Test-retest reliability of symptom-limited cycle ergometer tests in patients with chronic obstructive pulmonary disease

Background: Symptom-limited exercise tests are widely used to evaluate the effects of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD), but the reliability of these tests is not well established in COPD patients. Objectives: We compared test-retest reliability of two repeated symptom-limited exercise tests between COPD patients and healthy elderly subjects and between male and female patients. Method: Fifty-six COPD patients (40 men, 16 women) and 16 healthy subjects (6 men, 10 women) performed two symptom-limited exercise tests approximately 2 weeks apart. Measures of oxygen uptake ((V) over dot O-2), minute ventilation ((V) over dot E), heart rate, and ratings of breathlessness and leg fatigue were obtained at peak exercise at each symptom-limited exercise test. Results: Repeated measures of peak exercise responses were stable for patients and healthy subjects and for male and female patients. Although mean percent error (absolute difference divided by mean) for peak exercise responses was low, some individuals' values exceeded 10%. There was no difference in the percent error between CORD patients and healthy subjects or between men and women with COPD. Test-retest reliability was lower for breathlessness ratings than for other peak exercise responses for all groups. Conclusions: Repeated symptom-limited exercise tests are reliable in COPD patients and healthy subjects. However, some individuals are less reliable, and these patients may require more than one exercise test to establish reliable performance.