Destruction of the smallest branches of the air passages of the lungs, the broncheoli and the alveoli, caused by abnormal dilation and loss of elasticity, and associated with destruction of the wall of the alveoli. The condition is common in later life, although it is usually not severe. Oxygen and carbon dioxide exchange takes place in the alveoli; oxygen is extracted from the inhaled air and carbon dioxide removed from the blood. The lung has about 300 million alveoli, and thus a large reserve capacity, meaning that large numbers can be damaged before problems are caused. The commonest cause of emphysema is chronic bronchitis, a disorder with which it is associated in the CARA group. Chronic bronchitis, a gradual inflammation of the air passages, causes persistent accumulation of firm mucus in the air passages. Air can be inhaled, but is exhaled only with difficulty: the alveoli are dilated, the extra pressure inflates them, the walls are damaged and emphysema begins. The condition can also be caused by external stimuli, such as smoking, and there are less common causes such as playing the trumpet and glass blowing. Smoking causes emphysema only in ‘sensitive’ smokers; with others the lung abnormality disappears when they stop smoking. Emphysema in smokers is caused by the ‘ventilation effect’: smoke causes dilation of the air passages, behind which air accumulates. Emphysema can also result from aging of the tissue as the patient grows older, but this form is not usually severe, and causes few problems. The main, in fact the sole, symptom of emphysema is shortness of breath, caused by the lungs’ decreased ability to absorb oxygen. Other symptoms of emphysema are usually associated with other conditions such as chronic bronchitis, with signs like coughing and bringing up green sputum. The condition is always progressive, at best stable. Damage to the alveoli is irreversible, and further inflammation can cause further damage. A serious complication is enlargement of the heart and deficient functioning of the right ventricle, caused by its being overworked as a result of the constriction and decay of capillaries in the lungs, which can lead finally to heart failure (cardiac decompensation). The presence of emphysema is indicated by shortness of breath, enlargement of the chest and poor lung movement when breathing. Diagnosis may be confirmed by a chest X-ray, which shows excess air in the lungs, and measurement of lung function, showing that too much air remains in the lungs on breathing out; air in the alveoli is inadequately refreshed.

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