Resistance Heterogeneity and Small Airway Asthma Phenotype Reply

We read with interest the elegant modeling data of Foy and colleagues (1), who reported a 40% narrowing of small airways was associated with clinically relevant alterations in asthma control and quality of life. Such effects were commensurate with observed responses to biologics on the frequency-dependent heterogeneity of the resistance component of respiratory impedance measured by impulse oscillometry (IOS), where the mean pooled effect on resistance at 5 Hz (R5) 2 resistance at 20 Hz (R20) was 20.04 (95% confidence interval [CI], 20.03 to 20.05) (kPa/L) $ s.