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. Clinical Medical Research Center for Respiratory and Critical Care Medicine in Hunan Province, China
5. Department of Pulmonary and Critical Care Medicine, Zhuzhou Central Hospital, Zhuzhou, Hunan, China
6. Division 4 of Occupational Diseases, Hunan Prevention and Treatment Institute for Occupational Disease, Changsha, Hunan, China