Fireman Klein E, et al. – In this study, researchers assessed exhaled breath condensate (EBC)-ultrafine particles (UFP) content as a reflection of inflammation and oxidative stress status in COPD patients and as a risk marker for exacerbation. Using conventional methods, they collected EBC, and used ELISA kits to measure EBC carbonyl and 8-hydroxydeoxyguanosine (8-OHdG) levels. The study population (58 COPD patients and 40 healthy smoker and non-smoker controls) had spirometry, diffusion capacity, EBC testing, and blood sampling done. Compared with controls, absolute eosinophil count, C-reactive protein, and lactate dehydrogenase in serum were elevated in the COPD group. Findings suggested that UFP content in EBC reflects airway inflammation and oxidative stress. The hypothesis that increased epithelial permeability could be the mechanism behind these findings is supported by low UFP concentrations in EBC and high in the serum of COPD patients.