Addition of tiotropium to formoterol improves inspiratory muscle strength after exercise in COPD

SummaryBackgroundThe addition of tiotropium bromide (TIO) to formoterol fumarate (FOR) improves exercise performance in patients with chronic obstructive pulmonary disease (COPD). In this study, we test the hypothesis that the addition of TIO to FOR may improve respiratory muscle performance and oxygen uptake kinetics after exercise in patients with COPD.MethodsThirty eight patients with COPD were randomized to a 2 week treatment with FOR 12 μg twice a day plus TIO 18 μg once a day (FOR + TIO) or FOR 12 μg twice a day plus placebo (FOR + PLA) once a day, using a double-blind crossover design. Inspiratory muscle. Strength was measured before, immediately after, as well as 2, 5, and 10 min during recovery of exercise. Time to limit of tolerance on a constant work load exercise test and oxygen uptake kinetics during recovery were evaluated before and after intervention.ResultsOnly FOR + TIO improved resting (63 ± 10 cm to 84 ± 11 cmH2O) and post-exercise (49 ± 7 cm to 84 ± 11 cmH2O) maximal inspiratory pressure. Time to limit of tolerance on the constant work load test was increased by FOR + PLA and by FOR + TIO, but the size of the increment was significantly larger with FOR + TIO (40.7 ± 7.6% vs. 84.5 ± 8.2%; p < 0.05). Only FOR + TIO improved oxygen uptake kinetics during recovery (69 ± 21 to 60 ± 18 s). The improvement in maximal inspiratory pressure (0.78, p < 0.001) and in oxygen uptake kinetics (−0.91, p < 0.001) correlated with the change in time to the limit of tolerance.ConclusionsThe addition of TIO to FOR improves inspiratory muscle strength and oxygen uptake kinetics after exercise in COPD patients.