Individualized Perioperative Open Lung Ventilatory Strategy

Inclusion Criteria: * Age not less than 18 * Risk of postoperative pulmonary complication moderate-high defined by a score ≥ 26 on the risk scale ARISCAT (based on the analysis of seven factors, where a score between 26 and 44 points defines a moderate risk, and a score\> 44 points define a high risk, included in the Information Booklet Investigator). * Planned abdominal surgery\> 2 hours. * Signed informed consent for participation in the study. Exclusion Criteria: * Age less than 18 years. * Pregnant or breast-feeding. * Patients with BMI \>35. * Syndrome of moderate or severe respiratory distress: PaO2/FiO2 \< 200 mmHg. * Heart failure: NYHA IV. * Hemodynamic failure: CI \<2.5 L/min/m2 and / or requirements before surgery ionotropic support. * Diagnosis or suspicion of intracranial hypertension (intracranial pressure\> 15 mmHg). * Mechanical ventilation in the last 15 days. * Presence of pneumothorax. Presence of giant bullae on chest radiography or computed tomography (CT). * Patient with preoperatively CPAP. * Participation in another experimental protocol at the time of intervention selection.