[1] Catholic Univ Korea, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Seoul, South Korea
[2] Chung Ang Univ, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Seoul, South Korea
[3] Yonsei Univ, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Seoul, South Korea
[4] Chungnam Natl Univ, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Daejeon, South Korea
[5] Soonchunhyang Univ, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Bucheon, South Korea
[6] Ajou Univ, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Suwon, South Korea
[7] Ewha Womans Univ, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Seoul, South Korea
[8] Kyung Hee Univ Hosp, Coll Med, Dept Internal Med, Div Resp & Crit Care Med, Seoul, South Korea