System and method for correcting a living subject's measured blood pressure

• US 5,895,359 A
• Filed: 06/06/1997
• Issued: 04/20/1999
• 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): Getzow, Scott M.
• Application Number:
  US08/870,456
• Time in Patent Office: 683 Days
• Field of Search: 600/490, 600/491, 600/492, 600/493, 600/494, 600/495, 600/496, 600/500
• 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 system and method for correcting a living subject'"'"'s measured blood pressure when the living subject'"'"'s actual blood pressure changes during an oscillometric blood pressure measurement detects oscillometric pressure pulse waves produced by a cardiac muscle of the living subject, measures a blood pressure of the living subject based on the amplitudes of the oscillometric pressure pulse waves, and corrects the measured blood pressure when the living subject'"'"'s blood pressure changes during the blood pressure measurement. The system and method of this invention preferably determine an estimated blood pressure of the living subject, monitor the estimated blood pressure, and determine that the living subject'"'"'s blood pressure changed during the blood pressure measurement when the estimated blood pressure changes by a predetermined amount during the blood pressure measurement. When the living subject'"'"'s blood pressure is determined to have changed during the blood pressure measurement, the system and method of this invention display an estimated systolic blood pressure for the time at which the living subject'"'"'s diastolic blood pressure was measured.

Claims

1. A system for correcting a living subject'"'"'s measured blood pressure when the living subject'"'"'s actual blood pressure changes during an oscillometric blood-pressure measurement, comprising:

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

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

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

2. The 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.

3. The system of claim 2, wherein the constriction device comprises:

a cuff wrapable around the portion of the living subject and capable of applying 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.

4. The 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;

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 the pulse waves detected by the first pulse-wave detection device and predetermined periodic points on the 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.

5. The system of claim 4, wherein the first pulse-wave detection device comprises an electrocardiographic waveform detection device.

6. The system of claim 4, wherein the second pulse-wave detection device comprises an oximeter sensor.

7. The system of claim 6, wherein the oximeter sensor comprises a photoelectric pulse-wave detector.

8. The system of claim 4, wherein, 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.

9. The system of claim 4, 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.

10. The system of claim 4, wherein the pulse-wave-propagation information obtaining circuit further determines pulse wave propagation rates from the determined time differences, and the blood-pressure/pulse-wave-propagation-information relationship determining circuit further 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.

11. The system of claim 10, wherein the blood pressure of the living subject is a systolic blood pressure of the living subject.

12. A method of correcting a living subject'"'"'s measured blood-pressure when the living subject'"'"'s actual blood-pressure changes during an oscillometric blood-pressure measurement, comprising:

measuring a blood pressure of a living subject;

determining whether the living subject'"'"'s blood pressure changed during the blood pressure measurement; and

correcting the measured blood pressure when it is determined that the living subject'"'"'s blood pressure changed during the blood pressure measurement, wherein, correcting the measured blood pressure comprises identifying a pulse wave used to determine a diastolic blood pressure of the living subject.

13. The method of claim 12, wherein measuring the living subject'"'"'s blood pressure comprises:

detecting oscillometric pressure pulse waves from a first portion of the living subject; and

measuring the living subject'"'"'s blood pressure based on amplitudes of the oscillometric pressure pulse waves.

14. The method of claim 13, wherein determining whether the living subject'"'"'s blood pressure changed during the blood pressure measurement comprises:

detecting first pulse waves from a second portion of the living subject;

detecting second pulse waves from a third portion of the living subject;

determining time differences between predetermined periodic points on the first pulse waves detected from the second portion of the living subject and predetermined periodic points on corresponding ones of the second pulse waves detected from the third portion of the living subject;

determining a relationship between the determined time differences and the living subject'"'"'s blood pressure;

determining an estimated blood pressure of the living subject based on the determined relationship;

determining that the living subject'"'"'s blood pressure has changed when the estimated blood pressure of the living subject changes by a predetermined amount.

15. The method of claim 14, wherein correcting the measured blood pressure further comprises:

displaying an estimated systolic blood pressure for the pulse wave from which the diastolic blood pressure was determined.

16. The method of claim 14, wherein detecting first pulse waves from a second portion of the living subject comprises detecting an electrocardiographic waveform from a second portion of the living subject.

17. The method of claim 14, wherein detecting second pulse waves from a third portion of the living subject comprises detecting a plethysmographic pulse wave from a third portion of the living subject.

18. The method of claim 14, wherein determining a relationship between the determined time differences and the living subject'"'"'s blood pressure comprises determining a relationship between the determined time differences and the living subject'"'"'s systolic blood pressure.

19. The method of claim 14, wherein determining a relationship between the determined time differences and the living subject'"'"'s blood pressure comprises:

determining pulse wave propagation rates from the determined time differences;

determining a relationship between the determined pulse wave propagation rates and the living subject'"'"'s blood pressure.

20. The method of claim 19, wherein determining a relationship between the determined pulse wave propagation rates and the living subject'"'"'s blood pressure comprises determining a relationship between the determined pulse wave propagation rates and the living subject'"'"'s systolic blood pressure.