Metabolic calorimeter employing respiratory gas analysis

• US 6,955,650 B2
• Filed: 05/31/2002
• Issued: 10/18/2005
• Est. Priority Date: 08/02/1999
• Status: Expired due to Term

• Current Assignee: Microlife Medical Home Solutions Inc. (Morgan Stanley)
• Original Assignee: HealtheTech, Inc. (Morgan Stanley)
• Inventors: Lawrence, Craig M., Prachar, Timothy J., Mault, James R., Weintraub, Jeffrey C., Nason, Kevin S., Barber, Theodore W., Pearce, Edwin M. Jr.
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): Mallari, Patricia C.
• Application Number:
  US10/161,244
• Publication Number:
  US 20030065273A1
• Time in Patent Office: 1,236 Days
• Field of Search: 600529-543, 73/233, 128/204.18, 128/200.24, 128/205.12, 128/205.27, 128/206.12, 12820615-20617, 128/206.22, 128/206.24, 128/909, D24/110.1
• 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 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, and a hygiene barrier positioned to block a predetermined pathogen from the exhaled gases. The indirect calorimeter also includes a flow pathway 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 flow pathway includes a flow tube through which the inhaled and exhaled gases pass, an outer housing surrounding the flow tube, and a chamber disposed between the flow tube and the first end. The indirect calorimeter also includes a flow meter configured to generate electrical signals as a function of the instantaneous flow volume of inhaled and exhaled gases passing through the flow pathway, and a component gas concentration sensor operable to generate electrical signals as a function of the instantaneous fraction of a predetermined component gas in the exhaled gases as the gases pass through the flow pathway. The indirect calorimeter further includes a computation unit operable to receive the electrical signals from the flow meter and the concentration sensor and operative to calculate at least one respiratory parameter for the subject as the subject breathes through the calorimeter.

Claims

1. An indirect calorimeter, comprising:

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

a hygiene barrier module operatively connected to said respiratory connector, such that said inhaled and exhaled gases pass therethrough said hygiene barrier module for blocking a predetermined pathogen from said exhaled gases;

a flow pathway operatively connected to said hygiene barrier module for receiving and passing said 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 comprising;

(1) a flow tube through which said inhaled and exhaled gases pass, (2) an outer housing surrounding said flow tube, and (3) 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 flow meter configured to generate electrical signals as a function of an instantaneous flow volume of said inhaled and exhaled gases passing through said flow pathway;

a component gas concentration sensor operable to generate electrical signals as a function of an instantaneous fraction of a predetermined component gas in said exhaled gases passing through said flow pathway; and

a computation unit operable to receive said electrical signals from said flow meter and said concentration sensor and to calculate at least one respiratory parameter for said subject as said subject breathes through said calorimeter.

2. The calorimeter according to claim 1, wherein said hygiene barrier module includes a hygiene barrier housing including two generally parallel and spaced apart side walls and a hygiene barrier disposed between said side walls.

3. The calorimeter according to claim 2, wherein said hygiene barrier is a filtering material.

4. The calorimeter according to claim 2, wherein said hygiene barrier housing includes a lower wall and a saliva retention wall extending upwardly from said lower wall and adjacent said hygiene barrier to form a saliva trap.

5. The calorimeter according to claim 2, wherein said hygiene barrier module includes a respiration port for operatively connecting said hygiene barrier module to a corresponding port for said respiratory connector and a calorimeter port for operatively connecting said hygiene barrier module to a corresponding inlet conduit in fluid communication with said flow pathway.

6. The calorimeter according to claim 1, wherein said respiratory connector is a mask.

7. The calorimeter according to claim 1, wherein said hygiene barrier module and said respiratory connector are disposable.

