1. Emergency ICU, Regional Emergency Center, Chungnam National University Hospital, Daejeon, Korea.
2. Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, Chungnam National University Hospital, Daejeon, Korea.
3. Department of Anesthesiology, Chungnam National University Hospital, Daejeon, Korea.
4. Department of Anesthesiology, Chonbuk National University Hospital, Jeonju, Korea.
5. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Asan Medical Center, Seoul, Korea.