Emphysema. Coloured scanning electron micrograph (SEM) of human lung tissue affected by emphysema. Emphysema is a disease in which the tiny air sacs (alveoli) of the lung become enlarged and the walls separating them are damaged. Surface area for gaseous exchange is reduced, restricting oxygen uptake. This may cause breathlessness, bluish skin, and heart or respiratory failure. Occurrence of emphysema is strongly associated with smoking. Treatment of emphysema is with drugs and the cessation of smoking. Magnification: x150 when printed 10 centimetres wide.