Predictive values of pre-operative airway assessment for difficult laryngoscopy and tracheal intubation: Comparison of ratio of height to thyromental distance, modified Mallampati score, and upper lip bite test

Abstract

Background: Difficult airway management continues to be the single most common cause of morbidity and mortality attributable to anesthesia. Aims and Objectives: The aim is to assess the ratio of height to thyromental distance (RHTMD), modified Mallampati score (MMS), and upper lip bite test (ULBT) and to compare the predictive value of a single or combinations of tests for the prediction of difficult airway intubation. Materials and Methods: This prospective observational study was carried out over a period of 24 months on 248 patients planned for elective surgeries under general anesthesia with intubation, who were examined clinically. The statistical software Statistical Package for the Social Sciences version 20 has been used for the analysis with P=0.05. Results: Maximum (35.1%) was in 31–40 years of age group and 53.6% was female. 5.6%, 28.2%, and 9.7% were clinically assessed as difficult airways according to ULBT, MMS, and Cormack and Lehane’s grade, respectively. 90.3% patients had an easy intubation and 9.7% patients needed assisted intubation. RHTMD had the highest sensitivity (70.83) with a good specificity (95.09), good positive predictive value (PPV) (60.71), and the highest negative predictive value (NPV) (96.82). Combination of tests showed the highest sensitivity with RHTMD and MMS (62.50), highest specificity with TMD and ULBT (99.55) and RHTMD and ULBT (99.55), highest PPV with TMD and ULBT (90.00) and RHTMD and ULBT (90.00), and highest NPV with RHTMD and MMS (95.95). Conclusion: During pre-operative airway assessment, we should not rely upon any single test; a combination of tests should always be done.