Testing of body fluid constituents through measuring light reflected from tympanic membrane

• US 5,115,133 A
• Filed: 04/19/1990
• Issued: 05/19/1992
• Est. Priority Date: 04/19/1990
• Status: Expired due to Term

• Current Assignee: Inomet, Inc.
• Original Assignee: Inomet, Inc.
• Inventors: Knudson, Mark B.
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): BEYER, JAMES
• Application Number:
  US07/510,935
• Time in Patent Office: 761 Days
• Field of Search: 356/41, 250/341, 250/343, 128/633, 128/664
• US Class Current: 250/339.03
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/1491 Heated applicators
• CPC Class Codes: A61B 5/6817 Ear canal

Abstract

An apparatus and method are disclosed for determining a level of a constituent such as glucose in a body fluid such as blood. The apparatus and method utilize a light generator for generating a testing light of known intensity with the testing light including a wavelength absorbable by the constituent being measured. The light generator also generates a reference light of known intensity having a wavelength not absorbable by the constituent being measured. The testing light and reference light are directed toward a fluid containing an unknown concentration of a constituent. A light detector is provided for measuring the intensity of the testing light and reference light being spectrally modified by the fluid. A light path distance measurer is provided for measuring a distance of a light path traveled by the testing light and reference light. A circuit is provided for calculating a level of the constituent in the fluid in response to a reduction in intensity of the testing light and reference light and in response to the measured distance.

Claims

1. An apparatus for determining a level of a constituent in a body fluid, said apparatus comprising

light generating means for generating a testing light of known intensity with said testing light including at least one wavelength absorbable by said constituent and directing said testing light toward said fluid;

light detecting means for measuring an intensity of said testing light reflected from said fluid;

light path measurement means for measuring an actual distance of a light path from said light generating means to said light detecting means via said fluid;

circuit means for calculating a level of said constituent in said fluid in response to a reduction in intensity of said testing light between said light generating means and said light detecting means and in response to said actual distance measured by said light path measurement means.

2. An apparatus according to claim 1 wherein said light generating means includes means for generating at least two wavelengths including said testing light and a reference light of known intensity having at least one wavelength not absorbable by said constituent, said light detecting means including means for measuring said testing light and said reference light reflected from said fluid and said circuit means including means for comparing said measured intensities and using said measured intensity of said reference light as a reference for determining the amount of said testing light absorbed by said constituent.

3. An apparatus according to claim 2 comprising means for multiplexing said testing and reference lights emitted from said light generating means.

4. An apparatus according to claim 1 comprising heating means for controlling a temperature of said fluid.

5. An apparatus according to claim 1 wherein said light generating means, said light detecting means and said light path measurement means are disposed at a distal end of a housing.

6. An apparatus according to claim 5 wherein said body fluid is contained within a tympanic membrane and wherein said housing is sized to be received within an auditory canal of an ear with said distal end opposing said tympanic membrane.

7. An apparatus according to claim 6 wherein said distal end includes a material selected to pass said absorbable wavelength.

8. An apparatus according to claim 7 wherein said absorbable wavelength is infrared.

9. An apparatus according to claim 1 wherein said testing light includes a plurality of wavelengths absorbable by a plurality of different constituents and wherein said circuit means includes means for separately calculating the level of each of said constituents in response to a measured intensity of each of said wavelengths reflected from said fluid.

10. An apparatus according to claim 6 wherein said housing includes means for blocking ambient light from entering said auditory canal and reaching said distal end.

11. An apparatus according to claim 1 wherein said fluid is blood.

12. An apparatus according to claim 11 wherein said constituent is glucose.

13. An apparatus according to claim 1 wherein said fluid is crevicular fluid.

14. An apparatus according to claim 13 wherein said constituent is glucose.

15. An apparatus according to claim 1 wherein said fluid is peritoneal fluid.

16. An apparatus according to claim 15 wherein said constituent is glucose.

17. An apparatus according to claim 1 comprising admitting means for admitting a chemical to a body with a level of said constituent in said body fluid changing in response to an amount of said chemical admitted to said body, control means connecting said circuit means to said admitting means for varying an amount of said chemical admitted to said body in response to a level of said constituent calculated by said circuit means.

18. An apparatus according to claim 6 comprising heating means for heating said tympanic membrane to a temperature sufficient for fluid containing vessels in said tympanic membrane to be open.

19. An apparatus according to claim 6 comprising temperature detection means for detecting a temperature of said tympanic membrane.

20. An apparatus according to claim 19 comprising signal means indicating a measured temperature of said tympanic membrane has exceeded a maximum predetermined temperature range.

21. An apparatus according to claim 1 wherein said at least one wavelength is in a range of about 500 to about 4000 wave numbers.

