Pulse oximeter

• US 20040034294A1
• Filed: 08/16/2002
• Published: 02/19/2004
• Est. Priority Date: 08/16/2002
• Status: Active Grant

• Current Assignee: Optical Sensors Incorporated
• Original Assignee: Optical Sensors Incorporated
• Inventors: Kimball, Victor E., LaPlante, Paulita
• Granted Patent: US 6,763,256 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/043 in a linear array
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1464 specially adapted for foetal tissue
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

There is a need for a technique to compensate for, or eliminate, motion-induced artifacts in patient-attached critical care monitoring instruments. Also, a need exists to extend the accurate operational range of patient-attached pulse oximeters in environments when the patient'"'"'s blood oxygen saturation is well below the normal physiologic range, or where there is low blood flow. Accordingly, the invention is directed to improving pulse-oximetry by incorporating additional signals to aid in the triggering of the pulse-oximeter or in analyzing the data received by the pulse oximeter. These approaches include measuring a pulsatile characteristic of the patient at a position close to, or at the pulse-oximetry measurement site, or using pulsatile characteristics that result from contraction of the patient'"'"'s heart.

Claims

1. A method of determining hemoglobin oxygen saturation at a measurement site on a patient, comprising:

detecting a first pulsatile characteristic of the patient proximate the measurement site;

making hemoglobin oxygen saturation measurements at the measurement site; and

analyzing the hemoglobin oxygen saturation measurements made at the measurement site;

wherein at least one of i) making the hemoglobin oxygen saturation measurements and ii) analyzing the hemoglobin oxygen saturation measurements is performed in response to the detected first pulsatile characteristic.

2. A method as recited in claim 1, wherein making the hemoglobin saturation measurements includes triggering the hemoglobin oxygen saturation measurements at a predetermined time relative to the first pulsatile characteristic.

3. A method as recited in claim 1, wherein analyzing the hemoglobin oxygen saturation measurements includes modulating hemoglobin oxygen saturation measurement data in response to the first pulsatile characteristic.

4. A method as recited in claim 1, wherein detecting the first pulsatile characteristic includes making a laser Doppler velocimetry (LDV) measurement proximate the measurement site.

5. A method as recited in claim 4, further comprising making the LDV measurement at the measurement site.

6. A method as recited in claim 1, wherein detecting the first pulsatile characteristic includes measuring impedance of the patient proximate the measurement site.

7. A method as recited in claim 6, further comprising measuring the impedance of the patient at the measurement site.

8. A method as recited in claim 1, wherein the hemoglobin oxygen saturation measurement includes taking an optical blood absorption measurement at the measurement site at a time of substantially maximum absorption and taking an optical blood absorption measurement at the measurement site at a time of substantially minimum absorption.

9. A method as recited in claim 8, wherein the times of maximum absorption and minimum absorption correspond to predetermined times relative to a feature of the pulsatile characteristic.

10. A method as recited in claim 1, wherein the measurement site is at a patient'"'"'s digit and the first pulsatile characteristic is detected on the limb to which the digit is attached.

11. A method as recited in claim 10, wherein the first pulsatile characteristic is detected on the lower limb portion of the limb to which the digit is attached.

12. A method as recited in claim 1, wherein the measurement site is at a patient'"'"'s digit and the pulsatile characteristic is detected on one of the patient'"'"'s digits

13. A method as recited in claim 1, wherein the measurement site is at a patient'"'"'s digit and the pulsatile characteristic is detected on the patient'"'"'s digit.

14. A method as recited in claim 1, wherein the measurement site is at the patient'"'"'s buccal region.

15. A method as recited in claim 1, further comprising detecting motion of the patient and wherein one of i) making the hemoglobin oxygen saturation measurements and ii) analyzing the hemoglobin oxygen saturation measurements is performed in response to the detected motion.

16. A method as recited in claim 1, further comprising detecting a second pulsatile characteristic of the patient, wherein the one of i) making the hemoglobin oxygen saturation measurements and ii) analyzing the hemoglobin oxygen saturation measurements is performed in response to the detected second pulsatile characteristic.

17. A method as recited in claim 1, further comprising outputting results related to the first pulsatile characteristic.

18. A method as recited in claim 1, further comprising displaying results related to the first pulsatile characteristic.

19. A method as recited in claim 1, wherein the measurement site is on a neonate'"'"'s head during birth.

64. A method as recited in claim 1, further comprising displaying results related to the first pulsatile characteristic arising from contraction of the patient'"'"'s heart.

