Definition of Emphysema and smoking effects

Definition of Emphysema
By Mayo Clinic staff

Emphysema is a factor in the progression of chronic obstructive pulmonary disease (COPD), a condition that limits the flow of air when you breathe out. Emphysema occurs when the air sacs at the ends of your smallest air passages (bronchioles) are gradually destroyed. Smoking is the leading cause of emphysema.

As it worsens, emphysema turns the spherical air sacs — clustered like bunches of grapes — into large, irregular pockets with gaping holes in their inner walls. This reduces the number of air sacs and keeps some of the oxygen entering your lungs from reaching your bloodstream. In addition, the elastic fibers that hold open the small airways leading to the air sacs are slowly destroyed, so that they collapse when you breathe out, not letting the air in your lungs escape.

Airway obstruction, another feature of COPD, contributes to emphysema. The combination of emphysema and obstructed airways makes breathing increasingly difficult. Treatment often slows, but doesn't reverse, the process.