Asthma - The Basics
and a little bit more
Asthma is defined in Essential Allergy, by Niels Mygind, Ronald Dahl,
Soren Pedersen and Kristian Thestrup-Pedersen 2nd edition as :
a lung disease characterised by: 1, variable and reversible airway obstruction;
2, airway inflammation; and 3, bronchial hyper-responsiveness.
A medical description of asthma
Asthma is a disease causing difficulty in breathing, with recognisable symptoms: episodic wheezy breathlessness,
which varies considerably within short periods of time, and is
reversible (but not completely so in some patients) either spontaneously
or with treatment; most important is a significant response to beta2 agonists
and to corticosteroid drugs (Table 1).
Table 1. Characteristics of asthma in 10 points
Characteristics of Asthma
|1 Episodes of wheezy difficulty in breathing|
|2 Narrowing of the air passages in the lungs and hence increased resistance to airflow.|
The narrowing is due to different combinations of:
(a) contraction of muscles around the air passages
(b) swelling of the airway lining due to airway inflammation
(c) excessive mucus in the airways
|3 Rapid and considerable changes in airway obstruction (peak flow variation >= 20%)|
|4 Frequent nocturnal episodes and low morning peak flow values|
|5 Significant reversibility with drugs which resemble adrenaline, the beta2 agonists |
|6 Significant reversibility with steroid drugs |
|7 Symptom-free periods|
|8 Frequent occurrence of allergy|
|9 Inflammation of the air passages, characterised by eosinophils in the airway wall|
|10 Bronchial hyper-responsiveness to nonspecific stimuli such as cold air or histamine|
Three facts stand out about asthma.
- Drugs, such as those resembling two of our hormones, help asthma.
These two hormones are adrenaline (epinephrine in the USA) and hydrocortisone (a steroid). In practice we use modified forms of these hormones to get fewer side effects.
Adrenaline (epinephrine) shoots into our bloodstream when we have a sudden fright or emergency. It is the quick-acting hormone from the middle of the adrenal glands near our kidneys. It makes your pulse race, makes your heart thump, and readies your body for emergency action. In asthma, the medicines which resemble adrenaline quickly relieve asthma for a short time. So they are called 'relievers'.
Hydrocortisone comes from the outer part of our adrenal glands, called the 'cortex'. It is also partly an emergency hormone but it works much more slowly, for much longer, and in a completely different way from adrenaline. Medicines which resemble it act slowly make the lining of air tubes in asthma more normal. So your asthma becomes less bad and you are less likely to get asthma attacks. So these steroid medicines are called 'preventers'. There are other asthma 'preventers', but the steroids are the most powerful.
Most people who have asthma should have both of these kinds of medicine. Usually the best way to take them is to breathe them in. This is because you need less that way, and won't have so many side effects. It also works more quickly, important with the adrenaline-like 'relievers'. The third advantage is that the hydrocortisone-like steroid 'preventers' you breathe in can be chosen to be beautifully 'biodegradable' inside the body. They work in the lung, but don't get much chance to give side effects in the rest of your body, because your liver splits them up.
There are also other drugs which help asthma. Whilst drugs can remove all your symptoms if you have mild asthma, people with more severe or long-standing asthma don't get nearly such good results.
- The cause of the inflammation with eosinophils which underlies most asthma in younger sufferers is allergy.
We do not understand why so many people in 'Westernised' countries suffer from allergies, compared to people in less affluent rural parts of the world, though we have some clues. There is however a mass of evidence which proves that asthma is in general an environmentally induced disease. This raises the challenging possibility that we may be able to prevent asthma by altering our environment.
Treating asthma by removing the allergic cause can be very successful when the cause is easy to remove, as when the allergic cause is a dust or vapour inhaled only at work. The same is true when the cause is a domestic pet such as a cat or dog, though reluctance to part with a loved pet commonly prevents success. But the commonest cause of asthma is allergy to house dust mites, and getting rid of mites sufficiently to make a big difference to asthma requires a major change in lifestyle and is expensive.
There may be future treatments which abolish or diminish the allergy process in the body.
- Asthma changes progressively during the lifetime of someone who has it.
