Origin of changes in the epigastric impedance signal as determined by a three-dimensional model.

The impedance technique can be used for the noninvasive monitoring of the stomach, with the epigastric impedance signal being a function of the position and configuration of the electrodes. The changes observed could be due to meal resistivity, meal volume and contractions of the gastric smooth muscles. The effect of these various factors on the epigastric impedance signal was determined for several electrode configurations using a three-dimensional model of the abdomen. When the voltage sensing electrodes are located close to the current electrodes, the signal varies linearly with meal volume. The relationship between meal resistivity and the epigastric impedance signal is nonlinear. The impedance signal varies linearly with the contractions of the circular smooth muscles of the stomach.