A Prospective Observational Study to Assess the Usefulness of Preoperative Ultrasound Measurement of Anterior Neck Soft Tissue Thickness in Predicting Difficult Airway

Background: Preoperative identification of difficult intubation remains a critical challenge in anaesthetic practice. Conventional clinical predictors demonstrate suboptimal sensitivity individually. Ultrasonographic assessment of anterior neck soft tissue offers a quantitative, non-invasive alternative that warrants systematic evaluation. Objectives: To assess the diagnostic accuracy of preoperative ultrasound-measured anterior neck soft tissue thickness at three anatomical levels in predicting difficult intubation and to evaluate its correlation with established clinical airway parameters. Methods: This prospective observational study enrolled 150 adult patients undergoing elective surgery under general anaesthesia with endotracheal intubation at Govt. Theni Medical College, Theni . Preoperative ultrasound measurements were recorded at three levels — skin to hyoid bone (Level 1), skin to epiglottis at thyrohyoid membrane (Level 2), and skin to tracheal ring at suprasternal notch (Level 3). Intraoperative Cormack-Lehane grading served as the reference standard. ROC curve analysis, independent t-test, Chi-square test, and Spearman's rank correlation were applied. Results: Difficult intubation was encountered in 11 patients (7.3%). Soft tissue thickness was significantly greater in the difficult airway group at all three levels (p = 0.000). Level 2 demonstrated superior diagnostic accuracy (AUC = 0.995, sensitivity 100%, specificity 99.3%) at a cutoff of 2.335 cm. No significant correlation was observed between ultrasound measurements and clinical airway parameters. Conclusion: Preoperative ultrasound measurement at the thyrohyoid membrane level is a highly accurate, independent predictor of difficult intubation. A cutoff of 2.335 cm offers near-perfect sensitivity and specificity, establishing its value as a reliable adjunct in preoperative airway assessment.