Abstract: PURPOSE: To evaluate the risk factors of difficult laryngoscopy through structure of airway measured by ultrasound. METHODS: A total of 300 patients supposed to receive elective surgery under general anesthesia with endotracheal intubation were included. Before anesthesia induction, indicators such as tongue width, tongue thickness, mentohyoid distance, thyrohyoid distance and angle between base of tongue and thyroid cartilage were measured and recorded by ultrasound. After anesthesia induction, Cormack-Lehane (C-L) grade under laryngoscopy was conducted. One and 2 grades were defined as non-difficult laryngoscopy group and 3 and 4 grades were defined as difficult laryngoscopy group. The correlation between each evaluation index and C-L classification was analyzed by SPSS 22.0 software package. RESULTS: Angle between base of tongue and thyroid cartilage was thought as independent risk factor for predicting laryngoscopy, the cut-off point was 43°, sensibility was 96.2%, specificity was 83.6%, area under curve(AUC) was 0.866 [95%CI: 0.769-0.962]. CONCLUSIONS: Measuring angle between base of tongue and thyroid cartilage by ultrasound can be applied to predict difficult airway.

Key words: Ultrasonic measurement, Angle between base of tongue and thyroid cartilage, Difficult laryngoscopy