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Reviewed by Dr Gavin Petrie, consultant respiratory physician and Dr Paul Klenerman, consultant physician
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What is asthma?
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| Make sure you use the right technique when you take your
asthma medication. Poor technique is the most common reason for ineffective
treatment. |
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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.
How do you get asthma?
Asthma can be triggered by external agents, such as irritants in
the atmosphere which are breathed in, or by internal reactions within the body
that have been caused by an external influence. The kinds of provoking factors
can be divided into two groups:
-
non-specific factors: all asthma patients are affected by a
number of things that are referred to as irritants. They include exertion,
cold, smoke, scents and pollution.
-
specific factors: these are irritants or
allergens in the form
of pollen, dust, animal fur, mould and some kinds of food. A
virus or bacteria,
chemical fumes or other substances at the workplace and certain medicines, eg
aspirin and other
non-steroidal
anti-inflammatory drugs (NSAIDs), may also cause asthma.
To acquire asthma, people seem to need to have been born with a
predisposition to the disease. It may not reveal itself until they have been
exposed to some asthma irritants.
Smoking mothers, low birth weight, a lack of exposure to
infection in early life and traffic fumes have all been associated with the
increase in asthma. Less draughty houses resulting in a higher concentration of
house dust mites and cooking gases may also be part of the problem.
Currently, a great deal of research looking for the genes that
allow asthma to develop is being carried out. But until we can prevent asthma,
we have to suppress the symptoms and try to avoid the triggers where
possible.
What might trigger acute asthma attacks?
-
Exertion.
-
Cold.
-
Smoke.
-
Air pollution including exposure to certain chemicals. An
example is isocynates which are used in some painting and plastics industries.
-
Airway infection.
-
Allergies, eg to pollens, house dust mites, domestic animals
(especially cats), aspirin and non-steroidal anti-inflammatory drugs (NSAIDs)
such as ibuprofen.
What does asthma feel like?
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It is difficult to breathe and there is shortness of breath.
-
Wheezing when breathing out.
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Coughing, especially at night and with a
little mucus.
What are the warning signals of worsening attacks?
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Inhaled medicines appears less effective than usual.
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Symptoms of cough or wheeze on exertion.
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Night-time wakening with wheeze or cough.
-
Fall in the
peak flow meter
reading (a peak flow meter is a simple device that measures the maximum speed
at which a person can breathe out).
When it appears that your asthma is becoming less well
controlled, you should consult your doctor for advice on what to do.
What are the danger signals of severe attacks requiring immediate
medical attention?
-
Bluish skin colour and gasping
breath.
-
Exhaustion so severe that speech is
difficult or impossible.
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Confusion and restlessness.
What can you do to help yourself?
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Avoid the substances you are allergic to, if possible. It can
be difficult to know which specific factors may give you trouble, but general
irritants like tobacco smoke should be avoided.
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It is important to take your prescribed preventive medicines,
even if you feel well.
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If you get a serious attack, contact your doctor or the
emergency services.
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Discuss your treatment with
your doctor or practice nurse. You should know what to do if, for
example, you get a bit worse during a cold. This will usually involve a
temporary increase in the dosage of your treatment.
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Be familiar with the
use of a peak flow
meter, which can help you judge your asthma during spells when it is
worse.
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Make sure you
use your inhaler
device correctly. If you are unsure your practice nurse, doctor or
pharmacist will be able to help and advise you.
How does the doctor make the diagnosis?
The diagnosis is made on the basis of the patient's history
of symptoms and on simple tests of the lungs' function but it is not
always easy to come to a diagnosis of asthma if the symptoms are mild and
intermittent.
For those people whose asthma is associated with
eczema and
hay fever it can be
helpful to take blood samples and skin tests to look for hypersensitivity
towards specific substances.
What should I do?
Be active. If you get attacks during intense activity it may be
a good idea to take 'reliever' medicine before you begin to exercise.
These medicines, properly known as
bronchodilators, have a relaxing effect on the muscle
surrounding the bronchioles. Swimming is probably the best form of exercise for
asthma patients but the most important thing is to stay active.
What are the prospects for asthma suffers?
-
Although asthma cannot be cured it can usually be well treated
so that the symptoms give little trouble.
-
Half of the children who get asthma 'grow out of
it'.
-
It is vital to stop smoking to avoid developing long-term lung
damage (chronic bronchitis,
'smoker's lung'), which will reduce the lung function
drastically.
-
Severe attacks of asthma can be fatal but only if they are
treated inadequately or not soon enough.
Medicine
Medicines for asthma are generally thought of in two main
groups.