20. A system for making measurement of hemoglobin oxygen saturation of a patient at a measurement site, comprising:

means for detecting a pulsatile characteristic of the patient proximate the measurement site;

means for making hemoglobin oxygen saturation measurements at the measurement site; and

means for analyzing the hemoglobin oxygen saturation measurements made at the measurement site;

wherein at least one of i) the means for making the hemoglobin oxygen saturation measurements and ii) the means for analyzing the hemoglobin oxygen saturation measurements responds to the detected pulsatile characteristic.

21. An apparatus for measuring oxygen saturation of hemoglobin at a measurement site on a patient, comprising:

a controller having a first input to receive a first pulsatile input signal based on a first pulsatile patient characteristic measured proximate the measurement site, a first output to control making hemoglobin oxygen saturation measurements and a second input to receive signals related to the measurements of oxygen saturation of hemoglobin made at the measurement site, and having a processor that at least one of i) controls making the hemoglobin oxygen saturation measurements and ii) analyzes the received signals in response to the detected first pulsatile characteristic.

22. An apparatus as recited in claim 21, further comprising a sensor set, coupled to the controller and attachable to the patient to make the hemoglobin oxygen saturation measurements and to measure a first pulsatile characteristic proximate the measurement site, thereby producing the first pulsatile input signal.

23. An apparatus as recited in claim 21, wherein the controller triggers a signal at the first output at a predetermined time relative to the pulsatile input signal.

24. An apparatus as recited in claim 21, wherein the controller selects data obtained from the second input in response to the pulsatile input signal.

25. An apparatus as recited in claim 21, wherein the controller further includes a laser Doppler velocimetry (LDV) unit and the first input receives LDV data from the patient.

26. An apparatus as recited in claim 25, wherein the controller LDV unit includes a light source for generating light used in generating the LDV data received from the patient.

27. An apparatus as recited in claim 21, wherein the controller further includes an impedance measuring unit and the first input receives impedance measurement data from the patient.

28. An apparatus as recited in claim 27, wherein the controller further includes a second output from the impedance measuring unit to carry signals for generating impedance measurements.

29. An apparatus as recited in claim 21, wherein the controller further includes a pulse-oximeter module coupled to the first output and the second input.

30. An apparatus as recited in claim 29, wherein the pulse-oximeter unit receives optical absorption data from the measurement site at a time of substantially maximum absorption and at a time of substantially minimum absorption.

31. An apparatus as recited in claim 30, wherein the times of maximum absorption and minimum absorption correspond to predetermined times relative to a feature of the pulsatile input signal.

32. An apparatus as recited in claim 21, further comprising a sensor head coupled to the controller and couplable to the patient for taking measurements of hemoglobin oxygen saturation.

33. An apparatus as recited in claim 32, wherein the sensor head also includes at least one optical port for transmitting an LDV probe signal to the patient and receiving an LDV return signal from the patient.

34. An apparatus as recited in claim 32, wherein the sensor head delivers light to the patient at first and second wavelengths for making measurements of hemoglobin oxygen saturation, the first wavelength being different from the second wavelength.

35. An apparatus as recited in claim 34, wherein the sensor head delivers light to the patient at a third wavelength for making an LDV measurement on the patient.

36. An apparatus as recited in claim 34, wherein the sensor head delivers light to the patient at one of the first and second wavelengths for making an LDV measurement on the patient.

37. An apparatus as recited in claim 21, further comprising a third input to receive motion detection information of the patient, the processor that i) controls making the hemoglobin oxygen saturation measurements or ii) analyzes the received signals in response to the motion detection information.

38. An apparatus as recited in claim 37, further comprising a motion detector coupled to the third input.

39. An apparatus as recited in claim 21, further comprising a fourth input to receive a second pulsatile input signal based on a second pulsatile characteristic, the processor i) controlling making the hemoglobin oxygen saturation measurements or ii) analyzing the received signals in response to the detected second pulsatile characteristic.

40. An apparatus as recited in claim 21, wherein the controller further includes a data output to output data related to the first pulsatile characteristic.

41. An apparatus as recited in claim 21, wherein the controller further includes a display to display data related to the first pulsatile characteristic.

42. A sensor unit for making measurements of hemoglobin oxygen saturation on a patient, comprising:

a body attachable to the patient, the body having one or more optical ports for delivering light to the patient at at least first and second wavelengths for measuring hemoglobin oxygen saturation; and

at least a portion of a detector mounted on the body to measure a pulsatile characteristic of the patient.

