Intraoperatively ventilated patients with a tidal volume (VT) of 5-6ml / kg of ideal body weight and respiratory rate to maintain normal carbon dioxide. After intubation, in all patients will be performed an alveolar recruitment maneuver (MRA) and a PEEP titration trial (see Calculation of optimal PEEP). Every 40 minutes will be assessed the need to adjust the level of PEEP by evaluating the dynamic compliance of the respiratory system (Crs). Faced with a decline in Crs> 10% a new MRA and optimal PEEP setting will be assessed.

Postoperatively, high flow oxygen therapy will be individually indicated by evaluating peripheral oxygen saturation.

Intraoperatively ventilated patients with a tidal volume of 5-6 ml / kg of ideal body weightand respiratory rate to maintain normal carbon dioxide, PEEP 5 cmH2O. In this group no recruitment maneuvers or optimal PEEP setting will be performed.

Postoperatively, standard oxygen therapy.

To start the Alveolar Recruitment Maneuver (ARM) the ventilatory mode will be changed to pressure-controlled mode (PCV) with 20 cmH2O pressure control ventilation. A respiratory rate (RR) of 15 rpm, inspiration: expiration ratio of 1:1, FiO2 of 0.8 and PEEP of 5 cmH2O. The PEEP level will be increased in 5 cmH2O steps every 10 respiratory cycles, increasing to 15 cycles in the last level of PEEP (20 cmH2O), getting an opening pressure at 40 cmH2O airway (duration of the maneuver: 160 sec.)

composite of pulmonary infection, severe respiratory failure, acute respiratory distress syndrome, pneumothorax, bronchopleural fistula, atelectasis requiring bronchoscopy, empyema.

suspicion of pulmonary infection, mild acute respiratory failure, severe respiratory failure, acute respiratory distress syndrome