INCREASES IN INTRAABDOMINAL PRESSURE AFFECT PULMONARY COMPLIANCE

Objectives: To determine the effect of increased intraabdominal pressu re (IAP) on pulmonary compliance and to determine an effective means t o measure IAP. Design: A prospective study. Setting: An urban tertiary care hospital. Patients: Twenty-six adult patients undergoing laparos copic cholecystectomy. Interventions: Intra-operative management of la paroscopic cholecystectomy requiring endotracheal intubation with gene ral anesthesia, nasogastric and urinary bladder catheters, and positio n changes. Additional interventions included use of a rectal manometer and a respiratory pressure module inserted within the ventilator circ uit. Main Outcome Measures: Correlation of changes in IAP with changes in dynamic pulmonary compliance, measured as tidal volume/(end inspir atory pressure - end expiratory pressure) and comparison of three diff erent measurement techniques (bladder, rectal, and gastric) with a sta ndard technique (insufflation pressure) in three different positions ( supine, Trendelenburg's, and reverse Trendelenburg's). Results: Compli ance was significantly related to insufflation pressure (P<.001) by an alysis of variance. In the gas insufflation model, the mean increment in bladder pressure reflected most closely the IAP increment in the su pine position (5.7 vs 6 mm Hg) but not in the Trendelenburg (2.1 vs 6 mm Hg) and reverse Trendelenburg positions (3.4 vs 6 mm Hg). Rectal an d gastric pressures were also position dependent and technically less reliable. Conclusions: Increased IAP has a major influence on pulmonar y compliance (50% decrease at 16 mm Hg). Measurements of IAP by intrao rgan manometry are position dependent and may not accurately reflect t he intraperitoneal pressure.