Slopes of He (SHe) and SF6 (SSF6) from single-breath washout test (SBWO) (assessing ventilation heterogeneities at the level of pre- and intra-acinar bronchioles, respectively) (quadruple model, LR6000 Logan-Sinclair, Rochester, UK), respiratory system resistance (R5, R5-R19) and reactance (X5, AX, Fres) from forced oscillation test (FOT) (Resmon Pro, ResTech, Italy), lung capillary volume (Vc) from double diffusion of NO and CO (DLNO/DLCO) (Hyp'Air compact, Medisoft, Dinant, Belgium), and FEV1 from spirometry (Zan®, Oberthulba, Germany) were evaluated before and after LABD administered via a spacer device: during the first visit, before, 30 minutes and 2 hours after inhalation of 4 puffs of 2,5 µg of olodaterol (LABA); during the second visit, before, 40 minutes and 2 hours after the administration of 4 puffs of 2,5 µg of tiotropium (LAMA). Transcutaneous oximetry (Perimed232©, Järfälla, Sweden) was monitored continuously during the 2 hours of each visit.
