CN115316993A - A method and device for adaptive noise filtering based on flexible bioelectric dry electrodes - Google Patents

Abstract

The invention discloses a self-adaptive noise filtering method and device based on a flexible bioelectricity dry electrode. The flexible bioelectricity dry electrode is used for noninvasively collecting electrocardiosignals, heart sound signals and thoracic impedance detection signals of the body surface of a human body, and the dry electrode consists of three parts: the first part is a bioelectricity signal acquisition flexible dry electrode which consists of a b-electrocardiosignal acquisition electrode and an e-electrocardiosignal acquisition electrode; the second part is a chest impedance detection circuit which is used for measuring the chest impedance changed when the human body moves and is used as one of the reference signals for adaptively filtering noise; the third part is a three-axis acceleration sensor used for detecting the motion state of the human body and used as one of the reference signals for adaptively filtering noise. The dry electrode provided by the invention has good flexibility and customizability, does not need conductive gel, and reduces motion artifacts generated during human motion by adopting a self-adaptive noise filtering technology.

Description

A self-adaptive noise filtering method and device based on flexible bioelectric dry electrodes

technical field

The invention belongs to the technical field of medical signal detection and processing, and in particular relates to an adaptive noise filtering method and device based on flexible bioelectric dry electrodes.

Background technique

The electrocardiogram can reflect the electrical activity process of the human heart (represents the comprehensive process of the entire electrical excitation of the heart), and has important reference value for the basic function of the heart and its pathological research. It can analyze and identify various arrhythmias, and can also reflect the damage of the myocardial Condition and the functional structure of the atrium and ventricle. Electrocardiogram is the main basis for the treatment of cardiovascular diseases. It has the advantages of reliable diagnosis, simple method and no harm to patients. It is becoming more and more important in modern medicine.

In current clinical applications, Ag/AgCl wet electrodes are widely used to collect bioelectrical signals on the human body surface. In order to prevent noise interference during the collection process and ensure good contact between the skin and the electrodes, such electrodes usually need to use conductive electrodes. The conductive glue is used to reduce the contact resistance, and the conductive glue is easy to dry and solidify, which reduces the collection effect. And before using the wet electrode, it is usually necessary to pre-treat the skin, such as body hair shaving, alcohol wiping, etc., which brings inconvenience to the subjects and the operating physicians.

With the approval of regulatory agencies and the advancement of related technologies, wearable devices that continuously monitor the state of human health for a long time have become possible. Dry electrodes generally use contact electrodes. The conductive parts of some dry electrodes are made of metal materials, which have poor flexibility. The contact surface with the skin will change with the movement of the human body. The change of the contact surface will reduce the signal quality. In some In some cases, it may even cause damage to the human body. Some other dry electrodes use a foam material between the conductive part and the base. Although this method ensures good contact between the electrode and the skin, it increases the thickness of the electrode and may cause discomfort to the patient when worn for a long time. Therefore, the present invention proposes a multilayer flexible bioelectric dry electrode, which adopts a multilayer structure and is realized by screen printing technology, and has good flexibility and customizability.

Wearable ECG monitoring equipment usually records various types of noise, which can be summarized into five types: (1) motion interference caused by EMG signals; (2) motion interference caused by skin deformation comes from the inner and outer layers of the skin. Potential difference between layers; (3) motion interference caused by movement between metal and skin; (4) motion interference caused by wire movement; (5) interference caused by external static electricity.

Motion artifacts are the most difficult type of noise to eliminate because their frequency spectrum usually overlaps with very important spectral components of the ECG signal, usually due to transient (but not step) baseline drift caused by patient or electrode motion, and people's daily Motion interference will make wearable ECG monitoring devices unable to provide diagnostic quality ECG signals. In order to accurately diagnose heart disease, we need to reduce motion interference as much as possible to ensure the quality of ECG signals.

Contents of the invention

The purpose of the present invention is to propose an adaptive noise filtering method and device based on flexible bioelectric dry electrodes, which are used for long-distance monitoring of patients' ECG signals and heart sound signals. Technology and lead placement technology can overcome the existing motion artifact interference, a multi-layer flexible bioelectric dry electrode that can adaptively filter noise.

