Fractional exhaled nitric oxide and forced expiratory flow between 25% and 75% of vital capacity in children with controlled asthma

Purpose: Fractional exhaled nitric oxide (FeNO) and forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) are not included in routine monitoring of asthma control. We observed changes in FeNO level and FEF(25-75) after FeNO-based treatment with inhaled corticosteroid (ICS) in children with controlled asthma (CA).

Methods: We recruited 148 children with asthma (age, 8 to 16 years) who had maintained asthma control and normal forced expiratory volume in the first second (FEV(1)) without control medication for ≥3 months. Patients with FeNO levels >25 ppb were allocated to the ICS-treated (FeNO-based management) or untreated group (guideline-based management). Changes in spirometric values and FeNO levels from baseline were evaluated after 6 weeks.

Results: Ninety-three patients had FeNO levels >25 ppb. These patients had lower FEF(25-75)% predicted values than those with FeNO levels ≤25 ppb (P<0.01). After 6 weeks, the geometric mean (GM) FeNO level in the ICS-treated group was 45% lower than the baseline value, and the mean percent increase in FEF(25-75) was 18.% which was greater than that in other spirometric values. There was a negative correlation between percent changes in FEF(25-75) and FeNO (r=-0.368, P=0.001). In contrast, the GM FeNO and spirometric values were not significantly different from the baseline values in the untreated group.

Conclusion: The anti-inflammatory treatment simultaneously improved the FeNO levels and FEF(25-75) in CA patients when their FeNO levels were >25 ppb.