Emergency Department of China Rehabilitation Research Center, Fengtai District, Capital Medical University, no.10 Jiaomen North Street, Beijing, 100068, China. Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, NO.10 Xitoutiao, Youanmen, Fengtai District, Beijing, 100069, China. Department of Critical Care Medicine, Xuan Wu Hospital, Capital Medical University, no. 45 Changchun Street, Xicheng District, Beijing, 100053, China. Medical Intensive Care Unit, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, NO.1 Shuaifuyuan, Dongcheng District, Beijing, 100730, China. Department of Critical Care Medicine, Fu Xing Hospital, Capital Medical University, no. 20 Fuxingmenwai Street, Xicheng District, Beijing, 100038, China. Department of Critical Care Medicine, Fu Xing Hospital, Capital Medical University, no. 20 Fuxingmenwai Street, Xicheng District, Beijing, 100038, China. xixiuming2937@sina.com.