Assessment of difficult airway by using various bedside screening tests for endotracheal intubation

Introduction: The aim and objective of this study was to predict difficulty in endotracheal intubation by employing various bed side screening tests in patients posted for surgeries under general anaesthesia. Various bedside tests were used individually and in combination to assess the sensitivity and specificity in order to determine their positive predictive value and negative predictive value. Materials and Methods: The preoperative airway assessment was conducted using multiple screening tests like interincisor gap, thyromental distance, modified mallampati test, sternomental distance and head and neck movement. Intubation was considered difficult if the view on the laryngoscopy was Cormack and lehane grade III or IV, three or more attempts at tracheal intubation, duration >10 min or if special maneuvers were required to facilitate intubation. The results were evaluated on the basis of sensitivity, specificity, positive and negative predictive values of these tests. Results: The sternomental distance test has the highest sensitivity and positive predictive value of 77.3% and 63.0% and negative predictive value of 93.2% resulting as the best individual test for predicting difficulty for intubation followed by mallampati test with sensitivity of 60.0% and negative predictive value of 92.7%. IIG + MMT + SMD combination resulted best with sensitivity, specificity, PPV and NPV of 98.8%, 26.7%, 88.4% and 80.0% respectively. Conclusion: When multiple predictors were taken into consideration there was a considerable reduction in the outcome of false positives and false negatives with significant improvement in sensitivity, positive predictive value and negative predictive value. The application of multiple predictors can reduce the frequency of unanticipated difficulty and unnecessary interventions related to over- prediction of airway difficulty. Keywords: Interincisor gap, Thyromental distance, Modified mallampati test, Sternomental distance, Head and neck movement, Difficult airway predictors.