43. A sensor unit as recited in claim 42, wherein the body includes first and second optical ports to deliver light to the patient at respective first and second optical wavelengths when the patient interface is attached to the patient.

44. A sensor unit as recited in claim 42, wherein the body includes at least first and second light sources operating respectively at at least first and second wavelengths to direct light into the patient when the patient interface is mounted to the patient, and also includes an optical detector to detect light received, via the patient, from the at least first and second light sources.

45. A sensor unit as recited in claim 42, wherein the at least a portion of the detector includes an optical port for receiving an optical laser Doppler velocimetry (LDV) signal from the patient.

46. A sensor unit as recited in claim 45, wherein the optical port includes an optical fiber.

47. A sensor unit as recited in claim 42, wherein the at least a portion of the detector includes electrodes mounted with a surface of the housing to contact the patient when the interface is mounted to the patient.

48. A sensor unit as recited in claim 42, further comprising a motion sensor attached to the body.

49. A method of determining hemoglobin oxygen saturation at a measurement site on a patient, comprising:

measuring a first pulsatile characteristic arising from contraction of the patient'"'"'s heart;

illuminating the measurement site with light at at least two different wavelengths;

detecting the light at the at least two different wavelengths at the measurement site to produce detection signals; and

analyzing the detection signals to determine hemoglobin oxygen saturation levels at the measurement site;

wherein at least one of i) illuminating the measurement site and ii) analyzing the detected light is performed in response to the measured first pulsatile characteristic.

50. A method as recited in claim 49, wherein illuminating the measurement site includes triggering the one or more light sources at a predetermined time relative to the first pulsatile characteristic.

51. A method as recited in claim 49, wherein analyzing the detected light includes selecting hemoglobin oxygen saturation measurement data in response to the first pulsatile characteristic.

52. A method as recited in claim 49, further comprising measuring a second pulsatile characteristic of the patient and wherein at least one of i) illuminating the measurement site and ii) analyzing the detected light is performed in response to the measured second pulsatile characteristic.

53. A method as recited in claim 52, wherein the second pulsatile characteristic is a pulsatile characteristic arising from contraction of the heart.

54. A method as recited in claim 52, wherein the second pulsatile characteristic is an electroencephalographic (ECG) signal.

55. A method as recited in claim 49, wherein detecting the light includes measuring light absorption at a time of substantially maximum optical blood absorption and measuring light absorption at a time of substantially minimum optical blood absorption.

56. A method as recited in claim 55, wherein the times of maximum absorption and minimum absorption correspond to predetermined times relative to a feature of the blood flow characteristic.

57. A method as recited in claim 49, further comprising detecting motion of at least part of the patient to product motion detection signals, and wherein analyzing the detection signals includes analyzing the detection signals in response to the motion detection signals.

58. A method as recited in claim 49, wherein measuring the first pulsatile characteristic includes measuring blood flow velocity.

59. A method as recited in claim 49, wherein measuring the first pulsatile characteristic includes measuring impedance.

60. A method as recited in claim 49, wherein measuring the first pulsatile characteristic includes measuring blood pressure.

61. A method as recited in claim 49, wherein measuring the first pulsatile characteristic includes measuring an acoustic signal generated resulting from contraction of the heart.

62. A method as recited in claim 49, further comprising detecting motion of at least part of the patient and wherein analyzing the detection signals includes analyzing the detection signals includes selecting detection signals based on whether the detection signals were obtained during a period of patient motion.

63. A method as recited in claim 49, further comprising outputting results related to the first pulsatile characteristic arising from contraction of the patient'"'"'s heart.

65. A system for determining hemoglobin oxygen saturation at a measurement site on a patient, comprising:

means for measuring a first pulsatile characteristic arising from contraction of the patient'"'"'s heart;

means for illuminating the measurement site with light at two different wavelengths;

means for detecting the light at the two different wavelengths at the measurement site to produce detection signals; and

means for analyzing the detection signals to determine hemoglobin oxygen saturation levels at the measurement site;

wherein at least one of i) the means for illuminating the measurement site and ii) the means for analyzing the detected light performs in response to the measured first pulsatile characteristic.

