JP4149829B2 - Pulse wave measuring electrode and pulse wave measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode for pulse wave measurement and a pulse wave measurement device, and more particularly to an electrode for pulse wave measurement and a pulse wave measurement device that can measure a pulse wave with a simple configuration with a small burden on a subject.
[0002]
[Prior art]
Conventionally, pulse wave velocity or pulse wave velocity (PWV) is generally used as an indicator of vascular diseases such as arteriosclerosis. PWV is the speed at which the wave generated when the blood vessel wall pressure derived when pumping blood from the heart moves through the artery is transmitted through the blood vessel wall, and the higher the speed, the harder the blood vessel. PWV is obtained by measuring pulse waves at two points on a blood vessel and their propagation times, and dividing the distance between the two points by the propagation time.
[0003]
Arterial pulse waves are also used to obtain cardiac function indicators such as STI (systolic time phase). In recent years, how reflected waves from the periphery affect cardiac function, coronary artery disease, and brain disease. Whether to do is being considered.
[0004]
The pulse wave measurement method includes 1) detecting a pulse wave using a pulse wave sensor such as a pressure sensor, and 2) detecting a pulse wave of an artery by slightly pressing a subject's limb using a cuff. 3) What detects a pulse wave from the blood vessel diameter fluctuation | variation measured using the ultrasonic sensor is known.
[0005]
[Problems to be solved by the invention]
However, in the conventional pulse wave sensor, it is necessary to search for a place where the pulse touches. Moreover, in the method using a cuff, it is necessary to press the measurement site | part of a test subject in order to detect a pulse wave, and a test subject is forced. On the other hand, the method using an ultrasonic sensor has a problem that the ultrasonic sensor is expensive and the apparatus for measurement is enlarged.
[0006]
In addition, the arterial pulse wave used for cardiac function evaluation needs to faithfully reflect the internal pressure or volume pulse wave of the artery. However, the location of the sensor and the pressing force depend on the examiner. In many cases, the reproducibility of the obtained pulse waveform is a problem.
There is also a method (tonometry method) in which a part of the blood vessel is pressed until it becomes flat and the lateral pressure applied to the flattened portion of the blood vessel is measured with a multi-sensor (tonometry method), but a very large mechanism for fixing the arm And the pulse wave velocity may be affected depending on the degree to which the blood vessel is pressed.
[0007]
The present invention has been made in view of the problems of such a conventional pulse wave measuring device, and its purpose is to reduce the burden on the subject and to enable pulse volume measurement with high accuracy with a simple configuration. An object of the present invention is to provide a wave measuring device and a pulse wave measuring electrode.
[0008]
[Means for Solving the Problems]
That is, the gist of the present invention is a pulse wave measuring electrode having support means having an electrode mounting surface and a first electrode pair mounted on the electrode mounting surface, the electrode mounting surface being the first electrode pair. Each of the first pair of portions and a second pair of portions extending outward from the first pair of portions, and the first pair of portions are configured from substantially the same plane. lies in the pulse wave measurement electrode, wherein a second pair of sites are composed of surface inclined opposite and inwardly to each other with respect to the site of the first one pair, respectively.
[0009]
In such a pulse wave measurement electrode, it is preferable that the electrode mounting surface of the support means has a protrusion between the portions where the electrodes of the first electrode pair are mounted, and the protrusion touches the mounting surface in a plane. More preferably, it has a shape. If such a protrusion is provided and the electrode is attached so that the protrusion is positioned on the blood vessel to be measured, it is possible to measure the arterial volume pulse wave with higher accuracy.
[0010]
Furthermore, it is preferable to have a second electrode pair composed of electrodes provided on each of the inclined surfaces, and it is particularly preferable that the width of the second electrode pair is narrower than the width of the first electrode pair and the protrusion. With such a configuration, the current flowing between the second electrode pair flows in a concentrated manner in the tissues and blood vessels under the protrusions, thereby enabling highly accurate pulse wave measurement.
[0011]
Further, another gist of the present invention is that the pulse wave measurement electrode of the present invention and the pulse wave measurement electrode are mounted on a living body, and are mounted on the living body at a position sandwiching the first electrode pair . Three electrode pairs, a constant current supply means for supplying a predetermined constant current between the third electrode pairs, and a pulse wave acquisition means for acquiring a voltage waveform representing a change in bioimpedance from the first electrode pair as a pulse wave It exists in the pulse-wave measuring device characterized by having.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
■ (First embodiment)
Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings.
■ (Configuration of pulse wave measuring device)
FIG. 1 is a block diagram illustrating a configuration example of a pulse wave measurement device according to an embodiment of the present invention.
