1. Department of Pulmonary, Allergy and Critical Care Medicine, Hallym University Sacred Heart Hospital, Anyang, Korea.
2. Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Pulmonary and Critical Care Medicine, Yeungnam University Hospital, Daegu, Korea.
4. Department of Pulmonary and Critical Care Medicine, Inje University Sanggye Paik Hospital, Seoul, Korea.
5. Department of Internal Medicine, Kyeimyung University Dongsan Hospital, Daegu, Korea.
6. Department of Pulmonary and Critical Care Medicine, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
7. Department of Pulmonary and Critical Care Medicine, Chungnam University Hospital, Daejeon, Korea.
8. Department of Internal Medicine, Pusan National University Hospital, Busan, Korea.
9. Department of Pulmonary, Critical Care and Sleep Medicine, St. Paul's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
10. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Inje University Ilsan Paik Hospital, Goyang, Korea.
11. Department of Pulmonary, Allergy and Critical Care Medicine, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
12. Department of Internal Medicine, Hanyang University Guri Hospital, Guri, Korea.
13. Department of Pulmonary, Allergy and Critical Care Medicine, Chonbuk National University Hospital, Jeonju, Korea.