Children may grow out of asthma, but some of these grow back into it later. In people who have lifelong asthma the obstruction to the airways comes to be less completely relieved by drugs. One of the aims of treatment, according to current concepts, is to minimise the inflammation in the lung airways which we believe causes this long-term worsening.
Some asthma topics
We're still working on this section; what follows is only a beginning.
What should my Peak Flow be?
We've provided a widely used chart from which you can read off your predicted normal Peak Flow for your sex, age and height.
What are asthma triggers, and what are the causes?
A cause is something without which you would not be asthmatic.
A trigger is something which sets off an attack, but which does not make you asthmatic in the first place.
You will obviously want to avoid both causes and triggers, but the causes are more serious: without them the triggers do no harm.
Causes include allergies to house dust mites, cats, dogs, and moulds.
It is a mistake to belittle causes like house dust mites or cats by calling them "trigger factors".
Look up our page on triggers and causes of asthma..
Expecting a baby? Asthma and pregnancy
The news is not just reassuring; there is all the more reason to take extra care of your asthma if you are expecting a baby. Look up our page on asthma and pregnancy..
Exercise can cause asthma attacks
Exercise-induced asthma is an attack of asthma brought on by running or other exercise. Look up our page on exercise-induced asthma to find out what you can do about it.
Is your work causing your asthma?
If your asthma always seems to get better at weekends or when you go on holiday, one explanation could be that something at work is causing it.
Often overlooked, a work-related cause means you could be cured
Look up our page on occupational asthma..
Is it really an asthma attack?
Usually the problem with making a diagnosis of asthma is making it early enough. But sometimes, usually in people who do have true asthma as well, difficulty in breathing can be caused by abnormal movements of the voice box during breathing. This can mimic a severe asthma attack so closely that a correct diagnosis is difficult. But if it is recognised, treatment will be much more appropriate. To find out more about this condition, called Vocal Cord Dysfunction syndrome, click here. You will see information from the centre where it was best described, though the problem had been recognised before that.
Vocal cord dysfunction syndrome can mimic an attack
Of course there are quite a few other illnesses which can mimic asthma, though these are all rather rare compared to asthma. But vocal cord dysfunction has become better understood in recent years, so we have given it a place here.
Asthma may get worse from stomach acid rising up your gullet (gastro-oesophageal reflux disease, also called GER, or GERD)
Some research shows that 'acid reflux' from the stomach, acid stomach juice moving up the wrong way towards the mouth, can make asthma worse. Acid reflux can cause painful 'heartburn' which you can relieve with antacid medicines (medicines which neutralise the acid). It happens mostly in people who are older and overweight. But it can happen in children and in all kinds of people.
But the experts are not agreed
When researchers put acid into the gullets of people with asthma, it made their asthma worse.
People who have asthma get acid reflux more often than people without asthma. This is probably because of the big pressure changes in the chest during breathing in people with asthma. These high pressures could force liquid to travel the wrong way.
So asthma sufferers seem to lose out twice over. In the first place it is bad for them to have acid reflux, and in the second place they have acid reflux more often than other people.
But this is not the whole story. If acid reflux was really an important cause of asthma worsening, then treatments against acid reflux should make the asthma better. In practice many doctors have found such treatment disappointing. Research continues, but it's already continued a long time now. It's hard to think we'll be surprised by future research on this.
In the meantime, if you have asthma and you also have acid reflux, it could just be that careful treatment of your reflux will make your breathing better.
If your asthma is bad and no-one knows why, some doctors would check whether you had reflux by getting an expert to measure the acidity in your gullet. If the result showed acid, they would try to improve your lungs by treating your stomach. If it was me, despite the reservations, I'd give it a try.
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Home page |
About AAIR |
Asthma caused by exercise (exercise-induced asthma) |
Asthma at work (occupational asthma) |
CORRESPONDENCE PAGE on Asthma |
Other websites on asthma |
Allergy - the basics |
Nut Allergy & Anaphylaxis |
House dust mites |
Other sources of information |
This page is maintained by Martin Stern
Updates: 20 Sept 1998, 4 Apr 2001.
Copyright © 1997, 1998, 2001 Asthma and Allergy Information and Research