1. Department of Respiratory Medicine, The Fourth People's Hospital of Guiyang, Guiyang, Guizhou 550002, P.R. China
2. Department of Respiratory Diseases, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Institute of Respiratory Disease, Guangzhou, Guangdong 510120, P.R. China
3. Department of Respiratory Medicine, The Affiliated Zhoushan Hospital of Wenzhou Medical University, Zhoushan, Zhejiang 316000, P.R. China