Effect of abdominal layers on surface electroenterogram spectrum

Electroenterogram is the myoelectrical signal of the small bowel. It is the result of a permanent slow wave (low frequency component) and series of spike bursts (high frequency component) that are only present when a bowel contraction occurs. Surface recordings of electroenterogram is one of the potential non-invasive techniques for studying intestinal motility. The aim of this paper is to study the effect of abdominal layers on surface electroenterogram power spectrum. Power spectrum density of internal and external electroenterogram was calculated and divided into five frequency bands: [00.05-0.5 Hz], [0.5-2 Hz], [2-5 Hz], [5-15 Hz] and [15-35 Hz]. Ratio between energy on each frequency band from external and internal signal provide an estimation of the attenuation effect of abdominal layers on surface electroenterogram. Low attenuation coefficient values (round 10^-2-10^-3) manifest severe attenuation of surface recordings of EEnG. Lower attenuation coefficients of high frequency bands suggest a low-pass filtering effect of abdominal wall. Results show moderate variability of attenuation behavior of abdominal layers among recording sessions of individual in study. Greater variability is manifested in comparison among individuals. Particular attenuation effect of individual´s abdominal wall should be considered in order to define absolute intestinal motility indexes based on spectral energy distribution of surface EEnG.