Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-08-19
2002-01-01
O'Connor, Cary (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
Reexamination Certificate
active
06334850
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of detecting pulse wave, a method of detecting an artery position, and a pulse wave detecting apparatus, which enable a stable detection of the pulse wave irrespective of the operational level of an operator and are suitable for detecting a pulse waveform according to blood flow through an artery or blood vessels around the artery.
BACKGROUND ART
As one of the pulse wave detecting apparatuses, a device which detects the pulse wave of a radial artery is known. This device detects changes in pressure to the skin near the radial artery using a pressure sensor, thereby measuring the pulse wave. Since the device detects the change in the pressure applied to the sensor which is placed on the skin above the radial artery, a pressing force of 30 mmHg to 80 mmHg is required in order to stably detect the pulse wave. This causes a strong constrictive feeling in the subject.
For example, in U.S. Pat. No. 4,951,679, a pressure sensor placed near the radial artery is pressed against the arm while varying the pressing force in sequence to detect the pressing force with the maximum amplitude of a detected signal. The pulse wave is detected with this pressing force. This allows an optimum pressing force to be set without applying unnecessary pressure. However, it is necessary to apply a predetermined pressure against the arm, thereby leaving the problem of a strong constrictive feeling.
On the contrary, some pulse wave detecting apparatuses utilizing ultrasound or light (such as infrared radiation and laser beams) do not require a strong pressing force. In a pulse wave detecting apparatus which uses a reflected wave of ultrasound, a probe that emits ultrasound is applied to the arm of a subject from the outer side and the probe receives the ultrasound reflected by an artery or the like to measure the pulse wave.
On the other hand, a pulse wave detecting apparatus which uses light emits a light from a light emitting diode, for example, to the inside of a body to detect the amount of reflected light (reflected light from subcutaneous tissues). Since part of the light emitted from the light emitting diode is absorbed by hemoglobin in the blood vessels, the amount of reflected light is related to blood capacity in the blood vessels to be detected as the pulse wave.
In a conventional pulse wave detecting apparatus using ultrasound, the detected values of the reflected wave vary in accordance with angles between a probe which transmits and receives ultrasound and blood flow. In the operation of the probe, it is difficult to maintain a fixed angle to the blood flow, thereby causing difficulty in stable measurement of the pulse wave. For example, in the case where the probe is applied to the palm side of a subject's arm, the detection of the pulse wave becomes difficult if the probe shifts only by several millimeters from an artery. In the case where the probe is applied to the backhand side of the subject's arm, a signal-to-noise (SN) ratio necessary for detecting the pulse wave can not be secured.
In a device utilizing a laser or light-emitting diode, if irradiating light is not applied to the artery, the SN ratio necessary for detecting the pulse waveform can not be secured or stable pulse waveform can not be detected.
Conventionally, the pulse waveform has been detected based on the blood flowing in the artery. According to traditional Oriental medicine, it is believed that the conditions of a living body can be monitored based on the pulse waveform. The artery formed of smooth muscles and the like supplies blood to the peripheral tissues by the pulsation. Since the artery is a tissue of the living body, it is necessary to provide the artery with blood. The arteriole supplies blood to the arterial tissues. Since the arteriole supplies blood to the artery itself, the condition of the artery can be monitored by detecting the pulse waveform based on the blood flow of the arteriole. However, in conventional methods for detecting pulse waves, the pulse waveform has been detected based on the blood flowing in the artery, but the pulse waveform based on blood flowing in the arteriole has not been detected.
The present invention has been achieved to solve the above-described problems. An object of the present invention is to provide a method of detecting a pulse wave, a method of detecting an artery position, and a pulse wave detecting apparatus, which enable stable detection of the pulse wave independent of the skill level of an operator without forcing a strong constrictive feeling on the subject, and are suitable for detecting the pulse waveform according to blood flow through an artery or blood vessels around the artery.
DISCLOSURE OF THE INVENTION
(1) A method of detecting a pulse wave according to the present invention, uses a pulse wave detection means which detects a pulse waveform of blood flowing through blood vessels around an artery, and the method comprises steps of:
detecting the pulse waveform by the pulse wave detection means at a plurality of positions;
sensing a polarity of the pulse waveform detected by the pulse wave detection means; and
detecting the pulse waveform detected in a position range from a position where the polarity is inverted to a position where the polarity is returned to an original polarity as the pulse waveform from the blood vessels around the artery.
According to the present invention, the polarity of the pulse waveform in the blood vessels around an artery is sensed, the pulse waveform being detected at a plurality of positions and the pulse waveform in the blood vessels around the artery are detected in a position range from a position where the polarity is inverted to a position where the polarity is returned to the original polarity, that is, in the position range in which the polarity inversion resulting from the compression due to the artery is observed. This allows the pulse waveform from blood flowing through the arteriole, which is the blood vessel surrounding the artery, to be reliably detected with a high signal-to-noise ratio.
(2) A method of detecting a pulse wave according to the present invention, comprises steps of:
detecting a pulse waveform by a pulse wave detection means which detects the pulse waveform from blood flowing through blood vessels around an artery at a plurality of detection positions;
sensing a polarity of the pulse waveform detected by the pulse wave detection means; and
detecting the pulse wave of the artery positioned approximately at a center of the blood vessels around the artery in a position range from a position where the polarity is inverted to a position where the polarity is returned to an original polarity.
According to the present invention, the polarity of the pulse waveform in the blood vessels around an artery is sensed, the pulse waveform being detected at a plurality of positions and the pulse waveform in the artery positioned approximately at the center of the blood vessels around the artery are detected in a position range from a position where the polarity is inverted to a position where the polarity is returned to the original polarity, that is, in the position range in which the polarity inversion resulting from the compression due to the artery is observed. This allows the pulse wave of the artery to be detected at the accurately specified position, so that the pulse waveform of the artery can be reliably detected with a high signal-to-noise ratio.
(3) A method of detecting a position of an artery according to the present invention, using a pulse wave detection means which detects a pulse waveform of blood flowing through blood vessels around the artery, comprises the steps of:
detecting the pulse waveform by the pulse wave detection means at a plurality of positions;
sensing a polarity of the pulse waveform detected by the pulse wave detection means; and
detecting the location of the artery in a position range from a position where the polarity is inverted or is in the process of being inverted to a position where the polarity is returned t
Amano Kazuhiko
Ishiyama Hitoshi
Uebaba Kazuo
Natnithithadha Navin
O'Connor Cary
Seiko Epson Corporation
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