Chronic obstructive pulmonary disease (COPD) is a heterogeneous condition with recurrent exacerbations despite guideline-based therapy. This prospective observational cohort study aims to evaluate whether baseline fractional exhaled nitric oxide (FeNO), a biomarker of type 2 airway inflammation, predicts future exacerbations and lung function decline in COPD patients initiated on triple inhaler therapy in routine clinical practice. The study will also explore the relationships between air pollution exposure, type 2 inflammatory biomarkers, and COPD outcomes.