Lung function impairment is common after abdominal surgery. Few preventive strategies exist against postoperative lung function impairment. A new potential preventive strategy against postoperative lung function impairment comes from research on critically ill patients with severe respiratory failure. In this field research has long focused on influence of breathing volume (= tidal volume) during mechanical ventilation on outcome. It has been shown, that low tidal volumes improve patients outcomes as compared to (conventional) high tidal volumes. Therefore, we propose a patient and investigator blinded randomised trial to test the hypotheses that intraoperative mechanical ventilation with low tidal volumes as compared to high tidal volumes reduces postoperative lung function impairment in high risk patients.

Inclusion Criteria:

• written informed consent
• age ≥ 50 years and ASA classification ≥ II
• elective upper abdominal surgery of at least 3 hours duration
• general anaesthesia plus epidural anaesthesia.

Exclusion Criteria:

• < 18 years of age
• impaired mental state
• unwillingness to participate
• pregnancy
• duration of surgery < 3 hours
• ASA physical status ≥ IV
• increased intracranial pressure
• neuromuscular disease that impairs spontaneous breathing