Methods and apparatus for measuring arterial compliance, improving pressure calibration, and computing flow from pressure data

• US 6,733,461 B2
• Filed: 08/01/2002
• Issued: 05/11/2004
• Est. Priority Date: 08/01/2002
• Status: Expired due to Fees

• Current Assignee: Hypertension Diagnostics, Inc.
• Original Assignee: Hypertension Diagnostics, Inc.
• Inventors: Bratteli, Christopher W.
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US10/211,857
• Publication Number:
  US 20040024324A1
• Time in Patent Office: 649 Days
• Field of Search: 600/490, 600/492, 600/493, 600/494, 600/495, 600/496, 600/481, 600/483, 600/485, 600/486, 600/300, 128/920, 128/923
• US Class Current: 600/490
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: Y10S 128/92 Computer assisted medical diagnostics

Abstract

Methods and apparatus for measuring arterial compliance using combined noninvasive arterial tonometry and cuff oscillometry. Some embodiments include a calibration method using an oscillometric signal to calibrate the pressures of tonometric signals in a contralateral arterial site. The times at which two of the three oscillometric blood pressures (systolic pressure, mean pressure, diastolic pressure) are acquired are identified with times of un-calibrated tonometric pressure waveform. These blood pressures are then used to calibrate the tonometric pressure waveform along (optionally) with adjustments for head pressure. For example, a left brachial arterial cuff oscillometric signal is acquired coincidentally with an un-calibrated right radial arterial pressure tonometric signal. The time points of mean arterial pressure and diastolic pressure are determined from the oscillometric signal and identified with coinciding time points on the tonometric signal to produce a calibration. All pressures are then adjusted by the head pressure between the brachial and radial sites.

Claims

1. A method for computerized calculation of a variable physiological parameter of a patient, the method comprising:

(a) identifying the physiological parameter to be quantitatively monitored and estimated;

(b) measuring an oscillometric blood-pressure signal and a tonometric blood-pressure signal, which signals are quantitatively dependent on a particular value for the physiological parameter;

(c) obtaining a sequence of values that are based on the oscillometric signal and the tonometric signal;

(d) receiving the sequence of values as input signals to a computer system;

(e) processing the input signals within the computer system to convert the sequence of values to an output signal corresponding to the particular value of the physiological parameter; and

(f) using the oscillometric signal to calibrate the tonometric signal;

wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric signal S_r(t) as follows;

2. The method of claim 1, further comprising:

(g) calculating a first compliance value based on the calibrated radial pressure waveform;

(h) estimating end-effects of the oscillometric signal; and

(i) correcting the first compliance value using the estimated end effects.

3. The method of claim 1, further comprising:

(g) calculating a first compliance value based on the calibrated radial pressure waveform.

4. A method for computerized calculation of a variable physiological parameter of a patient, the method comprising:

(a) identifying the physiological parameter to be quantitatively monitored and estimated;

(b) measuring an oscillometric signal and a tonometric physiological signal, which signals are quantitatively dependent on a particular value for the physiological parameter;

(c) obtaining a sequence of values that are based on the oscillometric signal and the tonometric signal;

(d) receiving the sequence of values as input signals to a computer system; and

(e) processing the input signals within the computer system to convert the sequence of values to an output signal corresponding to the particular value of the physiological parameter;

wherein the processing function (e) includes estimating a first compliance value using a compliance pressure curve.

5. The method of claim 4, further comprising:

(f) using the oscillometric signal to calibrate the tonometric signal.

6. The method of claim 4, further comprising:

(f) using the oscillometric signal to calibrate the tonometric signal;

wherein two points along the oscillometric signal defining a subportion of the oscillometric pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal.

7. The method of claim 6, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood pressure.

8. The method of claim 6, wherein the two points along the oscillometric signal correspond to a systolic blood pressure and a mean blood pressure.

9. The method of claim 4, further comprising:

(f) using the oscillometric signal to calibrate the tonometric signal;

wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric signal S_r(t) as follows;

10. A method for computerized calculation of a variable physiological parameter of a patient,

p=pgh are calibration factors, and wherethe method comprising:

p=density of blood,

(a) identifying the physiological parameter to be quantitatively monitored and estimated;

g=acceleration to gravity,

(b) measuring an oscillometric signal and a tonometric physiological signal, which

h=height difference between the oscillometric and the tonometricsignals are quantitatively dependent on a particular value for the physiological parameter;

measurement sites, and is zero if the patient is supine,

(c) obtaining a sequence of values that are based on the oscillometric signal and the tonometric signal;

(d) receiving the sequence of values as input signals to a computer system;

(e) processing the input signals within the computer system to convert the sequence of values to an output signal corresponding to the particular value of the physiological parameter; and

(f) using a tonometric signal to calibrate oscillometric pressure signals in a contralateral arterial site.

