Community Activities - Derived from data collected in the ARISCAT study [14] and previous studies

Derived from data collected in the ARISCAT study [14] and previous studies on the incidence of postoperative pulmonary complications [12,13,30]. A two group c2 test with a 0.05 two-sided significance level will have 80 power to detect the difference (in post-operative pulmonary complications) between conventional mechanical ventilation (24 ) and open lung mechanical ventilation (16.5 ) (Odds ratio of 0.626) when the sample size in each group is 450. Interim analysis - one main concern is not to withhold positive effects of the open lung mechanical ventilation strategy to the control group. Therefore, 3 interim analyses are performed after 300 and 600 patients. The first interim analysis is performed when 300 patients have successfully been included and followed-up. If the intervention has a strong trend for improving post-operative pulmonary complications (as defined above) with a p-value < 0.