Diagnostic value of impulse oscillometry system in patients with asthma-chronic obstructive pulmonary disease

Objective To evaluate the diagnostic value of impulse oscillometry system (IOS) pulmonary function test-related indicators for the diagnosis of asthma-chronic obstructive pulmonary disease overlap (ACO) and to obtain the cut-off values of relevant parameters. Methods A total of 56 patients were enrolled, including 46 patients with chronic obstructive pulmonary disease (COPD) and 10 patients with ACO.General spirometry and IOS were performed before and after bronchodilation. 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%pred) and the impedance difference at 5 Hz and 20 Hz (R5-R20) is higher.The optimal threshold values are 117.33% and 0.27, respectively, and the sensitivity is 0.80 and 0.70, the specificity is 0.74 and 0.72 respectively.After the bronchodilation test, the threshold value, sensitivity, and specificity of R20%pred-post were 102.78%, 0.80, and 0.70, respectively.From the changes before and after the bronchialdilation test, when Δ(R5-R20)>0.06 and the area under the reactance ΔAX>0.98, satisfactory composite sensitivity (0.80 and 0.90, respectively) and specificity (0.78 and 0.72, respectively) were obtained.In addition, the variables of inspiratory phase impedance and reactance at 5 Hz before and after the bronchial dilation test, ΔR5in>0.12, ΔX5in>0.06 are the breakpoints, with moderate diagnostic value. Conclusions 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. Key words: Chronic obstructive pulmonary disease; Asthma-COPD overlap; Impulse oscillometry system