Ultrasound measurement of anterior neck soft tissue and tongue thickness to predict difficult laryngoscopy - An observational analytical study

BACKGROUND AND AIMS: Airway ultrasound is an emerging tool to predict difficult laryngoscopy. This study aimed to determine the utility of ultrasound measurement of the anterior soft tissue neck thickness at the level of hyoid, thyrohyoid membrane and thickness of tongue to predict difficult laryngoscopy and compare them with clinical parameters for airway assessment. METHODS: The distance from skin to hyoid bone, skin to the thyrohyoid membrane in neutral and sniffing position and maximum tongue thickness was measured by ultrasound and correlated with Cormack Lehane (CL) laryngoscope view in 310 adult surgical patients. Receiver operating characteristic curve was plotted and the area under the curve was calculated for each parameter. The sensitivity and specificity of ultrasound-guided parameters were compared with clinical parameters like the inter-incisor gap, modified Mallampatti classification, thyromental, sternomental distance and neck circumference. RESULTS: Incidence of difficult laryngoscopy (CL grade-III and IV) was 11.3%. A significant difference was observed in the ultrasound parameters between the easy and difficult laryngoscopy (P-value = 0.001). Sensitivity and specificity to predict difficult airway was 69.6% and 77% for tongue thickness, 68% and 73% for the skin to hyoid bone distance in a neutral position and found to be higher than clinical parameters. CONCLUSION: The ultrasound measurements of soft tissue thickness of the anterior neck and tongue thickness along with the clinical assessment of airway can be useful in predicting difficult laryngoscopy.