
Emphysema is a chronic lung disease caused by damage to the alveoli, the tiny air sacs in the lung where the exchange of oxygen and carbon dioxide takes place. With emphysema, damage to the alveoli results in air becoming trapped, causing them to expand and rupture.
Damage to alveoli, and the resultant compromise in air exchange results in a decreased level of oxygen in the blood (hypoxemia) combined with an increased level of carbon dioxide in the blood (hypercapnia).