1. Division of Pulmonary and Critical Care Medicine
2. Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery
3. Health Sciences Research-Biomedical Statistics and Informatics, and
4. Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota
5. Division of Pulmonary and Critical Care Medicine, Johns Hopkins Bayview Medical Center, Baltimore, Maryland; and
6. Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania