1. Department of Medical Physiology, Panum Institute, University of Copenhagen, DK-2200 Copenhagen;
2. Department of Clinical Physiology, Herlev Hospital, DK-2730 Herlev; and
3. Department of Aviation Medicine, Rigshospitalet 7805, DK-2200 Copenhagen;
4. Department of Physiology and Pharmacology, University of Southern Denmark, DK-5000 Odense, Denmark