8. The calorimeter according to claim 1, wherein said respiratory connector is a mouthpiece.

9. An indirect calorimeter, comprising:

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

a flow pathway operatively connected to said respiratory connector for receiving and passing said 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 comprising;

(1) a flow tube through which said inhaled and exhaled gases pass, (2) an outer housing surrounding said flow tube, and (3) 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 hygiene barrier positioned such that said inhaled and exhaled gases pass therethrough said hygiene barrier for blocking a predetermined pathogen from said exhaled gases;

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

a component gas concentration sensor operable to generate electrical signals as a function of an instantaneous fraction of a predetermined component gas in said exhaled gases passing through said flow pathway; and

a computation unit operable to receive said electrical signals from said flow meter and said concentration sensor and to calculate at least one respiratory parameter for said subject as said subject breathes through said calorimeter.

10. The calorimeter according to claim 9, wherein said respiratory connector is a mask, and said hygiene barrier is disposed within said mask.

11. The calorimeter according to claim 9, wherein said hygiene barrier is housed within a hygiene barrier module operatively connected between said respiratory connector and said flow pathway, said hygiene barrier module including a hygiene barrier housing including two generally parallel and spaced apart side walls with said hygiene barrier disposed between said side walls.

12. The calorimeter according to claim 11, wherein said hygiene barrier is a filtering material.

13. The calorimeter according to claim 11, wherein said hygiene barrier housing includes a lower wall and a saliva retention wall extending upwardly from said lower wall and adjacent said hygiene barrier to form a saliva trap.

14. The calorimeter according to claim 11, wherein said hygiene barrier module includes a respiration port for operatively connecting said hygiene barrier module to a corresponding port for said respiratory connector and a calorimeter port for operatively connecting said hygiene barrier module to a corresponding inlet conduit in fluid communication with said flow pathway.

15. The calorimeter according to claim 14, wherein said respiratory connector is a mouthpiece.

16. The calorimeter according to claim 14, wherein said respiratory connector and said hygiene barrier module are disposable.

17. The calorimeter according to claim 14, wherein said respiratory connector is a mask.

18. The calorimeter according to claim 10, wherein said mask further includes a mask shell and a mask liner inserted in said mask shell.

19. The calorimeter according to claim 18, wherein said hygiene barrier is a filtering material.

20. The calorimeter according to claim 19, wherein said mask shell and an inlet conduit for said flow pathway are integral and formed as one piece.

21. The calorimeter according to claim 20, wherein said mask shell, said inlet conduit and said flow pathway are disposable.

22. An indirect calorimeter, comprising:

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

a hygiene barrier disposed within said respiratory connector, such that substantially all of said inhaled and exhaled gases pass through said hygiene barrier, and said hygiene barrier operatively passes said inhaled and exhaled gases therethrough while blocking a predetermined pathogen in said exhaled gases;

a flow pathway operable to receive and pass said 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 comprising;

(1) a flow tube through which said inhaled and exhaled gases pass, (2) an outer housing surrounding said flow tube, and (3) 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 flow meter configured to generate electrical signals as a function of an instantaneous flow volume of said inhaled and exhaled gases passing through said flow pathway;

a component gas concentration sensor operable to generate electrical signals as a function of an instantaneous fraction of a predetermined component gas in said exhaled gases passing through said flow pathway; and

a computation unit operable to receive said electrical signals from said flow meter and said concentration sensor and to calculate at least one respiratory parameter for said subject as said subject breathes through said calorimeter.

23. The calorimeter according to claim 22, wherein said respiratory connector includes:

a mouthpiece; and

a hygiene barrier module including an inlet port for operatively connecting said hygiene barrier module to said mouthpiece and a connecting port for operatively connecting said respiratory connector to a corresponding inlet conduit in fluid communication with said flow pathway, said hygiene barrier being housed within said hygiene barrier module.

24. The calorimeter according to claim 22, wherein said respiratory connector is a mask.

25. The calorimeter according to claim 24, wherein said hygiene barrier is a filtering material.

26. The calorimeter according to claim 25, wherein said respiratory connector is disposable.

27. The calorimeter according to claim 24, wherein said mask further includes a mask shell and a mask liner inserted in said mask shell.

28. The calorimeter according to claim 27, wherein said mask shell is integral and formed as one with an inlet conduit in fluid communication with said flow pathway.

