1. Department of Emergency Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
2. Department of Emergency Medicine, University of Texas Southwestern, Medical Center, Dallas, TX 75390, USA
3. Department of Emergency Medicine, University of Chicago, Chicago, IL 60637, USA
4. Department of Emergency Medicine, George Washington University, Washington, DC 20052, USA
5. Department of Emergency Medicine, Gwinnett Medical Center, Lawrenceville, GA 30096, USA