Difficult intubation is a significant cause of mortality and morbidity related to anesthesia. We decided to evaluate the value of Modified Mallampati Score, Upper Lip Bite Test and Facial Angle in the prediction of difficult intubation.
In a prospective descriptive study, data from 132 patients who were candidates for elective maxillofacial surgeries under general anesthesia were gathered. Facial Angles were measured by a maxillofacial surgeon according to cephalometry. The Modified Mallampati Score and Upper Lip Bite Test were first measured by an anesthesiologist and then another anesthesiologist was assigned to record the Cormack and Lehane score during the intubation. Grades 3 and 4 were considered as difficult intubation. Sensitivity, specificity, positive predictive value, negative predictive value and Youden index were calculated for all tests.
Difficult intubation was reported in 12% of the patients. Facial Angle≤82.5° can predict difficult intubation with 87.5% sensitivity and 88.8% specificity. Among the three tests, a high Modified Mallampati Score had the highest specificity (94.5%) and a high Modified Mallampati Score and Facial Angle (FA≤82.5°) had the highest sensitivity (87.5%). The highest NPV, sensitivity and Youden index were observed when using Facial Angle with the Modified Mallampati Score or with Upper Lip Bite Test.
Facial Angle has a high sensitivity, NPV and Youden index for the prediction of difficult intubation, but the best result is achieved when Facial Angle is used in combination with either the Modified Mallampati Score or Upper Lip Bit Test.