Prediction of the difficult airway by pre-operative ultrasound-based measurement of airway parameters: A prospective observational study

Abstract

Background and Aims: Ultrasonography has emerged as a new airway assessment tool. However, its role in predicting difficult airways needs to be explored. This study aimed to evaluate the accuracy of pre-operative ultrasound assessment of the neck in predicting difficult airways in patients undergoing elective surgery under general anaesthesia. Methods: One hundred and fourteen adult patients undergoing elective surgeries under general anaesthesia were enrolled in this study. In the pre-operative room, upper airway ultrasound measurements of the neck were obtained, namely, distance from skin to the hyoid bone, distance from skin to the thyroid isthmus and thickness of the base of the tongue. Clinical airway assessment details were noted from the pre-anaesthetic evaluation form. The airway management technique was noted. Receiver operating characteristic curves were used to assess the diagnostic value of these upper airway ultrasound measurements in predicting difficult airways. Results: The distance from the skin to the thyroid isthmus in the difficult airway group (0.37 ± 0.133 cm) was significantly higher than in the non-difficult group (P = 0.007). It appeared to be a better predictor of difficult airways and correlated better with clinical tests among the measured ultrasound parameters. The body mass index was significantly higher in the difficult airway group (P = 0.009). Conclusion: Considering the difference in means between the two groups, distance from the skin to the thyroid isthmus should be explored as a potential predictor of a difficult airway in studies with a larger sample size.