Bronchitis is an obstructive pulmonary disease characterized by inflammation of the bronchi of the lungs. It is a common disease of habitual smokers and residents of polluted cities.

Like many disorders, bronchitis can be acute (short-term), or chronic (long-lasting). Chronic bronchitis is defined clinically as a persistent cough that produces sputum for at least three months in two consecutive years.

Features

Signs and symptoms

The primary symptom of chronic bronchitis is a persistent cough that produces sputum. A patient may have only this symptom for many years before others develop. Eventually, the patient will experience shortness of breath (dyspnea) on exertion. As the disease progresses, other symptoms may appear, such as an inability to sufficiently expel carbon dioxide from the lungs (hypercapnia) and insufficient oxygenation of the blood (hypoxemia) leading to cyanosis. Severe chronic bronchitis will commonly lead to cor pulmonale and heart failure

Morphology

When the airways of a lung affected by chronic bronchitis are viewed under a microscope, several features are usually observed:

• an increase in the number of goblet cells with mucus blocking the airway
• clusters of pigmented alveolar macrophages
• the presence of inflammatory cells (e.g. neutrophils)
• scarring (fibrosis) of the walls of the bronchioles

Diagnosis

A physical examination will often reveal decreased intensity of breath sounds (rhonchi) and extended expiration.

A common test when ordered when evaluating a patient for bronchitis is a sputum culture. In this test, a sample of sputum from a patient is stained and examined for the presence of bacteria that can cause disease.

There are a variety of lab test results that indicate the presence of chronic bronchitis in a patient, namely:

• a chest x-ray that reveals hyperinflation and increased bronchovascular markings
• a pulmonary function test that shows an increase in the lung's residual volume and a decreased vital capacity
• arterial blood gases that show a decreased level of oxygen in the blood and an increased level of carbon dioxide
• a sputum culture that has pathogenic microorganisms and/or neutrophils in it

Diagnosis of acute bronchitis is aided by finding an elevation in the level of the diaphragm on chest x-ray.

Pathophysiology

The initiating event in developing chronic bronchitis appears to be chronic irritation due to inhalation of certain substances (especially cigarette smoke). The earliest clinical feature of bronchitis is increased secretion of mucus by submucousal 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 mucousal hypersecretion. As bronchitis persists to become chronic bronchitis, a substantial increase in the number of goblet cells in the small airways is seen. This leads to further increased mucous production that contributes to the obstruction of the airways.

The role of infection in the pathogenesis of chronic bronchitis appears to be secondary. However, although infection is not responsible for initiating bronchitis, it may have an important role in maintaining it. Acute exacerbations of the long-standing bronchitis may result from infections.

Treatment

The single most important thing a patient can do to improve chronic bronchitis is to quit smoking. Oxygen therapy, bronchodilator drugs, and lung volume reduction surgery are also used to treat chronic bronchitis.

Prognosis

Pulmonary hypertension, cor pulmonale, and chronic respiratory failure are possible complications of chronic bronchitis.

The prognosis for patients with severe chronic bronchitis is poor. The median survival time of patients with severe bronchitis is four years (Medical Diagnosis and Treatment).

Prevention

Chronic bronchitis is very preventable. The main action to reduce your risk is to eliminate exposure to cigarette smoke. Smokers in the early stages of chronic bronchitis can change and improve the course of the disease by quitting smoking.

History

Bronchitis was originally named and described by Charles Bedham in 1808. It was introduced by P. Frank in his work "Interpretationes Clinicae" in 1812.

External links

Section Online medical references

• Acute bronchitis Merck Manual of Diagnosis & Therapy
• Bronchitis The Merck Manual - Second Home Edition
• Chronic Obstructive Pulmonary Disease The Merck Manual - Second Home Edition
• Chronic Obstructive Pulmonary Disease The Merck Manual of Geriatrics
• Bronchitis Lungs OnLine
• Acute Bronchitis FamilyDoctor.org (American Academy of Family Physicians)

References

• "Chronic bronchitis." Springhouse Handbook of Diagnostic Tests, 2nd ed. (1999). ISBN 0-87434-982-6
• "Chronic obstructive pulmonary disease." 2005 Current Medical Diagnosis and Treatment. ISBN 0-07-143692-8
• Kumar, Vinay, Abul Abbas, and Nelson Fausto. Robbins and Cotran Pathologic Basis of Disease, 7th ed. (2005). ISBN 0-7216-0187-1
• Skinner, Henry Alan. The Origin of Medical Terms. (1970).da:Bronkitis

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