METABOLIC ANALYZER TRANSDUCER

• US 20090227887A1
• Filed: 03/04/2008
• Published: 09/10/2009
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Medical Graphics Corporation (Niterra Co., Ltd.)
• Original Assignee: Medical Graphics Corporation (Niterra Co., Ltd.)
• Inventors: Grimes, Joel, Howard, C. Peter
• Granted Patent: US 8,197,417 B2
• 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 5/0833 Measuring rate of oxygen consumption

Abstract

A compact and wearable metabolic analyzer transducer comprising a housing containing a plurality of analog sensors, an A/D converter, a microcontroller, and a power source operatively coupled thereto where the microcontroller is programmed to compute minute ventilation, O₂ uptake, and CO₂ production of a subject. The transducer and its contents are of a size and weight that can either be easily supported from a facemask worn by a subject or incorporated in a respiratory circuit. The measured values can be wirelessly transmitted or transmitted, via a cable, to a remote personal computer, a personal digital assistant (PDA), or other display devices such as digital watches or image projectors.

Claims

1. A unitary lightweight transducer comprising, in combination:

(a) a housing having a tubular socket with a central lumen;

(b) an oxygen sensor mounted to the housing and exposed to the lumen for producing a first electrical signal proportional to inspired and expired oxygen;

(c) a diatomic gas sensor contained in the housing including an arcuate, open channel having a concave wall with a reflective surface thereon and first and second ends, the first end aligned with an IR source and the second end aligned with an IR detector for producing a second electrical signal proportional to the concentration of a predetermined gas in inspired and expired respiratory air flowing through the transducer;

(d) a flow sensor exposed to respiratory gas flow in the lumen for producing a third electrical signal proportional to the respiratory gas flow, the oxygen sensor, diatomic gas sensor and the flow sensor aligned with a mainstream respiratory gas flow path through the lumen;

(e) an analog-to-digital converter connected to receive the first, second and third electrical signals; and

(f) a microcontroller circuit coupled to the analog-to-digital converter, said oxygen sensor, diatomic gas sensor, flow sensors, analog-to-digital converter and microcontroller circuit being contained in a housing of a size and weight is adapted to be supported on the face of a subject whose oxygen uptake and carbon dioxide production are to be measured.

2. The unitary lightweight transducer as in claim 1 wherein said housing comprises;

(a) an outer shell having a first wall, a second wall and a side wall joining the first wall to the second wall and defining a hollow chamber and where the second wall and first wall each include a centrally disposed aperture;

(b) a detector mounting structure contained in the hollow chamber, the detector mounting structure having a base with a central aperture concentrically aligned with the apertures in the first wall and second wall and with the tubular socket projecting outward of the base; and

(c) an optical waveguide member dimensioned to fit within said tubular socket, the optical waveguide member having a tubular sidewall and a base, the tubular sidewall containing said arcuate, open channel and the base having an orifice of a predetermined shape and size, and where a portion of the tubular sidewall of the optical waveguide member extends through the aperture in the first wall.

3. The unitary lightweight transducer as in claim 2 wherein the arcuate open channel comprises a reflective surface and is exposed to respiratory air made to flow through the aperture in the second wall.

4. The unitary lightweight transducer as in claim 2 wherein the oxygen sensor comprises a galvanic fuel cell is disposed in a holder joined to the tubular socket of the detector mounting structure and is exposed to respiratory air made to flow through the aperture in the bottom wall.

5. The lightweight breath-by-breath metabolic analyzer transducer as in claim 2 wherein the flow sensor includes an electronic pressure sensor operatively disposed on opposite sides of said base of the optical waveguide member and configured to measure a pressure drop across the base due to air flow through an orifice in the base of the waveguide member.

6. The unitary lightweight transducer as in claim 2 and further including an absolute temperature sensor affixed to the detector mounting structure and exposed to respiratory air passing through the tubular socket, past the detector mounting structure and through the optical waveguide member.

7. The unitary lightweight transducer as in claim 2 wherein the analog-to-digital converter is mounted on a first printed circuit substrate disposed in a first space between the outer shell and the tubular socket of the housing.

