 The investigators will assess regional ventilation by means of micro-CT scanning during spontaneous breathing after the TOF ratio has reached 0.9. This way, the investigators can accurately reconstruct airway morphology. The different airway sections can then be linked to the corresponding lung tissue, and a full anatomical picture is thus rendered. A comparison of morphological scans at different breathing levels e.g. end-inspiratory and end-expiratory will allow us to model breath-by-breath regional airway and alveolar recruitment. 