT/US2003/035428
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English (en)
Inventor
Craig Thomas Flanagan
Original Assignee
Craig Thomas Flanagan
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Application filed by Craig Thomas Flanagan filed Critical Craig Thomas Flanagan
Priority to AU2003291343A priority Critical patent/AU2003291343A1/en
Publication of WO2004041084A1 publication Critical patent/WO2004041084A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/41—Detecting, measuring or recording for evaluating the immune or lymphatic systems
    • A61B5/412—Detecting or monitoring sepsis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/083—Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
    • A61B5/0833—Measuring rate of oxygen consumption
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/097—Devices for facilitating collection of breath or for directing breath into or through measuring devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/483—Physical analysis of biological material
    • G01N33/497—Physical analysis of biological material of gaseous biological material, e.g. breath

Definitions

  • This invention is in the field of Indirect Calorimeters for measuring Resting Metabolic Rate (RMR), oxygen consumption (VO2), and related respiratory parameters.
  • Indirect calorimetry is a method by which nutritional substrate utilization and heat production are measured in vivo starting from gas exchange measurements. Specifically " indirect calorimetry is useful in calculating the resting metabolic rate (RMR) or the caloric intake of an individual at rest. Indirect Calorimetry first proved its value in a clinical setting, where it allowed physicians to obtain a direct assessment of the metabolic state of a patient undergoing mechanical ventilation therapy for prescription of the proper amount and makeup of parenteral nutritional support.
  • Proper nutrition is important to the critically ill patient population. Improper patient nutrition has been associated with poor clinical outcome. Specifically, overfeeding can produce hyperglycemia and fatty infiltration producing liver dysfunction as well as respiratory acidosis/hypercapnia which are associated with ventilator weaning difficulties. Underfeeding can depress the immune response and lead to loss of lean body mass.
  • the RMR component is generally about 60-70% of TEE.
  • 6,616,615 teaches a respiratory calorimeter which uses a capnometer.
  • Mault's Patent Nos. 6,402,698 and 6,468,222 involve indirect calorimeters in which both inhaled and exhaled flow are directed through a single flow tube.
  • Bi-directional flow transducers measure the flow in each direction and gas composition is determined by sensors in commumcation with the bi-directional flow tube. All of the Mault patents and methods for determination of RMR are based on measurements made during both inhalation and exhalation and require a flow path used for both inhalation and exhalation.
  • Patent Nos. 5,285,794 to Lynch and 6,475,158 to Orr and Kofoed use unidirectional flow of only exhaled gas through their devices.
  • Mixing chambers are used in these devices to mix and equilibrate or average exhaled air from each exhalation. This averaging is necessary in their devices to obtain desired RMR measurements.
  • the addition of these mixing chambers makes their devices bulky which is a disadvantageous in a small handheld device.
  • a system for the determination of the metabolic rate of an individual uses separate inhalation and exhalation flow pathways with a unidirectional flow of exhalation gas in the exhalation pathway.
  • a flow sensor disposed in the exhalation flow pathway measures instantaneous exhalation gas flow through the pathway and transduces the instantaneous exhalation gas flow measurement into electrical signals representative of the instantaneous exhalation gas flow.
  • the system incorporates an oxygen sensor disposed to measure the instantaneous oxygen content of the exhalation gas in the exhalation pathway. The oxygen sensor transduces the oxygen measurement into electrical signals representative of the oxygen content measured. Because instantaneous oxygen measurements are used, no mixing chamber is necessary and the exhalation flow pathway is configured to minimize any mixing or averaging of the exhalation gas until after the desired measurements are made.
  • the exhalation gas flow and the oxygen sensors produce an adequate amount of information for a mathematical algorithm to calculate the volumetric oxygen consumption of a user breathing through the device, and from this the RMR can be determined.
  • An algorithm based on a modified Haldane Transform has been found satisfactory to calculate the RMR of a user from only exhalation flow rate and exhalation gas oxygen content measurements, and to do so with more tolerance of flow transducer zero and gain errors, and thus with more accuracy, than in currently available indirect calorimeter measurement systems.
