Emphysema

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

Signs and symptoms

Emphysema is characterised by loss of elasticity of the lung tissue; destruction of structures supporting the alveoli; and destruction of capillaries feeding the alveoli. The result is that the small airways collapse during expiration, leading to an obstructive form of lung disease (air is trapped in the lungs in obstructive lung diseases). Features are: shortness of breath on exertion--particularly when climbing stairs or inclines (and later at rest), hyperventilation and an expanded chest. As emphysema progresses, clubbing of the fingers may be observed, a feature of longstanding hypoxia.

Emphysema patients are sometimes referred to as "pink puffers". This is because emphysema sufferers may hyperventilate to maintain adequate blood oxygen levels. Hyperventilation explains why emphysema patients do not appear cyanotic as chronic bronchitis (another COPD disorder) sufferers often do; hence they are "pink" puffers (adequate oxygen levels in the blood) and not "blue" bloaters (cyanosis; inadequate oxygen in the blood).

Diagnosis

Diagnosis is by spirometry (lung function testing), including diffusion testing. Other investigations might include X-rays, high resolution spiral chest CT-scan, bronchoscopy (when other lung disease is suspected, including malignancy), blood tests, pulse oximetry and arterial blood gas sampling.

Pathophysiology

The scientific definition of emphysema is:

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

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.

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 lose carbon dioxide. The activity of another molecule called alpha 1-antitrypsin normally neutralizes the destructive action of one of these damaging molecules.

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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