The hypothesis of this study is that the "Open lung approach" ( recruitment and PEEP) during general anaesthesia reduces atelectasis formation and improves respiratory function in the immediate post-operative period after major abdominal surgery.

This is a prospective, randomized, controlled clinical-trial,performed in patients undergoing major abdominal surgery, to compare the effects on the post-operative pulmonary complications of two different intraoperative ventilatory strategies during general anaesthesia: 1- Control Group: PEEP 0 cmH2O without recruitment manoeuvre; 2- Treatment Group:recruitment manoeuvre (after intubation and before extubation) and PEEP 10 cmH2O In the post-operative period the following variables will be recorded at the first, third and fifth postoperative day: 1- Gas-exchange in air; 2- Chest X-ray for atelectasis evaluation; 3- signs of pulmonary complication (cough, secretions, dyspnea, thoracic pain)

Inclusion Criteria:

• Patients with ASA 1, 2 and 3
• Age higher than 18 years
• Major abdominal surgery
• General anesthesia

Exclusion Criteria:

• COPD with FEV1 lower than 50%
• Ischemic cardiopathy
• Loco-regional anesthesia alone
• Minor abdominal surgery
• Laparoscopic surgery