1 Division of Pulmonary Medicine and Allergy, Department of Internal Medicine, Hanyang Medical Center, Hanyang University College of Medicine, Seoul, Republic of Korea.
2 Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Gyeonggi-do, Republic of Korea.
3 Department of Thoracic and Cardiovascular Surgery, Hanyang University College of Medicine, Seoul, Republic of Korea.
4 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Chungbuk National University Hospital, Chungbuk National University College of Medicine, Cheongju, Republic of Korea.
5 Department of Thoracic and Cardiovascular Surgery, Ewha Woman's University College of Medicine Mokdong Hospital, Seoul, Republic of Korea.