| Difficult airway refers to a clinical situation in which a professionally trained anesthesiologist with more than five years of clinical anesthesia experience encounters difficulty with facemask ventilation of the upper airway,difficulty with tracheal intubation,or both.The principal adverse outcomes associated with the difficult airways include(but are not limited to)damage to the teeth,airway trauma,unnecessary surgical airway,cardiopulmonary arrest,brain injury,and death.The Expert Consensus on Difficult Airway Management formulated by Chinese Society of Anesthesiology in 2009 pointed out that more than 50% of serious anesthesia-related complications are caused by improper airway management.However,more than 90% of difficult airways can be detected by preoperative assessment.Therefore,a comprehensive and standardized preoperative airway assessment has very important clinical significance.It can identify difficult airways in advance,reduce serious complications and mortality of anesthesia,and ensure the safety of patients during the peri-anaesthesia period.The most commonly used preoperative airway assessment are the clinical airway assessment methods,including interincisor distance,modified Mallampati classification,thyromental distance,head and neck mobility and laryngoscope exposure classification,etc.,each evaluation method has a certain sensitivity and specificity for the prediction of difficult airways.However,there is no single index that can accurately predict difficult airways.Ultrasonography has the advantages of safety,non-invasiveness,real-time imaging and reproducibility.It has become an important diagnosis and treatment method in anesthesiology,critical care medicine,emergency department and other clinical disciplines.In recent years,the application of ultrasound in airway management has made great progress,such as locating cricothyroid,predicting difficult airways,guiding tracheal intubation in real time,helping select the size of pediatric tracheal tube,assessing the degree of fullness of the patient,and predicting successful extubation,etc..Among them,the value of ultrasound in predicting difficult airways has received more and more attention from researchers.However,currently there are few ultrasonic airway indicators available,and the effectiveness of the prediction still needs to be determined by further research;Secondly,there are few reports on the application of ultrasound in airway assessment in children.Ultrasound measurement of the distance from skin to epiglottis,tongue volume,tongue thickness,temporomandibular joint mobility and the length of the geniohyoid muscle can be used to predict difficult airways in adults,but it is not clear whether these ultrasonic airway indicators can be used to predict difficult airways in children.Based on the above two problems in the application of ultrasound in the study of difficult airways prediction: there are few available indicators and whether it is suitable for children,the following experiments were designed in this study: The first step,ultrasonic measurement of midsagittal tongue cross-sectional area(CSA)and tongue width,and the tongue volume was the product of tongue CSA and tongue width.Taking these three tongue indicators as the research object,we investigated whether the midsagittal tongue cross-sectional area and tongue width measured by ultrasound have the ability to predict difficult airways,and verified the predictive value of tongue volume measured by ultrasound for difficult airways in adults.The second step,several ultrasonic airway indicators and clinical airway indicators that had been proven to have predictive value for difficult airways in adults were selected as the research objects,and the indicators that could be used to predict difficult airways in children were screened out,and then the predictive value of the selected clinical airway indicators and ultrasonic airway indicators were evaluated with appropriate evaluation indexes.Chapter Ⅰ Literature review1.Research progress in difficult airway management2.Current status of research on difficult airway management in children3.The role of ultrasound in airway assessmentChapter Ⅱ Research studySection 1.Effectiveness of Midsagittal Tongue Cross-sectional Area and Tounge Width Measured by Ultrasound to Predict Difficult AirwaysObjective:To study the predictive value of midsagittal tongue cross-sectional area and tongue width for predicting difficult laryngoscopy and difficult tracheal intubation.Methods:1.Preoperative airway assessment and grouping A total of 244 patients who needed general anesthesia for endotracheal intubation and aged 18 to 90 years were selected.Before anesthesia,demographic variables were collected and clinical airway assessments(including modified Mallampti classification,interincisor