[1] Sunnybrook Ctr Prehosp Med, Toronto, ON M8W 3S2, Canada
[2] Univ Toronto, Div Emergency Med, Toronto, ON, Canada
[3] St Michaels Hosp, Rescu Li Ka Shing Knowledge Inst, Toronto, ON M5B 1W8, Canada
[4] Univ Toronto, Inst Med Sci, Toronto, ON, Canada