Non-invasive measurement of suprasystolic signals

• US 6,994,675 B2
• Filed: 07/19/2001
• Issued: 02/07/2006
• Est. Priority Date: 07/19/2000
• Status: Active Grant

• Current Assignee: Uscom Ltd.
• Original Assignee: Nigel E. Sharrock
• Inventors: Sharrock, Nigel E.
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US10/221,530
• Publication Number:
  US 20030040675A1
• Time in Patent Office: 1,664 Days
• Field of Search: 600/481, 600/485, 600490-496, 600500-503, 600/547
• US Class Current: 600/500
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• 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 5/02141 Details of apparatus construction, e.g. pump units or housings therefor, cuff pressurising systems, arrangements of fluid conduits or circuits A61B5/02233, A61B5/0235 take precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• 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 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61B 5/6824 Arm or wrist

Abstract

An apparatus for assessing cardiovascular status of a mammal comprises a system for locally applying a pressure to an artery capable of restricting blood flow through said artery, a wideband external pulse transducer having an output and situated to measure suprasystolic signals proximate to said artery, and a computing device receiving said output for calculating vascular compliance values. The method described is particularly useful for determining cardiac output, assessing whether a pregnant female has preeclampsia or a patient has cardiac insufficiency, or assessing cardiac arrhythmias.

Claims

1. An apparatus for assessing cardiovascular status of a mammal comprising:

a system for locally applying a pressure to an artery, capable of restricting blood flow through said artery;

a wideband external pulse transducer having an output and situated to measure suprasystolic signals proximate to said artery; and

a computing device receiving said output for assessing large arterial vascular compliance values from said suprasystolic signals.

2. The apparatus of claim 1, wherein said computing device analyzes a temporal amplitude pattern of said output.

3. The apparatus of claim 2, wherein said system for locally applying a pressure to an artery occludes said artery, said temporal amplitude pattern comprises a series of adjacent amplitude peaks and related dips, and the computing device calculates a first ratio of (1) the amplitude difference of a first peak and a subsequent dip and (2) the amplitude difference of a second peak and the subsequent dip as well as a second ratio of (1) the amplitude difference of the first peak and a subsequent dip and (2) the amplitude difference of a third peak and a subsequent dip.

4. The apparatus of claim 3, wherein the computing device calculates said value as a function of the natural logarithm of said first ratio or a power function of said first ratio.

5. The apparatus of claim 1 which assesses whether a pregnant mammal has a preeclampsia condition.

6. The apparatus of claim 1 which assesses whether a pregnant mammal has cardiac insufficiency.

7. The apparatus of claim 1, wherein stroke volume is determined.

8. The apparatus of claim 1, wherein breathing efficacy is determined.

9. The apparatus of claim 1, wherein said computing device calculates a heart rate and value relating to stroke volume from said heart rate and said cardiac output.

10. The apparatus of claim 1, wherein said wideband external pulse transducer comprises a foil electret transducer.

11. The apparatus of claim 1, wherein said wideband external pulse transducer comprises a piezoelectric transducer.

12. The apparatus of claim 11, wherein said wideband external pulse transducer comprises a metalized polyvinylidene fluoride polymer film.

13. The apparatus of claim 1, wherein the large arterial vascular compliance values are aortic compliance values.

14. The apparatus of claim 1 for assessing a physiological factor.

15. A method for assessing the large arterial vascular compliance of a mammal, comprising the steps of:

(a) measuring the suprasystolic waveforms of a peripheral artery with blood flow occluded;

(b) determining the difference in amplitude between a first suprasystolic peak and a first suprasystolic trough of the suprasystolic waveform;

(c) determining the difference in amplitude between a second suprasystolic peak and a second suprasystolic trough of the suprasystolic waveform;

(d) determining the ratio of a difference from step (b) to the difference from step (c); and

(e) calculating a large arterial vascular compliance value.

16. The method of claim 15, wherein the large arterial vascular compliance value is the aortic compliance value.

17. The method of claim 15, wherein in step (a) the suprasystolic waveforms are measured over a peripheral artery with a blood flow therethrough occluded.

