Measurement of Symptoms, Lung Hyperinflation, and Endurance during Exercise in Chronic Obstructive Pulmonary Disease

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Abstract

Changes in lung hyperinflation, dyspnea, and exercise endurance are important outcomes in assessing therapeutic responses in chronic obstructive pulmonary disease (COPD). Therefore, we studied the reproducibility of Borg dyspnea ratings, inspiratory capacity (IC; to monitor lung hyperinflation), and endurance time during constant-load symptom-limited cycle exercise in 29 patients with COPD (FEV1 = 40 ± 2% predicted; mean ± SEM). Responsiveness was also studied by determining the acute effects of nebulized 500 μg ipratropium bromide (IB) or saline placebo (P) on these measurements. During each of four visits conducted over an 8-wk period, spirometry and exercise testing were performed before and 1 h after receiving IB or P (randomized, double-blinded). Highly reproducible measurements included: endurance time (intraclass correlation R = 0.77, p < 0.0001); Borg ratings and IC at rest, at a standardized exercise time (STD), and at peak exercise (R > 0.6, p < 0.0001); and slopes of Borg ratings over time, oxygen consumption (V̇ o2), and ventilation (R > 0.6, p < 0.0001). Responsiveness was confirmed by finding a significant drug effect for: change (Δ) in endurance time (p = 0.0001); Δ BorgSTD and Δ Borg-time slopes (p < 0.05); and Δ IC at rest, at STD, and at peak exercise (p = 0.0001). With all completed visits, Δ BorgSTD correlated better with Δ ICSTD than any other resting or exercise parameter (n = 115, r = - 0.35, p < 0.001). We concluded that Borg dyspnea ratings, and measurements of IC and endurance time during submaximal cycle exercise testing are highly reproducible and responsive to change in severe COPD.

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