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Bronchospasm

Definition

Bronchospasm is an abnormal contraction of the smooth muscle of the bronchi, resulting in an acute narrowing and obstruction of the respiratory airway. A cough with generalized wheezing usually indicates this condition.

Bronchospasm is a chief characteristic of asthma and bronchitis.

Description

Bronchospasm is a temporary narrowing of the bronchi (airways into the lungs) caused by contraction of the muscles in the lung walls, by inflammation of the lung lining, or by a combination of both.

This contraction and relaxation is controlled by the autonomic nervous system. Contraction may also be caused by the release of substances during an allergic reaction.

The most common cause of bronchospasm is asthma, though other causes include respiratory infection, chronic lung disease (including emphysema and chronic bronchitis), anaphylactic shock, or an allergic reaction to chemicals.

The bronchial muscle goes into a state of tight contraction (bronchospasm), which narrows the diameter of the bronchus. The mucosa becomes swollen and inflamed which further reduces the bronchial diameter.

In addition, bronchial glands produce excessive amounts of very sticky mucus which is difficult to cough out and which may form plugs in the bronchus, further obstructing the flow of air.

When bronchi become obstructed, greater pressures are needed to push air through them in order to meet the body's requirement for oxygen. This requires greatly increased muscular effort. Breathing during bronchospasm requires more effort than normal breathing.

The excessive amounts of sticky mucus caught in the bronchi are highly irritating, and often trigger coughing.

Causes and Risk Factors

Excessive bronchial irritability is the root of asthma. Asthmatic attacks in children can be caused by a number of triggers:

Allergy. When foreign substances such as bacteria, viruses or toxic substances enter the body, one of the natural defenses is the formation of antibodies - molecules which combine with the foreign substances so as to render them harmless. This process is called immunity. Allergic children form protective antibodies just as do normal children. However, the allergic child forms other kinds of antibodies - which, rather than being protective, may actually do harm.

The ones that commonly cause problems are animal dander, pollen, dusts, molds and foods. Inhalation of an allergen triggers bronchoconstriction.

Exercise. This is a very common trigger for the symptoms in asthmatic children. This may take the form of obvious wheezing after exercise, or simply coughing.

Emotions. Psychological stress may trigger symptoms but asthma is not a psychosomatic disease.

Upper Respiratory Infections. When an asthmatic child has an upper respiratory infection, asthma may be triggered. Viral respiratory infections can provoke and alter asthmatic responses. Viral respiratory illnesses may produce their effect by causing epithelial damage, producing specific Immunoglobulin E (IgE) antibodies directed against respiratory viral antigens and enhancing mediator release. Antibiotics are not usually helpful -- either in clearing up the infection or in preventing bronchospasm. The best treatment of a cold is prevention through frequent handwashing.

Irritants. There is a wide variety of substances which irritate the nose, throat or bronchi. Cigarette smoke is one of the most common, but dust, aerosol sprays, and strong odors may serve as irritants.

Symptoms

Cough is a major symptom, and may be a more important symptom than wheezing in some asthmatic children, especially infants and toddlers. Wheezing and tightness in the chest are also very common.

Diagnosis

Diagnosis is based upon the clinical exam in which wheezing, poor air flow and generalized signs of an asthma attack may be found. Chest x-ray may show little if any change from normal.

Treatment

Beta2-agonists relax airway smooth muscle and may modulate mediator release from mast cells and basophils. Beta-agonist inhalers (bronchodilators) act to ease symptoms of asthma by relaxing muscles surrounding the walls of the bronchial tubes. Most beta-agonist drugs are prescription medications. Those sold in the U.S. include albuterol (Proventil, Ventolin), bitolterol (Tornalate), isoetharine (Bronkometer), metaproterenol (Alupent), pirbuterol (Maxair), and terbutaline (Brethaire).

While anti-inflammatory drugs, such as inhaled corticosteroids or cromolyn sodium, treat the underlying inflammation that causes the airways to react and narrow, beta-agonists only treat symptoms.

Questions to Ask Your Doctor

What is the cause of the bronchial contraction?

What is the relationship of the bronchospasm to upper respiratory infection?

Is there another source of irritants?

What can be done to relax the muscles?

Are anti-inflammatory drugs called for?

Is the use of beta2-agonists indicated?

How can we best cope with the symptoms?

What is the long-term prognosis?