[1] Univ Vermont, Med Ctr, Div Emergency Med, Burlington, VT 05405 USA
[2] Brooke Army Med Ctr, Emergency Med, SAUSHEC, Ft Sam Houston, TX USA
[3] Univ Texas Southwestern Med Ctr Dallas, Dept Emergency Med, Dallas, TX USA
[4] Univ Vermont, Dept Surg, Larner Coll Med, Div Emergency Med, Burlington, VT 05405 USA