Diagnostic Value Of Impulse Oscillometry System In Patients With Asthma-chronic Obstructive Pulmonary Disease

0bjective: Chronic obstructive pulmonary disease(COPD)and asthma are common chronic airway diseases,but they have different pathogenesis.Some patients with COPD may have airway reversibility,while some patients with asthma present with limited airflow limitation.Therefore,relying solely on the reversible and/or fixed degree of airflow,a clear differential diagnosis of chronic obstructive pulmonary disease or asthma cannot be made.This is also the difficulty in the diagnosis of patients with asthma-Chronic obstructive pulmonary disease overlap(ACO).Impulse Oscillation Pulmonary Function Test(IOS)is a method for assessing airway resistance and compliance through impulse oscillating techniques.It can simultaneously detect airway and small airway resistance,and can also judge airway and lung tissue compliance.These technical features make it possible for IOS to take into account the pathophysiological features of COPD and asthma,so as to obtain IOS test data with ACO characteristics.The aim of this study was to evaluate the diagnostic value of Impulse oscillometry system pulmonary function test(IOS)-related indicators for the diagnosis of asthma-chronic obstructive pulmonary disease overlap(ACO)and to obtain the cut-off values of relevant parameters.Methods:The study subjects were patients with chronic obstructive pulmonary disease or ACO who were diagnosed during the outpatient or hospital stay in our hospital from November 2015 to August 2018.A total of 56 patients were enrolled in the study.There were 46 patients with chronic obstructive pulmonary disease and 10 patients with ACO.Conventional spirometry,bronchodilation,and IOS before and after bronchodilation were performed according to the guidelines of the European Society of Respiratory Diseases.The gender,age,height,weight,smoking index,lung function index,and IOS index of all subjects were recorded.Data analysis was performed using SPSS 13.0 statistical software.If the measurement data conformed to the normal distribution,it was represented by X±S,and the t-test of two independent samples was used for comparison between groups.Non-normal measurement data were expressed as median and interquartile range M(QR),and Mann-Whitney U test was used for comparison between groups.P < 0.05 showed statistically significant differences.The corresponding sensitivity and specificity are obtained according to different IOS values,and the ROC curve is plotted with the 1-specificity as the abscissa and the sensitivity as the ordinate.Results:The ROC curve shows that,at the baseline state,the area under the curve(AUC)of the predicted value of the impedance at 20 Hz,(R20%pre)and the impedance difference at 5 Hz and 20 Hz(R5-R20)pre is higher.The optimal threshold values are 117.33% and 0.27,respectively,and the sensitivity is 0.8 and 0.7,the specificity is 0.74.And 0.72 respectively.After the bronchodilation test,the threshold value,sensitivity,and specificity of R20%post were 102.78%,0.8,and 0.7,respectively.From the changes before and after the bronchialdilation test,when ?(R5-R20)> 0.06 and the area under the reactance ? AX >0.98,satisfactory composite sensitivity(0.8 and 0.9,respectively)and specificity(0.78 and 0.72,respectively)were obtained.0.9).In addition,the variables of inspiratory phase impedance and reactance at 5 Hz before and after the bronchial dilation test,? R5 in >0.12,? X5 in >0.06 are the breakpoints,with moderate diagnostic value.Conclusion:As an auxiliary examination method of ACO,IOS has certain clinical application value,which is helpful for the differentiation of ACO patients and patients with simple COPD.At baseline,R20% pre>117.33%,(R5-R20)pre > 0.27 as a breakpoint,AUC were 0.77 and 0.74,respectively,with moderate diagnostic value;after bronchodilation test,R20% post>102.78 % as a breakpoint,AUC It has a moderate diagnostic value of 0.72.From the changes before and after the bronchial dilation test,?(R5-R20)> 0.06,? AX >0.98,? R5 in >0.12,? X5 in >0.06 are used as the breakpoint,and the AUC are 0.77,0.80,0.83,0.86,with moderate diagnostic value.