29. The calorimeter according to claim 28, wherein said hygiene barrier is a filtering material.

30. The calorimeter according to claim 29, wherein said mask liner is disposable, and said integral mask shell and inlet conduit are disposable.

31. The calorimeter according to claim 23, wherein said hygiene barrier is a filtering material.

32. The calorimeter according to claim 23, wherein said hygiene barrier module includes a hygiene barrier module includes a hygiene barrier housing including two generally parallel and spaced apart side walls with said hygiene barrier disposed between said side walls.

33. The calorimeter according to claim 32, wherein said hygiene barrier housing includes a lower wall and a saliva retention wall extending upwardly from said lower wall and adjacent said hygiene barrier to form a saliva trap.

61. The calorimeter according to claim 22, wherein said respiratory connector includes:

a respiratory connector housing including an inlet port and a connecting part in fluid communication with said flow pathway; and

a mouthpiece integral with said inlet port,

said hygiene barrier being disposed between said mouthpiece and said connecting port for operatively passing said inhaled and exhaled gases therethrough while blocking said predetermined pathogen in said exhaled gases.

62. The calorimeter according to claim 61, wherein said hygiene barrier is a filtering material.

34. An indirect calorimeter, comprising:

a flow tube configured to pass respiratory gases of a subject;

a flow meter coupled to said flow tube, said flow meter being configured to generate a first signal associated with said respiratory gases passing through said flow tube;

a component gas concentration sensor coupled to said flow tube, said component gas concentration sensor being configured to generate a second signal associated with said respiratory gases passing through said flow tube; and

a computation unit coupled to said flow meter and said component gas concentration sensor, said computation unit being configured to process said first signal and said second signal to determine a volume of said respiratory gases passing through said flow tube and a concentration of oxygen in said respiratory gases passing through said flow tube, said computation unit being configured to determine an amount of oxygen consumed by said subject based on said volume of said respiratory gases passing through said flow tube and said concentration of oxygen in said respiratory gases passing through said flow tube, said computation unit being configured to determine an amount of carbon dioxide produced by said subject based on said volume of said respiratory gases passing through said flow tube and said concentration of oxygen in said respiratory gases passing through said flow tube, said computation unit being configured to determine a resting metabolic rate for said subject based on said amount of oxygen consumed and said amount of carbon dioxide produced.

35. The calorimeter according to claim 34, wherein said flow meter is an ultrasonic flow meter.

36. The calorimeter according to claim 34, wherein said component gas concentration sensor is an oxygen sensor.

37. The calorimeter according to claim 34, wherein said computation unit is further configured to determine said resting metabolic rate for said subject based on said amount of oxygen consumed and an assumed respiratory quotient for said subject.

38. The calorimeter according to claim 37, wherein said assumed respiratory quotient ranges from 0.7 to 1.1.

39. The calorimeter according to claim 38, wherein said assumed respiratory quotient is 0.85.

40. An indirect calorimeter, comprising:

a first sensor configured to generate an output associated with a volume of inhaled gases of a subject and a volume of exhaled gases of said subject;

a second sensor configured to generate an output associated with a fraction of oxygen in said exhaled gases, said second sensor being a fluorescence quench oxygen sensor; and

a processing unit coupled to said first sensor and said second sensor, said processing unit being configured to process said output of said first sensor and said output of said second sensor to determine an amount of carbon dioxide produced by said subject.

41. The calorimeter according to claim 40, wherein said first sensor is a flow meter.

42. The calorimeter according to claim 41, wherein said flow meter includes a plurality of ultrasonic transducers.

43. The calorimeter according to claim 40, wherein said processing unit is configured to process said output of said first sensor and said output of said second sensor to determine an amount of oxygen consumed by said subject.

44. The calorimeter according to claim 43, wherein said processing unit is configured to determine a resting metabolic rate for said subject based on said amount of oxygen consumed and said amount of carbon dioxide produced.

