Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-04-26
2004-07-06
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S459000
Reexamination Certificate
active
06758816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a pulse wave detector, and more specifically, to a pulse wave detector for detecting pulse waves by sending and receiving ultrasonic waves to and from an artery.
2. Related Art
Detection of pulse waves caused by blood flow through an artery is widely used in cases such as medical institutions and healthcare administration. This pulse wave detection is also widely used for automatic electronic detection of pulse rate etc., as well as for detecting pulse rate at a specified time by touching an artery with a finger.
As a device for obtaining pulse rate by electronically detecting pulse waves, devices currently exist that have a piezoelectric element arranged on an artery and pulse rate is detected from pressure variations on the skin (positional variations of the skin caused by pressure) accompanying pressure variations inside the artery, or which use ultrasonic waves to detect pulse rate.
Japanese patent laid-open No. Hei. 1-214335 and U.S. Pat. No. 4,086,916, for example, propose use of the Doppler effect caused by blood flow, as a pulse wave detector that uses ultrasonic waves.
FIG. 10
shows the appearance of frequency variations of ultrasonic waves due to this Doppler effect.
If an ultrasonic wave as shown in
FIG. 10A
having frequency f
0
is transmitted from a body surface towards an artery, the transmitted ultrasonic wave is reflected by blood flowing in the artery. If this reflected wave is received by a receiver it is possible to detect variations in the frequency of the reflected wave. Specifically, if the frequency of a received wave is made f
1
, since the blood flow velocity in the artery is fast in the systolic phase of the heart, the frequency of the reflected wave becomes higher due to the Doppler effect (A part), while conversely the frequency becomes lower than the A part during relaxation of the heart (B part) since the blood flow velocity is lower, as shown in FIG.
10
B.
In this way, ultrasonic waves are directed to blood flow in an artery that changes in flow velocity due to beating of the heart, and pulse waves are detected by detecting frequency variation, and it is also possible to detect pulse rate and blood flow velocity.
Also, in German Patent publication No. 3345739 there is proposed a pulse wave detector that uses a plurality of sensors (a plurality of groups of sensors), and
FIG. 11
shows the arrangement of a sensor in this type of pulse rate detector. A transmitter
11
a
and a receiver
21
a
inside a sensor
19
a
are rectangular in shape. The longer side of each rectangle is arranged so that it is parallel to blood flow in an artery
2
, and so that a line connecting the transmitter
11
a
and the receiver
21
a
is orthogonal to the artery
2
.
However, with pulse wave detectors for detecting pulse waves using ultrasonic wave Doppler effects, as in the inventions disclosed in Japanese Patent laid-open No. Hei. 1-214335 and U.S. Pat. No. 4,086,916, there is a problem that power consumption is extremely large because ultrasonic waves are used.
As a result, the pulse wave detectors of the related art must be used in an environment such as a hospital or a house where electric power can be adequately supplied, and there is a problem that when they are used in any other environment ultrasonic waves can only be measured for a short time.
Particularly, in the case of a pulse wave detector that is of such a size and weight as to be portable, for instance a pulse wave detector built into a wristwatch, since the battery capacity is limited there is a problem that usage time is made even shorter.
Also, the ultrasonic waves f
0
transmitted for pulse wave detection are progressive waves in the order of a few MHz. This means that with a pulse wave detector, such as the invention disclosed in German patent publication No. 3345739, having a long side of a transmitter
11
a
and receiver
21
a
arranged parallel to the blood flow of an artery
2
, it is necessary to accurately transmit the ultrasonic waves f
0
toward the artery
2
, and it is difficult to align the position of the sensor
19
a.
Also, even if the positional alignment is performed accurately, there is a problem that it becomes impossible to measure ultrasonic waves due to positional variations in the artery
2
and the sensor
19
with movement of the wrist
2
a.
SUMMARY OF THE INVENTION
The present invention has been conceived in order to solve the above described problems, and a first object of the invention is to provide a pulse wave detector that can detect pulse waves with low power consumption, and which is capable of prolonging usage time.
A second object of the present invention is to provide a pulse wave detector that enables simple alignment of a sensor with an artery, and is capable of carrying out pulse wave detection even when there is wrist movement.
A pulse wave detector of the present invention comprises a transmitter for transmitting ultrasonic waves toward an artery, a receiver for receiving ultrasonic waves transmitted from the transmitter and reflected by blood flowing in the artery, a drive controller for intermittently driving at least one of the transmitter and the receiver, a pulse wave information acquisition unit for acquiring pulse wave information relating to pulse waves from the ultrasonic waves received by the receiver, and an output unit for outputting the pulse wave information acquired by the pulse wave information acquisition unit.
By intermittently driving at least one of the transmitter or the receiver in this way, it is possible to suppress the power consumption to the drive duty cycle. Specifically, a pulse wave detector has low power consumption. For example, by building the pulse wave detector into a watch, it is possible to routinely prolong usage. In this case, it is possible to utilize part or all of an oscillator section used in the watch as the drive controller of the present invention, and in this way an even simpler construction is made possible.
With the pulse wave detector of the present invention, it is possible for the pulse wave information acquisition unit to be provided with a memory for storing pulse wave information, and for the output unit to output the pulse wave information stored in the memory. Specifically, pulse rate information and detection information for specified time sections are stored in the memory in advance, and can be used for medical diagnosis by outputting to an external device such as a medical diagnostic machine.
With the pulse wave detector of the present invention, it is also possible for the pulse wave acquisition unit to acquire a pulse rate from the detection signal as pulse wave information, and for the output unit to output the pulse rate acquired by the pulse wave information acquisition unit. In this way, it is possible to routinely confirm a pulse under normal conditions.
The pulse wave detector of the present invention may also be provided with a display, and it is possible for the pulse wave information acquisition unit to acquire a pulse rate or pulse wave waveform as information relating to a pulse wave from the detection signal, and for the output unit to output the pulse rate or pulse wave waveform acquired by the pulse wave information unit to the display. In this way, by displaying the pulse rate or the pulse wave waveform, it is possible to easily confirm the pulse rate or pulse wave form even during normal day to day activities.
According to another aspect of a pulse wave detector of the present invention, the pulse wave information acquisition unit has a frequency detector for detecting frequency variations of the ultrasonic waves received by the receiver, and pulse wave information is acquired from a detection signal from the frequency detector.
In the pulse wave detector of the present invention, the drive controller intermittently drives both the transmitter and the receiver, and varies the drive timing of the transmitter and the drive means of the receiver. By intermittently driving both the transmitter and th
Kamimoto Takashi
Nakamura Chiaki
Odagiri Hiroshi
Sakumoto Kazumi
Shinogi Masataka
Adams & Wilks
Jaworski Francis J.
Patel Maulin
Seiko Instruments Inc.
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