Small airway function in children with mild to moderate asthmatic symptoms
Hanna Knihtilä1, Anne Kotaniemi-Syrjänen1, Anna S Pelkonen1
1Pediatric Unit, Department of Allergy, Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Insights
Small airway obstruction in children with recurrent wheezing shows subtle changes detectable by impulse oscillometry and exhaled nitric oxide. This dysfunction is linked to asthma exacerbations and exercise-induced bronchoconstriction (EIB).
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Asthma Research
Background:
- The clinical significance of small airway obstruction in mild pediatric asthma remains unclear.
- Evaluating small airway function is crucial for understanding asthma in children.
Purpose of the Study:
- To assess small airway properties in children experiencing mild to moderate asthmatic symptoms.
- To determine the association between small airway function, asthma control, and exercise-induced bronchoconstriction (EIB).
Main Methods:
- Children aged 5-10 with recurrent wheezing or persistent cough, and healthy controls, underwent impulse oscillometry (IOS), spirometry, and multiple-breath nitrogen washout (MBNW).
- Exhaled nitric oxide (NO) was measured at multiple flow rates to calculate alveolar NO concentration (Calv).
- Asthma control was assessed using the Childhood Asthma Control Test (C-ACT), short-acting β2-agonist (SABA) use, and exacerbation history.
Main Results:
- IOS, spirometry, and exhaled NO indexes related to small airways differed between children with recurrent wheezing and controls.
- Airway ventilation inhomogeneity and Calv correlated with asthma exacerbations.
- Lung clearance index and Calv were associated with EIB in symptomatic children.
Conclusions:
- Mild to moderate recurrent wheezing in children is associated with subtle changes in small airway function, measurable by IOS and exhaled NO.
- Small airway dysfunction, indicated by ventilation inhomogeneity and Calv, is linked to increased asthma exacerbations and EIB.
Background:
Clinical significance of small airway obstruction in mild pediatric asthma is unclear.
Objective:
To evaluate small airway properties in children with mild to moderate asthmatic symptoms and the association of small airway function with asthma control and exercise-induced bronchoconstriction (EIB).
Methods:
Children (5-10 years old) with recurrent wheezing (n = 42) or persistent troublesome cough (n = 16) and healthy controls (n = 19) performed impulse oscillometry (IOS), spirometry, and a 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 β2-agonist (SABA) use within the past month, and asthma exacerbations within the past year.
Results:
IOS, spirometry, and exhaled NO indexes that are related to small airway function differed between children with recurrent wheezing and healthy controls, whereas only forced expiratory flow at 25% to 75% of the forced vital capacity was associated with persistent cough. The MBNW indexes showed no difference between the groups. Among symptomatic children, conducting airway ventilation inhomogeneity and Calv were associated with asthma exacerbations (P = .03 and P = .002, respectively), and lung clearance index and Calv were associated with EIB (P = .04 and P = .004, respectively). None of the proposed small airway indexes was associated with the C-ACT score or SABA use.
Conclusion:
Subtle changes were observed in the proposed small airway indexes of IOS, spirometry, and exhaled NO among children with mild to moderate recurrent wheezing. Small airway dysfunction, expressed as ventilation inhomogeneity indexes and Calv, was also associated with asthma exacerbations and EIB.
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