| Background:Difficult airway is one of the major factors that endanger the safety of preoperative patients.Patients' lives are often threatened in the event.Accurate to screen out difficult airway patients can help reducing the risk of the relevant risk.Although there have been many kinds of difficult airway prediction method based on identifying the face or body surface anatomy in clinical application,but their predictive accuracy was low.We think that accurately predicting relies on accurate detection on upper airway anatomy.Compare to CT or MRI,ultrasonographic imaging has the characteristics of convenient,harmless,and the low cost.Preliminary studies confirmed that ultrasonography can be implemented to detect the upper airway anatomy.However,whether this method can be applied to predict difficult airway is remain unclear.Objective:The present study was aimed to investigate that: 1.Whether accurate measurement of upper airway parameters can improve their ability to predict difficult airway or not;2.The feasibility and reliability of ultrasonographic measurement of hyoid-mental distance and condylar mobility of temporomandibular joint;3.The efficiency of hyoid-mental distance and condylar mobility of temporomandibular joint evaluated by ultrasonography in predicting difficult airway;and 4.How to establish comprehensive prediction model based on ultrasonographic precise anatomic parameters and to investigate it's predictive value.Methods:The first part:We conducted a case cohort prospective and observational study.Adult patients undergoing general anesthesia and intubation for elective surgery were included.Accurate measurement of mouth opening,and rough estimate of mouth opening based on finger breadth was assessed preoperative.After induction of general anesthesia,the results of endotracheal intubation were assessed by an attending anesthesiologist.The primary outcome was difficult laryngoscopy;the secondary outcome was difficult intubation.Areas under the ROC curve were calculated and compared for each method to predict difficult airway.The second part:We had recruited 20 healthy adult volunteers.Two ultrasonographers detected their hyoid-mental distance and condylar mobility respectively and independently.And one ultrasonographer detected condylar mobility on two sides of the volunteers.The correlation between the two inspectors' measurement results,repeat reliability,and difference were analyzed.The third part:We conducted a prospective and observational case cohort study.Adult patients undergoing general anesthesia and intubation for elective surgery were included.Mouth opening,body mass index,grade of Mallampati,ultrasonographic measurement of hyoid-mental distance and condylar mobility were assessed preoperative.After intubation of general anesthesia,the consequences of endotracheal intubation were evaluated by an attending anesthesiologist.The primary outcome was difficult laryngoscopy;the secondary outcome was difficult intubation.Areas under the ROC curve were calculated and compared for each method to predict difficult laryngoscopy and difficult intubation.The best cutoff values of hyoid-mental distance and condylar mobility were determined by Youden index.The fourth part:Based on the data of third part,firstly,single variable Logistic regression analysis for predicting difficult laryngoscopy and difficult intubation were performed.Variables significant statistically in single variable analysis were included in a multivariate Logistic regression analysis,and to identify independent predictors.A comprehensive prediction model was established.And its efficiency in predicting difficult laryngoscopy and difficult intubation were analyzed.Results:The first part:A total of 732 patients were successfully included in statistical analysis.Of them,67 cases with difficult laryngoscopy,and 25 patients with difficult intubation.For predicting difficult laryngoscopy,accurate measurement of mouth opening owned an area under the ROC curve of 0.72,with statistically significant difference(P < 0.001)when compare to that of rough estimate of mouth opening(mouth opening < 3 finger: 0.63;mouth opening < 2 finger: 0.57).For predicting difficult intubation,accurate measurement of mouth opening owned an area under the ROC curve of 0.82,with statistically significant difference(P < 0.001)when compare to that of rough estimate of mouth opening(mouth opening < 3 finger: 0.67;mouth opening < 2 finger: 0.65).The second part:We successfully recruited 20 healthy volunteers,hyoid-mental distance of two ultrasonographers measurements were 5.2 ± 0.4cm,5.1 ± 0.4cm,respectively,with a correlation coefficient r of 0.95(P < 0.01),a Krippendorff's alpha value of 0.91.Paired t test showed that there was no statistically significant difference(P = 0.119).Condylar mobility two ultrasonographers measurements were 1.40 ± 0.29 cm,1.38 ± 0.26 cm,correlation r = 0.96,P < 0.01),Krippendorff's alpha value is 0.92,paired t test showed that there was no statistically significant difference(P = 0.204).Bilateral condylar mobility of one ultrasonographer measurements were 1.36 ± 0.25 cm for the left side,and 1.39 ± 0.26 cm for the right side,with a correlation r = 0.97(P < 0.01),and a Krippendorff 's alpha value of 0.95.Paired t test showed that there was no statistically significant difference(P = 0.665).The third part:A total of 2357 patients successfully recruited in statistical analysis.Of them,159 cases with difficult laryngoscopy,and 62 patients with difficult intubation.For predicting difficult laryngoscopy,hyoid-mental distance owned an area under the ROC curve of 0.81,and condylar mobility owned a highest area under the ROC curve of 0.92,with statistically significant difference(P < 0.001)when compare to that of other methods.For predicting difficult intubation,hyoid-mental distance owned an area under the ROC curve of 0.86,and condylar mobility owned a highest area under the ROC curve of 0.97,with statistically significant difference(P < 0.001)when compare to that of other methods.The fourth part:In predicting difficult laryngoscopy,multivariate Logistic regression analysis showed that men,grade of Mallampati > 2,hyoid-mental distance < 5.0 cm,and condylar mobility < 1.1 cm have independent predictive values.Regression model has an area under the ROC curve of 0.96.In predicting difficult intubation,multivariate Logistic regression analysis showed that men,mouth opening < 4.0cm,hyoid-mental distance < 5.0 cm,and condylar mobility < 1.1 cm have independent predictive values.Regression model has an area under the ROC curve of 0.98.Conclusion:1,Accurate measurement of upper airway anatomic parameters can help to improve the prediction effect of difficult airway.2,Hyoid-mental distance and condylar mobility can be accurately assessed by ultrasonography.And the results own good reliability.3,Hyoid-mental distance and condylar mobility assessed by ultrasonography have independent predictive values to predict difficult airway.4,the new comprehensive regression model,including new ultrasonographic methods,further improve the prediction ability for predicting difficult airway... |
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