1. Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
2. Division of Pulmonology, Critical Care and Sleep Medicine, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
3. Division of Pulmonology, Department of Internal Medicine, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea.
4. Department of Internal Medicine, Medical School and Research Institute of Clinical Medicine, Chonbuk National University, Jeonju, Korea.
5. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea.