The value of a method to reduce the exposure of the upper respiratory tract for predicting difficult laryngoscopy
Abstract Background: The current global situation of COVID-19 epidemic is serious. Routine preoperative methods to assess airway such as the interincisor distance(IID), Mallampati classification, and the upper lip bite test(ULBT) have a certain risk of upper respiratory tract exposure and virus spread. The condyle-tragus maximal distance(C-TMD) can be used to assess the airway, and the assessment method does not require the patient to expose the upper respiratory tract, but its value in predicting difficult laryngoscopy compared to other indicators (Mallampati classification, IID, and ULBT) remains unknown. The purpose of this study was to observe the value of C-TMD to predict difficult laryngoscopy and the influence on intubation time and intubation attempts, and provide a new idea for preoperative airway assessment during epidemic.Methods: We enrolled adult patients who underwent general anesthesia and tracheal intubation. The IID, Mallampati test result, ULBT result, and the C-TMD of each patient were evaluated prior to the initiation of anesthesia. The primary outcome were difficult laryngoscopy defined as the Cormack-Lehane Level > grade 2 , the number of intubation attempts and intubation time.Results: A total of 304 patients were successfully included in the study, 39 patients were identified as difficult laryngoscopy. The intubation time was shorter with the C-TMD >1 finger group 46.8±7.3s, compared with the C-TMD <1 finger group 50.8±8.6s (p<0.01).First attempt success rate was higher in the C-TMD >1 finger group than in the C-TMD <1 finger group (P<0.01).The correlation between the C-TMD and Cormack-Lehane Level was 0.317(Spearman correlation coefficient, P<0.001), and the area under the ROC curve was 0.699(P<0.01). The C-TMD <1 finger width was the most consistent with difficult laryngoscopy (κ=0.485;95%CI: 0.286-0.612) and its OR value was 10.09(95%CI: 4.19-24.28), sensitivity was 0.469(95%CI: 0.325-0.617), specificity was 0.929(95%CI: 0.877-0.964), positive predictive value was 0.676 (95%CI: 0.484-0.745), negative predictive value was 0.847(95%CI :0.825-0.865).Conclusion: Compared with the IID , Mallampati classification and ULBT, the C-TMD has higher value in predicting difficult laryngoscopy, which can become a more favorable airway assessment method during the epidemic of COVID-19.Trial registration: The study was registered on October 21, 2019 in the Chinese Clinical Trial Registry (ChiCTR1900026775).