Affiliation: | 1. Department of Emergency Medicine, University of North Carolina, 170 Manning Drive, CB # 7594, Chapel Hill, NC 27599-7594, USA;2. North Carolina State Highway Patrol, 3318 Garner Road, Raleigh, NC 27610, USA;3. Wake County Emergency Medical Services, 331 South McDowell Street, Raleigh, NC 27601, USA |