Accounting for SNR in an Algorithm Using Wavelet Transform to Remove ECG Interference from EMG Signals

When the electromyography (EMG) signal is acquired from muscles in the torso, the electrocardiography (ECG) signal coming from heart activity can interfere. As a result, the EMG signal can be contaminated during data collection. In this paper, a technique based on discrete stationary wavelet transform (DSWT) is proposed to remove ECG interference from the EMG signal while taking into account the signal-to-noise ratio (SNR). The contaminated EMG signal is decomposed using 5-level DSWT with the Symlet wavelet function. The coefficients for levels 4 and 5, which are contaminated by ECG, are set to zero when their absolute values are less than or equal to a threshold determined for each SNR level. A clean EMG signal can then be obtained by inverse DSWT mapping of the new thresholded coefficients. We evaluated the performance of the proposed algorithm using simulated EMG contaminated with both simulated and real ECG signals, at 9 SNR levels from [Formula: see text]20 to 20[Formula: see text]dB with 5[Formula: see text]dB increments. The performance based on mean absolute error, correlation coefficient and relative error shows that the DSWT method is better than a high-pass filter.

Electrocardiogram Interference: A Thing of the Past?

This paper focuses on the problem of high and/or imbalanced electrode-skin impedances changing electrocardiogram (ECG) morphology. After reproducing ECG interference in a controlled laboratory setting—similar to what was observed during cardiopulmonary bypass surgery— and then understanding the cause, this knowledge was applied to clinical settings. Most interference was reduced by using electrode impedance meters and consistent skin prep.