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Relievers (bronchodilators): these are
quick-acting medicines that relax the muscles of the airways. This opens the
airways and makes it easier to breathe. They are used to relieve
symptoms.
-
Preventers (anti-inflammatories): these act over
a longer time and work by reducing the inflammation within the airways. They
should be used regularly for maximum benefit. When the dosage and type of
preventive medicine is correct, there will be little need for reliever
medicines.
Relievers
There are three groups of these.
Beta-2 agonists
Beta-2 agonists act on molecule-sized receptors on the
muscle of the bronchioles. The medicine fits the receptor like a key fits a
lock and stimulates the muscle to relax. Examples of those which act for a
short time (three or four hours following a single dose) are
salbutamol (eg
Ventolin) and
terbutaline (eg
Bricanyl). These medicines are inhaled from a variety of delivery
devices, the most familiar being the pressurised metered-dose inhaler (MDI).
They are used when required to relieve shortness of breath.
Longer-acting beta-2 agonists include
salmeterol
(Serevent) and formoterol (eg
Foradil,
Oxis). Their
action lasts over 12 hours, making them suitable for twice-daily dosage to keep
the airways open throughout the day.
Anticholinergics
One of the ways in which the size of the airways is
naturally controlled is through nerves that connect to the muscles. The nerve
impulses cause the muscles to contract, thus narrowing the airway.
Anticholinergic medicines block this effect, allowing the airways to open. The
size of this effect is fairly small, so it is most noticeable if the airways
have already been narrowed by other conditions, such as
chronic bronchitis.
An example of an anticholinergic is
ipratropium bromide (eg
Atrovent). It has a maximum effect 30 to 60 minutes after inhalation,
which lasts for three to six hours.
Theophyllines
Theophylline (eg
Slo-phyllin) and
aminophylline (eg
Phyllocontin continus) are given by mouth and are less commonly used in
Britain because they are more likely to produce side effects than inhaled
treatment. They are still in very wide use throughout the world.
All three types of reliever can be combined if necessary.
Preventers
There are three main groups of these.
Corticosteroids
Corticosteroids (or 'steroids') such as
beclometasone (eg
Becotide),
budesonide (eg
Pulmicort) and
fluticasone (eg
Flixotide) have made an enormous difference to the management of asthma.
They work to reduce the amount of inflammation within the airways, reducing
their tendency to contract and have allowed many patients with previously
troublesome asthma to lead almost symptom-free lives. They are usually given as
inhaled treatment, although sometimes oral steroid tablets (prednisolone, eg Deltacortril) may
be required for severe attacks.
Although steroids are powerful medicines with many potential
side effects, their safety in asthma has been well established. It is also
important to balance the problems that arise from poorly treated asthma against
the improvement in health which occurs when the condition is well treated.
Cromones
There are two medicines in the cromone group:
sodium cromoglicate (eg
Intal) and
nedocromil sodium
(Tilade). They also act to reduce inflammation of the airways. They tend
to be best for mild asthma and are more effective in children than adults. The
medicines are given by inhalation and are usually very well tolerated.
Leukotriene receptor antagonists
Leukotrienes are released from the lungs in people with
asthma, causing inflammation and increased mucus production in the airways.
They also cause the muscles lining the airways to contract, which narrows the
airways. All of this makes it difficult for air to get in and out of the lungs.
Leukotriene receptor antagonists block leukotriene receptors
in the lungs and, as a result, block the action of the leukotrienes. This
prevents the excess mucus production, inflammation and narrowing of the airways
and so prevents asthma attacks. It’s also useful for preventing asthma
triggered by exercise.
By blocking this effect with these antagonist medicines the
constriction is reversed. There are two leukotriene receptor antagonists
currently available:
montelukast
(Singulair) and
zafirlukast
(Accolate), both of which are taken as tablets.
Combination inhalers
Combination inhalers have been the mainstay of asthma
treatment for a number of years.
In the 1990s longer-acting combinations of bronchodilators
and/or corticosteroids in one apparatus were developed. There are currently a
number of these regularly used in the UK, such as
Seretide (salmeterol,
fluticasone),
Symbicort (budesonide,
formoterol) and
Combivent UDVs
(salbutamol, ipratropium).
Many patients feel their asthma is much better controlled on
these combination inhalers and compliance is much better as they only need to
use one inhaler rather than two.
Easy to use, they can also be useful in visually impaired
patients and those who find using two or even three inhalers difficult to
remember.
Some trials have found that morning peak flow rates are better
using combination inhalers rather than single inhaler alone.
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Based on a text by Dr Carl J Brandt and Dr Finn Rasmussen
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Last updated 02.07.2008
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