1 Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Pusan National University Yangsan Hospital, Yangsan-si, GyeongNam, Republic of Korea.
2 Department of Thoracic and Cardiovascular Surgery, Pusan National University Yangsan Hospital, Yangsan-si, GyeongNam, Republic of Korea.
3 Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Pusan National University Yangsan Hospital, Geumo-ro 20, Beomeo-ri, Mulgeum-eup, Yangsan-si, GyeongNam 50612, Republic of Korea. Electronic address: yskim@pusan.ac.kr.