Method and system for determining cardiac function

• US 20080183232A1
• Filed: 01/30/2007
• Published: 07/31/2008
• Est. Priority Date: 01/30/2007
• Status: Abandoned Application

• Current Assignee: Woolsthorpe, LLC
• Original Assignee: Woolsthorpe, LLC
• Inventors: Voss, Gregory I., Mills, Alexander K., Sterling, Bernhard B., Wall, Donna, Bergman, Anthony J.
• Application Number:
  US11/700,328
• Publication Number:
  US 20080183232A1
• Time in Patent Office: Days
• US Class Current: 607/24
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• 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 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

A method for determining a physiologic characteristic associated with cardiac function in a subject comprising the steps of providing at least one electromagnetic radiation absorption measurement, providing demographic information reflecting the subject'"'"'s physical condition, determining a temporal plethysmographic value from the electromagnetic radiation absorption measurement, and determining at least one physiologic characteristic from the temporal plethysmographic value and demographic information by using a predetermined phenomenological model that is adapted to provide an estimate of a blood volume-time relationship proximate the heart and compute at least one physiologic characteristic associated with cardiac function based on the estimated blood volume-time relationship.

Claims

1. A method of determining a physiologic characteristic associated with cardiac function in a subject, comprising the steps of:

providing at least one non-invasive measurement representing a physiological parameter of the subject, said non-invasive measurement comprising electromagnetic radiation absorption;

determining at least one temporal plethysmographic value from said electromagnetic radiation absorption;

providing demographic information, said demographic information including information reflecting the subject'"'"'s physical condition; and

determining at least one physiologic characteristic from said temporal plethysmographic value and demographic information by using a predetermined phenomenological model, said model being adapted to provide an estimate of a blood volume-time relationship proximate the heart from non-pressure related measurements and compute at least one physiologic characteristic associated with cardiac function based on said estimated blood volume-time relationship.

2. The method of claim 1, wherein said subject'"'"'s physical condition information is selected from the group consisting of the subject'"'"'s weight, height, age, gender and body mass index.

3. The method of claim 1, wherein said subject'"'"'s physical condition information is selected from the group consisting of a disease condition, disease diagnosis and therapy for a disease.

4. The method of claim 1, wherein said physiologic characteristic is selected from the group consisting of heart rate, pulse transit time, wave velocity, central blood flow, peripheral blood flow, perfusion, contractility and vasoconstriction.

5. The method of claim 1, wherein said cardiac function is selected from the group consisting of stroke volume, cardiac output and cardiac index.

6. The method of claim 4, wherein said blood flow is determined by calculating for blood pressure (p(t)) according to the formula

p(t)=f(t)*z(t),

wherein p(t) represents pressure, f(t) represents volumetric flow, and z(t) represents impedance to flow at time t, and calculating for arterial volumetric flow at the aorta according to the formula

p_a(t)−

p_v(t)=f(t)*z(t),

wherein p_a(t) represents arterial pressure, p_v(t) represents central venous pressure, and z(t) represents arterial impedance at time t, and calculating for volumetric flow according to the formula

7. The method of claim 5, wherein said stroke volume (SV) is calculated according to the formula

8. The method of claim 7, wherein said p_v(t) is approximated as the arterial pressure at the end of diastole.

9. The method of claim 1, wherein said electromagnetic radiation absorption is measured on at least one location on the subject'"'"'s body selected from an arm, hand, finger, ear canal, ear lobe, foot, toe, nare, tongue, back, neck and forehead.

10. The method of claim 1, wherein said electromagnetic radiation absorption is measured on multiple locations on the subject'"'"'s body selected from an arm, hand, finger, ear canal, ear lobe, foot, toe, nare, tongue, back, neck and forehead.

11. The method of claim 1, wherein said electromagnetic radiation absorption is measured on at least one location on the subject'"'"'s body selected from the group consisting of the neck and forehead.

12. The method of claim 1, wherein said physiologic characteristic is visually displayed on a display medium.

13. A method of determining a physiologic characteristic associated with cardiac function in a subject, comprising the steps of:

providing at least first and second non-invasive measurements representing physiological parameters of the subject, said first non-invasive measurement comprising an electrical measurement of the heart, said second non-invasive measurement comprising electromagnetic radiation absorption;

determining at least one temporal relationship from said electrical measurement of the heart;

determining at least one temporal plethysmographic value from said electromagnetic radiation absorption;

providing demographic information, said demographic information including information reflecting the subject'"'"'s physical condition; and

determining at least one physiologic characteristic from said temporal relationship, temporal plethysmographic value and demographic information by using a predetermined phenomenological model, said model being adapted to provide an estimate a blood volume-time relationship proximate the heart from non-pressure related measurements and compute at least one physiologic characteristic associated with cardiac function based on said estimated blood volume-time relationship.

14. The method of claim 13, wherein said subject'"'"'s physical condition information is selected from the group consisting of the subject'"'"'s weight, height, age, gender and body mass index.

15. The method of claim 13, wherein said subject'"'"'s physical condition information is selected from the group consisting of a disease condition, disease diagnosis and therapy for a disease.

16. The method of claim 13, wherein said physiologic characteristic is selected from the group consisting of heart rate, pulse transit time, wave velocity, central blood flow, peripheral blood flow, perfusion, contractility and vasoconstriction.

17. The method of claim 13, wherein said cardiac function is selected from the group consisting of stroke volume, cardiac output and cardiac index.

18. The method of claim 16, wherein said central blood flow is determined by calculating for blood pressure (p(t)) according to the formula

p(t)=f(t)*z(t),

wherein p(t) represents pressure, f(t) represents volumetric flow, and z(t) represents impedance to flow at time t, and calculating for arterial volumetric flow at the aorta according to the formula

p_a(t)−

p_v(t)=f(t)*z(t),

wherein p_a(t) represents arterial pressure, p_v(t) represents central venous pressure, and z(t) represents arterial impedance at time t, and calculating for volumetric flow according to the formula

19. The method of claim 17, wherein said stroke volume (SV) is calculated according to the formula

20. The method of claim 19, wherein said p_v(t) is approximated as the arterial pressure at the end of diastole.

21. The method of claim 13, wherein said electrical measurement of the heart comprises electrical potential of the heart.

22. The method of claim 21, wherein said electrical potential of the heart is measured by an electrocardiogram.

23. The method of claim 13, wherein said electromagnetic radiation absorption is measured on at least one location on the subject'"'"'s body selected from an arm, hand, finger, ear canal, ear lobe, foot, toe, nare, tongue, back, neck and forehead.

24. The method of claim 13, wherein said electromagnetic radiation absorption is measured on multiple locations on the subject'"'"'s body selected from an arm, hand, finger, ear canal, ear lobe, foot, toe, nare, tongue, back, neck and forehead.

25. The method of claim 13, wherein said electromagnetic radiation absorption is measured on at least one location on the subject'"'"'s body selected from the group consisting of the neck and forehead.

26. The method of claim 13, wherein said first and second non-invasive measurements comprise time varying measurements.

27. The method of claim 13, wherein said physiologic characteristic is visually displayed on a display medium.

31. The method of claim 19, wherein said plurality of temporal plethysmographic values is scaled according to at least one of said physiological parameters.

28. A method of determining a physiologic characteristic associated with cardiac function in a subject, comprising the steps of:

providing at least one non-invasive measurement representing a physiological parameter of the subject, said non-invasive measurement comprising electromagnetic radiation absorption;

determining at least one temporal plethysmographic value from said electromagnetic radiation absorption;

performing non-linear scaling of said temporal plethysmographic value according to a physiological parameter selected from the group consisting of minimum blood pressure, maximum blood pressure and a predetermined blood pressure, said predetermined blood pressure being greater than said minimum blood pressure and less then said maximum blood pressure; and

determining a time-varied blood pressure from said scaled temporal plethysmographic value.

29. The method of claim 28, wherein a plurality of electromagnetic radiation absorption measurements are provided.

30. The method of claim 29, wherein a plurality of temporal plethysmographic values is determined from said plurality of electromagnetic radiation absorption measurements.

32. A method of determining a physiologic characteristic associated with cardiac function in a subject, comprising the steps of:

providing at least first and second non-invasive measurements representing physiological parameters of the subject, said first non-invasive measurement comprising an electrical measurement of the heart, said second non-invasive measurement comprising electromagnetic radiation absorption;

providing demographic information, said demographic information including information reflecting the subject'"'"'s physical condition;

determining temporal arterial pressure from said first and second non-invasive measurements and said demographic information;

determining the extent of a pressure pulse from said first and second non-invasive measurements;

determining heart rate from said first and second non-invasive measurements;

determining stroke volume from said temporal arterial pressure, extent of a pressure pulse and demographic information; and

determining cardiac output from said stroke volume and said heart rate.

33. The method of claim 32, wherein said subject'"'"'s physical condition information is selected from the group consisting of the subject'"'"'s weight, height, age, gender and body mass index.

34. The method of claim 32, wherein said subject'"'"'s physical condition information is selected from the group consisting of a disease condition, disease diagnosis and therapy for a disease.

35. The method of claim 32, wherein a plurality of first and second non-invasive measurements are provided.

36. The method of claim 35, including the step of pre-qualifying said first and second non-invasive measurements.

37. The method of claim 36, wherein said pre-qualifying comprises averaging said plurality of said first non-invasive measurements to provide mean first non-invasive measurements.

