1. Department of Critical Care Medicine, Samsung Medical Center, School of Medicine, Sungkyunkwan University, Seoul, Korea.
2. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, School of Medicine, Sungkyunkwan University, Seoul, Korea.
3. National Evidence-based Healthcare Collaborating Agency, Ministry of Health and Welfare, Korea.
4. Department of Information Statistics, Andong National University, Andong, Korea.
5. Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
6. Department of Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea.
7. Division of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
8. Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
9. Department of Internal Medicine, Chung Ang University College of Medicine, Seoul, Korea.
10. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.