Non-invasive blood pressure monitoring device and methods

• US 20050148885A1
• Filed: 08/20/2004
• Published: 07/07/2005
• Est. Priority Date: 08/22/2003
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: EPPCOR, INC.
• Inventors: Epstein, Paul, Tweed, David, Phillipps, Patrick G.
• Granted Patent: US 7,601,123 B2
• Time in Patent Office: Days
• US Class Current: 600/490
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 5/0048 Detecting, measuring or recording by applying mechanical forces or stimuli A61B5/021, A61B5/4884 and A61B9/00 take precedence
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/02241 of small dimensions, e.g. adapted to fingers
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance
• 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

Abstract

The apparatus and methods of the present invention provide a non-invasive measurement of blood pressure with a frequency that approximates a continuous measurement. Blood pressure measurement provides information that is both clinically and diagnostically significant. In accordance with an aspect of the present invention, a method for providing a non-invasive measurement of blood pressure, includes obtaining a first input signal and a second input signal indicative of occlusive measurements of systolic blood pressure and diastolic blood pressure, respectively; tracking a signal indicative of pulse pressure; continuously measuring a third signal indicative of mean blood pressure; and processing the signals to obtain a measurement indicative of systolic and diastolic blood pressure, wherein at least a portion of the measurement indicative of systolic and diastolic blood pressure is continuous. The second input signal indicative of diastolic blood pressure is analyzed to identify a maximum amplitude of the signal, the maximum amplitude being indicative of the diastolic blood pressure measurement.

Claims

1. A method for providing a non-invasive measurement of blood pressure, the method comprising the steps of:

obtaining a first input signal and a second input signal indicative of occlusive measurements of systolic blood pressure and diastolic blood pressure, respectively;

tracking a signal indicative of pulse pressure;

continuously measuring a third signal indicative of mean blood pressure; and

processing said signals to obtain a measurement indicative of systolic and diastolic blood pressure, wherein at least a portion of the measurement indicative of systolic and diastolic blood pressure is continuous.

2. The method of claim 1, wherein obtaining the second input signal indicative of diastolic blood pressure comprises analyzing the second input signal to identify a maximum amplitude of the signal, the maximum amplitude being indicative of the diastolic blood pressure measurement.

3. The method of claim 1, wherein the first input signal and the second input signal are obtained from a photo-plethysmograph.

4. The method of claim 3, wherein the photo-plethysmograph comprises a light source and a detector.

5. The method of claim 4, wherein the light source is a light emitting diode, a laser or an incandescent lamp.

6. The method of claim 4, wherein the detector is one of a photocell or a photo-resistive device.

7. The method of claim 1, wherein tracking a signal indicative of pulse pressure, pulse pressure characterized as the difference between a systolic pressure measurement and a diastolic pressure measurement, further comprises:

inducing a pulse signal into a region of interest, and

obtaining a resultant signal indicative of a combination of the induced pulse signal and a heart pulse signal.

8. The method of claim 7, wherein processing the resultant signal further comprises amplifying the resultant signal, separating the induced pulse signal from the heart pulse signal and calculating the pulse pressure from the relative amplitudes of the induced pulse signal and the heart pulse signal.

9. The method of claim 7, further comprising minimizing a venous response to the induced pulse signal.

10. The method of claim 9, wherein minimizing the venous response comprises at least one of selecting an appropriate frequency for the induced pulse signal and/or applying a constant pressure to the region of interest.

11. The method of claim 1, wherein the step of continuously measuring mean blood pressure further comprises continuously monitoring a voltage signal of a photo-plethysmograph and an amplitude signal of an induced pulse signal.

12. The method of claim 11, wherein the amplitude of the induced pulse signal is proportional to a compliance characteristic of an arterial vasculature.

13. The method of claim 11, further comprising:

calculating a function of the voltage signal and the amplitude signal, wherein the function is proportional to the mean blood pressure.

14. The method of claim 13, wherein the function is a geometric mean of the voltage signal and the amplitude signal.

15. The method of claim 13, further comprising determining a continuous measurement indicative of systolic blood pressure from the relationship defined by mean blood pressure added to a fraction of the pulse pressure.

16. The method of claim 15, wherein the fraction of the pulse pressure is two-thirds.

17. The method of claim 13, further comprising determining a continuous measurement indicative of diastolic blood pressure from the relationship governed by a fraction of the pulse pressure subtracted from mean blood pressure.

18. The method of claim 17, wherein the fraction of pulse pressure is one-third.

19. The method of claim 1, further comprising performing a plurality of processing cycles upon obtaining a new first input signal and new second input signal.

