Impulse oscillometry indices are associated with functional impairment and progressive pulmonary fibrosis across interstitial lung diseases.

Abstract

Background: Respiratory oscillometry provides effort-independent indices of airway heterogeneity (R5-20) and respiratory system stiffness (AX). Their clinical relevance in interstitial lung diseases (ILD) remains unclear and was the aim of our study.

Research design and methods: A cross-sectional study including patients with ILD who underwent oscillometry, pulmonary function tests (PFTs), and six-minute walking distance (6MWD) at a single visit. R5-20 and AX were analyzed as continuous variables and as thresholds derived from receiver operating characteristic (ROC) analysis for progressive pulmonary fibrosis (PPF). Associations with clinical outcomes were assessed using multivariable regression models.

Results: Ninety-four patients (median age 70y; 44% females) were included. Oscillometry parameters correlated with PFTs and 6MWD, and had a moderate discriminative ability for PPF (AUC 0.747-0.764). Abnormal oscillometry was identified in 46 patients (49%) and was not associated with any baseline characteristic or ILD subtype. However, it was linked to lower DLCO (48% vs. 54% predicted, p = 0.02) and reduced 6MWD (median [IQR] 413 [354-503] vs. 465 [425-533] meters, p = 0.024). R5-20 was higher in patients with air-trapping or mosaic attenuation in chest CT, although not in those with honeycombing or traction bronchiectasis.

Conclusion: Oscillometric abnormalities are common in ILD and independently associated with disease severity.