If you have chronic bronchitis:

• the cells lining the inside of the bronchi are continuously inflamed
• the airways in your lungs have become narrow and partly clogged with mucus

The bronchi are air passages connecting the windpipe (trachea) with the sacs of the lung (alveoli), where oxygen is taken up by the blood. Bronchitis is an inflammation of the bronchi. This inflammation causes excessive production of mucus and swelling of the bronchial walls. Airflow into and out of the lungs is obstructed.

With chronic bronchitis, the mucus cannot be cleared. Instead of helping to clean the lungs, it causes obstruction in the airways. The mucus is thicker and more difficult to cough up. This provides a means for bacteria to settle in the lower airways and increases the risk of infection.

Chronic bronchitis is caused mainly by cigarette smoke. It is characterized by:

• persistent cough
• production of mucus