Impulse oscillation system versus spirometry in assessment of obstructive airway diseases

Abstract

Background Impulse oscillation system (IOS) is a simple, effort-independent modality for the evaluation of airway resistance and reactance. It can be used for the assessment of obstructive airway diseases in adults and children. The aim of this study was to compare IOS and spirometry in the evaluation of airway obstruction in both asthmatic and chronic obstructive pulmonary disease (COPD) patients. Patients and methods A total of 70 participants were included in this study and were classified into three groups, the asthma group (25 patients), the COPD group (25 patients), and the control group (25 healthy participants), full history, clinical examination, and demographic data were obtained from all participants, spirometry was done, and the following values were obtained: forced expiratory volume in 1 s (FEV1%), forced vital capacity (FVC%), FEV1/FVC, midexpiratory flow rate (MEF)25–75%, and MEF75–85%, IOS measured values were R20%, R5%, and X5. Results Females represent about 64% of the asthma group, whereas males represent the 100% COPD group. COPD patients were older than both the asthma and control groups with the mean age of 56.8±9.31, whereas asthmatic patients were more obese than both the COPD and control groups with mean BMI of 29.27±6.03. There was a statistically significant decrease in all spirometry values and increase in central, peripheral airways resistance, and a decrease in reactance (to more negative values) in asthmatic and COPD patients in comparison with that of the control group. In the asthma group, we noticed a statistically significant negative correlation between R5% and FEV1/FVC, FEV1%, MEF75%, and MEF75–85%, whereas a positive correlation was found between these spirometry parameters and X5. In the COPD group, we found a statistically significant negative correlation between R20% and FEV1/FVC only, and a negative correlation between R5% and FEV1/FVC, FVC, FEV1%, MEF75%, and MEF75–85% with a statistically significant P value, and a positive correlation was found between these spirometry parameters and X5. Sensitivity of IOS in detection of small airway obstruction in the asthma group was 100%, specificity 83.33% with diagnostic accuracy of 96%, whereas in the COPD group, sensitivity was 83.33%, specificity 100%, and diagnostic accuracy 84%. Conclusion The severity of airway obstruction by IOS was well correlated to spirometry in both asthma and COPD. IOS was more sensitive in detection of small airway obstruction and less sensitive for large- airway obstruction than spirometry in asthmatics and COPD patients.