BACKGROUND: Conventional laparoscopic surgery requires a pneumoperitoneum with CO₂ and a change in the patient positioning. Because of the pneumoperitoneum, the peak and plateau airway pressure and respiratory compliances can change compared with initial value. Obesity also affects the patient's respiratory mechanics. The aim of this study was to determine the correlation between the patient's positioning and a pneumoperitoneum with the changes in the respiratory mechanics, and to examine the relationship between the patient's BMI and the changes in therespiratory mechanics.

METHODS: Fifty patients undergoing a laparoscopic cholecyctectomy and had no pulmonary pathology were enrolled in this study. The patient's basic data were obtained and the Body Mass Index (BMI) was calculateed. Conventional induction and maintenance of anesthesia were carried out, and each patient was fully relaxed with a rocuronium during the procedure. The change in the respiratory mechanics was checked 5 minutes after induction, the time that the pneumoperitoneum had been induced, and the end of surgery with the supine and 10° tilting of the Trendelenburg and reverse Trendelenburg position.

RESULTS: There was approximately a 30% reduction in dynamic compliances before and after inducing pneumoperitoneum with CO₂ at each position and a negative correlation between the BMI and the dynamic compliance. There were no significant differences in the respiratory mechanics withe the different patient positions.

CONCLUSIONS: The respiratory mechanics are influenced by an increase in the patient's BMI and induced pneumoperitoneum but not by a 10° tilting of the reverse Trendelenburg and Trendelenburg position.