JPS60103935A - Wristwatch type electrocardiograph - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-compact cardiac potential monitoring device (hereinafter referred to as a wrist-side type cardiac monitor 14) that is used by being worn on the wrist.

Viewing an electrocardiogram using an electrocardiograph 11 is a simple and most effective means for diagnosing heart disease, and is therefore very widely used. Furthermore, it is well known that recording and analyzing cardiac potential is very effective in preventing heart disease and managing health in daily life, but unfortunately, conventional electrocardiography Even with current technology, it is only about the size of a pocket tape recorder, so it is not used much.

In this method, nine pairs of electrodes are attached to a person's chest using adhesive tape, and the cardiac potential induced therein is amplified and recorded on a cassette tape, which can then be played back and analyzed at a hospital later. However, this method has the disadvantage that the equipment is large and heavy, and the work is cumbersome as it requires continuous rotation of tape with electrodes attached to the chest in order to detect heart attacks or other abnormalities that may occur at any time. It has a fundamental drawback that it is.

Therefore, in his previous patent, Sasaya described a means for recording one's own cardiac potential whenever necessary by incorporating a semiconductor memory of an ultra-small cardiac potential amplifier into an electronic wristwatch. .

The present invention relates to the structure of the electrodes of such a wristwatch type electrocardiograph. Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a diagram illustrating an implementation 911 of the present invention. 1 is the case of the watch body, which is preferably made of plastic. It is a 2-piece watch band. Reference numeral 6 denotes a push button switch, which in this example is used to switch from a normal electronic digital watch to an electrocardiograph. Reference numeral 4 denotes an electrode, and any finger (not shown in FIG. 1) of the right hand touches the electrode 4, and the other 1 on the D side of the case 1
By touching the left wrist 9 with two electrodes (not visible in Figure 1), the cardiac potential between the left hand and the right hand (electrocardiogram, this corresponds to the first lead of the W-shaped cavity) is captured, and the liquid crystal display 5 shows the heart waveform and heart rate.

Unfortunately, the liquid crystal display 5 is displaying the date, time, etc.

FIG. 2 shows an example of the arrangement of electrodes in the embodiment of the present invention. 4B is an electric object that comes into contact with the fingers of the right hand, and is arranged on the front surface of the case 1. FIG.

6.7 is placed on the back side of the case 1, and the left wrist 9
The electrode 7 is particularly referred to as a midpoint electrode. These electrodes 4,6°7 are connected to the electronic circuit 1
Connected to 0. Reference numeral 11 denotes a battery that drives the electronic circuit 10.

FIG. 3 is a block diagram of an electronic circuit used in an embodiment of the invention. Said electrode 4°6.7 is connected to a cardiac potential amplifier 12. The cardiac potential amplifier includes:
It is a differential amplifier. That is, since the electrode 4 is in contact with the right hand and the electrode 7 is in contact with the left hand, the signal V induced between the electrodes 4 and 7 changes the cardiac potential between the left hand and the right hand.
If the AC shoe sound induced in the human body is fllnl, and the polarization voltage generated between the electrode and the skin is ep, then v, = e + e n1 + e pl (1). Next, the electric potential v2 induced between the electrodes 6 and 7 is defined as the cardiac potential is zero, en is the alternating current noise induced in the human body, and vp2 is the polarized voltage generated between the electrodes and the skin. V2 = e nt + e p2 (21) The gain of the differential amplifier is A, and the output voltage is V.

Then vo=A(er-1-(vn,-vn2)+(vp1V
P2)) (It becomes 31.

In equation (3), since Vn and Vn are generally in phase, AC noise is reduced. Also, when the polarization voltage is made of the same metal as the electrodes, the polarity is the same even if the absolute value is slightly different, so (3)
The polarization voltage difference (vp, -vp2) in the equation becomes smaller than the original value. Moreover, the electrode 4 caused by finger contact or the like. Differential amplification is also advantageous for the unavoidable variations in polarization potential between /l,7 and the skin. That is, if the finger 8a is strongly pressed against the electrode 4, the electrodes 6 and 7 will strongly contact the wrist 9, while if the finger 8a is weakly pressed against the electrode 4, the electrodes 6 and 7 will come into contact with the wrist 9. The same will happen on the other side. In this way, since the change in the contact state between the skin and the electrode due to external force is the same for both electrodes 4 and 6.7, the change in polarization voltage can also be calculated by taking the difference as shown in equation (3). , can be made smaller to some extent.