8. The unitary lightweight transducer as in claim 7 and further including a second printed circuit substrate having the microcontroller circuit affixed thereto, the second substrate being disposed in a second space between the outer shell and the tubular socket of the housing.

9. The unitary lightweight transducer as in claim 8 and further including a power supply disposed in the housing and operatively coupled to the analog-to-digital converter and the microcontroller circuit.

10. The unitary lightweight transducer as in claim 9 wherein the power supply disposed in the housing is operatively coupled to the IR source and the IR detector.

11. The unitary lightweight transducer as in claim 10 wherein the IR source is an incandescent lamp.

12. The unitary lightweight transducer as in claim 9 wherein the power supply comprises a battery disposed in said housing and operatively coupled to the flow sensor the IR source and the IR detector.

13. The unitary lightweight transducer as in claim 2 wherein said housing and contents weigh less than 5 oz.

14. The unitary lightweight transducer as in claim 1 and further including a wireless transmitter disposed in the housing and coupled to the microcontroller circuit for sending computed values of oxygen uptake and carbon dioxide production to a remote receiver.

15. The unitary lightweight transducer as in claim 1 and further including a serial data input channel on the microcontroller adapted to receive heart rate signals from an external heart rate sensor over a wireless communications link.

16. The unitary lightweight transducer as in claim 3 wherein the IR source is operatively positioned to inhibit moisture condensation on the reflective surface.

17. A lightweight respiratory gas concentration transducer comprising, in combination:

(a) a tubular housing having a respiratory gas flow channel extending from a proximal end to a distal end of said housing; and

(b) a diatomic gas detector module disposed in said housing in alignment with the gas flow channel, said detector module having an optical waveguide member with an arcuate, open groove with a concave wall, the concave wall having a reflective surface thereon and said groove having first and second ends, the first end aligned with an IR source and the second end aligned with an IR detector, the open groove adapted to receive samples of inspired and expired air from a subject on whom the transducer is attached.

18. The lightweight respiratory gas concentration transducer of claim 17 and further including an oxygen sensor mounted on the detector module and exposed to respiratory gas flowing through the gas flow channel.

19. The lightweight respiratory gas concentration transducer of claim 18 and further including a flow sensor in the housing for measuring the volume rate of flow of respiratory gas through the flow channel.

20. The lightweight respiratory gas concentration transducer of claim 19 and further including a temperature measuring device and a barometric pressure sensor affixed to the housing.

21. The lightweight respiratory gas concentration transducer of claim 20 and further including a dc power supply disposed in the tubular housing for providing power to the IR source, the IR detector, the oxygen sensor and the temperature sensor.

22. The lightweight respiratory gas concentration transducer of claim 21 and further including a microcontroller disposed in the housing and connected to the IR source, the IR sensor, the oxygen sensor, the temperature sensor, the dc power supply, the flow sensor and the barometric pressure sensor for computing the subjects oxygen uptake and carbon dioxide production on a breath-by-breath basis.

23. The lightweight respiratory gas concentration transducer of claim 22 and wherein said microcontroller includes a serial communication channel comprising a transceiver disposed in said housing for communication with a remote computer.

24. The lightweight respiratory gas concentration transducer of claim 22 wherein the microcontroller controls the intensity of the IR source.

25. The lightweight respiratory gas concentration transducer of claim 17 wherein the reflective surface comprises a thin film of gold deposited on the concave wall.

26. A metabolic analyzer transducer, comprising

a housing capable of being coupled to a facemask and comfortably worn by a subject;

an analog sensor located within the housing;

a microcontroller located within the housing capable of receiving inputs from the analog sensor and compute CO₂ production by the subject; and

a power source located within the housing operatively coupled to the microcontroller.

27. The metabolic analyzer transducer of claim 26, further comprising an O₂ sensor located within the housing.

28. The metabolic analyzer transducer of claim 26, further comprising a wireless transmitter located within the housing.

29. The metabolic analyzer transducer of claim 28, wherein the wireless transmitter can transmit measured physiological values.

30. The metabolic analyzer transducer of claim 29, wherein the measured physiological values can be transferred to a remote device via a wireless connection.

