emphysema
(em-fi-sE-ma)
A common type of chronic obstructive pulmonary disease (COPD). It occurs when the linings of the air sacs within the lungs are damaged and air pockets develop as a result. Once the air becomes trapped, the lungs slowly increase in size and lose their elasticity, which makes breathing difficult because the lungs cannot exhale completely. See the COPD page for additional information.