Blood pressure monitor

• US 6,007,492 A
• Filed: 09/14/1998
• Issued: 12/28/1999
• Est. Priority Date: 10/24/1996
• Status: Expired due to Fees

• Current Assignee: Omron Healthcare Company Limited (Omron Corporation)
• Original Assignee: Colin Corporation (Fukuda Denshi Company Limited)
• Inventors: Goto, Masami, Narimatsu, Kiyoyuki, Yokozeki, Akihiro, Nishibayashi, Hideo
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/152,464
• Time in Patent Office: 470 Days
• Field of Search: 600/485, 600/490, 600/493-6, 600/500
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds

Abstract

A blood pressure monitor including a cuff, a pressure sensor which detects a pressure in the cuff, a pressure regulating device which increases the pressure of the cuff, a pulse-amplitude determining device for determining an amplitude of each of pulses of a pulse wave which are produced in the cuff and detected by the pressure sensor while the cuff pressure is increased, a candidate determining device for determining, as a diastolic BP candidate, a pressure of the cuff which is detected by the pressure sensor and which corresponds to an amplitude of a first pulse of the pulses determined by the pulse-amplitude determining device, by judging whether the amplitude of the first pulse is not greater than a reference value which is smaller than an amplitude of at least one second pulse of the pulses, by a predetermined proportion of the amplitude of the second pulse, the amplitude of the second pulse being determined by the pulse-amplitude determining device after the amplitude of the first pulse is determined, and a BP determining device for determining, as a monitor diastolic BP value, the cuff pressure corresponding to the amplitude of the first pulse, when the candidate determining device determines, as the diastolic BP candidate, the cuff pressure corresponding to the amplitude of the first pulse, with respect to a predetermined number of the one or more second pulses.

Claims

1. A blood pressure monitor comprising:

an inflatable cuff which is adapted to be wound around a body portion of a living subject to press said body portion through which an artery of the subject extends;

a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in said cuff;

a pressure pulse wave sensor which is adapted to be pressed against a distal section of said artery located on a distal side of said cuff wound around said body portion, so as to detect a pressure pulse wave which is produced from said distal section of the artery and is propagated thereto via a skin tissue above said distal section;

relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by said blood pressure measuring device and a magnitude of the pressure pulse wave detected by said pressure pulse wave sensor;

blood pressure determining means for successively determining at least a diastolic blood pressure of the subject according to the determined relationship based on a magnitude of a lower-peak point of each of successive first heartbeat-synchronous pulses of said pressure pulse wave detected by said pressure pulse wave sensor;

cuff-pressure increasing means for increasing said pressure of said cuff at a predetermined rate;

waveform-characteristic determining means for determining a characteristic of a lower-peak portion of a waveform of each of successive second heartbeat-synchronous pulses of said pressure pulse wave which are detected by said pressure pulse wave sensor when said pressure of said cuff is increased at said predetermined rate by said cuff-pressure increasing means, said lower-peak portion including a lower-peak point of said each second heartbeat-synchronous pulse; and

judging means for judging whether said determined relationship is accurate, based on at least one diastolic blood pressure determined by said blood pressure determining means and a pressure of said cuff corresponding to a time when the waveform characteristics determined by said waveform-characteristic determining means significantly largely change.

2. The blood pressure monitor according to claim 1, wherein said waveform-characteristic determining means comprises length determining means for determining, as said characteristic of said lower-peak portion of said waveform of said each second heartbeat-synchronous pulse, a length of said lower-peak portion defined by a first magnitude of said lower-peak point of said each second heartbeat-synchronous pulse and a second magnitude greater by a predetermined amount than the first magnitude.

3. The blood pressure monitor according to claim 2, wherein said judging means comprises:

first means for differentiating, with respect to time, the respective lengths of the respective lower-peak portions of the second heartbeat-synchronous pulses determined by said length determining means, and determining a time corresponding to the greatest differential, as said time when said waveform characteristics significantly largely change; and

second means for judging whether said determined relationship is accurate, based on said at least one diastolic blood pressure determined by said blood pressure determining means and said pressure of said cuff corresponding to said time corresponding to said greatest differential.

4. The blood pressure monitor according to claim 3, wherein said second means of said judging means comprises means for judging whether an absolute value of a difference between the last diastolic blood pressure determined by said blood pressure determining means and said pressure of said cuff corresponding to said time corresponding to said greatest differential, is not greater than a reference value.

5. The blood pressure monitor according to claim 4, wherein said blood pressure measuring device comprises means for measuring a diastolic blood pressure of the subject by changing said pressure in said cuff, and wherein said second means of said judging means comprises means for judging whether said absolute value of said difference is not greater than a modified reference value which is obtained by subtracting, from said reference value, a difference between the measured diastolic blood pressure and said pressure of said cuff corresponding to said time corresponding to said greatest differential.

6. The blood pressure monitor according to claim 1, wherein said blood pressure measuring device comprises periodic blood pressure measuring means for periodically measuring said blood pressure of the subject at a predetermined period, and wherein said cuff-pressure increasing means, said waveform-characteristic determining means, and said judging means are operated at said predetermined period, and said periodic blood pressure measuring means is operated when a negative judgment is made by said judging means and is not operated when a positive judgment is made by said judging means.