38. The method of claim 36, wherein said pre-qualifying comprises selecting a third non-invasive measurement from said plurality of second non-invasive measurements, said third non-invasive measurement having a maximum pulsatile amplitude.

39. The method of claim 36, wherein said pre-qualifying comprises filtering of said plurality of first and second non-invasive measurements.

40. The method of claim 32, wherein said step of determining temporal arterial pressure includes the steps of determining QRS onset, determining the onset of systolic upstroke, determining pulse transit time and determining selective blood pressure parameters.

41. The method of claim 40, wherein said step of determining QRS onset provides the time of the onset of the QRS complex.

42. The method of claim 41, wherein said QRS onset time indicator comprises a QRS time index that substantially corresponds to the moment of said onset of the QRS complex.

43. The method of claim 40, wherein said step of determining the onset of systolic upstroke provides the time of the onset of systolic upstroke.

44. The method of claim 43, wherein said systolic upstroke time indicator comprises a systolic upstroke time index that substantially corresponds to the moment of said onset of systolic upstroke.

45. The method of claim 44, wherein said pulse transit time is determined from said QRS and systolic time indices.

46. The method of claim 40, wherein said blood pressure parameters are selected from the group consisting of minimum arterial pressure (P_diastole), mean arterial pressure (P_mean), and maximum arterial pressure (P_systole).

47. The method of claim 46, wherein said mean arterial pressure (P_mean) is determined from said pulse transit time, heart rate and demographic information.

48. The method of claim 47, wherein said minimum arterial pressure (P_diastole) and maximum arterial pressure (P_systole) are determined from said mean arterial pressure (P_mean) and correlations of said pressure pulse.

49. The method of claim 46, wherein said mean arterial pressure (P_mean) is determined from at least one physiologic characteristic, said demographic information and a blood flow model adapted to provide a model of blood flow through the heart and compliant arteries, said physiologic characteristic being selected from the group consisting of heart rate, pulse transit time, wave velocity, central blood flow, peripheral blood flow, perfusion, contractility and vasoconstriction.

50. The method of claim 32, wherein determining the extent of a pressure pulse includes determining portions of an arterial pressure signal that corresponds to systole.

51. The method of claim 32, wherein said step of determining the extent of the pressure pulse includes the steps of determining the dicrotic notch and end of diastole.

52. The method of claim 51, wherein said step of determining the end of diastole provides a time index that corresponds to the end of diastole during said predetermined heart beat.

53. The method of claim 51, wherein said step of determining the dicrotic notch provides a time index that corresponds to the dicrotic notch during a predetermined heart beat.

54. The method of claim 53, wherein said step of determining said dicrotic notch includes the use of an algorithm to determine the change in slope of a signal representing measure of blood flow (V(t)), wherein V(t) comprises the measured volume at time (t) that corresponds to said dicrotic notch.

55. The method of claim 54, wherein said dicrotic notch occurs at a transition from negative acceleration (d²V/dt²<

0) to positive acceleration (d²V/dt²<

0), said transition having a window of time corresponding to peak systole and minimum diastole.

56. The method of claim 55, wherein said algorithm identifies said peak systole and minimum diastole and calculates d²V/dt² for each point within said time window.

57. The method of claim 55, wherein said algorithm further identifies transitions from said negative to positive acceleration.

58. The method of claim 32, wherein said stroke volume (SV) is calculated according to the formula

59. The method of claim 32, wherein said cardiac output is calculated from a formula

60. The method of claim 32, wherein said electrical measurement of the heart comprises electrical potential of the heart.

61. The method of claim 60, wherein said electrical potential of the heart is measured by an electrocardiogram.

62. The method of claim 32, wherein said electromagnetic radiation absorption is measured on at least one location on the subject'"'"'s body selected from an arm, hand, finger, ear canal, ear lobe, foot, toe, nare, tongue, back, neck and forehead.

63. The method of claim 32, wherein said electromagnetic radiation absorption is measured on multiple locations on the subject'"'"'s body selected from an arm, hand, finger, ear canal, ear lobe, foot, toe, nare, tongue, back, neck and forehead.

64. The method of claim 32, wherein said electromagnetic radiation absorption is measured on at least one location on the subject'"'"'s body selected from the neck and forehead.

65. The method of claim 32, wherein said first and second non-invasive measurements comprise time varying measurements.

66. A system for determining a physiologic characteristic associated with cardiac function in a subject, comprising:

interface means adapted to receive at least one non-invasive measurement representing a physiological parameter of the subject, said non-invasive measurement comprising electromagnetic radiation absorption, and demographic information, said demographic information including information reflecting the subject'"'"'s physical condition;

means for determining at least one temporal plethysmographic value from said electromagnetic radiation absorption; and

means for determining at least one physiologic characteristic from said temporal plethysmographic value and demographic information by using a predetermined phenomenological model, said model being adapted to provide an estimate of a blood volume-time relationship proximate the heart and compute at least one physiologic characteristic associated with cardiac function based on said estimated blood volume-time relationship.

