1. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts;
2. Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
3. Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, Stanford University, Stanford, California;
4. Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington; and
5. Medical Service, Veterans Affairs Puget Sound Health Care System, Seattle, Washington