USG-guided Airway Assessment as an Adjunct to Predict Difficult Video-laryngoscopy and Intubation: A Prospective Preliminary Study

A BSTRACT Background and Aims: Ultrasound is now widely used for predicting difficult laryngoscopy and intubation. We evaluated the clinical and ultrasound parameters with respect to difficulty of glottic visualization and need for manipulation for intubation with a videolaryngoscope and also if any correlation exists between the individual ultrasound and clinical parameters. Methods: One hundred and sixty patients aged 18–60 years, ASA physical status I and II, without any airway pathology, posted for elective surgery under endotracheal general anesthesia were included. Airway was assessed with clinical predictors (Body Mass Index (BMI), Mallampati Score, Upper Lip Bite Test (ULBT), Neck Circumference to Thyromental distance (NC/TMD) ratio) and ultrasound parameters (soft tissue thickness at the level of Hyoid bone (SHB) and vocal cords (SVC), tongue thickness (TT)). They were then correlated with the visualization of percentage of glottic opening (POGO) on videolaryngoscopy and ease of intubation. Results: All ultrasound parameters and NC/TMD predicted POGO with the highest sensitivity. For manipulation required during intubation, the optimal cutoff values were BMI >26.75, Mallampati Grade of > III, ULBT grade > III, NC/TMD ratio >4.67, SVC 0.99 cm, SHB 0.89 cm, and TT 5.92 cm. Conclusions: Airway ultrasound is a useful adjunct to clinical parameters in assessing the airway for videolaryngoscopy and intubation. NC/TMD and SVC predicted the need for manipulation with the highest accuracy. The BMI and Mallampati best correlated with tongue thickness, while the NC/TMD best correlated with the SVC and SHB.