An Observational Study for the Comparison of Upper Lip Bite Test with the Measurement of Thyromental Distance for the Prediction of Difficult Intubation

Abstract

Introduction: Difficulties in laryngoscopy and tracheal intubation occur in 1.5% to 13% of patients undergoing general anesthesia, presenting a persistent concern for anesthesiologists. The Upper Lip Bite Test (ULBT) and Thyromental Distance (TMD) represent distinct methods for preoperative airway assessment. While ULBT evaluates temporomandibular joint movement, TMD measures the distance between the laryngeal prominence and the mental protuberance. This observational study aims to systematically compare the effectiveness of ULBT and TMD in predicting difficult intubation, contributing valuable insights for refining preoperative airway assessment protocols.

Aim and Objective: The aim is to compare the Upper Lip Bite Test with the measurement of thyromental distance for the prediction of difficult intubation. The objective is to compare the sensitivity, specificity, positive predictive value, and negative predictive value of ULBT and TMD for predicting difficult intubation.

Materials and Methods: This prospective, observational, single-blind study involved thirty patients scheduled for elective intubation. ULBT and TMD assessments were conducted during preoperative evaluation, and difficulty prediction was recorded. Laryngoscopic views were documented post-induction using the Cormack Lehane classification. Inclusion criteria encompassed age, consent, ASA grades I and II, and elective surgery; exclusion criteria included refusal, airway history, tumors, and restricted mobility.

Results: The comparative analysis between ULBT and TMD for predicting difficult and easy intubation. ULBT exhibited perfect sensitivity (100%) and high specificity (96.4%), with a positive predictive value of 66.7% and a negative predictive value of 100%. TMD showed 60% sensitivity, 96% specificity, a positive predictive value of 75%, and a negative predictive value of 92.3%.

Conclusion: The study concludes that ULBT, assessing temporomandibular joint movement, outperforms TMD in predicting difficult intubation. Incorporating ULBT into routine preoperative assessments enhances patient safety. A nuanced approach, considering patient-specific factors, is crucial. Future research should explore larger populations for generalizability. This study contributes valuable insights to anesthesia practice, aiding clinicians in informed decision-making for airway assessments.