Institution: | 1Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea.;2Commander, Armed Forces Chunchun Hospital, Chunchun, Korea.;3Department of Pulmonary and Critical Care Medicine, and Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.;4Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea. |