Adaptive cancellation of the ECG interference in external electroenterogram

The small bowel myoelectrical activity (electroenterogram) can be recorded placing electrodes on the abdominal skin. This surface signal contains noise and interferences. The most significant interferences in the surface electroenterogram are the respiratory artifact and the electrocardiogram signal (ECG). Conventional filtering cannot be applied to eliminate these interferences because the signal and interferences have overlap spectra. The goal of this paper is to cancel the ECG interference from surface register through adaptive filtering. Internal and external recordings were acquired simultaneously from four Beagle dogs. In this study three different configurations of adaptive filters (based on LMS algorithm) were tested for ECG cancellation from external electroenterogram. Spectral parameters were calculated from surface recording and filtered surface recordings: energy (EF), energy over two Hz (EF2), mean frequency (FM) and frequency standard deviation (FSD). Correlation between surface recording parameters and internal motility index (IMI) is analysed. Results show that spectral parameter EF2 of filtered external electroenterogram presents high correlation coefficient value. The adaptive interference cancellation is a very efficient method to solve the problem when signal and interference have overlap spectra. Small bowel motility can be studied through filtered external register of the electroenterogram without need of surgical intervention.