20. A method for monitoring a continuous blood pressure measurement of a subject such as a critical care patient, the method comprising the steps of:

calibrating a signal indicative of a mean pressure tracking parameter;

measuring continuously and tracking a signal indicative of pulse pressure;

calculating a continuous measurement indicative of mean blood pressure; and

processing at least the continuous measurement indicative of mean blood pressure to obtain measurements indicative of continuous systolic blood pressure and continuous diastolic blood pressure.

21. The method of claim 20, further comprising obtaining a plurality of occlusive measurements indicative of blood pressure.

22. The method of claim 21, wherein obtaining a plurality of occlusive measurements includes obtaining a first input signal indicative of a systolic blood pressure and second input signal indicative of diastolic blood pressure, and wherein the second input signal indicative of diastolic blood pressure comprises analyzing the second input signal to identify a maximum amplitude of the second input signal, the maximum amplitude being indicative of the diastolic blood pressure measurement.

23. The method of claim 22, wherein the first input signal and the second input signal are obtained from a photo-plethysmograph.

24. The method of claim 23, wherein the photo-plethysmograph comprises a light source and a detector.

25. The method of claim 24, wherein the light source is a light emitting diode, a laser or an incandescent lamp.

26. The method of claim 24, wherein the detector is one of a photocell or a photo-resistive device.

27. The method of claim 20, wherein tracking a signal indicative of pulse pressure which is characterized as the difference between a systolic pressure measurement and a diastolic pressure measurement further comprises inducing a pulse signal into a region of interest, and obtaining a resultant signal indicative of a combination of the induced pulse signal and a heart pulse signal.

28. The method of claim 27, wherein processing the resultant signal further comprises amplifying the resultant signal, separating the induced pulse signal from the heart pulse signal and calculating the pulse pressure from the relative amplitudes of the induced pulse signal and the heart pulse signal.

29. The method of claim 27, further comprising minimizing a venous response to the induced pulse signal.

30. The method of claim 29, wherein minimizing the venous response comprises at least one of selecting an appropriate frequency for the induced pulse signal and/or applying a constant pressure to the region of interest.

31. The method of claim 20, wherein the step of continuously measuring mean blood pressure further comprises continuously monitoring a voltage signal of a photo-plethysmograph and an amplitude signal of an induced pulse signal.

32. The method of claim 31, wherein the amplitude of the induced pulse signal is proportional to a compliance characteristic of an arterial vasculature.

33. The method of claim 31, further comprising:

calculating a geometric mean of the voltage signal and the amplitude signal, wherein the geometric mean is proportional to the mean blood pressure.

34. The method of claim 33, further comprising:

determining a continuous measurement indicative of systolic blood pressure from the relationship defined by mean blood pressure added to a fraction of the pulse pressure.

35. The method of claim 34, wherein the fraction is two-thirds.

36. The method of claim 33, further comprising determining a continuous measurement indicative of diastolic blood pressure from the relationship governed by a fraction of the pulse pressure subtracted from mean blood pressure.

37. The method of claim 36, wherein the fraction is one-third.

38. The method of claim 22, further comprising performing a plurality of processing cycles upon obtaining a new first input signal and new second input signal.

39. A system for providing a continuous, non-invasive measurement of blood pressure, comprising:

a sensor module to obtain a plurality of physiological signals indicative of blood pressure; and

a control module in communication with the sensor module for data collection and processing, the control module having a processor to process the plurality of physiological signals to provide a continuous measurement indicative of blood pressure.

40. The system of claim 39, wherein the sensor module comprises:

a housing defining a compartment closed at a distal end and open at a proximal end for receiving a body part into the proximal end;

a first membrane defining a first chamber containing a pressurized fluid to apply a static pressure field to the body part when received within the housing;

a second membrane defining a second chamber; and

at least one sensor in at least one of said first and second chamber for sensing changes in the body part.

41. The system of claim 40, wherein the at least one sensor is a pressure sensor for sensing the pressure of a region of interest of the body part.

42. The system of claim 40, wherein the at least one sensor is a photo-plethysmograph.

43. The system of claim 40, wherein the at least one sensor comprises a light source and an optical detector.

44. The system of claim 43, wherein the light source is one of a light emitting diode, a laser or an incandescent lamp.

45. The system of claim 43, wherein the optical detector is one of a photocell or a photo-resistive device.

46. The system of claim 43, wherein the sensor is located on an integrated circuit board.

47. The system of claim 39, wherein the processor in the control module further comprises at least one of analog processing circuitry and digital processing circuitry.

