Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-01-31
2001-11-13
Lacyk, John P. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S490000, C600S494000
Reexamination Certificate
active
06315734
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for obtaining an information relating to a propagation velocity of a pulse wave which propagates through an artery of a living subject, for example, a pulse-wave propagation time or a pulse-wave propagation velocity.
2. Related Art Statement
There have been proposed various pulse-wave propagation information obtaining apparatuses for obtaining an information relating to a propagation velocity of a pulse wave which propagates through an artery of a living subject. The pulse-wave propagation information is used for estimating a blood pressure, a degree of an arterial sclerosis, or a peripheral resistance of the subject, or the like.
The pulse-wave propagation information includes a pulse-wave propagation velocity and/or a pulse-wave propagation time. Since the pulse-wave propagation velocity is determined by dividing a propagation path (distance) through which the pulse wave propagates by the pulse-wave propagation time, it is needed to determine the pulse-wave propagation time. The pulse-wave propagation time is determined as follows: First, a first and a second signal detecting device are worn on a first and a second portion of the subject, respectively, and detect a first signal produced in synchronism with a heart beat of the subject and a second signal produced in synchronism with the heart beat of the subject, respectively. Then, a time difference between a time when the first signal is detected and a time when the second signal is detected is determined. The time difference is defined as the pulse-wave propagation time.
For example, a phonocardiographic transducer worn on a chest of the subject is employed as the first signal detecting device, and a second heart sound II detected by the phonocardiographic transducer is employed as the first signal. A carotid pulse sensor worn on a cervix of the subject is employed as the second signal detecting device, and a notch of a carotid pulse wave detected in synchronism with the detected second heart II by the carotid pulse sensor is employed as the second signal. The notch of the carotid pulse wave is defined as a point at which the amplitude of the carotid pulse wave (i.e., the intensity of the second signal) starts increasing after decreasing from the maximum amplitude of the carotid pulse wave. A time difference between a time when the second heart sound II is detected and a time when the notch of the carotid pulse wave is detected is determined as the pulse-wave propagation time. It is generally understood that the pulse-wave propagation time determined based on the second heart sound II and the notch of the carotid pulse wave is suitable for evaluating a pulse-wave propagation time of a central portion of the subject. The carotid pulse sensor for detecting the carotid pulse wave is disclosed in Laid-Open Publication No. 10-146322 of unexamined Japanese Patent Application.
However, it needs a great skill to wear the carotid pulse sensor on an appropriate portion of the cervix of the subject. If the carotid pulse sensor is not worn on the appropriate portion of the cervix of the subject, an accurate carotid pulse wave may not be detected, so that an incorrect notch of the carotid pulse wave may be detected. Therefore, an accurate pulse-wave propagation time may not be determined.
Moreover, in the case where a pulse-wave detecting device worn on a different portion of the subject than the cervix is employed in place of the carotid pulse sensor, a notch of the detected pulse wave may be employed as the second signal. However, if the notch of the pulse wave is obscure, a time when the notch is detected can not be determined accurately. Therefore, an accurate pulse-wave propagation time can not be determined.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a pulse-wave propagation information obtaining apparatus which can obtain an accurate information relating to a propagation velocity of a pulse wave which propagates through an artery of a living subject.
The above object has been achieved by the present invention, which provides an apparatus for obtaining an information relating to a propagation velocity of a pulse wave which propagates through an artery of a living subject, comprising: (a) a first signal detecting device which is adapted to be worn on a first portion of the subject and which detects a first signal generated from the first portion in synchronism with a heart beat of the subject; (b) a pulse-wave detecting device which is adapted to be worn on a second portion of the subject and which detects, as a second signal, a notch of the pulse wave generated from the second portion in synchronism with the heart beat of the subject; (c) a pressing device which is adapted to be worn on a third portion of the subject to press the third portion, the third portion being on a downstream side relative to the second portion of the subject with respect to the artery and being in proximity to the second portion; and (d) pulse-wave propagation time determining means for determining, as the information, a time difference between a time when the first signal is detected by the first signal detecting device and a time when the notch of the pulse wave is detected by the pulse-wave detecting device in a state in which the third portion of the subject is pressed by the pressing device.
In the apparatus in accordance with the present invention, the pulse-wave propagation time determining means determines, as a pulse-wave propagation time, the time difference between the time when the first signal is detected by the first signal detecting device and the time when the notch of the pulse wave is detected by the pulse-wave detecting device in the state in which an artery of the subject under the pressing device is pressed by the pressing device. The pulse-wave detecting device is worn on the portion of the subject being on an upstream side relative to the pressing device with respect to the artery and being in proximity to the pressing device. In the state in which the artery is pressed by the pressing device, a notch of the pulse wave can be clearly detected by the pulse-wave detecting device located upstream of, and near to, the pressing device. Therefore, the time when the notch of the pulse wave is detected is accurately determined. Thus, the apparatus according to the present invention can accurately determine a pulse-wave propagation time based on the accurate time when the notch of the pulse wave is detected.
According to a preferred feature of the present invention, the pulse-wave detecting device comprises a brachial pulse-wave detecting device which is adapted to be worn on an upper arm of the subject and which detects a notch of a brachial pulse wave of the subject, and the pressing device comprises a first rubber bag which is adapted to be worn on the upper arm of the subject for determining a blood pressure of the subject, the apparatus further comprising: a pressure control device which changes a pressing pressure of the first rubber bag; and a blood pressure determining device which determines the blood pressure of the subject, based on signals successively detected while the pressing pressure of the first rubber bag is changed by the pressure control device. In this case, the pulse-wave propagation information obtaining apparatus can determine the blood pressure of the subject in addition to the information relating to the propagation velocity of the pulse wave.
According to another feature of the present invention, the brachial pulse-wave detecting device comprises a second rubber bag for detecting the brachial pulse wave of the subject, the second rubber bag is adapted to be worn on an upstream side relative to a portion of the upper arm on which the first rubber bag is worn, and the apparatus further comprises an outer bag in which the first and second rubber bags are accommodated in a state in which the first and second rubber bags are spaced from each other. Thus, since only the outer
Colin Corporation
Lacyk John P.
Natnithithadha Navin
Oliff & Berridg,e PLC
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