The effect of laparoscopic cholecystectomy on respiratory compliance as determined by continuous spirometry

Study objective: To evaluate the effect of pneumoperitoneum on dynamic compliance during laparoscopic cholecystectomy with continuous spirometry. Design: Prospective, open clinical study with the patients serving as their own controls. Setting: Operating room at a university hospital. Patients: II ASA status I and II patients scheduled for elective laparoscopic cholecystectomy. Interventions: Pneumoperitoneum up to an intraabdominal pressure of 12 mmHg was created with carbon dioxide (CO2) insufflation. Thereafter, the patients were placed in a position combining a head-up hilt with a left side down lateral tilt, for dissection of the gallbladder. Steady levels of anesthesia and neuromuscular block, as well as a constant tidal volume of ventilation, were maintained throughout the procedure. Measurements and Main Results: Airway pressures and respiratory volumes were continuously measured. Compliance was calculated by dividing expiratory tidal volume by end inspiratory pressure, and was displayed as a pressure-volume loop. After the creation of pneumoperitoneum, end-inspiratory airway pressure increased by 40%, and compliance decreased by 30%. These levels remained unchanged during surgery with the patient in a head-up and left side down lateral tilt position. After release of intraabdominal pressure, inspiratory airway pressure and compliance returned to control levels. The pressure-volume loop sloped to the right and its horizontal diameter was elongated during pneumoperitoneum. The new configuration was maintained until the loop returned to the control shape after evacuation of the pneumoperitoneum. Conclusions: Increased intraabdominal pressure during laparoscopic cholecystectomy causes a significant, but fully reversible, decrease in dynamic compliance. On-line spirometry with a graphic display of the pressure-volume loop facilitates the immediate discovery of these alterations.