Abstract: PURPOSE: To evaluate the efficacy of fiberoptic bronchoscopy combined with end-tidal carbon dioxide monitoring for endotracheal intubation in patients with difficult airway in oral and maxillofacial surgery. METHODS: Sixty patients with expected difficult airway under general anesthesia undergoing oral and maxillofacial surgery from November 2018 to January 2019 were selected. ASA grade I-II patients were randomly divided into two groups (n=30). Patients in the experimental group received end-tidal carbon dioxide monitoring combined with fiberoptic bronchoscopy for transnasal endotracheal intubation under the condition of preserving patients' spontaneous breathing, while patients in the control group only received fiberoptic bronchoscopy for the procedures. The success rate of the first endotracheal intubation, the duration of endotracheal intubation with fiberoptic bronchoscopy, the number of attempts, and the incidence of endotracheal complications were recorded. GraphPad Prism 6 was used for statistical analysis. RESULTS: A total of 60 patients were included and 60 were actually completed. There was no significant difference in the success rate of first endotracheal intubation between the two groups (90.0% for the control group and 93.3% for the experimental group, P=0.2196). There was no significant difference in the average number of intubation attempts between the two groups (1.2±0.2 times in the control group and 1.1±0.1 times in the experimental group, P=0.6451). The intubation time in the experimental group was significantly lower than that in the control group (29.5±2.3) s in the control group and (15.8±1.2) s in experimental group, P=0.0192:. During intubation, there was no significant difference in the incidence of tachycardia (HR>100 times/min) between the two groups (6.6% for the control group and 3.3% for the experimental group, P=0.1746). There was no significant difference in the incidence of increased blood pressure (20% higher than the essential blood pressure) during intubation between the two groups (10.0% in the control group and 6.7% in the experimental group, P=0.2541). The incidence of oxygen saturation decrease (SpO₂<90%) in the experimental group was significantly lower than that in the control group (13.3% in the control group and 6.7% in the experimental group, P=0.0412). The incidence of epistaxis was significantly lower in the experimental group than in the control group (16.7% in the control group and 6.7% in the experimental group, P=0.0224). There was no significant difference in the incidence of postoperative pharyngeal pain between the two groups (6.7% in the control group and 3.3% in the experimental group, P=0.1652). Postoperative hoarseness did not occur in either group. There was no significant difference in the incidence of postoperative adverse memory between the two groups (6.7% in the control group and 3.3% in the experimental group, P=0.1652). CONCLUSIONS： End-tidal carbon dioxide monitoring combined with endotracheal intubation through nasal fiberoptic bronchoscopy can shorten the duration of endotracheal intubation, decrease oxygen saturation during intubation and reduce the incidence of epistaxis, thus improving the efficiency and safety of endotracheal intubation.

Key words: Fiberoptic bronchoscope, End-tidal carbon dioxide monitoring, Difficult airway, Tracheal intubation, General anesthesia