RESPIRATION AND THE AIRWAY Pressure-controlled ventilation improves oxygenation during laparoscopic obesity surgery compared with volume-controlled ventilation

Background. We compared pressure and volume-controlled ventilation (PCV and VCV) in morbidly obese patients undergoing laparoscopic gastric banding surgery. Methods. Thirty-six patients, BMI.35 kg m22, no major obstructive or restrictive respiratory disorder, and PaCO2,6.0 kPa, were randomized to receive either VCV or PCV during the surgery. Ventilation settings followed two distinct algorithms aiming to maintain end-tidal CO2 (E0CO2) between 4.40 and 4.66 kPa and plateau pressure (Pplateau) as low as possible. Primary outcome variable was peroperative Pplateau. Secondary outcomes were PaO2 (FIO2 at 0.6 in each group) and PaCO2 during surgery and 2 h after extubation. Pressure, flow, and volume time curves were recorded. Results. There were no significant differences in patient characteristics and co-morbidity in the two groups. Mean pH, PaO2, SaO2, and the PaO2/FIO2 ratio were higher in the PCV group, whereas PaCO2 and the E 0 CO2-PaCO2 gradient were lower (all P,0.05). Ventilation variables, includ- ing plateau and mean airway pressures, anaesthesia-related variables, and postoperative cardio- vascular variables, blood gases, and morphine requirements after the operation were similar. Conclusions. The changes in oxygenation can only be explained by an improvement in the lungs ventilation/perfusion ratio. The decelerating inspiratory flow used in PCV generates higher instantaneous flow peaks and may allow a better alveolar recruitment. PCV improves oxygenation without any side-effects. Br J Anaesth 2008; 100: 709-16