Bronchitis

BRONCHITIS

The term "bronchitis" refers to the inflammation of medium-sized and large airways in the lung (bronchi). Bronchitis is distinguished from bronchiolitis (inflammation of small airways that lack cartilage and mucus-secreting glands in their walls) and from bronchiectasis (permanent dilation and destruction of bronchi associated with chronic cough productive of purulent sputum). Although bronchial asthma is a chronic inflammatory airway disease, it is not considered under the heading of bronchitis.

Acute bronchitis is usually an infectious disease caused by viruses (influenza A and B, parainfluenza, the common cold viruses [rhinovirus and coronavirus], adenovirus, and respiratory syncytial virus). Infrequently, acute bronchitis is caused by inhalation of toxic gases and products of combustion or by aspiration of foreign material. Acute infectious bronchitis is a self-limited illness characterized by cough, sputum production, and, in most cases, symptoms of an upper respiratory tract infection (sore throat, and nose and sinus congestion). Inflammation of the trachea usually occurs together with inflammation of the bronchi, so the term "tracheobronchitis" is sometimes used. The majority of cases occur during the winter. In most cases, symptoms clear spontaneously within one week. In about 10 percent of cases, acute bronchitis can be traced to infection by nonviral agents including Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis. Diagnostic tests to determine the specific organism responsible for acute bronchitis are impractical, so therapy is usually empiric.

Treatment of acute bronchitis consists of symptomatic relief with cough suppressant medication (antitussives), pain relief with nonsteroidal anti-inflammatory drugs, and decongestants if nasal and sinus congestion is present. Antibiotics against bacterial organisms are not indicated in the treatment of acute bronchitis. If acute bronchitis occurs during a community outbreak of influenza A or B infection, influenza is likely and may be managed with new antiviral drugs that shorten the duration of illness. This therapy is effective, however, only if begun within two days of the onset of symptoms. Expense and limitation of the symptomatic benefit to one to two days render such antiviral therapy controversial.

A few patients with acute bronchitis suffer from persistent cough beyond seven to ten days, requiring management with inhaled bronchodilators such as albuterol. Persistent cough along with sore throat (pharyngitis) may suggest infection from Mycoplasma pneumoniae or Chlamydia pneumoniae, prompting treatment with an antibiotic (doxycycline, erythromycin, clarithromycin, or azithromycin). A persistent, violent, barking cough may be a clue to infection from Bordetella pertussis. This fairly common problem may respond to a one- or two-week course of antibiotic treatment with erythromycin. A cough that persists for more than three weeks is termed "chronic cough." Occasionally chronic cough follows an episode of acute bronchitis. More likely, however, chronic cough is caused by some type of under-lying chronic lung disease, bronchial asthma, postnasal drip, or gastroesophageal reflux disease.

It is important to distinguish acute bronchitis from pneumonia. Patients with pneumonia usually have fever, chills, and a more severe illness than is seen with acute bronchitis, and the chest X-ray reveals a shadow (lung infiltrate) that is lacking in acute bronchitis. Acute bronchitis should also be distinguished from an attack of bronchial asthma and from acute exacerbation of chronic obstructive pulmonary disease (COPD).

Chronic bronchitis is characterized by chronic or recurrent excess bronchial mucus secretion. About 12.5 million Americans are thought to suffer from chronic bronchitis, and the morbidity, mortality, and economic impact of this condition (and of emphysema) are immense. Chronic bronchial inflammation results in a persistent cough, which by definition occurs most days for at least three months of the year for at least two successive years. The cough is typically productive of varying amounts and appearance of phlegm (sputum). Other diseases that are associated with excessive mucus secretion, such as chronic sinusitis with post-nasal drip, asthma, lung cancer, tuberculosis, and bronchiectasis, must not be confused with chronic bronchitis. Patients with "simple chronic bronchitis" lack airflow obstruction on pulmonary function tests (spirometry), whereas those with "chronic obstructive bronchitis" have reduced air-flow rates. Both types of chronic bronchitis are closely linked to cigarette smoking.

Chronic obstructive bronchitis is one of two types of COPD, the other being emphysema. Some, but not all, patients with simple chronic bronchitis progress to the chronic obstructive form. Most patients with chronic obstructive bronchitis also have emphysema. Chronic asthmatic bronchitis is an overlap condition with features of both chronic bronchitis and bronchial asthma. Industrial bronchitis is a type of chronic bronchitis associated with occupational exposure to dusts.

Patients with chronic obstructive bronchitis usually have a daily cough, sputum production, shortness of breath (dyspnea), and sometimes wheezing. These symptoms typically appear in the age range from forty-five to sixty and gradually progress, particularly if cigarette smoking continues. In advanced cases, chronic respiratory failure may occur. Acute exacerbations of chronic bronchitis are intermittent episodes of increasing cough with discolored sputum, shortness of breath, and wheezing that typically occur one or two times each year. Viral or bacterial infection is a common cause of these episodes.

Medical management of chronic bronchitis includes general measures such as patient education, smoking cessation, improved nutrition, exercise, and immunization against infection by influenza virus and Streptococcus pneumoniae. Complete elimination of cigarette smoking is essential and has been proven to slow the rate of decline in pulmonary function that occurs over time. Patients with chronic obstructive bronchitis are treated with bronchodilator drugs such as inhaled ipratropium bromide and albuterol and occasionally with oral theophylline. Supplemental oxygen is prescribed for patients with low arterial blood-oxygen levels (hypoxemia), and antibiotics are often given for significant acute exacerbations. Other management strategies that are recommended for emphysema are also appropriate for chronic obstructive bronchitis because of the over-lap of these two conditions.

JOHN L. STAUFFER

(SEE ALSO: Acute Respiratory Diseases; Asthma; Influenza)

BIBLIOGRAPHY

American Thoracic Society (1995). "Standards for the Diagnosis and Care of Patients with Chronic Obstructive Pulmonary Disease." American Journal of Respiratory and Critical Care Medicine 152(5):S77– S120.

Anthonisen, N. R.; Manfreda, J.; Warren, C. P. W.; Hershfield, E. S.; Harding, G. K. M.; and Nelson, N. A. (1987). "Antibiotic Therapy of Acute Exacerbations of Chronic Obstructive Pulmonary Disease." Annals of Internal Medicine 106(2):196–204.

Sethi, S. (2000). "Infectious Etiology of Acute Exacerbations of Chronic Bronchitis." Chest 117(5):380S–385S.

Snow, V.; Mottur-Pilson, C.; and Gonzales, R. (2001). "Principles of Appropriate Antibiotic Use for Treatment of Acute Bronchitis in Adults." Annals of Internal Medicine 134:518–520.