Responsiveness of continuous ratings of dyspnea during exercise in patients with COPD

Purpose: To examine the responsiveness of a new computerized method for patients to provide continuous ratings of dyspnea during exercise in patients with chronic obstructive pulmonary disease (COPD). Methods: In this randomized, double-blind study the effects of an inhaled bronchodilator (BD), albuterol/ipratropium bromide solution, were compared with normal saline (NS) in 30 patients with COPD (age, 66 ± 9 yr; forced expiratory volume in 1 s, 48 ± 14% pred). At visit 1, patients were familiarized with the cycle ergometer and computer, monitor, and mouse system to provide continuous ratings of dyspnea during exercise. At subsequent visits 2-3 d apart, patients performed pulmonary function tests followed by incremental ramp (15 W·min ^-1) and, 1 h later, constant work (at 55% of maximal work capacity) exercise tests. Results: During incremental exercise the slopes of V̇O ₂:dyspnea and V̇_E:dyspnea regressions were significantly lower, and patients exercised longer (Δ = 0.4 min; P = 0.003) with BD therapy compared with NS. During constant work exercise there was a significant reduction in dyspnea at the same exercise duration (5.0 ± 2.8 vs 6.2 ± 2.8 units on the 0-10 category-ratio scale; P = 0.02) and patients exercised longer (Δ = 0.9 min; P = 0.04) with BD therapy. Changes in lung function at rest did not correlate significantly with changes in dyspnea ratings during exercise. Conclusions: Continuous ratings of dyspnea were responsive to inhaled bronchodilator therapy during both incremental and constant work exercise tests in patients with symptomatic COPD.