Abstract
Aim: Physiologic and biologic determinants of exercise tolerance in COPD have not been extensively studied.
Methods: We examined 45 COPD patients (36 male, age 69.9±7.1 yrs, pack-yrs 50.8±28.2, FEV1 52.5±17.0 %pred) attending to a pulmonary rehabilitation program. All of them underwent a detailed functional (including static lung function, diffusing capacity, MIP, MEP) and biologic (blood and sputum inflammatory cells, blood haemoglobin, CRP and pro-BNP) evaluation. Exercise capacity was assessed by incremental CPET on cycloergometer (VO2peak/kg: 17.5±5.5 ml/min/kg) and by incremental SWT (284.4±128.0 m) (dependent variables). Several independent variables were considered for predicting VO2peak/kg or SWT. Multivariate analysis was performed including all independent variables which were significantly correlated to the dependent variables.
Results: FEV1, IC, DLco, blood hemoglobin and pro-BNP were all significantly correlatd with VO2peak/kg and SWT, but age and MIP/MEP significantly correlated only with SWT. In a logistic regression analysis, blood hemoglobin tended to be significantly correlated with VO2peak/kg (p=0.08, r2: 0.23), while hemoblobin, MIP and age significantly correlated with SWT (p<0.001 for each variables, cumulative r2: 0.63).
Conclusion: The difference in the main determinants of CPET and SWT suggests that these two tests for assessing exercise capacity are exploring different physiologic and biologic features of COPD.
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