60 patients to be included who are adult patients admitted to hospital with a clinical diagnosis of acute exacerbation of Chronic Obstructive Pulmonary Disease (COPD). Acute exacerbation of COPD will be defined as sustained worsening of the patient's condition with an increase in cough and one or more of dyspnoea, sputum volume or sputum purulence, necessitating a change in regular medication.