[1] Seoul Natl Univ, Bundang Hosp, Dept Internal Med, Div Pulm & Crit Care Med, Songnam, South Korea
[2] Seoul Natl Univ, Bundang Hosp, Lung Inst, Songnam, South Korea
[3] Seoul Natl Univ, Coll Med, Dept Internal Med, Div Pulm & Crit Care Med, Seoul 110744, South Korea
[4] Seoul Natl Univ, Coll Med, Lung Inst, Seoul 110744, South Korea
[5] Seoul Natl Univ, Boramae Hosp, Dept Internal Med, Div Pulmonol, Seoul 110744, South Korea
[6] Dongguk Univ, Ilsan Hosp, Coll Med, Div Pulmonol & Crit Care Med,Dept Internal Med, Goyang, South Korea
[7] Chung Ang Univ, Coll Med, Dept Internal Med, Div Pulm & Crit Care Med, Seoul 156756, South Korea