[1] Boston Univ, Sch Med, Dept Emergency Med, Boston, MA 02118 USA
[2] Johns Hopkins Univ, Sch Med, Dept Emergency Med, Baltimore, MD USA
[3] Brown Univ, Dept Emergency Med, Alpert Sch Med, Providence, RI 02912 USA
[4] Univ N Carolina, Dept Emergency Med, Chapel Hill Sch Med, Chapel Hill, NC USA
[5] Univ N Carolina, Dept Internal Med, Chapel Hill Sch Med, Chapel Hill, NC USA