1. Department of Respiratory and Critical Care Medicine, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China
2. Research Unit of Respiratory Disease, Central South University, Changsha, Hunan, China
3. Diagnosis and Treatment Center of Respiratory Disease, Central South University, Changsha, Hunan, China
4. Department of Respiratory, The Eighth Hospital, Changsha, Hunan, China in
5. Division 4 of Occupational Diseases, Hunan Prevention and Treatment Institute for Occupational Diseases, Changsha, China