Asthma Introduction

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Asthma Overview

Introduction

Classification of Severity

Asthma Signs and Symptoms

Diagnostic Tests for Asthma

Asthma Treatment

[edit] Asthma

Introduction:

Asthma is a very common disease. According to Ref. 3 (page 749) it affects about 15 million people in the US or 5% of the population. Under the age of 10 years males outnumber females by a factor of 1 1/2 to 2. But by the age of 30 years both sexes have about the same probability of getting asthma. In about half of the cases genetic factors and family susceptibility factors play a role.

More than 12 billion $ are spend every year in the US for treatment and disability caused by asthma. More than 9 million office visits and about 2 million Emergency Room visits in hospitals throughout the US are caused by asthma. Air pollution has been shown to be a triggering factor for the development of asthma.

Ozone, car exhausts, smoldering wood fires in the open air and sulfur dioxide that is produced by industry have all been identified as being able to cause acute asthma attacks in previously non diagnosed persons. Viral infections (respiratory synsytial virus in infancy, influenza and rhinovirus in older children and adults) can also cause acute asthma attacks. The worldwide death rates due to asthma has slowy gone up over the years. At present about 3000 asthma patients die every year in the US despite the best modern therapy methods.

Three factors have been identified to play a major role in asthma:

• Allergies: this is leading to an inflammatory reaction of the airways. House dust, molds, food allergies, grass pollen, ragweed, tree pollen and other allergens have been identified to set off this inflammatory reaction.
• Bronchospasm: the wheezing sound that bronchial tubes of asthmatics make comes from spasm in the smaller bronchial tubes, called "bronchioles". "Bronchiolitis" is the name for the spastic condition of these bronchioles, which is associated with inflammation. The physician listens with the stethoscope for evidence of "wheezing", which is the sound equivalent of air being squeezed through the spastic bronchioles of the asthmatic.
• Airway hyperresponsitivity: airways of asthmatics are hyperreacting to stimuli such as cold air, irritants like diesel fumes or other pollutants with spasm of the airways. The hyperirritability of airways often includes the nasal passages (vasomotor rhinitis) as well.

Much has been learnt in recent years about some of the inflammatory mediators that are involved in these various components of asthma. For instance, the mediation of allergies often involves pathological Immunoglobulines (=Ig) that are known to be antibodies circulating in the blood stream. One fraction is called IgE and is responsible for the acute asthma brought on by peanut allergies and another IgE antibody is involved in ragweed allergies. Inflammatory mediators such as histamine, leukotrienes and cytokines are all known to lead to leakage of secretions behind the lining of the bronchial tubes and bronchioles increasing the resistance of the airways. The end result is that the asthmatic with an acute asthma attack cannot move air freely back and forth. With severe cases this leads to an accumulation of carbon dioxide and a lack of oxygen in the blood. Bronchoconstriction has been determined to be due to parasympathetic nerve ending stimulation, which happens by way of reflexes.

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References:

1. Noble: Textbook of Primary Care Medicine, 3rd ed., Copyright © 2001 Mosby, Inc.

2. National Asthma Education and Prevention Program. Expert Panel Report II. National Heart, Lung and Blood Institute, 1997.

3. Rakel: Conn's Current Therapy 2002, 54th ed., Copyright © 2002 W. B. Saunders Company

4. Murray & Nadel: Textbook of Respiratory Medicine, 3rd ed., Copyright © 2000 W. B. Saunders Company

5. Behrman: Nelson Textbook of Pediatrics, 16th ed., Copyright © 2000 W. B. Saunders Company

6. Merck Manual: Asthma

7. Goldman: Cecil Textbook of Medicine, 21st ed., Copyright © 2000 W. B. Saunders Company

8. Ferri: Ferri's Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby, Inc.

9. Rakel: Conn's Current Therapy 2004, 56th ed., Copyright © 2004 Elsevier