Bronchitis
Bronchitis is inflammation of the bronchi (medium-size airways) in the lungs. Acute bronchitis is usually caused by viruses or bacteria and may last several days or weeks. Chronic bronchitis is not necessarily caused by infection and is generally part of a syndrome called COPD (chronic obstructive pulmonary disease); it is defined clinically as a persistent cough that produces sputum (phlegm), for at least three months in two consecutive years. The remainder of this article deals with acute bronchitis only.
Acute bronchitis is characterized by cough and sputum (phlegm) production and symptoms related to the obstruction of the airways by the inflamed airways and the phlegm, such as shortness of breath and wheezing. Diagnosis is by clinical examination and sometimes microbiological examination of the phlegm. Treatment may be with antibiotics (if a bacterial infection is suspected), bronchodilators (to relieve breathlessness) and other treatments.
Acute bronchitis often follows a cold or infection. The earliest clinical feature of bronchitis is increased secretion of mucus by submucosal glands of the trachea and bronchi. Damage caused by irritation of the airways leads to inflammation and infiltration of the lung tissue by neutrophils. The neutrophils release substances that promote mucosal hypersecretion.
Neutrophils infiltrate the lung tissue, aided by damage to the airways caused by irritation.
Damage caused by irritation of the airways leads to inflammation and leads to neutrophils being present
Mucosal hypersecretion is promoted by a substance released by neutrophils
Further obstruction to the airways is caused by more goblet cells in the small airways. This is typical of chronic bronchitis
Although infection is not the reason or cause of chronic bronchitis it is seen to aid in sustaining the bronchitis.