It is a condition clinically defined as persistent cough with expectoration for at least 3 months to the year. Cough is caused by oversecretion of mucus.
-Most Common responsible factors are cigarette smoking and atmospheric pollution. As it impairs ciliary movements, Inhibits function of alveolar macrophages and leads to hypertrophy and hyperplasia of mucus-secreting glands.
Grossly- The bronchial wall is thickened hyperaemic oedematous, Lumina may contain mucus plug.
Microscopically- histologically it is defined by increased Reid index, which is the ratio between the thickness of the submucosal mucus gland in the cartilage containing large airway to that of the total bronchial wall. The increase in thickness can be assessed by a micrometer lens. Bronchial epithelium show squamous metaplasia and dysplasia and chronic inflammatory cell infiltrate.