[1] Stanford Univ, Sch Med, Dept Emergency Med, 900 Welch Rd,Suite 350, Palo Alto, CA 94304 USA
[2] Western Univ, Schulich Sch Med & Dent, Div Emergency Med, London, ON, Canada
[3] Western Univ, Schulich Sch Med & Dent, Ctr Educ Res & Innovat, London, ON, Canada
[4] Western Univ, Dept Med, London, ON, Canada
[5] Western Univ, Fac Educ, London, ON, Canada