1. Critical Care Medicine Department, National Institutes of Health Clinical Center, National Heart, Lung, and Blood Institute, Bethesda, Maryland;
2. Department of Pulmonary Critical Care Medicine, Johns Hopkins Hospital, Baltimore, Maryland;
3. Division of Pulmonary and Critical Care, University of Michigan Hospital, Ann Arbor, Michigan; and
4. Pulmonary Services, MedStar Washington Hospital Center, Washington, D.C.