Abstract: PURPOSE: To verify the accuracy of ultrasonic measurement of the anterior neck soft tissue to predict difficult airway, to find a suitable value of the anterior neck soft tissue for Chinese population, and to compare the accuracy with other airway assessments. METHODS: One hundred and forty-one patients were included, aged 13 to 88 years old, ASA class Ⅰ-Ⅲ, undergoing endotracheal intubation for an elective surgical procedure. The name, gender, age , height, weight of each patient were recorded. The clinical screening tests to predict difficult airway were performed (BMI, interincisoral gap, modified Mallampati score, thyromental distance). Ultrasound (US) measurements of anterior neck soft tissue were obtained(the level of hyoid bone, thyrohyoid membrane, vocal cords, thyroid isthmus and suprasternal notch). The laryngoscopic view was graded using Cormack and Lehane classification by anesthesia providers on the day of surgery. The data were analyzed using SPSS 19.0 software package. RESULTS: Difficult laryngoscope (Cormack-Lehane classification III-IV) was present in 17 of 141 patients. The sonographic measurements of anterior neck soft tissue were greater in the difficult laryngoscopy group compared to the easy laryngoscopy group at the level of the thyrohyoid membrane [(2.43±0.50)cm : (2.08±0.39)cmand vocal cords [(0.98±0.21)cm : (0.87±0.20)cmand D-value (the difference between the level of the thyrohyoid membrane and the vocal cords). The cut-off value was 2.19, 1.05 and 1.19 cm, respectively. CONCLUSIONS: Sonographic measurements of anterior neck soft tissue thickness at the level of thyrohyoid membrane, vocal cords and the D-value can be used to distinguish difficult and easy laryngoscopy.

Key words: Difficult airway, Difficult laryngoscopy, Endotracheal intubation, Ultrasound