1. Department of Pulmonary and Critical Care Medicine, Cheng Du Qing Cheng Mt. Hospital, Chongzhou City, Chengdu, China
2. Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
3. School of Mathematics, Sichuan University, Chengdu, Sichuan, China.