Quantitative evaluation of the dynamics of external factors influencing canine gastric electrical activity before and after uncoupling.

Electrical uncoupling could be a major source of gastric motility abnormalities. Non-invasive recognition of the onsets of gastric electrical uncoupling could become an avenue for early detection of gastric motor abnormalities. Cutaneous recordings of gastric electrical activity (GEA), known as electrogastrograms (EGG), are dynamically influenced by a variety of external factors, jeopardizing their reliability. In the present study the dynamics of external factors influencing both internal GEA and EGG during surgically induced gastric electrical uncoupling are quantitatively explored. Sixteen anaesthesized dogs underwent implantation of six stainless steel pairs of bipolar electrodes, positioned among the sites for future divisions of the stomach into three equal sections. In the basal state and after each surgical cut, simultaneous 30-min recordings of six internal GEA and eight EGG channels were performed in each dog. The signals were filtered, conditioned and digitized to obtain their one-dimensional representations in the sampled time domain. These representations were regarded as particular projections of multidimensional dynamic vectors located in the phase space, which incorporated both the dynamics of the electrical processes taking place in the stomach and the dynamic interactions between the external factors influencing the recordings. Embedding dimensions in the phase space were considered quantitative expressions of all these factors. Comparative statistical evaluation of the dynamics of the embedding dimensions for both internal GEA and EGG channels was performed. Although the number of embedding dimensions did not change significantly with the introduction of gradual uncoupling both in the internal GEA and in the EGG channels, opposite tendencies towards increment in the former and decrement in the latter were noted. After the introduction of severe uncoupling, cutaneous embedding dimensions became very similar to the internal ones. A significant number of external factors influencing EGG recordings preclude reliable recognition of mild electrical uncoupling from EGG.