Intermittent narrowing of the airways, causing shortness of breath and wheezing
- Can occur at any age, but more common in children than adults
- More common in male children and adult females
- Sometimes runs in families
- Exposure to common allergens, including house dust mites, pollens, and pet fur, are risk factors
People with asthma have attacks of wheezing and shortness of breath that vary in severity from day to day and from month to month. Some people have only occasional mild attacks, while others may experience severe disabling symptoms on most days. Most people have symptoms that fall somewhere between these two extremes, but, when their asthma attacks occur, they tend to be unpredictable in length and severity. Severe attacks of asthma are potentially life-threatening if they are not given immediate medical treatment.
Although asthma can begin at any age, most adults with the condition developed it as children. More boys than girls are affected but, in adults, asthma is more common in women. The problems associated with asthma and its management are different in children. For this reason, there is a separate article on asthma in children in the section on childhood disorders.
How common is it?
The UK has one of the highest rates of asthma in the world, although the reasons for this are unclear. In the mid 2000s, about 5.4 million people in the UK were being treated for asthma, of whom about 4.3 million were adults (about 1 in 12 of all adults) and 1.1 million were children (about 1 in 11 of all children). It is the most common long-term medical problem affecting children in the UK.
What are the causes?
During an asthma attack, the muscle in the walls of the bronchi (airways) contracts, causing narrowing. The linings of the airways also become swollen and inflamed, producing excess mucus that can block the smaller airways.
In some people, an allergic response triggers the airway changes. This allergic type of asthma tends to occur in childhood, and may develop in association with eczema or certain other allergic conditions, such as hay fever (see Allergic rhinitis). Susceptibility to these conditions frequently runs in families and may be inherited.
Some substances, called allergens, are known as trigger attacks of allergic asthma. They include pollen, house dust mites, mould, and dander and saliva from furry animals, such as cats and dogs. Rarely, certain foods, such as milk, eggs, nuts, and wheat, provoke an allergic asthmatic reaction. Some people who have asthma are sensitive to aspirin or other anti-inflammatory drugs (such as ibuprofen) and taking them may trigger an attack.
When asthma starts in adulthood, there are usually no identifiable allergic triggers. The first attack is often brought on by a respiratory infection.
Factors that can provoke attacks in a person with asthma include cold air, exercise, smoke, and occasionally emotional factors such as stress and anxiety. Although industrial pollution and exhaust emissions from motor vehicles do not normally cause asthma, they do appear to worsen symptoms in people who already have the disorder. Pollution in the atmosphere may also trigger asthma in susceptible people.
In some cases, a substance that is inhaled regularly in the work environment can cause a previously healthy person to develop occupational asthma, one of the few occupational lung diseases that is still increasing in incidence. If you develop wheezing and shortness of breath that improve when you are not in your work environment, you may have this disorder.
There are more than 200 substances found in the workplace that are known to triggers symptoms of asthma, including isocyanates (used in spray-painting, for example); dust from flour, grain, wood, and from insects and other animals; glues; resins; and latex. However, occupational asthma can be difficult to diagnose because a person may be regularly exposed to a particular trigger substance for weeks, months, or even years before the symptoms begin to appear.
What are the symptoms?
The symptoms of asthma may develop gradually and may not be noticed until a trigger provokes the first severe attack. For example, exposure to an allergen or a respiratory tract infection may cause the following symptoms:
Painless tightening in the chest.
Shortness of breath.
Dry, persistent cough.
Feelings of panic.
These symptoms often become considerably worse at night and in the early hours of the morning.
Some people find that they develop mild wheezing during a common cold or a chest infection, but usually this does not indicate asthma. The main feature that distinguishes asthma from other respiratory conditions is its variability.
If asthma becomes severe, the following symptoms may develop:
Wheezing that is almost inaudible because so little air flows through the airways.
Inability to complete a sentence due to shortness of breath.
Blue lips, tongue, fingers, and toes due to lack of oxygen.
Exhaustion, confusion, and coma.
If you are with someone who is having a severe attack of asthma or your own symptoms continue to worsen, you need to call an ambulance.
How is it diagnosed?
If you have had breathing problems recently but are free of symptoms when you consult the doctor, he or she will ask you to describe your symptoms and will examine you. Your doctor may also arrange for you to have various tests, such as spirometry, to measure how efficiently your lungs work (see Lung function tests). As part of these tests, your doctor may ask you to exercise for a few minutes in an attempt to induce a mild attack of asthma. Less commonly, the doctor will measure how irritable your airways are by getting you to breathe in a small dose of a test chemical. If you do have an asthma attack as a result of these tests, you will be given medication to relieve it.