distance,and thyromental distance)were performed,then a curvilinear low-frequency probe was used for ultrasonography,and midsagittal tongue CSA and tongue width were measured.Tongue volume was derived from multiplying the midsagittal tongue CSA by the tongue width.After induction of anesthesia,the patients were subjected to laryngoscope exposure and tracheal intubation.According to the results of the Cormack-Lehane laryngoscopy exposure classification,the patients were divided into difficult laryngoscopy group(DL group)and non-difficult laryngoscopy group(NDL group).According to the results of intubation difficulty scale,patients were divided into difficult intubation group(DI group)and non-difficult intubation group(NDI group).2.Analyze the predictive ability of ultrasonic measurement of midsagittal tongue CSA,tongue width and tongue volume for predicting difficult laryngoscopy and difficult tracheal intubation.1)Statistically analyze whether there were statistical differences in midsagittal tongue CSA,tongue width and tongue volume between the DL group and the NDL group,and between the DI group and the NDI group.2)The receiver operating characteristic(ROC)curve and the Youden’s index were used to determine the cut-off value of each clinical and ultrasonic airway indicator for predicting difficult laryngoscopy and difficult tracheal intubation,and then according to the cut-off value of each indicator,the accuracy,sensitivity,specificity,positive predictive value and negative predictive value of each indicator for predicting difficult laryngoscopy and difficult tracheal intubation were calculated.Results:1.A total of 230 patients were included in the final statistical analysis,of which 28(12.2%)patients experienced difficult laryngoscopy,and 12(5.2%)patients experienced difficult tracheal intubation.2.Ultrasonic measurement of midsagittal tongue CSA and tongue volume could help identify patients with difficult laryngoscopy(tongue CSA:sensitivity was 0.71,specificity was 0.60;tongue volume: sensitivity was0.57,specificity was 0.82)and patients with difficult tracheal intubation(tongue CSA: sensitivity was 0.50,specificity was 0.97;tongue volume:sensitivity was 0.67,specificity was 0.83);Ultrasonic measurement of tongue width helped identify patients with difficult laryngoscopy(sensitivity was0.39,specificity was 0.89).3.The AUCs the ROC curve of midsagittal tongue CSA,tongue width and tongue volume for predicting difficult laryngoscopy was 0.68,0.65 and 0.71,respectively;And the AUC of the ROC curve of midsagittal tongue CSA,tongue width and tongue volume for predicting difficult tracheal intubation were 0.69,0.59 and 0.69,respectively.Conclusion:Midsagittal tongue CSA and tongue volume measured by ultrasound can be used to predict difficult laryngoscopy and difficult tracheal intubation;While the tongue width measured by ultrasound may be a weak predictor of difficult laryngoscopy.Section 2.The value of ultrasonic measurement of different airway indicators in predicting difficult laryngoscopy in childrenObjective:To evaluate the predictive value of ultrasonic measurements of tongue volume,midsagittal tongue CSA,tongue width,length of geniohyoid muscle and distance from skin to epiglottis for difficult laryngoscopy in children.Methods:1.Preoperative airway assessment and grouping A total of 287 children undergoing general anesthesia and tracheal intubation,aged 5 to 12 years old,were selected,including 194 males and93 females,with BMI of 10~39 Kg/m2.Before anesthesia,demographic variables were collected and clinical airway assessments(including modified Mallampti classification,interincisor distance,and thyromental distance)were performed,then the midsagittal tongue CSA,tongue width,length of geniohyoid muscle,and distance from skin to epiglottis were measured by ultrasound,and the tongue volume was derived from multiplying the midsagittal tongue CSA by the tongue width.After induction of anesthesia,the children were subjected to laryngoscope exposure.According to the results of Cormack-Lehane laryngoscopy exposure classification and their age,the children were divided into four groups: 5 to 8 years old with difficult laryngoscopy group(DL5 group)and 5 to 8 years old with non-difficult laryngoscopy group(NDL5 group),9to 12 years old group with difficult laryngoscopy(DL9 group)and 9 to 12 years old group with non-difficult laryngoscopy(NDL9 group).2.Analyze the predictive ability of above clinical airway assessment indicators and ultrasonic airway indicators for difficult laryngoscopy in children aged 5 to 12 years.1)Statistically analyzed whether there were statistical differences in the above airway assessment indicators(interincisor distance,thyromental distance and modified Mallampati classification,as well as ultrasonic assessment of midsagittal