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 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).
Because bronchitis is typically self-limited, the physical examination of the patient with bronchitis should show cough but no fever, no evidence of fast breathing, no evidence of fast heart rate, and no difficulty with oxygenation. Deviation from this presentation may occur if the patient with bronchitis is also experiencing an exacerbation of an underlying respiratory condition such as asthma or COPD.
Diagnostic studies such as chest X-ray, arterial blood gas, and sputum culture are typically not warranted. Only when the physician is concerned that the symptoms may be caused by an alternative diagnosis should these studies be obtained. To do so otherwise has not been proven to be cost-effective.
Supportive care is also traditionally offered because this condition is self-limited. Supportive care consists of encouraging the patient to expand fluid intake, as needed use of analgesics such as acetaminophen, ibuprofen, or naproxen (when not contraindicated), and rest. Cough suppressants are not routinely recommended as prospective studies have shown no benefit when these agents were compared to placebo. Antibiotics, mucolytics, and bronchodilators (breathing medications) should not be routinely administered as they have not been proven to alter the time to resolution of symptoms or return to normal activities.
Exceptions to the above include cases of bronchitis occurring in patients with underlying lung diseases which may be exacerbated by the acute bronchitis. Examples of such underlying lung conditions include but are not limited to asthma, COPD, pulmonary fibrosis, and sarcoidosis. In such cases, consideration may be given to the use of bronchodilators, corticosteroids, antibiotics, and cough suppressants, on a case-by-case basis. Input from a pulmonologist may be helpful.
In the event that a patient suspected of having uncomplicated, acute bronchitis does not respond to supportive care within the usual time frame and has protracted symptoms, consideration should be given to consultation with a pulmonologist and performance of a chest X-ray, blood tests, lung function testing, and possibly cultures for microorganisms. Conditions that may masquerade as uncomplicated bronchitis include pertussis (whooping cough), asthma, COPD, lung cancer, pneumonia, inhaled foreign body, or infectious processes including but not limited to tuberculosis, fungal infection, or other malignancy. If one of these conditions is diagnosed following appropriate studies, definitive therapy should be applied.
In recent years, development of evidence-based guidelines has become common practice. These guidelines are formulated by groups of content experts following an exhaustive review of prospective, controlled clinical studies of patients with the disease under consideration. The evidence supporting application of or withholding of treatment is rated according to the level of evidence from the literature that supports the recommendation. The American College of Chest Physicians has published two sets of evidence-based guidelines on acute bronchitis, the first in 2001 and the second in 2006. These guidelines should be consulted for specific levels of recommendation of the treatments discussed herein.
Asthma; Chronic Obstructive Pulmonary Disease (COPD); Pneumonia; Pulmonology.
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