Metabolic calorimeter employing respiratory gas analysis

• US 6,402,698 B1
• Filed: 09/19/2000
• Issued: 06/11/2002
• Est. Priority Date: 02/05/1998
• Status: Expired due to Term

• Current Assignee: Microlife Medical Home Solutions Inc.
• Original Assignee: HealtheTech, Inc.
• Inventors: Mault, James R.
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US09/601,589
• Time in Patent Office: 630 Days
• Field of Search: 600/529, 600/531, 600/532, 600/533, 600/538, 732/33, 128/204.22, 128/204.23
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption

Abstract

An indirect calorimeter for measuring the metabolic activity and related respiratory parameters of a subject includes a facial mask operative to be supported in contact with the subject so as to pass the inhalations and exhalations as the patient breathes. Both the inhaled and exhaled gasses pass through a tube which incorporates an ultrasonic pulse transit time flow meter adapted to generate electrical signals as a function of the instantaneous flow volume. A fluorescence quench oxygen sensor is supported in the flow tube and generates electrical signals as a function of the instantaneous oxygen content of the respiratory gasses. A computation unit receives output signals from the flow sensor and the oxygen sensor to calculate oxygen consumption and related parameters.

Claims

1. An indirect calorimeter for measuring the metabolic activity of a subject, said analyzer comprising:

a respiratory connector-operative to be supported in contact with the subject so as to pass inhaled and exhaled gases as the subject breathes;

a flow tube connected at one end to the respiratory connector and at the other end to a source and sink for respiratory gases so as to receive and pass inhaled and exhaled gases;

a flow meter operatively connected to said flow tube and adapted to generate electrical signals as a function of the instantaneous volume of inhaled and exhaled gases passing through the flow tube;

an oxygen sensor supported on the flow tube so as to generate electrical signals as a function of the instantaneous fraction of oxygen in the inhaled and exhaled gases as they pass through the flow tube; and

a computation unit for receiving said electrical output signals from the flow sensor and the oxygen sensor and operative to integrate the electrical signals which are functions of the instantaneous volume of gases passing through the flow tube with the electrical signals which are functions of the instantaneous fraction of oxygen in the gasses passing through the flow tube as the subject breathes over a period of time, the computation unit being operative to compute the oxygen consumption of the subject over the period of time by calculating the integral of the instantaneous flow volumes during inhalation, multiplied by the instantaneous oxygen content measurements at the time of such instantaneous flow volumes, and subtracting from that integral the integral of tile instantaneous flow volume during exhalation multiplied by the instantaneous oxygen content measurements at the time of such instantaneous flow volumes.

2. The indirect calorimeter of claim 1, wherein said flow meter is a bidirectional flow meter.

3. The indirect calorimeter of claim 2, wherein said bidirectional flow meter comprises an ultrasonic flow meter.

4. The indirect calorimeter of claim 1, wherein said oxygen sensor is a fluorescence quench oxygen sensor.

5. The indirect calorimeter of claim 1, wherein said respiratory connector comprises a mask having a free edge which can form a seal about a portion of a subject'"'"'s face.

6. The indirect calorimeter of claim 5, wherein said bidirectional flow meter and said ultrasonic oxygen sensor are supported on said mask.

7. The indirect calorimeter of claim 6, wherein said bidirectional flow meter and said ultrasonic oxygen sensor are supported by an insert, said insert adapted to matingly engage at least a portion of said mask.

8. The indirect calorimeter of claim 5, wherein said mask comprises a digital processor, visual display, and a power source.

9. The indirect calorimeter as in claim 7, wherein said insert comprises at least two nares spreaders adapted to resiliently engage the nares to enlarge opening of the nares.

10. The indirect calorimeter of claim 9, wherein said nares spreader comprises outwardly biased adhesive regions which engage the user'"'"'s nares and resiliently spring outwardly to enlarge the opening of the nares.

11. The indirect calorimeter of claim 5, wherein said mask further comprises a mechanism for transferring output from said sensors to said computer/computation unit.

12. The indirect calorimeter of claim 11, wherein said mechanism comprises a conductive line.

14. The system of claim 1, wherein the computer further calculates the subject'"'"'s carbon dioxide production over said period of time in accordance with the following equation:

15. The indirect calorimeter of claim 14, wherein said flow sensor is a bidirectional flow meter.

16. The indirect calorimeter of claim 14, wherein said gas sensor is an oxygen sensor.

17. The indirect calorimeter of claim 14, said flow meter including an emitter of ultrasonic pulses and a detector for receiving reflected ultrasonic pulses.

18. The indirect calorimeter of claim 16, wherein said oxygen sensor is a fluorescence quench oxygen sensor.

19. The indirect calorimeter of claim 18, wherein said oxygen sensor includes an emitter for stimulating radiation for a fluorescing coating and a receiver for measuring the intensity of the fluorescing radiation emitted by said coating.

20. The indirect calorimeter of claim 14, wherein said disposable section comprises a mask having a free edge which can form a seal about a portion of a subject'"'"'s face.

21. The indirect calorimeter of claim 20, wherein said flow meter and said oxygen sensor are supported on said mask.

22. The indirect calorimeter of claim 21, wherein said flow meter and said ultrasonic sensor are supported by an insert, said insert adapted to matingly engage at least a portion of said mask.

23. The indirect calorimeter of claim 20, wherein said mask comprises a digital processor, visual display, and a power source.

24. The indirect calorimeter of claim 22, wherein said insert comprises at least two nares spreaders adapted to resiliently engage the nares to enlarge opening of the nares.

