JPH029811B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

In order to clearly capture cardiac electrical phenomena, the present invention
Measures electrical potential from many points on the body surface near the heart,
The present invention relates to an electrode for a body surface electrocardiograph that calculates a measured potential and displays a potential distribution diagram at a certain time.

[Conventional technology and its problems]

Conventional electrocardiographs measure potential changes at six points on the chest. This electrocardiograph tests for abnormalities in the heart from the observed waveforms at each point. However, with this type of electrocardiograph, it is difficult to clearly examine all cardiac electrical phenomena. In recent years, a new type of electrocardiograph has been introduced, for example, one that places electrodes at 80 to 200 points on the body surface near the heart, collects cardiac potential from all the electrodes, and comprehensively determines the electrical phenomena of the heart. Surface electrocardiographs have been developed. A body surface electrocardiograph, for example, as shown in Figure 1,
Create a potential distribution map that appears on the body surface near the heart at a certain time. A potential distribution map is a distribution map of potentials on the body surface of cardiac electrical phenomena. The potential distribution diagram is based on the measurement signals from all electrodes.
It is calculated by a computer. That is,
The measured potential of each electrode at a certain time is stored in the computer's memory, and the equipotential points are calculated based on the measured potential of each electrode. It's something to be shown on TV. This type of electrocardiograph displays an electric potential distribution diagram at fixed time intervals (e.g., several milliseconds) to detect the enlargement of positive or negative regions, the state of contraction, and the state of contraction that appear on the body surface near the heart. Changes in potential gradients, etc. are obvious at a glance, and electrocardiographic phenomena are clearly displayed. Despite having such excellent characteristics, body surface electrocardiographs have not yet become widespread. This is because it is extremely difficult to accurately measure cardiac potential from an extremely large number of measurement points at the same time. The reason why it is difficult for this type of electrocardiograph to accurately measure the potential from the electrodes is due to the following reasons. The number of measurement points is extremely large. It is difficult to determine whether a measurement signal is an accurate measurement signal or a measurement signal with an error. Electrode measurement errors significantly distort the potential distribution map, but it is difficult to determine whether the distortion is caused by heart disease or measurement errors. An increase in the number of measurement points makes measurement significantly more difficult. For example, assume that each electrode causes a measurement failure with a probability of 1/100. In this case, with 10 electrodes, the probability that any one of the electrodes will cause a measurement failure is only 1/10. In other words, out of 10 measurements, the probability that any electrode will produce a measurement error is only once, and all electrodes will be able to accurately measure the remaining 9 measurements. While using the same electrode,
If the cardiac potential is measured at 100 points, some electrode will always have a measurement error, and the cardiac potential cannot be measured accurately with all electrodes. Each electrode is 1/100
It is by no means rare in actual cardiac potential measurement that a measurement error occurs with a probability of . For this reason, with body surface electrocardiographs, it takes time to set many electrodes on the body surface, and it also takes a considerable amount of time to accurately measure cardiac potential from all electrodes. be. Further, the body surface electrocardiograph has the disadvantage that it is difficult to determine whether the measured potential is accurate or inaccurate based on the measured potential of the electrodes. This is because, unlike conventional electrocardiographs, they do not display temporal changes in cardiac potential. With conventional electrocardiographs that observe waveforms that change over time, if the electrodes make poor contact, the zero point shifts, and you can clearly see that there is a measurement error. However, body surface electrocardiographs do not display temporal changes in cardiac potential, but rather display potential distribution diagrams to examine electrical phenomena in the heart.
It is difficult to distinguish poor electrode contact from the potential distribution map. Further, it is a problem that although body surface electrocardiographs produce different potential distribution maps depending on the patient, distortion of the potential distribution diagram due to heart disease may be similar to distortion of the potential distribution diagram due to poor measurement. For this reason, it is extremely difficult to determine whether there is a heart disease or due to poor measurement by looking at a distorted potential distribution diagram. This is the biggest drawback of body surface electrocardiographs, as the potential distribution map may be distorted even when observing a healthy person. For this reason, it takes four people to accurately measure cardiac potential from approximately 100 locations using conventional suction cup electrodes.
It takes 30 minutes to over an hour, and even if everything goes well,
Only one or two people can be tested per hour. For this reason, this type of electrocardiograph uses disposable electrodes. Disposable electrodes have adhesive paste and electrolyte applied to their surfaces. This electrode can measure cardiac potential more stably than a suction cup type electrode. However, with this electrode structure, it is difficult to accurately measure multiple cardiac potentials simultaneously. Furthermore, the electrodes of the body surface electrocardiograph can accommodate body shapes due to individual differences and gender differences, and do not cause measurement errors due to irregularities on the body surface or variations in irregularities due to breathing movement. It does not cause fear, pain, or pressure to the patient, and it can be easily and quickly attached and detached, requiring no maintenance, and each electrode can be placed in a fixed position without relative displacement. It is required that it can be placed in Incidentally, an electrode for electroencephalography in which a needle electrode is elastically pushed out by a spring has been developed (Japanese Patent Publication No. 30866/1986). Electrodes with this structure can be applied to body surface electrocardiograph electrodes. When applying an electrode with this structure to a body surface electrocardiograph, it is necessary to press the needle electrode against the body surface with a strong pressing force in order to accurately detect the potential at the contact point. however,
In reality, it is limited by the pressing force of the needle electrode. The reason is that since the number of electrodes is large, the overall pressing force is strong. For example, if the pressing force of one electrode is 500g,
If the number of electrodes is 100, the entire chest will be pressed with a strong force of 50 kg, giving the patient intense compressions. It is never preferable to press with a strong pressure when examining a patient with weakened physical strength. For this reason, it is not possible to put into practical use an electrode that can stably measure cardiac potential simply by increasing the pressing force on the electrode. In addition, in order for a body surface electrocardiograph to display a precise potential distribution map, in addition to using electrodes to accurately measure cardiac potential, the number of electrodes must be increased to increase the number of measurement points. Set the electrode on the body surface without shifting the position. That is also important. The more measurement points there are, the more precise the potential distribution map can be created. However, the more measurement points there are, the more difficult it becomes to accurately measure cardiac potential from all electrodes. Furthermore, it is necessary to measure the cardiac potential without moving the electrode from a specific position. A computer that receives cardiac potentials from the electrodes calculates a potential distribution map assuming that the electrodes are in a defined array. If the position of the electrode deviates from the determined position, distortion will occur in the calculated potential distribution map. This is because the electrode position imagined by the computer and the actual measurement position deviate from each other. For this reason, it is important that the electrodes be able to measure the cardiac potential at a specified body surface without shifting their positions.

