Metabolic analyzer

• US 5,363,857 A
• Filed: 06/01/1993
• Issued: 11/15/1994
• 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): Cohen, Lee S.
• Assistant Examiner(s): Nasser, Robert L.
• Application Number:
  US08/069,513
• Time in Patent Office: 532 Days
• Field of Search: 128/716, 128/718, 128/719, 128/622, 128/205.22, 128/205.23, 356/41
• US Class Current: 600/531
• 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: A61B 5/7242 using integration
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

A metabolic rate analyzer is provided comprising a CO₂ detector, an O₂ detector, a flow resistance, a differential pressure transducer, a solenoid-actuated metering valve for producing a volumetrically-proportional sample of respired gas, a vacuum regulator for receiving the sample, a pump for drawing the sample from the vacuum regulator, and a processor for periodically sampling the differential pressure signal to provide a flow signal, to modulate power applied to the solenoid-actuated flow proportioning valve, and to provide a measure of the total volume of respired gas. The processor correlates the total volume of respired gas, O₂ content and CO₂ content to provide a measure of metabolic rate. Flow is recycled between the pump and the regulator valve to provide a source of mixed respired gas for analysis and digital integration of the flow signal provides a measure of the total volume of respired gas. A pulse generator driven by the microprocessor varies the frequency of pulses applied to the metering valve and the pulse width to provide volumetrically-proportional sampling and to control the effective sample volume of the analyzer, respectively. The processor determines the slope of the flow signal and increases the periodic sample rate of the pressure signal when slope is increasing and decreases the periodic sample rate when slope is decreasing to provide derivative augmentation of the sample period.

Claims

1. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a small, representative and proportional sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and said O₂ detector means; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means determining the total volume of respired gas and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

2. The metabolic analyzer of claim 1 further comprising regulator means for receiving the sample of the respired gas from said flow proportioning valve means and delivering the sample of the respired gas to said pump means.

3. The metabolic analyzer of claim 2 wherein said pump means is provided with a first output and a second output, said first output of said pump means being directed to said regulator means to provide a loop flow of mixed respired gas and said second output being directed to said CO₂ and O₂ detector means to provide a sample of mixed respired gas.

4. The metabolic analyzer of claim 2 wherein said regulator means comprises a vacuum regulator having a regulator output port maintained at a predetermined vacuum.

5. The metabolic analyzer of claim 4 wherein said regulator means further comprises a regulator input port connected to said flow proportioning valve means for receiving respired gas.

6. The metabolic analyzer of claim 1 wherein said flow detector means comprises an orifice which provides a restriction to the flow of respired gas and a differential pressure transducer for determining the pressure drop across said orifice.

7. The metabolic analyzer of claim 6 wherein said orifice is disposed in a plate and comprises a sharp plate orifice.

8. The metabolic analyzer of claim 7 wherein said differential pressure transducer comprises means for providing a flow signal that is proportional to the square of the flow of respired gas through said sharp plate orifice.

9. The metabolic analyzer of claim 8 wherein said sharp plate orifice is provided with a cross shape.

10. The metabolic analyzer of claim 1 wherein said flow detector means provides a flow signal having a known relationship to the flow of respired gas and said analyzer further comprises pulse generator means for generating said sampling signal, said sampling signal having a variable frequency, the frequency of the said sampling signal being controlled by said processor means and the flow signal so that the frequency of said sampling signal is proportional to the flow of respired gas.

11. The metabolic analyzer of claim 10 wherein said pulse generator means generates said sampling signal with a variable pulse width and said processor means determines the breath rate of an individual being studied by monitoring the flow signal, said processor means controlling the pulse width of said sampling signal, said processor means decreasing the pulse width when breath rate is high and increasing pulse width when breath rate is low to control an effective sample volume of the metabolic analyzer.

12. The metabolic analyzer of claim 10 wherein said flow proportioning valve means further comprises means responsive to the output of said pulse generator means for delivering a volumetrically-proportional sample of respired gas.

13. The metabolic analyzer of claim 12 wherein said flow proportioning valve means comprises a normally-closed, spring-biased, solenoid valve having an actuation coil which overcomes the spring bias when the output of said pulse generator means is applied to said actuation coil, thus opening said flow proportioning valve means to deliver a volumetrically-proportional sample of respired gas.

14. The metabolic analyzer of claim 1 wherein said flow detector means comprises means for providing a flow signal having a known relationship to the flow of respired gas, said processor means comprising means for receiving the flow signal, periodically determining a flow rate value for respired gas and summing said flow rate values to provide a measure of the total volume of respired gas by effectively integrating respired gas flow over time.

