Asthma

About one child in ten develops asthma at some stage during childhood - it is one of the comonest lung problems in children and is becoming commoner, although experts are unsure why. Some children grow out of asthma as they get older, but not all. About one adult in 20 has it and rarely, adults can develop the complaint later in life without any sign of it before.

What is asthma
Asthma involves a severe narrowing of the bronchial tubes. These lead from the windpipe - trachea - into the lungs, carry the oxygen we breathe in to all parts of the lungs and provide a path for the carbon dioxide (a waste product of the body) to escape up the trachea when we breathe out. The difficulty in breathing is most noticeable when breathing out and so asthmatics often breathe in using short gasps but breathe out with a loud wheeze because they have to work hard to push air out against their narrowed lungs. This narrowing can improve by itself or in response to treatment.

What causes asthma?
The cause of asthma remains unknown. Asthma is brought on by a number of different causes, ranging from breathing polluted air (which may explain why asthma continues to increase) to emotional upset, which makes it a rather complex problem to treat. Whatever the cause, it is the release of two chemicals by the body that triggers the narrowing of the airways. The first is histamine. Histamine release is the most common cause of asthma, and the process which brings it about is rather remarkable considering that the substances which trigger it - house dust containing the faeces of house dust mites, animal fur, pollen and fungal spores among others - are so varied.
The second is called acetylcholine. Acetylcholine release from the nerve endings in the bronchial tubes can be caused by a number of substances irritating both the airways and the nerves controlling breathing itself. On top of these chemicals being released, secretions and mucus begins to block the very fine airways in the lungs, making breathing even harder.

Other things known to trigger asthma include:

pregnancy
cold air
cigarette smoke, perfumes and chemical fumes
pet hair
drugs such as aspirin, beta blockers, and anti-inflammatory drugs
exercise
Symptoms
The typical asthma attack is characterized by a sudden shortness of breath and wheezing, which is sometimes accompanied by coughing. Coughing and waking at night is a comon symptom of asthma, and wheezing tends to be worse first thing in the morning. Asthma attacks tend to occur intermittently, with attacks happening every few days, weeks or months depending on the severity. Asthmatics are more prone to chest infections, and this is caused by a failure to clear the lungs fully.

Diagnosis
The diagnosis of asthma is usually straightforward from the history alone, but breathing tests such as a peak flow test will confirm it. This involves having a small hand-held tube which is blown into morning and night, and which measures how well the lungs are working. These give readings during normal periods, during an attack and after having treatment to dilate the airways.

Treatment
The treatment given for asthma largely depends on the type of asthma and the severity of the attacks, but it is broadly divided into two:
The first is everyday treatment to prevent attacks and allow for a normal quality of life - this is known as preventive (or prophylactic) treatment. There are two main types of drug used here, given usually as inhaled treatment which is preferred over tablets or liquid medicines. There are 'preventers', which are inhaled steroids (e.g Becotide) taken on a regular basis to reduce any inflammation in the airways which may cause symptoms.

Second there are 'relievers', which have a much shorter length of action (e.g. Ventolin) and are used to immediately relieve any asthma symptoms. These inhaled medications act directly on the airways surfaces themselves, so any absorption of the drugs into the body itself is minimal.

If asthma proves to be poorly controlled, other treatment can be added to the usual inhalers. These include other inhalers and tablets such as aminophylline or steroids. A sign of poor control is usually an excess usage of the 'reliever' inhaler during the day or night - such use suggests either more 'preventer' is needed on a regular basis, or extra treatment needs to be added to what is being taken.