Abstract:Objective To analyze the relevant influencing factors for the tracheal intubation with video laryngoscope in the supine position without hyperextension of the neck and to explore the way of enhancing the quality of airway management. Methods We enrolled 200 patients undergoing elective abdominal operation under general anesthesia in our hospital from June 2017 to March 2018, and recorded factors that may affect tracheal intubation success rate, intubation time, and postoperative hoarseness including age, height, and weight of the patients, the bending angle of endotracheal tube and work experience of the operator. Besides, anatomic parameters such as thyromental distance, and surgery information such as intubation and anesthesia time were documented. Logistic regression model was used to analyze the influencing factors for the failure of initial intubation attempt and postoperative hoarseness. Receiver operating characteristic (ROC) curve was applied to calculate the cut-off value of the bending angle of endotracheal tube. Results The bending angle of endotracheal tube, thyromental distance and the angle of head extension were different between the successful intubation group and failed intubation group (P < 0.05). The weight and body mass index of the patients in the group with intubation time less than 30 s were lower than those in the group with intubation time no less than 30 s (P < 0.05). The weight of the patients, the bending angle of endotracheal tube and the success rate of initial intubation attempt were different between the group with and without postoperative hoarseness (P < 0.05). Multivariate Logistic regression analysis suggested that thyromental distance [O^R = 1.588 (95% CI: 1.080, 2.336)] and the bending angle of endotracheal tube [O^R = 1.097 (95% CI: 1.048, 1.148)] were influencing factors for the failure of initial intubation attempt, and that the bending angle of endotracheal tube [ O^R = 0.916 (95% CI: 0.873, 0.961)] was an influencing factor for postoperative hoarseness. ROC analysis showed that the bending angle of endotracheal tube less than 78.55° would increase the risk of failure in the first attempt to intubation, while that greater than 84.10° would increase the risk of postoperative hoarseness. Conclusions In tracheal intubation with video laryngoscope in the supine position without hyperextension of the neck, the bending angle of the endotracheal tube affected both the success rate of intubation and the incidence of postoperative hoarseness. The bending angle of endotracheal tube between 78.55° to 84.10° may be potentially optimal and could be recommended for clinical use.