1. Department of Respiratory Internal Medicine, People's Hospital of Quzhou City, Quzhou, Zhejiang 324000, P.R. China
2. Institute of Respiratory Diseases, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, P.R. China
3. Department of Respiratory Internal Medicine, The Second Affiliated Hospital, Suzhou University, Suzhou, Jiangsu 215004, P.R. China