*Pulmonary, Allergy, and Critical Care Division, Department of Medicine, and †Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; ‡Pulmonary and Allergy Associates, Morristown, New Jersey, and §Morristown Medical Center, Morristown, New Jersey; ∥Department of Emergency Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; ¶Department of Anesthesiology, Columbia University Medical Center, New York, New York; and #Department of Emergency Medicine, Medstar Washington Hospital Center, Washington, DC, and **Georgetown University School of Medicine, Washington, DC