22. An apparatus according to claim 21 wherein said at least one wavelength is about 1040 wave numbers.

23. An apparatus of determining a level of a blood constituent through non-invasive testing, said apparatus comprising:

light generating means for generating testing light of known intensity and including a wavelength absorbable by said constituent;

light detecting means for measuring an intensity of light;

housing means having a distal end for carrying said light generating means and said light detecting means with said distal end sized to be received within an auditory canal of an ear with said light generating means and said light detecting means opposing a tympanic membrane;

light path measurement means for measuring an actual distance of a light path from said light generating means to said light detecting means via said tympanic membrane;

circuit means for calculating a level of said constituent in blood within blood vessels of said tympanic membrane in response to a reduction of intensity of said testing light between said light generating means and said light detecting means and in response to said measured actual distance.

24. An apparatus according to claim 23 wherein said light generating means includes means for generating at least two wavelengths including said testing light and the reference light having a wavelength not absorbable by said constituent, said light detecting means including means for measuring said testing light and said reference light reflected from said tympanic membrane, and in said circuit means including means for comparing said measured intensities and using said measured intensity of said reference light as a reference for determining the amount of said testing light absorbed by said constituent.

25. An apparatus according to claim 24 comprising means for multiplexing said testing and reference lights emitted from said light generating means.

26. An apparatus according to claim 23 comprising heating means for heating said tympanic membrane to a temperature sufficient for said blood vessels to be unrestricted.

27. An apparatus according to claim 23 wherein said distal end includes a material selected to pass said absorbable wavelength.

28. An apparatus according to claim 27 wherein said absorbable wavelength is infrared.

29. An apparatus according to claim 23 wherein said testing light includes a plurality of wavelengths absorbable by a plurality of different constituents wherein said circuit means includes means for separately calculating a level of each of said constituents in response to a measured intensity of each of said wavelengths reflected from said tissue

30. An apparatus according to claim 23 wherein said housing includes means for blocking ambient light from entering said auditory canal and reaching said distal end.

31. An apparatus according to claim 23 wherein said constituent is blood glucose.

32. An apparatus according to claim 23 wherein said wavelength is in a range of about 500 to about 4000 wave numbers.

33. An apparatus, according to claim 32 wherein said wavelength is about 1040 wave numbers.

34. A method of non-invasive testing of a blood constituent utilizing light generating means for generating a testing light of known intensity and including a wavelength absorbable by said constituent, light detecting means for measuring an amount of light reflected from a tissue containing blood, light path measurement means for measuring a distance of a light path from said light generating means to said light detecting means via said tissue and circuit means for calculating a level of said constituent in said tissue in response to a reduction in intensity of said testing light said light generating means and said light detecting means and in response to said measured distance, said method including the steps of:

locating said light generating means in a location for light from said light generating means to be directed to a tympanic membrane and reflected back toward said light detecting means;

directing said testing light to said tympanic membrane;

measuring an intensity of said testing light reflected by said tympanic membrane;

measuring an actual distance of said light path from said light generating means to said light detecting means via said tympanic membrane; and

calculating a level of said constituent by comparing said measured and known intensities and allowing for an effect of said measured actual distance.

35. A method according to claim 34 wherein said method utilizes heating means for heating said tympanic membrane and said method includes the steps of heating said tympanic membrane to a temperature sufficient for blood vessels in said tympanic membrane to be unrestricted.

36. A method according to claim 34 wherein said light generating means includes means for generating at least two wavelengths including said testing light and a reference light of known intensity having a wavelength non-absorbable by said constituent, said light detecting means including means for measuring said testing light and said reference light reflected from said tympanic membrane and said circuit means including means for comparing said measured intensities and using said measured intensity of said reference light as a reference for determining the amount of said testing light absorbed by said constituent, said method including the step of directing said reference light towards the tympanic membrane and measuring an intensity of said reference light reflected off said tympanic membrane and calculating a level of said constituent by comparing a measured intensity of said reference light to a measured intensity of said testing light.

37. A method according to claim 36 comprising multiplexing said reference light and said testing light at said light generating means.

38. A method according to claim 34 wherein said constituent is glucose.

39. A method according to claim 34 wherein said wavelength of said testing light is infrared.

40. A method according to claim 34 wherein said testing light includes a plurality of wavelengths absorbable by a plurality of constituents and wherein said circuit means include the means for separately calculating the level of each of said constituents in response to a measured intensity of each of said wavelengths reflected from said tympanic membrane, said method including the steps of directing each of said plurality of wavelengths to said tympanic membrane and measuring an intensity of each wavelength reflected from said tympanic membrane and calculating the level of each of said constituents.

