Non-invasive measurement of suprasystolic signals

• US 20030040675A1
• Filed: 09/13/2002
• Published: 02/27/2003
• Est. Priority Date: 07/19/2000
• Status: Active Grant

• Current Assignee: Uscom Ltd.
• Original Assignee: Nigel E. Sharrock
• Inventors: Sharrock, Nigel E.
• Granted Patent: US 6,994,675 B2
• Time in Patent Office: Days
• US Class Current: 600/490
• 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 calculating vascular compliance values.

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 vascular compliance values are aortic compliance values.

53. The apparatus of claim 1 or 27 for assessing a physiological factor.

14. A method for determining the 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;

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

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

(e) calculating the vascular compliance value.

15. The method of claim 14, wherein the vascular compliance value is the aortic compliance value.

16. The method of claim 14, wherein in step (a) the suprasystolic waveforms are measured over a peripheral artery with a blood flow therethrough occluded.

17. The method of claim 14, further comprising the step of determining a cardiac output based upon the vascular compliance value.

18. The method of claim 14, wherein stroke volume is determined.

19. The method of claim 14, wherein cardiac output is determined.

20. The method of claim 14, wherein breathing efficacy is determined.

21. The method of claim 14, wherein patients are monitored during administration of anesthesia.

22. The method of claim 14 for better prescribing treatment for hypertension.

23. The method of claim 14, wherein shock is assessed.

24. The method of claim 14, wherein heart failure is assessed.

25. The method of claim 14 for assessing a physiological factor.

26. The method of claim 25, wherein the physiological factor is heart rate, blood pressure/pulse pressure, or pulse wave delay.

27. A noninvasive cardiac monitoring apparatus comprising:

a brachial artery cuff;

pressure control system for controlling a pressure in said cuff;

a wideband acoustic transducer having an output and adopted 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 determine vascular compliance.

28. The apparatus of claim 27, wherein the vascular compliance is aortic compliance.

29. The apparatus of claim 27, wherein said wideband external pulse transducer comprises a foil electret transducer.

30. The apparatus of claim 27, wherein said wideband external pulse transducer comprises a piezoelectric transducer.

31. The apparatus of claim 30, wherein said wideband external pulse transducer comprises a metalized polyvinylidene fluoride polymer film.

32. The apparatus of claim 27, 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.

33. The apparatus of claim 27, 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.

34. The apparatus of claim 32 or 33, 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.

35. The apparatus of claim 27, further comprising means for determining cardiac output.

36. 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 vascular compliance value.

37. The method of claim 36, wherein the vascular compliance value is an aortic compliance value.

38. The method of claim 36, wherein said analysis determines a likely diagnosis or prognosis of the mammal.

39. The method of claim 36 which assesses whether a pregnant mammal has a preeclampsia condition.

40. The method of claim 36 which assesses whether the mammal has cardiac insufficiency.

41. The method of claim 36, wherein breathing efficacy is determined.

42. The method of claim 36, wherein cardiac arrhythmias are assessed.

43. The method of claim 36, wherein endothelia dysfunction is assessed.

44. The method of claim 36, wherein a cardiovascular aging profile is determined.

45. The method of claim 36, wherein the diastolic reflective wave assesses the degree of peripheral vasoconstriction.

46. The method of claim 36, wherein suprasystolic signals are used to measure the duration of systole and/or the duration of diastole.

47. The method of claim 36, wherein patients are monitored during administration of anesthesia.

48. The method of claim 36 for better prescribing treatment for hypertension.

49. The method of claim 36, wherein shock is assessed.

50. The method of claim 36, wherein heart failure is assessed.

51. The method of claim 36 for assessing a physiological factor.

52. The method of claim 51, wherein the physiological factor is heart rate, blood pressure/pulse pressure, or pulse wave delay.