1. Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, Massachusetts
2. Department of Medicine, University of Toronto, Toronto, Ontario, Canada
3. Weill Cornell Medicine, New York, New York
4. Instituto Nacional de Enfermedades Respiratorias, Ismael Cosío Villegas, Mexico City, Mexico
5. Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico; and
6. Department of Medicine, University of Calgary, Calgary, Alberta, Canada