ASTHMA

It is appropriate to mention here some basic facts about asthma before knowing the causes.
Firstly, it may be noted that it may appear in infants and disappears as age advances. In other cases, it appears in manhood.
Secondly, it is not an infectious disease.
Thirdly, asthma is hyper-reactivity of the inner lining of the lower and upper portions of the respiratory tract.

Bronchial asthma is defined as a condition characterised by recurrent attacks of difficulty in exhalation due to widespread reversible narrowing of airways in the lungs, which varies in severety over a short period of time either spontaneously or as a result of treatment.

Remarkable hyper-reactivity of the air passages and excessive; response by narrowing to various kinds of stimuli . for example, immunological, infective, psychic, physical and chemical agents. The condition is not due to any known specific infection. The most important feature in bronchial asthma is the hyper-reactivity of bronchial tree. The air passages show excessive response by spasm to all sorts of stimuli, not only to antigen or chemicals like histamin but also to cold air, atmospheric irritants like dust, kitchen fumes, sprays, gases, extreme exercise,etc.

Asthma is -
a) episodic breathlessness which changes in severity spontaneously or with treatment;
b) wheeze (whistling noise) while breathing out, and
c) demonstrable variations in obstruction to air flow through the airways of the lungs. Experts classified bronchial asthma as extrinsic, intrinsic and mixed, also as seasonal, irregular, perennial and status asthmaticus, i.e. attack all the 24 hours.

The respiratory system in the body includes nose, pharynx, larynx, lumps, bronchi, air sacs, etc. Respiration involves two processes of inhalation and exhalation. Respiration is a function in the body which has both involuntary and voluntary nervous controls. Normal rate of respiration is slightly quicker in women than in men. Normal rates per minute are given below: In new born babies 40/min At one year 30, 2 - 5 years 24 and In adults 10 - 20.

The rate and depth of respiration varies with the oxygen demands of the body. They increase with exercise and emotion and decrease during rest. Fourthly, the total lung capacity is from 4.5 to 5 litres of air. Tidal air is the amount of air that is breathed out in one breath and this is about half a litre.