The Accuracy Of Anterior Neck Soft Tissue Thickness Measurement Under Ultrasound In Evaluating Mask Ventilation Difficulty And Laryngoscope Exposure Difficulty

Objective:The accuracy of preoperative ultrasound measurement of anterior cervical soft tissue thickness in predicting difficult mask ventilation(DMV)and difficult laryngoscopy(DL)in patients undergoing elective endotracheal intubation under general anesthesia.Methods:From January 2022 to April 2022,a total of 190 patients,88 males and 102 females,aged 18-80 years,with body mass index(BMI)17.6-38.7 kg/m2,undergoing elective endotracheal intubation under general anesthesia in the Department of Anesthesiology,Jincheng People’s Hospital,were selected.American Society of Anesthesiologists(ASA)Classification Ⅰ～Ⅲ.General data collected one day before surgery included sex,age,height,weight,BMI,mouth opening,nail/chin distance,modified Mallampati airway classification,and ASA classification.The soft tissue thickness of the anterior neck was measured by ultrasound before anesthesia,the minimum distance from the hyoid bone to skin surface(DSHB),the minimum distance from the midpoint of the epiglottis to the skin surface(DSEM),the minimum distance from the anterior joint of the vocal cords to the skin surface(DSAC),the minimum distance from the thyroid isthmus to the skin surface(DSTI)and the minimum distance from the trachea to the skin surface at the jugular notch(DSTJ).Data were recorded by two different anesthesiologists: one anesthesiologist measured ultrasound distances(DSHB,DSEM,DSAC,DSTI,DSTJ)preoperatively,and the other anesthesiologist was responsible for general data collection;After anesthesia,mask ventilation grade(grade 3,grade 4: DMV)and laryngoscope exposure degree(grade≥Ⅱb: DL)were recorded according to mask ventilation grade and modified Cormack-Lehance(C-L)grade.Area under receiver operating characteristic curve(ROC curve).The curve(AUC)evaluates the accuracy of ultrasound indicators in predicting DMV and DL.Results:Among the 190 patients,182 cases were in the mask ventilation easy group(grade 1and 2).Grade 3 and 4 were DMV group,8 cases.Grade Ⅰ and Ⅱa were modified laryngoscope exposure easy group,133 cases;Grade Ⅱb,Ⅲ and Ⅳ were classified as DL group,57 cases.The mean values of all ultrasonic parameters increased with the increase of DMV and DL.The soft tissue thickness of anterior neck(DSHB,DSEM,DSAC,DSTI,DSTJ)was positively correlated.There was a positive correlation between the increase of the thickness of the five layers of anterior neck soft tissue under ultrasound and the incidence of DMV and DL,and the correlation between DSHB and DMV and DL was better than other ultrasound indicators.The Pearson correlation coefficient and 95%confidence interval of DMV were 0.316(0.172-0.439).The Pearson correlation coefficient and 95% confidence interval of DL were 0.337(0.185-0.478).The AUC,95%confidence interval,sensitivity,specificity and cut-off value of each ultrasound index were calculated according to the ROC curve.The AUC of DSHB under mask ventilation classification was 0.912.95% confidence interval(0.863-0.948);The sensitivity was100%,the specificity 83.5%,and the cut-off value was 1.04.The AUC of DSHB under modified laryngoscope grading was 0.701.95% confidence interval(0.630-0.765);The sensitivity was 63.2%,the specificity 75.2%,and the cut-off value was 0.91.Conclusion:Preoperative ultrasound measurement of anterior cervical soft tissue thickness can predict DMV and DL.Compared with other ultrasound indicators,DSHB has a certain predictive value for DL and DMV.DSHB > 1.04 indicated difficulty in mask ventilation.DSHB > 0.91 indicates difficulty in laryngoscope exposure.Ultrasound is a safe,noninvasive test that can be used as an aid in the preoperative evaluation of patients with suspected difficult airways.