To evaluate the reliability of upper lip bite test and ultrasound guided airway assessment in predicting difficult intubation in elective surgeries under general anaesthesia: A prospective randomised trial

• Author Details:   
• Bhavini Shah
• Brinda Badam
• Reshma Salim ^*

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Background and Aims: Airway management is a crucial aspect of anaesthetic practice, and predicting difficult intubation is essential to avoid severe complications. While the Upper Lip Bite Test (ULBT) is a widely used bedside screening tool, it has limitations in accurately predicting difficult intubation. Ultrasound evaluation of the airway has emerged as a promising alternative. This study aimed to evaluate the reliability of the ULBT and anterior neck soft tissue measurement at the vocal cord level (ANS-VC) in predicting difficult intubation and its correlation with Cormack-Lehane (CL) grading, intubation attempts, technique modifications, and failed intubations.

Materials and Methods: This prospective observational study included 100 adult patients (ASA I–II) undergoing elective surgery under general anaesthesia. Preoperative ULBT and ultrasound evaluation of the anterior neck soft tissue at the vocal cord level (ANS-VC) were performed. Laryngoscopy was conducted by a blinded anaesthesiologist, and Cormack-Lehane (CL) grades were recorded. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of both ULBT and ANS-VC were calculated. Receiver Operating Characteristic (ROC) analysis was performed to determine the optimal ANS-VC cutoff value for predicting difficult intubation.

Results: ULBT demonstrated a sensitivity of 73.4%, specificity of 33.3%, and an overall accuracy of 65%. ANS-VC, with an optimal cutoff value of 0.33 cm, had a sensitivity of 73.4%, specificity of 71.4%, and an accuracy of 73%. The ANS-VC cutoff showed superior balanced predictive performance compared to ULBT. ULBT was more effective in terms of sensitivity, whereas ANS-VC demonstrated better specificity and a more balanced overall predictive performance.

Keywords: Airway management, Difficult intubation, Upper lip bite test, Ultrasound airway assessment, Cormack-Lehane grading, Predictive validity, Airway ultrasound.