| Objective: Laryngeal mask airway(LMA)is a kind of ventilating device above the glottis.With advantages of simple to operate,small traumatic stress,weak cardiovascular response and low incidence of postoperative complications,LMA has been widely used in clinic practice and become common ventilating device for airway management under general anesthesia in the world.It is important to choose an appropriate size of LMA for ensuring accurate location of LMA and safety of ventilation.Body weight is always recommended as the selection criterion of LMA by manufacturers.However,in clinical practice,it found that this criterion did not guarantee the accuracy of size selection of LMA,and had no abvious clinical advantages.Recently,the method of the size selection of LMA by visual inspecting the oral cavity volume of patients is the most commonly way for anesthetists,but there is still lack of research evidence.Therefore,this study aimed to explore the correlation between body weight,height,interincisor distance,angulus oris distance,mandibular angular distance,thyromental distance and the size selection of LMA,and find out factors influencing selection of the optimal size of LMA for females to provide a reasonable and effective method of the size selection of LMA for females and provide a guidance for ventilation management of LMA under general anesthesia.Methods: A total of 400 adult female patients,ASA I-II,aged 18-70 years old,who were administered with LMA for elective surgery under general anesthesia,were enrolled in the study.Patients with major systemic diseases,risk of reflux and aspiration,throat surgery history,and a need of head and neck surgery were excluded.Before surgery,body weight,height,interincisor distance,angulus oris distance,mandibular angular distance and thyromental distance of patients were measured.Then the LMA chosen empirically by another anesthetist was inserted after induction of anesthesia.Last,the number of insertion of LMA,the score of fiberoptic bronchoscopy and the oropharyngeal leak pressure were recorded.Independent sample t test or analysis of variance was used to single factor analysis;Logistic regression analysis was used to multivariate analysis.Predictive value of various factors on the size selection of LMA for females was evaluated by the receiver operating characteristic curve(ROC)and area under the curve(AUC).Results: In this study,a total of 400 adult female patients administered with LMA for elective surgery under general anesthesia were selected.Two of them were excluded as a result of endotracheal intubation instead of LMA after entering operation room.The result of single factor analysis showed that there was obvious correlation between body weight,interincisor distance,mandibular angular distance,angulus oris distance,thyromental distance and the size selection of LMA(p<0.05),but height had no relevance with the size selection of LMA(p>0.05).Logistic regression analysis showed there was also correlation between mandibular angular distance,interincisor distance,angulus oris distance,thyromental distance and the size selection of LMA,the OR value was 6.364,2.869,33.255,1.878,respectively.There was no correlation between body weight and the size selection of LMA.ROC curve analysis showed that the AUC of body weight,body mass index,angulus oris distance,mandibular angular distance,interincisor distance,thyromental distance and Logistic regression model new variable Pre-1 were 0.701,0.708,0.766,0.704,0.604,0.611,0.882,respectively.Conclusion: Weight,angulus oris distance,mandibular angular distance,interincisor distance and thyromental distance could affect the size selection of Supreme LMA for adult females.Angulus oris distance has higher reliability on determining the size selection of Supreme LMA for adult females.It suggested that body weight,body mass index,angulus oris distance,mandibular angular distance,interincisor distance and thyromental distance considered together to select the optimal size of LMA was superior to judgment just by body weight. |
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