ASSESSMENT OF COLONIC PRESSURE VOLUME RELATIONSHIPS IN HEALTHY VOLUNTEERS

Pressure-volume (p-v) relationships (or "compliance curves") obtained during colonic balloon distention are used to assess drug effects. P-v curves are also applied to characterize biomechanical properties such as viscoelasticity. This is possible if the experimental conditions are consistent with the assumptions of biophysical models. Our aims were: i) To demonstrate that the deforming stress (i.e. intraballoon pressure) and tissue tension (represented by balloon volume) are in equilibrium (or "steady state") during colonic balloon distention in humans; to assess ii) the intraindividual reproducibility of p-v relationships, iii) the effect of altering the rate of inflation on p-v curves and iv) differences between ascending (Asc) and descending (Des) p-v curves, i.e. hysteresis. Methods: A barostat-balloon was positioned in the cleansed descending colon in 15 healthy volunteers. During each p-v curve, the barostat balloon was inflated (Asc curve) and subsequently deflated (Des curve) in 4 mmHg steps from 0-44 mmHg. At each step, balloon pressure was maintained until balloon volume stabilized, i.e. fluctuation