Ultrasound Quantification of Anterior Neck Soft-Tissue Thickness: A Reliable Predictor of Difficult Laryngoscopy in Obese Patients

Abstract

Background: Obese patients are at increased risk of difficult laryngoscopy due to anterior neck soft-tissue deposition. Conventional clinical predictors have limited reliability in this population. This study evaluated the predictive performance of bedside ultrasound measurement of anterior neck soft-tissue thickness. Methods: This prospective observational study included 60 obese adults (BMI ≥30 kg/m², ASA II–III) undergoing elective surgery under general anaesthesia. Standard clinical airway assessment and ultrasonographic measurements of skin-to-hyoid bone (DSHB), skin-to-epiglottis (DSEM), and skin-to-anterior commissure (DSAC) distances were performed preoperatively. Difficult laryngoscopy was defined as Cormack-Lehane grade 3 or 4. Multivariate logistic regression and receiver operating characteristic (ROC) analysis were used. Results: Difficult laryngoscopy occurred in 11/60 patients (18.3%). Groups were comparable in demographics and BMI. Modified Mallampati score III (p=0.007) and neck circumference (p=0.002) were associated with difficulty. Ultrasound parameters showed the strongest discrimination: DSHB1.91± 0.30vs 1.38 ±0.20 cm, DSEM2.79± 0.50 vs1.89 ± 0.35cm, and DSAC1.70± 0.35vs 1.32± 0.30cm (all p<0.0002). These measurements remained independent predictors on multivariate analysis. Conclusion: Ultrasound quantification of anterior neck soft-tissue thickness provides objective and reliable prediction of difficult laryngoscopy in obese patients and may serve as a valuable adjunct to conventional airway assessment.