Emphysema. Three-dimensional computed tomography (CT) scan of the lungs, showing advanced emphysema of the right lung (left). Emphysema is a disease in which the tiny air sacs (alveoli) of the lung become enlarged and the walls separating them are damaged. It is strongly associated with smoking. Damaged areas (upper and lower left) are more transparent. The reduced surface area for gaseous exchange restricts oxygen uptake. This may cause breathlessness, bluish skin, and heart or respiratory failure. Treatment is with drugs and the cessation of smoking. For several CT scans of these lungs, see images M150/223-227.