45. The calorimeter according to claim 40, further comprising:

a flow tube configured to pass said inhaled gases and said exhaled gases as said subject breathes, said first sensor and said second sensor being coupled to said flow tube.

46. The calorimeter according to claim 45, further comprising:

a hygiene barrier module coupled to said flow tube, said hygiene barrier module being configured to block a predetermined pathogen from said exhaled gases.

47. An indirect calorimeter, comprising:

means for generating a first output associated with a volume of respiratory gases of a subject;

means for generating a second output associated with a concentration of oxygen in said respiratory gases; and

means for processing said first output and said second output to determine a resting metabolic rate for said subject, said means for processing said first output and said second output including;

means for determining an amount of oxygen consumed by said subject based on said volume of said respiratory gases and said concentration of oxygen in said respiratory gases; and

means for determining said resting metabolic rate based on said amount of oxygen consumed and an assumed respiratory quotient for said subject.

48. The calorimeter according to claim 47, wherein said means for processing said first output and said second output further includes:

means for determining an amount of carbon dioxide produced by said subject based on said volume of said respiratory gases and said concentration of oxygen in said respiratory gases; and

means for determining said resting metabolic rate based on said amount of oxygen consumed and said amount of carbon dioxide produced.

49. The calorimeter according to claim 47, wherein said assumed respiratory quotient ranges from 0.7 to 1.1.

50. The calorimeter according to claim 49, wherein said assumed respiratory quotient is 0.85.

51. An indirect calorimeter, comprising:

a flow tube configured to pass inhaled gases and exhaled gases of a subject;

a flow meter coupled to said flow tube, said flow meter being configured to generate an output associated with a volume of said inhaled gases and a volume of said exhaled gases;

a component gas concentration sensor coupled to said flow tube, said component gas concentration sensor being configured to generate an output associated with a concentration of oxygen in said exhaled gases;

a temperature sensor configured to generate an output associated with ambient temperature;

a pressure sensor configured to generate an output associated with ambient pressure;

a humidity sensor configured to generate an output associated with relative humidity; and

a computation unit coupled to said flow meter, said component gas concentration sensor, said temperature sensor, said pressure sensor, and said humidity sensor said computation unit being configured to process said output of said flow meter and said output of said component gas concentration sensor to determine at least one respiratory parameter for said subject, said computation unit being configured to process said output of said temperature sensor, said output of said pressure sensor, and said output of said humidity sensor to determine said at least one respiratory parameter.

52. The calorimeter according to claim 51, wherein said component gas concentration sensor is an oxygen sensor.

53. The calorimeter according to claim 52, wherein said oxygen sensor is a fluorescence quench oxygen sensor.

54. The calorimeter according to claim 51, wherein said output of said component gas concentration sensor is further associated with a concentration of oxygen in said inhaled gases.

55. The calorimeter according to claim 51, wherein said computation unit is configured to process said output of said flow meter and said output of said component gas concentration sensor to determine an amount of oxygen consumed by said subject and an amount of carbon dioxide produced by said subject, said computation unit being configured to determine said at least one respiratory parameter based on said amount of oxygen consumed and said amount of carbon dioxide produced.

56. The calorimeter according to claim 55, wherein said computation unit is configured to determine said amount of oxygen consumed based on said volume of said inhaled gases, said volume of said exhaled gases, and said concentration of oxygen in said exhaled gases.

57. The calorimeter according to claim 55, wherein said computation unit is configured to determine said amount of carbon dioxide produced based on said volume of said inhaled gases, said volume of said exhaled gases, and said concentration of oxygen in said exhaled gases.

58. The calorimeter according to claim 51, further comprising;

a respiratory connector coupled to said flow tube, said respiratory connector being configured to be supported in contact with said subject so as to pass said inhaled gases and said exhaled gases.

59. The calorimeter according to claim 51, wherein said flow meter is an ultrasonic flow meter.

60. The calorimeter according to claim 58, further comprising:

a hygiene barrier module coupled to said respiratory connector and said flow tube, said hygiene barrier module being configured to block a predetermined pathogen from said exhaled gases.