BRONCHITIS

inflammation of all or part of the bronchial tree (the bronchi), through which air passes into the lungs. During the passage through the bronchi, microorganisms and other foreign bodies are removed from the air by tiny hairlike structures called cilia, which project from the cells that line the bronchial wall. These cilia exhibit a wavelike motion and sweep the foreign material upward toward the trachea and larynx. Because of this irritation a thick mucous and a thinner serous secretion are produced by glands in the bronchial wall and aid in the elimination of the foreign material. Such material and the secreted mucus stimulate nerve endings in the bronchial wall and initiate the cough reflex. Coughing then completes the expulsion of the foreign material and of the secreted mucus from the bronchial tree. All these factors together, often occurring in a vicious circle, cause an inflammation of the bronchi, which is called bronchitis. This can be caused either by a sudden and rapid attack upon the bronchi by infectious, physical, or chemical agents, resulting usually in a relatively brief disease, called acute bronchitis, or by long-standing, repetitive injury that results in protracted and often permanent damage to the bronchial mucosa, called chronic bronchitis. Acute bronchitis is defined by some as a symptom caused by any of a great number of agents and not as a specific disease. It is most frequently caused by viruses responsible for upper respiratory infections and is, therefore, often part of what is called the common cold. It is also a common sequel to influenza, whooping cough, and measles, as well as infections by pyogenic (pus-producing) organisms such as streptococci and staphylococci. Acute bronchitis can also be precipitated by a variety of physical and chemical agents, such as hot or toxic gases inhaled by fire victims; war gases; fumes of strong acids, ammonia, or organic solvents; and dusts containing silica and beryllium. Treatment has to be both symptomatic and specific. Steam inhalation, bronchodilators, and expectorants will usually relieve the symptoms, while specific chemotherapy (according to the sensitivity of the infecting organisms) and removal of or from the noxious physical or chemical agent will take care of the underlying cause. The course of the disease is commonly short, two to four days, if the specific treatment is successful. Untreated or unmitigated acute bronchitis may develop into chronic bronchitis. Chronic bronchitis refers to long-standing inflammation of the bronchial tree. The continuous injury to the lining has destroyed many of the cells, the cilia are absent, and the defense mechanism against invading foreign material is lost. Scarring has produced narrowing, rigidity, and distortion of the bronchial tubes, predisposing to chronic infection and hypersecretion of viscous mucous materials. A chronic, deep, and productive cough is the main symptom. It is difficult to suppress and actually should not be suppressed, since the abundant secretion has to be eliminated to avoid the ever-present danger of severe superimposed infection. Excessive and prolonged tobacco smoking can be one of the causes of chronic bronchitis and is certainly one of the most aggravating factors of chronic bronchitis. Chronic heart disease may produce congestion of blood in the lungs that obstructs or collapses the bronchi by exerting pressure on them. Infections of the sinus cavities may provide a reservoir of available pathogenic microorganisms, which can continually reinfect the lungs. Damaged bronchi are ideal sites for harbouring infections and accumulating excess fluids and secreted mucus. Sudden changes in temperature, cold and damp climate, and dusty surroundings increase the severity of the symptoms. Chronic bronchitis predisposes to the development of pulmonary fibrosis and emphysema. Episodes of acute bronchitis and pneumonia are frequent, because the respiratory tract is more susceptible to invasion by pathogenic microorganisms. Because the damage to the bronchial tree is largely irreversible, the treatment has to be symptomatic, consisting of expectorants and bronchodilators. Occasionally, drugs to suppress paroxysmal coughing may be necessary but must be used sparingly because they can be addictive and because expectoration is necessary. Of primary importance is the prevention of superimposed infections either by careful watching for early signs or by using prophylactic antibiotics. Adjusting the patient's living and working conditions to the largely irreversible condition is an essential factor in treatment.