  • the algorithm is -implemented -in a microprocessor- system -in commumcation with each of .the -sensors.
  • the results of calculations performed by the microprocessor using the algorithm are displayed for the user via a graphical display.
  • Additional sensors to determine additional desired parameters such as ambient and/or airway humidity, ambient and/or airway temperature, and ambient pressure, may be included in the device. Incorporation of such additional measurements into the calculations of some of the calculated parameters, such as RMR, will increase the accuracy of those calculated parameters.
  • a preferred indirect calorimetry system of the invention includes a handheld device having an exhalation gas inlet and exhalation gas outlet with an exhalation gas pathway extending between the inlet and outlet.
  • a facemask or mouthpiece is removably secured in the inlet to direct the exhalation gas from a user into the inlet of the device.
  • the exhalation gas pathway has a gas flow sensor therein to measure the instantaneous gas flow through the pathway and has an oxygen sensor in flow communication with the pathway to measure the instantaneous oxygen content of the gas passing through the pathway.
  • a measurement pathway which includes the oxygen sensor therein, is provided in flow communication with the exhalation gas pathway.
  • a vacuum pump draws exhalation gas from the exhalation gas pathway through a drying tube, the oxygen sensor, and a flow restrictor and pneumatic accumulator which together ensure a constant flow rate through the measurement pathway.
  • a three way valve is preferably included in the measurement pathway upstream of the oxygen sensor which selectively connects the measurement pathway to the exhalation gas pathway for measurement of the oxygen content of the exhalation gas passing through the exhalation gas pathway or to the atmosphere to pull atmospheric air through the oxygen sensor for calibration of the oxygen sensor.
  • the face mask is designed for single use and means may be provided, such as a bar code placed on a portion of the face mask that is inserted into the inlet of the-device in combination with a bar code reader in the inlet of the device to read the bar code, to ensure that a particular face mask is used only once.
  • the device preferably includes a display to display the measurements obtained and calculated by the device to the user.
  • FIG. 1 is a perspective view of an embodiment of an indirect calorimetry system of the invention, showing a facemask engaged with and extending from the body of the device;
  • FIG. 2 a perspective view of the device showing the top portion of the body separated from the bottom portion so that interior components are visible;
  • FIG. 3 a perspective view of the device similar to that of FIG. 2, but from the opposite side;
  • FIG. 4 a perspective view of the disposable facemask for use with the embodiment of FIG. 1;
  • FIG. 5 a perspective view from a different angle of the disposable facemask of FIG. 4;
  • FIG. 6, a block diagram of the signal processing portion of the system; and FIG. 7, a flow diagram of the exhalation gas pathway and measurement pathway of the system.
  • the Haldane Transform provides the foundation for the algorithmic approach used in this invention. Such a mathematical derivation is repeated below:
  • VT Volume of inspired air in ml (STPD - standard temperature (0°C), standard pressure pressure (760 mmHg), dry (0% relative humidity).
  • V E Volume of expired air in ml (STPD).
  • Vi V E *(1 -F E O 2 - F E CO 2 )/(l -F ⁇ O 2 ) (1.4)
  • Equation 1.4 can be plugged into Equation 1.1. to yield the Haldane , _ ___
  • This equation yields oxygen consumption.
  • the Weir Equation is as follows:
  • Vi Volume of inspired air in ml (STPD - standard temperature (0°C), standard pressure (760 m Hg), dry (0% relative humidity).
  • V E Volume of expired air in ml (STPD).
  • VO 2 mis of O 2 removed from Vi in lung (STPD).
  • V ⁇ f( ⁇ *V E ) (1.8)
  • VN 2 V E - V E CO 2 - V E O 2 (1.10)
  • VN 2 VE - V E CO 2 - V E O 2 (1.11)
  • VI V E - (1-RQ ⁇ VO 2 (1.13)
  • Vi V E - (l-RQ)*V E *( ⁇ *F,O 2 - F E O 2 ) (1.14)
  • Equation 1.6 can be used to estimate RMR given a starting estimate of RQ to obtain the VCO 2 required for this equation.