11. A method for computerized calculation of a variable physiological parameter of a patient, the method comprising:

(a) identifying the physiological parameter to be quantitatively monitored and estimated;

(b) measuring an oscillometric signal and a tonometric physiological signal, which signals are quantitatively dependent on a particular value for the physiological parameter;

(c) obtaining a sequence of values that are based on the oscillometric signal and the tonometric signal;

(d) receiving the sequence of values as input signals to a computer system;

(e) processing the input signals within the computer system to convert the sequence of values to an output signal corresponding to the particular value of the physiological parameter; and

(f) estimating end-effects of oscillometric sensor apparatus on the oscillometric signal.

12. The method of claim 11, further comprising:

(g) using an oscillometric signal to calibrate tonometric pressure signals in a contralateral arterial site.

13. The method of claim 11, further comprising:

(g) using the oscillometric signal to calibrate tonometric pressure; and

(h) calculating a value for the physiological parameter.

14. The method of claim 13, wherein the physiological parameter to be estimated is compliance, the method further comprising:

(i) calculating a first compliance value based on the calibrated tonometric pressure waveform; and

(j) correcting the first compliance value using the estimated end effects.

15. The method of claim 11, further comprising:

(g) using the oscillometric signal to calibrate tonometric pressure;

wherein two points along the oscillometric signal defining a subportion of a oscillometric pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal; and

(h) calculating a value for the physiological parameter.

16. The method of claim 15, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood pressure.

17. The method of claim 11, further comprising:

(g) using the oscillometric signal to calibrate the tonometric signal;

wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric signal S_r(t) as follows;

18. The method of claim 17, wherein the physiological parameter to be estimated is compliance, the method further comprising:

(i) calculating a first compliance value based on the calibrated tonometric pressure waveform; and

(j) correcting the first compliance value using the estimated end effects.

51. The system of claim 14, wherein the computer system further calibrates the tonometric signal based on the oscillometric signal, and wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric signal S_r(t) as follows:

52. The system of claim 51, wherein the physological parameter to be estimated is compliance, wherein the computer system further calculates a first compliance value based on the calibrated tonometric pressure waveform, and corrects the first compliance value using the estimated end effects.

19. A method for computerized calculation of a variable physiological parameter of a patient, the method comprising:

(a) identifying the physiological parameter to be quantitatively monitored and estimated;

(b) coupling at least a first sensor and a second sensor to the patient, the first sensor and the second sensor each being responsive to monitor different time-varying physiological waveforms, which waveforms are quantitatively dependent on a particular value for the physiological parameter;

(c) obtaining a time-correlated dual sequence of digital values that are based on the waveforms monitored by the first and second sensors;

(d) receiving the sequence of digital values as input signals to a computer system; and

(e) processing the input signals within the computer system to convert the time-correlated dual sequence of digital values to an output signal corresponding to a value of the physiological parameter, wherein the physiological parameter is vascular compliance, the first sensor monitors an oscillometric waveform, and the second sensor monitors a tonometric waveform.

20. The method of claim 19, further comprising:

(f) using an oscillometric signal to calibrate tonometric pressure;

wherein two points along the oscillometric signal defining a subportion of the oscillometric pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal.

21. The method of claim 20, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood presure.

22. The method of claim 20, wherein the two points along the oscillometric signal correspond to a systolic blood pressure and a mean blood pressure.

23. The method of claim 19, further comprising:

(f) using the oscillometric waveform to calibrate tonometric waveform;

wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric waveform S_r(t) as follows;

24. The method of claim 19, where the (e) processing of the input signals includes estimating a first compliance value using a compliance pressure curve.

25. The method of claim 19, further comprising:

(f) estimating end-effects of oscillometric sensor apparatus on the oscillometric signal.

