纺织结构动态心电图电极-皮肤界面噪音机理研究

As the growing aging population, cardiovascular diseases (CVDs) have been the major cause of death among elderly people, which have become a medical burden to the whole society. CVDs are often chronic, accumulative and unpredictable that hardly be diagnosed by conventional ECG measurement. Fortunately, holter ECG monitoring has proven to be the effective measure to prevent and early diagnosis of CVDs. It applies the disposal metal plated electrodes with the assisting of sticky hydro-gel to acquire high precision signals. ..However, the traditional disposal sticky hydro-gelled metal plate electrodes are not suitable for long-term ECG monitoring. For one thing, the hydrogel has adverse effect on electrode performance when it is dehydrated. For the other, the hydrogel may cause skin allergy or inflammation in long-term application. As alternative to traditional metal plate electrodes, textile electrodes are flexible, comfortable, and have good air and moisture permeability, applied without gel that less prone to skin problems in long-term application. Moreover, textile electrodes are washable, reusable and easy integrated into garments for mobile health monitoring. These advantages will undoubtedly give textile electrodes potential application scenario especially in future home-medicine or tele-medicine...The state-of-the-art textile electrodes can acquire perfect ECG signal comparable to traditional metal plated electrodes with hydro-gel when the subject is in static state, while severely contaminated by motion artifacts during body movement. From the study carried on traditional electrodes, it suggested that the motion artifacts are mainly originate from the skin-electrode interfacial instability and skin deformation induced potentials. However, motion artifacts in textile electrodes may have their own characteristics as the differences in structure and application method compared with traditional metal plate electrodes. Textile electrodes are flexible and apply with no hydro-gel at the skin electrode interface, the contact area may easily be affected by fabric deformation and skin-electrode relative slippage during body movement. So motion artifacts in textile electrodes are much more complicated than traditional metal plate electrodes, especially the noise from skin-electrode interfacial instability which is the main concern of this project. ..In this project, we propose to investigate the motion artifacts from skin-electrode interface by analyzing their mechanical interaction and interfacial electrical properties, as well as characterizing the amplitude of motion artifacts during skin-electrode mechanical interaction. Finally, a skin-electrode interfacial model is built using constant phase element and validated from textile structure, skin-electrode mechanical interaction aspects. By using this model, we expect to optimize the textile structure to fabricate low noise electrodes, to predict the noise amplitude for further de-noising process.

动态心电图（DCG）是心脏疾病预防和诊断的重要手段之一，利用纺织电极监测DCG具有其他类型电极无可比拟的舒适性与易用性优势，然而阻碍纺织电极实际应用的最重要原因是动态噪音问题。本项目以电极与皮肤界面为切入点，从界面动态力学作用、界面电学性能、界面等效电路模型、界面动态噪音机理等方面进行研究。电极-皮肤动态力学作用主要研究人体运动过程中电极与皮肤的接触压力和相对速度；电极-皮肤界面电学性能评价是基于自行研制的电极动态测试平台，电极在相对于皮肤做标准化的、受控的运动时，测量界面动态频率响应特性和动态界面噪音；电极-皮肤界面等效电路模型是基于基本电路元件和常相位角元件建立，并从电极材料、电极结构、动态作用、界面状态等方面进行验证；界面动态噪音机理研究界面动态噪音形成机制，预测电极-皮肤动态作用过程中动态噪音水平。本项目开展将为前端纺织电极的结构优化和后端动态心电图的降噪、去噪提供理论依据。

本项目研究纺织电极-皮肤的动态力学作用与动态噪音间的关系，提出纺织电极-皮肤界面等效电路模型。结果发现：（1）电极-皮肤间的压力为3kPa左右时电极和皮肤接触较稳定。（2）电极-皮肤的接触压力变化与心电信号基线波动间的相关系数为0.9556。（3）电极-皮肤界面阻抗的数量级为1MΩ@1Hz，阻抗随压力波动的范围约为30%。（4）电极-皮肤界面噪音水平在10-20mV之间，与电极直径、接触压力呈负相关，与电极压缩模量、压缩滞后性也明显相关。（5）常相位角元件（CPE）建立的纺织电极-皮肤界面等效电路模型与实验结果高度一致。本项目研究成果对于纺织电极的结构优化，心电监测智能服装的设计，以及动态心电图的降噪具有重要的理论意义。