Reply to Janssen and Wouters: Loss of Alveolar Attachments as a Pathomechanistic Link between Small Airway Disease and Emphysema

Vasilescu et al commend Dr Janssen and Dr Wouters for highlighting the importance of their study to validate parametric response mapping (PRM) as an imaging biomarker to identify small airway disease in patients with chronic obstructive pulmonary disease (COPD). They agree with them that their data provide further support for the notion, as previously stated, that small airway disease is an important target for COPD therapies. The unique data set and tissues available from their work clearly demonstrate that the number of terminal bronchioles is significantly reduced in lung regions where the airspace size (a surrogate for emphysema) remains below the detectible level of clinical computed tomography, and that these regions are predominantly classified as PRM functional small airway disease. In contrast, the data show that the number of terminal bronchioles is further reduced in regions where PRM emphysema is dominant. However, their data were obtained from patients with severe COPD and cannot unambiguously define whether this pathological process is the same for all patients with COPD.