In ventilated patients with acute respiratory failure endotracheal suctioning may lead to alveolar derecruitment, which can be monitored by means of functional residual capacity (FRC) measurements. Regional distribution of ventilation can be followed at bedside using electrical impedance tomography. The investigators hypothesize that a FRC guided recruitment strategy, aimed at restoring a baseline FRC value after open endotracheal suctioning, improves oxygenation and regional distribution of ventilation. In addition the investigators research the impact of such a strategy on the inflammatory response to mechanical ventilation.

Inclusion Criteria:

• need for mechanical ventilation due to respiratory failure after cardiac surgery

Exclusion Criteria:

• circulatory failure, eg. need for high doses of inotropes or extracorporal cardiac support