This is a prospective, randomized, double-blinded controlled study designed to evaluate whether combining preoperative ultrasonographic skin-to-epiglottis distance (SED) with the modified Mallampati score improves prediction of difficult laryngoscopy compared with the modified Mallampati score alone in adult elective surgical patients undergoing tracheal intubation under general anesthesia. Eligible patients will be randomly assigned to one of two groups: Group A will undergo standard preoperative airway assessment including modified Mallampati score only, while Group B will receive both modified Mallampati assessment and ultrasound measurement of SED using a standardized anterior neck scanning protocol in the preoperative area.
All patients will subsequently undergo direct laryngoscopy for tracheal intubation in the operating room, performed by an experienced anesthesiologist who is blinded to the preoperative airway assessment results; the Cormack-Lehane laryngoscopic view during the first intubation attempt will be recorded as the reference standard for defining difficult laryngoscopy (grade 3-4). Additional data collected will include age, sex, body mass index, relevant comorbidities, and type of surgery to allow adjustment for potential confounders. The primary endpoint is the diagnostic accuracy (area under the receiver operating characteristic curve) of SED plus modified Mallampati versus modified Mallampati alone for predicting difficult laryngoscopy. Secondary endpoints include the correlation of SED with Cormack-Lehane grade, sensitivity, specificity, and predictive values of each assessment strategy, and exploratory subgroup analyses in higher-risk patients such as those with obesity.
