1. Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
2. Barlow Respiratory Hospital, Los Angeles, CA 90026, USA
3. Department of Medicine, Division of Palliative Care Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
4. Department of Anesthesiology, András Jósa County Hospital, 4400 Nyíregyháza, Hungary
5. Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, National Taiwan University Hospital, Taipei 100, Taiwan
6. Pulmonary, Critical Care and Sleep Section, West Los Angeles VA Medical Center, Los Angeles, CA 90073, USA