What Can Be Measured from Surface Electrogastrography

The aims of this study were to investigate the detectability of the propagation of the gastric slow wave from the cutaneous electrogastrogram (EGG) and the patterns of the EGG when the gastric slow waves are uncoupled. A mathematical model was established based on the volume conductor theory to simulate the transfer of the serosal gastric slow wave from the stomach to the abdominal surface. A number of computer simulations were conducted using the model, and the periodic cross-correlation function was used to estimate the phase shift between the four channels. It was found that the propagation of the gastric slow wave was detectable from the multichannel EGG signals. The detectability of the propagation was, however, associated with a number of factors, such as the thickness of the abdominal wall and the propagation velocity of the serosal slow wave. The amplitude of the EGG was found to be associated with the coupling/uncoupling and propagation velocity of the gastric slow wave. The amplitude of the EGG increased when the propagation velocity of the gastric slow wave increased. The amplitude of the EGG was substantially decreased when the gastric slow waves were uncoupled. The uncoupling of the gastric slow wave at a frequency of 3 cpm produced dysrhythmias in the EGG, including tachygastria, bradygastria, and arrhythmia. The power spectra of simulated different positional EGG signals showed similar patterns when the gastric slow wave was coupled and different and unpredictable patterns when the gastric slow wave was uncoupled. In conclusion, multichannel EGG recordings may be necessary to obtain more information on gastric slow waves from the abdominal electrodes. The propagation and coupling or uncoupling of the gastric slow wave may be detected from multichannel EGG recordings.