Bronchoconstriction is narrowing of the airways of the lungs due to tightening of the surrounding muscles. Bronchioles are tubes that air flows in and out of the lungs. Narrowing of these tubes can occur in response to certain triggers as well as the inflammation that occurs in asthma. Bronchoconstriction is one of the major components of an asthma attack.
Bronchoconstriction During an Asthma Attack
Asthma is one of the most common chronic diseases of childhood. But it can occur in adults also, even during old age. An asthma attack occurs when the airways react to certain triggers of asthma. During an attack, excess mucus is produced and it clogs the airways. At the same time, there is swelling of airways and tightening of the muscles that surround them. This causes narrowing of the airways which is known as bronchoconstriction. Narrowing of airways and excess mucus production make breathing difficult during an asthma attack.
Certain cells in the airways, particularly mast cells are thought to be responsible in initiating bronchoconstriction in response to certain triggers during an asthma attack. These mast cells release substances like histamine and leukotrienes which are responsible for contraction of the airways. Also, certain white blood cells like eosinophils migrate to the area of bronchoconstriction and release certain additional substances which further cause bronchoconstriction.
Common Triggers of Asthma
Bronchoconstriction with asthma is caused by a number of triggers. They are:
- Tobacco and cigarette smoke
- Dust mites
- Animal dander
- Respiratory infections
- Cold and windy weather
All of these triggers do not cause bronchoconstriction in all patients of asthma. Different triggers may be responsible in different persons.
Bronchoconstriction gives rise to the following symptoms:
- Cough, particularly worse at night
- Shortness of breath
- Chest tightness
- Reduced exercise tolerance
During exercise, initially dilation of airways occurs. If exercise continues beyond 10 minutes, asthma symptoms may occur. Cold, dry air provokes more obstruction of airways as compared to warm humid air.
The following investigations help in the diagnosis of asthma:
- Blood eosinophils more than 4% or 300-400/microliter
- Total serum immunoglobulin levels more than 100 IU
- Chest X-ray to rule out other respiratory diseases
- Pulmonary function testing by spirometry
- Allergy skin testing to assess if there is any associated features of skin allergy
Treatment and Follow Up
The aim of treatment is to control asthma symptoms, prevent acute attacks of asthma, maintain normal exercise levels and achieve normal pulmonary function.
The management includes both preventive steps as well as medication.
- Diet - Any specific food known to cause asthma and bronchoconstriction should be avoided.
- Exercise - It should be done in a warm, humid atmosphere rather than dry and cold environment.
Drugs for asthma includes a number of medications like salbutamol, levalbuterol and salmeterol which are beta agonists and cause bronchodilation. Corticosteroids like beclomethasone and fluticasone decrease the fluid accumulation and inflammation.
Other drugs available are ipratropium bromide, mast cell stabilizers like cromolyn sodium, leukotriene receptor antagonists like montelukast and lipoxygenase inhibitors like zileuton.
- Allergy and allergic diseases: the new mechanisms and therapeutics, 1998 by Denburg Judah.
- Asthma and COPD: basic mechanisms and clinical management, 2002 by Barnes Peter.