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 VO2:dyspnea and V-E:dyspnea regressions were significanty lower, and patients exercised longer (Delta = 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 oil the 0-10 category-ratio scale; P = 0.02) and patients exercised longer (Delta = 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.