Both breathing discomfort and leg discomfort contribute to perceived symptom limitation in many COPD patients during incremental cycle ergometry (IE); perceived symptom limitation during constant work rate cycle ergometry (CWRE) has not been evaluated. In a double-blind, placebo-controlled study evaluating the effects of tiotropium on exercise tolerance in patients with COPD, we compared perceived symptom limitation during IE and CWRE, and evaluated the effects of tiotropium on perceived symptom limitation during CWRE.
248 COPD patients performed IE and CWRE at screening, and CWRE after 6 weeks of treatment. Patients rated breathing discomfort and leg discomfort (Borg scale) at the point of symptom limitation and reported the perceived symptom limitation using a simple questionnaire (Hamilton et al CHEST 1996;110:1255).
The tableScreeningDay 42 CWREIECWRETiotropiumPlaceboNumber of patients248248131117BD50.8%40.3%27.5%*41.9%BD / LD33.1%43.5%41.2%38.5%LD16.1%14.5%29.8%*18.0%None0%1.6%1.5%1.7%*
p<0.01 vs. placebo, Chi-square testbelow shows the percentage of patients who perceived symptom limitation as breathing discomfort alone (BD), a combination of breathing and leg discomfort (BD / LD), leg discomfort alone (LD), neither breathing nor leg discomfort (None). There was a significant shift in perceived symptom limitation following treatment with tiotropium, with a reduction in the proportion of patients with BD alone as the perceived symptom limitation and an increase in the proportion of patients with LD alone as the perceived symptom limitation (p<0.01). At the point of symptom limitation, breathing discomfort was greater than leg discomfort at baseline (adjusted mean: 7 vs. 6.3 Borg units) and with placebo (7 vs. 6.5 Borg units), but breathing discomfort was less than leg discomfort with tiotropium (6.3 vs. 6.5 Borg units).
As a result of tiotropium-induced reductions in exertional dyspnea, patients are more likely to report that leg discomfort contributes to symptom limitation during exercise.
In the assessment of disability in patients with COPD, consideration should be given to the relative role of breathing discomfort and leg discomfort to symptom limitation.
D.E. O’Donnell, Boehringer Ingelheim and Pfizer