25. The indirect calorimeter of claim 24, wherein said nares spreaders comprise outwardly biased adhesive regions which engage the user'"'"'s nares and resiliently spring outwardly to enlarge the opening of the nares.

26. The indirect calorimeter of claim 20, wherein said mask further comprises a mechanism for transferring output from said sensors to said computer/computation unit.

27. The indirect calorimeter of claim 26, wherein said mechanism comprises a conductive line.

28. The indirect calorimeter of claim 14, wherein said computer further calculates the subject'"'"'s carbon dioxide production over said period of time in accordance with the following equation:

13. An indirect calorimeter comprising:

a permanent, reusable section;

a disposable section adapted to engage said permanent section;

an oxygen sensor disposed on said permanent section, said oxygen sensor including an emitter for stimulating radiation for a fluorescing coating, a receiver measuring the intensity of the fluorescing radiation emitted by said coating;

a flow meter disposed on said permanent section, said flow meter including an emitter of ultrasonic pulses and a detector for receiving reflected ultrasonic pulses; and

a computer/computation unit operative to receive outputs from said oxygen sensor and said flow meter and to calculate respiratory parameters.

29. An indirect calorimeter for measuring the metabolic activity of a subject, said calorimeter comprising:

a respiratory connector configured to interface with the subject so as to pass inhaled and exhaled gases in use;

a flow pathway in fluid communication with the respiratory connector and with a source of respiratory gases and configured to pass inhaled and exhaled gases in use;

at least one flow meter provided along said flow pathway and adapted to generate electrical signals as a function of the instantaneous volume of inhaled and exhaled gases as said gases are actually passing through the flow pathway;

at least one oxygen sensor provided along said flow pathway and adapted to generate electrical signals as a function of the instantaneous fraction of oxygen in at least one of the inhaled and exhaled gases as said gases are actually passing through the flow pathway; and

a computation unit for receiving said electrical signals from the at least one flow meter and the at least one oxygen sensor and adapted to utilize said electrical signals to compute the subject'"'"'s oxygen consumption over a period of time.

30. An indirect calorimeter for measuring the metabolic activity of a subject, said calorimeter comprising:

a respiratory connector configured to interface with the subject so as to pass inhaled and exhaled gases in use;

a flow pathway in fluid communication with the respiratory connector and with a source of respiratory gases and configured to pass inhaled and exhaled gases in use;

at least one flow meter adapted to determine the volume of inhaled and exhaled gases as said gases are passing through the flow pathway;

at least one oxygen sensor to determine the oxygen content of at least one of the inhaled and exhaled gases as said gases are passing through the flow pathway; and

a computation unit for receiving output signals from the at least one flow meter and the at least one oxygen sensor and adapted to utilize said output signals to compute the subject'"'"'s oxygen consumption over a period of time.

31. An indirect calorimeter comprising:

a flow pathway adapted to communicate respiratory gases with a subject;

a permanent, reusable section having;

at least one flow meter adapted to measure the flow volume of gases as they pass through the flow pathway; and

at least one gas sensor adapted to measure content of gases as they pass through the flow pathway;

a disposable section selectively engaged in fluid communication with said permanent section wherein said disposable section defines at least a portion of the flow pathway; and

a respiratory connector configured to interface with a subject;

wherein said permanent section further comprises a computer/computation unit configured to receive outputs from said at least one gas sensor and said at least one flow meter and to calculate respiratory parameters therefrom.

32. An indirect calorimeter for measuring the metabolic activity of a subject, said calorimeter comprising:

a respiratory connector, wherein said respiratory connector is configured to interface with the subject;

a disposable section comprising;

at least a portion of a flow pathway, wherein said flow pathway is in fluid communication with the respiratory connector and with a source of respiratory gases;

a permanent, reusable section adapted to selectively engage in fluid communication with said disposable section, said reusable section comprising;

at least one flow meter, wherein said flow meter is adapted to measure flow volume of inhaled gases as they pass through the flow pathway and to measure flow volume of exhaled gases as they pass through the flow pathway;

at least one oxygen sensor, wherein said at least one oxygen sensor is adapted to measure oxygen content in gases as they pass through the flow pathway; and

a computer/computation unit operative to receive outputs from said at least one oxygen sensor and said at least one flow meter and adapted to compute the subject'"'"'s oxygen consumption over a period of time.

33. A method for calculating oxygen consumption of a subject, comprising:

providing a flow tube through which the subject may inhale and exhale gas;

measuring within the flow tube the flow volume of inhaled gases as they pass through the flow tube;

measuring within the flow tube the flow volume of exhaled gases as they pass through the flow tube;

measuring within the flow tube the oxygen concentration of at least one of said inhaled and exhaled gases as they pass through the flow tube; and

calculating oxygen consumption using the inhaled flow volume, the exhaled flow volume, and the oxygen concentration.

34. An indirect calorimeter operative to measure the respiratory consumption per unit time of a subject, comprising:

a respiratory connector operative to be in fluid communication with the respiratory system of a subject so as to pass respiratory gases as the subject breathes;

a flow meter operative to generate signals as a function of the volume of gases passed through the flow meter;

an oxygen sensor operative to generate signals as a function of the instantaneous oxygen content of gases passed through the sensor;

an electronic computer operative to receive signals from the flow meter and the oxygen sensor; and

conduits interconnecting the respiratory connector, the flow meter and oxygen sensor such that the subject'"'"'s inhalations and exhalations pass through the flow meter an the subject'"'"'s exhalations pass through the oxygen sensor,

the computer being operative to receive the signals from the oxygen sensor and the flow meter to calculate the subject'"'"'s oxygen consumption over the period of the test.