Chronic bronchitis is defined clinically as persistent cough with sputum production for at least 3 months in at least 2 consecutive years.

The classic chronic bronchitis patient is a "blue bloater" - cyanotic due to a decrease in sufficient amounts of oxygen reaching the blood) , obese, and edematous (cor pulmonale) . Patients suffering  from emphysema are referred to as "pink puffers". Are "pink puffers" more breathless than "blue bloaters"?Br Med J (Clin Res Ed). 1983 Jan 15;286(6360):179-82

 Microscopic features:  (click on the image)

1. Hyperemia and edema of mucus membranes of the lung.

2. Mucinous secretions or casts filling airways.

3. Increase in size of mucous glands

4. Bronchial or bronchiolar mucous plugging, inflammation and fibrosis.

5. Squamous metaplasia or dysplasia of bronchial epithelium.

6. Smokers with both symptoms of chronic bronchitis and chronic airflow limitation have an increased number of goblet cells and inflammatory cells in the epithelium of peripheral airways.

Reid Index: (click on the image) In chronic bronchitis there is enlargement of mucous secreting glands in the trachea and bronchi. The ratio of the thickness of the mucous gland layer to the thickness of the wall between the epithelium and cartilage is known as the Reid Index. A normal Reid index is less than 0.4 and is increased in chronic bronchitis.

Chronic irritation of the airways by the inhaled substances, especially tobacco smoke, is the dominant factor in the pathogenesis of chronic bronchitis. These irritants cause bronchitis by eliciting:

(i) Hypersecretion of mucus

(ii) Subsequent hypertrophy of mucous glands

(iii) Goblet cell metaplasia in bronchial epithelium

(iv) Bronchiolitis

Infections are a secondary factor that maintain and promote the injury initiated by smoking.

Exacerbations and death follow infection with S. pneumoniae or H. influenzae.

Death may also result from cor pulmonale or from apnea .