Logistic Regression Analysis Of Difficult Airway Risk Factors And Establishment Of New Airway Prediction System Based On Arne

Objective The object of this study was to determine the clinical risk factors of difficult laryngoscopy and difficult mask ventilation.Methods Three hundred patients receiving general anaesthesia with tracheal intubation were involved, their airway characteristics such as height, thyromental and sternomental distance(TMD), range of neck movement, inter-incisor distance, and modified Mallampati class were determined.Intubation Difficult Score was used to identify difficult laryngoscopy.Both difficult laryngoscopy and difficult mask ventilation were treated as difficult airway.Association between airway characteristics and difficult airway were analysed by logistic regression analysis.The cut-off values for ratio of height and TMD was found by ROC curve.Results Eight airway characteristics related to difficult airway were ratio of height and TMD3.58(1.95～8.46), modified Mallampati class3.34(1.82～7.14),BMI3.07(1.64～6.69),history of difficult airway2.79(1.28～5.25),thick neck2.15(1.04～4.37), range of neck movementl.98(0.96～3.89), sternomental and angulus mandibulae distance1.46 (0.67 ～ 3.04), and inter-incisor distance1.01(0.49～2.54). Cut-off values for ratio of height and TMD was 22.8.Conclusion The airway characteristics related to difficult airway were ratio of height and TMD, modified Mallampati class, BMI, history of difficult airway, thick neck, range of neck movement, sternomental and angulus mandibulae distance, and inter-incisor distance. The cut-off values for ratio of height and TMD differed in ethnic groups., in our study it was 22.8.Objective A new system based on Arne system was set up for predicting difficult laryngoscopy.Methods 113 patients who suffered from difficult laryngoscopy consisted the case group. According to principles of the same sex,similar age,113 patients with easy laryngoscopy were paired with the case group Airway characteristics such as knowledge by the patient of previous difficult laryngoscopy,pathologies associated with difficult laryngoscopy,clinical symptoms of airway pathology,height,thyromental distance(TMD),maximum range of the head and neck movement,inter-incisor gap and mandible luxation were recorded. Logistic regression analysis was applied to find a new system. Arne system and new system was applied respectively.Results (1) Risk factors of difficult laryngoscopy were clinical symptoms of airway pathology, Mallampati test,ratio of height and TMD, knowledge of difficult laryngoscopy and inter-incisor gap.The odd radios were (19.57,1.28～94.33), (15.39,1.14～87.74), (11.62,1.06～ 75.41), (5.45,0.97～46.23), (2.78,0.91 ～12.50). (2) The new system got the sensitivity,specificity,positive predictive value and the negative predictive value of 85.8,70.8,74.6 and 83.3 respectively. Arne system got the sensitivity,specificity,positive predictive value and the negative predictive value of 77.0,78.8,78.4,59.3 respectively.Conclusion The new system got the sensitivity,specificity,positive predictive value and the negative predictive value of 85.8,70.8,74.6 and 83.3 respectively, could predict difficult airway appropriately.