1. Department of Anesthesiology, The Second Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China
2. Department of Emergency, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China
3. Endoscopy Center, The Seventh Affiliated Hospital of Sun Yat-sen University, No. 628, Zhenyuan Road, Guangming District, Shenzhen 518101, China