Exhaled Breath Condensate Ph Is Correlated With Post-exercise Small Airway Obstruction

Abstract

PURPOSE: It has been shown that individuals with asthma and exercise-induced bronchoconstriction (EIB) exhibit lower exhaled breath condensate (EBC) pH values than healthy individuals. The purpose of this study was to determine if EBC pH was correlated with the degree of airway obstruction following a bronchial hyperresponsiveness challenge. METHODS: Twenty three subjects [15 asthmatics subjects with EIB, as determined by a post-EVH drop of ≥ 10% in FEV1; 8 control subjects (no-asthma/no EIB)] were asked to breathe normally at rest for 10 min wearing a nose clip while their exhaled breath was collected (EcoScreen, Jager, Hoechberg, Germany). The pH of the condensate was measured immediately following collection. Subsequently subjects underwent a eucapnic voluntary hyperventilation (EVH) challenge. The EVH challenge required each subject to hyperventilate for 6 min at a ventilation calculated as 30 × the volume of baseline FEV1, while breathing a gas mixture containing 5% CO2, 21% O2, and balance N2. Pulmonary function was measured pre-EVH and post-EVH at 5, 10, 15, and 20 min. RESULTS: The EBC pH was significantly (p<0.05) lower in the subjects that exhibited EIB (6.83±0.43) as compared to those who did not (7.37±0.32). The EBC pH was not significantly correlated to the post-EVH drop in FEV1 (r=0.048, p=0.827). However, EBC pH was found to be significantly inversely correlated to post challenge drop in FEF25-75% (r=0.579, p=0.004). CONCLUSION: Exhaled breath condensate pH was significantly lower in subjects who exhibit EIB than in healthy control individuals, which may indicate acidification of the airways in individuals with airway hyperresponsiveness. The pH was also inversely related with the post-EVH drop in FEF25-75% indicating that the lower EBC pH in the airways may be indicative of heightened reactivity in the small airways.