66. A system for measuring oxygen saturation of hemoglobin at a measurement site on a patient, comprising:

a controller having a first input to receive a first pulsatile measurement signal indicative of a first pulsatile characteristic resulting from contraction of the patient'"'"'s heart from the patient, a first output to control making hemoglobin oxygen saturation measurements and a second input to receive signals related to the measurements of oxygen saturation of hemoglobin made at the measurement site, and having a processor that at least one of i) controls making the hemoglobin oxygen saturation measurements or ii) analyzes the received signals in response to the received first pulsatile measurement signal.

67. A system as recited in claim 66, wherein the first pulsatile characteristic is blood flow velocity.

68. A system as recited in claim 67, wherein the controller includes a laser Doppler velocimetry (LDV) module, having an output for directing an LDV optical probe signal at the patient and being coupled to receive the first pulsatile measurement signal.

69. A system as recited in claim 66, wherein the first pulsatile characteristic is impedance.

70. A system as recited in claim 67, wherein the controller includes an impedance module, having an output for directing a probe current to the patient and being coupled to receive the first pulsatile measurement signal.

71. A system as recited in claim 66, wherein the first pulsatile characteristic is an acoustic signal related to contraction of the heart.

72. A system as recited in claim 71, wherein the controller includes an acoustic signal module coupled to receive the first pulsatile measurement signal.

73. A system as recited in claim 66, wherein the first pulsatile characteristic is blood pressure.

74. A system as recited in claim 73, wherein the controller includes an blood pressure measuring module coupled to receive the first pulsatile measurement signal.

75. A system as recited in claim 66, wherein the controller triggers a signal at the first output at a predetermined time relative to the first pulsatile measurement signal.

76. A system as recited in claim 66, wherein the controller selects data obtained from the second input in response to the first pulsatile measurement signal.

77. A system as recited in claim 66, wherein the controller further includes a third input to receive a second pulsatile measurement signal from the patient related to a second pulsatile characteristic of the patient.

78. A system as recited in claim 77, wherein the second pulsatile characteristic is a pulsatile characteristic resulting from contraction of the patient'"'"'s heart.

79. A system as recited in claim 77, wherein the second pulsatile characteristic is an electroencephalographic (ECG) signal.

80. A system as recited in claim 66, wherein the controller further includes a pulse-oximeter unit coupled to the first output and the second input.

81. A system as recited in claim 80, wherein the pulse-oximeter unit receives optical absorption data from the measurement site at a time of substantially maximum absorption and at a time of substantially minimum absorption.

82. A system as recited in claim 81, wherein the times of maximum absorption and minimum absorption correspond to predetermined times relative to a feature of the first pulsatile measurement signal.

83. A system as recited in claim 66, further comprising a sensor head coupled to the controller and attachable to the patient for taking measurements of hemoglobin oxygen saturation.

84. A system as recited in claim 83, wherein the sensor head also includes at least part of a sensor for detecting the first pulsatile characteristic.

85. A system as recited in claim 84, wherein the sensor head delivers light to the patient at first and second wavelengths for making measurements of hemoglobin oxygen saturation, the first wavelength being different from the second wavelength.

86. A system as recited in claim 84, wherein the sensor head delivers light to the patient at a third wavelength for making an LDV measurement on the patient.

87. A system as recited in claim 84, wherein the sensor head delivers light to the patient at one of the first and second wavelengths for making an LDV measurement on the patient.

88. A system as recited in claim 84, wherein the sensor head includes an impedance sensor for measuring impedance of the patient.

89. A system as recited in claim 84, wherein the sensor head includes a pressure monitor for measuring blood pressure of the patient.

90. A system as recited in claim 84, wherein the sensor head includes an acoustic sensor for measuring an acoustic signal related to contraction of the patient'"'"'s heart.

91. A system as recited in claim 66, wherein the controller further includes a fourth input to receive patient motion information.

92. A system as recited in claim 91, wherein the controller further analyzes the received signals in response to the patient motion information received via the fourth input.

93. A system as recited in claim 91, further comprising a motion detector coupled to the fourth input, the motion detector being attachable to the patient.

94. A system as recited in claim 93, further comprising a sensor unit attachable to the patient for receiving at least one of a) the first pulsatile measurement signal from the patient and b) optical blood absorption data, the motion sensor being integrated to the sensor unit.

95. A system as recited in claim 66, wherein the controller further includes a data output to output data related to the first pulsatile characteristic resulting from contraction of the patient'"'"'s heart.

96. An apparatus as recited in claim 66, wherein the controller further includes a display to display data related to the first pulsatile characteristic resulting from contraction of the patient'"'"'s heart.