[1] Prehosp Emergency Med Serv, Res Dept, Olof Palmes Alle 34, DK-8200 Aarhus N, Denmark
[2] Aarhus Univ Hosp, Dept Clin Epidemiol, DK-8000 Aarhus, Denmark
[3] Aarhus Univ Hosp, Dept Anesthesiol, DK-8000 Aarhus, Denmark
[4] Odense Univ Hosp, Mobile Emergency Care Unit, Anaesthesiol & Intens Care, Odense, Denmark
[5] Univ Copenhagen, Emergency Med Serv, Copenhagen, Denmark