1. From the Department of Anaesthesiology and Critical Care Medicine, Merheim Medical Center, Witten/Herdecke University, Cologne, Germany
2. German Aerospace Center (DLR), Institute of Aerospace Medicine, Department of Cardiovascular Aerospace Medicine, Cologne, Germany
3. Department of Neurosurgery, Merheim Medical Center, Witten/Herdecke University, Cologne, Germany
4. Department of Radiology, Merheim Medical Center, Witten/Herdecke University, Cologne, Germany.