1 Department of Emergency Medicine, Brooke Army Medical Center, Fort Sam Houston, TX, USA.
2 Department of Emergency Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA. Electronic address: WB4Z@hscmail.mcc.virginia.edu.
3 Department of Emergency Medicine, UT Southwestern, Dallas, TX, USA.
4 Department of Emergency Medicine, Brooke Army Medical Center, Fort Sam Houston, TX, USA. Electronic address: brit.long@yahoo.com.