Diagnosis of exacerbations of COPD is based largely on key symptoms (increasing sputum purulence and volume, and breathlessness) and the severity depends on the level of healthcare resource utilisation. Aetiology is varied, although infection is the major causative factor. Neutrophilic inflammation is a major pathological event, but eosinophils are also implicated, suggesting an "asthmatic" aetiology. Airflow limitation and dynamic hyperinflation are the physiological changes, which can result

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... n deterioration in gas exchange and respiratory failure. Antibiotics are reserved for purulent exacerbations, with the exception of the presence of pneumonia and prophylaxis during ventilation. Steroids are recommended for all hospitalised patients and outpatients with a significant increase in breathlessness. Controlled oxygen therapy is central to management and is guided by arterial blood gas measurements. Noninvasive ventilation is the preferred management for patients with acidotic respiratory failure when the arterial pH is 7.25-7.35 despite the standard initial therapy. Prevention of exacerbations is aided by influenza vaccination and the institution of regular inhaled long-acting bronchodilators and inhaled corticosteroids. Summary Exacerbation of COPD is a common problem, which causes a considerable burden to the patient and the healthcare system. This article aims to give a structured overview of the different aspects of COPD exacerbations, including their classification, aetiology, pathophysiology, differential diagnosis, management and prevention. The ERS designates this educational activity for a maximum of 1 CME credit. For information on how to earn CME credits, see page 315.