In the figure, reference numeral 10 denotes an arithmetic control unit that controls the overall control of the pulse wave measuring device according to the present embodiment. The arithmetic control unit includes a CPU, a ROM, a RAM, and the like (not shown). For example, the CPU executes a program stored in the ROM. Control of the entire apparatus including measurement processing described later is executed.
[0013]
The arithmetic control unit 10 can obtain a pulse wave from the bioelectrical impedance value measured by the impedance conversion unit 50. The arithmetic control unit 10 also includes a display unit 70 that can be configured from an LCD, a CRT, etc., a recording unit 75 such as a printer, a storage unit 80 that can be configured from a mass storage device such as an HDD, and an audio generation unit 85 such as a speaker. It is connected. The arithmetic control unit 10 can control these units. An operation unit 90 having, for example, a keyboard and a mouse is provided as a user interface for performing settings, inputs, and the like with respect to the arithmetic control unit 10.
[0014]
A constant current supply unit 40 can supply a constant current of a predetermined frequency (for example, about 50 KHz, several hundreds μA) between the constant current electrodes 41 and 42. For example, an oscillation circuit that oscillates a signal of about 50 KHz and a constant current source are provided. Have. A pair of voltage electrodes 51a and 51b are arranged between the constant current electrodes 41 and 42 at a predetermined distance. In the present specification, the pair of voltage electrodes 51 a and 51 b are collectively referred to as a voltage electrode pair 51. In the present embodiment, measurement is performed using a pulse wave measurement electrode in which constant current electrodes 41 and 42 and a voltage electrode pair 51 are fixedly arranged as will be described later.
[0015]
As the voltage electrode 51, an electrode made of a material suitable for measurement, such as an Ag-Agcl electrode, is used, and is directly fixed to the body surface (skin) of the subject. The pulse wave measuring device of this embodiment measures a pulse wave as a bioimpedance waveform.
[0016]
The voltage electrode pair 51 is connected to the impedance converter 50. The impedance converter 50 detects the impedance value (biological impedance) between the voltage electrodes 51a and 51b mounted between the constant current electrodes 41 and 42.
[0017]
When a minute high-frequency current is passed between the constant current electrodes 41 and 42, the voltage electrode pair 51 detects a voltage proportional to the impedance of the living tissue existing between both electrodes. Since blood has an extremely high electrical conductivity compared to other living tissues, impedance detected by the voltage electrode pair 51 is mainly blood that is pumped from the heart, particularly in a portion where there is no other organ such as the upper arm or the lower limb. Is governed by the flow rate. Therefore, by measuring the impedance waveform (voltage waveform) measured by the voltage electrode pair 51, it is possible to obtain a change in the blood flow volume flowing through the part. Since the change in blood flow corresponds to a volume pulse wave that changes in response to the pulse of the heart, it is possible to measure the pulse wave by measuring an impedance waveform that indicates a change in blood flow.
[0018]
The bioimpedance waveform output from the impedance conversion unit 50 is input to the calculation control unit 10. The arithmetic control unit 10 can store the obtained bioimpedance waveform in the recording unit 75 and display it on the display unit 70.
[0019]
■ (Electrode arrangement)
FIG. 2 is a diagram showing the arrangement of the constant current electrodes 41 and 42 and the voltage electrode pair 51 in the present embodiment.
As can be seen from FIG. 2, in the present embodiment, each electrode is preferably disposed on a straight line that is substantially perpendicular to the direction of the arterial movement, with the artery for measuring the pulse wave in between. Thus, by arranging the electrodes so as to be located across the artery, there are the following advantages.
1) When the electrodes are arranged apart from each other in the blood vessel running direction, the averaged pulse wave is measured according to the distance between the voltage electrodes, whereas the observed blood vessel length is shortened, so that it is sharp. An impedance waveform can be obtained.
2) Since the blood vessel length to be observed is short, the local pulse wave of the artery can be measured.
3) Since it is not necessary to dispose the electrodes separately in the direction of blood vessel travel, measurement can be performed in a narrow range, and the influence on other parts of the subject is extremely small.
4) Since the pulse wave can be measured as long as the measurement site has an arterial direction, the measurement site can be easily determined.
5) A pulse wave can be measured by selecting a specific artery at a site where a plurality of arteries exist (for example, an ankle).
The position where the electrode is mounted is not particularly limited, but it is preferable that the living tissue structure is simple. For example, it is preferable to wear it on the limbs, neck, fingers and the like.
