Impact of dupilumab on oscillometry and spirometry derived ratios in severe refractory asthma.

Impulse oscillometry (IOS) - a physiological effort independent technique - is used to evaluate small airways dysfunction in asthma. The absolute values produced from IOS can be challenging to understand thus, we previously proposed using oscillometry derived ratios to aid interpretation. Patients with abnormal baseline R5-R20/R5 ratio were identified and analysed if there was a significant response in their ratios pre and post treatment on dupilumab. There were significant improvements in both R5-R20/R5 and X5/AX as well as the spirometry derived ratios FEV1/FVC and FEF25-75/FVC. The type 2 biomarkers (eosinophils and FeNO) and asthma control score also showed significant improvements, although they were not significantly correlated with the oscillometry ratios. Standardised response means showed good sensitivity for both oscillometry derived ratios and spirometry derived ratios in detecting response to treatment. Based on these observations, oscillometry derived ratios may be a viable and easier to interpret alternative to using absolute values for the evaluation of small airways response to biologic therapy in a real-life clinic setting.