Metabolic calorimeter employing respiratory gas analysis

• US 20030065275A1
• Filed: 10/16/2002
• Published: 04/03/2003
• Est. Priority Date: 08/02/1999
• Status: Abandoned Application

• Current Assignee: HealtheTech, Inc.
• Original Assignee: HealtheTech, Inc.
• Inventors: Lawrence, Craig M., Prachar, Timothy J., Mault, James R., Weintraub, Jeffrey C., Nason, Kevin S., Barber, Theodore W., Pearce, Edwin M. Jr.
• Application Number:
  US10/272,348
• Publication Number:
  US 20030065275A1
• Time in Patent Office: Days
• US Class Current: 600/531
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: A61B 5/222 combined with detection or measurement of physiological parameters, e.g. heart rate
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

An indirect calorimeter for measuring the metabolic rate of a subject includes a disposable portion and a reusable portion. The disposable portion includes a respiratory connector configured to be supported in contact with the subject so as to pass inhaled and exhaled gases as the subject breathes. The disposable portion also includes a flow pathway operable to receive and pass inhaled and exhaled gases, having a first end in fluid communication with the respiratory connector and a second end in fluid communication with a source and sink for respiratory gases. The disposable portion is disposed within the reusable portion, which includes a flow meter, a temperature sensing means, a humidity sensing means, a pressure sensing means, a component gas concentration sensor, and a computation unit. The flow meter generates a signal as a function of the instantaneous flow volume of respiratory gases passing through the flow pathway and the component gas concentration sensor generates a signal as a function of the instantaneous fraction of a predetermined component gas in the exhaled gases. The computation unit receives the electrical signals from the flow meter, the temperature sensing means, the pressure sensing means, the humidity sensing means, and the concentration sensor and calculates at least one respiratory parameter for the subject as the subject breathes through the calorimeter.

Claims

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

a disposable portion having a respiratory connector configured to be supported in contact with the subject so as to pass inhaled and exhaled gases as the subject breathes;

a flow pathway within said disposable portion operable to receive and pass inhaled and exhaled gases, said flow pathway having a first end in fluid communication with said respiratory connector and a second end in fluid communication with a source and sink for respiratory gases;

a reusable portion having a housing with a recess defined therein for receiving said disposable portion;

a flow meter within said housing configured to generate electrical signals as a function of the instantaneous flow volume of inhaled and exhaled gases passing through said flow pathway;

a temperature sensing means within said housing operable to generate an electrical signal representative of ambient temperature;

an ambient pressure sensing means within said housing operable to generate an electrical signal representative of ambient pressure;

a humidity sensing means within said housing operable to generate an electrical signal representative of relative humidity;

a component gas concentration sensor within said housing operable to generate an electrical signal as a function of the instantaneous fraction of a predetermined component gas in the exhaled gases as the gases pass through said flow pathway; and

a computation unit operable within said housing to receive said electrical signals from said flow meter, said temperature sensor, said humidity sensor, said ambient pressure sensor and said concentration sensor and operative to calculate at least one respiratory parameter for the subject as the subject breathes through the calorimeter.

2. The calorimeter according to claim 1, wherein said flow pathway includes an elongated flow tube through which the inhaled and exhaled gases flow, and a chamber disposed between said flow tube and said first end, said chamber being a concentric chamber surrounding one end of said flow tube and being defined between said flow tube and said outer housing.

3. The calorimeter according to claim 1, wherein said disposable portion is received in the recess in a direction perpendicular to said flow tube.

4. The calorimeter according to claim 1, wherein said component gas concentration sensor is an oxygen sensor.

5. The calorimeter according to claim 4, wherein said oxygen sensor is a fluorescence quench type oxygen sensor.

6. The calorimeter as set forth in claim 4 wherein said temperature sensing means senses ambient temperature and oxygen sensor temperature.

7. The calorimeter according to claim 1 wherein said flow meter includes an upper ultrasonic transducer and a lower ultrasonic transducer in fluid communication with the inhaled and exhaled gases passing through said flow pathway.

8. The calorimeter according to claim 7, wherein said temperature, pressure and humidity sensing means are microscopic temperature, pressure and humidity transducers arranged in an array within said ultrasonic transducer.

9. The calorimeter according to claim 1, wherein said respiratory parameter is resting metabolic rate, which is calculated from the measured volume of oxygen consumed by the subject and the measured amount of carbon dioxide produced by the subject.

10. The calorimeter according to claim 1, further comprising a carbon dioxide sensing means for sensing the amount of carbon dioxide in the exhaled gases.

