This paper outlines the protocol for a clinical study aimed at determining whether roflumilast (a lon-acting inhibitor of the PDE-4 enzyme) can reduce the inflammation present in patients with moderate-to-severe COPD. As part of the study, biomarkers will be used to quantify the effect that roflumilast has on both systemic and pulmonary inflammation. Previous research has shown that roflumilast can improve symptoms in patients with moderate-to-severe COPD, but this study may lead to the discovery of important biomarkers and surrogate endpoints for studying the disease.