1. Department of Respiratory and Critical Care Medicine, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, P. R. China
2. Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, Sichuan, P. R. China
3. North Sichuan Medical College, Nanchong, Sichuan, P. R. China
4. Department of Geriatric intensive care unit, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, P. R. China
5. Department of Respiratory and Critical Care Medicine, Anyue County People’s Hospital, Anyue, Sichuan, P. R. China
6. Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, P. R. China