ECG Signal Quality in Intermittent Long-Term Dry Electrode Recordings with Controlled Motion Artifacts

Wearable long-term monitoring applications are becoming more and more popular in both the consumer and the medical market. In wearable ECG monitoring, the data quality depends on the properties of the electrodes and on how they contact the skin. Dry electrodes do not require any action from the user. They usually do not irritate the skin, and they provide sufficiently high-quality data for ECG monitoring purposes during low-intensity user activity. We investigated prospective motion artifact–resistant dry electrode materials for wearable ECG monitoring. The tested materials were 1) porous: a conductive polymer, conductive silver fabric; and 2) solid: stainless steel, silver, and platinum. ECG was acquired from test subjects in a 10-minute continuous settling test and in a 48-hour intermittent long-term test. In the settling test, the electrodes were stationary, whereas both stationary and controlled motion artifact tests were included in the long-term test. The signal-to-noise ratio (SNR) was used as a figure of merit to quantify the results. Skin-electrode interface impedance was measured to quantify its effect on the ECG, as well as to leverage the dry electrode ECG amplifier design. The SNR of all electrode types increased during the settling test. In the long-term test, the SNR was generally elevated further. The introduction of electrode movement reduced the SNR markedly. Solid electrodes had a higher SNR and lower skin-electrode impedance than porous electrodes. SNR and impedance are negatively associated with each other. In the stationary testing, stainless steel showed the highest SNR, followed by platinum, silver, conductive polymer, and conductive fabric. In the movement testing, the order was platinum, stainless steel, silver, conductive polymer, and conductive fabric. The files include videos showing the instrumentation during ECG and impedance movement testing and an Excel-sheet with the calculated signal-to-noise results and measured impedance norms. Full methods are described in the related research paper of the same name.

可穿戴长期监测应用在消费级与医疗级市场均日益普及。在可穿戴心电（ECG）监测中，数据质量取决于电极自身特性及其与皮肤的接触状态。干式电极无需用户进行额外操作，通常不会刺激皮肤，且在用户低强度活动时，可为心电监测提供足够高质量的数据。本研究针对可穿戴心电监测场景，研究了具备抗运动伪影潜力的干式电极材料。本次测试的材料分为两类：1）多孔型：导电聚合物、导电银织物；2）实心型：不锈钢、银以及铂。研究招募受试对象，分别开展10分钟连续静置测试与48小时间歇性长期测试，以采集心电信号。静置测试中电极保持静止；而长期测试则同时涵盖静止状态与可控运动伪影测试两种工况。本研究以信噪比（SNR）作为品质因数，对测试结果进行量化评估。同时测量皮肤-电极界面阻抗，以量化其对心电信号的影响，并为干式电极的心电放大器设计提供参考依据。所有电极类型的信噪比在静置测试中均有所提升。在长期测试中，信噪比通常会进一步升高。引入电极运动工况后，信噪比会出现显著下降。实心型电极的信噪比高于多孔型电极，且皮肤-电极界面阻抗更低。信噪比与界面阻抗呈负相关关系。在静止工况测试中，不锈钢的信噪比最高，依次为铂、银、导电聚合物与导电织物。而在运动工况测试中，排名依次为铂、不锈钢、银、导电聚合物与导电织物。本次公开的数据集包含两段视频，分别展示心电与阻抗运动测试的实验装置，以及一份包含计算所得信噪比结果与实测阻抗基准值的Excel表格。完整的实验方法可参见同名相关研究论文。