1 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, Seoul, Republic of Korea.
2 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, 82 Gumi-ro 173 beon-gil Bundang-gu, Seongnam-si, Gyeonggi-do, Republic of Korea. yjlee1117@snubh.org.