[1] Univ Ulsan, Coll Med, Asan Med Ctr, Dept Pulm & Crit Care Med, 88,Olympic Ro 43 Gil, Seoul 05505, South Korea
[2] Soonchunhyang Univ, Div Allergy & Resp Dis, Seoul Hosp, Seoul, South Korea
[3] Yonsei Univ, Severance Hosp, Dept Internal Med, Div Pulm & Crit Care Med,Coll Med, Seoul, South Korea
[4] Seoul Natl Univ, Bundang Hosp, Dept Internal Med, Coll Med, Seongnam, South Korea
[5] Seoul Natl Univ, Seoul Natl Univ Hosp, Coll Med, Dept Internal Med,Div Pulm & Crit Care Med, Seoul, South Korea
[6] Inje Univ, Ilsan Paik Hosp, Dept Internal Med, Div Pulm & Crit Care Med, Goyang, South Korea