15. The metabolic analyzer of claim 14 wherein said flow detector means comprises a sharp plate orifice and a differential pressure transducer, an output of said differential pressure transducer comprising said flow signal, the square root of said flow signal being representative of the flow rate value of respired gas, said processor means periodically sampling said flow signal, taking the square root of said flow signal to form a flow rate value, summing said flow rate values, dividing by the number of flow rate values formed, and multiplying by the elapsed time to provide a measure of the total volume of respired gas by digital integration.

16. The metabolic analyzer of claim 1 wherein said flow detector means comprises means for providing a flow signal having a known relationship to the flow of respired gas, said processor means comprises means for receiving and periodically sampling the flow signal;

said processor means periodically determining a flow rate value and comparing flow rate values to determine a time rate of change (slope) for said flow rate values;

said processor means increasing a periodic sample rate when the slope is increasing and decreasing the periodic sample rate when the slope is decreasing to provide a derivative augmentation of the sample rate of the metabolic analyzer.

17. The metabolic analyzer of claim 16 wherein said flow detector means comprises a sharp plate orifice and a differential pressure transducer, an output of said pressure transducer comprising said flow signal, the square root of said flow signal comprising said flow rate value, said processor means periodically determining the square root of said flow signal and the slope of the square root of said flow signal.

18. The metabolic analyzer of claim 1 wherein said O₂ detector means comprises a galvanic cell.

19. The metabolic analyzer of claim 1 wherein said CO₂ detector means comprises a non-dispersive infrared (NDIR) gas analyzer.

20. The metabolic analyzer of claim 19 wherein said NDIR gas analyzer further comprises:

an infrared (IR) source of energy in a bandwidth having a known absorption by CO₂ ;

a sample cell through which the respired gas passes;

an IR detector;

said IR source being disposed on one side of said sample cell and said IR detector being disposed on another side of said sample cell for measuring the absorption of IR due to the CO₂ content of the respired gas and to provide a signal representative of the CO₂ content of the respired gas.

21. The metabolic analyzer of claim 20 wherein said NDIR gas analyzer further comprises a body having a known absorption for IR energy that corresponds to a predetermined CO₂ content in a gas being studied;

and a mechanical transport for reciprocally placing said body between said source and said detector to calibrate said NDIR analyzer.

22. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and said O₂ detector means, said pump means having a pump inlet and a pump outlet;

vacuum regulator means for receiving the sample of the respired gas from said flow proportioning valve means and delivering the sample to said pump means, said vacuum regulator means having a regulator input port connected to said flow proportioning valve means for receiving the sample, a regulator output port maintained at a predetermined vacuum, and a regulator recycle port, said pump inlet being connected to said regulator output port and said pump outlet being connected to said regulator recycle port to provide a loop for mixing respired gas; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means determining the total volume of respired gas, and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

23. The metabolic analyzer of claim 22 wherein said pump outlet is also connected to said CO₂ detector means and said O₂ detector means to provide a sample of mixed respired gas to said CO₂ and O₂ detector means when said flow proportioning valve means releases respired gas to said vacuum regulator means.

24. The metabolic analyzer of claim 23 further comprising a calibration valve connected to said regulator input port for introducing ambient air to span and calibrate said CO₂ and O₂ means.

25. A metabolic analyzer comprising:

CO₂ detector means for determining an CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and O₂ detector means, said pump means having a pump inlet and a pump outlet;

vacuum regulator means for receiving the sample of the respired gas from said flow proportioning valve means and delivering the sample to said pump means, said vacuum regulator means comprising;

a regulator body defining a gas chamber;

a regulator input port for receiving respired gas from said flow proportioning valve means;

a regulator output port for delivering respired gas to said pump inlet;

a flexible diaphragm disposed between said regulator input port and said regulator output port, said diaphragm dividing said gas chamber into an input side and an output side in fluid communication with said regulator input port and said regulator output port, respectively;

a regulator metering port disposed in said diaphragm for establishing a fluid communication between said input side and said output side of said gas chamber;

a regulator recycle port in fluid communication with said regulator output side;

a regulator transfer port disposed in said output side of said gas chamber for supplying respired gas to said regulator output port, said diaphragm being spring-biased against said transfer port to keep said transfer port normally closed except for said metering port which extends therethrough;

said pump inlet being connected to said regulator output port and said pump outlet being connected to said regulator recycle port to form a loop for mixing respired gas; and

said pump outlet being connected to said CO₂ detector means and said O₂ detector means to provide a sample of mixed respired gas to said CO₂ and O₂ means when said flow proportioning valve means introduces a volume of respired gas to said input side of said gas chamber of said vacuum regulator means; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means determining the total volume of respired gas, and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

