Impulse oscillometry (IOS) in Interstitial Lung Diseases: clinical- functional- radiological correlations

Introduction: Interstitial lung diseases (ILD) are a heterogeneous group of diseases characterized by inflammation and/or fibrosis. Small airways ( Objectives: Assess small airways involvement through IOS in patients with ILD. Assess a possible correlation between small airways resistance, reactance and symptoms. Assess a possible correlation between the values R5-R20 and the degree of small airways involvement in HRTC. Methods: A single-center prospective cohort study. Patients with different diagnoses of ILD were divided in two subgroups: fibrosing ILD and non-fibrosing ILD. They underwent spirometry, HRTC and IOS. Parameters collected were: R5 (total airway resistance), R20 (central airway resistance); R5-R20 (small airway resistance), AX (reactance area), X5 (reactance measured at a 5 Hertz frequency). Results: 70 patients with a diagnosis of ILD have been enrolled: 33 with fibrosing ILD, 37 with non-fibrosing ILD. The fibrosing ILD group has R5-R20 higher than non-fibrosing ILD group statistically significant and in fibrosing ILD group R5-R20 increases with the age of patients. In fibrosing ILD there is a inverse statistically significant correlation of X5 with the FVC % predicted. In non-fibroing ILD, the thickening of the bronchiolar walls is associated with an increase in R5-R20 statistically significant. Conclusion: IOS could be useful in ILD to value the small airways involvement together with HRCT. Reactance could have a role in the functional follow-up of fibrosing ILD patients.