System and method for accurately monitoring the cardiovascular state of a living subject

• US 5,931,790 A
• Filed: 06/06/1997
• Issued: 08/03/1999
• Est. Priority Date: 06/06/1997
• Status: Expired due to Fees

• Current Assignee: Omron Healthcare Company Limited (Omron Corporation)
• Original Assignee: Southwest Research Institute
• Inventors: Peel, Harry H. III
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/870,460
• Time in Patent Office: 788 Days
• Field of Search: 600/485, 600/490, 600/493-6, 600/500, 600/503
• US Class Current: 600/494
• 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

Abstract

A blood-pressure measurement system accurately monitors a living subject'"'"'s cardiovascular state, even if the living subject'"'"'s blood pressure changes during a measurement, the living subject exhibits frequent arrhythmias, or motion artifacts are present during the blood-pressure measurement. The blood-pressure measurement system of this invention provides an arrhythmia-pulse correcting circuit that corrects the amplitudes of oscillometric pulses produced by arrhythmias. An oscillometric-systolic-pressure correcting circuit corrects the measured systolic oscillometric blood pressure when a living subject'"'"'s blood pressure is changing during the oscillometric blood-pressure measurement. A quality-assurance and data-checking circuit determines the reliability of the oscillometric blood-pressure values, determines the cause of problems in the blood-pressure measurement process, alerts a user if a reliable oscillometric blood-pressure measurement cannot be obtained and performs user-specified living subject evaluation checks.

Claims

1. A blood-pressure measurement system, comprising:

an oscillometric pulse-wave detection device that detects oscillometric pressure pulse waves produced by a cardiac muscle of a living subject during an oscillometric-blood-pressure measurement, the oscillometric pressure pulse waves propagating through an artery of the living subject;

an arrhythmia-pulse correcting circuit that identifies abnormal oscillometric pressure pulse waves and corrects the amplitudes of oscillometric pressure pulse waves produced by arrhythmias; and

a blood-pressure measuring circuit that measures a blood pressure of the living subject based on amplitudes of the oscillometric pressure pulse waves detected by the oscillometric pulse-wave detection device and on the corrected amplitudes of oscillometric pressure pulse waves produced by arrythmias.

2. The blood-pressure measurement system of claim 1, wherein the blood-pressure measuring circuit measures a systolic blood pressure, a diastolic blood pressure and a mean blood pressure of the living subject.

3. The blood-pressure measurement system of claim 1, further comprising a quality-assurance and data checking circuit that determines a quality of blood-pressure measurement data based on predetermined quality-assurance rules and criteria, the quality-assurance and data checking circuit initiating a new oscillometric-blood-pressure measurement if the quality of the blood-pressure measurement data is below a predetermined threshold.

4. The blood-pressure measurement system of claim 3, wherein the quality-assurance and data checking circuit initiates a new oscillometric-blood-pressure measurement when the arrhythmia-pulse correcting circuit identifies a predetermined number of abnormal oscillometric pressure pulse waves produced by arrythmias or motion artifacts.

5. The blood-pressure measurement system of claim 3, wherein the quality-assurance and data checking circuit performs user-specified living subject evaluation checks based on predetermined criteria.

6. The blood-pressure measurement system of claim 1, wherein the oscillometric-pulse-wave detection device comprises a constriction device that applies a changing constriction pressure to a portion of the living subject.

7. The blood-pressure measurement system of claim 6, wherein the constriction device comprises:

a cuff wrapable around the portion of the living subject that applies a constriction pressure to the portion of the living subject when the cuff is wrapped around the portion of the living subject; and

a cuff-pressure regulating circuit that controls the constriction pressure applied by the cuff to the portion of the living subject, the cuff pressure regulating circuit changing the constriction pressure applied by the cuff to the portion of the living subject during an oscillometric-blood-pressure measurement.

8. The blood-pressure measurement system of claim 1, further comprising:

a first pulse-wave detection device that detects first pulse waves from a first portion of the living subject; and

a second pulse-wave detection device that detects second pulse waves from a second portion of the living subject.

9. The blood-pressure measurement system of claim 8, wherein the arrhythmia-pulse-correcting circuit corrects the amplitude of a detected oscillometric pressure pulse wave produced by an arrhythmia based on the amplitude of a previous normal pulse wave detected by the second pulse-wave detection device and the amplitude of a current pulse wave detected by the second pulse-wave detection device.

