The computer as referee in the analysis of human small bowel motility

Abstract

The aim of this study was to determine whether visual analysis of graphic records of small bowel motility is a reliable method of discriminating pressure events caused by bowel wall contraction from those of extraenteric origin and to compare this method with computerized analysis. Each of six independent observers was supplied with the same pair of records of 1 h of fasting diurnal duodenojejunal motility, acquired with a 3-channel ambulant data-logging system; one record included many artifacts due to body movement while the other did not. The observers were asked to identify and classify pressure events and to measure the duration and amplitude of "true" contractions. A computer program for on-line analysis is described; the algorithm was designed to overcome the problems of a variable baseline and sudden changes in pressure due to body movements that are unavoidable in prolonged recording from the small bowel of ambulant subjects. For regular contractions (phase III of migrating motor complex) there was good agreement between observers but not for irregular contractions, particularly when movement artifacts were abundant. When the observers were asked to repeat the analysis 6 mo later, there was poor agreement with their original identification of irregular contractions and artifacts. There was, however, good agreement between the computer analysis, which was totally reproducible, and the median decisions of the observer group; this agreement supports the validity of our computer algorithm. We conclude that computer analysis is not merely a valuable ergonomic aid for analysis of large quantity of data acquired in prolonged ambulatory monitoring, but also that, even for brief recordings, it provides a standard of reproducibility unmatched by "expert" inspection. Visual analysis is unreliable and thus susceptible to subjective bias; this may, in part, account for conflicting reports of small bowel motility under similar conditions reported by different workers in our own and other laboratories.