What is the role of chronic bronchitis in the pathogenesis of chronic obstructive pulmonary disease (COPD)?

Updated: Aug 15, 2019
  • Author: Paul Kleinschmidt, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

In this type, chronic bronchitis plays the major role. Chronic bronchitis is defined by excessive mucus production with airway obstruction and notable hyperplasia of mucus-producing glands, as depicted in the images below.

Chronic obstructive pulmonary disease (COPD). Hist Chronic obstructive pulmonary disease (COPD). Histopathology of chronic bronchitis showing hyperplasia of mucous glands and infiltration of the airway wall with inflammatory cells.
Chronic obstructive pulmonary disease (COPD). Hist Chronic obstructive pulmonary disease (COPD). Histopathology of chronic bronchitis showing hyperplasia of mucous glands and infiltration of the airway wall with inflammatory cells (high-powered view).

Damage to the endothelium impairs the mucociliary response that clears bacteria and mucus. Inflammation and secretions provide the obstructive component of chronic bronchitis. In contrast to emphysema, chronic bronchitis is associated with a relatively undamaged pulmonary capillary bed. Emphysema is present to a variable degree but usually is centrilobular rather than panlobular. The body responds by decreasing ventilation and increasing cardiac output. This V/Q mismatch results in rapid circulation in a poorly ventilated lung, leading to hypoxemia and polycythemia.

Eventually, hypercapnia and respiratory acidosis develop, leading to pulmonary artery vasoconstriction and cor pulmonale. With the ensuing hypoxemia, polycythemia, and increased CO2 retention, these patients have signs of right heart failure and are known as "blue bloaters."


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