Department of Internal Medicine, Hanyang University College of Medicine, Korea.
1Division of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Korea.
Address for correspondence: Younsuck Koh M.D. Division of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, 338-1, Poongnap-dong, Songpa-gu, Seoul, 138-736, Korea. Phone: 02-3010-3134, Fax: 02-3010-4709, yskoh@amc.seoul.kr