  • Expression 1.14 is the expression we will use to eliminate the need for inspiratory flow/volume determination and, by extension, the need to monitor inhalation breath parameters on the device. Thus, the device does not need to sense gas volume or gas concentration during the inspiratory phase of breathing. The above equations are used as follows:
  • the device measures the instantaneous partial pressure of oxygen during exhalation and instantaneous value of flow and the algorithm flow averages these values to obtain PEO 2 (or the average partial pressure of oxygen during exhalation). 2.
  • the device either measures the current barometric pressure using an on-board barometric pressure transducer (use of such a transducer is currently preferred) or estimates the barometric pressure using an altitude value inputted by the user. This barometric pressure is used to convert partial pressures of oxygen to fractions of oxygen as follows:
  • FEO 2 PE ⁇ 2 /PBarometric 3.
  • the device measures the fraction of inspired oxygen, F ⁇ O 2; by obtaining the partial pressure of oxygen at the beginning of exhalation and assuming, since no gas consumption has occurred in this airway gas, that it is equal to the partial pressure of ambient oxygen (such an assumption is very accurate).
  • the partial pressure is then divided by current barometric pressure as in step 2:
  • F ⁇ O 2 PE ⁇ 2 Begir-ning of Exhalation/ PBarometric
  • RQ is assumed to be a typical clinical value of ⁇ 0.8 because, in this device as with other indirect calorimetry devices, carbon dioxide volume (VCO ) necessary for RQ calculation tends to require a long measurement duration before stability can be assumed, and errors in this parameter do not contribute significantly to overall algorithm error. Therefore the value of carbon dioxide volume is rarely measured in practice.
  • VCO carbon dioxide volume
  • VT Once VT has been determined, it can be plugged into 1.15 to obtain VO 2 . This VO 2 can in turn be plugged into the Weir Equation to obtain RMR.
  • an ambient humidity sensor can be used, and is used in preferred embodiments of the invention.
  • the ambient humidity sensor is used to determine the water vapor pressure in the inhaled gas stream.
  • a determination of inhaled gas stream humidity is required to make correction for changes in water vapor content between the inhaled and exhaled breathing gas.
  • exhaled gas humidity is assumed to be at a relative humidity of 100% (and at a temperature slightly below body temperature or approximately 36°C).
  • an exhalation gas humidity sensor which would be located in the exhalation gas pathway could also be used, but the inventor is not currently aware of an inexpensive and robust sensor that can be used as an exhalation gas humidity sensor. Advances in micro-machined electro-mechanical device technologies (MEMS) may make such a sensor available in the next few years. Such a sensor would improve estimates of water vapor content of the exhaled gas and thereby improve overall algorithm/device accuracy.
  • An exhalation gas temperature sensor could also be used in the future in conjunction with the exhalation gas humidity sensor for determining real time, intra- breath values of relative humidity. The determination of the relative humidity of a gas requires both gas temperature and absolute humidity readings.
  • a preferred embodiment of the invention includes an ambient temperature sensor.
  • Integration-type algorithm which is based on a comparison of inhalation and exhalation gas parameters, is commonly used in practice in prior art systems.
  • Such an algorithm will be termed an "Integration Algorithm" for sake of discussion in this patent.
  • Integration Algorithms are mentioned as being preferentially used by Mault in patents such as No. 6,402,698, and are based on the following mathematical expression:
  • This VO 2 value can then be plugged into further mathematical expressions such as the Weir, described herein, to obtain RMR. It is clear upon inspection of the terms of this Integration Algorithm that implementation of such an Integration Algorithm requires sensor-based information on inhalation flow.
  • the Modified Haldane Transform provides a significant computational benefit over the Integration Algorithm. Specifically, implementation of a device using this Modified Haldane Transform results in improved algorithm accuracy in the setting of flow transducer zero and gain errors. Such errors are an unavoidable fact in practical application of such sensor-based systems.
