1. Department of Anaesthesiology; Haugesund Hospital, Helse Fonna; Haugesund Norway
2. Oslo Centre for Biostatistics and Epidemiology; Oslo University Hospital; Oslo Norway
3. Norwegian Ministry of Trade, Industry and Fisheries; Oslo Norway
4. Department of Anaesthesiology; Division of Emergencies and Critical Care; Oslo University Hospital, Rikshospitalet; Oslo Norway