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.