[0020]
■ (Configuration of electrode for pulse wave measurement)
In order to easily realize the electrode arrangement shown in FIG. 2, the present embodiment uses pulse wave measurement electrodes in which the constant current electrodes 41 and 42 and the voltage electrode pair 51 are attached at predetermined positions. 3A and 3B are diagrams showing a configuration example of the pulse wave measurement electrode in the present embodiment. FIG. 3A is a plan view seen from the electrode surface, and FIG. 3B is a side view.
[0021]
As shown in FIG. 3, the pulse wave measurement electrode 100 includes a support 53 formed of an insulator such as plastic or rubber, constant current electrodes 41 and 42, and a voltage electrode pair 51. Although not shown in FIG. 3, cables, connectors, and the like for electrically connecting each electrode to the constant current supply unit 40 and the impedance conversion unit 50 actually extend from the support 53 to the outside.
[0022]
The support 53 has the same electrode arrangement surface so that all of the constant current electrodes 41 and 42 and the voltage electrode pair 51 are in the positional relationship as shown in FIG. Instead, the surface on which the constant current electrodes 41 and 42 are disposed extending from the surface on which the voltage electrode pair 51 is disposed is inclined inwardly and in the opposite direction with respect to the surface on which the voltage electrode pair 51 is disposed. Have That is, the constant current electrode is so that the constant current flows evenly in the thickness direction of the tissue between the constant current electrodes 41, 42, and the constant current electrodes 41, 42 are sufficiently adhered to the curved body surface such as the extremities. 41 and 42 are provided on the inclined surface in the opposite direction.
[0023]
Further, between the voltage electrode pair 51, a pressing portion (projection portion) 52 is provided that slightly protrudes from the surface on which the voltage electrode pair 51 is disposed. By providing the pressing portion 52, the venous blood existing between the skin and the arterial blood vessel can be eliminated, the soft tissue can be given rigidity, and the distortion of the impedance waveform due to the pulsation of the artery can be suppressed.
Since the pulse wave measurement based on the impedance measurement can be basically regarded as a pulse wave measurement based on the amount of blood, the pressing by the pressing unit 52 may be such that the distortion of the impedance waveform due to the pulsation of the artery can be suppressed. Accordingly, the pressing force may be weaker than that in the above-described tonometry method in which a part of the arterial blood vessel is pressed to become flat, and the influence on the arterial pulse wave can be ignored.
[0024]
Moreover, it is preferable that the press part 52 contacts the mounting part surface (skin) in a plane for the purpose. Further, the size (contact area) is preferably determined so as to suppress the distortion of the impedance waveform.
As shown in FIG. 4, at the time of measurement, the pressing portion 52 is positioned on the artery 54 to be measured, and the support portion 53 is held by an appropriate holder or by hand, and the pulse wave measuring electrode 100 as a whole. Press lightly against the surface of the body to be measured. Thus, the presence of the pressing part 52 between the voltage electrode pair 51 makes it possible to obtain a more accurate bioimpedance waveform.
When fixing the pulse wave measurement electrode 100 at the time of measurement, a method that does not hinder the venous perfusion returning from the periphery to the center at the measurement site is used so as not to affect the pulse waveform or pulse wave velocity. preferable.
[0025]
When the size (contact area) of the pressing portion 52 is increased, it is necessary to increase the pressing force at the time of measurement, the biological tissue is generally not uniform, and the advantages of local pulse wave measurement are obtained. It is preferable that the distance between each electrode (51a, 51b) which comprises an electrode pair is the minimum distance required in order to acquire a bioimpedance waveform favorably. Further, the distance between the constant current electrodes 41 and 42 is preferably shorter from the viewpoint of allowing a constant current to flow stably to a portion where the pressing portion 52 is in contact. However, in order to adjust the sensitivity to the depth at which the blood vessel to be measured exists, it is preferable that the distance between the constant current electrodes 41 and 42 be adjustable. A plurality of types of measurement electrodes having different electrode distances may be prepared, and the distance can be adjusted by any means such as making the electrodes movable.
[0026]
The shape of the voltage electrode 51 and the constant current electrodes 41 and 42 can be arbitrarily set. However, for example, the constant current electrodes 41 and 42 are not formed in a flat plate shape on the body surface so that good contact with the body surface is achieved. It is preferable that the contact portion is formed in a convex arc shape (FIG. 6A).
Further, as shown in FIGS. 7A and 7B, the width of the constant current electrodes 41 and 42 is set to the voltage electrode 51 and the pressing portion in order to narrow the current flow range and enable more local measurement. It is preferable to make it smaller than the width of 52.
