Bronchitis

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Bronchitis is an inflammation of the lining of the air tubes of the lungs, the bronchi. Acute bronchitis usually follows a cold, a sore throat or influenza, most often in winter. It is very common as a winter flare-up in people with chronic bronchitis. It may also be brought on by breathing a polluted atmosphere or by smoking.

In most cases the condition settles within a week or two, but there is always the risk, especially in cigarette smokers, that the condition may progress to chronic bronchitis with inevitable winter flare-ups.

The lining cells of the air tubes in healthy lungs are tall (columnar). The surfaces nearest the inside of the tube are covered with fine hairs (cilia), which move together in a manner similar to the effect of wind blowing across a field of ripe corn.

The hair movement acts to carry dust and other foreign material upwards and away from the deeper parts of the lungs. This is one of the bodyâ€™s protective processes and, without it, a good deal of unwanted material in the air we breathe would find its way into the delicate air sacs.

Chemical irritants such as cigarette smoke or other environmental or industrial pollutants damage the ciliated cells, eventually destroying the action of the hairs altogether. They also cause the glands in the air passages to produce too much mucus. Because the cilia are not working properly, this mucus accumulates in the tubes. Coughing can usually clear this material. Irritants also interfere with the white blood cell mechanism that combats infection in the lungs. This is the condition of chronic bronchitis.

Coughing often becomes less effective when the circular muscles in the wall of the bronchial tubes contract, so causing the tubes to narrow. This is called bronchospasm and causes wheezing, another sign of chronic bronchitis.

Chronic bronchitis is one of the forms of chronic obstructive lung (pulmonary) disease (COPD).In the early stages chronic bronchitis may be a comparatively mild disease. But, with time and continued abuse, it is likely to progress to chronic obstructive airway disease (COAD), in which large numbers of the tiny lung air sacs break down to form a smaller number of larger air spaces. The total surface area now available for transferring oxygen to the blood is much less, so you become short of oxygen. In addition, the smaller bronchial tubes become inflamed, narrowed and partially blocked by mucus. The result is increased breathlessness.

Smoking is especially dangerous if you have a persistent, productive cough. Chronic bronchitis and other forms of COPD affects 18 per cent of male smokers and 14 per cent of female smokers.

Chronic bronchitis and emphysema may so restrict the movement of oxygen from the atmosphere to your blood that the blood does not get enough. Blood without enough oxygen is blue, in contrast to its usual bright red colour, and gives a bluish tinge to the skin. This is called cyanosis.At the same time, these diseases may greatly increase the resistance to blood pumped through the lungs by the right side of the heart. This causes the muscle of the right heart to enlarge, and this extra pumping power may meet the need for a while.

Eventually, however, the right side of the heart may fail and be unable to maintain enough blood flow from the rest of the body, via the veins. The result is a general increase of fluid in the tissues (oedema), characteristic of right heart failure.