[1] Univ N Carolina, Dept Emergency Med, 170 Manning Dr, Chapel Hill, NC 27599 USA
[2] Univ Penn, Wharton Sch Business, Philadelphia, PA 19104 USA
[3] Thomas Jefferson Univ, Dept Emergency Med, Philadelphia, PA 19107 USA
[4] Univ Penn, Dept Surg, Div Traumatol Surg Crit Care & Emergency Surg, Philadelphia, PA 19104 USA
[5] Univ Penn, Dept Emergency Med, Philadelphia, PA 19104 USA
[6] Philadelphia Fire Dept, Philadelphia, PA USA