Evaluation of methodological and biological influences on the collection and composition of exhaled breath condensate

The purpose of this inter-species comparison (calves and pigs) was to identify methodological and biological influences on the collection and composition of exhaled breath condensate (EBC). A total of 352 EBC samples were collected, whilst variables of ventilation were registered in parallel. Partial pressure of carbon dioxide (pCO₂) and pH were analysed in non-degassed EBC samples. The concentration of total protein in EBC was measured colorimetrically. In both species, lung function was evaluated before and after EBC collection. Statistical analyses were performed to study the effect of EBC collection on lung function and to identify the influence of ventilatory variables on the collection and composition of EBC. Collection of EBC did not affect lung function. Despite the volume of EBC collected per unit time being primarily dependent on ventilation per unit time, species-specific conditions during the EBC collection process resulted in different dependences of EBC collection from other variables of ventilation (i.e. maximal airflow during expiration or expired tidal volume kg^-1 body weight). The concentration of protein ml^-1 EBC increased with the expired volume per min and with peak expiratory flow. Although the pCO₂ in fresh EBC was significantly negatively dependent on the duration of collection, comparable pHs (5.6 - 6.2) were measured in EBC of both calves and pigs. The obtained data may help one standardize EBC collection in different species.