Correlation between ultrasonographic evaluation of the airway and Cormack-Lehane view by direct laryngoscopy in the Indian subpopulation

Abstract

Background: An important aspect of airway management is assessment of the airway to predict difficult intubation. Ultrasonography has recently emerged as a noninvasive tool that is helpful for preoperative airway assessment and management. Patients and Methods: In this study, four sonographic measurements, namely (a) distance of the pre-epiglottic space (PES), (b) distance from epiglottis to the vestibular ligaments' midpoint (EVL), (c) skin to hyoid bone distance (DSHB) and (d) distance from the skin to epiglottis midway between hyoid bone and thyroid cartilage (DSEM) were correlated with the Cormack-Lehane grade obtained by direct laryngoscopy. Results: Of the 77 patients included for data analysis, 19 patients (24% of total) had difficult intubation. Of those with difficult intubation, 63% were female. Pearson's analysis revealed a correlation of Cormack-Lehane grade as weak negative with PES, weak positive with EVL, very weak positive with DSHB and very weak negative with DSEM. To predict difficult airway, the cutoff values for PES, EVL, DSHB and DSEM as determined by the Youden index were found to be 2.8 mm (sensitivity 21.1% and specificity 84.5%), 9.3 mm (sensitivity 36.8% and specificity 86.2%), 12.7 mm (sensitivity 42.1% and specificity 79.3%) and 6.8 mm (sensitivity 21.1% and specificity 87.9%), respectively. The area under the curves of PES, EVL, DSHB and DSEM were all below 0.6. Conclusion: PES, EVL, DSHB and DSEM are poor in predicting difficult intubation. These parameters can, however, be used to rule out difficult intubation because they are all highly specific.