Laplacian electrode to record small bowel myoelectrical activity from abdominal surface

The aim of this study is to develop a system to record small intestine myoelectric activity (electroenterogram) from abdominal surface. The difficult anatomic access is a technical problem for monitoring intestinal activity, therefore most methods are invasive. It results in many problems like the low amplitude of the signal recorded and physiological interferences captured. In order to avoid these troubles, and to estimate the location of the small intestine point whose activity is being recorded, a tripolar concentric ring electrode has been implemented in bipolar configuration (TCB). This electrode is based on Laplacian theory. The signals recorded by TCB electrode were analysed and contrasted to the internal myoelectric signal and to the signals obtained from the body surface by using two unipolar electrodes. A surgical intervention was carried out in a Beagle dog to suture a bipolar electrode at the bowel serosa. The signals recorded were acquired and preprocessed to carry out a density power spectral analysis (periodogram). The electroenterogram captured by TCB electrode were free of ECG interferences. Its periodogram revealed a peak near 0.25 Hz, corresponding to the slow wave frequency (13 to 18 cpm), while it rejected a peak at 0.4 Hz due to breath interference. These results show the utility of the TCB electrode in order to remove interferences in abdominal surface electroenterogram acquisitions.