Impact of Airway Ultrasound Measurements on the Success of Videolaryngoscopy in Predicting Difficult Airway

Upper airway ultrasonography has emerged as a promising tool for difficult airway assessment by enabling non-invasive, bedside, repeatable, and objective evaluation of airway anatomy. However, a substantial proportion of the existing literature has correlated ultrasonographic measurements with direct laryngoscopy findings. Whether these measurements retain their predictive value in the setting of videolaryngoscopy, and which ultrasonographic parameters best reflect technical intubation difficulty during videolaryngoscopic intubation, remain unclear. Furthermore, several studies have proposed specific cut-off values for upper airway ultrasonographic measurements to predict difficult laryngoscopy when direct laryngoscopy is used. However, these cut-off values may not be directly applicable to videolaryngoscopy because the improved glottic visualization provided by videolaryngoscopes fundamentally alters the relationship between airway anatomy and intubation difficulty.

Therefore, after obtaining a detailed medical history, including both general medical and difficult airway-related history, all patients underwent a comprehensive airway assessment. Conventional predictors of difficult airway were evaluated, including Mallampati classification, inter-incisor distance, thyromental distance, atlanto-occipital joint extension, neck circumference, and the upper lip bite test.

On the day of surgery, ultrasonographic measurements including the distance from the skin to the epiglottis (ESD), hyomental distance (HMD), tongue thickness (TT), and tongue cross-sectional area (CSA) will be obtained. Following these assessments, patients will be transferred to the operating room, where standard general anesthesia induction will be performed. Orotracheal intubation will subsequently be carried out using a videolaryngoscope. After intubation, the difficulty of mask ventilation, laryngoscopy, and orotracheal intubation will be evaluated by the anesthesiologist using established clinical assessment tools and scoring systems.