Physiological stress detector device and method

• US 6,553,242 B1
• Filed: 02/01/2000
• Issued: 04/22/2003
• Est. Priority Date: 06/15/1997
• Status: Expired due to Term

• Current Assignee: SPO Medical Equipment, Ltd. (SPO Global, Inc.)
• Original Assignee: SPO Medical Equipment, Ltd. (SPO Global, Inc.)
• Inventors: Sarussi, Israel
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): Kremer, Matthew J
• Application Number:
  US09/147,683
• Time in Patent Office: 1,176 Days
• Field of Search: 600/309-310, 600/315, 600/322-326, 600/330, 600/336, 600/478-479, 356/39-41
• US Class Current: 600/330
• CPC Class Codes: A61B 2503/06 Children, e.g. for attention deficit diagnosis
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/6828 Leg
• CPC Class Codes: A61B 5/6829 Foot or ankle

Abstract

A method and device for measurement of a level of at least one blood constituent. The device includes a light source and a light detector proximate the surface of an organ. The device also includes a pair of adjustable gain amplifiers and a processor/controller connected within a processing unit. The processing unit operates to separate an AC signal component from a DC signal component. The light source includes at least one light emitting unit. Preferably, the light source alternatingly emits light at two different wavelength ranges and normalizes the AC and DC output signals corresponding with the intensity of the light reflected from the organ and calculates a ratio of the normalized signals for each wavelength range. The device may determine the level of the blood constituent and may also use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range. The device and the method may be applied to monitoring, inter alia, conditions of apnea, respiratory stress, reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity.

Claims

1. A non-invasive device disposed proximate a surface of an organ for measurement of a level of at least one blood constituent, comprising:

at least one light source, providing light directed toward said surface of said organ, the light being reflected from said organ;

a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said reflected light for producing intensity signals in accordance therewith; and

a processing unit for processing said intensity signals received from said light detector, said processing unit comprising;

first and second amplifiers for amplifying said intensity signals, each in accordance with a respective first and second gain amplification factor; and

a processor for automatically determining said first and second gain amplification factors in adjustable fashion;

wherein during a first stage, said first and second amplifiers amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, and wherein the amplified DC signal component is converted by a digital to analog converter to an analog signal and is subtracted from the intensity signals, said amplified DC signal component being subtracted from said intensity signals at an input of said first amplifier, to isolate an AC signal component of said intensity signals,

and wherein during a second stage, said second amplifier amplifies said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor,

said processing unit producing output signals in accordance with said isolated AC signal component and said DC signal component and calculating in accordance therewith, at least one blood constituent level.

2. The device according to claim 1 wherein said processor develops a control signal when said adjustably-determined second gain amplification factor is established in said second stage, said control signal is able to shut off said light source.

3. The device according to claim 2 wherein said control signal conserves energy by reducing an operational duty cycle of said at least one light source.

4. The device according to claim 1 wherein said at least one light source comprises a single light emitting unit capable of controllably providing light having a wavelength range selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range, said single light emitting unit can be switched from emitting light within said first wavelength range to emitting light within said second wavelength range.

5. The device according to claim 1 wherein said at least one light source provides light having wavelengths in the red and infrared ranges.

6. The device according to claim 5 wherein said organ is the skin, said blood constituent is hemoglobin, and wherein measurement of a level of oxygen saturation in said hemoglobin provides an early indication of respiratory stress.

7. The device according to claim 6 wherein said respiratory stress is associated with Sudden Infant Death Syndrome.

8. The device according to claim 6 used to monitor heart rate.

9. The device according to claim 6 used as an apnea monitor.

10. The device according to claim 6 wherein the device is a portable hand held reflective pulse oximeter.

21. The device according claim 1 or 11 wherein said at least one light source and said light detector are held in a spaced relationship while in contact with the surface of said organ so as to substantially block entrance of external light therebetween.

22. The device according to claim 1 or 11 wherein said processing unit further comprises:

means for normalizing said output signals to produce first and second normalized signals; and

means for forming a ratio of said first and second normalized signals, said processor calculating said blood constituent level in accordance with said ratio.

23. The device according to claim 1 or 11 wherein said organ is the skin and said device is arranged for mounting on a ribbon or a bracelet for placement on a part of a human or an animal body.

24. The device according to claim 1 or 11 wherein said organ is the skin and said device is arranged for mounting on a tightly-fitted garment to be worn over a part of the body.

25. The device according to claim 1 or 11 further comprising a transmitter for transmitting said output signals to a receiver at a remote location, allowing monitoring of said at least one blood constituent level from said remote location,

said receiver being equipped with an alarm unit for alerting when said at least one blood constituent level falls outside of a predetermined range.

