Accuracy of modified thyromental height in predicting difficult laryngoscopy / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the accuracy of modified thyromental height (MTMH) in predicting difficult laryngoscopy.Methods Two hundred and sixty-three patients of both sexes requiring endotracheal intubation,aged over 17 yr,with body mass index less than 33 kg/m2,of American Society of Anesthesiologists physical status Ⅰ or Ⅱ,scheduled for elective surgery under general anesthesia,were selected.The modified Mallampati test (MMT) score,thyromental height (TMH) and MTMH ("sniffing" thyromental height) were assessed after admission to the operating room.MMT grade Ⅲ or Ⅳ was set as positive predicting index.Direct laryngoscope was placed after induction of anesthesia to expose the glottis,and difficult laryngoscopy was defined as Cormack-Lehane grade Ⅲ or Ⅳ after external laryngeal manipulation.The area under the receiver operating characteristics curve (AUC) was used to evaluate the accuracy of MMT,TMH and MTMH in predicting difficult laryngoscopy.Results Difficult laryngoscopy was found in 24 patients and non-difficult laryngoscopy in 239 patients,the incidence of difficult laryngoscopy was 10.0％,and there were no failed intubations.The AUC (95％ confidence interval) of MTMH in predicting difficult laryngoscopy was 0.966 (0.396-0.984),the best cut-off value was 46.83 mm,and Youden index was 0.8456.The sensitivity and specificity of MTMH in predicting difficult laryngoscopy was 91.67％ and 92.89％,respectively,and the odds ratio was 143.647.The AUC of MTMH in predicting difficult laryngoscopy was significantly enlarged when compared with that of MMT and TMH (P＜0.05).Conclusion MTMH can accurately predict difficult laryngoscopy with the best cut-off value of 46.83 mm in patients.