1 Children's National Hospital, George Washington University School of Medicine and Health Sciences, Division of Emergency Medicine and Trauma Center, Washington, District of Columbia.
2 Los Angeles County Emergency Medical Services Agency, Harbor-UCLA Medical Center, David Geffen School of Medicine at UCLA, Department of Emergency Medicine, Los Angeles, California.
3 Children's Hospital at LHSC, Department of Pediatrics and Medicine, Schulich School of Medicine & Dentistry-Western University, London, Ontario, Canada.