A Comparative Study On The Evaluation Method Of Difficult Airway Based On Ultrasonography And LEMON Method

Objective:1.To evaluate the clinical effect of the LEMON method in predicting Chinese patients with difficult airway.2.To establish a new comprehensive prediction model based on the upper airway anatomic parameters measured by ultrasonography.Then,analysis of the new comprehensive prediction model and LEMON method,which one is better in predicting difficult airway.Methods:The first part:A total of 1528 patients scheduled for surgery requiring tracheal intubation under general anaesthesia,680 males and 848 females,aged 18-83 years,were enrolled in the study.We used the LEMON method to assess airway conditions before anaesthesia and recorded the scores.After induction of general anaesthesia,we used ordinary laryngoscope to complete tracheal intubation and recorded Cormach-Lehane level and intubation times of every patient.The primary end point was difficult tracheal intubation.The secondary end point was difficult laryngoscopy.Receiver operating characteristic curve analysis and the area under the curve were used to evaluate the clinical effect of the LEMON method.We used the Youden index to analyze the predictive effect of the LEMON method.The second part:A total of 2030 patients scheduled for elective surgery requiring tracheal intubation under general anaesthesia,1011 males and 1019 females,aged 18-95 years,ASA physical status I or II,were enrolled in the study.We used the LEMON method to assess airway conditions before anaesthesia and recorded the scores.Ultrasonographic measurement of condylar mobility,hyoid-mental distance,tongue thickness and distance of 1/3 tongue root to submental skin were also recorded.After induction of general anaesthesia,we used ordinary laryngoscope to complete tracheal intubation and recorded Cormach-Lehane level and intubation times of every patient.The primary end point was difficult tracheal intubation.The secondary end point was difficult laryngoscopy.We calculated the odds ratio,sensitivity,specificity,positive predictive value and negative predictive value of each anatomic parameters measured by ultrasonography.We used the Youden index to analyze the predictive effect of each anatomic parameters measured by ultrasonography.Multiple Logistics regression analysis was used to establish a comprehensive prediction model.Receiver operating characteristic curve analysis and the area under the curve were used to compare the clinical effect of LEMON method and the comprehensive prediction model in predicting difficult airway.Results:The first part:The incidence of difficult laryngoscopy and difficult tracheal intubation were 6.9% and2.4%,respectively.The area under the curve of the LEMON method for predicting difficult laryngoscopy and difficult tracheal intubation were 0.884(95%CI 0.867-0.899)and 0.934(95%CI 0.921-0.946),respectively.The score based on the LEMON method prediction criteria for difficult laryngoscopy is 4,with the highest value in sensitivity(88.7%,95%CI 88.1-94.0)and specificity(74.8%,95%CI 72.5-77.1).The score based on the LEMON method prediction criteria for difficult intubation is 5,with the highest value in sensitivity(81.0%,95%CI 64.8-92.0)and specificity(92.3%,95%CI 90.8-93.6).The second part:Finally,there ware 127 cases with difficult laryngoscopy and 55 cases with difficult tracheal intubation.The incidence of difficult laryngoscopy and difficult tracheal intubation were 6.3% and 2.7%,respectively.We used the Youden index to analyze the predictive effect of each anatomic parameters measured by ultrasonography.The condylar mobility,hyoid-mental distance,tongue thickness and distance of 1/3 tongue root to submental skin measured by ultrasonography prediction criteria for difficult laryngoscopy are ?10.77 mm,?48.44 mm,>59.53 mm and >57.31 mm,respectively.The condylar mobility,hyoid-mental distance,tongue thickness and distance of 1/3 tongue root to submental skin measured by ultrasonography prediction criteria for difficult tracheal intubation are ?10.42 mm,?45.00 mm,>59.33 mm and >59.73 mm,respectively.In predicting difficult laryngoscopy,Multiple Logistics regression analysis showed that the condylar mobility,hyoid-mental distance,and tongue thickness measured by ultrasonography have independent prediction values.The area under the curve of the comprehensive prediction model and LEMON method are0.798(95%CI 0.780-0.815)and 0.803(95%CI 0.785-0.820),respectively.And there are no statistically significant difference between them(p > 0.05).In predicting difficult tracheal intubation,Multiple Logistics regression analysis showed that the condylar mobility and hyoid-mental distance measured by ultrasonography have independent prediction values.The area under the curve of the comprehensive prediction model and LEMON method are 0.862(95%CI 0.846-0.877)and 0.852(95%CI0.836-0.867),respectively.And there are no statistically significant difference between them(p>0.05).Conclusion: 1.Airway assessment score based on the LEMON method is able to successfully stratify the risk of difficult airway in Chinese patients and it has good clinical effect in predicting Chinese patients with difficult airway.2.The comprehensive prediction model based on parameters measured by ultrasonography is equivalent to the LEMON method in predicting difficult airway,which can predict difficult airway effectively.