[Object of this invention]

An object of the present invention is to provide electrodes for a body surface electrocardiograph, in which electrodes arranged close to each other can stably contact the uneven human body surface and accurately detect potentials at body surface locations. Another important object of the present invention is to provide an electrode for a body surface electrocardiograph that has a weak pressing force on the body surface and can detect body surface potential without causing pressure or discomfort to the patient. be.

[Means to solve conventional problems]

The electrode for a body surface electrocardiograph of the present invention has the following configuration. (a) Electrodes for body surface electrocardiographs are electrodes that touch multiple points on the skin surface of the human chest and detect the potential at the points of contact. (b) The electrode includes a plurality of needle electrodes that directly contact the skin surface of the human body, a main body having the needle electrodes, and an elastic body that elastically presses the tips of the needle electrodes toward the body surface. There is. (c) At least the surface of the needle electrode is electrically conductive so that cardiac potential can be detected by contacting the surface of the human body. (d) A plurality of needle electrodes are arranged close to each other, and when one of these needle electrodes arranged close to each other comes into contact with the human body surface, the cardiac potential on the body surface increases. The electrodes are electrically connected in parallel to form a set of electrode units so that the electrodes can be detected. (e) There are multiple sets of electrode units, and within one electrode unit, no matter which needle electrode measures the cardiac potential, positional errors are minimized.
The needle electrode spacing within one electrode unit is close compared to the distance between adjacent electrode units. (f) In order for all needle electrodes to be pressed uniformly against the body surface, each needle electrode can be moved in and out of the body surface independently and elastically by an elastic body, and must be connected to the same electrode unit. The needle electrodes constituting the device are attached so as to be movable in parallel or substantially parallel. (g) The needle electrodes of any or all of the electrode units in each set detect the local potential on the body surface, and the multiple sets of electrode units locally detect the cardiac potential at a specific point on the human chest; The electrical signal is configured to be input to the arithmetic circuit.

