METHODS FOR STUDYING INTESTINAL SENSITIVITY AND COMPLIANCE - IN-VITROSTUDIES OF BALLOONS AND A BAROSTAT

The aim of this study was to compare in vitro various methods for reco rding intestinal sensitivity and compliance. Relationships between vol ume and pressure were determined in segments of penrose tubing and pig gut ('artificial intestine') using pressure increments of 2 mmHg (0-2 4 mmHg). We tested two direct methods of distension of the entire segm ents (by syringe inflation and the Mayo barostat); we also used three different balloon devices for indirect distension (a 10 cm polyethylen e barostat bag, a 10 cm latex condom balloon and a 6 cm latex condom b alloon). Maximal distending diameters of the recording systems were me asured by injecting from 0 to 160 mL of air. The elastic properties of the balloons were also tested by distensions in air and in rigid tube s. All recording systems accurately detected a lesser compliance of th e penrose drain as compared to pig gut. In absolute terms, only the co mpliance measured with a polyethylene barostat bag distended with a sy ringe was not different from the compliance of the segment as measured directly. The bellows of our barostat and the latex balloons had sign ificant intrinsic compliances which interfered with the recorded press ure-volume curves. On the other hand, highly compliant plastic bags re corded most faithfully the compliance of artificial gut and that of no ncompliant rigid tubes. For comparable volumes of distension, external diameters were larger with the 6 cm latex balloon than with the 10 cm latex balloon or the 10 cm polyethylene barostat balloon. A polyethyl ene bag distended with a non-compliant air injector (syringe) reflecte d most accurately the pressure-volume relationships of tubular structu res. The different maximal diameters assumed by the three distending d evices may explain, in part, why lower Volumes of distension are requi red to elicit symptoms with smaller distending balloons in vivo.