Peripheral airway function and disease burden in COPD.

Background: While oscillometry appears advantageous over spirometry in detecting peripheral airway dysfunction, a feature of COPD, further research on its role in disease monitoring is needed. The objectives of the present study were to analyse the associations between oscillometry by impulse oscillometry (IOS) and forced oscillation technique (FOT) and airway obstruction, health status, dyspnoea and future exacerbations in COPD.

Methods: Oscillometry and disease burden were assessed in 150 adults with COPD within the Tools Identifying Exacerbations study. At 5 Hz, abnormal resistance (R _rs5) and reactance (X _rs5) were defined as z-scores >1.645 and <-1.645 sd, respectively, whereas a mean difference in reactance between inspiration and expiration >2.80 cmH₂O·L^-1·s^-1 represented abnormal ΔX _rs5. Forced expiratory volume in 1 s (FEV₁), COPD Assessment Test (CAT) and modified Medical Research Council (mMRC) scores were obtained. Medical records were reviewed for future exacerbations (≥1) between baseline and 1 and 3 years, respectively.

Results: Abnormal oscillometry correlated with disease burden, with the highest risk observed for severe airway obstruction (FEV₁ <50% pred): odds ratios with 95% confidence intervals ranging from 4.80 (1.93-12.0) to 18.0 (7.13-45.3) for R _rs5, X _rs5 and ΔX _rs5, followed by moderate to severe dyspnoea (mMRC ≥2) for ΔX _rs5, COPD health status (CAT ≥10) for R _rs5 and ΔX _rs5 and future exacerbations (1 and 3 years) for R _rs5 and X _rs5, respectively, with odds ratios (95% CI) ranging from 2.77 (1.27-6.05) to 3.98 (1.38-11.5).

Conclusions: Abnormal oscillometry may be relevant in the evaluation of COPD patients, including the prediction of future exacerbation risk.