11. An indirect calorimeter for measuring the metabolic rate of a subject, said calorimeter comprising:

a disposable portion having a respiratory connector configured to be supported in contact with the subject so as to pass inhaled and exhaled gases as the subject breathes;

a flow pathway within said disposable portion operable to receive and pass inhaled and exhaled gases, said flow pathway having a first end in fluid communication with said respiratory connector and a second end in fluid communication with a source and sink for respiratory gases;

a reusable portion having a housing with a recess defined therein for receiving said disposable portion;

a flow meter within said housing configured to generate electrical signals as a function of the instantaneous flow volume of inhaled and exhaled gases passing through said flow pathway, wherein said flow pathway includes an elongated flow tube through which the inhaled and exhaled gases flow, and a chamber disposed between said flow tube and said first end, said chamber being a concentric chamber surrounding one end of said flow tube and being defined between said flow tube and said outer housing;

a temperature sensing means within said housing operable to generate an electrical signal representative of ambient temperature;

an ambient pressure sensing means within said housing operable to generate an electrical signal representative of ambient pressure;

a humidity sensing means within said housing operable to generate an electrical signal representative of relative humidity;

a component gas concentration sensor within said housing operable to generate an electrical signal as a function of the instantaneous fraction of a predetermined component gas in the exhaled gases as the gases pass through said flow pathway; and

a computation unit operable within said housing to receive said electrical signals from said flow meter, said temperature sensor, said humidity sensor, said ambient pressure sensor and said concentration sensor and operative to use said electrical signals in calculating at least one respiratory parameter for the subject as the subject breathes through the calorimeter.

12. The calorimeter according to claim 11, wherein said respiratory parameter is resting metabolic rate, which is calculated from the measured volume of oxygen consumed by the subject and the measured amount of carbon dioxide produced by the subject.

13. The calorimeter according to claim 12 wherein said flow meter includes an upper ultrasonic transducer and a lower ultrasonic transducer in fluid communication with the inhaled and exhaled gases passing through said flow pathway.

14. The calorimeter according to claim 13, wherein said temperature, pressure and humidity sensing means are microscopic temperature, pressure and humidity transducers arranged in an array within said ultrasonic transducer.

15. The calorimeter according to claim 14, wherein said component gas concentration sensor is an oxygen sensor.

16. The calorimeter according to claim 15, wherein said oxygen sensor is a fluorescence quench type oxygen sensor.

17. The calorimeter as set forth in claim 15 wherein said temperature sensing means senses ambient temperature and oxygen sensor temperature.

18. The calorimeter according to claim 15, further comprising a carbon dioxide sensing means for sensing the amount of carbon dioxide in the exhaled gases.

19. An indirect calorimeter for measuring the metabolic rate of a subject, said calorimeter comprising:

a disposable portion having a respiratory connector configured to be supported in contact with the subject so as to pass inhaled and exhaled gases as the subject breathes;

wherein said disposable portion includes an outer shell having a ceiling at an upper end, a floor at a lower end, and a rearward wall extending therebetween said ceiling and said floor, and said ceiling includes an opening with a predetermined pathogen resistant material disposed across the opening and said floor includes a first opening with another predetermined pathogen resistant material disposed across the opening, and a second opening, and said rearward wall includes an opening with another pathogen resistant material disposed across the opening;

a flow pathway within said disposable portion operable to receive and pass inhaled and exhaled gases, said flow pathway having a first end in fluid communication with said respiratory connector and a second end in fluid communication with a source and sink for respiratory gases, said flow pathway including a flow tube through which the inhaled and exhaled gases pass, and a chamber disposed between said flow tube and said first end, said chamber being a concentric chamber surrounding one end of said flow tube and being defined between said flow tube and said outer housing;

a reusable portion operatively attached to said disposable portion, and having a passageway in fluid communication with the source and sink for respiratory gases and in alignment with the second opening in the floor;

a flow meter within said disposable portion, wherein said flow meter includes an upper ultrasonic transducer for measuring the instantaneous flow volume in alignment with the opening in the ceiling, and a lower ultrasonic transducer for measuring the instantaneous flow volume in alignment with the first opening in the floor;

a temperature sensing means within said housing operable to generate an electrical signal representative of ambient temperature;

an ambient pressure sensing means within said housing operable to generate an electrical signal representative of ambient pressure;

a humidity sensing means within said housing operable to generate an electrical signal representative of relative humidity;

a component gas concentration sensor within the disposable portion that is in alignment with the opening in the back wall;

a computation unit within said disposable portion, wherein said flow meter generates an electrical signal as a function of the instantaneous flow volume of inhaled and exhaled gases passing through said flow pathway and said component gas concentration sensor generates an electrical signal as a function of the instantaneous fraction of a predetermined component gas in the exhaled gases as the gases pass through said flow pathway and said computation unit receives said electrical signals from said flow meter, said temperature sensing means, said ambient pressure sensing means, said humidity sensing means and said concentration sensor and calculates at least one respiratory parameter for the subject as the subject breathes through the calorimeter.

20. The calorimeter according to claim 19, wherein said temperature, pressure and humidity sensing means are microscopic temperature, pressure and humidity transducers arranged in an array within said ultrasonic transducer.

21. The calorimeter according to claim 19, wherein said component gas concentration sensor is an oxygen sensor.

22. The calorimeter as set forth in claim 21 wherein said temperature sensing means senses ambient temperature and oxygen sensor temperature.

23. The calorimeter according to claim 19, further comprising a carbon dioxide sensing means for sensing the amount of carbon dioxide in the exhaled gases.

24. The calorimeter according to claim 19, wherein said respiratory parameter is resting metabolic rate, which is calculated from the measured volume of oxygen consumed by the subject and the measured amount of carbon dioxide produced by the subject.