10. The blood-pressure measurement system of claim 9, wherein the arrhythmia-pulse-correcting circuit corrects the amplitude of a detected oscillometric pressure pulse wave produced by an arrhythmia using the relationship:

space="preserve" listing-type="equation">SM.sub.1 (c)=SM.sub.1 (a) Δ

V.sub.f (n)/Δ

V.sub.f (a)!,

where;

SM₁ (c) is a corrected oscillometric pressure pulse wave amplitude;

SM₁ (a) is the detected oscillometric pressure pulse wave amplitude;

Δ

V_f (n) is the amplitude of the previous normal pulse wave detected by the second pulse-wave detection device; and

Δ

V_f (a) is the amplitude of the current pulse wave detected by the second pulse-wave detection device.

11. The blood-pressure measurement system of claim 8, wherein the first pulse-wave detection device comprises an electrocardiographic waveform detection device.

12. The blood-pressure measurement system of claim 11, wherein the arrhythmia-pulse-correcting circuit determines whether an oscillometric pressure pulse wave was produced by an arrhythmia based on a shape of a corresponding pulse wave detected by the electrocardiographic waveform detection device.

13. The blood-pressure measurement system of claim 8, wherein the second pulse-wave detection device comprises an oximeter sensor.

14. The blood-pressure measurement system of claim 13, wherein the oximeter sensor comprises a photoelectric pulse-wave detector.

15. The blood-pressure measurement system of claim 8, further comprising:

a pulse-wave-propagation information obtaining circuit that determines time differences between predetermined periodic points on pulse waves detected by the first pulse-wave detection device and predetermined periodic points on corresponding pulse waves detected by the second pulse-wave detection device;

a blood-pressure/pulse-wave-propagation-information relationship determining circuit that determines a relationship between the time differences determined by the pulse-wave-propagation information obtaining circuit and a blood pressure of the living subject; and

an estimated-blood-pressure determining circuit that successively determines an estimated blood pressure based on the relationship determined by the blood-pressure/pulse-wave-propagation-information relationship determining circuit.

16. The blood-pressure measurement system of claim 15, wherein the blood-pressure/pulse-wave-propagation-information relationship determining circuit determines a relationship between the time differences determined by the pulse-wave-propagation information obtaining circuit and a systolic blood pressure of the living subject.

17. The blood-pressure measurement system of claim 15, wherein the pulse-wave-propagation information obtaining circuit determines pulse wave propagation rates from the determined time differences, and the blood-pressure/pulse-wave-propagation-information relationship determining circuit determines a relationship between the pulse wave propagation rates determined by the pulse-wave-propagation information obtaining circuit and a blood pressure of the living subject.

18. The blood-pressure measurement system of claim 17, wherein the blood-pressure/pulse-wave-propagation-information relationship determining circuit determines a relationship between the pulse wave propagation rates determined by the pulse-wave-propagation information obtaining circuit and a systolic blood pressure of the living subject.

19. The blood-pressure measurement system of claim 15, further comprising an oscillometric-systolic-pressure correcting circuit that corrects a systolic blood pressure measured by the blood-pressure measuring circuit when the living subject'"'"'s blood pressure changes during an oscillometric-blood-pressure measurement.

20. The blood-pressure measurement system of claim 19, wherein the oscillometric-systolic-pressure correcting circuit identifies a pulse wave that was used by the blood-pressure measuring circuit to determine a diastolic blood pressure of the living subject and, when the estimated blood pressure of the living subject changes by a predetermined amount during the oscillometric-blood-pressure measurement, displays an estimated systolic blood pressure for the pulse wave from which the diastolic blood pressure was determined.

21. The blood-pressure measurement system of claim 15, further comprising:

a pulse-period measuring circuit that determines a pulse period based on a time difference between predetermined periodic points on successive pulse waves detected by the first pulse-wave detection device;

a pulse-period-abnormality judging circuit that determines whether a pulse-period determined by the pulse-period measuring circuit is normal or abnormal;

a pulse-wave-area determining circuit that determines a pulse-wave area for each pulse wave detected by the second pulse-wave detection device; and

a pulse-wave-area-abnormality judging circuit that determines whether a pulse-wave area determined by the pulse-wave-area determining circuit is normal or abnormal.

22. The blood-pressure measurement system of claim 21, wherein the arrhythmia-pulse correcting circuit determines whether an oscillometric pressure pulse wave is abnormal based on the determinations by the pulse-period-abnormality judging circuit and the pulse-wave-area-abnormality judging circuit.

23. The blood-pressure measurement system of claim 21, further comprising an estimated-blood-pressure-abnormality judging circuit that determines whether an estimated blood pressure determined by the estimated-blood-pressure determining circuit is normal or abnormal.

