Can lung function tests help identify functional phenotypes in children with asthma?

Aim of the study: To evaluate the role of spirometry, BDR, and plethysmography, in identifying functional phenotypes in asthmatic children. Hypothesis: Different functional phenotypes can be identified in asthmatic children; if air-trapping is the most common functional phenotype, spirometric parameters cannot predict its presence. Material and Methods: The lung function using spirometry, BDR, and plethysmography was evaluated at asymptomatic conditions at 93 children with bronchial asthma. Multivariate logistic regression assessed the likelihood of having reversibility of FEV1 after BD, also if FEV1 and ∆FEV1 after BD can predict the presence of air-trapping. Results: 10.8% of patients had FEV1<80%; obstruction was found in 66.7% of the patients through sRaw. Positive BDR was confirmed in 50% of the patients. High FEV1 values have high chances of reversibility (χ2(4) =19.44, p = 0.02). RV detected air-trapping in 79.3% of the patients. FEV1 and ∆FEV1 after BD cannot predict the presence of air-trapping (OR 0.99, OR 1.03). Conclusion: Although basal spirometry is normal in most children with asthma, the measurement of BDR, sRaw, and static lung volumes, reveal important functional phenotypes. Plethysmographic measurement of sRaw is more sensitive than spirometry to detect bronchial obstruction. In clinically stable patients with normal spirometry, BDR serves as an early detector of bronchial dysfunction. Air-trapping is the most frequent functional phenotype; spirometric parameters cannot predict its presence. For its evaluation, it is recommended measurement of static lung volumes.