Diagnostic Efficacy and Clinical Value of Ultrasonography in Difficult Airway Assessment: Based on a Prospective Cohort Study

Objective: A case-control study was conducted to explore the diagnostic efficacy and clinical value of ultrasound in difficult airway assessment.

Methods: A total of 220 patients undergoing elective surgery under general anesthesia were prospectively enrolled in our hospital from April 2018 to April 2021. General data were collected one day before operation, including sex, age, height, weight, body mass index (BMI), modified Mallampati test (MMT), inter-incisor distance (IID) and thyromental distance (TMD), the upper lip bite test (ULBT), and thyromental height (TMH). DSH, DSE, DSV, HMD, and tongue width and thickness were measured by ultrasound in the supine position before anesthesia induction on the day of operation. The above data were measured by the same anesthesiologist. After anesthesia, the patients were exposed to laryngoscope by the same senior doctor who did not participate in the data analysis, and the Cormack-Lehane (CL) grade was recorded and endotracheal intubation was completed. The relationship between DSE, DSH, DSV, HMD, and tongue width and thickness and laryngoscope exposure difficulty and tracheal intubation difficulty was analyzed. The critical value of each index for predicting laryngoscope exposure difficulty and tracheal intubation difficulty was obtained by the receiver operating characteristic curve (ROC) and Jordan index. According to the critical value, the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of each index were calculated.

Results: On comparing the general conditions of the four groups, this study prospectively included 220 patients undergoing elective surgery under general anesthesia for tracheal intubation in our hospital from April 2018 to April 2021, of which 8 cases were excluded from the study because of loss of incisors, 5 cases were excluded from the study due to unclear development of the anterior vocal cords under ultrasound, 7 cases were excluded from the study, and finally 200 patients were included in the study, including 104 males and 96 females. Among the 200 patients, difficult laryngoscope exposure was found in 26 cases (13.00%) and difficult tracheal intubation in 17 cases (8.50%). Tracheal intubation was performed in 17 patients with a visual laryngoscope and light rod, respectively. The weight and BMI of patients in the DL group were higher than in the NDL group, and the difference was statistically significant (P < 0.05); the weight and BMI of patients in the DI group were higher than in the NDI group, and the difference was statistically significant (P < 0.05); there was no significant difference in sex, age, and height between the DL group and the NDL group and the DI group and the NDI group (P > 0.05). Compared with the NDL group, IID, TMD, and TMH in the DL group were lower, and the difference was statistically significant (P < 0.05); there was no significant difference in ULBT (P > 0.05). DSE, DSH, and DSV were higher than in the NDL group, and the difference was statistically significant (P < 0.05), the HMD was lower than in the NDL group, and the difference was statistically significant (P < 0.05);the width and thickness of tongue were higher than in the NDL group, and the difference was statistically significant (P < 0.05). On comparing the DI NDI groups, the IID, TMD, and TMH in group DI were lower than in group NDI, and the difference was statistically significant (P < 0.05), but there was no significant difference in ULBT (P > 0.05); DSE, DSH, and DSV were higher than in the NDI group, and the difference was statistically significant (P < 0.05); the HMD was lower than in the NDI group, and the difference was statistically significant (P < 0.05); the width and thickness of tongue were higher than in the NDL group, and the difference was statistically significant (P < 0.05). The AUC of BMI, TMH, DSE, DSV, HMD, and tongue width and thickness all ranged from 0.70 to 0.9. Laryngoscope exposure difficulty diagnostic value was medium. The AUC of TMD, MMT, ULBT, IID, and DSH ranged from 0.5 to 0.7. The diagnostic value of laryngoscope exposure difficulty was low. According to the ROC curve, the AUC value of HMD, DSE, and tongue thickness in ultrasonic indicators was higher than that of traditional indicators and the AUC value of TMH was the highest in traditional indicators. When the HMD cutoff value was 5.29 cm; the accuracy, sensitivity, specificity, PPV, and NPV were 73.6%, 96.7%, 71.6%, 31.8%, and 97.4%, respectively. Compared with tongue width, tongue thickness has a better predictive performance. The accuracy of DSH, DSV, DSE, and tongue width and thickness in predicting difficult laryngoscope exposure was lower than HMD and the difference was statistically significant (P < 0.05). The patients in the DI and NDI groups indicated that the AUC of ULBT, TMD, and IID was between 0.5 and 0.7, the diagnostic values of BMI, MMT, TMH, DSE, DSH, DSV, HMD, and tongue width and thickness were between 0.7 and0.9, and the diagnostic value for tracheal intubation difficulty was moderate. According to the ROC curve, HMD, DSE, and tongue thickness in ultrasonic indexes were higher compared to traditional indexes. Among the traditional indexes, the AUC value of TMH is the largest. In ultrasonic indexes, when the critical value of HMD DSE is 4.85 cm, the AUC value is 0.893, and its accuracy, sensitivity, specificity, PPV, and NPV are 81.6%, 93.8%, 80.6%, 30.2%, and 99.5%, respectively. In ultrasonic indexes, the prediction performance is better, followed by the tongue thickness prediction performance. The accuracy of DSH, DSV, DSE, and tongue width and thickness in predicting difficult tracheal intubation was lower than in HMD, and the difference was statistically significant (P < 0.05).

Conclusion: Ultrasonic measurements such as DSH, DSE, DSV, HMD, and tongue width and thickness have predictive value for difficult airway;when the ultrasonic measurement of HMD is ˂5.29 cm, we should pay attention to the difficulty of laryngoscope exposure, and when DSE is ˂4.85 cm, we should watch out for difficult tracheal intubation. In terms of other ultrasound indexes, HMD is more valuable in predicting difficult airway.