[1] Stanford Univ, Dept Emergency Med, Sch Med, 900 Welch Rd,Ste 350, Palo Alto, CA 94304 USA
[2] Yale Univ, Dept Emergency Med, Sch Med, New Haven, CT USA
[3] Emory Univ, Dept Emergency Med, Sch Med, Atlanta, GA USA
[4] Oregon Hlth & Sci Univ, Dept Emergency Med, Portland, OR 97201 USA
[5] Univ Maryland, Dept Emergency Med, Sch Med, Baltimore, MD USA