Ben Beck1, Karen Smith2, Eric Mercier3, Peter Cameron4. 1. Department of Epidemiology and Preventive Medicine, Monash University, Victoria, Australia. Electronic address: ben.beck@monash.edu. 2. Department of Research and Evaluation, Ambulance Victoria, Australia; Department of Epidemiology and Preventive Medicine, Monash University, Victoria, Australia; Department of Community Emergency Health and Paramedic Practice, Monash University, Victoria, Australia. 3. Department of Epidemiology and Preventive Medicine, Monash University, Victoria, Australia; Department of Family and Emergency Medicine, Laval University, Quebec City, Quebec, Canada; Emergency and Trauma Centre, The Alfred, Melbourne, Victoria, Australia. 4. Department of Epidemiology and Preventive Medicine, Monash University, Victoria, Australia; Emergency and Trauma Centre, The Alfred, Melbourne, Victoria, Australia.