Comparison of the Thyromental Distance, Thyrohyoid Distance, and Mallampati Scores in Prediction of Difficult Intubation in Patients Undergoing General Anaesthesia: An Observational Study

Abstract

Background: Several studies have been conducted to assess the accuracy of predictors of difficult intubation, but the results are still very variable. This study aims to discover the incidence of difficult intubation in our cohort. We also compared the accuracy of the Mallampati score, thyromental distance, and thyrohyoid distance in predicting intubation difficulties in patients who will undergo surgery under general anesthesia. Materials and Methods: This prospective, observational study was conducted on 100 subjects who met the inclusion and exclusion criteria and had their Mallampati score, thyromental distance, and thyrohyoid distance measured preoperatively. After inducing anesthesia, the degree of difficulty in intubation was assessed using the Cormack-Lehane grading. The Mallampati score, thyromental distance, and thyrohyoid distance were then tested for accuracy as predictors of the occurrence of difficult intubation using the binomial logistic regression. Results: The incidence of difficult intubation was 21%. We found a significant difference (P < 0.001) between the Mallampati score and the degree of intubation difficulty, where subjects with a Mallampati score of 1–2 experienced fewer intubation difficulties. The mean thyromental distance differed significantly between subjects with and without difficulty intubating (6.3 ± 0.6 vs. 4.6 ± 0.6 cm, P < 0.001). There was also a significant difference in the mean thyrohyoid distance between subjects with and without difficulty intubating (3.6 ± 0.4 vs. 2.0 ± 0.2, P < 0.001). Conclusion: Mallampati score, thyromental distance, and thyrohyoid distance were not significant as single predictors of difficult intubation, but they were significant when combined.

Keywords

• airway; general anesthesia; intubation; mallampati