In principle, it is possible to induce a cardiac potential by connecting the electrodes 6 and 7 and using a single input, but in practice it is very unstable, but in the embodiment of the present invention, it is possible to induce a cardiac potential with a single input. It is now possible to induce cardiac potential. The electrocardiogram induction method (differential amplification method) using three-point electrodes l is a well-known electrocardiogram measurement technique. However, since the conventional devices are large in size, their main purpose was to remove AC noise, and the distance between the electrodes was wide. However, as in the embodiment of the present invention, in order to stably induce a cardiac potential in a situation where the contact state between the skin and the electrode is highly variable in a normal posture, it is necessary to It is extremely important to place the electrode in the correct position.

The amplified electrocardiogram signal is converted into a digital signal by the A/D converter 16 and temporarily stored in the RAM 14. A part of the signal output from the RAM 14 passes through the drive circuit 17 and is displayed as a potential waveform on the liquid crystal display 5.

A part of the output signal of the RAM 14 is sent to the D/A converter 18.
The digitized cardiac potential is converted into an analog quantity again, and becomes a waveform with the same waveform as the original waveform, but with an expanded amplitude. applied. 15 is a clock signal generator that generates a clock signal that controls the timing of the entire system; 16 is a controller that generates a control signal that controls the operation of the entire system based on the clock signal; are the A/D converter and the RAM.

The voltage is applied to the drive circuit, the liquid crystal display, and the D/A converter to control their operations. In this example, the frequency for sampling the cardiac potential is 200H2, and the RA
M14 can store 42 seconds of cardiac potential information. In other words, after a seizure occurs or something abnormal is felt,
Since it is possible to observe the cardiac potential for 42 seconds, it can be said that 1-4 points is sufficient medically. Furthermore, the output section "1"
20, a tape recorder or graphic board 1
By connecting Nonta, it is possible to record all the cardiac potential information that has occurred during the 42 seconds stored in the RAM 14. After that, if the information in the RAM 14 is erased, a new cardiac potential can be recorded.

FIG. 4 shows another embodiment of the invention.

In this example, the midpoint electrode 7 is arranged on the front surface of the case 1. Therefore, the right hand 1 is connected to the electrode 4.
One finger 8a of the right hand contacts the middle point electrode 7, and only the electrode 7 on the back surface of the case 1 contacts the left wrist. This embodiment has the advantage that the detection of cardiac potential is not very stable, and the back surface of the case 1 can be simplified.

When used in combination with an electronic wristwatch, the back cover is often removed when replacing the battery, so it is preferable that the back cover has a simple structure.

FIG. 5 shows another embodiment of the invention.

In this case, the electrode that contacts one finger 8a of the right hand uses an electrostatic induction electrode made of a high dielectric material 4a and a metal thin film 4b. In this example, the impedance of the electrostatic induction electrode is high (the capacitance is about 50 nF, so the impedance is 6.4 in the cardiac potential frequency range from 0.5 Hz to 500 H2).
M rh to 64 Ω), so there is a drawback that an impedance conversion circuit as shown in FIG. 6 is required. However, in this embodiment, the contact state between the skin and the electrode is particularly unstable, the impedance of the skin impedance itself is high, and the finger 8a and the metal thin film 4b, which are unstable, are unable to connect the high dielectric material 4a. The biggest advantage is that the various instability caused by contact between the skin surface and the metal surface can be avoided because the electrical connection is made through the metal surface. As the high dielectric constant material, an anodized tantalum film and a thermally oxidized film of silicon can provide a thin and stable bullet, but they have low mechanical strength and are expensive, so they are not very practical. The most practical material is (4-tanx 1 < ゛ium), which is polished to a thickness of 0.12 mm and hardened with resin on the back side to obtain strength.

