Autocorrelation, cross correlation and coherence analyses of the electrical activity of the human stomach in the postoperative period.

Electrical potentials generated by the stomach have been well categorized. They vary in amplitude, shape, frequency and time relationships and may be contaminated by electrical activity from other organs. In addition to visual observation, this investigation used methods of autocorrelation and cross correlation, spectral analysis and coherence determinations to refine and numerically characterize gastric electrical potentials. Bipolar Teflon coated electrode wires were brought out through the abdominal wall in six patients, four of whom underwent fundoplication, one of whom underwent cholecystectomy and one of whom underwent portacaval shunt. Recordings were obtained until the ninth postoperative day using differential preamplifiers, an oscilloscope and a dual channel tape recorder. Oscilloscope displays were photographed, and the outputs of the tape recorder were filtered in the analog mode. Similar recordings were also obtained postoperatively in a patient with gastric stasis, and a surface electrode was used to record the gastric electrical activity of a normal volunteer. The propagation time, electrical control activity frequencies and bioelectrical dependence or independence between the two measuring sites were clearly differentiated by these methods. This method offers a safe and feasible way of recording and analyzing the electrical activity of the human stomach in the postoperative period with statistically specified reliability. This is accomplished through temporarily implanted wires, and, potentially, from the surface of the body, even during electrical interference.