Exhaled breath condensate biomarkers of airway inflammation and oxidative stress in COPD

Exhaled breath condensate (EBC) is a noninvasive method for collecting airway secretions and for studying the composition of the airway lining fluid. Several biomolecules, including leukotrienes, prostaglandins, isoprostanes, hydrogen peroxide, nitric oxide-derived products, hydrogen ions, and adenosine triphosphate, have been measured in healthy subjects. Some of these inflammatory mediators are elevated in patients with chronic obstructive pulmonary disease (COPD). Analysis of biomolecules in EBC is potentially useful for monitoring of lung inflammation and oxidative stress, which is an important component of inflammation, in patients with COPD. As it is completely noninvasive, EBC might also be suitable for longitudinal studies, and for monitoring the effects of pharmacological therapy in patients with COPD. Different profiles of biomarkers in EBC might reflect different aspects of lung inflammation or oxidative stress. Identification of selective profiles of biomarkers in EBC in lung diseases might have a value for differential diagnosis in respiratory medicine. However, several methodological aspects have to be formally addressed and standardization of EBC methodology is required before this technique can be considered for application in the clinical setting.