41. A method according to claim 34 wherein said testing light is selected to have at least a wavelength in a range of about 500 to 4000 wave numbers.

42. A method according to claim 41 wherein said testing light is selected to have at least a wavelength of about 1040 wave numbers.

43. An apparatus for determining a level of a constituent in a body fluid, said apparatus comprising:

light generating means for generating a source light including at least one wavelength absorbable by the constituent;

directing means for directing said source light to a tympanic membrane;

light detection means for detecting light reflected from said tympanic membrane and producing an output signal indicative of an amount of absorption of said light by said tympanic membrane; and

processing means for receiving said output signal and calculating an amount of said constituent in a body fluid within said tympanic membrane.

44. An apparatus according to claim 43 wherein said at least one wavelength is in a range of about 500 to about 4000 wave numbers.

45. An apparatus according to claim 44 wherein said at least one wave numbers is about 1040 wavelengths.

46. An apparatus according to claim 43 wherein said light generating means includes means for generating at least two wavelengths including said source light and a reference light of known intensity having at least one wavelength not absorbable by said constituent, said light detection means including means for measuring said source light and said reference light reflected from said tympanic membrane and said processing means including means for comparing said measured intensities and using said measured intensity of said reference light as a reference for determining the amount of said source light absorbed by said constituent.

47. An apparatus according to claim 46 comprising means for multiplexing said source and reference lights emitted from said light generating means.

48. An apparatus according to claim 43 comprising heating means for controlling a temperature of said tympanic membrane.

49. An apparatus according to claim 43 wherein said light generating means and said light detection means are disposed at a distal end of a housing.

50. An apparatus according to claim 49 wherein said housing is sized to be received within an auditory canal of an ear with said distal end opposing said tympanic membrane.

51. An apparatus according to claim 50 wherein said distal end includes a material selected to pass said absorbable wavelength.

52. An apparatus according to claim 51 wherein said absorbable wavelength is infrared.

53. An apparatus according to claim 43 wherein said source light includes a plurality of wavelengths absorbable by a plurality of different constituents and wherein said processing means includes means for separately calculating the level of each of said constituents in response to a measured intensity of each of said wavelengths reflected from said tympanic membrane.

54. An apparatus according to claim 50 wherein said housing includes means for blocking ambient light from entering said auditory canal and reaching said distal end.

55. An apparatus according to claim 43 wherein said fluid is blood.

56. An apparatus according to claim 55 wherein said constituent is glucose.

57. An apparatus according to claim 43 comprising admitting means for admitting a chemical to a body with a level of said constituent in said body fluid changing in response to awn amount of said chemical admitted to said body, control means connecting said processing means to said admitting means for varying an amount of said chemical admitted to said body in response to a level of said constituent calculated by said processing means.

58. An apparatus according to claim 49 comprising heating means for heating said tympanic member to a temperature sufficient for fluid containing vessels in said tympanic membrane to be open.

59. An apparatus according to claim 49 comprising temperature detection means for detecting a temperature of said tympanic membrane.

60. An apparatus according to claim 59 comprising signal means indicating a measured temperature of said tympanic membrane has exceeded a maximum predetermined temperature range.

61. A method for determining a level of a constituent in a body fluid, said method comprising:

generating a source light including at least one wavelength absorbable by the constituent;

directing said source light to a tympanic membrane;

detecting light reflected from said tympanic membrane and producing a signal indicative of an amount of absorption of said light by said tympanic membrane; and

receiving said signal and calculating an amount of said constituent in a body fluid within said tympanic membrane in response to said received signal.

62. A method according to claim 61 wherein said source light is selected to have said at least one wavelength in a range of about 500 to 4000 wave numbers.

63. A method according to claim 62 wherein said at least one wavelength is selected to have a wavelength of about 1040 wave numbers.

64. A method according to claim 61 wherein said method utilizes heating means for heating said tympanic membrane to a temperature sufficient for blood vessels in said tympanic membrane to be unrestricted.

65. A method according to claim 61 wherein further comprising the step of directing a reference light of known intensity having a wavelength non-absorbable by said constituent towards the tympanic membrane and measuring an intensity of said reference light reflected off said tympanic membrane and calculating a level of said constituent by comparing a measured intensity of said reference light to a measured intensity of said source light.

66. A method according to claim 65 comprising multiplexing said reference light and said source light at said light generating means.

67. A method according to claim 65 wherein said constituent is glucose.

68. A method according to claim 65 wherein said wavelength of said source light is infrared.

69. A method according to claim 65 wherein said source light includes a plurality, said method including the steps of directing each of said plurality of wavelengths to said tympanic membrane and measuring an intensity of each wavelength reflected from said tympanic membrane and calculating the level of each of said constituents.