Human surface electrogastrograms: ac and dc measurements.

Both ac and dc abdominal electrical recordings were made on fasted and fed human subjects using a spatial array of 18 cutaneous, biopotential electrodes. Controlled skin puncture minimized cutaneous potentials. Pregelling electrodes minimized drift. The recording sessions were between two and three hours in length. We determined the optimal location for ac recording of a 3 cpm wave at a location on the midline approximately 5 cm below the xiphoid process. Seven cpm waves were also observed in one individual at the same location. The dc values were fed into a Hewlett Packard 1000 computer which interpolated the intermediate values and plotted two-dimensional contour plots which were examined visually. The right abdominal surface was typically 1.8 mV more negative than the left for prefeeding. The left abdominal surface was typically 4.6 mV more negative than the right for postfeeding. We propose an electrical model that explains these results during the fasted state.