Small airway function in children with mild-to-moderate asthmatic symptoms and healthy controls

Publication date: Available online 27 July 2018

Source: Annals of Allergy, Asthma & Immunology

Author(s): Hanna Knihtilä, Anne Kotaniemi-Syrjänen, Anna S. Pelkonen, Mika J. Mäkelä, L Pekka Malmberg

Abstract

Background: Clinical significance of small airway obstruction in mild pediatric asthma is unclear.

Objective: To evaluate small airway properties in children with mild-tomoderate asthmatic symptoms, and the association of small airway function with asthma control and exercise-induced bronchoconstriction (EIB).

Methods: Children (5-10 years) with either recurrent wheezing (n=42) or persistent troublesome cough (n=16), and healthy controls (n=19) performed impulse oscillometry (IOS), spirometry, and multiple-breath nitrogen washout (MBNW) test. Exhaled nitric oxide (NO) was measured at multiple flow rates to determine alveolar NO concentration (CALV). Asthma control was evaluated with the Childhood Asthma Control Test (C-ACT), short-acting beta2-agonist (SABA) use within the past month, and asthma exacerbations within the past year.

Results: IOS, spirometry, and exhaled NO indices which are related to small airway function differed between children with recurrent wheezing and healthy controls, whereas only forced expiratory flow at 25-75% of the forced vital capacity (FEF25-75) was associated with persistent cough. MBNW indices showed no difference between the groups. Among symptomatic children, conducting airway ventilation inhomogeneity (Scond) and CALV were associated with asthma exacerbations (p=0.028 and p=0.002, respectively), and lung clearance index (LCI) and CALV were associated with EIB (p=0.044 and p=0.004, respectively). None of the proposed small airway indices was associated with the C-ACT score or SABA use.

Conclusion: Subtle changes were observed in the proposed small airway indices of IOS, spirometry, and exhaled NO among children with mild-tomoderate recurrent wheezing. Small airway dysfunction, expressed as ventilation inhomogeneity indices and CALV, was also associated with asthma exacerbations and EIB.

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