26. The device according to claim 1 or 11 wherein said first and second gain amplification factors are determined by said processor in an iterative process by adjustably setting a gain amplification factor and measuring a dynamic voltage range of said output signals to determine if said voltage range falls within a predetermined window established by said processor.

27. The device according to claim 1 or 11 wherein said light source comprises at least a first light emitting unit capable of controllably emitting light having a first wavelength range and a second light emitting unit capable of controllably emitting light having a second wavelength range, said first wavelength range being at least partially different from said second wavelength range.

28. The device according to claim 1 or 11 wherein said output signals are sent by said processor to an alarm unit for alerting when said at least one blood constituent level falls outside of a predetermined range.

29. The device according to claim 1 or 11 adapted to determine blood bilirubin levels.

30. The device according to claim 1 or 11 used for mapping the intensity of said AC signal component along the surface of said organ to detect regions of said organ having a reduced blood flow.

11. A non-invasive device disposed proximate a surface of an organ for measurement of a level of at least one blood constituent, comprising:

at least one light source, providing light directed toward said surface of said organ, the light being reflected from said organ;

a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said reflected light for producing intensity signals in accordance therewith; and

a processing unit for processing said intensity signals received from said light detector, wherein processing the intensity signals is done through a single analog path, said processing unit comprising;

first and second amplifiers for amplifying said intensity signals, each in accordance with a respective first and second gain amplification factor; and

a processor for automatically determining said first and second gain amplification factors in adjustable fashion;

wherein during a first stage, said first and second amplifiers amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, said amplified DC signal component being subtracted from said intensity signals at an input of said first amplifier, to isolate an AC signal component of said intensity signals,

and wherein during a second stage, said second amplifier amplifies said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor,

said processing unit producing output signals in accordance with said isolated AC signal component and said DC signal component and calculating in accordance therewith, at least one blood constituent level.

12. The device according to claim 11 wherein said at least one light source comprises a single light emitting unit capable of controllably providing light having a wavelength range selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range, said single light emitting unit can be switched from emitting light within said first wavelength range to emitting light within said second wavelength range.

13. The device according to claim 11 wherein said processor develops a control signal when said adjustably-determined second gain amplification factor is established in said second stage, said control signal is able to shut off said light source.

14. The device according to claim 13 wherein said control signal conserves energy by reducing an operational duty cycle of said at least one light source.

15. The device according to claim 11 wherein said at least one light source provides light having wavelengths in the red and infrared ranges.

16. The device according to claim 15 wherein said organ is the skin, said blood constituent is hemoglobin, and wherein measurement of a level of oxygen saturation in said hemoglobin provides an early indication of respiratory stress.

17. The device according to claim 16 wherein said respiratory stress is associated with Sudden Infant Death Syndrome.

18. The device according to claim 16 used to monitor heart rate.

19. The device according to claim 16 used as an apnea monitor.

20. The device according to claim 16 wherein the device is a portable hand held reflective pulse oximeter.

31. A method for measurement of a level of at least one blood constituent, the method comprising the steps of:

providing light from at least one light source disposed proximate a skin surface, directing said light toward the skin surface, said light being reflected from said skin surface;

providing a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said light reflected from said skin for producing intensity signals in accordance therewith;

processing said intensity signals received from said light detector, said processing step comprising the steps of;

amplifying said intensity signals in first and second amplifiers, each in accordance with a respective first and second gain amplification factor; and

automatically determining said first and second gain amplification factors in adjustable fashion;

wherein during a first stage, said first and second amplifier amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, and wherein the amplified DC signal component is subtracted from the intensity signals by a digital to analog converter, said DC signal component being subtracted from said intensity signals at an input of said first amplifier, thereby isolating an AC signal component of said intensity signals, and

wherein during a second stage, said second amplifier amplifies said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor, said processing step producing output signals in accordance with said isolated AC signal component and said DC signal component; and

calculating in accordance therewith, said at least one blood constituent level, wherein the amplified DC signal component is converted by a digital to analog converter to an analog signal and is subtracted from the intensity signals.

32. The method according to claim 31 wherein the processing is a serial process.

33. The method according to claim 32 wherein said blood constituent is hemoglobin, the method further comprising the step of measuring a level of oxygen saturation in said hemoglobin providing an early indication of respiratory stress.

34. The method according to claim 33 wherein said respiratory stress is associated with Sudden Infant Death Syndrome.

35. The method according to claim 32 further comprising the step of initiating an alarm for alerting when said at least one blood constituent level falls outside of a predetermined range.

36. The method according to claim 35 wherein said alarm is selected from an audible alarm, a visual alarm, a tactile alarm, dialing a telephone number and any combination thereof.

37. The method according to claim 32 wherein said light is alternatingly selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range.

38. The method according to claim 37 wherein said first wavelength range includes wavelength of red light and said second wavelength range includes wavelength of infra-red light, said at least one blood constituent is hemoglobin and wherein said method determines a level of oxygen saturation of said hemoglobin.

