Divison of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Ilsan Paik Hospital, Inje University College of Medicine, Ilsan Department of Internal Medicine, National Medical Center, Seoul Department of Pulmonology and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul Department of Critical Care, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang Division of Pulmonary and Critical Care Medicine, Kyung Hee Medical Center, Kyung Hee University Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul Department of Pulmonary and Critical Care Medicine, Kyung Hee University Hospital at Gangdong, Kyung Hee University, Seoul Division of Pulmonary, Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul Division of Pulmonology, Department of Internal Medicine, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Bucheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Bucheon Department of Pulmonary and Allergy, Department of Internal Medicine, Regional Respiratory Center, Yeungnam University Hospital, Daegu Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul Division of Pulmonology and Critical Care Medicine, Department of Internal Medicine, Uijeongbu St Mary's Hospital, College of Medicine, The Catholic University of Korea, Uijeongbu Division of Pulmonary, Sleep and Critical Care Medicine, Department of Internal Medicine, Korea University Guro Hospital, Korea University Medical School, Seoul Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Yeouido St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, KonKuk University School of Medicine, Seoul Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Wonkwang University Sanbon Hospital, Wonkwang University College of Medicine, Sanbon Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Republic of Korea.