Emphysema

Emphysema is a chronic lung disease. It is often caused by exposure to toxic chemicals or long-term exposure to tobacco smoke.

Pathophysiology

The scientific definition of emphysema is:

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:"Permanent destructive enlargement of the airspaces distal to the terminal bronchioles without obvious fibrosis".

Related Topics:
Distal - Fibrosis

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Hence, the definite diagnosis is made by a pathologist. However, we can easily ascertain clinical diagnosis by history, clinical examination, chest radiography and lung function tests.

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In normal breathing, air is drawn in through the bronchial passages and down into the increasingly fine network of tubing in the lungs called the alveoli, which are many thousands of tiny sacs surrounded by capillaries. These absorb the oxygen and transfer it into the blood. When toxins such as smoke are breathed into the lungs, the particles are trapped by the hairs and cannot be exhaled, leading to a localised inflammatory response. Chemicals released during the inflammatory response (trypsin, elastase, etc.) are released and begin breaking down the walls of alveoli. This leads to fewer but larger alveoli, with a decreased surface area and a decreased ability to take up oxygen and carbon dioxide. The activity of another molecule called alpha 1-antitrypsin normally neutralizes the destructive action of one of these damaging molecules.

Related Topics:
Bronchial passage - Alveoli - Oxygen - Blood - Inflammatory

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After a prolonged period, hyperventilation becomes inadequate to maintain high enough oxygen levels in the blood, and the body compensates by vasoconstricting appropriate vessels. This leads to pulmonary hypertension. This leads to enlargement and increased strain on the right side of the heart, which in turn leads to peripheral edema (swelling of the peripherals) as blood gets backed up in the systemic circulation, causing fluid to leave the circulatory system and accumulate in the tissues.

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Emphysema occurs in a higher proportion in patient with decreased alpha 1-antitrypsin (A1AT) levels (alpha 1-antitrypsin deficiency, A1AD). In A1AD, inflammatory enzymes (such as elastase) are able to destroy the alveolar tissue (the elastin fibre, for example). Most A1AD patients do not develop clinically significant emphysema, but smoking and severely decreased A1AT levels (10-15%) can cause emphysema at a young age. In all, A1AD causes about 2% of all emphysema.

Related Topics:
Alpha 1-antitrypsin - Alpha 1-antitrypsin deficiency - Elastase - Alveolar - Tissue - Elastin

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