Partitioned-airways nitric oxide in healthy and asthmatic children. Effect of atopy and anti-inflammatory therapy.

Background. Peripheral and proximal airway contributions to nitric oxide (NO) exchange are promising tools for assessing asthma. How disease status and atopy influence partitioned-airway NO is still under investigation. Aims. To compare partitioned-airway NO concentrations with clinical data and allergen sensitization in asthmatic and healthy children. Methods. In 27 asthmatic and 53 healthy (12 atopic) children, aged 11.1±2.0 yr, 50 males), we measured the fractional NO concentration (FENO) at three exhalation flows: 50, 100 and 150 ml/s. Linear regressions of NO output with exhalation flows were used to estimate the alveolar-NO concentration (CaNO) and the maximum airway-NO flux (J’awNO). Respiratory symptoms, therapy with inhaled corticosteroids (ICs), spirometry and skin-prick testing were assessed. The sum of positive-skin wheals for either indoor and outdoor allergens was recorded. Results. Asthmatic and atopic-healthy children showed higher median (IQR) FENO, CaNO and J’awNO than non-atopic healthy children [e.g. CaNO: 8.1 (9.9) and 7.4 (4.6) ppb vs 3.3 (4.5) ppb; J’awNO: 1638.7 (1892.1) nl/s and 1108.3 (1662.6)nl/s vs 506.7 (443.3) nl/s, p<0.001]. ICs-treated patients (n=11) had lower CaNO than those steroid-naïve (n=16): 3.0 (7.2) ppb vs 9.5 (6.5) ppb, p<0.001. Multiple-linear regression analysis with NO-exchange variables as dependent with potential explanatory variables yielded CaNO explained by indoor-allergen scores and therapy with ICs whereas J’awNO model included asthma diagnosis and cough or wheeze in the past 4 weeks. Conclusion. Increased estimates of partitioned airway NO concentrations can be found in atopic children despite their disease status. Indoor, rather than outdoor allergens are associated to peripheral-airway inflammation.