[0027]
The shape of the support 53, including the shape of the electrode arrangement surface, is such that each electrode is in close contact with the body surface of the measurement site and that the constant current flows as evenly as possible in the depth direction of the measurement site. As long as 41 and 42 can be arranged, other shapes may be used.
[0028]
In the measurement of various parts having different thicknesses, the constant current electrodes 41 and 42 can be formed by changing the inclination angle (opening degree) of the portion of the support 53 where the constant current electrodes 41 and 42 are arranged. It becomes possible to make it contact with a mounting site more reliably. Specifically, as shown in FIG. 6A, at least a portion where the constant current electrodes 41 and 42 of the support 53 are arranged is formed of an elastic body, or as shown in FIG. It is conceivable to use a structure such as always energizing in the inner direction (the closing direction).
[0029]
■ (Measurement processing)
Next, the procedure at the time of measurement will be described. First, as described above, the pulse wave measurement electrode 100 is arranged on the extremity of the subject, for example, the arm as shown in FIGS. 2 and 4 and lightly pressed.
[0030]
Next, measurement is started with the pulse wave measurement electrode pressed. As described above, the measurement process can be realized by a CPU included in the arithmetic control unit 10 executing a control program stored in a ROM or the like and controlling each unit.
[0031]
For example, when an instruction to start measurement is given via the operation unit 90, first, a predetermined high-frequency constant current is supplied from the constant current supply unit 40 between the constant current electrodes 41 and 42. As described above, the constant current applied to the living body is about 50 KHz and about several hundred μA.
[0032]
Next, the acquisition of the impedance waveform output from the impedance converter 50 is started. The acquired impedance waveform is sampled at a predetermined frequency and converted into digital data, and data for the most recent predetermined time is stored in the storage unit 80, for example. Alternatively, digital data of an impedance waveform within a predetermined measurement time may be stored in the storage unit 80.
Of course, the measured waveform can be displayed on the display unit 70 or printed out from the recording unit 75.
[0033]
Thus, according to the pulse wave measurement device according to the present embodiment, it is possible to measure the pulse wave simply by lightly pressing the electrode against the measurement site, and the burden on the subject can be reduced to an extent that can be almost ignored. The apparatus can be configured with a simple configuration, and the apparatus can be miniaturized. Further, it is not necessary to use an expensive sensor such as an ultrasonic sensor, and the cost of the apparatus can be reduced. Furthermore, since it is not necessary to find a place where the pulse is touched, the measurement operation itself is easy.
[0034]
The measurement start instruction may be given from, for example, a button provided on the pulse wave measurement electrode, in addition to being given explicitly from the operation unit 90, or to the constant current electrodes 41 and 42 at all times. May supply a constant current, monitor the output from the impedance converter 50, and automatically start the measurement when it is determined that the electrode is pressed against the measurement site.
[0035]
■ (Modification of the first embodiment)
In the first embodiment, the pulse wave measuring device that measures the pulse wave of the subject at one place is shown. However, as shown in FIG. 5, the constant current supply unit, the impedance conversion unit, and the pulse wave measurement electrode By providing a plurality of pairs of current electrode pairs and voltage electrode pairs and measuring pulse waves at a plurality of sites, the pulse wave propagation velocity can be measured.
[0036]
In this case, after the impedance waveforms from the impedance conversion units 50a and 50b are digitized and stored as described above, the characteristic points common to each waveform (pulse wave rising points within one waveform period) are obtained from each digital waveform data. And a notch or the like), and a time shift (delay amount) of the feature point is detected. Then, the pulse wave propagation velocity is calculated by dividing the detected delay amount by the distance L between the electrode pairs or the anatomical blood vessel length. The pulse wave velocity may be a value corrected by the blood pressure value by a known method.
[0037]
The calculated value is output together with other necessary information in a predetermined format in the display unit 70 and / or the recording unit 75. It is also possible to store the calculation result in the storage unit 80. At this time, the corresponding impedance waveform data, the calculated pulse wave propagation velocity, and other information related to the measurement (for example, the sex of the subject, age, measurement site, distance L between the electrode pair, the magnitude of the applied constant current, and between the constant current electrodes You may memorize | store with the information selected from distance etc.).
[0038]
Further, by further providing a known heart sound microphone, by determining the time difference between the second heart sound of the subject obtained using this heart sound microphone and the pulse wave obtained from the electrodes attached to the neck and thigh of the subject, It is also applicable to the measurement of pulse wave velocity in the aorta.
