Comparison of Oscillometry with Lung Function Parameters between Bronchial Asthma with Airflow Obstruction and COPD Patients

BackgroundLung oscillometry is an emerging lung function test for assessing obstructive airway disease. Comparisons of oscillometry parameters and their bronchodilator responsiveness (BDR) between bronchial asthma and chronic obstructive pulmonary disease (COPD) patients are limited. Research QuestionDo oscillometry parameters and their BDR differ between stable asthma and COPD patients with similar severity of airflow obstruction? Study Design and MethodsWe included 467 consecutive adult patients with a clinical history of asthma (n=187) or COPD (n=280). Oscillometry, spirometry, and body plethysmography were performed before and after inhaling 400 g of salbutamol. Patients were stratified based on the severity of airflow obstruction in spirometry. The z scores of the oscillometry parameters were used for the comparison. The BDR of oscillometry parameters with other lung function parameters was also compared. ResultsThe average age of the study population was 54.9 years, and 76.4% were male. COPD patients were older, had a greater number of smokers, and had poorer lung function. The magnitude of oscillometry parameters worsened with increasing severity of airflow obstruction, regardless of the underlying disease. Asthma patients, particularly those with moderate and severe airway obstruction, had significantly higher R5 and R19 than COPD patients. The within- and whole-breath X5 of asthma were not different from those of COPD patients with similar severities of airflow obstruction. Expiratory flow limitation at tidal breaths ({Delta}X5 > 0.28 kPa/L/s) was observed in both asthma and COPD patients across all severities of airflow obstruction. The proportion of BDR in oscillometry was significantly lower than that in spirometry for both asthma (35.3% vs. 57.1%; p<0.01) and COPD patients (19.3% vs. 47.1%; p=0.02). InterpretationOscillometry parameters except for R5 and R19 did not differ between asthma and COPD patients with similar severities of airflow obstruction. Similar to spirometry, COPD patients had lower BDR in oscillometry than asthma patients. Take-home PointsO_ST_ABSStudy QuestionC_ST_ABSAre oscillometry parameters and their bronchodilator responsiveness different between bronchial asthma and COPD patients with similar severities of airflow obstruction? ResultsWe compared the FOT between 187 bronchial asthma and 280 COPD patients. Except for R5 and R19, the severity and distribution of high oscillometry parameters did not differ between asthma and COPD patients. InterpretationThe severity of oscillometry abnormalities is primarily determined by the severity of airflow obstruction, not the underlying disease.