1. Division of Pulmonary, Allergy and Critical Care and Sleep Medicine, University of Arizona, Tucson, Arizona
2. Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
3. Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Arizona College of Medicine–Phoenix, Phoenix, Arizona
4. Birmingham VA Medical Center, Birmingham, Alabama; and
5. Southern Arizona VA Health Care System, Tucson, Arizona