The content and main technical features of the present invention are as follows:

(1) An adaptive noise filtering method and device based on a flexible bioelectric dry electrode disclosed in the present invention, the device includes: a flexible dry electrode for bioelectric signal acquisition, a chest impedance detection circuit, a three-axis acceleration sensor, an adaptive Filter and self-powered module, and the first three parts are relatively independent and not connected to each other. Among them, the flexible dry electrodes for bioelectrical signal collection include ECG signal collection electrodes and heart sound signal collection electrodes, all of which are made of fabric base layer, polydimethylsiloxane Oxygen (PDMS) elastic film layer, stretchable sealing layer, flexible sensing layer of carbon-silver mixture (printed circuit), and the flexible dry electrode, chest impedance detection circuit and three layers realized by screen printing technology Integration of shaft acceleration sensors;

The method is a minimum mean square (LMS) adaptive noise filter. First, the reference input signal is a chest impedance change signal and a triaxial acceleration signal. The reference input signal is a signal that has nothing to do with the ECG signal but is strongly related to the noise; Then, the collected ECG signal, heart sound signal, chest impedance change signal and triaxial acceleration signal are transmitted to the adaptive filter to filter out the measurement noise during the bioelectricity detection process. The adaptive filter meets the requirements of low power consumption and simple hardware implementation, and can be used for adaptive noise filtering in different bioelectric detection environments.

(2) A self-adaptive noise filtering method and device based on flexible bioelectric dry electrodes disclosed in the present invention is characterized in that: the multi-layer flexible dry electrodes need to be used in three sets, of which two electrodes As a prerequisite for thoracic impedance testing, they are placed on the lower left and right chests of the patient and are also the position of the I lead. The remaining electrode is placed on the left armpit of the patient as a reference electrode to initially reduce power frequency interference.

(3) An adaptive noise filtering method and device based on a flexible bioelectric dry electrode disclosed in the present invention is characterized in that: the multi-parameter signal acquisition electrode has a multi-layer structure, and from the outer layer to the inner side are respectively Fabric base layer, polydimethylsiloxane (PDMS) elastic film layer, carbon-silver hybrid (printed circuit), and flexible sensing layer. The outer layer refers to the direction away from the human skin, and the inner layer refers to the direction close to the human skin.

(4) A self-adaptive noise filtering method and device based on flexible bioelectric dry electrodes disclosed in the present invention is characterized in that: the self-powered module adopts a lithium-ion battery and a sweat bio-battery, wherein the sweat bio-battery As a self-generating device, microbial tissue is used as a catalyst, and lactic acid produced by human sweat is used as a substrate to power a bio-battery, thereby prolonging the monitoring time of a wearable ECG monitoring device.

(5) An adaptive noise filtering method and device based on flexible bioelectric dry electrodes disclosed in the present invention is characterized in that: the wireless transmission module used in the device is a Bluetooth module or a 2.4G wireless transmission module. Through the wireless transmission module, the adaptively filtered ECG signal and heart sound signal can be compressed and packaged and transmitted to the mobile phone or computer for displaying physiological parameters such as the ECG signal and heart sound signal, and using the data analysis of the smart terminal Ability to conduct preliminary analysis and diagnosis. At the same time, the smart terminal uploads the received ECG and heart sound signals to the cloud server, and the cloud server further analyzes the health data to generate a health data report, and returns it to the smart terminal.

Description of drawings

Fig. 1 is a structural schematic diagram of an adaptive noise filtering method and device based on a flexible bioelectric dry electrode according to the present invention.

Fig. 2 is a front and back view of an adaptive noise filtering method and device application example based on a flexible bioelectric dry electrode of the present invention.

Fig. 3 is a comparison diagram of noise filtering effects of an adaptive noise filtering method and device based on a flexible bioelectric dry electrode according to the present invention.

Fig. 4 is a frame diagram of an adaptive filter algorithm of an adaptive noise filtering method and device based on a flexible bioelectric dry electrode of the present invention.

Specific implementation method

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention.

Referring to Figure 1, it shows the specific structure of the adaptive noise filtering method and device based on the flexible bioelectric dry electrode, which is generally divided into three layers:

(1) The innermost layer that is also close to the skin is a multi-parameter signal acquisition electrode, which can monitor the patient's ECG signal and heart sound signal, and combine the ECG signal with the heart sound signal to better analyze the heart health of the human body , making heart health monitoring more accurate.

(2) The second layer is the chest impedance detection circuit, which monitors the change of the human chest electrical impedance caused by breathing. In each breathing cycle, the increase of the air breathing volume will reduce the conductivity of the human chest. Because at least two electrodes are required to monitor changes in chest impedance, the present invention requires at least three electrodes, two of which are necessary for the chest impedance detection circuit, and the remaining one is used as a reference electrode to initially reduce power frequency interference.

(3) The third layer is a three-axis acceleration sensor, which can accurately detect the characteristic parameters of human body movement, and has the characteristics of miniature, low power consumption, and high resolution. It can detect static and dynamic accelerations and inclination changes in the horizontal direction in various changing environments, and satisfies the condition that the ECG signal is irrelevant but strongly related to motion noise.

