*Pulmonary, Allergy, and Critical Care Division, Perelman School of Medicine
†Department of Medicine, Palliative and Advanced Illness Research Center, Perelman School of Medicine
‡Leonard Davis Institute of Health Economics
§Department of Biostatistics, Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
G.E.W. is supported by NIH T32 HL098054. M.O.H. declares no conflict of interest.