tongue CSA,tongue width,tongue volume,length of geniohyoid muscle and the distance from skin to epiglottis)between the DL5 group and the NDL5 group,and between the DL9 group and the NDL9 group.2)The ROC curve and the Youden’s index were used to determine the cut-off value of each clinical and ultrasonic airway indicator for predicting difficult laryngoscopy,and then according to the cut-off value of each indicator,the accuracy,sensitivity,specificity,positive predictive value and negative predictive value of each indicator for predicting difficult laryngoscopy were calculated.Results:1.The clinical airway assessment indicators had a good predictive effect on difficult laryngoscopy in children: the shortened interincisor distance for 5 to 8 years old children,the shortened thyromental distance for 9 to12 years old children and the increased modified Mallampati classification for 5 to 12 years old children.2.The shorten length of the geniohyoid muscle(5 to 8 years,<3.85 cm;9 to 12 years,<4.19 cm)and the increased distance from skin to epiglottis(5 to 8 years,>1.56 cm)evaluated by ultrasound were helpful to identify children with difficult laryngoscopy.3.The AUCs of ROC curve of the above clinical and ultrasonic airway indicators were all between 0.7 and 0.9.Conclusion:Ultrasonic measurement of the length of the geniohyoid muscle and the distance from skin to epiglottis can effectively predict difficult laryngoscopy in children.Section 3.Effect of ultrasonic measurement of tongue thickness on the prediction of difficult laryngoscope exposure in childrenObjective:To study the predictive value of tongue thickness evaluated by ultrasonography and the ratio of tongue thickness to thyromental distance for difficult laryngoscopy in children.Methods:1.Preoperative airway assessment and grouping A total of 292 children undergoing general anesthesia and tracheal intubation were selected,aged 5 to 12 years old,gender and BMI were not limited,and ASA grade I to II.Before anesthesia,clinical airway assessments(including mouth opening,thyromental distance,and modified Mallampti classification)were performed,then the tongue thickness was measured by ultrasound.After induction of anesthesia,the children’s Cormack-Lehane laryngoscopy exposure classification was recorded,According to the results of laryngoscopy exposure and their age,the children were divided into four groups: 5 to 8 years old with difficult laryngoscopy group(DL5 group)and5 to 8 years old with non-difficult laryngoscopy group(NDL5 group),9 to 12 years old group with difficult laryngoscopy(DL9 group)and 9 to 12 years old group with non-difficult laryngoscopy(NDL9 group).2.Analyze the predictive effects of clinical airway assessment indicators and ultrasonic measurement of tongue thickness on difficult laryngoscopy in children aged 5 to 12 years.1)Statistically analyzed whether there were statistical differences in the above airway assessment indicators(interincisor distance,thyromental distance and modified Mallampati classification,as well as ultrasonic measurement of tongue thickness)between the DL5 group and the NDL5 group,and between the DL9 group and the NDL9 group.2)The ROC curve and the Youden’s index were used to obtain the cut-off value of each clinical airway assessment indicator and ultrasonic measurement of tongue thickness for predicting difficult laryngoscopy,and then according to the cut-off value of each indicator,the accuracy,sensitivity,specificity,positive predictive value and negative predictive value of each indicator for predicting difficult laryngoscopy were calculated.Results:1.The predictive effect of clinical airway assessment indicators on difficult laryngoscopy in children: the reduced inter-incisor distance(<3.6 cm)had a predictive effect on difficult laryngoscopy in children aged5 to 8 years,the increased modified Mallampati classification(>2 levels)and Shortened thyromental distance(5 to 8 years old: <5.6 cm;9 to 12 years old: <5.4 cm)had a good predictive effect on difficult laryngoscopy in children aged 5 to 12 years.2.The increased tongue thickness(>4.5 cm)measured by ultrasound could be used to predict difficult laryngoscopy in children aged 5 to 8 years.3.The increased ratio of tongue thickness to thyromental distance(5 to8 years: >0.86;9 to 12 years: >0.94)and ratio of Mallampati classification to thyromental distance(5 to 8 years old: >0.35;9 to 12 years: >0.42)all had a predictive effect on difficult laryngoscopy in children aged 5 to 12 years.4.The AUCs of ROC curve of the above airway indicators were all greater than 0.7.Conclusion:The tongue thickness measured by ultrasound and the ratio of tongue thickness to thyromental distance may be both effective indicators of difficult laryngoscopy in children. |
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