Chronic bronchitis

Last revised by Daniel J Bell on 18 Aug 2021

Chronic bronchitis is most commonly defined as the presence of productive cough for three months in two successive years in a patient in whom other causes of chronic cough, such as tuberculosis, lung cancer and heart failure, have been excluded. It can be an important pathological component of chronic obstructive pulmonary disease (COPD), although it is often considered as a distinct phenotype.

Persistent productive cough for many years without any additional respiratory impairments, but eventually dyspnea on exertion develops. After some time other signs of COPD may appear, including hypercapnia, hypoxemia and mild cyanosis. Long-standing severe chronic bronchitis commonly leads to cor pulmonale and heart failure 4.

Chronic bronchitis most often results from overproduction and hypersecretion of mucus by goblet cells. The mechanism is not entirely clear but is linked to both hypertrophy of submucosal glands (Reid index) and increased number of goblet cells which are thought to be the protective reaction to tobacco smoke or other pollutants 4. This can, in turn, lead to worsening airflow obstruction by luminal obstruction of small airways, epithelial remodeling, and alteration of airway surface tension predisposing to collapse. 

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