Increases in Intra-abdominal Pressure Affect Pulmonary Compliance

OBJECTIVES: To determine the effect of increased intra-abdominal pressure (IAP) on pulmonary compliance and to determine an effective means to measure IAP. DESIGN: A prospective study. SETTING: An urban tertiary care hospital. PATIENTS: Twenty-six adult patients undergoing laparoscopic cholecystectomy. INTERVENTIONS: Intra-operative management of laparoscopic cholecystectomy requiring endotracheal intubation with general anesthesia, nasogastric and urinary bladder catheters, and position changes. Additional interventions included use of a rectal manometer and a respiratory pressure module inserted within the ventilator circuit. MAIN OUTCOME MEASURES: Correlation of changes in IAP with changes in dynamic pulmonary compliance, measured as tidal volume/(end inspiratory pressure--end expiratory pressure) and comparison of three different measurement techniques (bladder, rectal, and gastric) with a standard technique (insufflation pressure) in three different positions (supine, Trendelenburg's, and reverse Trendelenburg's). RESULTS: Compliance was significantly related to insufflation pressure (P < .001) by analysis of variance. In the gas insufflation model, the mean increment in bladder pressure reflected most closely the IAP increment in the supine 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 and gastric pressures were also position dependent and technically less reliable. CONCLUSIONS: Increased IAP has a major influence on pulmonary compliance (50% decrease at 16 mm Hg). Measurements of IAP by intraorgan manometry are position dependent and may not accurately reflect the intraperitoneal pressure.