Forced oscillation technique in progressive pulmonary fibrosis in a single-center retrospective study

The contribution of forced oscillation technique (FOT), also called oscillometry, in diagnosis and follow-up of progressive pulmonary fibrosis (PPF) is not yet established. The aims of this monocentric retrospective study were to compare the FOT profile between patients suffering from PPF and stable non-idiopathic pulmonary fibrosis (IPF) interstitial lung diseases (ILDs), to look for a correlation between oscillometry and conventional function tests currently used for PPF follow-up and functional definition (forced vital capacity (FVC) and diffusing lung capacity (DLCO)) and correlation with ILD severity according to FVC. Compared to non-IPF stable ILDs (n = 94), PPF patients (n = 45) showed lower median reactance at 5Hz (Xrs5) values (during inspiratory phase: 0.31 versus -0.39 expressed as Z-scores, p = 0.019595). Xrs5 also showed moderate correlation with FVC and DLCO. Finally, among all ILDs (n = 160), Xrs5 showed correlation with disease severity according to FVC. These results suggest that, in conjunction with conventional pulmonary function tests, FOT could be an interesting tool to predict progressive course of fibrosing non-IPF ILDs. Its exact contribution to PPF diagnosis and follow-up needs to be determined by a prospective approach.