Abstract
Fractional exhaled nitric oxide (FeNO) is a non-invasive marker of airway inflammation in asthma and respiratory allergy. Environmental factors, especially indoor and outdoor air quality, may play an important role in triggering acute exacerbations of respiratory symptoms. The authors have reviewed the literature reporting effects of outdoor and indoor pollutants on FeNO in children. Although the findings are not consistent, urban and industrial pollution—mainly particles (PM2.5 and PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2)—as well as formaldehyde and electric baseboard heating have been shown to increase FeNO, whilst ozone (O3) tends to decrease it. Among children exposed to Environmental Tobacco Smoke (ETS) with a genetic polymorphisms in nitric oxide synthase genes (NOS), a higher nicotine exposure was associated with lower FeNO levels. Finally, although more studies are needed in order to better investigate the effect of gene and environment interactions which may affect the interpretation of FeNO values in the management of children with asthma, clinicians are recommended to consider environmental exposures when taking medical histories for asthma and respiratory allergy. Further research is also needed to assess the effects of remedial interventions aimed at reducing/abating environmental exposures in asthmatic/allergic patients.
Highlights
Elevated levels of nitric oxide in exhaled air are considered a noninvasive marker of airway inflammation in asthma and respiratory allergy management [1]
In mild-to-moderate persistent asthmatic children followed by Childhood Asthma Research and Education (CARE) Network supported by NHLBI, a highly significant correlation of Fractional exhaled nitric oxide (FeNO) levels with blood eosinophilia was found [3]
Clinicians should take into account some indoor pollution factors, like indoor allergens [4, 31, 32], mainly Dermatophagoides and pets, electric baseboard heating [32], higher formaldehyde concentrations in houses [34], using of woodstoves, candles or gas cookers [35, 36], chlorine, or polyvinyl chloride (PVC) exposure [36, 38] for which increase FeNO values are found in children
Summary
Elevated levels of nitric oxide in exhaled air (fractional concentration of exhaled nitric oxide, FeNO) are considered a noninvasive marker of airway inflammation in asthma and respiratory allergy management [1]. FeNO is faster and easier to obtain than other measurements of inflammation such as sputum eosinophils level [5] For these reasons, some authors use it as a complementary tool to lung function tests in order to obtain a better control of clinical symptoms and asthma exacerbations [6]. There has been an increase in the prevalence of asthma and allergic diseases, among children living in the urban areas of economically developed countries This has led to suppose that environmental factors, especially indoor and outdoor air quality, may play an important role in the development of allergy and in triggering acute exacerbations of respiratory symptoms [10]. The aim of this review is to make a reappraisal of the current evidences on whether environmental factors, such as outdoor and indoor pollutants, affect FeNO in children
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