Emphysema. Gross clinical specimen of a sectioned lung affected by emphysema. The alveoli (air sacs), in which gaseous exchange takes place, become damaged, and the walls between them break down. This causes the formation of large spaces (black) in the lungs, which are less efficient at extracting oxygen from the air. The majority of cases of emphysema are caused by cigarette smoking. Symptoms include shortness of breath, which can develop into a serious lack of oxygen in the blood. This can lead to cyanosis (blue colouration due to lack of oxygen), and often to heart and respiratory failure. It is incurable. Treatment is aimed at stopping further damage.