[0039]
Furthermore, since arterial volume pulse waves can be accurately measured, measurement of STI (time phase of systole) and measurement of arterial vascular stiffness index by comparison of early and late systolic waves from local pulse wave shape Measurement of the degree of load on the heart, blood vessel compliance measurement from the diastolic waveform, and the like can be performed. It is also possible to give these measurement functions to the arithmetic control unit 10 to display, save, and output measurement results.
[0040]
[Other Embodiments]
In the above-described embodiment, for example, the embodiment shown in FIG. 1, the configuration in which the constant current electrode pair 41 and 42 and the voltage electrode pair 51a and 51b are independent has been described. However, the constant current electrode pair and the voltage electrode pair are shared. It is also possible to do. For example, in FIG. 1, the voltage electrodes 51a and 51b may be used as the electrodes of the constant current electrode pair. In this case, the constant current supply unit 40 is connected to the voltage electrodes 51a and 51b, and the constant current electrode pairs 41 and 42 are not necessary.
[0041]
In this case, the constant current electrodes 41 and 42 need not be provided on the support 53 of the pulse wave measurement electrode 100, but it is preferable that the shape of the electrode ground plane of the support 53 is not changed. That is, the surfaces on which the constant current electrodes 41 and 42 are provided are inclined in directions opposite to each other, in addition to the constant current flowing uniformly in the depth direction of the measurement site, This is because a function as a guide for arranging in a substantially orthogonal direction is also intended. That is, particularly when measuring in the limbs, if the pulse wave measuring electrodes are arranged so as to correspond to the cross-sectional shape of the limbs, the electrode pairs are naturally arranged in a direction substantially orthogonal to the direction of the artery.
[0042]
Also, when measuring the pulse wave propagation velocity, the time lag of the waveform was detected with the time lag of the feature points (rise, notch, etc.) detected from the acquired impedance waveform. It is possible to detect the time lag using any other method such as obtaining the correlation and using the delay amount when the maximum cross-correlation is obtained as the time lag of the waveform.
[0043]
【The invention's effect】
As described above, according to the present invention, the load on the subject is small, and the pulse wave can be measured with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a pulse wave measurement device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an example of electrode arrangement at the time of measurement using the pulse wave measuring device according to the first embodiment of the present invention. FIG. 3 is a diagram showing a pulse wave measuring device according to the first embodiment of the present invention. It is a figure which shows the structural example of the electrode for pulse wave measurement in.
4 is a diagram showing a state when the pulse wave measurement electrode of FIG. 3 is mounted. FIG. 5 is a block diagram showing a configuration example of a pulse wave measurement device according to a modification of the first embodiment of the present invention. It is.
6A is a diagram showing another example of the shape of the constant current electrode, and FIGS. 6B and 6C are diagrams showing another example of the configuration of the pulse wave measurement electrode.
FIG. 7 is a diagram for explaining the effect of reducing the width of the constant current electrode.

Claims (7)

A support means having an electrode mounting surface;
A pulse wave measurement electrode having a first electrode pair mounted on the electrode mounting surface,
The electrode mounting surface has a first pair of portions where each electrode of the first electrode pair is provided, and a second pair of portions extending outward from the first pair of portions, the first pair of sites consists substantially the same plane, characterized in that said second pair of sites are composed of surface inclined opposite and inwardly to each other with respect to portions of each of the first a pair An electrode for pulse wave measurement.   2. The pulse wave measuring electrode according to claim 1, further comprising a second electrode pair comprising electrodes provided on each of the inclined surfaces. Furthermore, the support means comprises
3. The pulse wave measurement electrode according to claim 1, wherein the electrode mounting surface has a protrusion between a first pair of portions on which the electrodes of the first electrode pair are mounted. 4. . The pulse wave measurement electrode according to claim 1,
Constant current supply means for supplying a predetermined constant current between the first electrode pair;
A pulse wave measurement device comprising: a pulse wave acquisition unit that acquires a voltage waveform representing a change in bioimpedance from the first electrode pair as a pulse wave. An electrode for pulse wave measurement according to claim 2,
Constant current supply means for supplying a predetermined constant current between the second electrode pair;
A pulse wave measuring device, comprising: a pulse wave acquisition unit that acquires a voltage waveform representing a change in bioimpedance from the first electrode pair as a pulse wave.   The electrode constituting the first electrode pair is attached to the extremity, neck, or finger surface of the subject so as to be located across the artery that runs. The pulse wave measuring device according to 1. Furthermore, the support means comprises
A protrusion between the first pair of portions on the electrode mounting surface where the electrodes of the first electrode pair are mounted;
The pulse wave measurement electrode according to claim 2, wherein a width of the second electrode pair is smaller than a width of the first electrode pair and the protrusion.

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