24. The blood-pressure measurement system of claim 23, wherein the estimated-blood-pressure-abnormality judging circuit, the pulse-wave-area-abnormality judging circuit and the pulse-period-abnormality judging circuit together comprise a blood-pressure-measurement starting circuit.

25. The blood-pressure measurement system of claim 24, wherein the blood-pressure-measurement starting circuit initiates a new oscillometric blood-pressure measurement when at least one of the estimated blood pressure, the pulse-wave area and the pulse period is determined to be abnormal.

26. The blood-pressure measurement system of claim 24, wherein the blood-pressure-measurement starting circuit initiates a new oscillometric blood-pressure measurement when the estimated blood pressure and at least one of the pulse-wave area and pulse period are determined to be abnormal.

27. A blood-pressure measurement system, comprising:

an oscillometric pulse-wave detection device that detects oscillometric pressure pulse waves produced by a cardiac muscle of a living subject during an oscillometric-blood-pressure measurement, the oscillometric pressure pulse waves propagating through an artery of the living subject;

an arrhythmia-pulse correcting circuit that identifies abnormal oscillometric pressure pulse waves and corrects the amplitudes of oscillometric pressure pulse waves produced by arrhythmias;

a blood-pressure measuring circuit that measures at least a systolic blood pressure and a diastolic blood pressure of the living subject based on amplitudes of the oscillometric pressure pulse waves detected by the oscillometric pulse-wave detection device and on the corrected amplitudes of oscillometric pressure pulse waves produced by arrythmias;

a first pulse-wave detection device that detects first pulse waves from a first portion of the living subject;

a second pulse-wave detection device that detects second pulse waves from a second portion of the living subject;

a pulse-wave-propagation information obtaining circuit that determines time differences between predetermined periodic points on pulse waves detected by the first pulse-wave detection device and predetermined periodic points on corresponding pulse waves detected by the second pulse-wave detection device;

a blood-pressure/pulse-wave-propagation-information relationship determining circuit that determines a relationship between the time differences determined by the pulse-wave-propagation information obtaining circuit and a blood pressure of the living subject;

an estimated-blood-pressure determining circuit that successively determines an estimated blood pressure based on the relationship determined by the blood-pressure/pulse-wave-propagation-information relationship determining circuit;

an oscillometric-systolic-pressure correcting circuit that corrects a systolic blood pressure measured by the blood-pressure measuring circuit when the living subject'"'"'s blood pressure changes during an oscillometric-blood-pressure measurement;

a blood-pressure-measurement starting circuit that determines whether each of an estimated blood pressure, a pulse-wave area and a pulse period is normal or abnormal, the blood-pressure-measurement starting circuit initiating a new oscillometric-blood-pressure measurement when at least one of the estimated blood pressure, the pulse-wave area and the pulse period is determined to be abnormal; and

a quality-assurance and data checking circuit that determines a quality of blood-pressure measurement data based on predetermined quality-assurance rules and criteria, the quality-assurance and data checking circuit initiating a new oscillometric-blood-pressure measurement if the quality of the blood-pressure measurement data is below a predetermined threshold.

28. The blood-pressure measurement system of claim 27, wherein the quality-assurance and data checking circuit initiates a new oscillometric-blood-pressure measurement when the arrhythmia-pulse correcting circuit identifies a predetermined number of abnormal oscillometric pressure pulse waves.

29. The blood-pressure measurement system of claim 27, wherein the blood-pressure measuring circuit measures a mean blood pressure of the living subject and wherein the quality-assurance and data checking circuit initiates a new oscillometric-blood-pressure measurement when the mean blood pressure falls below a predetermined value.

30. The blood-pressure measurement system of claim 27, wherein the quality-assurance and data checking circuit performs user-specified living subject evaluation checks based on predetermined criteria.

31. The blood-pressure measurement system of claim 27, wherein the blood-pressure-measurement starting circuit initiates a new oscillometric blood-pressure measurement when the estimated blood pressure and at least one of the pulse-wave area and pulse period are determined to be abnormal.

32. The blood-pressure measurement system of claim 27, wherein the arrhythmia-pulse-correcting circuit corrects the amplitude of a detected oscillometric pressure pulse wave produced by an arrhythmia based on the amplitude of a previous normal pulse wave detected by the second pulse-wave detection device and the amplitude of a current pulse wave detected by the second pulse-wave detection device.

