Cardiac surgery with cardiopulmonary bypass (CPB) frequently induces post-operative respiratory dysfunction. The post-operative pulmonary complications (PPCs) significantly increase the peri-operative morbidity and require invasive treatments during longer and more expensive ICU stays. A specific pathophysiology involving general anesthesia and CPB-related factors (inflammation, pulmonary ischemia) has been clearly demonstrated and pulmonary atelectasis seems to play a central role in the occurence of these PPCs. The open lung approach is a ventilation strategy that aims to "open the lung and keep it open" using different ventilatory settings. The efficacy of that strategy is not demonstrated in the global surgical population. However, its application in the perioperative care of cardiac surgery patients could be of great interest by counteracting the development of atelectasis.

The purpose of this multicentre, double blinded, randomized controlled study is to evaluate the influence of a perioperative multimodal protective ventilation strategy based on the "open lung approach" on postoperative outcomes during the first 7 days following cardiac surgery. Participating centres will include 500 adult patients undergoing scheduled on-pump cardiac surgery. The open lung approach will combine recruitment maneuvers (RM), positive end expiratory pressure (PEEP) at 8 cmH2O from intubation to detubation and continuation of ultraprotective ventilation during CPB. It will be compared to a conventional approach without RM, with PEEP at 2 cmH2O and discontinuation of ventilation during CPB. The primary endpoint is any post-operative pulmonary complication. The secondary endpoints are any post-operative extra-pulmonary complications and the number of ICU-free days to day 7.

Inclusion Criteria:

• Cardiac surgery planned with CPB and sternotomy.
• Age > 18 years old.

Exclusion Criteria:

• Urgent surgery : cardiac transplantation, aortic dissection, active endocarditis.
• Aortic arch surgery with circulatory arrest.
• LVAD surgery.
• Acute or chronic preoperative hypoxemia (PaO2 < 65 mmHg in air).
• Preoperative shock state requiring catecholamines.
• LVEF < 40%.
• Pulmonary hypertension with systolic pulmonary artery pressure > 50 mmHg.
• Severe right ventricular dysfunction (TDI tricuspid annular systolic velocity < 10 cm.s-1).
• Chronic kidney disease (Glomerular filtration rate < 30 mL/min).
• Body Mass Index > 35kg/m2.
• Patient's refusal.