1. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea
2. Division of Pulmonary, Sleep and Critical Care Medicine, Department of Internal Medicine, Eunpyeong St. Mary's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea
3. Division of Pulmonology and Critical Care Medicine, Department of Internal Medicine, Yeouido St. Mary's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea
4. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, St. Vincent's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea
5. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Incheon St. Mary's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea
6. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Bucheon St. Mary's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea
7. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Uijeongbu St. Mary's Hospital, College of Medicine The Catholic University of Korea Seoul Republic of Korea