Exhaled nitric oxide and exercise-induced bronchoconstriction in young wheezy children – interactions with atopy

The association between exercise-induced bronchoconstriction (EIB) and exhaled nitric oxide (FE_NO) has not been investigated in young children with atopic or non-atopic wheeze, two different phenotypes of asthma in the early childhood. Steroid naïve 3- to 7-yr-old children with recent wheeze (n = 84) and age-matched control subjects without respiratory symptoms (n = 71) underwent exercise challenge test, measurement of FE_NO and skin prick testing (SPT). EIB was assessed by using impulse oscillometry, and FE_NO by standard online technique. Although FE_NO levels were highest in atopic patients with EIB, both atopic and non-atopic wheezy children with EIB showed higher FE_NO than atopic and non-atopic control subjects, respectively. In atopic wheezy children, a significant relationship between FE_NO and the severity of EIB was found ( r  = 0.44, p = 0.0004), and FE_NO was significantly predictive of EIB. No clear association between FE_NO and EIB or predictive value was found in non-atopic wheezy children. Both atopic and non-atopic young wheezy children with EIB show increased FE_NO levels. However, the association between the severity of EIB and FE_NO is present and FE_NO significantly predictive of EIB only in atopic subjects, suggesting different interaction between bronchial responsiveness and airway inflammation in non-atopic wheeze.