Value Of Existing Airway Assessments For Predicting Difficult Endotracheal Intubation With Visual Rigid Laryngoscopes

Objective Visual rigid laryngoscope has been increasingly used in endotracheal intubation under general anesthesia.However,the traditional bedside assessment methods used to predict difficult endotracheal intubation are still the standard for visual rigid laryngoscopy assisted intubation to predict difficult endotracheal intubation,and there is no special method to evaluate the difficult endotracheal intubation for visual rigid laryngoscope assisted endotracheal intubation.This study is to explore whether the predictors of difficult endotracheal intubation for Macintosh laryngoscopy assisted endotracheal intubation can also predict the difficult endotracheal intubation for visual rigid laryngoscope assisted endotracheal intubation,in order to determine which demographic or morphological factors can predict difficult endotracheal intubation assisted with visual rigid laryngoscope.In the end,we want to provide a reference for preoperative airway assessment for visual rigid laryngoscope assisted endotracheal intubation.Methods Five hundred patients(aged 18～85yr)underwent general anesthesia endotracheal intubation were assigned in this study.Recording the basic information such as gender,age,height,weight,BMI,ASA classification and airway related history,as well as mouth opening,thyromental distance,modified Mallampati test,incisors protrusion,upper lip bite test,neck backwardness,neck circumference and neck length,mandibular length and other physical examination.The endotracheal intubation was completed with the visual rigid laryngoscope by midline approaching through the mouth.Meanwhile,we record the visual classification of rigid laryngoscope,intubation time and the times of intubation.Moreover,we record the sore throat and hoarseness of the patient after operation.Intubation time and the times of intubation were used as the dependent variables,gender,age,BMI,mouth opening,thyromental distance,modified Mallampati test,incisors protrusion,upper lip bite test,neck backwardness,neck circumference,neck length,mandibular length,thyromental distance/height,snoring and small mandible were used as the independent variables.Variable screening was performed using a stepwise screening method and multiple linear regression analysis was used to derive a multiple linear regression equation.P<0.05 was considered as statistically significant.Results Twenty patients were excluded and a total of 480 patients were included in the analysis.Among them,465 cases completed endotracheal intubation at the first attempt,14 cases completed endotracheal intubation at the second attempt,and one case completed tracheal intubation at the third attempt.The mean intubation time was(17.38±7.81)s.Small mandible(X1)and neck circumference(X2)went into regression equation through multiple linear-regression analysis where the times of intubation(N)was dependent variable.Multiple linear-regression equation was shown as N =1.196+0.063X1-0.005X2.The times of intubation was positively related with small mandible,while negatively related with neck circumference.Small mandible(X1),age(X3)and incisors protrusion(X4)went into regression equation through multiple linear-regression analysis where intubation time was dependent variable.The multiple-linear regression equation was shown as T=5.365+3.713X1+0.076X3-1.941X4.Intubation time was positively related with small mandible and age,while negatively related with incisors protrusion.Through Spearman relativity analysis,visual classification of rigid laryngoscope was significantly related with intubation time,P<0.01.Conclusions Older age and small mandible can predict the longer intubation time with visual rigid laryngoscopes by midline approaching through the mouth.Incisors protrusion can predict shorter intubation time.There was no certain value with other traditional bedside assessment methods by midline approaching through the mouth.In addition,visual classification of rigid laryngoscope and intubation time has a significant correlation,which can be considered as an index of the difficulty degree of intubation.