Notes on Exacerbations

• Greatest risk factor is the history of previous exacerbations
• Progression through GOLD stages increases exacerbation risk
• Exacerbations worsen survival and impair lung function
• Infective exacerbations still the most common type of exacerbation, bacteria marginally more common than viruses (54% vs 48%), patients with infectious exacerbations stayed longer in hospital and had worse decline in lung function
• Sputum purulence is associated with culture of pathogenic bacteria, in comparison to mucoid sputum.

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Viral model of COPD exacerbation

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• Give patients with COPD rhinovirus and measure lung function, sputum neutrophils, bacterial counts etc in comparison to non-obstructed control patients. 
• Rhinovirus infection worsened breathlessness, post bronchodilator peak flows, sputum neutrophilia and caused secondary increase in bacterial colonisation and the degradation of antimicrobial peptides (see below)

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