[effect]

In order for a body surface electrocardiograph to accurately create a potential distribution map, it is important to accurately measure cardiac potential without positional deviation even with a large number of electrodes, as mentioned above. By the way, the skin surface of the human body is an electrically extremely non-uniform layer, and the contact resistance of electrodes varies significantly in some areas. The contact resistance of the electrode to the skin surface varies depending on the pressing force of the electrode, but if you press the needle electrode to a painless level without using an electrolyte between the electrode and the human body surface, the contact resistance between the electrode and the skin will increase. The contact resistance varies greatly, from several tens of kilohms to several thousand kilohms, depending on the contact portion. For example, when a needle electrode comes into contact with skin near pores, electrical resistance tends to drop significantly. For this reason, an electrode that contacts a local part of the body surface, such as a needle electrode, may not be able to accurately measure cardiac potential even if the tip appears to be in contact with the human body surface. This is because the tip of the needle electrode may come into contact with a portion of the skin with high contact resistance. Needle electrodes that come into contact with areas of high contact resistance should not be pressed against the skin so hard that the patient cannot bear it due to pain.
The contact resistance between the needle electrode and the skin is too low to accurately measure cardiac potential. It is a pressing force that is painful and difficult to endure even with a single needle electrode. Pressing 100 needle electrodes against the body surface with such strong pressure is not practical due to both the pain and the total pressure. However, needle electrodes that come into contact with areas with low contact resistance with the skin are pressed against the skin with weak pressure and can accurately measure cardiac potential. The electrode for a body surface electrocardiograph of the present invention makes effective use of the unique conditions of the human body surface and succeeds in accurately measuring cardiac potential with a weak pressing force as a whole. That is, the electrode for a body surface electrocardiograph of the present invention is an electrode unit composed of a plurality of needle electrodes, and measures the cardiac potential induced at a specific point on the body surface. One set of electrode units covers one part of the body surface.
Measuring the cardiac potential at a point. Multiple sets of electrode units are used to measure cardiac potential at multiple points on the body surface. In one set of electrode units, it is not necessary that all needle electrodes accurately measure cardiac potential. If any one needle electrode can accurately measure the cardiac potential, that electrode unit can accurately measure the cardiac potential even if the other needle electrodes cannot accurately measure the cardiac potential. Not all needle electrodes necessarily measure cardiac potential accurately. Further, in the electrode of the present invention, each needle electrode is independently and elastically pressed against the body surface. Furthermore, the needle electrodes constituting the same set of electrode units are movable in parallel or nearly parallel to each other, and are pressed against the body surface by elastic bodies. In this electrode structure, each needle electrode moves in and out in response to the unevenness of the body surface, and each electrode is elastically pressed against the body surface. The needle electrode set on the body surface in this state is pressed against the body surface in an almost ideal state. However, even when pressed against the body surface under ideal conditions, not all needle electrodes can accurately measure cardiac potential. Therefore, in the electrode of the present invention, a plurality of needle electrodes constitute one set of electrode units. It is sufficient that any one of the needle electrodes constituting a set of electrode units can accurately measure cardiac potential. The probability that all needle electrodes constituting one set of electrode units will not be able to accurately measure cardiac potential is extremely low. For example, assuming that the probability that each needle electrode cannot accurately measure cardiac potential is 1/100, and one set of electrode units is composed of four needle electrodes, all four needle electrodes will measure cardiac potential. The probability that it cannot be measured is 1 in ¹⁰⁸ , which is almost zero. This electrode unit
If 100 sets are used, the probability of not being able to accurately measure cardiac potential is only 1 in 10 ⁶ (1 in a million). That is, although the electrode of the present invention has an extremely simple configuration, it has the advantage of being able to accurately measure cardiac potential using a large number of electrodes. By the way, whether a needle electrode can accurately measure cardiac potential is determined by the contact resistance between the needle electrode and the body surface. If the contact resistance between the needle electrode and the skin surface is higher than the input impedance of the first stage amplifier to which the needle electrode is connected, the cardiac potential cannot be accurately detected even if the needle electrode contacts the body surface. For example, if the input impedance of the first-stage amplifier is 10MΩ and the contact resistance between the needle electrode and the body surface is 2MΩ, the cardiac potential induced in the needle electrode is input to the first-stage amplifier with a drop of about 20%. Under normal conditions, it is not uncommon for the contact resistance between the needle electrode and the body surface to be several MΩ or more. The contact resistance between the needle electrode and the skin surface becomes smaller when the pressing force of the needle electrode is increased. Therefore, in order to increase measurement accuracy, it is preferable to press the needle electrode against the body surface with as strong a force as possible. However, strongly pressing needle electrodes cause pain to the patient. For this reason, the needle electrode should not be too weak or too strong. It is extremely important to press all needle electrodes against the body surface with a predetermined pressing force. In order to achieve this, the electrode of the present invention has a structure in which the needle electrodes constituting the electrode unit are each elastically pushed out independently. Therefore, each needle electrode moves in and out according to the unevenness of the body.
Pressed against the body surface in ideal conditions. Any one of the plurality of needle electrodes pressed against the body surface contacts the body surface with a contact resistance lower than the input impedance of the amplifier, and accurately measures the cardiac potential. Therefore, by using the electrode for a body surface electrocardiograph of the present invention, it is possible to realize the feature of accurately testing the cardiac electrical phenomena of many patients having a wide variety of body types. In addition, since the cardiac potential can be measured accurately by electrically contacting the body surface with any one needle electrode, the pressing force of one needle electrode can be weakened to minimize the pain caused to the patient. It also has the advantage of being able to accurately test cardiac electrical phenomena.

