Rationale: Bronchodilator therapy represents a potentially valuable therapeutic option to increase exercise tolerance and enhance lung function in mild to moderate chronic obstructive pulmonary disease (COPD).
Objectives: To determine effects of tiotropium on pulmonary hyperinflation and exercise tolerance in patients with symptomatic Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 and 2 COPD who experienced inspiratory capacity decrease greater than or equal to 100 ml during incremental and constant work rate treadmill exercise.
Methods: This 22-week, randomized, double-blind, two-period crossover study evaluated the efficacy of once-daily tiotropium bromide (18 μg) versus placebo in patients with GOLD 1 and 2 COPD. Primary endpoint was between-group (tiotropium vs. placebo) difference in inspiratory capacity at isotime (i.e., at the time the shortest test ended) during constant work rate treadmill exercise from baseline to the end of a 6-week treatment period. Key secondary endpoints included differences in exercise duration and exertional dyspnea. Safety was assessed by recording adverse events.
Measurements and main results: Study population comprised 48 patients with GOLD 1 COPD and 78 patients with GOLD 2 COPD. Resting inspiratory capacity significantly improved with tiotropium versus placebo in the overall (P < 0.0001), GOLD 1 (P = 0.0183), and GOLD 2 (P < 0.0001) groups. Isotime inspiratory capacity was significantly enhanced during exercise in the overall (P = 0.0087) and GOLD 2 (P = 0.0494) groups after tiotropium versus placebo. Tiotropium versus placebo significantly enhanced exercise duration in the GOLD 2 group (P = 0.0070) but not in the GOLD 1 or overall patient groups. In the overall group, increase in exercise duration seen with tiotropium was well correlated with the increase in isotime inspiratory capacity (r = 0.463, P < 0.0001).
Conclusions: Resting and exercise hyperinflation were ameliorated by bronchodilator therapy with tiotropium in the overall GOLD 1 plus 2 COPD group. Exercise tolerance was enhanced in GOLD 2, but not GOLD 1, COPD. Clinical trial registered with www.clinicaltrials.gov (NCT01072396).
Keywords: Global Initiative for Chronic Obstructive Lung Disease; chronic obstructive pulmonary disease; dynamic hyperinflation; dyspnea; inspiratory capacity.