 Day of surgery. Standard periop care in coherence with department routines. Preoxygenation using FiO2 1.0 during induction of anaesthesia, and before commencing cardiopulmonary bypass CPB. Inhalational anaesthetics during surgical preparation, and again after weaning from CPB. Apnoea without PEEP or intermittent ventilation during CPB. Before weaning from CPB manual lung recruitment with the APL-valve set to 30 cm H2O, and visual guidance of the lungparenchyma or pleura. After chest closure, FiO2 is set to 0.5, volume controlled ventilation 4-6 mlKg titrated according to pCO2, and PEEP is set to 5 cm H2O. Patient ventilation circuit will be broken twice in conjugation with the use of a transport ventilator device before arrival in the CICU. Ventilator settings in the CICU is pressure-regulated volume-controlled ventilation VKTS, tidal volumes of 4-6 mlKg titrated according to pCO2, respiratory frequency of 14min, and PEEP 8 cm H2O. 