The aim of this observational study is to evaluate the accuracy of the HMDR combined with the ULBT as a predictor of difficult laryngoscopy in obese patients undergoing elective surgery under general anesthesia, regarding:
* Correlation of HMDR-ULBT values with Cormack-Lehane grades during laryngoscopy. * Comparison of HMDR-ULBT with standard HMDR in predicting difficult laryngoscopy.
Adult obese patients aged 18 to 65 years.
Both sexes.
American Society of Anesthesiologists (ASA) physical status II- III.
Body Mass Index (BMI) ≥ 30 kg/m² (classified as obese).
History of maxillofacial trauma, surgery, or congenital facial anomalies affecting mandibular movement or neck anatomy.
Known or suspected difficult airway requiring awake intubation.
Patients with limited neck mobility (e.g., cervical spine disease or immobilization).
Temporomandibular joint disorders or restricted mandibular mobility.
Single group
Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite test
Diagnostic testHyomental distance will be measured using ultrasound in three positions: neutral head position, maximum head extension, and during the upper lip bite test (ULBT).
Prediction of difficult laryngoscopic view, defined as Cormack-Lehane Grade 3 or 4 on the first laryngoscopy attempt without external laryngeal manipulation.
Difficult laryngoscopic view is defined as Cormack-Lehane Grade III or IV during the first laryngoscopy attempt without external laryngeal manipulation Cormack-Lehane classification for laryngoscopic view : grade 1: most of the vocal cords is seen; grade 2: only the posterior part of the vocal cords or the arytenoid cartilages are seen; grade 3: only epiglottis is seen; grade 4: epiglottis is not seen.
Determination of an optimal cutoff value for HMDR-ULBT to predict difficult laryngoscopy.
Receiver operating characteristic (ROC) curve analysis will be performed to determine the optimal cutoff value of the hyomental distance ratio measured during the upper lip bite test (HMDR-ULBT) for predicting difficult laryngoscopic view, defined as Cormack-Lehane Grade III or IV on the first laryngoscopy attempt without external laryngeal manipulation. The area under the ROC curve (AUC), sensitivity, specificity, positive predictive value, and negative predictive value corresponding to the optimal cutoff value will be calculated.
Comparison of HMDR-ULBT with standard HMDR in predicting difficult laryngoscopy.
The predictive performance of the hyomental distance ratio measured during the upper lip bite test (HMDR-ULBT) will be compared with that of the standard hyomental distance ratio (HMDR) for predicting difficult laryngoscopic view, defined as Cormack-Lehane Grade III or IV during the first laryngoscopy attempt without external laryngeal manipulation. Diagnostic accuracy parameters, including sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating characteristic (ROC) curve, will be compared between the two methods.
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