39. The method according to claim 38 used for monitoring heart rate.

40. The method according to claim 38 used for monitoring a condition of apnea.

41. The method according to claim 38 further including the step of repeating said steps of providing light, providing a light detector and processing, at a plurality of positions along said skin for mapping the levels of said AC signal component along the surface of said skin to detect regions of reduced blood flow.

42. The method according to claim 31 further comprising the step of initiating an alarm for alerting when said at least one blood constituent level falls outside of a predetermined range.

43. The method according to claim 42 wherein said alarm is selected from an audible alarm, a visual alarm, a tactile alarm, dialing a telephone number and any combination thereof.

44. The method according to claim 31 wherein said light is alternatingly selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range.

45. The method according to claim 44 wherein said first wavelength range includes wavelength of red light and said second wavelength range includes wavelength of infra-red light, said at least one blood constituent is hemoglobin and wherein said method determines the level of oxygen saturation of said hemoglobin.

46. The method according to claim 45 used for monitoring heart rate.

47. The method according to claim 45 used for monitoring a condition of apnea.

48. The method according to claim 45 further including the step of repeating said steps of providing light, providing a light detector and processing, at a plurality of positions along said skin for mapping levels of said AC signal component along the surface of said skin to detect regions of reduced blood flow.

49. The method according to claim 31 or 32 further comprising the step of transmitting said output signals to a receiver at a remote location, allowing monitoring of said at least one blood constituent level from said remote location, said receiver being equipped with an alarm unit for alerting when said at least one blood constituent level falls outside of a predetermined range.

50. The method according to claim 31 or 32 wherein said step of processing further comprises:

normalizing said output signals to produce first and second normalized signals;

forming a ratio of said first and second normalized signals; and

calculating said blood constituent level in accordance with said ratio.

51. The method according to claim 31 or 32 further comprising the steps of:

developing a control signal when said adjustably-determined second gain amplification factor is established in said second stage; and

shutting off said at least one light source in response to said control signal.

52. The method according to claim 31 or 32 further comprising the steps of:

determining said first and second gain amplification factors by a processor in an iterative process by adjustably setting a gain amplification factor; and

measuring a dynamic voltage range of said output signals to determine if said voltage range falls within a predetermined window established by said processor.

53. The method according to claim 31 wherein said blood constituent is hemoglobin, the method further comprising the step of measuring a level of oxygen saturation in said hemoglobin providing an early indication of respiratory stress.

54. The method according to claim 53 wherein said respiratory stress is associated with Sudden Infant Death Syndrome.

55. The method according to claim 31 or 32 used for monitoring a level of bilirubin in blood.

56. A method for non-invasively determining blood flow velocity in a region of an organ, the method comprising the steps of:

positioning a first pulse-oximetry device and a second pulse-oximetry device proximate a surface of said region, said first and said second device being separated from each other by a predetermined distance;

simultaneously obtaining a first and a second sets of data representing pulsatile variation of a level of oxygen saturation at locations of said first and said second device, respectively, as a function of time, each of said first set and second set of data including at least one extremum data value, said at least one extremum data value of said first set of data corresponding to said at least one extremum data value of said second set of data;

calculating the time interval between said at least one extremum data value of said first set of data and said at least one extremum data value of said second set of data;

dividing the value of said predetermined distance by the value of said time interval to obtain a value representing the approximate blood flow velocity in said region of said organ,

wherein each of said first device and said second device includes;

at least one light source, providing light directed toward the surface of said organ, said light being reflected from said organ;

a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said reflected light for producing intensity signals in accordance therewith; and

a processing unit for processing said intensity signals received from said light detector, said processing unit comprising;

first and second amplifiers for amplifying said intensity signals, each in accordance with a respective first and second gain amplification factor; and

a processor for automatically determining said first and second gain amplification factors in adjustable fashion;

wherein during a first stage, said first and second amplifiers amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, and wherein the amplified DC signal component is subtracted from the intensity signals by a digital to analog converter and is subtracted from said intensity signals at an input of said first amplifier, to isolate an AC signal component of said intensity signals,

and wherein during a second stage, said second amplifier amplifying said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor, said processing unit producing output signals in accordance with said isolated AC signal component and said DC signal component and calculating in accordance therewith, said level of oxygen saturation.

57. The method according to claim 56, wherein the processing is a serial process.

58. The method according to claim 56 wherein said organ is the skin.

59. The method according to claim 56 wherein said at least one extremum data value is selected from a minimum data value a maximum data value.

60. The method according to claim 56 or 57 wherein said organ is an internal organ and wherein said method further includes the step of repeating said steps of providing light, providing a light detector and processing, at a plurality of positions along the surface of said internal organ for mapping levels of said AC signal component along the surface of said internal organ to detect regions of reduced blood