Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
Address for correspondence: Kyung Ho Kang, M.D., Ph.D. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Guro Hospital, Korea. University College of Medicine 80 Guro Dong, Guro Ku, 152-050, Seoul, Korea. Phone: 82-2-818-6638, Fax: 82-2-865-9670, kkhchest@korea.ac.kr