1 Kyung Hee University School of Medicine, Seoul, Korea (the Republic of).
2 ilsan paik hospital, pulmonary and critical care medicine, Goyang-city, Korea (the Republic of).
3 University of Ulsan, Asan Medical Center, Department of Internal Medicine, Seoul, Korea (the Republic of).
4 Asan Medical Center, Department of Laboratory Medicine, Seoul, Korea (the Republic of).
5 Asan Medical Center, University of Ulsan College of Medicine, Department of Radiology, Seoul, Korea (the Republic of).
6 Asan Medical Center, Seoul, Korea (the Republic of).
7 Asan Medical Center, College of Medicine University of Ulsan, Seoul, Korea (the Republic of).
8 Asan Medical Center, College of Medicine University of Ulsan, Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul, Korea (the Republic of).
9 Bloomsbury Institute of Intensive Care Medicine, London, United Kingdom of Great Britain and Northern Ireland; sangho@amc.seoul.kr.