26. The method of claim 25, wherein the physiological parameter to be estimated is compliance, the method further comprising:

(g) using an oscillometric signal to calibrate tonometric pressure;

wherein two points along the oscillometric signal defining a subportion of the oscillometric pressure range are used with two corresponding points along the tonometric signal to generate a calibrated tonometric signal;

(h) calculating a first compliance value based on the calibrated tonometric pressure waveform; and

(i) correcting the first compliance value using the estimated end effects.

27. A method for computerized calculation of a variable physiological parameter of a patient, the method comprising:

(a) identifying the physiological parameter to be quantitatively monitored and estimated;

(b) coupling at least a first sensor and a second sensor to the patient, the first sensor and the second sensor each being responsive to monitor different time-varying physiological waveforms, which waveforms are quantitatively dependent on a particular value for the physiological parameter;

(c) obtaining a time-correlated dual sequence of digital values that are based on the waveforms monitored by the first and second sensors;

(d) receiving the sequence of digital values as input signals to a computer system; and

(e) processing the input signals within the computer system to convert the time-correlated dual sequence of digital values to an output signal corresponding to a value of the physiological parameter wherein the physiological parameter is vascular compliance, the first sensor monitors an oscillometric waveform derived from oscillometric signals of a brachial artery site, and the second sensor monitors a tonometric waveform derived from tonometric signals of a contralateral radial artery site.

28. The method of claim 27, further comprising:

(f) using an oscillometric signal to calibrate tonometric pressure;

wherein two points along the oscillometric signal defining a subportion of the oscillometric pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal.

29. The method of claim 28, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood pressure.

30. The method of claim 28, wherein the two points along the oscillometric signal correspond to a systolic blood pressure and a mean blood pressure.

31. The method of claim 27, further comprising:

(f) using the oscillometric waveform to calibrate the tonometric waveform;

wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric waveform S_r(t) as follows;

32. The method of claim 27, where the (e) processing of the input signals includes estimating a first compliance value using a compliance pressure curve.

33. The method of claim 27, further comprising:

(f) estimating end-effects of oscillometric sensor apparatus on the oscillometric signal.

34. The method of claim 33, wherein the physiological parameter to be estimated is compliance, the method further comprising:

(g) using an oscillometric signal to calibrate tonometric pressure;

wherein two points along the oscillometric signal defining a subportion of the oscillometric pressure range are used with two corresponding points along the tonometric signal to generate a calibrated tonometric signal;

(h) calculating a first compliance value based on the calibrated tonometric pressure waveform; and

(i) correcting the first compliance value using the estimated end effects.

35. A system for computerized calculation of a variable physiological parameter of a patient, the system comprising:

a first sensor that measures an oscillometric blood-pressure signal that is quantitatively dependent on a particular value for the physiological parameter;

a second sensor that measures a tonometric blood-pressure signal that is quantitatively dependent on the particular value for the physiological parameter;

a first analog-to-digital converter, operatively coupled to the first sensor, that generates a first sequence of digital values that are based on the oscillometric signal;

a second analog-to-digital converter, operatively coupled to the second sensor, that generates a second sequence of digital values that are based on the tonometric signal; and

a computer system, operatively coupled to the first and second analog-to-digital converters, wherein the computer system processes the first and second sequences of values to generate an output signal corresponding to the particular value of the physiological parameter, and the computer uses the oscillometric signal to calibrate the tonometric signal, and wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric signal S_r(t) as follows;

36. The system of claim 35, wherein the computer system further calculates a first compliance value based on the calibrated radial pressure waveform, estimates end-effects of the oscillometric signal, and corrects the first compliance value using the estimated end effects.

37. A system for computerized calculation of a variable physiological parameter of a patient, the system comprising:

a first sensor that measures an oscillometric physiological signal that is quantitatively dependent on a particular value for the physiological parameter;

a second sensor that measures a tonometric physiological signal that is quantitatively dependent on the particular value for the physiological parameter;

a first analog-to-digital converter, operatively coupled to the first sensor, that generates a first sequence of digital values that are based on the oscillometric signal;

a second analog-to-digital converter, operatively coupled to the second sensor, that generates a second sequence of digital values that are based on the tonometric signal; and

a computer system, operatively coupled to the first and second analog-to-digital converters, wherein the computer system processes the first and second sequences of values to generate an output signal corresponding to the particular value of the physiological parameter, wherein the computer system further estimates a first compliance value using;

a compliance pressure curve.

