Emphysema is a disease of the lungs that usually develops after many years of smoking. Both chronic bronchitis and emphysema belong to a group of lung diseases known as chronic obstructive pulmonary disease (COPD). Once it develops, emphysema can’t be reversed. This is why not smoking or stopping smoking is very important.
Emphysema is a condition that involves damage to the walls of the air sacs (alveoli) of the lung. Alveoli are small, thin-walled, very fragile air sacs located in clusters at the end of the bronchial tubes deep inside the lungs. There are about 300 million alveoli in normal lungs. As you breathe in air, the alveoli stretch, drawing oxygen in and transporting it to the blood. When you exhale, the alveoli shrink, forcing carbon dioxide out of the body.
When emphysema develops, the alveoli and lung tissue are destroyed. With this damage, the alveoli cannot support the bronchial tubes. The tubes collapse and cause an “obstruction” (a blockage), which traps air inside the lungs. Too much air trapped in the lungs can give some patients a barrel-chested appearance. Also, because there are fewer alveoli, less oxygen will be able to move into the bloodstream.