Huijun Xi1, Jingjing Liu2, Li Gui3. 1. Digestive Endoscopy Center, Changhai Hospital, 168 Changhai Road, Shanghai 200433, People's Republic of China. 2. Emergency Nursing Department, School of Nursing, 2nd Military Medical University, 800 Xiangyin Road, Shanghai 200433, People's Republic of China. 3. Emergency Nursing Department, School of Nursing, 2nd Military Medical University, 800 Xiangyin Road, Shanghai 200433, People's Republic of China. Electronic address: guili2000@foxmail.com.