Fractional Exhaled Nitric Oxide and Exacerbations of COPD

Fractional Exhaled Nitric Oxide (FeNO) as a Predictor of Exacerbations in COPD Patients Initiated on Triple Inhaler Therapy: A Prospective Exploratory Cohort Study

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.

This is a pragmatic, prospective, longitudinal observational cohort study conducted in patients with COPD who are initiated on triple inhaler therapy as part of routine clinical care. No investigational drugs, devices, or protocol-mandated interventions are administered. Biomarker measurements, including fractional exhaled nitric oxide (FeNO), are performed for research purposes only and do not influence clinical decision-making.

Participants will be followed for up to 12 months after enrollment with scheduled assessments of exacerbation events, lung function, symptom burden, and biomarkers. The total study duration is approximately 24 months, accounting for a 12-month enrollment period and completion of follow-up for the last enrolled participant. Environmental air pollution exposure will be estimated using a validated hybrid kriging/land-use regression model based on residential address.

Inclusion Criteria:

• Adults aged 40 years or older
• Diagnosis of chronic obstructive pulmonary disease (COPD) confirmed by post-bronchodilator spirometry (FEV₁/FVC < 0.70).
• History of cigarette smoking
• Receiving triple inhaler therapy (inhaled corticosteroid/long-acting beta-agonist/long-acting muscarinic antagonist) as part of routine clinical care, including:
• patients who have been previously escalated to triple inhaler therapy due to prior exacerbations and are already receiving triple therapy at the time of enrollment, and
• patients who are newly prescribed triple inhaler therapy at or immediately before enrollment because of a recent exacerbation.

Exclusion Criteria:

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