1. Shandong University, Jinan, Shandong 250100, P.R. China
2. Department of Respiratory Medicine, Yantai Yuhuangding Hospital, Yantai, Shandong 264000, P.R. China
3. Department of Respiratory Medicine, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, P.R. China