[3] As COPD progresses, exacerbations tend to become more frequent, the average being about three episodes per year.

If due to a bacterial infection, the sputum may be slightly streaked with blood and coloured yellow or green.

[5] As the lungs tend to be vulnerable organs due to their exposure to harmful particles in the air, several things can cause an acute exacerbation of COPD: In one-third of all COPD exacerbation cases, the cause cannot be identified.

[citation needed] The diagnostic criteria for acute exacerbation of COPD generally include a production of sputum that is purulent[7] and may be thicker[5] than usual, but without evidence of pneumonia (which involves mainly the alveoli rather than the bronchi).

[7] A chest X-ray is usually performed on people with fever and, especially, hemoptysis (blood in the sputum), to rule out pneumonia and get information on the severity of the exacerbation.

Many organizations consider it a priority to create such a standard, as it would be a major step forward in the diagnosis and quality of treatment of COPD.

Regular medication use can prevent some COPD exacerbations; long acting beta-adrenoceptor agonists (LABAs), long-acting anticholinergics, inhaled corticosteroids and low-dose theophylline have all been shown to reduce the frequency of COPD exacerbations.

In the prehospital environment those given high flow O2 rather than titrating their O2 saturations to 88% to 92% had worse outcomes.

Patients may watch for symptoms, such as shortness of breath, change in character or amount of mucus, and start self-treatment as discussed with a health care provider.