Ventilation heterogeneity is associated with airway responsiveness in asthma but not COPD

- We investigate predictors of airway hyperresponsiveness (AHR) in older asthmatic and COPD patients.
- In COPD AHR is predicted by less peripheral ventilation heterogeneity and lower forced vital capacity.
- In asthma AHR is predicted by more peripheral ventilation heterogeneity and higher residual volume.
- AHR is different in asthma and COPD and is determined by underlying disease-specific processes.

Airway hyperresponsiveness (AHR) occurs in both asthma and COPD. In older people with asthma, AHR is associated with increased acinar ventilation heterogeneity, but it is unknown if this association exists in COPD.Thirty one COPD and 19 age-matched asthmatic subjects had measures of spirometry, lung volumes, exhaled nitric oxide, ventilation heterogeneity, and methacholine challenge. Indices of acinar (Sacin) and conducting (Scond) airway ventilation heterogeneity were calculated from the multiple breath nitrogen washout. Predictors of AHR were then determined.In COPD, AHR was predicted by lower Sacin and lower FVC (model r2 = 0.35, p = 0.001). In asthma, AHR was predicted by higher Sacin and higher residual volume (model r2 = 0.62, p < 0.001).These findings suggest that airway responsiveness in COPD and asthma is determined by underlying disease-specific processes, rather than a common pattern of physiological abnormality.