The London COPD exacerbation (EXCEL) cohort builds on an established cohort started in 1995 and designed to study COPD exacerbations and their impact on health-status and disease progression.

Our intentions are to phenotype Chronic Obstructive Pulmonary Disease (COPD) patients on the basis of factors that a related to (a) exacerbation frequency which will include (b) lung function to assess disease severity, (c) baseline therapy, (d) airway and systemic inflammatory markers, (e) health status, (f) gene expression, (g) airway bacterial and viral load and (h) co-morbidity including cardiovascular disease, diabetes and psychological disease, (i) psychological factors,(j) mortality, (k) nasal susceptibility to rhinovirus infection, (l) heart rate variability (m) exhaled hydrogen sulphide.

Inclusion Criteria:

• Forced Expiratory Volume in 1 sec (FEV1)/Forced Vital Capacity (FVC) ratio of <0.70
• Able and willing to give informed and written consent

Exclusion Criteria:

• Patients with a history of asthma, bronchiectasis, carcinoma of the bronchus, or other significant respiratory disease were excluded.
• Patients on Immunosuppressive medications or with active cancer
• Long term steroid therapy
• Age <40 years at recruitment

Patients with COPD who are generally seen in outpatient clinic.