Identification of intestinal pacemaker frequency through time-frequency ridge analysis of surface EEnG

The non-invasive monitoring of the frequency of intestinal pacemaker activity (slow wave, SW) has an important diagnostic value. However the presence of noise, physiological interferences and spurious peaks of the spectral estimators can yield to misidentification of SW frequency when using conventional dominant frequency detection method. In this paper, two methods of ridge extraction from the time-frequency distribution of human surface electroenterogram (EEnG) are proposed for the identification and tracking of SW frequency in 13 recording sessions of 120 minutes in 13 healthy volunteers. The minimum average distance method, that includes of information of previous and subsequent windows of analysis, yields the best results in terms of providing ridges that are longer, with less interruptions and with more stable frequency values which better suit the ubiquity and rhythmicity characteristics of the intestinal SW. This technique permits to reduce misinterpretations of intestinal SW frequency which can be of great importance in diagnostic applications of EEnG.