1. Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
2. Department of Emergency Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
3. Department of Epidemiology and Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
4. Department of Anesthesia, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.