Linna Huang1, Tianshu Zhai1, Lin Hua2, Qingyuan Zhan3. 1. Department of Pulmonary and Critical Care Medicine, Centre for Respiratory Diseases, China-Japan Friendship Hospital, Postal Address: No. 2 Yinghua East Road, Chaoyang District, Beijing 100029, PR China. 2. School of Biomedical Engineering, Capital Medical University, Beijing, PR China. Electronic address: hualin7750@ccmu.edu.cn. 3. Department of Pulmonary and Critical Care Medicine, Centre for Respiratory Diseases, China-Japan Friendship Hospital, Postal Address: No. 2 Yinghua East Road, Chaoyang District, Beijing 100029, PR China. Electronic address: drzhanqy@163.com.