Asthma is a chronic disease in which sufferers have repeated attacks of difficulty in breathing and coughing. There seems to be an increase in the amount of asthma all over the world, especially in children. To understand what happens in asthmatic attacks it is helpful to visualise the basic structure of the airway tubes of the lung.
The main airway (windpipe, trachea) of the body is about 2-3cm across. It divides into its main branches (bronchi), which lead to the right and left lung, which divide further, like the branches of a tree, to supply air to all parts of the lungs.
The smallest tubes (bronchioles) are only millimetres wide and they are made up of ring-shaped muscles that are capable of contracting or relaxing. Anything that makes them contract will narrow the passages, which makes it more difficult for the air to pass through and also gives rise to the characteristic wheezy noise.
Asthmatics tend to be sensitive to various types of irritants in the atmosphere that can trigger this contraction response from the bronchial muscles.
The bronchi also have an inner lining that becomes inflamed in asthma, which makes the lining swell and produce an excess amount of the mucus (phlegm) it normally makes.
All of these processes contribute to the airway narrowing and the treatment for asthma is aimed at reversing them as much as possible.
People of all ages get asthma but 50 per cent of sufferers are children, mostly boys, under 10. Among adults, women are more likely to develop asthma than men.
