Study objective: Inhaled bronchodilators are the first-line pharmacotherapy against COPD. The purpose of the present study was to investigate the effects of β2-agonists and anticholinergic agents on the exercise capacity of patients with COPD.
Methods: A total of 67 stable patients with COPD were recruited at the Kyoto University Hospital. After inhaling 400 μg salbutamol, 80 μg ipratropium bromide, or an identical placebo in a randomized, double-blind, crossover fashion, the patients performed cycle endurance tests at a constant workload of 80% of the maximum work rate reached on progressive cycle ergometry, and the endurance time was recorded.
Results: Both salbutamol and ipratropium bromide significantly improved the endurance time by 29 s (15%; p < 0.001) and 27 s (14%; p < 0.001), respectively, in comparison with the placebo. However, there was no statistically significant difference between them (p = 0.71). The dyspnea ratios were also similarly reduced by both bronchodilators. The difference in the endurance time between therapy with salbutamol and placebo was significantly, but moderately, related to the difference between therapy with ipratropium bromide and placebo. In addition, there were no relationships, or only weakly significant relationships, between the change in FEV1 and the change in the endurance time, the highest oxygen uptake, and the highest minute ventilation for both salbutamol and ipratropium bromide.
Conclusions: Therapy with both salbutamol and ipratropium bromide improved exercise capacity, as evaluated by the endurance time, and reduced dyspnea similarly in patients with COPD. In addition, the effects of the different bronchodilators on exercise capacity varied within individuals, and a complex mechanism may be responsible for the different effects of these two bronchodilators on exercise capacity vs airflow limitation. These results support the conclusion that both types of inhaled bronchodilators can be used as first-line drugs for the treatment of stable patients with COPD.