Biannual Review of Exhaled Air and Trends in Health Evaluation in COPD

This study aims to evaluate how airway inflammation, lung function, and symptoms change over time in people with chronic obstructive pulmonary disease (COPD). Airway inflammation will be assessed using a simple breath test (FeNO) and a small blood sample to measure eosinophils, a type of white blood cell. Participants will be followed for one year, with three study visits (at the start, 6 months, and 12 months). The goal is to understand how these markers evolve and whether they differ between people who experience a worsening of symptoms (called exacerbations) and those who remain stable. All tests except for a small extra blood draw are part of routine COPD care. Participation does not affect standard treatment.