There is considerable evidence that oxidative stress is increased in patients with COPD, although little information is available about its relation with the structural and functional alterations produced by COPD. We evaluate the relationship between 8-isoprostane in exhaled breath condensate (EBC) of stable COPD patients and the main parameters of the disease such as dyspnoea, stages of severity, lung parenchyma densities, lung function impairment and exercise tolerance in order to identify the predictors of airway oxidative stress.
METHODS: In a cross-sectional study, we included 76 males with moderate to very severe COPD. 8-isoprostane levels in EBC were measured by EIA. Regional lung densities were measured by lung densitometry with high resolution computed tomography. Arterial blood gases, lung volumes and diffusing capacity were determined. Patients performed a six-minute walk test and an incremental exercise test with measurement of breathing pattern and operating lung volumes.
RESULTS: Significant severity-related differences in 8-isoprostane were identified according to BODE index. 8-isoprostane levels were related to smoking intensity, lung densities in expiration, static lung volumes, PaO(2), diffusion capacity, distance walked in six minutes, peak oxygen uptake and anaerobic threshold. Concentration of 8-isoprostane was higher in the 60 patients (79%) who developed dynamic hyperinflation than in the remaining 16 who did not (21%). In a multivariate linear regression analysis using 8-isoprostane as a dependent variable, end-expiratory lung volume change and PaO(2) were retained in the prediction model (r(2)=0.734;p<0.001).
CONCLUSION: In stable COPD patients, oxygen level and dynamic hyperinflation are related to airway oxidative stress.
Authors: García-Rio F, Romero D, Lores V, Casitas R, Hernanz A, Galera R, Alvarez-Sala R, Torres I
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