[1] Konkuk Univ, Konkuk Univ Hosp, Sch Med, Dept Internal Med,Div Pulm & Allergy, Seoul, South Korea
[2] Sungkyunkwan Univ, Samsung Med Ctr, Dept Med, Div Pulm & Crit Care Med,Sch Med, Seoul, South Korea
[3] Catholic Univ Korea, Coll Med, Dept Internal Med, Div Pulm & Crit Care Med,Seoul St Marys Hosp, Seoul, South Korea
[4] Korea Univ, Guro Hosp, Dept Internal Med, Div Resp & Crit Care Med,Med Ctr, Seoul, South Korea
[5] Sungkyunkwan Univ, Kangbuk Samsung Hosp, Dept Internal Med, Div Pulm & Crit Care Med,Sch Med, Seoul, South Korea
[6] Kyung Hee Univ, Kyung Hee Univ Hosp Gangdong, Dept Internal Med, Div Pulm & Crit Care Med,Sch Med, Seoul, South Korea
[7] Hallym Univ, Dept Internal Med, Div Pulm Allergy & Crit Care Med, Sacred Heart Hosp, 22,Gwanpyeong Ro 170 Beon Gil, Anyang Si 14068, Gyeonggi Do, South Korea