1. Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland;
2. Department of Medicine and Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California;
3. Division of Pulmonary, Critical Care and Sleep, University of California at San Francisco, San Francisco, California;
4. Division of Pulmonary and Critical Care, University of Utah School of Medicine, Salt Lake City, Utah;
5. Division of Pulmonary, Critical Care and Sleep Medicine, National Jewish Health, Denver, Colorado;
6. Division of Pulmonary, Critical Care and Occupational Medicine, and
7. Department of Psychiatry and Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa;
8. Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois;
9. Division of Pulmonary and Critical Care Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan;
10. Lung Health Center, Division of Pulmonary, Allergy and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama;
11. Birmingham Veterans Affairs Medical Center, Birmingham, Alabama;
12. Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina;
13. Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina;
14. Department of Thoracic Medicine and Surgery, Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania;
15. Division of General Internal Medicine, Columbia University Medical Center, New York, New York; and
16. Cornell University School of Medicine, New York, New York