Correlations between exhaled nitric oxide levels and pH-metry data in asthmatics with gastro-oesophageal reflux

Background: In gastro-oesophageal reflux (GER), micro-aspirations of gastric fluid may damage the epithelial surface of the airways, an important source of endogenous nitric oxide (NO). Objectives: The aim of the study was to evaluate the possible infl uence of GER on fractional exhaled nitric oxide (FE_NO) release. Methods: FE_NO levels were compared in two age-matched groups of allergic children: (1) 20 with mild asthma, responding to standard anti-asthma pharmacologic therapy (asthmatic children) and (2) 12 with mild 'asthma-like symptoms' and GER. Results: No differences in pulmonary functions parameters (FEV₁ , FVC and FEF_25-75%) were found between the two groups of children (p > 0.1); FE_NO levels were higher in asthmatic children compared with GER children (p = 0.0001). GER children underwent 24-hour oesophageal pH-metry, and possible correlations between pH-metry data, pulmonary functions and FE_NO levels were evaluated. No correlations were found between pulmonary functions and pH-metry data (p > 0.05, each correlation). In contrast, correlations were observed between FE_NO levels and pH-metry data, including (1) percentage of study time with pH <4 (r = -0.80, p = 0.008), (2) number of episodes with pH <4 (r = -0.76, p = 0.012), and (3) number of episodes >5 min with pH <4 (r = -0.69, p = 0.02). Conclusions: Thus, FE_NO levels are lower in allergic children with 'asthma-like symptoms' and GER as compared to asthmatic children. The correlations between FE_NO levels and pH-metry data suggest that inhalation of acid gastric content may interfere with NO production in the airways.