Predictive value of upper lip bite test and ratio of height to thryromental distance for predicting difficult laryngoscopy in apparently normal Guajarati patients

Abstract

Background: Maintaining a patent airway in anesthetized patients is the important responsibility of an anesthesiologist. Objective: Study conducted with the objectives to evaluate sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), relative risk (RR), odd ratio (OR) and LR for various screening tests like upper lip bite test (ULBT), ratio of height to thyromental distance (RHTMD), inter incisor gap (IIG), modified Mallampatti Test (MMT), thyromental distance (TMD) and head and neck movement (HNM) in isolation. Materials and Methods: In this prospective, single blinded observational study, 480 adult patients of either sex, ASA grade I and II were assessed and graded for ULBT, RHTMD, TMD, MMT, IIG, and HNM according to standard methods and association with the Cormack and Lehane grade. Results: TMD, ULBT and RHTMD had highest sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio which was 46.67%, 95.45%, 63.64%, 91.3%, 4.94 and 46.67%, 92.05%, 50.0%, 91.01%, 5.13 and 40%, 90.91%, 42.85%, 89.89%, 4.45, respectively. Conclusion: Out of all the 6 predictive tests evaluated, TMD, ULBT and RHTDM are the best predictive test for difficult laryngoscopy.