Chronic Bronchitis is defined clinically as hypersecretion of mucus and recurrent episode of productive cough for a period of 3 months per year at least two consecutive years.
First there is glandular hypertrophy. Mucous gland hypertrophy and hyperplasia from chronic irritations cause excessive mucus production. The excessive mucus and impaired ciliary movement associated with chronic bronchitis increase susceptibility to infection. As infection progress, the epithelial cells produce a mucopurulent exudates in the lumen or the disease may progress to ulceration and destruction of the bronchial wall. The peribronchial fibrosis and the presence of granulation tissue result in stenosis and airway obstruction.
Second the bronchial wall tissue changes, mucosal ocdema and excessive mucus production, all increase airway resistance in persons with chronic bronchitis. Excess mucus may also cause bronchospasm.
Third the pathophysiologic changes may impair the ability of lungs to exchange 0, and CO, leading to ventilation-perfusion mismatching at the alveolar-capillary membrane. Obstructed airways may lead to atelectasis which further diminishes the surface are a available for respiration. Fourth the right ventricular decompensation or corpulmonale may result.