Association between fraction of exhaled nitrous oxide, bronchodilator response and inhaled corticosteroid type

Fraction of exhaled nitrous oxide (FeNO) is a known marker of airway inflammation and a topic of recent investigation for asthma control in children.

To investigate the relationship among FeNO and bronchodilator response measured by spirometry and types of inhaled corticosteroids (ICS).

A one-year review of children tested with spirometry and FeNO in a regional pediatric asthma centre was conducted.

A total of 183 children were included (mean [± SD] age 12.8 ± 2.8 years). Fluticasone was used most commonly (n=66 [36.1%]), followed by ciclesonide (n=50 [27.3%]). Most children (n=73 [39.9%]) had moderate persistent asthma. Increased FeNO was associated with percent change in forced expiratory volume in 1 s (FEV1) after bronchodilator adjusted for allergic rhinitis, parental smoking and ICS type (B=0.08 [95% CI 0.04 to 0.12]; P<0.001). Similarly, FeNO was associated with percent change in forced expiratory flow at 25% to 75% of the pulmonary volume (FEF25-75) after bronchodilator adjusted for parental smoking and ICS type (B=0.13 [95% CI 0.01 to 0.24]; P=0.03). FeNO accounted for only 16% and 9% of the variability in FEV1 and FEF25-75, respectively. Mean-adjusted FeNO was lowest in fluticasone users compared with no ICS (mean difference 18.6 parts per billion [ppb] [95% CI 1.0 to 36.2]) and there was no difference in adjusted FeNO level between ciclesonide and no ICS (5.9 ppb [95% CI -9.0 to 20.8]).

FeNO levels correlated with bronchodilator response in a regional pediatric asthma centre. However, FeNO accounted for only 16% and 9% of the variability in FEV1 and FEF25-75, respectively. Mean adjusted FeNO varied according to ICS type, suggesting a difference in relative efficacy between ICS beyond their dose equivalents.