  • the following Table shows the results of calculations made on a spreadsheet given increasing errors in flow transducer gain. The table shows that transducer gain significantly affects the accuracy of the VO 2 readings of the algorithm as determined by the Integration Algorithm. Errors in VO 2 readings propagate though the subsequent mathematical formulations (such as the Weir Equation) used by prior art devices thus affecting the ultimate calculation accuracy of resting metabolic rate.
  • the indirect calorimeter indicated generally as 10, Figs. 1-3, includes an exhalation gas pathway therethrough with an inlet 14 and outlet 16.
  • the calorimeter body includes an upper body portion 17 and a lower body portion 18.
  • a flip up screen 19, with a graphic or alphanumeric display 20, can be closed when the device is not in use by pivoting the screen 20 down into a receiving recess 21 in the upper body portion 17, as shown in Fig. 3.
  • a power switch 22 can be pressed to initiate power-up of the device, i.e., to turn "on" the device.
  • LED 24 indicates when the device is connected to a source of AC power and LED 25 indicates when the device is turned “on.”
  • a rotary selector switch 26 with built in “press switch,” such as a Grayhill 61 C series switch, allows the user to rotate the switch knob to select the desired operation of the device or to input information into the device and to confirm the desired selection by pressing the knob to activate the "press switch” which enters the information. While the rotary switch with press switch is currently preferred, other arrangements such as separate selection and confirmation switches can be used.
  • a user exhales into the inlet 14 of the exhalation air pathway through the device. It is important that the entire exhaled breath of the user pass through the exhalation gas pathway.
  • the inlet 14 to the exhalation gas pathway is coupled to a user's mouth by a face mask 28, Fig. 1, or by other suitable mouthpiece so that as a user exhales, the entire exhaled breath is directed into the inlet 14 of the exhalation air pathway.
  • the face mask or other suitable mouthpiece will also include an inlet for atmospheric air for inhalation by the user so that the user can easily inhale and exhale while using the device with the exhaled breath directed into inlet 14 of the device. Figs.
  • the exhalation gas flow pathway through the device extends from exhalation gas inlet 14 to exhalation gas outlet 16, and includes inlet tube 30 positioned in exhalation gas inlet 14 to receive the exhalation gas outlet of face mask 28 thereover.
  • An O-ring may be positioned in groove 31 of inlet tube 30 to seal the connection to the face mask.
  • the inlet tube 30, after several bends, connects to a flow sensor 32 . which measures the real time or instantaneous flow of exhalation gas through the flow sensor 32, which is the same as the flow of exhalation gas through the exhalation gas flow pathway.
  • a heated screen element differential pressure transducer similar in construct to a Hans Rudolph Model 8300 works well as the flow sensor and is currently preferred, although other types of flow sensors can also be used.
  • the flow sensor produces an electrical signal representative of the measured instantaneous flow of exhalation gas through the sensor, which is also a measure of the instantaneous gas flow through the exhalation gas pathway.
  • Exit tube 33 extends from the outlet of flow sensor 32 and after several bends, discharges the exhalation gas to the atmosphere through exhalation gas outlet 16.
  • a measurement flow pathway extends from an inlet tube 35 in gas flow communication with the exhalation gas flow pathway, here shown as communication with exit tube 33, to a measurement pathway outlet 36.
  • Inlet tube 35 may be a length of Nafion tubing which connects the exhalation gas pathway to an inlet of an electrically operated three way valve 37.
  • the Nafion tube dries the exhalation gas drawn into the measurement pathway before it reaches the oxygen sensor.
  • a second inlet of the three way valve 37 communicates with the atmosphere through inlet 38.
  • Tube 39 connects the outlet of the three way valve 37 to oxygen sensor 40.
  • the presently preferred oxygen sensor is a cylindrical fast fuel cell (Galvanic) oxygen sensor, such as a Teledyne UFO-130.
  • Other types of oxygen sensors may be used, such as paramagnetic oxygen sensors, for example fast acoustic paramagnetic sensors as manufactured by Datex of Helsinki, Finland.
  • the oxygen sensor produces an electrical signal representative of the measured instantaneous partial pressure of oxygen of gas passing through the sensor.
