Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-12-30
2002-04-09
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S494000, C600S500000, C600S504000
Reexamination Certificate
active
06368282
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring the velocity of propagation of a pulse wave which is propagated through an artery of a living subject.
2. Related Art Statement
The blood pressure, degree of arterial sclerosis, peripheral resistance, etc. of a living subject can be estimated based on the velocity of propagation of a pulse wave which is propagated through an artery of the subject. There is known a pulse-wave propagation velocity measuring apparatus including a pair of pulse-wave sensors which are put on different locations on the skin of a living subject to press different portions of an artery of the subject via the skin and detect respective pulse waves from the artery. The measuring apparatus determines a pulse-wave propagation velocity based on the phase difference of the two pulse waves detected through the two sensors. The measuring apparatus is disclosed in, e.g., Unexamined Japanese Patent Application laid open for inspection purposes under Publication No. 60(1985)-220037.
The prior measuring apparatus measures the pulse-wave propagation velocity through the pulse-wave sensors being pressed against two portions of a superficial artery, such as carotid artery, radial artery, or dorsal pedal artery, that is adjacent to the skin of the subject. In this case, however, the time difference between the time of occurrence or detection of a heartbeat-synchronous pulse of one of the two pulses waves and the time of occurrence or detection of a corresponding heartbeat-synchronous pulse of the other pulse wave is small, because the length or distance between the two portions of the superficial artery is short. Thus, the time difference may not be relied upon for providing a very accurate pulse-wave propagation velocity.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for measuring a very accurate pulse-wave propagation velocity.
The above object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for measuring a propagation velocity of a pulse wave which is propagated through an artery of a living subject, the apparatus comprising an electrocardiographic-waveform detecting device which detects an electrocardiographic waveform from the subject, a pulse-wave sensor which is adapted to be worn on the subject and which detects the pulse wave from the subject, time-difference determining means for determining a time difference between a first periodic point relating to the detected electrocardiographic waveform and a second periodic point relating to the detected pulse wave, and propagation-velocity determining means for determining the propagation velocity of the pulse wave based on the determined time difference.
In the pulse-wave measuring apparatus in accordance with the first aspect of the invention, the time difference determined by the time-difference determining means contains a time duration when the pulse wave is propagated through the aorta directly connected to the heart of the subject. Therefore, the length of the artery through which the pulse wave is propagated is increased and accordingly the time difference is increased. In addition, since the diameter of the aorta is large and accordingly the velocity of the pulse wave being propagated through the aorta is decreased, the time difference is increased. Thus, the present apparatus provides a very accurate pulse-wave propagation velocity. Therefore, the degree of arterial sclerosis, or the blood pressure, of the subject can be estimated with high accuracy based on the thus determined pulse-wave propagation velocity.
According to a preferred feature of the first aspect of the invention, the pulse-wave sensor comprises a pressure sensor which is adapted to be pressed against a portion of the artery of the subject via a skin of the subject and which detects, as the pulse wave, a heartbeat-synchronous pressure oscillation which is transmitted thereto from the portion of the artery via the skin. In the case where the present invention is applied to a BP monitor apparatus including an identical pressure sensor for monitoring BP values of a subject, the pressure sensor is used for the two purposes, one for detecting a pulse wave and thereby measuring a pulse-wave propagation velocity and the other for monitoring BP values. The BP monitor apparatus having the pulse-wave propagation velocity measuring function enjoys a reduced production cost.
According to another feature of the first aspect of the invention, the pulse-wave sensor comprises an inflatable cuff which is adapted to be wound around a body portion of the subject, and a pressure sensor which detects, as the pulse wave, a heartbeat-synchronous pressure oscillation which is produced in the cuff. In the case where the present invention is applied to a BP measuring apparatus including identical cuff and pressure sensor for measuring a BP value of a subject, the cuff and pressure sensor are used for the two purposes, one for detecting a pulse wave and thereby measuring a pulse-wave propagation velocity and the other for measuring a BP value. The BP measuring apparatus having the pulse-wave propagation velocity measuring function enjoys a reduced production cost.
According to another feature of the first aspect of the invention, the pulse-wave sensor comprises a photoelectric sensor including a light source which emits a light toward a body portion of the subject, and a light detecting element which detects the light transmitted through, or reflected from, the body portion. In the case where the present invention is applied to a blood-oxygen-saturation measuring apparatus (e.g., so-called pulse oximeter) having an identical photoelectric sensor for measuring a blood oxygen saturation of a subject, the photoelectric sensor is used for the two purposes, one for detecting a pulse wave and thereby measuring a pulse-wave propagation velocity and the other for measuring a blood oxygen saturation. The oxygen-saturation measuring apparatus having the pulse-wave propagation velocity measuring function enjoys a reduced production cost.
According to a second aspect of the present invention, there is provided an apparatus for measuring a propagation velocity of a pulse wave which is propagated through an artery of a living subject, the apparatus comprising a blood-pressure measuring device which measures a blood pressure value of the subject, an electrocardiographic-waveform detecting device which includes a plurality of electrodes adapted to contact a body surface of the subject and which detects an electrocardiographic waveform from the subject through the electrodes, a pulse-wave sensor which is adapted to be worn on the subject and which detects the pulse wave from the subject, time-difference determining means for determining a time difference between a first periodic point relating to the detected electrocardiographic waveform and a second periodic point relating to the detected pulse wave, propagation-velocity determining means for determining the propagation velocity of the pulse wave based on the determined time difference, and propagation-velocity modifying means for modifying the determined propagation-velocity value to a modified propagation-velocity value corresponding to a predetermined blood pressure value, based on the measured blood pressure value, according to a predetermined relationship between modified propagation velocity, and determined propagation velocity and measured blood pressure.
While the pulse-wave propagation velocity is influenced by the degree of arterial sclerosis, it is also influenced by the blood pressure and/or the pulse rate of the subject. However, the blood pressure (BP) values of the subject will change more or less in different measurements. Therefore, the propagation velocity measured by the prior apparatus may not directly be used as an index indicative of a degree of arterial sclerosis. In the pulse-wave propagation velocity measuring
Ikawa Tomoko
Inukai Hidekatsu
Nomura Takashi
Ogura Toshihiko
Oka Tohru
Colin Corporation
Oliff & Berridg,e PLC
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