Retrieval of the small intestinal pressure from time-frequency analysis of the electroenterogram

The aim of this work is to analyse the electrical signal from the serosa of the small bowel in the time-frequency (t-f) plane. This signal is named the electroenterogram, and it is the result of a slow wave (SW) and a spike burst (SE). Only the latter represents intestinal pressure, but SW gives the maximum rhythm of the contractions. Three joint records of electroenterogram and intestinal wall contractions were carried out (duodenum, angle of Treitz and jejunum) on two dogs. Each record is 4 hours long. Six t-f distributions were calculated over a 1 minute period of the electroenterogram: Wigner-Ville (WVD), Choi-Williams (CWD), Zhao-Atlas-Marks (ZAM), and 3 spectrograms with different window lengths. CWD is the best distribution for graphical displaying in order to recognise the electrical signal of the small bowel. However, spectrograms are better than CWD for obtaining the time marginal and the local mean frequency. Both temporal functions are highly correlated with intestinal pressure.