1. Division of Pulmonary, Allergy, and Critical Care Medicine, Duke University Hospital , Durham, North Carolina
2. Department of Surgery, University of North Carolina School of Medicine , Chapel Hill, North Carolina
3. North Carolina Jaycee Burn Center , Chapel Hill, North Carolina
4. Department of Anesthesiology, University of North Carolina School of Medicine , 101 Manning Drive Chapel Hill, North Carolina 27599
5. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill , North Carolina 27599