1 Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine, Department of Medicine, Medical University of South Carolina, Charleston, SC.
2 Birmingham Veterans Affairs Health Care System, Birmingham, AL.
3 Atlanta Veterans Affairs Health Care System, Decatur, GA; Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA.
4 Jesse Brown Veterans Affairs Medical Center, Chicago, IL.
5 Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine, Department of Medicine, Medical University of South Carolina, Charleston, SC; Ralph H. Johnson Veterans Affairs Health Care System, Charleston, SC. Electronic address: [email protected].