This study will evaluate how well an ultrasound measurement of the distance from the skin to the epiglottis, when combined with the modified Mallampati score, can predict difficult laryngoscopy in adult patients undergoing elective surgery under general anesthesia. Adult patients scheduled for surgery requiring tracheal intubation will be randomly assigned to two assessment strategies before anesthesia: one group will have the usual bedside airway assessment with modified Mallampati alone, and the other group will have modified Mallampati plus a quick, painless ultrasound scan of the front of the neck to measure the skin-to-epiglottis distance. During intubation, the anesthesiologist, who is blinded to the preoperative assessments, will grade the laryngoscopic view using the Cormack-Lehane classification, and the investigators will compare how accurately each assessment approach predicts difficult laryngoscopy (grade 3-4). The study does not change how anesthesia or airway management is performed; ultrasound and clinical assessments are added solely for measurement and data collection, with minimal risk to participants and potential future benefits in improving airway risk stratification and patient safety.
Adults aged 18-65 years.
ASA physical status I-II.
Scheduled for elective surgery under general anesthesia requiring tracheal intubation with direct laryngoscopy.
Able to provide written informed consent.
Emergency surgery.
Known or suspected difficult airway requiring planned alternative intubation technique (e.g., awake fiberoptic).
History of significant upper airway pathology, neck mass, prior neck surgery, or radiation affecting airway anatomy.
Limited mouth opening, cervical spine instability, or contraindication to standard sniffing position.
Parallel
Ultrasound-Guided Skin-to-Epiglottis Distance Measurement
Diagnostic testPoint-of-care airway ultrasound of the anterior neck using a high-frequency linear probe (10-13 MHz) placed transversely at the thyrohyoid membrane to measure the vertical skin-to-epiglottis distance in millimeters. The scan is performed preoperatively in supine neutral position, is non-invasive and painless, and does not alter anesthetic or airway management, which follow standard clinical practice. This measurement is combined with the modified Mallampati score in the experimental arm to predict difficult laryngoscopy (Cormack-Lehane grade 3-4).
Clinical Airway Assessment With Modified Mallampati Score
Diagnostic testStandard preoperative bedside airway assessment using the modified Mallampati score without airway ultrasound; performed in the sitting position with mouth opening and maximal tongue protrusion, used routinely to anticipate difficulty of laryngoscopy.
Diagnostic accuracy of Ultrasonographic Skin-to-Epiglottis Distance plus Mallampati vs Mallampati alone for difficult laryngoscopy
Area under the receiver operating characteristic (ROC) curve (AUC) of the combined ultrasound skin-to-epiglottis distance plus modified Mallampati score compared with the AUC of the modified Mallampati score alone for predicting difficult laryngoscopy, defined as Cormack-Lehane grade 3-4 on first direct laryngoscopy attempt.
Correlation between skin-to-epiglottis distance and Cormack-Lehane grade
Pearson or Spearman correlation coefficient between the ultrasound-measured midline skin-to-epiglottis distance and the Cormack-Lehane laryngoscopic grade recorded on the first intubation attempt in all patients who undergo airway ultrasound.
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