Small Airway Dysfunction in Children With Controlled Asthma.

Introduction: Asthma is characterized by chronic inflammation of the central and distal airways. The aim of this study was to assess the small airway (SA) of children with moderate-severe asthma with normal FEV1.

Methods: This was an open-label, prospective, observational, cross-sectional study with consecutive inclusion of patients with moderate-severe asthma, receiving standard clinical treatment, with normal baseline FEV. We determined multiflow FEno (CAno), oscillatory resistance and reactance (R5-R20, X5), forced spirometry (FEV1, FEF), total body plethysmography (RV/TLC) and bronchodilation test. SA involvement was defined as: CAno>4.5 ppb, R5-R20>0.147kPa/L/s, X5<-0.18kPa/L, FEF<-1.65 z-score, RV/TLC>33%. Poor asthma control was defined as ≤ 19 points on the ACT questionnaire or ≤ 20 on the c-ACT.

Results: In a cohort of 100 cases, 76 had moderate asthma and 24 had severe asthma; 71 children were classified as poorly controlled and 29 were well-controlled. In total, 77.78% of the group with all the correct determinations (n=72) showed ≥ 1 altered SA parameter and 48.61% ≥ 2 parameters. There were no differences between well-controlled or poorly controlled cases.

Conclusions: Children with moderate-severe asthma, with normal FEV, show a phenotype of dysfunctional SA. In our series, the evaluation of SA using the techniques described above did not provide information on disease control.