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 (FEF25-75) are not included in routine monitoring of asthma control. We observed changes in FeNO level and FEF25-75 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 (FEV1) 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 FEF25-75% predicted values than those with FeNO levels ≤25 ppb (P25 ppb.