Ultrasonography versus conventional methods (Mallampati score and thyromental distance) for prediction of difficult airway in adult patients

Background: The poor reliability of traditional screening tools to identify a potentially difficult airway makes the difficult laryngoscopy and tracheal intubation rate remains at 1.5-13%.The hypothesis is that fat pads affect the view during direct laryngoscopy so the increasing thickness of pretracheal soft tissue or pre-epiglottic space could be strong predictors of difficult laryngoscopy as the mobility of the pharyngeal structures is impaired. Upon that, we aimed to evaluate ultrasound-measured distance from skin to epiglottis for prediction of difficult laryngoscopy in Egyptian population. Methods: This was a prospective single blind randomized clinical study conducted on 80 patients requiring general anesthesia.Preoperatively, airway evaluation was performed using three parameters including Mallampati score, thyromental distance and ultrasound-measured distance from skin to epiglottis at the level of thyrohyoid membrane. The primary outcome was to correlate ultrasound measured distance from skin to epiglottis with difficult laryngoscopy in Egyptian population using Cormack - Lehane grading. Results: Difficult laryngoscopy group displayed greater thickness of the ultrasound measured distance from the skin to epiglottis(2 +/- 0.3 cm versus 1.7 +/- 0.3 cm; p = 0.002). The cut-off point for difficult laryngoscopy was >1.85 cm with sensitivity of 80%, specificity of 70.8% and area under the receiver operating characteristic curve was 0.759. Mallampati score and thyromental distance had poor area under the curve = (0.651, 0.670 respectively). Conclusion: Our study revealed good correlation between ultrasonograohic measurement of the skin to epiglottis distance and Cormack-Lehane grade in Egyptian population, therefore it might be considered as a predictor of difficult laryngoscopy.