LAMA improves tissue oxygenation more than LABA in patients with COPD.

The effect of bronchodilators is mainly assessed with forced expiratory volume in 1 s (FEV 1 ) in chronic obstructive pulmonary disease (COPD). Their impact on oxygenation and lung periphery is less known. Our objective was to compare the action of long-acting β 2 -agonists (LABA-olodaterol) and muscarinic antagonists (LAMA-tiotropium) on tissue oxygenation in COPD, considering their impact on proximal and peripheral ventilation as well as lung perfusion. FEV 1 , Helium slope (S He ) from a single-breath washout test (S He decreases reflecting a peripheral ventilation improvement), frequency dependence of resistance (R5-R19), area under reactance (AX), lung capillary blood volume (Vc) from double diffusion (DL NO /DL CO ), and transcutaneous oxygenation (TcO 2 ) were measured before and 2 h post-LABA ( day 1 ) and LAMA ( day 3 ) in 30 patients with COPD (FEV 1 54 ± 18% pred; GOLD A 31%/B 48%/E 21%) after 5-7 days of washout, respectively. We found that TcO 2 increased more ( P = 0.03) after LAMA (11 ± 12% from baseline, P < 001) compared with LABA (4 ± 11%, P = 0.06) despite a lower FEV 1 increase ( P = 0.03) and similar S He ( P = 0.98), AX ( P = 0.63), and R5-R19 decreases ( P = 0.37). TcO 2 and S He changes were negatively correlated ( r = -0.47, P = 0.01) after LABA, not after LAMA ( r = 0.10, P = 0.65). DL NO /DL CO decreased and Vc increased after LAMA ( P = 0.04; P = 0.01, respectively) but not after LABA ( P = 0.53; P = 0.24). In conclusion, LAMA significantly improved tissue oxygenation in patients with COPD, while only a trend was observed with LABA. The mechanisms involved may differ between both drugs: LABA increased peripheral ventilation, whereas LAMA increased lung capillary blood volume. Should oxygenation differences persist over time, LAMA could arguably become the first therapeutic choice in COPD. NEW & NOTEWORTHY Long-acting muscarinic antagonists (LAMAs) significantly improved tissue oxygenation in patients with COPD, while only a trend was observed with β 2 -agonists (LABAs). The mechanisms involved may differ between drugs: increased peripheral ventilation for LABA and likely lung capillary blood volume for LAMA. This could argue for LAMA as the first therapeutic choice in COPD.