Metabolic rate analyzer

• US 5,117,674 A
• Filed: 08/29/1991
• Issued: 06/02/1992
• Est. Priority Date: 05/22/1990
• Status: Expired due to Term

• Current Assignee: Aerosport, Inc.
• Original Assignee: Aerosport, Inc.
• Inventors: Howard, Charles P.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US07/752,020
• Time in Patent Office: 278 Days
• Field of Search: 128/716, 128/719, 128/720, 73/23.2, 73/23.3, 73/31.07
• US Class Current: 73/31.07
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

The metabolic rate analyzer comprises a flow proportioning valve for producing a proportional sample of the expired gas of the subject being studied. A sample cylinder is provided for drawing a proportional sample of the expired gas of the subject being studied from the flow proportioning valve. A test chamber is provided and an O₂ sensor is provided. The test chamber is provided with a selectively-permeable membrane, the selectively-permeable membrane having a selective permeability for CO₂, whereby CO₂ is selectively vented from the test chamber. The sample cylinder is also used for charging the test chamber with the proportional sample of the expired gas of the subject. A pressure sensor is provided for monitoring the pressure of the sample and determining the rate of pressure decay in the test chamber due to the selective venting of CO₂ through the permeable membrane. An analyzing means is provided for determining CO₂ content in the expired gas from the rate of pressure decay in the test chamber, conducting a volumetric analysis of the proportioinal sample to determine total volume of expired gas, and then correlating O₂ content, CO₂ content and total volume of expired gas to provide a measure of the metabolic rate of the subject being studied.

Claims

1. A CO₂ gas analyzer comprising:

a test chamber;

a means for charging said test chamber with a sample gas;

a selectively-permeable membrane disposed in said test chamber, said membrane being provided with a selective permeability for CO₂, said membrane being disposed in said test chamber for selectively venting CO₂ from said test chamber;

a pressure sensor for monitoring the pressure of the sample and determining the rate of pressure decay in said test chamber due to selective venting of CO₂ through said selectively-permeable membrane; and

an analyzing means for determining the CO₂ content of the sample gas from the rate of pressure decay in said test chamber.

2. The CO₂ gas analyzer of claim 1 further comprising a temperature sensor for monitoring the temperature of the sample, and analyzing means for determining CO₂ content corrected for sample temperature.

3. The CO₂ gas analyzer of claim 1 further comprising:

a second gas test chamber;

a second membrane disposed in said second gas test chamber, said second gas membrane being provided with a permeability for a second gas, said second membrane being disposed in said second gas test chamber for selectively venting a second gas from said second gas test chamber;

a means for charging said second gas test chamber with a sample gas;

a second gas pressure sensor for monitoring the pressure of the sample in said second gas test chamber and determining the rate of pressure decay in said second gas test chamber due to the selective venting of a second gas through said second gas membrane; and

an analyzing means for determining the content of a second gas in the sample from the rate of pressure decay in said second gas test chamber.

4. The CO₂ gas analyzer of claim 3 wherein said second membrane is similar in composition to said membrane having a selective permeability for CO₂ and each of said first and second test chambers are provided with a reference gas, and the reference gas in the first chamber is different than the reference gas in the second chamber.

5. The CO₂ gas analyzer of claim 4 wherein a reference gas of ambient air is provided for said membrane having a selective permeability for CO₂.

6. The CO₂ gas analyzer of claim 5 wherein a reference gas comprising a sample of the second gas is provided for said second membrane.

7. The CO₂ gas analyzer of claim 1 wherein said test chamber comprises a pressure vessel;

a sample outlet;

a sample inlet;

a sample window;

a first porous sintered metal plate disposed in said sample window;

a second porous sintered metal plate disposed in said sample window, said selectively-permeable membrane being disposed between said first and second sintered metal plates and supported by the same.

8. The CO₂ gas analyzer of claim 1 wherein said selectively-permeable membrane comprises a silicone rubber membrane.

9. The CO₂ gas analyzer of claim 8 further comprising a well disposed adjacent said selectively-permeable membrane, said well being disposed outside of said test chamber, said well containing a matrix saturated with water to compensate for the presence of water vapor in the sample gas.

10. The CO₂ gas analyzer of claim 1 wherein said analyzing means further comprises an analog to digital converter for transforming an analog signal representative of pressure into a corresponding digital signal.

11. The CO₂ gas analyzer of claim 10 wherein said analyzing means further comprises a programmed digital processor for determining the rate of pressure decay and then correlating the same to a value for CO₂ content.

12. A gas analyzer comprising:

a first test chamber;

a means for charging said test chamber with a sample gas;

a first selectively-permeable membrane disposed in said first test chamber, said first membrane being provided with a selective permeability for a first gas of interest, said first membrane being disposed in said first test chamber for selectively venting the first gas of interest from said first test chamber;

a first pressure sensor for monitoring the pressure of the sample and determining the rate of pressure decay in said first test chamber due to selective venting of the first gas of interest through said first selectively-permeable membrane; and

an analyzing means for determining the concentration of the first gas of interest in the sample gas from the rate of pressure decay in said first test chamber.

13. The gas analyzer of claim 12 further comprising a temperature sensor for monitoring the temperature of the sample, and analyzing means for determining the concentration of the first gas of interest corrected for sample temperature.