48. The system of claim 47, wherein the analog processing circuitry provides at least one of a signal indicative of an induced pulse signal, a heart pulse signal, DC photocell signal, induced drive signal to an AC pressure pump, pressure signal to an analog to digital converter and a drive signal to a light source.

49. The system of claim 47, wherein the digital processing circuitry provides at least one of signal to a filter clock, graphics display, user interface, a pump, a plurality of valves and a power amplifier.

50. The system of claim 39, wherein the control module comprises an integral display unit for displaying the plurality of physiological signals indicative of blood pressure.

51. The system of claim 50, wherein the plurality of physiological signals comprises at least one of pulse pressure, mean blood pressure, pulse waveform, alarm limits, diastolic blood pressure for a period of time and systolic blood pressure for a period of time.

52. The system of claim 39, wherein the control module further comprising a plurality of user interfaces to select different parameters such as time and alarm limits.

53. A portable apparatus for monitoring non-invasively, blood pressure measurements of a patient, comprising:

a housing defining a compartment closed at one end and open at an opposite end for receiving a distal part of a body part, the housing having at least one sensor for measuring a signal indicative of blood pressure;

a pump to pressurize at least one chamber in said housing; and

a processing device in communication with the housing and pump to process the at least one signal to provide at least one signal indicative of blood pressure, wherein at least a portion of said signal is provided continuously.

54. The portable apparatus of claim 53, wherein the housing comprises:

a first membrane defining a first chamber containing a pressurized fluid to apply a static pressure field to the body part when received within the housing;

a second membrane defining a second chamber; and

at least one sensor in at least one of said first and second chamber for sensing changes in the body part.

55. The portable apparatus of claim 53, wherein the at least one sensor is a pressure sensor for sensing the pressure of a region of interest of the body part.

56. The portable apparatus of claim 54, wherein the at least one sensor is a photo-plethysmograph.

57. The portable apparatus of claim 54, wherein the at least one sensor comprises a light source and an optical detector.

58. The portable apparatus of claim 57, wherein the light source is one of a light emitting diode, a laser or an incandescent lamp.

59. The portable apparatus of claim 57, wherein the optical detector is one of a photocell or a photo-resistive device.

60. The portable apparatus of claim 57, wherein the sensor is located on an integrated circuit board.

61. The portable apparatus of claim 53, wherein the processing device further comprises at least one of analog processing circuitry and digital processing circuitry.

62. The portable apparatus of claim 53, wherein the processing device comprises an integral display unit for displaying the plurality of physiological signals indicative of blood pressure.

63. The portable apparatus of claim 62, wherein the plurality of physiological signals comprises at least one of pulse pressure, mean blood pressure, pulse waveform, alarm limits, diastolic blood pressure for a period of time and systolic blood pressure for a period of time.

64. The portable apparatus of claim 53, wherein the processing device further comprising a plurality of user interfaces to select different parameters such as time and alarm limits.

65. The portable apparatus of claim 53, wherein the apparatus weighs approximately 11 pounds.

66. The method for providing a non-invasive measurement of blood pressure, the method comprising:

obtaining an input signal indicative of blood pressure from an occlusive measurement; and

analyzing the input signal to identify a maximum amplitude of the signal, the maximum amplitude being indicative of the diastolic blood pressure measurement.

67. The method of claim 66, further comprising:

obtaining a second input signal indicative of occlusive measurements of systolic blood pressure;

tracking a signal indicative of pulse pressure;

continuously measuring a third signal indicative of mean blood pressure; and

processing said signals to obtain a measurement indicative of systolic and diastolic blood pressure, wherein at least a portion of the measurement indicative of systolic and diastolic blood pressure is continuous.

68. The method of claim 67, wherein the input signal and the second input signal are obtained from a photo-plethysmograph.

69. The method of claim 68, wherein the photo-plethysmograph comprises a light source and a detector.

70. The method of claim 69, wherein the light source is a light emitting diode, a laser or an incandescent lamp.

71. The method of claim 69, wherein the detector is a photocell or a photo-resistive device.

72. The method of providing a continuous, non-invasive measurement of blood pressure, the method comprising:

tracking a signal indicative of pulse pressure, pulse pressure characterized as the difference between a systolic pressure measurement and a diastolic pressure measurement, comprising;

inducing a pulse signal into a region of interest, and

obtaining a resultant signal indicative of a combination of the induced pulse signal and a heart pulse signal.