FIG. 6 shows an impedance conversion circuit when using the electrostatic induction electrode, which itself is not particularly new. Two N-type junction field effect transistors (hereinafter referred to as J
High resistance (approximately 100 MΩ) resistors 25a and 23b are connected between the gates of FETs 21 and 22 and the ground.

There is a resistor 2 between the source of the JFET 21 and 22 and the ground.
4a.

24b (approximately 2 Ω each) are connected to the JFET
Each source of the electrocardiogram amplifier (differential type) 1
Connect with 20 input terminal. In this way, the disadvantage of high impedance of the electrostatic induction type electrode is solved. Since the electrode 6 is made of metal and directly touches the skin, the impedance between the skin and the electrode is not as high as the electrostatic induction electrode.

However, depending on the environmental conditions, the input impedance of the electrocardiogram amplifier 12 is sufficiently high (10 MΩ or more), since the input impedance of the electrocardiogram amplifier 12 is high enough (10 MΩ or more).
Resistors 23b and 24'b are unnecessary.

FIG. 7 shows an example regarding the arrangement of the back electrodes of the case in the embodiments shown in FIGS. 2 and 5. FIG. FIG. 7(,) shows an embodiment in which 2'-" electrodes are arranged line-symmetrically, and FIG. 7(b) shows an embodiment in which they are arranged concentrically.

As described above, the present invention applies the differential amplification method used in conventional electrocardiogram measurement methods to a wristwatch type electrocardiograph.

Even if the midpoint electrodes for differential amplification are placed in close proximity to each other, an electrocardiogram equivalent to that obtained with the conventional standard limb lead method can be obtained, and there is no noise or contact between the electrodes and the skin. It has also become more resistant to fluctuations.

Specifically, the above effects can be obtained by arranging the intermediate electrode on the back or front surface of the main body case. Furthermore, by using an electrostatic induction electrode as the electrode that comes into contact with the fingertip, the effects of the present invention become even clearer. As described above, the effects of the present invention are great in practice.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of electrode arrangement in an embodiment of the present invention, and FIG. 3 is a block diagram of an electronic circuit used in an embodiment of the present invention. FIG. 4 is a diagram showing another embodiment of the present invention, FIG. 5 is a diagram showing another embodiment of the present invention (an example using an electrostatic induction electrode), and FIG. 6 is a diagram showing another embodiment of the invention.
The impedance conversion circuit of the embodiment shown in FIG.
FIG. 7 shows an example regarding the arrangement of back electrodes in an embodiment of the present invention. 1... Case 2... Watch band 6.
...Push button switch 4...Electrode 5...Liquid crystal display 6...
... Electrode 7 ... Midpoint electrode 8a, sl)
...Finger? ...Wrist 10...
Electronic circuit 11...Battery 12...Cardiopotential amplifier 15...A/D converter 14...RA
M15...Clock signal generator 16...Controller 17...Drive circuit 1
8...D/A converter 19...Output amplifier 20...Output terminals 21, 22...N-type junction field effect transistor 23a, 23b, 24a・24b・・・・・・Resistance or higher Applicant Seiko Electronics Industries Co., Ltd.

Claims (3)

[Claims] (1) One of the electrodes arranged on the front and y plane of the case contacts a part of the right hand and the other contacts a part of the left hand to induce a cardiac potential, amplify and display the cardiac potential, An electrocardiograph having a function of storing the electrocardiogram waveform and having a structure suitable for being worn on the arm. (2) An electrocardiogram according to claim +1), characterized in that either one of the electrodes is divided into two electrodes, and one of the divided electrodes is connected to a midpoint input of a differential amplifier. Total. (3) Either one of the two electrodes other than the electrode connected to the midpoint input of the differential amplifier has a structure that induces a cardiac potential by electrostatic induction without directly touching the skin. An electrocardiograph according to claim (2), characterized in that: