1. Department of Emergency Medicine, Los Angeles County+USC Medical Center, General Hospital, 1200 State Street, Room 1011, Los Angeles, CA 90033, USA
2. Division of Emergency Medicine, Stanford University Medical Center, 300 Pasteur Drive, Alway Building, M121, Stanford, CA 94305, USA
3. Division of Emergency Medicine, New York-Presbyterian Hospital, Columbia University Medical Center, 622 West 168th Street, New York, NY 10032, USA