Stationarity study of the myoelectrical signal recorded from small bowel

Electroenterogram (EEnG) is the myoelectrical signal recorded from small intestine. Due to the relationship between mechanical activity and myoelectrical activity of the intestinal smooth muscle, EEnG could be a solution for quantifying intestinal motility. Motility indexes are traditionally calculated from 1-minute window analysis. However, no prior works have analyzed whether signal properties remain constant or not within this time interval. The aim of present paper is to study time evolution of changes in EEnG spectrum in order to determine if traditional analysis and window length is satisfactory from the signal dynamics point of view. Mechanical and electrical activities are recorded simultaneously in bowel rings (at duodenum, angle of Treitz and jejunum) of three Beagle dogs. Thirteen recording sessions were carried out. A stationary index (SI) based on statistical analysis of time evolution of spectral parameters is defined and calculated over EEnG recording sessions. Results show that myoelectrical signal from bowel muscle is stationary during quiescence periods and maximum contractions periods. However, during irregular contractile activity (i.e. transitions from no-activity to maximum activity, or in fed state) electroenterogram is a non-stationary signal if 1-minute length is chosen for its analysis. Therefore, traditional intestinal motility indexes must be redefined using non-stationary techniques.