What is Asthma?

Asthma is a widespread persistent inflammatory condition of the lung airways whose cause is not totally understood. It's a disorder of the respiratory system in which the passage of air to the lungs sporadically narrow causing coughing, wheezing, and shortness of breath which often worsens at night. This tightening is typically short-term and reversible, but in severe attacks, asthma can result in death.

The term Asthma most frequently refers to bronchial asthma, another inflammation of the airways, but it is also used to refer to cardiac asthma, which develops when fluid builds up in the lungs as a complication of heart failure.

Asthma causes inflammation of the airways airflow into and out of the lungs. The muscles of the bronchial tree become taut and the lining of the air passages to enlarge, which reduces airflow and produces the characteristic asthmatic wheezing sound.

An asthma attack, can also occur as an allergic reaction to an allergen or other substance (acute asthma), or as a part of a complex disease cycle which includes reactions to stress or exercise (chronic asthma).

Alternate Names For Asthma Include
Bronchial Asthma, Exercise Induced Asthma - Bronchial, Reactive Airways Disease (RAD)

Chronic Asthma
In chronic asthma, inflammation can be accompanied by irreparable airflow limitation. In pre-school children underlying pathology may not exhibit considerable bronchial hyper reactivity, and there is also no evidence chronic inflammation is a basis for the episodic wheezing  which is associated with viral infections.

Characteristic Features of Chronic Asthma
These include an alteration of the construction and functions of elements of the airways. Together, these structural changes interact with the inflammatory cells and mediators to cause the characteristic features of the disease.

Occurrence
Asthma occurs in both males and females of all ages, racial groups, and socioeconomic levels. it is also found Asthma is usually more common in poor built-up neighbourhoods, and in cold climates, and developed countries, but this is probably due to the poor living conditions of the asthmatic sufferers.

Research suggests genetic factors can also increase the risk of developing asthma, and children with a family history of asthma are more likely to develop the disease than other children. However many people with no family history of asthma can also develop the disorder.

Prevalence Of Asthma
In many countries the frequency of asthma is increasing, particularly in the second decade of life where it affects 10-15% of the population. There is also a noted geographical variation, with asthma being common in more urbanized countries.

Some of the highest rates of Asthma are countries such as New Zealand and Australia, but it is much rarer in Far Eastern countries such as China, Malaysia, Africa and Central and Eastern Europe.

Having said that however long-term follow-up in these developing countries suggests asthma problems may become more frequent as the population becomes more 'westernized'.

Studies of occupational asthma suggest a high proportion of the workforce, perhaps up to 20%, may become asthmatic if exposed to potent sensitizers.

Asthma has three characteristics:

    * airflow limitation,
    * airway hyper responsiveness,
    * Inflammation of the bronchi with its associated plasma exudation, oedema, and smooth muscle hypertrophy, mucus plugging and epithelial damage.

Asthma can be divided into:
Extrinsic - implying a definite external cause
Intrinsic - when no causative means can be identified.
 

Extrinsic asthma
This occurs most regularly in individuals who show a positive skin-prick reaction to universal inhalant allergens. Positive skin-prick tests to these inhalant allergens are shown in 90% of children with persistent asthma. Interestingly though only 50% of adults veer towards this trend.

Intrinsic asthma
This usually starts in middle age, though many sufferers with adult-onset asthma show positive skin tests and on closer questioning often give a history of respiratory symptoms which are compatible with childhood asthma.

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