[1] Yale Univ, Sch Med, Sect Emergency Med, New Haven, CT 06519 USA
[2] Boston Univ, Sch Med, Dept Emergency Med, Boston, MA 02118 USA
[3] Boston Univ, Sch Publ Hlth, Dept Maternal & Child Hlth, Boston, MA USA
[4] Brown Univ, Sch Med, Dept Emergency Med, Providence, RI 02912 USA
[5] Carolinas Med Ctr, Dept Emergency Med, Charlotte, NC 28203 USA
[6] Univ Michigan, Sch Med, Sect Emergency Med, Ann Arbor, MI USA