1. Division of Pulmonary, Allergy, and Critical Care Medicine, Duke University Hospital , 2301 Erwin Road, Durham, North Carolina 27710 , USA
2. Department of Surgery, University of North Carolina School of Medicine , 101 Manning Drive, Chapel Hill, North Carolina 27599 , USA
3. North Carolina Jaycee Burn Center , 101 Manning Drive, Chapel Hill, North Carolina 27599 , USA
4. Department of Anesthesiology, University of North Carolina School of Medicine , 101 Manning Drive, Chapel Hill, North Carolina 27599 , USA
5. Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill , 135 Dauer Drive, Chapel Hill, North Carolina 27599 , USA
6. Department of Psychiatry, University of North Carolina School of Medicine , 101 Manning Drive, Chapel Hill, North Carolina 27599 , USA