Bronchitis is inflammation of the mucous membranes of the bronchi, the airways that carry airflow from the trachea into the lungs. Bronchitis can be classified into two categories, acute and chronic, each of which has unique etiologies, pathologies, and therapies.
Acute bronchitis is characterized by the development of a cough, with or without the production of sputum, mucus that is expectorated (coughed up) from the respiratory tract. Acute bronchitis often occurs during the course of an acute viral illness such as the common cold or influenza. Viruses cause about 90% of cases of acute bronchitis while bacteria account for less than 10%.
Chronic bronchitis, a type of chronic obstructive pulmonary disease, is characterized by the presence of a productive cough that lasts for 3 months or more per year for at least 2 years. Chronic bronchitis most often develops due to recurrent injury to the airways caused by inhaled irritants. Cigarette smoking is the most common cause, followed by air pollution and occupational exposure to irritants, and cold air.
Acute bronchitis is most often caused by viruses that infect the epithelium of the bronchi, resulting in inflammation and increased secretion of mucus. Cough, a common symptom of acute bronchitis, develops in an attempt to expel the excess mucus from the lungs. Other common symptoms include sore throat, runny nose, nasal congestion (coryza), low-grade fever, pleurisy, malaise, and the production of sputum. As most cases of acute bronchitis are caused by viruses, antibiotics should not be used since they are only effective against bacteria. Using antibiotics in patients who do not have bacterial infections promotes the development of antibiotic-resistant bacteria, which may lead to greater morbidity and mortality. Antibiotics should only be prescribed if microscopic examination of Gram stained sputum shows large numbers of bacteria present. Other symptoms may include wheezing and shortness of breath, especially upon exertion. The cough is often worse soon after awakening, and the sputum produced may have a yellow or green color and may be streaked with blood.
Most cases of chronic bronchitis are caused by smoking cigarettes or other forms of tobacco. Chronic inhalation of irritating fumes or dust from occupational exposure or air pollution may also be causative. About 5% of the population has chronic bronchitis, and it is two times more common in males than females.
Chronic bronchitis is treated symptomatically. Inflammation and edema of the respiratory epithelium may be reduced with inhaled corticosteroids. Wheezing and shortness of breath can be treated by reducing bronchospasm (reversible narrowing of smaller bronchi due to constriction of the smooth muscle) with bronchodilators such as inhaled β-Adrenergic agonists (e.g., albuterol) and inhaled anticholinergics (e.g., ipratropium bromide). Hypoxemia, too little oxygen in the blood, can be treated with supplemental oxygen.
The most effective method of preventing chronic bronchitis and other forms of COPD is to avoid smoking cigarettes and other forms of tobacco.
On pulmonary tests, a bronchitic (bronchitis) may present a decreased FEV1 and FEV1/FVC. However, unlike the other common obstructive disorders, asthma and emphysema, bronchitis rarely causes a high residual volume. This is because the air flow obstruction found in bronchitis is due to increased resistance, which does not generally cause the airways to collapse prematurely and trap air in the lungs.
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