1. Department of Critical Care Medicine, The Second School of Clinical Medicine, Southern Medical University, Guangzhou, Guangdong 510280, P.R. China
2. Department of Respiratory Medicine, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China
3. Department of Emergency Medicine, People's Hospital of Henan University of Chinese Medicine/Zhengzhou People's Hospital, Zhengzhou, Henan 450003, P.R. China
4. Department of Critical Care Medicine, The Fifth Clinical Medical College of Henan University of Chinese Medicine, Zhengzhou, Henan 450003, P.R. China