Oscillometry in Chronic Respiratory Diseases: From Standardization to Clinical Adoption

Objective: Oscillometry is a lung function technique that has gained increasing interest because of its sensitivity to small airway dysfunction. Despite growing attention, important challenges still limit widespread clinical adoption. The current study aims to advance in Oscillometry analysis and reporting to improve repeatability, interpretability, and clinical applicability. Methods: Oscillometry, forced spirometry, and symptoms were measured at three time points, over a median follow-up of 602 days, in 170 patients with COPD (n=89, 52%), asthma (n=59, 35%), and bronchiectasis (n=22, 13%). We investigated: (1) intra-breath analysis; (2) several modelling strategies to derive a single oscillometry score for routine clinical interpretation; and (3) intra-individual variability. Outcomes were evaluated across three clinical scenarios: bronchodilator response, longitudinal follow-up, and exacerbations. Results: Intra-breath differences between inspiratory and expiratory phases (ΔX5 and ΔAX) reflected respiratory hysteresis but had poor repeatability (daily CoV: 200% and 70%, respectively). Resistance-related variables (R5, R5–20) showed lower sensitivity than reactance-related indices (AX, X5, Fres). An AX-based calibrated oscillometry score (AX-OS) provided the best index among the candidate models evaluated. AX-OS had higher repeatability (CoV 19%) than conventional oscillometry variables, and good clinical responsiveness across the three clinical scenarios assessed. Moreover, AX-OS showed potential for contributing to enhanced community-managed exacerbations through a hybrid care intervention. Conclusions: The findings support: (1) well-defined strategies to reduce intra-session variability, particularly through optimization of AX-derived measures; and (2) simplified clinical reporting approaches. AX-OS may improve interpretability and longitudinal assessment; however, independent validation in larger multicentre cohorts is needed before routine clinical applicability. Trial registration: NCT06421402. Keywords: forced oscillation technique; small airway; COPD; asthma; repeatability; biomarkers; respiratory mechanics.