One-lung ventilation (OLV) with resting of the contralateral lung may be required to allow or facilitate thoracic surgery. However, OLV can result in severe hypoxemia, requiring a mechanical ventilation approach that is able to maintain adequate gas exchange, while protecting the lungs against postoperative pulmonary complications (PPCs). During OLV, the use of lower tidal volumes is helpful to avoid over-distension, but can result in increased atelectasis and repetitive collapse-and-reopening of lung units, particularly at low levels of positive end-expiratory pressure (PEEP).

Anesthesiologists inconsistently use PEEP and recruitment maneuvers (RM) in the hope that this may improve oxygenation and protect against PPC. Up to now, it is not known whether high levels of PEEP combined with RM are superior to lower PEEP without RM for protection against PPCs during OLV.

Hypothesis: An intra-operative ventilation strategy using higher levels of PEEP and recruitment maneuvers, as compared to ventilation with lower levels of PEEP without recruitment maneuvers, prevents postoperative pulmonary complications in patients undergoing thoracic surgery under standardized one-lung ventilation.

Inclusion Criteria:

• Patient scheduled for open thoracic or video-assisted thoracoscopic surgery under general anesthesia requiring OLV (no emergency surgery)
• BMI < 35 kg/m2
• age ≥ 18 years
• expected duration of surgery > 60 min
• planned lung separation with double lumen tube (DLT, not for study purpose only)
• most of ventilation time during surgery expected to be in OLV

Exclusion Criteria:

• COPD GOLD grades III and IV, lung fibrosis, documented bullae, severe emphysema, pneumothorax
• uncontrolled asthma
• Heart failure NYHA Grade 3 and 4, Coronary Heart Disease CCS Grade 3 and 4
• previous lung surgery
• documented pulmonary arterial hypertension >25mmHg MPAP at rest or > 40 mmHg syst. (estimated by ultrasound)
• documented or suspected neuromuscular disease (thymoma, myasthenia, myopathies, muscular dystrophies, others)
• planned mechanical ventilation after surgery
• bilateral procedures
• lung separation with other method than DLT (e.g. difficult airway, tracheostomy)
• surgery in prone position
• persistent hemodynamic instability, intractable shock
• intracranial injury or tumor
• enrollment in other interventional study or refusal of informed consent
• pregnancy (excluded by anamnesis and/or laboratory analysis)
• esophagectomy, pleural surgery only, sympathectomy surgery only, chest wall surgery only, mediastinal surgery only, lung transplantation
• presence before induction of anaesthesia of one of the adverse events, listed as postoperative pulmonary complications (aspiration, moderate respiratory failure, infiltrates, pulmonary infection, atelectasis, cardiopulmonary edema, pleural effusion, pneumothorax, pulmonary embolism, purulent pleuritis, lung hemorrhage)
• documented preoperative hypercapnia > 45mmHg (6kPa)