Exploring Small Airway Disease in Idiopathic Pulmonary Fibrosis Patients: Insights from Oscillometry Analysis

Background: Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease characterized by lung scarring. Recent evidence suggests that small airway dysfunction (SAD) contributes to IPF pathogenesis. This study assessed SAD in IPF patients using oscillometry and examined associations with disease severity and cardiovascular comorbidity. Methods: Forty-eight IPF patients were included in this cross-sectional study. Lung function was assessed using forced oscillation technique (FOT) and impulse oscillometry (IOS), spirometry, plethysmography, and DLCO measurements. Key parameters, including AX, Fres, and R5-R20, were analyzed. Correlations between oscillometry parameters, disease severity indices (GAP index, MRC dyspnea score), and coronary artery disease (CAD) risk were evaluated. Results: Elevated R5-R20 was observed in 65% of patients (FOT) and 60% (IOS). Increased Fres was found in 94% (FOT) and 90% (IOS), while AX was elevated in all participants. Significant correlations were found between AX and DLCO% (r = -0.502, p < 0.001), and between Fres and DLCO% (r = -0.705, p < 0.001). Higher AX was associated with increased CAD score (r = 0.283, p = 0.045), while improved lung compliance (less negative X5) correlated with a lower CAD score (r = -0.314, p = 0.037). No significant correlations were found between oscillometry parameters and GAP or MRC scores. Conclusion: SAD is prevalent in IPF and is associated with impaired gas exchange and increased cardiovascular risk. Oscillometry provides valuable insights into lung stiffness and small airway resistance, particularly in cases where spirometric abnormalities may not be evident, supporting its use in monitoring disease progression in IPF.