Bronchodilator response (BDR)
One measurement according to the aforementioned criteria 15 min after administration of 400 μg of salbutamol via a metered-dose inhaler with spacer was selected for both IOS and spirometry. The spirometric BDR was defined as positive when change of forced expiratory volume in one second (FEV1) was ≥12% and/or ≥ 200 mL.