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