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.