Identification of the slow wave of small bowel myoelectrical activity by surface recording

The bioelectrical signal (electroenterogram) is recorded at the abdominal surface of Beagle dogs with the aim of detecting the slow wave of small bowel myoelectrical activity. Electroenterogram comprises two signals: the slow wave, which is permanently present and establishes the maximum rate of intestinal contraction, and a series of rapid activity peaks generated at the plateau of the slow wave when the small bowel contracts. Two biosignals were recorded using bipolar electrodes: the internal myoelectric signal at a point of the jejunum serosa, and the bioelectric signal at the abdominal wall. The coherence function was used to evaluate the relation between the spectral contents of the two signals (internal and external). The results show high coherence function values for frequencies of under 2 Hz. A maximum was even detected for a frequency round 0.3 Hz, corresponding to the frequency of the slow wave (between 16 and 19 cycles/min.). Based on the coherence function, it is shown that the signal recorded at the abdominal surface is closely related to the slow wave component of the internal signal. The model employed therefore offers a noninvasive technique for recording small bowel myoelectrical activity.