[1] Keimyung Univ, Sch Med, Dept Med, Daegu, South Korea
[2] Keimyung Univ Dongsan Hosp, Dept Internal Med, Div Pulm & Crit Care Med, Daegu, South Korea
[3] Daegu Catholic Univ, Sch Med, Dept Internal Med, Daegu, South Korea
[4] Yeungnam Univ Hosp, Reg Resp Ctr, Dept Internal Med, Div Pulm & Crit Care Med, Daegu, South Korea
[5] Kyungpook Natl Univ, Sch Med, Dept Internal Med, Div Pulm & Crit Care Med, Daegu, South Korea