EMPHYSEMA

also called pulmonary emphysema, abnormal distension of the lungs with air. The air ducts and the air sacs, or alveoli, are distended and there is destruction of the partitions between alveoli and loss of alveoli. The exact cause and mechanism producing emphysema are not definitely known. It is most commonly associated with cigarette smoking and chronic bronchitis. Lungs affected by emphysema show loss or degeneration of elastic tissue, disappearance of capillary walls, and breakdown of the alveolar walls. The air sac first stretches and then tends to disintegrate. The lung therefore becomes filled with large pools of air, and loss of elastic support around small airways, or associated loss of small airways themselves, severely interferes with expiration. The lung takes on a lace network, and the capillaries are greatly diminished, leaving the lung tissue dry and pale. Some emphysema patients show a deficiency in a substance called antitrypsin; this substance normally counteracts the enzyme trypsin produced by bacteria that tends to degenerate tissue. An insufficient amount of antitrypsin gives even harmless bacteria an advantage and allows for possibly greater destruction. The clinical manifestations are constant. There is severe breathlessness upon exertion, loss of weight, and swelling in the extremities; the skin takes on a bluish colour from lack of sufficient gas exchange; there is tightness in the chest; and the affected person wheezes and has an intolerance to sudden cold or smoky atmospheres. The chest may be noted to be held in the inspiratory position. The disease is one of the most common and crippling of respiratory diseases. There is no evidence that lung tissue destroyed by emphysema can be repaired. Bullous emphysema is a variety of emphysema in which the distended alveoli actually form large air cysts on one or both of the lungs and occasionally rupture, causing lung collapse. When the blisters cause reduced heart or lung efficiency, they are sometimes removed by surgery.