  • Tube 41 extends from oxygen sensor 40 to flow restrictor 42 connected by tube 43 to pneumatic accumulator 44.
  • Tube 45 connects pneumatic accumulator 44 to vacuum pump 46 which discharges to the atmosphere through outlet 36.
  • Vacuum pump 46 can be any of a number of small DC pumps available today as OEM units, such as a Gast miniature diaphragm 2D series.
  • Three-way valve 37 can switch the inlet for the measurement pathway and oxygen sensor 40 between exhalation gas from the exhalation gas pathway and atmospheric air.
  • Pneumatic accumulator 44 in combination with flow restrictor 42,,form-a..pneumatic damping. system in the measurement pathway. to ..damp out. ump pressure oscillations and provide a constant gas or air flow through the measurement pathway and oxygen sensor 40.
  • Figs. 4 and 5 show a preferred embodiment of disposable face mask 28 for use with the calorimeter of the invention and includes a face mask body 50 configured to fit over the nose and mouth of a user and a mask outlet tube 52.
  • Mask outlet tube 52 is sized to slide over and closely fit over inlet tube 30, Fig. 3, in calorimeter inlet 14, with the connection sealed by an O- ring in inlet tube groove 31.
  • a keyed protrusion 53 on mask outlet tube 52 fits into receiving groove 54, Fig. 3, in calorimeter inlet 14 to ensure that the mask is correctly oriented when mask outlet tube 52 is inserted into calorimeter inlet 14, and that it does not rotate when placed over inlet tube 30.
  • the mask has two one-way check valves 56 and 58. These two check valves ensure that gas enters the mask only through valve 56 on inhalation by the user, and exits the mask only through outlet tube 52 after passing though valve 58 on exhalation by the user.
  • the mask is designed to minimize dead space volume between the inner surface of the mask and the surface of the face.
  • Such a minimization of dead space volume is achieved by inward protrusions 60 which extend inward towards the face to ensure only the nose area and mouth area have a large opening.
  • Such a minimization of dead space volume reduces the amount of CO re-breathed by the user and as a result minimizes the consequent negative effects thereof previously described for two way flow pathways.
  • each face mask may be provided with a bar code indication 61, Fig. 5, placed on a flat area 62 on the top of outlet tube 52.
  • a bar code reader is built into the top of calorimeter inlet 14 as at 63, Fig.
  • a "Single Use" label 64 is preferably located on the front of the mask.
  • the calorimeter includes a microprocessor, Fig. 6, and associated circuitry to process signals from the various sensors and produce desired information therefrom and display that information to a user.
  • the flow sensor and oxygen sensor are connected to the microprocessor.
  • the indicated "microprocessor" block is meant to include not only the microprocessor itself, but all associated circuitry, such as interface circuitry and memory circuitry. Any other sensors, such as the illustrated CO 2 sensor, Barometric Pressure sensor, Temperature sensor, and Humidity sensor are also connected to the microprocessor.
  • the microprocessor processes the signals supplied to it from the sensors and using the "algorithm" as previously described and programmed into the microprocessor, calculates the desired information which is then sent to the display. The calculated information may also be stored by the microprocessor.
  • the circuitry is housed in the calorimeter body in any desired location, such as inside the upper portion of the calorimeter body and is not visible in the drawings.
  • the calorimeter may be battery powered and/or may include a socket 70, Fig. 3, for attachment of a plug from a power jack which allows wall power to be plugged into the device alleviating the necessity for batteries or prolonging the life of batteries when provided.
  • Fig. 7 shows a pneumatic flow schematic of the device indicating the flow pathways of the preferred embodiment.
  • the arrows represent gas flow in direction and width of the arrows gives some indication of degree of volumetric flow.
  • air is draw in through the check valve in the facemask through the ambient gas inlet.
  • gas is exhausted from the outlet of the face mask and through the exhalation gas pathway in the device.
  • the second check valve shown located in the indirect calorimetry device can be either located in the indirect calorimetry device or located in the mask at or near the mask's connection to the indirect calorimetry device. Such location in the mask has been described for the mask of Figs. 4 and 5.
