1. Department of Internal Medicine, Taipei Veterans General Hospital Yuli branch, No. 91, Xinxing St., Yuli, Hualien 98142, Taiwan
2. Department of Chest Medicine, Taipei Veterans General Hospital, No. 201, Sec. 2, Shih-Pai Rd., Beitou Dist., Taipei 12117, Taiwan
3. School of Medicine, National Yang Ming Chiao Tung University, No. 155, Sec. 2, Linong St. Beitou Dist., Taipei 112304, Taiwan
4. Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA