EVALUATION OF SMALL AIRWAY REVERSIBILITY AMONG ASTHMATIC PATIENTS WITH NON-OBSTRUCTIVE PATTERNS OF SPIROMETRY

Background: Although the forced expiratory flow parameters are increasingly used in the diagnosis of small airway disease (SAD), the reversibility of these indicators is rarely described. The aim of this study is to evaluate the association of small airways reversibility with the presence of SAD and bronchodilator reversibility (BDR) of the proximal airways.Methods: The forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and the indicators of SAD (FEF25%, FEF50%, FEF75%, FEF25-75%, and FEF75-85%) were measured before and 20 minutes after salbutamol administration (200 mcg by using inhaler/Spacer). Positive BDR was accepted when FEV1 or FVC was increased ? 12% and > 200 ml, indicating responsive proximal airways. Positive small airway reversibility was diagnosed when any of the small airway indicators is increased ? 30% above the baseline results. All measurements were performed with the All-flow spirometer (Clement Clarke International, Harlow, UK).Results: Evidence of SAD was found in 62.1% of all participants and in 75.2% of those who showed responsive proximal airways. The positive predictive value of the SAD in diagnosing responsive proximal airways was 67.8%. The reversibility of the small airway indicators showed insignificant association with the FEV1 or FVC BDR. The reversibility of FEF50%, FEF75% and FEF25-75% showed significant association with the diagnosis of SAD, with specificities ranging from 75.5%-81.1%.Conclusion: SAD has a significant association with positive reversibility of both the proximal and the peripheral airways. Further studies are needed to evaluate the clinical significance of positive small airway reversibility in the diagnosis and management of obstructive lung diseases.Keywords: Asthma; Small airway disease; Bronchodilator Reversibility, FEV1, FVC; FEF25-75%