Development of a Technique for Cancelling Motion Artifact in Ambulatory ECG Monitoring System

ECG is a electrical signal generated by the heart and has a regular rhythm. ECG cycle, however, change depending on the person´s activities and heart-related disorders. Therefore, waveform of the ECG signal can be analyzed to assess cardiac abnormalities and lesion of the heart, infer into pathological and biological mechanisms of the heart, and diagnose for various cardiac disorders. ECG enables non-invasive measuring and contains an abundance of health information. That said, this paper discusses a study concerning development of a highly convenient ECG monitoring system. Realization of such monitoring system required development of a portable, miniature, battery-powered, low power consumption, and wireless ECG measuring system featuring belt-type ECG leads worn around the chest. A Zigbee-compatible wireless sensor node was used for wireless transmission of measured ECG data, and a ultra low power consumption wireless data communications units were also developed. And then a monitoring program was coded to enable ECG signal monitoring from a personal computer. Ambulatory ECG measuring is often associated with motion artifact that forms as the subject moves about his or her daily life. Motion artifact´s frequency characteristic is that it varies depending on the type of movement. Therefore, an adaptive filter was used to cancel the changing motion artifact and thereby minimize movement-induced motion artifact. Test results confirm that using the ECG monitoring system proposed herein makes it possible to measure ECG signals in non-restrained environments.