Method and apparatus for pressure-controlled distension of the lower gastrointestinal tract

Despite the relevance of visceral perception in the lower gastrointestinal tract to clinical research, especially for diagnosis of functional diseases or neurological derangements of the bowel, precise techniques to evaluate these perceptual processes and mechanical properties of the bowel wall were lacking until recently. Such techniques must include the application of well-defined stimuli and the recording of physiological reactions. A probe was developed which causes minimal discomfort to the subject and is therefore suitable for psychophysical examinations. It can be easily modified for different applications. Stimuli are applied by inflating a balloon, which distends the colon or rectum wall. Prestretching of the balloon material before mounting it on the probe results in monotonic and flat pressure characteristics. Balloon volume is nearly independent from external pressure, within 5% under physiological conditions. Dynamic performance of the balloon is sufficient for studies on the influence of stimulus shape. A microcomputer-controlled pump-system presents precise stimuli within a wide range of volume and inflation rate. A stepping motor is the heart of this system and allows to define exact values for volume and pumping rate without the use of complicated controlling elements. Menu-driven programs allow complex stimulus shapes and sequences. The method and apparatus described above have been successfully used in clinical and basic psychophysiological studies.