acute exacerbation of chronic obstructive pulmonary disease acute exacerbation of chronic obstructive pulmonary disease 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. acute exacerbation of chronic obstructive pulmonary diseaseother namesacute exacerbations of chronic bronchitis (aecb)chest x-ray in a case of copd exacerbation where a nasopharyngeal swab detected haemophilus influenzae, with right-sided opacitiesspecialtyrespirology, emergency medicine 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. causes 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: respiratory infection, being responsible for approximately half of copd exacerbations. approximately half of these are due to viral infections and another half appears to be caused by bacterial infections. common bacterial pathogens of acute exacerbations include haemophilus influenzae, streptococcus pneumoniae and moraxella catarrhalis. less common bacterial pathogens include chlamydia pneumoniae and mrsa. pathogens seen more frequently in patients with impaired lung function (fev<35% of predicted) include haemophilus parainfluenzae (after repeated use of antibiotics), mycoplasma pneumoniae and gram-negative, opportunistic pathogens like pseudomonas aeruginosa and klebsiella pneumoniae. allergens, e.g., pollens, wood or cigarette smoke, pollution toxins, including a variety of different chemicals air pollution failing to follow a drug therapy program, e.g. improper use of an inhaler in one-third of all copd exacerbation cases, the cause cannot be identified. diagnosis