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The use of capacitive electrodes in portable ECG devices

Overchuk K.V., Boyakhchyan A.A., Uvarov A.A., Soldatov V.S. Tomsk Polytechnic University, Tomsk Supervisor: Ph.D., Lezhnina I.A

Abstract

In the last few years, the demand to telemedicine market has grown and growing. One of the reasons is the fact that cardiovascular diseases are leading in the structure of deaths in the world and created a different number of gadgets for monitoring the heart health. Most of these devices are portable ECG. The article describes the growth of the market telemedicine, the relevance of the use of portable ECG and their principle of operation. Most of them are used dry electrodes. But recently a growing interest to the capacitive electrodes which are described in the article. Capacitive electrodes open new opportunities for telemedicine market.

Every year, cardiovascular disease (CVD) kills 17 million people (Figure 1), is more than the population of Moscow. Meanwhile, cardiovascular disease may be asymptomatic, the person may be at risk and even not suspect the existence of violations of the heart. A typical example is sudden cardiac death (SCD), one of the most insidious types of CVD.

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Figure 1. Reasons of death in the world

heart monitoring health electrode

For the diagnosis of heart diseases created a lot of devices. Such devices were reviewed and sensors that are used in them.

Traditional methods of diagnosing of heart diseases mean: 12-lead ECG and Holter monitor. But there are also a variety of portable ECG device that patients can use at home. Such devices are described in «Single-lead portable ECG devices: Perceptions and clinical accuracy compared to conventional cardiac monitoring» [1]. Such medical gadgets are relevant and demand for them is growing, the market of telemedicine gadgets is growing rapidly, and if in 2014 the market volume amounted to 17.8 billion dollars, is expected by 2019 28.9 billion [2].

The article «Single-lead portable ECG devices: Perceptions and clinical accuracy compared to conventional cardiac monitoring» describes devices for ECG monitoring. A study was conducted: patients were given four devices for monitoring ECG and 6 minutes in order to enable them to understand how they work. Later conducting a survey of patients to find out whether you need such gadgets and 75% of patients [3] have expressed an interest. It was also highly appreciated the convenience of each instrument, and most of the patients said that they would buy for personal use such gadgets, which once again proves the high demand in the market of telemedicine.

In the article «Telemedicine Market & Services - 2014 - 2020» describes that telemedicine has become one of the formats of main medicine. The main advantage of telemedicine is that it allows to directly serving the millions of people while saving time and money. Patients do not need to stand in long lines in hospitals, to get to the doctor. Modern gadgets allow you to send the necessary information a doctor via the Internet. The only limitation of telemedicine today is that it is used mainly in developed countries. [3]

One of the most popular gadgets of telemedicine is personal ECG device. Since most heart attacks and deaths are outside hospital so the most logical to use such devices. There are many different algorithms for reading and analyzing the ECG. The principle of these devices is quite simple, after reading the device gives signal to the microcontroller (which already has an analog-digital converter). The converted signal is saved and appears on the LCD ECG signal (or is sent to your smart phone) [4].

In the article "HeartCheck PEN, Telemedicine Device for ECG Acquisition" a medical device for the measurement of ECG described, which is currently only available in pharmacies in Canada [5]. But this device is ideal for the telemedicine market. The device looks like MP3 player (Figure 2.) It is equipped with a small monitor that people could see their EСG. To measure the ECG only need to attach the fingers to the electrodes, the device saves the ECG and if necessary a person can send data to a doctor. The device can determine the risk of sudden cardiac death. So that device can not only buy people with heart disease, but also all those who protect their health.

The principle of operation of most portable cardiographs a similar as that of the 12-lead cardiograph, but instead of the standard three-lead is used only one. Electrocardiograph based on the principle of registration of electrical impulses that arise in the heart. The devices register the difference of potentials at two points of the electric field of the heart (and therefore are used two dry electrodes). The result is the difference between the biopotentials in as a graph on the device screen.

One of the common problems of the electrodes (which are used in these devices) is that they can easily slide over the skin, which leads to interference.

These portable ECG devices have one more disadvantage: they are not able to carry out continuous monitoring of the heart, which complicates diagnosis, for example in the early stages of arrhythmia. In this case device must always be wearable and the best solution is to use a device in which the capacitor electrodes are installed, as it is written in the article "Dry-contact and noncontact biopotential electrodes" [6].

Figure 2. HeartCheck PEN

The article "Dry-contact and noncontact biopotential electrodes" describes in great detail the use of capacitive electrodes and their advantages over conventional medical electrodes. Before you apply the electrodes is necessary degrease in places where the skin electrodes applied, lubricate with a special paste, which has conductive properties. Capacitive electrodes also do not require such action. They are based on the principle of action of a plane parallel capacitor. The electrode is protected by a layer of dielectric material, which is applied to it to insulate the electrode from the measuring object. Sensor sufficiently compact (10x10 mm, Figure. 3), does not require direct electrical contact, respectively, has no polarization effects and should not be wet. The most interest in these sensors because of the ability to measure physiological parameters on the surface of the human body. The sensors can be used for all types of electrophysiological diagnosis. Another feature of these sensors is low energy consumption.

The use of these electrodes relevant, because of the following advantages:

• Low energy consumption;

• It does not need to be lubricated gel (unlike 12-lead cardiograph);

• Don't slide on the skin;

• Don't interfere;

• Resolution better than other electrodes.

In future is planned to develop a portable device using capacitive electrodes.

Figure. 3 Dry-contact electrodes

References

1. Devin D. Mehta, MD, Noreen T. Nazir, MD, Richard G. Trohman, MD, Annabelle S. Volgman, MD, Single-lead portable ECG devices: Perceptions and clinical accuracy compared to conventional cardiac monitoring, Journal of Electrocardiology 48 (2015), p. 710 - 716

2. Global Telemedicine Market (2015-2019), Mordor Intelligence, August 31, 2015

3. Journal of Pharmaceutical, Biological and Chemical Sciences Volume 6, Issue 4, 2015, Pages 344-352

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