Abstract
Background: Exercise intolerance is the hallmark of COPD and FEV1 is the traditional method used to define the severity of COPD. However there is a dissociation between FEV1 and exercise capacity in a large proportion of subjects with COPD. Therefore it is of interest to investigate if other lung function parameters are having an additive, predictive value of exercise capacity (EC) and if this differs according to the COPD stages.
Methods: Spirometry, measurements of lung volumes and diffusing capacity for carbon monoxide (DLCO) were performed in 88 patients with COPD GOLD stages II-IV. EC was determined by symptom-limited incremental cycle ergometer test.
Results: DLCO, FEV1 and inspiratory capacity (IC) were found to be the best predictors of EC in a stepwise regression analysis and explain 72% of EC. These lung function parameters explained 71% of EC in GOLD II, 69% in GOLD III and 32% in GOLD IV. DLCO alone was the best predictor of exercise capacity in GOLD II and IV (Table).
Discussion: Additive information regarding COPD patients' exercise capacity is obtained by measuring diffusing capacity and inspiratory capacity. DLCO was the strongest predictor of exercise capacity in all subjects and the best individual predictor in patients with GOLD stage II. This suggests that clinically monitoring with measurements of diffusing capacity may be beneficial even in patients with moderate disease severity.
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