26. A metabolic rate analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

a flow restriction through which the respired as is directed;

differential pressure detector means connected to said flow restriction for providing a differential pressure signal representative off the flow of respired gas through said flow restriction;

solenoid-actuated flow proportioning valve means adapted to be connected to a source of respired gas for delivering a small, representative and volumetrically-proportional sample of respired gas;

vacuum regulator means for receiving the sample;

pump means for drawing the sample from said vacuum regulator means and delivering the sample to said CO₂ and O₂ detector means; and

processor means for converting said differential pressure signal into a flow signal that is representative of a volumetric flow of respired gas that established said differential pressure signal, said processor means using said flow signal to modulate electrical power applied to said solenoid-actuated flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means determining the total volume of respired gas and correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

27. A metabolic rate analyzer comprising:

CO₂ detector means for providing a CO₂ signal representative of the CO₂ content of a respired gas;

O₂ detector means for providing an O₂ signal representative of the O₂ content of the respired gas;

a sharp plate orifice through which the respired gas is directed;

differential pressure transducer means for providing a pressure signal representative of the difference in pressure of the respired gas on opposite sides of said orifice;

solenoid-actuated flow proportioning valve means adapted to be connected to a source of respired gas for delivering a small, representative volumetrically-proportional sample of respired gas;

vacuum regulator means for receiving the sample of respired gas;

pump means for drawing the sample of respired gas from said vacuum regulator means, said pump means being provided with a first output and a second output;

said first output of said pump means being directed to said vacuum regulator means to provide a loop flow of mixed respired gas;

said second output of said pump means being directed to said CO₂ detector means and said O₂ detector means for delivering mixed respired gas thereto;

processor means for periodically sampling said pressure signal and taking the square root of said pressure signal to provide a flow signal representative of the flow of respired gas;

pulse generator means having a variable frequency and variable pulse width output controlled by said processor means and said flow signal, the frequency of the output of said pulse generator means increasing with an increase in the flow signal and decreasing with a decrease in the flow signal, the output of said pulse generator means being applied to said solenoid-actuated flow proportioning valve means;

said processor means summing said flow signals, dividing by the number of flow signals taken, and multiplying by elapsed time to provide a measure of the total volume of respired gas, thus effectively integrating said flow signal;

said processor means monitoring said flow signal to determine a breath rate and for increasing the pulse width of the output of said pulse generator means when breath rate is low and for decreasing pulse width when breath rate is high, thus controlling an effective sample volume of the analyzer;

said processor means having a variable period for sampling said flow signal, said processor means determining a slope of said flow signal for decreasing said period when the slope is increasing and increasing said period when the slope is decreasing, thus effecting derivative augmentation of said variable period for sampling;

said processor means correlating said measure of the total volume of respired gas, said CO₂ signal and said O₂ signal to provide a measure of metabolic rate.

28. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas, said CO₂ detector means comprising a non-dispersive infrared (NDIR) gas analyzer having an infrared (IR) source and a means for calibrating said NDIR analyzer comprising a means for attenuating said IR source;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a small, representative and proportional sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and said O₂ detector means; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means determining the total volume of respired gas and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

29. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a small, representative and proportional sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means, said pump means being provided with an inlet, a first output and a second output, said first output being connected back to said inlet to provide a recirculation loop of mixed respired gas and said second output being connected to said CO₂ and O₂ detector means to provide a sample of mixed respired gas; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means determining the total volume of respired gas and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

30. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a small, representative and proportional sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and said O₂ detector means; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said processor means having a sample period for sampling said flow signal, said processor means determining the slope of said flow signal for decreasing said period when the slope is increasing and increasing said period when the slope is decreasing to provide derivative augmentation of said sample period, said processor means determining the total volume of respired gas and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

31. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a small, representative and proportional sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and said O₂ detector means; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said sampling signal comprising a series of digital pulses having a pulse width, said processor means monitoring said flow signal to determine a breath rate for increasing said pulse width when breath rate is low and decreasing said pulse width when breath rate is high for providing a variable sample volume, said processor means determining the total volume of respired gas and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.

32. A metabolic analyzer comprising:

CO₂ detector means for determining a CO₂ content of a respired gas;

O₂ detector means for determining an O₂ content of the respired gas;

flow detector means for providing a flow signal representative of the flow of the respired gas;

flow proportioning valve means for delivering a small, representative and proportional sample of the respired gas having a known volumetrically-proportional relationship with a total volume of the respired gas;

pump means for drawing the sample of the respired gas from said flow proportioning valve means and delivering the sample to said CO₂ and said O₂ detector means; and

processor means for converting said flow signal into a sampling signal that is applied to said flow proportioning valve means to provide a sample of respired gas having a known volumetrically-proportional relationship with the total volume of respired gas, said sampling signal comprising a series of digital pulses having a frequency, said processor means monitoring said flow signal for increasing said frequency when said flow signal increases and decreasing said frequency when said flow signal decreases for providing a proportional sample, said processor means determining the total volume of respired gas and said processor means correlating total volume, CO₂ content and O₂ content to provide a measure of metabolic rate.