1. Division of Pulmonary and Critical Care Medicine and
2. Division of Pulmonary, Critical Care, and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts;
3. Division of Pulmonary, Critical Care, and Occupational Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa;
4. Boston University School of Public Health, Boston, Massachusetts; and
5. Cardiology Division, Massachusetts General Hospital, Boston, Massachusetts;
6. Vertex Pharmaceuticals, Boston, Massachusetts