73. The method of claim 72, wherein processing the resultant signal further comprises amplifying the resultant signal, separating the induced pulse signal from the heart pulse signal and calculating the pulse pressure from the relative amplitudes of the induced pulse signal and the heart pulse signal.

74. The method of claim 72, further comprising minimizing a venous response to the induced pulse signal.

75. The method of claim 74, wherein minimizing the venous response comprises at least one of selecting an appropriate frequency for the induced pulse signal and/or applying a constant pressure to the region of interest.

76. The method of claim 72, further comprising:

obtaining a first input signal and a second input signal indicative of occlusive measurements of systolic blood pressure and diastolic blood pressure, respectively;

continuously measuring a third signal indicative of mean blood pressure; and

processing said signals to obtain a continuous measurement indicative of systolic and diastolic blood pressure.

77. The method for non-invasively monitoring blood pressure comprising:

continuously measuring mean blood pressure by continuously monitoring a voltage signal of a photo-plethysmograph and an amplitude signal of an induced pulse signal.

78. The method of claim 77, wherein the amplitude of the induced pulse signal is proportional to a compliance characteristic of an arterial vasculature.

79. The method of claim 77, further comprising:

calculating a function of the voltage signal and the amplitude signal, wherein the function is proportional to the mean blood pressure.

80. The method of claim 79, wherein the function is a geometric mean of the voltage signal and the amplitude signal.

81. The method of claim 80, further comprising determining a continuous measurement indicative of systolic blood pressure from the relationship defined by mean blood pressure added to a fraction of pulse pressure.

82. The method of claim 81, whereby the fraction of pulse pressure is two-thirds.

83. The method of claim 79, further comprising determining a continuous measurement indicative of diastolic blood pressure from the relationship governed by a fraction of pulse pressure subtracted from mean blood pressure.

84. The method of claim 83, whereby the fraction is one-third.

85. The method of claim 77, further comprising the steps of:

obtaining a plurality of occlusive measurements indicative of blood pressure;

calibrating a signal indicative of a mean pressure tracking parameter; and

measuring continuously and tracking a signal indicative of pulse pressure.

86. A sensor module for providing measurements indicative of blood pressure, comprising:

operating in a first mode for providing occlusive measurements indicative of diastolic blood pressure and systolic blood pressure; and

operating in a second mode for continuously providing signals indicative of blood pressure.

87. The sensor module of claim 86 further comprising a control module in communication with the sensor module for data collection and processing.

88. The sensor module of claim 86, wherein the occlusive measurements further comprises:

obtaining a first input signal indicative of diastolic blood pressure comprises analyzing the input signal to identify a maximum amplitude of the signal, the maximum amplitude being indicative of the diastolic blood pressure measurement.

89. The sensor module of claim 86, wherein the occlusive measurement comprises obtaining a first input signal and a second input signal from a photo-plethysmograph.

90. The sensor module of claim 89, wherein the photo-plethysmograph comprises a light source and a detector.

91. The sensor module of claim 90, wherein the light source is a light emitting diode, a laser or an incandescent lamp.

92. The sensor module of claim 90, wherein the detector is one of a photocell or a photo-resistive device.

93. The sensor module of claim 86, wherein operating in the first mode comprises tracking a signal indicative of pulse pressure, pulse pressure characterized as the difference between a systolic pressure measurement and a diastolic pressure measurement, further comprises:

inducing a pulse signal into a region of interest, and obtaining a resultant signal indicative of a combination of the induced pulse signal and a heart pulse signal.

94. The sensor module of claim 93, wherein processing the resultant signal further comprises amplifying the resultant signal, separating the induced pulse signal from the heart pulse signal and calculating the pulse pressure from the relative amplitudes of the induced pulse signal and the heart pulse signal.

95. The sensor module of claim 93, further comprising minimizing a venous response to the induced pulse signal.

96. The sensor module of claim 95, wherein minimizing the venous response comprises at least one of selecting an appropriate frequency for the induced pulse signal and/or applying a constant pressure to the region of interest.

97. The sensor module of claim 86, wherein operating in the second mode further comprises continuously measuring mean blood pressure by continuously monitoring a voltage signal of a photo-plethysmograph and an amplitude signal of an induced pulse signal.

98. The sensor module of claim 94, wherein the amplitude of the induced pulse signal is proportional to a compliance characteristic of an arterial vasculature.

99. The sensor module of claim 94, further comprising:

calculating a function of the voltage signal and the amplitude signal, wherein the function is proportional to the mean blood pressure.

100. The sensor module of claim 99, wherein the function is a geometric mean of the voltage signal and the amplitude signal.