Orally exhaled nitric oxide levels are related to the degree of blood eosinophilia in atopic children with mild-intermittent asthma

Increased levels of nitric oxide have been found in expired air of patients with asthma, and these are thought to be related to the airway inflammator y events that characterize this disorder, Since, in adults, bronchial infla mmatory changes are present even in mild disease, the present study was des igned to evaluate whether a significant proportion of children with mild-in termittent asthma could have increased exhaled air NO concentrations, Twenty-two atopic children (aged 11.1+/-0.8 yrs) with mild-intermittent ast hma, treated only with inhaled beta(2)-adrenoreceptor agonists on demand an d 22 age-matched controls were studied, NO concentrations in orally exhaled air, measured by chemiluminescence, wer e significantly higher in asthmatics, as compared to controls (19.4+/-3.3 p arts per billion (ppb) and 4.0+/-0.5 ppb, respectively; p<0.01), Interestin gly, 14 out of 22 asthmatic children had NO levels >8.8 ppb (i,e, >2 standa rd deviations of the mean in controls), In asthmatic patients, but not in c ontrol subjects, statistically significant correlations were found between exhaled NO levels and absolute number or percentage of blood eosinophils (r =0.63 and 0.56, respectively; p<0.01, each comparison), In contrast, exhale d NO levels mere not correlated with forced expiratory volume in one second (FEV1) or forced expiratory flows at 25-75% of vital capacity (FEF25-75%) or forced vital capacity (FVC), either in control subjects, or in asthmatic patients (p>0.1, each correlation), These results suggest that a significant proportion of children with mild-i ntermittent asthma may have airway inflammation, as shown by the presence o f elevated levels of nitric oxide in the exhaled air, The clinical relevanc e of this observation remains to be established.