Background: The cardiopulmonary effects of the combination of abdominal and thoracic pressures in humans have not been well delineated. Objective: To study the cardiopulmonary effects of 15 mm Hg of intra-abdominal pressure in the presence and absence of 10 cm H2O of positive end-expiratory pressure (PEEP). Design: Prospective. Setting: University hospital. Methods: Nine patients undergoing laparoscopic cholecystectomy had pulmonary compliance, cardiac output, exhaled carbon dioxide, and preload (left ventricular end- diastolic volume) determined at 4 points while undergoing ventilation with (1) no PEEP before pneumoperitoneum; (2) 10 cm H2O of PEEP and no pneumoperitoneum; (3) no PEEP and 15 mm Hg of pneumoperitoneum; and (4) 10 cm H2O of PEEP and 15 mm Hg of pneumoperitoneum. Preload and cardiac output were determined by means of transesophageal echocardiography. Pulmonary compliance and exhaled carbon dioxide were determined by an attachment to the end of the endotracheal tube. Main Outcome Measures: Preload, cardiac output, exhaled carbon dioxide, and pulmonary compliance. Results: There was no significant change from baseline in preload, cardiac output, or pulmonary compliance when either PEEP or pneumoperitoneum was applied separately. However, there was a significant decrease in preload (P<.01), cardiac output (P = .01), and exhaled carbon dioxide (P = .04) when PEEP and pneumoperitoneum were applied together. Pulmonary compliance was not significantly affected at any of these points. Conclusions: There was a significant reduction in preload and cardiac output when there was intra- abdominal pressure of 15 mm Hg in the presence of 10 cm H2O of PEEP. This combination of pressures may pose a contraindication to laparoscopic surgery.
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