It may be an important amplifying mechanism for COPD .Biomarkers of oxidative stress (hydrogen peroxide ,8-isoprostane ) are increased in the exhaled breath condensate ,sputum and systemic circulation of COPD patients .Oxidative stress is further increased in exacerbations .Oxidants are generated by cigarette smoke and released from activated inflammatory cells such as macrophages and neutrophils .There also might be a reduction in the endogenous antioxidants in COPD patients because of the reduction in transcription factor Nrf2