[Preferred embodiment]

Examples thereof will be described below based on the drawings. The electrocardiograph shown in FIG. 2 consists of an electrode 1 and an arithmetic circuit 2.
, an operation switch 3, an XY plotter 4, and a monitor television 4'. The electrode 1, as shown in FIGS. 3 to 5,
It consists of ten main bodies 6 and eight sets of electrode units 5 attached to one set of main bodies 6. Each main body 6 is connected by a flexible member 7 which is a string-like rubber-like elastic body, and an elastic wrapping band 8 is connected to the outermost main body 6. An adhesive tape 9 is sewn to the tip of the wrapping band 8. The electrode unit 5 is composed of four needle electrodes 5N. As shown in FIG. 4, the needle electrodes 5N are arranged side by side in the main body 6 so as to be able to move in and out. The main body 6 includes a box-shaped case 10 that is open at the bottom.
and two insulating plates 11 and 12. The needle electrode 5N forming the electrode unit is inserted through the two plates 11 and 12 so as to be freely removable and removable. A needle electrode 5 is placed between the plates 11 and 12.
A coil spring 13, which is an elastic body that elastically pushes out N, is provided. The coil spring 13 is a push spring, and the needle electrode 5N
The lower end passes through the middle of the needle electrode 5N, and the upper end passes through the upper plate 11 and is connected to a conductive layer 14 such as a copper film printed on the upper surface of the plate. The main body 6 shown in FIGS. 5 and 6 has eight sets of electrode units 5 in one main body 6, and one set of electrode units 5 is composed of four needle electrodes 5N. The four needle electrodes 5N are arranged in parallel, fairly close to each other compared to the spacing between the electrode units 5 of each set, and spaced apart by, for example, a fraction of the spacing between the electrode units. . The coil springs 13 inserted into the four needle electrodes 5N are connected by a conductive layer 14 on the upper surface of the plate. In this structure, for example, the interval between the needle electrodes 5N is set to 1 to 1.
You can get quite close to it at 15mm. In this way, the needle electrode 5
The structure in which the detected potential of the needle electrodes 5N is transmitted to the leader line 15 even with the coil spring 13 pushing out N is an ideal structure in that each needle electrode 5N can freely move up and down without being influenced by each other. In the upper plate member 11, a cylinder 16 is inserted into a through hole through which the needle electrode 5N is inserted. The cylindrical body 16 is made of metal so as to reduce the frictional resistance with the needle electrode 5N, which is a metal wire made of stainless steel, copper, aluminum, or a conductive alloy.
Alternatively, a cylindrical body with a smooth inner surface and low frictional resistance is used. Further, as shown in FIG. 6, this cylindrical body 16 protrudes somewhat downward from the lower end of the plate material 11. The upper end portion of the coil spring 13 is inserted into the protruding portion with the needle electrode 5N being pushed in and the coil spring 13 being crushed. According to this structure, when the needle electrode 5N is pushed all the way in, the crushed coil spring 13 contacts the needle electrode 5N, and the coil spring 13 moves into the needle electrode 5N.
This prevents the movement of the needle electrode 5N from being stopped, and the needle electrode 5N always moves in and out smoothly. The needle electrode 5N, which is elastically pushed out by the coil spring 13, has a lower end of the coil spring 13.
For example, the thickened portion fixed by soldering or welding gets caught in the through hole 17 of the plate material 12 below, and is prevented from slipping out. As shown in FIG. 7, the upper plate material 11 is printed with a conductive layer 14 such as a copper film, and a lead wire 15 is connected to one end of the conductive layer 14. In the main body shown in FIG. 8, a coil spring 13 is disposed above the upper plate at the upper end of the needle electrode 5N, and the needle electrode 5N is inserted through the coil spring. A coil spring is a tension spring.
The upper end is connected to the upper end of the needle electrode, and the lower end is welded to the conductive layer printed on the surface of the plate material.
A leader wire is connected to the conductive layer. In the main body shown in FIG. 9, coil springs are arranged above and below the upper plate. According to this structure, one end of one or both of the upper and lower coil springs may be connected to the conductive layer of the plate material, and a leader wire may be connected to the conductive layer. In this case, one of the solid materials may be made considerably softer, that is, the elastic modulus, which is the force required to extend a unit length, may be made considerably smaller. For the flexible member 7 that connects each block, a non-stretchable string or band, a flexible synthetic resin, or the like can be used. The lead wires 15 connected to the electrodes are collected into one shielded wire 26, and the shielded wire 26 is also connected to the arithmetic circuit 2. By the way, the electrocardiogram signal level detected by the electrodes is quite low, and sufficient consideration must be given to removing external noise. By shielding each block independently, the S/N ratio can be improved. In order to further reduce the noise level, it is preferable to incorporate amplification means, such as an FET, for amplifying the signal detected by the electrodes in the block. The connection between the FET 18 and the electrode unit 5 is the first
As shown in FIG. 0, there is no need to incorporate a power supply in each main body, and the load resistance R of the FET 18 may be incorporated in the arithmetic circuit. Also, conveniently,
Even if the FET 18 is incorporated, the number of leader lines 15 does not increase. That is, the main body having eight sets of electrode units incorporates eight FETs, and can transmit the body surface detection potential to the arithmetic circuit 2 using eight output signal lead lines 15 and one ground wire. FIG. 11 shows a state in which the electrode is attached to the human chest. That is, each main body 6 is placed on the body surface near the heart, and both ends of the wrapping band 8 are connected to each other with adhesive tape 9 to bring the electrodes of the main body 6 into contact with the body surface with a constant pressure. In this case, as shown in FIG.
It is also a good idea to tighten the electrode with a stronger force to press and contact the electrode with the body surface. The arithmetic circuit 2 processes the electrical signals sent from the electrodes according to a predetermined method, calculates equipotential lines at regular intervals from the electrical signals sent from the electrodes, and outputs the results. A signal is sent to the XY plotter 4 and monitor television 4', and an equipotential diagram is drawn on these.

