Electronic sphygmomanometer and method for measuring blood pressure

• US 6,228,036 B1
• Filed: 02/15/2000
• Issued: 05/08/2001
• Est. Priority Date: 07/17/1998
• Status: Expired due to Term

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Nakanishi, Takashi
• Primary Examiner(s): O'Connor, Cary
• Assistant Examiner(s): CARTER, RYAN CHRISTOPHER
• Application Number:
  US09/500,990
• Time in Patent Office: 448 Days
• Field of Search: 600/481, 600/490, 600/491, 600/493-496, 600/499, 600/502, 600/310, 600/473, 600/477
• US Class Current: 600/491
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds

Abstract

The present invention is directed to an electronic sphygmomanometer for determining a blood pressure depending on variation in pulse wave amplitude variation waveform and cuff pressure formed by variation in the amplitude of the pulse wave, comprising: detecting the pulse wave amplitude and cuff pressure when the pulse wave exceeds a first threshold to define a first threshold; detecting the pulse wave amplitude and cuff pressure when the pulse wave exceeds a second cuff pressure to define a second point; and then, calculating a pulse wave amplitude linear equation for connecting the first and the second points to obtain a systolic blood pressure value.

According to the invention, the electronic sphygmomanometer is capable of precisely measuring a blood pressure even if dispersion occurs in pulse wave amplitude depending on how to mount the cuff or even if there is certain distortion in pulse wave depending on the physical conditions of a subject.

Claims

1. An electronic sphygmomanometer comprising a cuff for applying a pressure to blood vessels;

cuff pressure adjusting means for adjusting a pressure in the cuff;

pressure signal converting means for outputting as a pressure signal the cuff internal pressure appeared when the pressure applied to the blood vessels is depressurized by means of the cuff pressure adjusting means;

pulse wave detecting means for detecting a pulse wave from said pressure signal;

cuff pressure detecting means for detecting the pressure in the cuff from said pressure signal; and

blood pressure determining means for determining the pressure in said cuff and the blood pressure from blood said pulse wave, said electronic sphygmomanometer meter being characterized in that said blood pressure determining means comprises;

first pulse wave detecting means for detecting as a first pulse wave amplitude value a pulse wave amplitude firstly exceeding a first threshold from among said pulse waves;

second pulse wave detecting means for detecting as a second pulse wave amplitude value a pulse wave amplitude firstly exceeding a second threshold;

first cuff pressure detecting means for detecting a first cuff pressure value when said first pulse wave amplitude value is detected;

second cuff pressure detecting means for detecting a second cuff pressure value when said second pulse wave amplitude value is detected;

a linear equation calculating means of the pulse wave amplitude for linearly equating a relationship between a cuff pressure and a pulse wave amplitude based on said first pulse wave amplitude value, said second pulse wave amplitude value, said first cuff pressure value, and said second cuff pressure value; and

a blood pressure calculating means for obtaining a systolic blood pressure value from a linear equation of pulse wave amplitude.

2. An electronic sphygmomanometer according to claim 1, characterized in that said first threshold is 0% to 50% of the maximum pulse wave amplitude value.

3. An electronic sphygmomanometer according to claim 1, characterized in that said second threshold is 80% to 100% of the maximum pulse wave amplitude value.

4. An electronic sphygmomanometer according to claim 1 characterized in that said first pulse wave detecting means detects as a third pulse wave amplitude value a pulse wave amplitude which firstly becomes lower than a third threshold value;

said second pulse wave detecting means detects as a fourth pulse wave amplitude value a amplitude which becomes firstly lower than a fourth threshold;

said first cuff pressure detecting means detects a third cuff pressure a cuff pressure when said third pulse wave amplitude value is detected;

said second cuff pressure detecting means detects as a fourth cuff pressure a cuff pressure when said fourth pulse wave amplitude value is detected;

said linear equation calculating means of the pulse wave amplitude linearly equates a relationship between the cuff pressure and the pulse wave amplitude from said third pulse wave amplitude value, said fourth pulse wave amplitude value, said third cuff pressure value, and said fourth cuff pressure value; and

said blood pressure calculating means obtains a diastolic blood pressure value from the pulse wave amplitude linear equation.

5. An electronic sphygmomanometer according to claim 4, characterized in that said third threshold is 0% to 50% of the maximum pulse wave amplitude linear equation.

6. An electronic sphygmomanometer according to claim 4, characterized in that said threshold is 80% to 100% of the maximum pulse wave amplitude value.

7. An electronic sphygmomanometer according to claim 1, characterized in that said pulse wave amplitude linear equation is used, thereby to substitute the pulse wave amplitude of a constant ratio for the maximum amplitude pulse wave value and determine a blood pressure value.

8. An electronic sphygmomanometer according to claims 1, characterized in that said blood pressure value calculating means uses said pulse wave amplitude linear equation, thereby to change a ratio for the maxim um amplitude for determining a blood pressure value for the maximum amplitude value based on pulse wave data.

9. A blood pressure measuring method for determining a blood pressure depending on variation in a pulse wave amplitude variation waveform and a cuff pressure formed by variation in the amplitude of the pulse wave, said blood pressure measuring method characterized by comprising:

detecting the pulse wave amplitude and cuff pressure when said pulse wave exceeds a first threshold to define a first point, and detecting the pulse wave amplitude and cuff pressure when said pulse wave exceeds a second threshold to define a second point; and

then, calculating a pulse wave amplitude linear equation for connecting the first and the second points to obtain a systolic blood pressure value based on the pulse wave amplitude linear equation.

10. A blood pressure measuring method for determining a blood pressure depending on variation in the pulse wave amplitude variation waveform and cuff pressure formed by variation in the amplitude of the pulse wave, said blood pressure measuring method characterized by comprising:

detecting the pulse wave amplitude and cuff pressure when said pulse wave becomes lower than a third threshold to define a third point, and detecting the pulse wave amplitude and cuff pressure when said pulse wave becomes lower than a fourth threshold to define a fourth point; and

then, calculating a pulse wave amplitude linear equation for connecting the third and fourth points to obtain a diastolic blood pressure value based on the pulse wave amplitude linear equation.