Bronchitis

The term bronchitis refers to a self-limited condition caused by infection and/or inflammation of the bronchial tree. Bronchi are tube-like structures that serve to communicate oxygenated air to the lung during inhalation and remove debris and products of metabolism (e.g., carbon dioxide) during exhalation. The origin of the bronchial tree is the trachea (main breathing tube), which branches into the right and left main stem bronchi. These main stem bronchi repeatedly [Page 313]branch into smaller and smaller bronchi, allowing for dispersion of oxygenated air to the periphery of the lung. Some experts have made the analogy of an upside-down tree trunk with branches to the branching of the bronchi within the human lung.

Bronchitis results from inflammation and/or infection of the epithelial cell lining of the bronchial tree by viruses, bacteria, or following inhalation of irritant gases such as those associated with home fires, mixing of bleach and ammonia in a closed space, chemical fires, and so forth. These infected epithelial cells frequently become detached from the surface of the lining of the bronchi and may be coughed up by the patient in the form of sputum (phlegm).

Symptoms of bronchitis include cough, which may be a nonproductive (dry) cough or a cough productive of sputum (phlegm); mild to moderate chest pain (behind the breastbone and noted particularly with repeated coughing); and rarely, mild shortness of breath with or without wheezing.

Bronchitis may be acute or chronic. It has been estimated that 10 percent of nonsmoking adults will experience at least one episode of bronchitis per year. Tobacco smokers are at increased risk to develop repeated episodes of bronchitis and, with long-term smoking, a condition known as chronic bronchitis may develop. The diagnosis of chronic bronchitis is made when cough and sputum (phlegm) production occurs on most days of the month for at least three months of the year, for two consecutive years.

During the early days of acute bronchitis, symptoms may be indistinguishable from any other respiratory tract infection. The duration of the cough associated with acute bronchitis persists for at least five days and may last for as long as three to four weeks. The differential diagnosis of acute bronchitis includes postnasal drip, exacerbation of asthma, or chronic obstructive pulmonary disease (COPD) as well as other types of pulmonary disease including influenza or pneumonia.

A large number of viruses have been shown to cause acute bronchitis; in addition, a number of bacterial species may cause bronchitis. Treatment with antibiotics is generally not recommended and will only be effective when cultures or testing for antibodies has identified specific bacterial causes of bronchitis; specific antiviral medications may be indicated for the treatment of bronchitis caused by the influenza virus (antiviral therapies have been shown to reduce the length of symptoms and prompt faster return to usual activities).