[1] Vancouver Gen Hosp, Dept Emergency Med, 855 12th Ave W, Vancouver, BC V5Z 1M9, Canada
[2] Univ British Columbia, Dept Emergency Med, Vancouver, BC, Canada
[3] St Pauls Hosp, Dept Emergency Med, Vancouver, BC, Canada
[4] Denver Hlth Med Ctr, Dept Emergency Med, Denver, CO USA
[5] Univ Colorado, Sch Med, Dept Emergency Med, Aurora, CO USA