Hyomental distance ratio as the diagnostic predictor of difficulty in laryngoscopy

Abstract

The Hyomental Distance (HMD) has been used to estimate the mandibular space. This study has been undertaken with a purpose to evaluate the usefulness of the Hyomental Distance Ration (HMDR) for accurately predicting difficulty in visualisation of larynx in apparently normal patients. This prospective, single blinded, unicentric evaluation of airway screening tests for difficult laryngoscopy was conducted on 300 subjects, over the period of 24 months, with the approval of the Ethics committee, and written informed consent of the subjects. The sensitivity of HMDR with cut off value of 1.2 is 93.3%, specificity 81.7%, PPV 56%, NPV 98%. It showed a positive co-relation with Cormack-Lehane grading (p<0.05). It has overall Accuracy of 84%. The AUC is 0.88. When Modified Mallampati test & HMDR of cut-off value 1.17 are used in combination, 231(94%) cases of easy visualization of larynx and 46(84%) cases of difficulty in visualization of larynx were predicted correctly