Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Asan, Korea.
Address for correspondence : Dong Soon Kim, M.D. Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center 388-1 Pungnap-dong, Songpa-gu, Seoul, 138-736, Korea. Phone : 82-2-3010-3132, Fax : 82-2-3010-6968, dskim@amc.seoul.kr