Individualized Perioperative Open Lung Ventilatory Approach in Emergency Abdominal Laparotomy. A Prospective Multicenter Randomized Controlled Trial.

Inclusion Criteria: * Adult men and women ≥18 years of age who underwent emergency laparotomy with the presence of post-induction positive air-test (SpO2 \<97% after a maximum of 15 minutes at FIO2 of 0.21). A SpO2 \<97% at any FIO2 would also be considered a positive air-test. Exclusion Criteria: * 1\) Pregnancy or breast feeding, 2) Moderate or severe ARDS defined, 3) refractory shock, 4) diagnosis or suspected intracranial hypertension (\>15mmHg), 5) mechanical ventilation in the last 15 days (including CPAP), 6) presence of pneumothorax or giant bullae in a chest radiograph or computed tomography (CT), 7) patients participating in another intervention study with the same or similar primary outcome variable.