An acute exacerbation of chronic obstructive pulmonary disease, or acute exacerbations of chronic bronchitis (AECB), is a sudden worsening of chronic obstructive pulmonary disease (COPD) symptoms including shortness of breath, quantity and color of phlegm that typically lasts for several days. It may be triggered by an infection with bacteria or viruses or by environmental pollutants. Typically, infections cause 75% or more of the exacerbations; bacteria can roughly be found in 25% of cases, viruses in another 25%, and both viruses and bacteria in another 25%. Airway inflammation is increased during the exacerbation resulting in increased hyperinflation, reduced expiratory air flow and decreased gas exchange.Exacerbations can be classified as mild, moderate, and severe. As COPD progresses, exacerbations tend to become more frequent, the average being about three episodes per year. Signs and symptoms
An acute exacerbation of COPD is associated with increased frequency and severity of coughing. It is often accompanied by worsened chest congestion and discomfort. Shortness of breath and wheezing are present in many cases. Exacerbations may be accompanied by increased amount of cough and sputum productions, and a change in appearance of sputum. An abrupt worsening in COPD symptoms may cause rupture of the airways in the lungs, which in turn may cause a spontaneous pneumothorax.In infection, there is often weakness, fever and chills. If due to a bacterial infection, the sputum may be slightly streaked with blood and coloured yellow or green.
Hemoptysis may also indicate other, potentially fatal, medical conditions.A history of exposure to potential causes and evaluation of symptoms may help in revealing the cause the exacerbation, which helps in choosing the best treatment. A sputum culture can specify which strain is causing a bacterial AECB. An early morning sample is preferred.E-nose showed the ability to smell the cause of the exacerbation.The definition of a COPD exacerbation is commonly described as "lost in translation", meaning that there is no universally accepted standard with regard to defining an acute exacerbation of COPD. 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. Prevention
Acute exacerbations can be partially prevented. Some infections can be prevented by vaccination against pathogens such as influenza and Streptococcus pneumoniae. 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. Other methods of prevention include:

Smoking cessation and avoiding dust, passive smoking, and other inhaled irritants
Yearly influenza and 5-year pneumococcal vaccinations
Regular exercise, appropriate rest, and healthy nutrition
Avoiding people currently infected with e.g. cold and influenza
Maintaining good fluid intake and humidifying the home, in order to help reduce the formation of thick sputum and chest congestion. Treatment
Based on the severity different treatments may be used. Mild exacerbations are treated with short acting bronchodilators (SABDs).