Background: Compared with men, women often have a shorter interincisor distance and a shorter thyromental distance but are less likely to have difficult airway. The hypothesis is that the prediction criteria of difficult airway differ between men and women. The aim of this study was to investigate differences in the prediction criteria of anatomic predictors for difficult airways in men and women.
Methods: We enrolled adult patients who underwent general anesthesia and tracheal intubation. The interincisor distance, thyromental distance, modified Mallampati test results, upper lip bite test results, and tongue thickness of each patient were evaluated prior to the initiation of anesthesia. The primary outcome was difficult tracheal intubation. Receiver operating characteristic (ROC) curve analysis and Youden's index were used to determine the criteria for predictors in men and women.
Results: In total, 1059 men and 1195 women were examined. Compared with women, men had a higher incidence of difficult tracheal intubation (P<0.001). The cut-off values for predicting difficult tracheal intubation of the interincisor distance, thyromental distance, modified Mallampati test results, upper lip bite test results, and tongue thickness determined by Youden's index were ≤38 mm, ≤70 mm, >3, >2, and >62 mm, respectively, for men, and ≤33 mm, ≤65 mm, >2, >1, and >60 mm, respectively, for women.
Conclusions: The optimal cut-off values of predictors of difficult airway differ between males and females.