33. The blood-pressure measurement system of claim 32, wherein the arrhythmia-pulse-correcting circuit corrects the amplitude of a detected oscillometric pressure pulse wave produced by an arrhythmia using the relationship:

space="preserve" listing-type="equation">SM.sub.1 (c)=SM.sub.1 (a) Δ

V.sub.f (n)/Δ

V.sub.f (a)!,

where;

SM₁ (c) is a corrected oscillometric pressure pulse wave amplitude;

SM₁ (a) is the detected oscillometric pressure pulse wave amplitude;

Δ

V_f (n) is the amplitude of the previous normal pulse wave detected by the second pulse-wave detection device; and

Δ

V_f (a) is the amplitude of the current pulse wave detected by the second pulse-wave detection device.

34. The blood-pressure measurement system of claim 27, wherein the oscillometric-pulse-wave detection device comprises a constriction device that applies a changing constriction pressure to a portion of the living subject.

35. The blood-pressure measurement system of claim 34, wherein the constriction device comprises:

a cuff wrapable around the portion of the living subject that applies a constriction pressure to the portion of the living subject when the cuff is wrapped around the portion of the living subject; and

a cuff-pressure regulating circuit that controls the constriction pressure applied by the cuff to the portion of the living subject, the cuff pressure regulating circuit changing the constriction pressure applied by the cuff to the portion of the living subject during an oscillometric-blood-pressure measurement.

36. The blood-pressure measurement system of claim 35, wherein the quality-assurance and data checking circuit initiates a new oscillometric blood-pressure measurement when a cuff deflation rate exceeds a predetermined value.

37. The blood-pressure measurement system of claim 27, wherein the first pulse-wave detection device comprises an electrocardiographic waveform detection device.

38. The blood-pressure measurement system of claim 37, wherein the arrhythmia-pulse-correcting circuit determines whether an oscillometric pressure pulse wave was produced by an arrhythmia based on a shape of a corresponding pulse wave detected by the electrocardiographic waveform detection device.

39. The blood-pressure measurement system of claim 27, wherein the second pulse-wave detection device comprises an oximeter sensor.

40. The blood-pressure measurement system of claim 39, wherein the oximeter sensor comprises a photoelectric pulse-wave detector.

41. The blood-pressure measurement system of claim 39, wherein the quality-assurance and data checking circuit initiates a new oscillometric-blood-pressure measurement when an error signal is received from the oximeter sensor.

42. The blood-pressure measurement system of claim 27, wherein the blood-pressure/pulse-wave-propagation-information relationship determining circuit determines a relationship between the time differences determined by the pulse-wave-propagation information obtaining circuit and a systolic blood pressure of the living subject.

43. The blood-pressure measurement system of claim 27, wherein the pulse-wave-propagation information obtaining circuit determines pulse wave propagation rates from the determined time differences, and the blood-pressure/pulse-wave-propagation-information relationship determining circuit determines a relationship between the pulse wave propagation rates determined by the pulse-wave-propagation information obtaining circuit and a blood pressure of the living subject.

44. The blood-pressure measurement system of claim 43, wherein the blood-pressure/pulse-wave-propagation-information relationship determining circuit determines a relationship between the pulse wave propagation rates determined by the pulse-wave-propagation information obtaining circuit and a systolic blood pressure of the living subject.

45. The blood-pressure measurement system of claim 27, wherein the oscillometric-systolic-pressure correcting circuit identifies a pulse wave that was used by the blood-pressure measuring circuit to determine a diastolic blood pressure of the living subject and, when the estimated systolic blood pressure of the living subject changes by a predetermined amount during the oscillometric-blood-pressure measurement, displays an estimated systolic blood pressure for the pulse wave from which the diastolic blood pressure was determined.

46. The blood-pressure measurement system of claim 27, further comprising:

a pulse-period measuring circuit that determines a pulse period based on a time difference between predetermined periodic points on two successive pulse waves detected by the first pulse-wave detection device; and

a pulse-wave-area determining circuit that determines a pulse-wave area for each pulse wave detected by the second pulse-wave detection device.

47. The blood-pressure measurement system of claim 46, wherein the blood-pressure-measurement starting circuit comprises:

a pulse-period-abnormality judging circuit that determines whether a pulse-period determined by the pulse-period measuring circuit is normal or abnormal;

a pulse-wave-area-abnormality judging circuit that determines whether a pulse-wave area determined by the pulse-wave-area determining circuit is normal or abnormal; and

an estimated-blood-pressure-abnormality judging circuit that determines whether an estimated blood pressure determined by the estimated-blood-pressure determining circuit is normal or abnormal.

48. The blood-pressure measurement system of claim 47, wherein the arrhythmia-pulse correcting circuit determines whether an oscillometric pressure pulse wave is produced by an arrhythmia or a motion artifact based on the determinations by the pulse-period-abnormality judging circuit and the pulse-wave-area-abnormality judging circuit.