Ventilation with high versus low peep levels during general anaesthesia for open abdominal surgery does not affect postoperative spirometry: A randomised clinical trial

Background: Invasive mechanical ventilation during general anaesthesia for surgery typically causes atelectasis and impairs postoperative lung function. Objective: We investigated the effect of intraoperative ventilation with high positive end-expiratory pressure (PEEP) and recruitment manoeuvres (RMs) on postoperative spirometry. Design: This was a preplanned, single-centre substudy of an international multicentre randomised controlled trial, the PROVHILO trial. Setting: University hospital from November 2011 to January 2013. Patients: Nonobese patients scheduled for major abdominal surgery at a high risk of postoperative pulmonary complications (PPCs). Intervention: Intraoperative low tidal volume ventilation with PEEP levels of 12 cmH2O and RM (the high PEEP group) or with PEEP levels of 2 cmH2O or less without RM (the low PEEP group). Main Outcome Measures: Time-weighted averages (TWAs) of the forced expiratory volume in 1 s (FEV1) and the forced vital capacity (FVC) up to postoperative day five. Results: Thirty-one patients were allocated to the high PEEP group and 32 to the low PEEP group. No postoperative spirometry test results were available for 6 patients. In both groups, TWA of FEV1 and FVC until postoperative day five were lower than preoperative values. Postoperative spirometry test results were not different between the high and low PEEP group; Data are median [interquartile range], TWA FVC 1.8 [1.6 to 2.4] versus 1.7 [1.2 to 2.4] l (P = NS) and TWA FEV1 1.2 [1.1 to 2.5] versus 1.2 [0.9 to 1.9] l (P = NS). Patients who developed PPCs had lower FEV1 and FVC on postoperative day five; 1.1 [0.9 to 1.6] versus 1.6 [1.4 to 1.9] l (P = 0.001) and 1.6 [1.2 to 2.6] versus 2.3 [1.7 to 2.6] l (P = 0.036), respectively. Conclusion: Postoperative spirometry is not affected by PEEP and RM during intraoperative ventilation for open abdominal surgery in nonobese patients at a high risk of PPCs, but rather is associated with the development of PPCs