[Brief explanation of drawings]

Figure 1 is a body surface equipotential diagram near the heart, Figure 2 is a block diagram of an electrocardiograph in which the electrode of the present invention is used, and Figures 3 to 5 are electrodes according to an embodiment of the present invention. Perspective view, sectional view, bottom view, Fig. 6,
Figures 8 and 9 are cross-sectional views showing the mounting location of the electrode unit, Figure 7 is a plan view of the plate, Figure 10 is a wiring diagram of the FET connected to the electrode, and Figure 11 shows the mounting state of the electrode. FIG. DESCRIPTION OF SYMBOLS 1...Electrode, 2...Arithmetic circuit, 3...Operation switch, 4...XY plotter, 4'...Monitor TV, 5...Electrode unit, 5N...Needle electrode, 6...
...Main body, 7...Movable member, 8...Wrap band, 9
... Adhesive tape, 10 ... Case, 11 ... Plate material, 12 ... Plate material, 13 ... Coil spring,
14...Conductive layer, 15...Leader wire, 16...Cylinder, 17...Through hole, 18...FET, 19...
Band, 26...shielded wire.

Claims (1)

[Claims] 1. An electrode for a body surface electrocardiograph having the following configuration. (a) By touching multiple points on the skin surface of the human chest,
This is an electrode that detects the potential at the point of contact. (b) The electrode includes a plurality of needle electrodes that directly contact the skin surface of the human body, a main body having the needle electrodes, and an elastic body that elastically presses the tips of the needle electrodes toward the body surface. There is. (c) At least the surface of the needle electrode is conductive. (d) A plurality of needle electrodes are arranged close to each other, and the plurality of needle electrodes arranged close to each other are electrically connected in parallel to form a set of electrode units. are doing. (e) There are multiple sets of electrode units, and the needle electrode spacing within one electrode unit is close compared to the distance between adjacent electrode units. (f) The needle electrodes are capable of independently and elastically moving in and out toward the body surface using elastic bodies, and the needle electrodes constituting the same set of electrode units are free to move in parallel or almost parallel. is attached to. (g) Each set of electrode units detects the local potential of the body surface, multiple sets of electrode units locally detect the cardiac potential of the human chest, and this electrocardiographic signal is input to the calculation circuit. It is configured.