Preoperative airway ultrasonography for predicting difficult intubation in adult female patients: a prospective...

Accurate preoperative prediction of difficult intubation is essential for perioperative safety. Ultrasonographic airway evaluation has emerged as a promising adjunct. However, heterogeneity in study populations has limited the identification of population-specific predictors. This study aimed to evaluate the diagnostic performance of four ultrasonographic airway parameters in non-obese, non-obstetric adult female patients.

This prospective, single-center, single-blinded observational study included adult women undergoing elective surgery. Preoperative airway ultrasonography was performed to measure tongue thickness, skin-to-hyoid bone distance, skin-to-epiglottis distance, and skin-to-anterior commissure of the vocal cords distance. Tracheal intubation was conducted using direct laryngoscopy by anesthesiologists blinded to ultrasonographic findings. Difficult intubation was defined as a restricted composite outcome: a Cormack-Lehane grade III-IV view on initial laryngoscopy plus either failed first-attempt intubation or requirement for adjunct techniques. Diagnostic performance was assessed using receiver operating characteristic analysis and multivariable logistic regression.

A total of 379 patients were analyzed, of whom 45 (11.9%) met the criteria for difficult intubation. Tongue thickness was significantly greater in patients with difficult intubation and demonstrated the highest predictive accuracy (AUC 0.92, 95% CI 0.87-0.98). Skin-to-anterior commissure distance showed moderate discriminatory ability (AUC 0.71), whereas other measurements had limited or poor performance. In multivariable analysis, tongue thickness emerged as the strongest independent predictor of difficult intubation.

Within this specific cohort, tongue thickness showed the highest discriminatory performance among the evaluated ultrasonographic parameters. Population-specific airway assessment using targeted ultrasonographic parameters may enhance preoperative risk stratification and support safer anesthetic practice.

NCT07343557 (retrospectively registered).