Abstract
Several non-invasive biomarkers have been used to investigate the pathophysiology, treatment and prognosis of COPD. However, for most markers there is no standardized procedure and few randomised studies have been performed with COPD patients. We have developed an efficient, sensitive and reproducible procedure for measuring hydrogen peroxide (H2O2) in exhaled breath condensate (EBC) and have shown that it is important to have a low detection limit. We also found that the H2O2 concentration increases significantly over the day in both COPD patients and healthy controls. It is possible that exhaled H2O2 levels are influenced by the intake of food and drinks or exercise and it is therefore very important to perform H2O2 measurements in follow-up studies at the same time of day in the same conditions. In contrast to other investigators, we did not find significant higher exhaled H2O2 concentrations in stable COPD patients compared with healthy controls, possibly because our control group was matched with the patient group for age and smoking status. The number and activation of inflammatory cells seem to be increased in COPD patients compared with healthy persons, we showed that peripheral neutrophils are more easily activated by certain stimuli to release superoxide. No changes were observed in exhaled H2O2 levels during a COPD exacerbation and subsequent treatment. In contrast, serum inflammatory markers such as ESR, CRP and MPO concentration did show a reduction during treatment. This means that these parameters are more appropriate to evaluate the effect of treatment during exacerbation than exhaled H2O2 levels. Finally, we used exhaled H2O2 levels to evaluate the effect of two different ICS in stable COPD patients. The exhaled H2O2 levels decreased in both treatment groups after four weeks and the effect lasted for several weeks after discontinuation. We found no difference in effect between both ICS. This study shows that ICS do influence the concentration of exhaled H2O2.
