Chronic bronchitis is an inflammation, or irritation, of the airways in the lungs. Airways are tubes in your lungs that air passes through. They are also called bronchial tubes. When the airways are irritated, thick mucus forms in the tubes. The mucus plugs up the tubes and makes it hard for you to get air into your lungs.
Cigarette smoking is the main cause of chronic bronchitis.
When tobacco smoke is breathed into the lungs, it irritates the airways which then produce mucus. People who have been exposed for a long time to things that irritate their lungs, like chemical fumes, dust and other substances, can also get chronic bronchitis. If your doctor thinks you have chronic bronchitis, you may be tested to find out if your lungs are damaged. You might have a pulmonary function test to see how well your lungs are working. With this test, you breathe into a machine that measures the amount of air in your lungs.