Supplemental oxygen prevents exercise-induced oxidative stress in muscle-wasted patients with chronic obstructive pulmonary disease

Rationale: Although oxygen therapy is of clear benefit in patients with severe chronic obstructive pulmonary disease (COPD), recent studies have shown that short-term supplementary oxygen may increase oxidative stress and inflammation within the airways. Objective: We investigated whether systemic inflammation and oxidative stress at rest and during exercise in patients with COPD are influenced by supplemental oxygen. Methods: Nine normoxemic, muscle-wasted patients with moderate to very severe COPD were studied. Plasma markers of systemic inflammation (leukocyte counts, interleukin 6 [IL-6]) and oxidative stress (lipid peroxidation, protein oxidation, antioxidant capacity) were measured after treatment with either supplemental oxygen (nasal, 4 L·min^-1) or compressed air, both at rest (1 h treatment) and after submaximal exercise (40 W, constant work rate). In addition, free-radical production by neutrophils and ATP-degradation products were determined before and after exercise. Results: Short-term oxygen breathing at rest did not influence systemic low-grade inflammation and oxidative stress. The IL-6 response to exercise was attenuated during cycling with supplemental oxygen. Exercise-induced lipid and protein oxidation were prevented by treatment with supplemental oxygen. This was associated with both decreased free-radical production by neutrophils and reduced formation of (hypo)xanthine and uric acid. Conclusion: Short-term supplementary oxygen does not affect basal systemic inflammation and oxidative stress but prevents exercise-induced oxidative stress in normoxemic, muscle-wasted patients with COPD, and attenuates plasma IL-6 response. Inhibition of neutrophil activation and ATP degradation appears to be involved in this effect.