38. The system of claim 37, wherein the first sensor senses the oscillometric signal from one side of a patient, the second sensor senses the tonometric signal from a contralateral arterial site, and the computer uses the oscillometric signal to calibrate tonometric pressure signals in the contralateral arterial site.

39. The system of claim 37, wherein the oscillometric physiological signal is an oscillometric blood pressure signal, the tonometric physiological signal is a tonometric blood pressure signal, and the computer system further calibrates the tonometric pressure signal based on the oscillometric pressure signal.

40. The system of claim 37, wherein the oscillometric physiological signal is an oscillometric blood pressure signal, the tonometric physiological signal is a tonometric blood pressure signal, and the computer system further calibrates the tonometric blood pressure signal with the oscillometric blood pressure signal, and wherein two points along the oscillometric signal that define a subportion of a osillometric pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal.

41. The system of claim 40, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood pressure.

42. The system of claim 40, wherein the two points along the oscillometric signal correspond to a systolic blood pressure and a mean blood pressure.

43. The system of claim 37, wherein the computer system further calibrates the tonometric blood pressure signal with the oscillometric blood pressure signal;

wherein a calibrated radial pressure waveform P_r(t) is derived from the tonometric signal S_r(t) as follows;

44. A system for computerized calculation of a variable physiological parameter of a patient, the system comprising:

a first sensor that measures an oscillometric physiological signal that is quantitatively dependent on a particular value for the physiological parameter;

a second sensor that measures a tonometric physiological signal that is quantitatively dependent on the particular value for the physiological parameter;

a first analog-to-digital converter, operatively coupled to the first sensor, that generates a first sequence of digital values that are based on the oscillometric signal;

a second analog-to-digital converter, operatively coupled to the second sensor, that generates a second sequence of digital values that are based on the tonometric signal; and

a computer system, operatively coupled to the first and second analog-to-digital converters, wherein the computer system processes the first and second sequences of values to generate an output signal corresponding to the particular value of the physiological parameter, wherein the computer system further uses a tonometric signal to calibrate oscillometric pressure signals in a contralateral arterial site.

45. A system for computerized calculation of a variable physiological parameter of a patient, the system comprising:

a first sensor that measures an oscillometric physiological signal that is quantitatively dependent on a particular value for the physiological parameter;

a second sensor that measures a tonometric physiological signal that is quantitatively dependent on the particular value for the physiological parameter;

a first analog-to-digital converter, operatively coupled to the first sensor, that generates a first sequence of digital values that are based on the oscillometric signal;

a second analog-to-digital converter, operatively coupled to the second sensor, that generates a second sequence of digital values that are based on the tonometric signal; and

a computer system, operatively coupled to the first and second analog-to-digital converters, wherein the computer system processes the first and second sequences of values to generate an output signal corresponding to the particular value of the physiological parameter, wherein the computer system further estimates end-effects of oscillometric sensor apparatus on the oscillometric signal.

46. The system of claim 45, wherein the computer system further includes:

means for obtaining a time-correlated dual sequence of digital values that are based on the waveforms monitored by the first and second sensors; and

means for processing the input signals to convert the time-correlated dual sequence of digital values to an output signal corresponding to a value of the physiological parameter.

47. The system claim 45, wherein the computer system further calibrates the tonometric blood pressure signal with the oscillometric blood pressure signal, and calculates a value for the physiological parameter based on the calibrated tonometric signal.

48. The system of claim 47, wherein the physiological parameter to be estimated is compliance, the system further calculates a first compliance value based on the calibrated tonometric pressure waveform, and corrects the first compliance value based on the estimated end effects.

49. The system of claim 45, wherein the computer system further calibrates the tonometric signal based on the oscillometric signal, where two points that define a subportion of a oscillometric pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal, and the computer system calculates a value for the physiological parameter.

50. The system of claim 49, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood pressure.

53. The system of claim 45, wherein the computer system further calibrates the tonometric signal based on the oscillometric signal, wherein two points along the oscillometric signal defining a subportion of the oscillometrtic pressure range are used with two corresponding points along the tonometric signal to calibrate the tonometric signal.

54. The system of claim 53, wherein the two points along the oscillometric signal correspond to a diastolic blood pressure and a mean blood pressure.

55. The system of claim 53, wherein the two points along the oscillometric signal correspond to a systolic blood pressure and a mean blood pressure.