  • a filter is preferably located in the facemask so as to form a biologic barrier between the user and the device to protect the user from infection resulting from device reuse (the facemasks are not reused).
  • a small volumetric stream of exhalation gas is drawn through a pneumatic oxygen sampling system consisting of a Nafion Tube segment to dry the gas (optional), a three-way solenoid valve, a restrictor, an accumulator, and a vacuum gas pump.
  • the three-way valve allows the device to switch (under microprocessor control) between supplying ambient air to the oxygen sensor (path 2 connected to path 3) and supplying exhalation gas to the oxygen sensor (path 1 connected to path 2).
  • ambient atmospheric air passes through the oxygen sensor and can be used to calibrate the sensor to 20.9% oxygen.
  • the purpose of the restrictor and accumulator is to pneumatically damp out pressure oscillations resulting from pump action, thus allowing a smooth and uninterrupted flow of gas though the oxygen sensor.
  • the vacuum pump produces a vacuum in the line proximal to the pump for drawing gas through this measurement pathway.
  • the accumulator is preferentially located distal to the oxygen sensor so as to prevent gas mixing before sampling, thus ensuring a sample representative of exhalation oxygen partial pressure at a given point in time.
  • the oxygen sensor can be placed in the exhalation flow pathway thus eliminating the need for the pump-based sampling system.
  • the exhalation gas does not pass all sensors at the same time.
  • the exhalation gas will pass the flow sensor where the flow measurement is taken and then that gas will flow further through the exhalation gas pathway and a portion of it will flow through the measurement pathway to the oxygen sensor so the oxygen reading for particular gas passing through the flow sensor will be delayed from the flow reading. Therefore, the flow signal from the flow sensor or transducer should be delayed, such as in the algorithm, to appropriately synchronize it with the oxygen signal which is delayed due to gas transport through the pathways of the device.
  • a carbon dioxide sensor may be included in the exhalation gas pathway to determine the carbon dioxide partial pressure of the exhalation gas stream. Such a determination would allow the device to calculate the proportionate amount of carbohydrate and fat being metabolized (given an estimate of protein metabolism).
  • Such formulations of carbohydrate and fat metabolism, given a ratio of carbon dioxide volumetric production to oxygen volumetric consumption are known in the art.
  • the invention has been described as using instantaneous or real time measurements of oxygen content and flow. Any exhalation breath will vary in oxygen content from start of exhalation to the end of exhalation, with less oxygen contained in the gas exhaled at the end of exhalation than at the beginning of exhalation.
  • the flow rate or speed of exhalation will also generally vary during exhalation.
  • Instantaneous or real time measurement of oxygen content and flow rate means that the output of the sensor will be substantially representative of the actual value of oxygen content and flow rate of the gas passing the sensor at the time of the output and that the device is configured so that the character of the gas passing through the device maintains the character of the gas as it was exhaled, i.e., that substantial mixing of the gas does not take place.
  • the output of the oxygen sensor will show the gas with an oxygen content substantially at twenty percent dropping to an oxygen content substantially at eighteen percent over a half second interval.
  • the output of the sensor will substantially track the actual values of the parameters being measured as they are upon exhalation of the breath. This does not happen with a mixing chamber where the exhaled gas over an entire exhaled breath or substantial portion of an exhaled breath is mixed so as to be averaged or equilibrated so that only an average oxygen content reading for the breath is obtained by the sensor.
  • the diameter of the exhalation pathway of the device has to be small enough to prevent substantial mixing of the gas as it is passing through the pathway before reaching the sensors, and that the sensors used have a fast response time so that the response can follow changes of the parameter in the breath.
  • some delay in sensor response and some small mixing of the sample will take place so the sensor readings are only approximate.
  • the sensors used should be fast sensors meaning that the T 10 -T 9 o response time of the sensor is less than about 500 msec, and preferably less than 300 msec. This means that output response of the sensor to a step change in input to the sensor, with output changing from ten percent to ninety percent, occurs in less than 500 msec.
