There are two forms of bronchitis: acute bronchitis and chronic bronchitis. Acute bronchitis is a sudden inflammation of the bronchi, the larger air passages of the lungs. The illness can occur once or a number of times in a lifetime. Chronic bronchitis is a persistent, often debilitating, form of the disorder. Smoking is one of the principal culprits in cases of bronchitis and other disorders of the respiratory system. During respiration air is carried to the lungs via the air passages. Inflammation of the bronchi can impair the air supply to the tissue of the lung. Acute bronchitis is largely caused by viruses, and is usually preceded by a common cold. Viruses often attack the mucous membrane of the bronchi, which is a good source of food for bacteria, which means that bacterial infection can result. The symptoms of acute bronchitis are fever and coughing, and the production of sputum (phlegm) resulting from inflammation of the mucus; it contains pus if bacterial infection has set in. Breathing is usually slightly constricted, seriously so in the case of patients with a lung disease such as asthma or emphysema. With viral bronchitis persistent coughing can result, possibly with traces of blood in the sputum caused by the violence of the cough. Occasionally bronchitis is accompanied by vomiting, diarrhoea and haematuria (blood in the urine). Generally the patient recovers from viral bronchitis in a few weeks. In patients with healthy lungs a bacterial infection frequently clears up successfully without special treatment, but the diseases are more stubborn if the patient has unsound lungs. Complications of acute bronchitis are sinusitis and inflammation of the ear. In some children meningitis can result. If bronchitis descends to the lower air passages it can lead to pneumonia. A doctor can diagnose acute bronchitis by questioning the patient and by physical examination. If there is pus in the sputum a bacteriological examination can be arranged (examination under a microscope of bacteria in a culture). This is always done in serious cases. Then a blood test is carried out and the chest X-rayed to establish whether bronchitis has developed into another underlying lung complaint. To reduce the possibility of acute bronchitis, patients with an existing lung disease or other reduction of resistance can take a course of anti-influenza injections. It is a wise precaution for children, elderly people, and those in the higher risk categories to consult a doctor if acute bronchitis occurs. In the case of healthy adults this is not always necessary, but it is wise to inhale water vapour and to rest in bed to reduce painful symptoms. If coughing up sputum is difficult, the doctor can prescribe medicine to loosen the mucus, or drugs to suppress the cough. If there is pus in the sputum (bacterial infection) antibiotics will probably be prescribed, particularly for children at high risk. If there is serious constriction then medication to distend the air passages can help. Drawing off excess mucus and regular knocking of the chest are also helpful. Oxygen may possibly be used. In serious cases artifi-cal respiration may be necessary. Chronic bronchitis is a chronic inflam- mation of the bronchi. The disease is so common throughout the Western world that it has almost reached epidemic proportions, particularly in men over 40, but it also occurs in men and women under that age. With asthma and emphysema, bronchitis is one of the CARA group. The bronchial mucous membrane consists of mucus-producing cells and cells with cilia. If the mucous membrane is irritated, for example by smoke or smog, then the mucus-producing cells overproduce, resulting in a thick layer which screens the cells. The irritation leads to increasing paralysis of the ciliary cells, and the mucus can no longer be swept along. The longer the irritation from smoke persists, the more mucus is produced and the situation deteriorates. When the mucus layer has become so thick that air can no longer pass in the usual way, the patient coughs, and the mucus is moved in this way, but the patient finds it increasingly necessary to cough up mucus. The mucus (sputum) is usually white to yellow in colour, and fairly thick. Patients suffer more in winter because cold air also acts as a mucus-producing stimulus. In summer the patient suffers less, and sometimes not at all. If nothing is done to remove the causes of chronic bronchitis the symptoms remain the same or get worse. The mucus layer is an ideal place for bacteria, and their presence worsens the symptoms. Exacerbated chronic bronchitis is indistinguishable from acute bronchitis, and should be treated in the same way, with antibiotics. When chronic bronchitis has been present for a few years it can develop into emphysema. The doctor diagnoses chronic bronchitis by the characteristic symptoms and physical examination. Characteristic sounds can be heard with a stethoscope, because breathing in and out is no longer possible without resistance. Breathing in also takes longer. The doctor also checks for other sounds which could indicate the presence of other lung diseases with symptoms like those of chronic bronchitis – asthma and emphysema in particular. Emphysema usually results from a lung disease that has persisted for years. Because the three illnesses have so many common symptoms the concept of CARA was introduced some years ago as a common name for chronic bronchitis, asthma and emphysema. A chronic bronchitis sufferer can do a great deal to reduce discomfort and to make further sudden deterioration as unlikely as possible. In the first place he must be sure that the air he breathes is as pure as possible. If applicable the patient should stop smoking, and avoid rooms in which others are smoking. In winter he should protect himself against cold air, for example by breathing through a scarf. To keep the risk of infection as low as possible he should avoid contact with people with colds; in the winter this means avoiding functions attended by large numbers of people. Treatment prescribed by the doctor is based on the same principles. In some cases he will prescribe medicines to thin the mucus to enable it to be coughed up more easily. A doctor must be consulted, even if he prescribes nothing, so that he can establish whether the cough is masking another disorder. If the mucus becomes green, a visit to the doctor is also essential, because green or pus-containing mucus indicates a bacterial infection, which should be treated with antibiotics. Blood in the sputum can be harmless, but can also be the first sign of incipient lung disease, and only a doctor can make a diagnosis.