COMPARISON OF THYROMENTAL HEIGHT TEST (TMHT) WITH MODIFIED MALLAMPATI SCORE, THYROMENTAL DISTANCE, NECK CIRCUMFERENCE, NECK EXTENSION AND INTER INCISOR GAP, AS A PREDICTOR OF DIFFICULT LARYNGOSCOPY: A PROSPECTIVE STUDY

Abstract

Introduction: Anticipating and preparing for difficulty in airway management is crucial. There are many bedside physical examination indices available for prediction of difficult laryngoscopy and intubation. These tests are easy to perform and cost effective. We have tried to evaluate the role of Thyro Mental Height Test (TMHT) as a simple bedside difficult airway predictive test and compared it with Modified Mallampati test (MMT), Thyro Mental Distance (TMD), Neck Circumference (NC), Neck Extension (NE) and Inter Incisor Gap (IIG). We hypothesized that TMHT is more accurate than MMT, TMD, NC, NE and IIG.

Method: 100 consecutive patients aged between 18-65 years of ASA grade 1 and 2 requiring GA for elective surgery were assessed for airway evaluation with TMHT, MMT, TMD, NC, NE and IIG. 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: Sensitivity of TMHT, MMT, TMD, NC, NE and IIG were 91.67 %, 75%, 25%, 25%, 50% and 58.33%, respectively. Highest sensitivity of TMHT means it is a good test to predict difficult intubations. Specificity of TMHT, MMT, TMD, NC, NE and IIG were 92.05 %, 88.64%, 72.73%, 16%, 70.45%, 86.36%, respectively. Highest specificity of TMHT means it is a good test to predict easy intubations. Accuracy of TMHT (92%) was higher than other tests, which testifies that the TMHT carries lower false positive and negative values in predicting a difficult laryngoscopic view.

Conclusion: Our study demonstrated that the Thyromental Height Test (TMHT) is the best predictive test for difficult laryngoscopy out of all the predictive tests evaluated.