Impulse oscillometry to differentiate between chronic obstructive pulmonary disease and bronchial asthma

Abstract

BackgroundThe impulse oscillation system (IOS) yields useful clinical data that predominantly include functional assessment of peripheral airways more than that available from commonly used spirometry. The aim of this study was to differentiate between chronic obstructive pulmonary disease (COPD) and bronchial asthma using IOS.Patients and methodsThis study was carried out on 40 patients; 20 patients were diagnosed with bronchial asthma and the remaining 20 patients had a clinical diagnosis of COPD. All patients underwent baseline IOS and spirometry, and then after 15 min of inhalation of 400 μg salbutamol, spirometry was repeated in all patients.ResultsA highly statistically significant difference was found between asthma patients and COPD patients in R20, whereas no statistically significant difference was found between the two studied groups in R5, X5. There was a statistically significant difference between asthma patients and COPD patients in resistance; 75% of asthmatic patients had increased total airway resistance, mainly proximal, 20% had increased total airway resistance, mainly peripheral, and 5% had normal airway resistance, whereas all COPD patients had increased total airway resistance, mainly peripheral. No significant correlation was found between IOS parameters and spirometric parameters in COPD or asthmatic patients, but in both groups, there was a significant correlation between forced expiratory volume 1 (FEV1) and R5, X5.ConclusionIOS provides useful clinical information that prominently includes functional assessment of small, peripheral airway behavior beyond that available from commonly used pulmonary function tests. IOS also aids differentiation between COPD and bronchial asthma. COPD patients had increased airway resistance, mainly in the peripheral airways, whereas asthmatic patients had increased airway resistance, mainly in the proximal airways. R20 is the best IOS parameter to differentiate between these two diseases.