Diagnostic Value of Upper Lip Bite Test combined with Hyomental Distance Ratio in assessing the airway

Abstract

INTRODUCTION Airway assessment before any type of anesthesia is mandatory. Upper lip bite test (ULBT) is a relatively new test for assessing the airway. Range of freedom of mandible and dental architecture has a significant role in facilitating intubation, both of which are assessed by this single test. ULBT with good neck movements are sufficient criteria for assessing the airway. Hyomental distance ratio (HMDR) assesses the range of neck movements. So by combining these two tests we expect an increase in reliability and validity. METHODS Preoperatively we assessed the airway using ULBT, HMDR, and Mallampati (MP) tests of 300 patients. The anesthesiologist doing laryngoscopy is blinded to the results of pre op airway evaluation. Direct laryngoscopies are graded using the modified Cormack and Lehane scale. Difficult laryngoscopy was defined as Grade 3 or 4 view. ULBT class 3, and HMDR with optimal cutoff point 1.2 are considered as difficult intubation predictors. Sensitivity, Specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV) and Accuracy of both ULBT and HMDR separately and then both in combination are calculated and compared with those of MP. RESULTS ULBT:-Sensitivity - 88.2%, Specificity - 99.62%, PPV - 96.77%, NPV - 98.51%, Accuracy - 98.33% HMDR: - Sensitivity - 88.2%, Specificity – 99.25%, PPV - 93.75%, NPV - 98.50%, Accuracy - 98.00% MP: - Sensitivity - 17.65%, specificity - 88.72%, PPV - 16.67%, NPV - 89.39%, Accuracy - 80.66% ULBT+HMDR: - Sensitivity - 82.35%, specificity-100%, PPV100%, NPV97.75%, Accuracy - 98.00 % CONCLUSION Upper Lip Bite test is good screening test for assessing the airway. ULBT in combination with HMDR increased the specificity and positive predictive value.