  • a preferred oxygen sensor would have a T ⁇ 0 -T 90 response time of less than 500 msec and preferably less than 300 msec, for — tracking-the intra-breath oxygen partial-pressure value in the exhalation gas stream.

Abstract

Un calorimètre indirect destiné à mesurer le taux métabolique et les paramètres respiratoires correspondants d'un utilisateur comprend une partie non jetable (10) et un masque facial jetable (28). Le calorimètre utilise un flux d'écoulement de gaz d'expiration et une teneur en oxygène de gaz d'expiration pour déterminer le taux métabolique de l'utilisateur et d'autres paramètres respiratoires. D'autres propriétés du gaz d'expiration peuvent aussi être détectées pour déterminer les paramètres. Le flux de gaz expiré est dirigé dans une voie de gaz d'expiration à travers une partie non jetable (10) dans un mode d'écoulement unidirectionnel, de manière à exposer le gaz d'expiration aux capteurs de dispositifs comprenant un transducteur de flux de gaz d'expiration (32) et un capteur d'oxygène (40). Des signaux électriques provenant des captures sont transmis vers une unité de calcul telle qu'un microprocesseur qui effectue les calculs du taux de métabolisme ou autres et affiche les résultats sur un afficheur (20).
PCT/US2003/035428 2002-11-05 2003-11-04 Calorimetre indirect WO2004041084A1 (fr)

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US9949667B2 (en) 2008-11-17 2018-04-24 University Health Network Mask and method for use in respiratory monitoring and diagnostics
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US10078074B2 (en) 2013-01-22 2018-09-18 Arizona Board Of Regents On Behalf Of Arizona State University Portable metabolic analyzer system
WO2019074922A1 (fr) * 2017-10-10 2019-04-18 Endo Medical, Inc. Dispositif d'analyse de la respiration
WO2021108822A1 (fr) * 2019-12-02 2021-06-10 Lung-Diagnostics Gmbh Dispositif de test pulmonaire
US11284814B2 (en) * 2016-04-14 2022-03-29 Vo2 Master Health Sensors Inc. Device for measuring a user's oxygen-consumption

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EP1707120A3 (fr) * 2005-03-31 2007-07-25 Medical Graphics Corporation Capteur pour la détermination du quotient d'échange respiratoire
EP2091427A2 (fr) * 2006-12-04 2009-08-26 RIC Investments, LLC. Compensation d'erreurs volumétriques dans un système de surveillance de gaz
EP2091427A4 (fr) * 2006-12-04 2012-05-02 Ric Investments Llc Compensation d'erreurs volumétriques dans un système de surveillance de gaz
US9949667B2 (en) 2008-11-17 2018-04-24 University Health Network Mask and method for use in respiratory monitoring and diagnostics
EP2618732A1 (fr) * 2010-09-22 2013-07-31 University Health Network (UHN) Masque et procédé destinés à être utilisés dans la surveillance respiratoire et le diagnostic respiratoire
EP2618732A4 (fr) * 2010-09-22 2017-04-26 University Health Network (UHN) Masque et procédé destinés à être utilisés dans la surveillance respiratoire et le diagnostic respiratoire
US10078074B2 (en) 2013-01-22 2018-09-18 Arizona Board Of Regents On Behalf Of Arizona State University Portable metabolic analyzer system
WO2017180605A1 (fr) * 2016-04-12 2017-10-19 Endo Medical, Inc. Dispositif d'analyse de la respiration
WO2017180606A1 (fr) * 2016-04-12 2017-10-19 Endo Medical, Inc. Dispositif d'analyse de la respiration
US11284814B2 (en) * 2016-04-14 2022-03-29 Vo2 Master Health Sensors Inc. Device for measuring a user's oxygen-consumption
WO2019074922A1 (fr) * 2017-10-10 2019-04-18 Endo Medical, Inc. Dispositif d'analyse de la respiration
CN108523845A (zh) * 2018-04-13 2018-09-14 北京航空航天大学 便携式新陈代谢测量仪
WO2021108822A1 (fr) * 2019-12-02 2021-06-10 Lung-Diagnostics Gmbh Dispositif de test pulmonaire

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