Randomized controlled trial, comparing two groups of 40 patients each scheduled for open major abdominal surgery. The intervention group was ventilated with a protective strategy consisting on a low Tidal volume (Vt) (6ml/kg of predicted body weight (PBW)), positive end expiratory pressure (PEEP) = 10 cm H2O and recruitment manoeuvres (RM) after disconnection from the ventilator, the control group had classic ventilation (Vt = 8 ml/kg of PBW, PEEP = 4 cmH2O and no RM).

This randomized controlled trial, was approved by the institutional ethics committee of our hospital. Informed consent was obtained from all the participants before randomization. Investigators included 80 patients (40 in each group), ASA I or II, planned for open abdominal surgery lasting more than 2 hours under general anesthesia.

Patients were not included if they had specially acute respiratory disease, severe asthma or emphysema, sleep apnea syndrome, septic shock and body mass index (BMI) < 16 or > 35 Kg/m2. Participants were excluded in case of serious peroperative anesthetic complications or hemorrhagic shock.

Primary endpoint was postoperative pulmonary complications occurring within the first 7 days after surgery (defined as hypoxemia, Broncho-pneumopathy, pulmonary infiltrate, acute respiratory distress syndrome, atelectasis, pleural effusion).

Secondary endpoints for all participants were intra-operative complications (change in SpO2 when dropped less than 90%, hypotension <90 mmHg lasting more than 3 min, need for vasopressor administration, new arrhythmia), postoperative extrapulmonary complications (septic shock, postoperative surgical complications, heart disease complications). Investigators recorded for all participants length of hospital stay and mortality rate were .

Investigators randomly allocated patients before entering to the operating room to:

• Control Group (CG): patients ventilated with Vt of 8 ml/kg of predicted body weight (PBW), a low level of PEEP (4 cm H2O) without RM.
• Protective Ventilation Group (PVG): patients ventilated with a low Vt of 6 ml/Kg of PBW, a high level of PEEP (10 cm H2O), RMs applied after intubation, before extubation and in case of disconnection from the ventilator.

Other ventilation settings, type of anesthesia, fluid administration and post operative pain management were standardized.

In the postoperative period, investigators daily assessed clinical examination and arterial blood gas if pulse oximetry dropped. For all participants, a chest X ray, blood count creatinine and C reactive protein were done at day 1 and day 3.

Data were presented as means and standard deviation [SD] or frequencies. Statistical analyses were performed using SPSS statistical software version 20.0. A p-value of 0.05 was considered significant.

Inclusion Criteria:

• ASA I or II, planned for open abdominal surgery lasting more than 2 hours under general anesthesia

Exclusion Criteria:

• Patients were not included if they had specially acute respiratory disease, severe asthma or emphysema, sleep apnea syndrome, septic shock and BMI < 16 or > 35 Kg/m2. They were excluded in case of serious peroperative anesthetic complications or hemorrhagic shock.