Non-invasive collection of exhaled breath condensate in rats: Evaluation of pH, H2O2 and NOx in lipopolysaccharide-induced acute lung injury

The analysis of exhaled breath condensate (EBC) offers the potential for identifying lung disease markers in humans and animals, but methodological issues and standardised procedures need to be addressed before the technique can be considered for use in applications to help understand the role of environmental pollution in respiratory diseases. The purpose of this study was to develop and implement a new device using a glass-chamber for collecting EBC non-invasively from rats in order to analyse EBC markers in lipopolysaccharide (LPS)-induced acute lung injury. Eighty-four adult rats were used in five different series of experiments to determine the source of EBC formation, intra-day and inter-day variability, and the influence of environmental parameters on EBC markers. The hypothesis that inflammation induces an oxidative stress was assessed by measuring pH, nitrogen oxides (NOx) and hydrogen peroxide (H2O2) in EBC.The results confirmed that EBC fluid was generated at the level of the respiratory tract. The repeatability studies of disease markers indicated higher concentrations of NOx and H2O2 at midday compared to the morning, but there were no significant difference between measurements on consecutive days. EBC volume was influenced by both ambient temperature and humidity. Moreover, 3 h after LPS challenge, significantly increased concentrations of both NOx and H2O2 were observed in EBC of the LPS group compared with controls (P = 0.005 and P = 0.027, respectively). These results suggested that EBC collection may be a valuable tool to monitor the presence of markers, such as NOx and H2O2, in an animal model of LPS-induced acute lung injury.