18. The method of claim 15, further comprising the step of determining a cardiac output based upon the large arterial vascular compliance value.

19. The method of claim 15, wherein stroke volume is determined.

20. The method of claim 15, wherein cardiac output is determined.

21. The method of claim 15, wherein breathing efficacy is determined.

22. The method of claim 15, wherein patients are monitored during administration of anesthesia.

23. The method of claim 15 for better prescribing treatment for hypertension.

24. The method of claim 15, wherein shock is assessed.

25. The method of claim 15, wherein heart failure is assessed.

26. The method of claim 15 for assessing a physiological factor.

27. The method of claim 26, wherein the physiological factor is heart rate, blood pressure/pulse pressure, or pulse wave delay.

28. A noninvasive cardiac monitoring apparatus comprising:

a brachial artery cuff;

a pressure control system for controlling a pressure in said cuff;

a wideband acoustic transducer having an output and being adapted to measure acoustic emission proximate to said cuff; and

a system for analyzing said output at least during a period of complete occlusion of flow in the brachial artery due to pressurization of said cuff, to assess large arterial vascular compliance from a portion of said output representing the period of complete occlusion.

29. The apparatus of claim 28, wherein the large arterial vascular compliance is aortic compliance.

30. The apparatus of claim 28, wherein said wideband external pulse transducer comprises a foil electret transducer.

31. The apparatus of claim 28, wherein said wideband external pulse transducer comprises a piezoelectric transducer.

32. The apparatus of claim 31, wherein said wideband external pulse transducer comprises a metalized polyvinylidene fluoride polymer film.

33. The apparatus of claim 28, wherein said analyzing system comprises means for determining the difference in amplitude between a first suprasystolic peak and a first suprasystolic trough and the difference between the amplitude of a second suprasystolic peak and a second suprasystolic trough and means for calculating the ratio of the differences.

34. The apparatus of claim 28, wherein said analyzing system comprises means for determining the difference in amplitude between a first suprasystolic peak and a first suprasystolic trough and the difference between the amplitude of a third suprasystolic peak and a third suprasystolic trough and means for calculating the ratio of the differences.

35. The apparatus of claim 33 or 34, wherein said estimating means calculates said compliance value as a function of the natural logarithm of said ratio or a power function of said ratio.

36. The apparatus of claim 28, further comprising means for determining cardiac output.

37. The apparatus of claim 28 for assessing a physiological factor.

38. A method for assessing the cardiovascular status of a mammal comprising:

providing a system for locally applying a pressure to an artery, capable of restricting blood flow through said artery;

providing a wideband external pulse transducer having an output and situated to measure acoustic suprasystolic signals proximate to said artery; and

analyzing the output of the wideband external pulse transducer to calculate a large arterial vascular compliance value based on the suprasystolic signals.

39. The method of claim 38, wherein the large arterial vascular compliance value is an aortic compliance value.

40. The method of claim 38, wherein said analysis determines a likely diagnosis or prognosis of the mammal.

41. The method of claim 38 which assesses whether a pregnant mammal has a preeclampsia condition.

42. The method of claim 38 which assesses whether the mammal has cardiac insufficiency.

43. The method of claim 38, wherein breathing efficacy is determined.

44. The method of claim 38, wherein cardiac arrhythmias are assessed.

45. The method of claim 38, wherein endothelia dysfunction is assessed.

46. The method of claim 38, wherein a cardiovascular aging profile is determined.

47. The method of claim 38, wherein the diastolic reflective wave assesses the degree of peripheral vasoconstriction.

48. The method of claim 38, wherein suprasystolic signals are used to measure the duration of systole and/or the duration of diastole.

49. The method of claim 38, wherein patients are monitored during administration of anesthesia.

50. The method of claim 38 for better prescribing treatment for hypertension.

51. The method of claim 38, wherein shock is assessed.

52. The method of claim 38, wherein heart failure is assessed.

53. The method of claim 38 for assessing a physiological factor.

54. The method of claim 53, wherein the physiological factor is heart rate, blood pressure/pulse pressure, or pulse wave delay.