Exhaled Breath Condensate pH as a Non-invasive Measure of Inflammation in Non-CF Bronchiectasis

Bronchiectasis is characterised by neutrophilic bronchial inflammation. Direct measurement of lung inflammation would be useful to assess disease activity, guide need for treatment, and monitor response. The aim of this study was to test whether exhaled breath condensate (EBC) pH, a simple noninvasive test, provides a clinically useful measure of inflammation in the lungs of patients with bronchiectasis. 96 consecutively referred patients were studied when clinically stable, 20 followed up over two years, and a further 22 patients seen during an exacerbation. Subjects breathed tidally for 10 minutes into a condensing chamber (Ecoscreen, Erich Jaeger, Hoechberg, Germany). pH in EBC was measured immediately using a pH probe. In a representative group of 25 patients samples were deaerated with argon gas. This was to control for variations in pH ex vivo by removing CO2. EBC was acidic in bronchiectasis patients (6.79±0.72) compared to controls (7.08±0.69) and primary ciliary dyskinesia patients (7.24±0.53). pH was related to lung volume but not disease severity. Repeated measures show EBC pH changes with symptoms. EBC is further acidified during an exacerbation of bronchiectasis (6.44±0.72), this acidification persists following treatment (6.09±0.80). EBC pH is not sufficiently sensitive or specific to monitor patients' health status or provide information to inform acute treatment decisions.