Comparison of thyromental height test(TMH) with modified mallampati test and thyromental distance for prediction of difficult laryngoscopy: a prospective study

Introduction: No anesthesia is safe unless diligent efforts are made to secure and maintain an intact airway. Various tests have been in practice i.e., Modified Mallampati Test(MMT), Thyromental Distance(TMD), Sternomental distance and Upper lip bite test. No single test has been proved to be effective for predicting difficult laryngoscopy. We undertook this study to evaluate the effectiveness of Thyromental height(TMH) to predict the difficult laryngoscopy in comparison with MMT and TMD. We hypothesized that TMH is more accurate than MMT and TMD for predicting difficult laryngoscopy. Methodology: Sixty consecutive patients aged between 18 to 60 years of ASA grade 1 and 2 requiring GA for elective surgery were assessed for airway evaluation with MMT,TMD and Thyromental height test. After anaesthesia induction the best laryngoscopic view which lead to intubation was assigned as grade of 1 to 4 according to Cormack Lehane grading. Grade 3 and 4 were considered difficult. Results: Out of 60, 48 belonged to ASA grade 1 and 12 in grade 2.Incidence of difficult laryngoscopy was 6.6%. MMT & TMD appear to be more accurate than TMH. Conclusion: TMH appears to be simple, inexpensive, easily done test to predict difficult laryngoscopy, which is comparable in sensitivity & NPV but less accurate than MMT & TMD.