14. The gas analyzer of claim 12 further comprising:

a second gas test chamber;

a second membrane disposed in said second gas test chamber, said second membrane being provided with a selective permeability for a second gas, said second membrane being disposed in said second gas test chamber for selectively venting a second gas from said second gas test chamber;

a means for charging said second gas test chamber with a sample gas;

a second gas pressure sensor for monitoring the pressure of the sample in said second gas test chamber and determining the rate of pressure decay in said second gas test chamber due to the selective venting of a second gas through said second membrane; and

an analyzing means for determining the concentration of a second gas in the sample from the rate of pressure decay in said second gas test chamber.

15. The gas analyzer of claim 14 wherein said second membrane is similar in composition to said first membrane.

16. The gas analyzer of claim 15 wherein a first reference gas is provided for said first membrane and a second reference gas different from said first reference gas is provided for said second membrane.

17. The gas analyzer of claim 16 wherein said first reference gas comprises ambient air.

18. The gas analyzer of claim 17 wherein said second reference gas comprises a sample of the second gas.

19. The gas analyzer of claim 12 wherein said first test chamber comprises a pressure vessel;

a sample outlet;

a sample inlet;

a sample window;

a first porous sintered metal plate disposed in said sample window;

a second porous sintered metal plate disposed in said sample window, said first selectively-permeable membrane being disposed between said first and second sintered metal plates and supported by the same.

20. The gas analyzer of claim 12 wherein said first selectively-permeable membrane comprises a silicone rubber membrane.

21. The gas analyzer of claim 20 further comprising a well disposed adjacent said first selectively-permeable membrane, said well being disposed outside of said first test chamber, said well containing a matrix saturated with water to compensate for the presence of water vapor in the sample gas.

22. The gas analyzer of claim 12 wherein said analyzing means further comprises an analog to digital converter for transforming an analog signal representative of pressure into corresponding digital signals.

23. The gas analyzer of claim 22 wherein said analyzing means further comprises a programmed digital processor for determining the rate of pressure decay and then correlating the same to a value for the concentration of the gas of interest.

24. A method for determining CO₂ concentration in a gas mixture comprising the steps of:

providing a test chamber;

providing the test chamber with a pressure sensor and a selectively-permeable membrane, the membrane being provided with a selective permeability for CO₂, the membrane being disposed in the chamber for selectively venting CO₂ from the test chamber;

charging the test chamber with a sample of the gas mixture;

monitoring the pressure of the sample in the test chamber;

determining the rate of pressure decay in the test chamber due to the selective venting of CO₂ through the selectively-permeable membrane; and

determining the CO₂ concentration in the gas mixture from the rate of pressure decay in the test chamber.

25. The method for determining CO₂ concentration of claim 24 further comprising the steps of:

providing a second gas test chamber with a second gas pressure sensor and a second membrane having a permeability for a second gas of interest;

charging the second gas test chamber with a sample of the gas mixture;

monitoring the pressure of the sample in the second gas test chamber;

determining the rate of pressure decay in the second gas test chamber due to selective venting of the second gas of interest through the second membrane; and

determining the concentration of the second gas of interest in the gas mixture from the rate of pressure decay in the second gas test chamber.

26. The method for determining CO₂ concentration of claim 25 further comprising the steps of:

providing membranes of similar composition; and

providing different reference gases for each membrane.

27. The method for determining CO₂ concentration of claim 25 further comprising the steps of:

providing an ambient air reference for the membrane having a selective permeability for CO₂ ; and

providing a sample of the second gas reference for the second membrane.

28. The method for determining CO₂ concentration of claim 24 further comprising the steps of:

providing a temperature sensor;

monitoring the temperature of the sample gas; and

temperature correcting the steps of monitoring pressure, determining the rate of pressure decay and determining the CO₂ concentration.

29. The method for determining CO₂ concentration of claim 24 further comprising the steps of:

forming a selectively-permeable membrane from silicone rubber; and

compensating for water vapor in the sample by saturating the outside surface of the silicone membrane with water.

30. A method of gas analysis comprising the steps of:

providing a first test chamber;

providing the first test chamber with a first pressure sensor and a first selectively-permeable membrane, the first membrane having a selective permeability for a first gas of interest, the first membrane being disposed in the first test chamber for selectively venting the first gas of interest from the test chamber;

charging the first test chamber with a sample of a gas mixture;

monitoring the pressure of the sample in the first test chamber;

determining the rate of pressure decay in the first test chamber due to the selective venting of the first as of interest through the first selectively-permeable membrane; and

determining the concentration of the first gas of interest in the gas mixture from the rate of pressure decay in the test chamber.

31. The method of gas analysis of claim 30 further comprising the steps of:

providing a second gas test chamber with a second gas pressure sensor and a second membrane having a permeability for a second gas of interest;

charging the second gas test chamber with a sample of the gas mixture;

monitoring the pressure of the sample in the second gas test chamber;

determining the rate of pressure decay in the second gas test chamber due to selective venting of the second gas of interest through the second membrane; and

determining the concentration of the second gas of interest in the gas mixture from the rate of pressure decay in the second gas test chamber.

32. The method of gas analysis of claim 31 further comprising the steps of:

providing first and second membranes having a similar composition; and

providing different reference gases for each membrane.

33. The method of gas analysis of claim 31 further comprising the steps of:

providing an ambient air reference for the first membrane; and

providing a sample of the second gas reference for the second membrane.

34. The method of gas analysis of claim 30 further comprising the steps of:

providing a temperature sensor;

monitoring the temperature of the sample gas; and

temperature correcting the steps of monitoring pressure, determining the rate of pressure decay and determining the concentration of gas of interest.

35. The method of gas analysis of claim 30 further comprising the steps of:

forming a selectively-permeable membrane from silicone rubber; and

compensating for water vapor in the sample by saturating the outside surface of the silicone membrane with water.