Exhaled breath condensate pH and exhaled nitric oxide in allergic asthma and in cystic fibrosis

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Abstract
Background: It has been proposed that the pH of airway lining fluid may regulate the fractional exhaled concentration of nitric oxide (FeNO) in respiratory disease. Methods: FeNO, exhaled breath condensate (EBC) pH, and EBC concentrations of nitrite plus nitrate (NO2/NO3) were compared in 12 subjects with stable asthma, 18 with stable cystic fibrosis (CF), and 15 healthy control subjects. Eight of the CF patients were studied on a separate occasion at the start of a pulmonary exacerbation. Results: FeNO was significantly greater in asthmatic subjects than in control subjects (mean 35 v 9 ppb, pv 6.08, p = 0.23). Levels of NO2/NO3 were on average higher in EBC samples from asthmatic subjects, but the difference was not significant. In patients with stable CF both the FeNO (mean 4 ppb, p2/NO3 (median 29.9 μM; p = 0.002) in patients with stable CF, in contrast, were significantly higher than in control subjects. During CF exacerbations, EBC pH was further reduced (median 5.30, p = 0.017) but FeNO and NO2/NO3 were unchanged. Conclusions: These findings demonstrate a dissociation between EBC pH and FeNO in inflammatory airways disease.