1. Department of Pulmonary, Critical Care and Sleep Medicine, Virginia Tech Carilion School of Medicine, Carilion Clinic, Roanoke, VA, USA
2. Department of Emergency Medicine, Virginia Tech Carilion School of Medicine, Carilion Clinic, Roanoke, VA, USA
3. Department of Statistics, Virginia Tech Carilion School of Medicine and Research Institute, Roanoke, VA, USA