The main purpose of this study is to determine whether pharmacological treatment with N-acetylcysteine improves central and peripheral cardiorespiratory control and physical capacity in COPD patients with mild-to-moderate airflow obstruction.

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. Cardiovascular complications constitute the main causes of poor physical capacity and healthcare resources utilization in COPD. There is emerging evidence that these impairments have a major impact on the health of patients with mild-to-moderate disease, the largest sub-population of COPD. This important problem, however, is currently neglected as no specific pharmacological treatment is offered to these patients. Recent studies indicate that vascular abnormalities are mediated, at least in part, by circulating inflammatory substances and direct damage of the arteries by oxygen radicals (oxidative stress). The current investigation will test the hypothesis that N-acetylcysteine (NAC), via its anti-inflammatory and antioxidant properties, improves systemic vascular function and physical capacity in COPD patients with mild-to-moderate airflow obstruction.

Inclusion Criteria:

• stable COPD with mild-to-moderate airflow obstruction as indicated by the low ratio between forced expiratory volume in one second and forced vital capacity (FEV1/FVC<0.7) together with post-bronchodilator FEV1≥60% predicted under optimized clinical treatment as judged by the accompanying physician

Exclusion Criteria:

• unable to perform all experimental procedures and/or provide informed consent;
• hospital admission in the previous 6 weeks;
• exercise training program in the previous 6 months;
• any condition that could interfere with the ability to exercise;
• diagnosed psychiatric or cognitive disorders;
• type I insulin-dependent diabetes mellitus;
• excessively over-weight (BMI>35kg/m²);
• other diagnosed cardiorespiratory disorders (e.g., chronic heart failure, peripheral artery disease).

Adverse event data collected over the 4-day treatment period (NAC and placebo).