67. The method of claim 66, wherein said subject'"'"'s physical condition information is selected from the group consisting of the subject'"'"'s weight, height, age, gender and body mass index.

68. The method of claim 66, wherein said subject'"'"'s physical condition information is selected from the group consisting of a disease condition, disease diagnosis and therapy for a disease.

69. The system of claim 66, wherein said physiologic characteristic is selected from the group consisting of heart rate, pulse transit time, wave velocity, central blood flow, peripheral blood flow, perfusion, contractility and vasoconstriction.

70. The system of claim 66, wherein said cardiac function is selected from the group consisting of stroke volume, cardiac output and cardiac index.

71. A system for determining a physiologic characteristic associated with cardiac function in a subject, comprising:

interface means adapted to receive at least first and second non-invasive measurements representing physiological parameters of the subject, said first non-invasive measurement comprising an electrical measurement of the heart and said second non-invasive measurement comprising electromagnetic radiation absorption, and demographic information, said demographic information including information reflecting the subject'"'"'s physical condition;

means for determining at least one temporal relationship from said electrical measurement of the heart;

means for determining at least one temporal plethysmographic value from said electromagnetic radiation absorption; and

means for determining at least one physiologic characteristic from said temporal relationship, temporal plethysmographic value and demographic information by using a predetermined phenomenological model, said model being adapted to provide an estimate of a blood volume-time relationship proximate the heart and compute at least one physiologic characteristic associated with cardiac function based on said estimated blood volume-time relationship.

72. The method of claim 71, wherein said subject'"'"'s physical condition information is selected from the group consisting of the subject'"'"'s weight, height, age, gender and body mass index.

73. The method of claim 71, wherein said subject'"'"'s physical condition information is selected from the group consisting of a disease condition, disease diagnosis and therapy for a disease.

74. The system of claim 71, wherein said physiologic characteristic is selected from the group consisting of heart rate, pulse transit time, wave velocity, central blood flow, peripheral blood flow, perfusion, contractility and vasoconstriction.

75. The system of claim 71, wherein said cardiac function is selected from the group consisting of stroke volume, cardiac output and cardiac index.

76. A system for determining a physiologic characteristic associated with cardiac function in a subject, comprising:

interface means adapted to receive at least one non-invasive measurement representing a physiological parameter of the subject, said non-invasive measurement comprising electromagnetic radiation absorption;

means for determining at least one temporal plethysmographic value from said electromagnetic radiation absorption;

means for performing non-linear scaling of said temporal plethysmographic value according to a physiological parameter selected from the group consisting of minimum blood pressure, maximum blood pressure and a predetermined blood pressure, said predetermined blood pressure being greater than said minimum blood pressure and less than said maximum blood pressure; and

means for determining a time-varied blood pressure from said scaled temporal plethysmographic value.

77. The system of claim 76, wherein a plurality of said electromagnetic radiation absorption measurements are provided.

78. The method of claim 77, wherein a plurality of temporal plethysmographic values is determined from said plurality of electromagnetic radiation absorption measurements.

79. The method of claim 78, wherein said plurality of temporal plethysmographic values is scaled according to at least one of said physiological parameters.

80. A system for determining a physiologic characteristic associated with cardiac function in a subject, comprising:

interface means adapted to receive at least first and second non-invasive measurements representing physiological parameters of the subject, said first non-invasive measurement comprising an electrical measurement of the heart and said second non-invasive measurement comprising electromagnetic radiation absorption, and demographic information, said demographic information including information reflecting the subject'"'"'s physical condition;

means for determining at least one temporal relationship from said electrical measurement of the heart;

means for determining at least one temporal plethysmographic value from said electromagnetic radiation absorption;

means for determining the extent of a pressure pulse from said first and second non-invasive measurements;

means for determining heart rate from said first and second non-invasive measurements;

means for determining stroke volume from said temporal arterial pressure, extent of a pressure pulse and demographic information; and

means for determining cardiac output from said stroke volume and said heart rate.

81. A method of detecting hypovolemia in a subject, comprising the step of comparing a change in oxygen saturation as a function of changes in inspiratory oxygen percentage to derive a model based estimate of left ventricular ejection fraction, said comparison being made on a heartbeat-to-heartbeat basis.

82. The method of claim 81, including the step of initially providing said subject with oxygen enriched air, said air being inhaled in one breadth by said subject, whereby said subject'"'"'s arterial oxygen saturation increases for a first period of time and decreases thereafter for a second period of time.

83. The method of claim 82, wherein a decay parameter is determined from said decrease in said subject'"'"'s arterial oxygen saturation during said second period of time.

84. The method of claim 83, wherein said ejection fraction is determined by calibrating said decay parameter via echocardiography.