Fig. 2 is a schematic structural diagram of an adaptive noise filtering method and device based on a flexible bioelectric dry electrode. The ECG chest strap consists of 1. an elastic fabric base, 2. two multilayer flexible bioelectric dry electrodes that can adaptively filter out noise, 3. a printed circuit, 4. a reference electrode, and 5. an ECG Collector base, 6. Elasticity adjustment buckle and 7. Locking buckle constitute. When monitoring the ECG signal, the patient needs to wear the ECG chest strap on the lower part of the chest, which is consistent with the position of the standard I lead. 4. The reference electrode is located under the armpit of the right arm, and the ECG collector is installed on the base of the ECG collector. The ECG signal of the patient can be monitored in real time.

Fig. 3 is a comparison diagram of the effect before and after filtering of ECG signal monitoring in a twisted state of a healthy person who is equipped with an adaptive noise filtering method and device based on flexible bioelectric dry electrodes.

Described adaptive filtering noise adopts adaptive filter, and algorithm framework is as shown in Figure 4, wherein needs electrocardiogram signal and heart sound signal as main input signal d(k), comprises expected signal x(k) and noise n(k). The reference input signal s(k) is related to the noise n(k), but not to the signal x(k). The reference signal s(n) is fed into an adaptive filter to produce an output y(k), representing a replica as close as possible to the noise n(k). The coefficients of the adaptive filter are constantly changing according to the selected adaptive algorithm. This filtered signal output y(k) is then subtracted from the main input d(k) to obtain the estimated desired signal x ^' (k), as shown in the equation:

"

e(k)=x(k)=x(k)+n(k)-n(k)

e(k) is the filtered signal, and n ^' (k) is an exact copy of the noise n(k).

In this way, the electrocardiographic signal and heart sound signal from which motion noise has been filtered out can be obtained.

Claims (5)

1. An adaptive noise filtering method and device based on a flexible bioelectric dry electrode, characterized in that the device includes: a flexible dry electrode for bioelectric signal acquisition, a chest impedance detection circuit, a three-axis acceleration sensor, and an adaptive filter And the self-power supply module, and the first three parts are relatively independent and not connected to each other. Among them, the flexible dry electrode for bioelectrical signal collection includes ECG signal collection electrode and heart sound signal collection electrode, all of which are made of fabric base layer, polydimethylsiloxane (PDMS) elastic film layer, stretchable sealing layer, flexible sensing layer of carbon-silver mixture (printed circuit), and the flexible dry electrode, chest impedance detection circuit and three-axis acceleration layered by screen printing technology integration of sensors; The method is a minimum mean square (LMS) adaptive noise filter. First, the reference input signal is a chest impedance change signal and a triaxial acceleration signal. The reference input signal is a signal that has nothing to do with the ECG signal but is strongly related to the noise; Then, the collected ECG signal, heart sound signal, chest impedance change signal and triaxial acceleration signal are transmitted to the adaptive filter to filter out the measurement noise during the bioelectricity detection process. The adaptive filter meets the requirements of low power consumption and simple hardware implementation, and can be used for adaptive noise filtering in different bioelectric detection environments. 2. An adaptive noise filtering method and device based on flexible bioelectric dry electrodes as claimed in claim 1, characterized in that: when the multilayer flexible dry electrodes are used, three are used in a complete set, two of which are As a necessary condition for chest impedance detection, the electrodes are placed on the lower left and right chests of the patient, which is also the position of the I lead, and the remaining electrode is placed on the left armpit of the patient as a reference electrode to initially reduce power frequency interference. . 3. A method and device for adaptive noise filtering based on flexible bioelectric dry electrodes as claimed in claim 1, characterized in that: the multi-parameter signal acquisition electrode has a multi-layer structure, from the outer layer to the inner side respectively It is a fabric base layer, a polydimethylsiloxane (PDMS) elastic film layer, a carbon-silver mixture (printed circuit), and a flexible sensing layer. The outer layer refers to the direction away from the human skin, and the inner layer refers to the direction close to the human skin. 4. A method and device for adaptive noise filtering based on flexible bioelectric dry electrodes as claimed in claim 1, characterized in that: the self-powered module adopts a lithium-ion battery and a sweat bio-battery, wherein the sweat bio- As a self-generating device, the battery uses microbial tissue as a catalyst and lactic acid produced by human sweat as a substrate to power the bio-battery, thus prolonging the monitoring time of wearable ECG monitoring equipment. 5. An adaptive noise filtering method and device based on flexible bioelectric dry electrodes according to claim 1, characterized in that: the wireless transmission module used in the device is a Bluetooth module or a 2.4G wireless transmission module. Through the wireless transmission module, the adaptively filtered ECG signal and heart sound signal can be compressed and packaged and transmitted to the mobile phone or computer for displaying physiological parameters such as the ECG signal and heart sound signal, and using the data analysis of the smart terminal Ability to conduct preliminary analysis and diagnosis. At the same time, the smart terminal uploads the received ECG and heart sound signals to the cloud server, and the cloud server further analyzes the health data to generate a health data report, and returns it to the smart terminal.

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