31. The metabolic analyzer transducer of claim 30, wherein the remote devices can be any one of a personal computer, personal digital assistant, cell phone, or a Bluetooth capable device.

32. The metabolic analyzer transducer of claim 26, further comprising a respiratory gas analyzer within the housing.

33. The metabolic analyzer transducer of claim 32, further comprising a flow sensor within the housing.

34. The metabolic analyzer transducer of claim 33, further comprising an absolute temperature sensor within the housing.

35. The metabolic analyzer transducer of claim 34, further comprising an analog-to-digital converter capable of receiving inputs from any of the sensors within the housing.

36. A metabolic analyzer transducer system, comprising:

a metabolic analyzer transducer able to sense and compute CO₂ production by a subject;

a facemask for operably coupling the metabolic analyzer transducer to the subject; and

a user interface communicatively coupled to the metabolic analyzer transducer.

37. The metabolic analyzer transducer system of claim 36, further comprising an ergometer.

38. The metabolic analyzer transducer system of claim 37, wherein the user interface and ergometer are contained in one device.

39. The metabolic analyzer transducer system of claim 38, wherein the ergometer is a stationary bicycle.

40. The metabolic analyzer transducer system of claim 36, further comprising a wireless connection device housed on the metabolic analyzer transducer for communicatively coupling the metabolic analyzer transducer with the user interface.

41. The metabolic analyzer transducer system of claim 40, wherein the wireless connection device is a Bluetooth wireless transceiver.

42. The metabolic analyzer transducer system of claim 36, wherein the facemask can support 5 oz. or less.

43. The metabolic analyzer transducer system of claim 36, further comprising a sensor housed by the metabolic analyzer transducer for detecting CO₂.

44. The metabolic analyzer transducer system of claim 43, further comprising a microcontroller housed in the metabolic analyzer transducer capable of receiving inputs from the CO₂ sensor.

45. The metabolic analyzer transducer system of claim 37, wherein the ergometer can be any one of a treadmill, elliptical machine, stair machine, bike, cross or a country trainer.

46. A method of manufacturing a metabolic analyzer transducer comprising the steps of:

(a) molding an outer plastic shell having a bottom wall, a top wall and a side wall joining the top wall to the bottom wall and defining a hollow chamber where the bottom wall and top wall each include a centrally disposed aperture;

(b) placing a detector mounting structure in the hollow chamber, the detector mounting structure having a base with a central aperture concentrically aligned with the apertures in the top wall and bottom wall and with a tubular socket projecting outward of the base; and

(c) inserting an optical waveguide member within said tubular socket, the optical waveguide member having a tubular sidewall and a base containing said arcuate, open channel and an orifice of a predetermined shape and size in the base, and where a portion of the tubular sidewall of the optical waveguide member extends through the aperture in the top wall.

47. The method of claim 46, further comprising the step of inserting an oxygen sensor for producing a first electrical signal proportional to inspired and expired oxygen into the central aperture.

48. The method of claim 47, further comprising the step of attaching a diatomic gas sensor to the detector mounting structure, the diatomic gas sensor including said arcuate, open channel said channel having a concave wall with a reflective surface thereon and first and second ends, the first end aligned with an IR source and the second end aligned with an IR detector for producing a second electrical signal proportional to the concentration of a predetermined gas in inspired and expired respiratory air flowing through the orifice;

49. The method of claim 48, further comprising the step of attaching a flow sensor to the detector mounting structure, the flow sensor producing a third electrical signal proportional to a pressure drop across said orifice, the oxygen sensor, diatomic gas sensor and the flow sensor aligned with a mainstream respiratory gas flow path.

50. The method of claim 49, further comprising the step of coupling an analog-to-digital converter to the detector mounting structure, the analog-to-digital converter connected to receive the first, second and third electrical signals.

51. The method of claim 50, further comprising the step of coupling a microcontroller circuit to the detector mounting structure, the microcontroller circuit coupled to the analog-to-digital converter, said oxygen sensor, diatomic gas sensor, flow sensors, and analog-to-digital converter.

52. The method of claim 51, wherein the metabolic analyzer transducer is of a size and weight adapted to be supported by a facemask to be worn by a subject whose oxygen uptake and carbon dioxide production are to be measured.

53. The method of claim 52, wherein the arcuate open channel is exposed to respiratory air made to flow through the aperture in the bottom wall.

54. The method of claim 53, wherein the oxygen sensor comprises a galvanic fuel cell disposed in a holder joined to the tubular socket of the detector mounting structure and is exposed to respiratory air made to flow through the aperture in the bottom wall.

55. The method of claim 54, wherein the flow sensor includes electronic pressure sensors operatively disposed on opposite sides of said base of the optical waveguide member and configured to measure a pressure drop across the base due to air flow through said orifice in the base of the waveguide member.

56. A method of manufacturing a lightweight respiratory gas concentration transducer comprising, comprising the steps of:

(a) molding a tubular housing having a respiratory gas flow channel extending from a proximal end to a distal end of said housing; and

(b) placing a diatomic gas detector module in said housing in alignment with the gas flow channel, said detector module having an optical waveguide member with an arcuate, open groove with a concave wall, the concave wall having a reflective surface thereon and said groove having first and second ends, the first end aligned with an IR source and the second end aligned with an IR detector, the open groove adapted to receive samples of inspired and expired air from a subject on whom the transducer is attached.

57. The method of claim 56, further comprising the step of mounting an oxygen sensor on the detector module and exposing to respiratory gas flowing through the gas flow channel.

58. The method of claim 57, further comprising the step of forming an orifice in a base of the optical waveguide member for measuring a pressure drop across said base due to gas flow through said orifice.

59. The method of claim 58, further comprising the step of affixing a temperature measuring device and a barometric pressure sensor to the housing.

60. The method of claim 59, further comprising the step of inserting a dc power source in the tubular housing for providing power to the electronics and sensors.

61. The method of claim 60, further comprising the step of inserting a microcontroller in the housing.

62. The method of claim 61, further comprising the step of connecting the microcontroller to the IR source, the IR sensor, the oxygen sensor, the temperature sensor, the dc power supply, the flow sensor and the barometric pressure sensor for computing the subject'"'"'s oxygen uptake and carbon dioxide production on a breath-by-breath basis.

63. The method of claim 62, wherein the microcontroller includes a serial communication channel comprising a transceiver disposed in said housing for communication with a remote computer.

64. The method of claim 63, wherein the microcontroller controls the intensity of the IR source

65. The method of claim 64, wherein the reflective surface comprises a thin film of gold deposited on the concave wall.

66. A method of measuring a metabolic rate of a subject, comprising the steps of:

measuring CO₂ with an analog sensor located within a housing coupled to a facemask;

receiving inputs from the analog sensor at a microcontroller and computing CO₂ production by the subject, the microcontroller located within the housing; and

powering the analog sensor and microcontroller with a power source located within the housing operatively coupled to the microcontroller and analog sensor.

67. The method of claim 66, further comprising the step of measuring O₂ with an O₂ sensor located within the housing.

68. The method of claim 67, further comprising the step of transmitting measured physiological values of the subject with a wireless transmitter located within the housing.

69. The method of claim 67, further comprising the step of transferring physiological values of the subject to a remote device via a wireless connection.

70. The method of claim 67, further comprising the step of measuring air flow with a flow sensor located within the housing.

71. The method of claim 70, further comprising the step of measuring respired air from the subject with a respiratory gas analyzer located within the housing.

72. The method of claim 71, further comprising the step of measuring temperature with an absolute temperature sensor located within the housing.

73. The method of claim 72, further comprising the step of zeroing a flow transducer during each breath.

74. The method of claim 73, further comprising the step of zeroing CO₂.

75. The method of claim 74, further comprising the step of spanning 0₂ on a breath by breath basis.

76. The method of claim 75, further comprising the step of correcting an 0₂ signal from flow to yield a pressure compensated 02 output.

77. The method of claim 76, further comprising the step of augmenting the 0₂ signal to provide real-time breath by breath measurements and removal of DC drift.