[1] Inje Univ, Haeundae Paik Hosp, Dept Pulm & Crit Care Med, Coll Med, Busan, South Korea
[2] Hanyang Univ, Dept Internal Med, Div Pulm Med & Allergy, Coll Med, Seoul, South Korea
[3] Hallym Univ, Dept Internal Med, Div Pulm Allergy & Crit Care Med, Kangnam Sacred Heart Hosp, Seoul, South Korea
[4] Univ Ulsan, Asan Med Ctr, Dept Pulm & Crit Care Med, Coll Med, Seoul, South Korea