Improving bedside airway tests accuracy for predicting difficult laryngoscopy using ultrasound-measured skin-to-epiglottis distance

Background This study aimed to assess the accuracy of a composite score combining ultrasound-measured skin-to-epiglottis distance (DSE), Upper Lip Bite Test (ULBT), and Modified Mallampati Test (MMT) in predicting difficult airway. Methods In this prospective observational study, 250 adults scheduled for elective surgery were assessed preoperatively using ULBT, MMT, and ultrasound measurement of DSE. A composite airway score was calculated by assigning one point for each of the following: DSE > 2.0 cm, ULBT class > I, and MMT grade > II. Difficult laryngoscopy was defined as Cormack–Lehane grade > 2, and difficult intubation as an Intubation Difficulty Scale > 5. The outcomes were the ability of the score and individual tests to predict difficult airway using area under the receiver operating characteristic curve (AUC). Results The incidence of difficult laryngoscopy and intubation was 12.8% and 6.8%, respectively. The composite score showed superior predictive accuracy compared to individual tests, with AUCs (95% confidence interval) of 0.77 (0.72–0.82) for difficult laryngoscopy and 0.83 (0.78–0.88) for difficult intubation. A score > 1 had negative predictive values of 93% for difficult laryngoscopy and 97% for difficult intubation. When all three tests were negative, the composite score had a sensitivity and negative predictive value of 100% for predicting difficult intubation. Conclusion A composite airway score combining DSE, ULBT, and MMT can accurately predict difficult laryngoscopy and intubation. When all three parameters are negative, difficult intubation is very unlikely. Additionally, a score of < 2 rules out difficult laryngoscopy and intubation with 93% and 97% accuracy, respectively.