Exploring small airway disease in idiopathic pulmonary fibrosis patients: insights from oscillometry analysis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease, with small airway dysfunction (SAD) increasingly recognized as part of its pathophysiology. This study evaluated SAD prevalence and its association with gas exchange and cardiovascular risk using oscillometry.

Forty-eight IPF patients underwent forced oscillation technique (FOT), impulse oscillometry (IOS), spirometry, plethysmography, and DLCO. Key oscillometry indices (R5, R20, R5-R20, X5, AX, Fres) were analyzed. Associations with DLCO%, GAP index, MRC dyspnea score, and Framingham Risk Score (FRS) were assessed. Multivariable regression adjusted for age, sex, smoking, TLC%, antifibrotic use, and GAP stage.

SAD was highly prevalent, with abnormal AX in all participants, elevated Fres in > 90%, and abnormal R5-R20 in ~ 60%, using both FOT and IOS, confirming consistency across devices. AX and Fres correlated strongly with DLCO% (r = - 0.50, - 0.70; both p < 0.001) and remained independently associated after adjustment. Both also correlated with FRS (p < 0.05), suggesting a link between lung stiffness and cardiovascular risk. No associations were seen with GAP or MRC scores. FOT and IOS showed excellent agreement for oscillometric parameters (r > 0.8), demonstrating strong concordance between the two measurement systems.

SAD is a common, clinically relevant feature of IPF. AX and Fres may serve as sensitive, non-invasive markers for disease monitoring and cardiovascular risk assessment. Further multicenter, longitudinal studies are needed to validate these findings and establish the role of oscillometry in routine clinical practice.