Preoperative Assessment to Predict Difficult Airway Using Multiple Screening Tests

Background Predicting a difficult airway is one of the necessities in anesthesiology practice. Recognition of an obviously difficult airway leads to a series of communication and preparations to assist, as well as the establishment and maintenance of the airway. In this study, we compared various predictors of difficult laryngoscopy/intubation to determine the best possible difficult airway predictors. The present study aimed to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of the following airway assessment tests to predict difficult airway: (1) Modified Mallamapati test; (2) thyromental distance; (3) inter-incisor gap; (4) upper lip bite test; (5) LEMON airway assessment test; and (6) atlantooccipital movement. Methodology A total of 300 patients who presented for different operative procedures were selected. Screening tests were done in the preoperative examination room. The tests included the Modified Mallamapati test, thyromental distance, upper lip bite test, inter-incisor gap, LEMON airway assessment, and atlantooccipital movement. Laryngoscopy was done in the operation theater and the view was classified according to Cormack-Lehane's scale. Using this clinical data, the sensitivity, specificity, PPV, and NPV of each test in predicting difficult airways were calculated. Results The thyromental distance test had the highest sensitivity, NPV, and accuracy. The upper lip bite test had the highest specificity and PPV. LEMON airway assessment test had the lowest specificity, PPV, NPV, and accuracy. Thyromental distance had the highest accuracy followed by the Modified Mallampati test. Inter incisor gap had low sensitivity and PPV, and the atlantooccipital extension test had low sensitivity. Conclusions The currently available screening tests for difficult intubation have only poor-to-moderate discriminative power when used alone. No single airway test can provide a high index of sensitivity and specificity for the prediction of difficult airways. The upper lip bite test had the highest specificity and the thyromental distance test had the highest NPV. Every anesthesiologist must be trained and equipped to deal with now much less common, unexpected failure to intubate.