Evaluation of Ultrasound-guided Airway Assessment Indices in Patients with Unanticipated Difficult Intubation: A Prospective Observational Study

Background: Ultrasound-guided airway assessment has shown a potential role in improving the diagnostic accuracy of clinical tests. The aim of this study was to assess the role of the three common indices, including distance from skin to hyoid (DSH), distance from skin to epiglottis (DSE), and distance from skin to vocal cord (DVC), in predicting unanticipated difficult intubation (DI). Materials and Methods: Ninety-eight patients fulfilling the inclusion criteria were enrolled in this study. Ultrasound-guided airway measurements were recorded in the midline at three levels: hyoid bone, epiglottis, and vocal cords. An experienced anesthesiologist not involved in the ultrasound assessment performed the airway management, and intubation difficulty was recorded as per the intubation difficulty score (IDS). Patients with IDS >5 were graded as difficult, whereas those with IDS <5 were graded as easy. After analyzing the data, sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, area under the curve (AUC), and cutoff values were calculated for each of the three study parameters. Results: DSE showed the highest diagnostic accuracy with a sensitivity of 82.35%. The receiver-operating characteristic curve analysis revealed the highest AUC for DSE (0.791 with 95% confidence interval of 0.697–0.8660). The estimated cutoff for DSE >2.1 cm showed a highly significant association with DI ( P < 0.0001). Conclusions: Our study suggests that the preoperative assessment of DSE is the better predictor of DI as compared to DSH and DVC. Its high sensitivity may have a role in avoiding unanticipated DI.