Study objectives: We have previously shown that tiotropium at 18 mug reduces lung hyperinflation and dyspnea during exercise and improves exercise tolerance in patients with COPD. The present study was designed to gain further insight into the duration of improvements.
Design, patients, and interventions: A randomized, double-blind, placebo-controlled, parallel-group study was conducted in 261 COPD patients (mean age, 62.5 +/- 7.4 years [+/- SD]; 189 men and 72 women; mean FEV1, 1.2 +/- 0.4 L [43 +/- 12.7% predicted]). On day 0 (first dose), day 21, and day 42 of treatment, pulmonary function tests were performed before and 1 h 20 min after dosing, followed by a constant work rate cycle ergometry test (75% maximum work capacity) to symptom limitation at 2.25 h after dosing. On day 42, an additional constant work rate cycle ergometry test was performed at 8 h after dosing.
Results: Adjusted mean (+/- SE) endurance time (ET) on day 42 was 803 +/- 40 s (tiotropium), vs 568 +/- 42 s (placebo) at 2.25 h after dosing (primary end point; treatment difference, 236 +/- 58 s; p = 0.0001) and 665 +/- 40 s (tiotropium) vs 494 +/- 42 s (placebo) at 8 h after dosing (treatment difference, 171 +/- 58 s; p = 0.0035). Adjusted mean dyspnea intensity at isotime on day 42 was 4.60 +/- 0.16 Borg units (tiotropium), vs 5.65 +/- 0.16 Borg units (placebo) at 2.25 h after dosing (p < 0.001), and 5.54 +/- 0.17 Borg units (tiotropium) vs 6.51 +/- 0.18 Borg units (placebo) at 8 h after dosing (p < 0.001). Adjusted mean pre-exercise inspiratory capacity (IC) on day 42 was 2.41 +/- 0.03 L (tiotropium) vs 2.19 +/- 0.03 L (placebo) at 2.25 h after dosing (p < 0.001), and 2.31 +/- 0.03 L (tiotropium) vs 2.16 +/- 0.03 L (placebo) at 8 h after dosing (p < 0.001). The significant increase in IC with tiotropium compared with placebo was maintained throughout exercise.
Conclusions: The present study confirms that tiotropium reduces lung hyperinflation at rest and during exercise, reduces exertional dyspnea, and improves symptom-limited exercise tolerance in COPD patients. Furthermore, this study shows that this improvement is present at 2.25 h and at 8 h after dosing after 6 weeks of treatment.