If you are having a mild attack when you consult your doctor, he or she may measure the speed at which you exhale using a device called a peak flow meter (see Monitoring your asthma) and then ask you to inhale a bronchodilator, which relaxes the airways. Your doctor may be able to diagnose asthma if your peak flow rate increases substantially after you have inhaled the bronchodilator drug.
If you have a severe attack of shortness of breath, you may be treated and sent to hospital for assessment. Once you are admitted to hospital, the oxygen level in your blood will be assessed (see Measuring blood gases), and you may have a chest X-ray to rule out other serious lung disorders, such as a pneumothorax.
If you are diagnosed with asthma, your doctor may suggest that you have further tests at a later date to check for allergies to substances that are known to trigger attacks. If the timing and occurrence of your symptoms suggests that you have occupational asthma, your doctor will ask about substances used in your workplace to try to identify a specific trigger for your asthma.
What is the treatment?
Some people with asthma do not need treatment if they manage to avoid the factors that trigger their symptoms (see Living with asthma). However, there are so many triggers that it is very difficult to avoid them all, and for this reason treatment is often necessary.
Today, asthma attacks can usually be treated with short-acting drugs. In addition, long-term maintenance treatment can prevent asthma attacks developing. The current approach to asthma treatment is to give you the knowledge and confidence to be able to manage the condition yourself on a day-to-day basis, in partnership with your doctor. The most important aspects of controlling your asthma effectively are the careful planning of drug treatment and regular monitoring of your condition.
The aim of all drug treatment is to eliminate symptoms and reduce the frequency and severity of asthma attacks so that visits to an accident and emergency department are no longer needed. Severe, potentially fatal attacks rarely develop without warning. Recognizing a serious change in your condition and taking prompt action by adjusting your treatment or contacting your doctor are essential to prevent an attack occurring.
Types of drugs
The drugs that are used to treat asthma fall into two distinct categories: quick-relief drugs (relievers), which are used to relieve an attack of wheezing; and preventer drugs, which help to prevent attacks occurring. Most relievers are bronchodilators. There are several different types of bronchodilator, all of which relax the muscles that narrow the airways and treat breathing problems as they occur. Relievers are usually effective within a few minutes if they are inhaled, but their effect lasts for only a few hours. They should be used as soon as symptoms develop or, if recommended by your doctor, before you start to exercise.
Most preventers of asthma are corticosteroid drugs (see Corticosteroids for respiratory disease), which slow the production of mucus, reduce inflammation in the airways, and make the airways less likely to narrow when they are exposed to a trigger substance. Non-steroidal preventers, such as sodium cromoglicate and leukotriene antagonist drugs (see Antiallergy drugs), are sometimes used to reduce the allergic response and to prevent narrowing of the airways. This type of treatment must be used on a daily basis and can take several days to become effective.
Both relievers and preventers are usually inhaled from a special device called a metered-dose inhaler, which delivers a fixed dose of the drug. Your doctor will show you how to use an inhaler. For acute asthma attacks, some people find drugs are most effective when inhaled using a spacer attached to the inhaler or through a device called a nebulizer. This device produces a fine mist of drugs to be inhaled through a mouthpiece or face mask (see Taking inhaled asthma drugs). Spacers are also useful if you find it difficult to coordinate releasing the drug and inhaling. Children may need to use spacers.
People with long-term severe asthma may occasionally be given additional preventers in the form of low-dose oral corticosteroids rather than just inhaled drugs. Oral corticosteroids may also be given to relieve severe attacks.
Nowadays, adults with asthma are encouraged to take as much responsibility as possible for managing their condition. Asthma may vary in severity from day to day or over longer periods. For this reason, you and your doctor will probably develop an asthma management plan which helps you to assess your symptoms and make adjustments to your treatment accordingly. The key to controlling asthma is regular monitoring of symptoms and self-assessment using a symptom diary and a peak flow meter, which determines the rate at which you are able to exhale.
As you follow your management plan, your asthma treatment will move up a level, down a level, or stay the same, depending on your most recent symptoms and peak flow readings. A different level of treatment may involve altering a drug dosage; taking the medicine in another way, such as orally instead of by inhaling; taking a different drug; and/or using the treatment more or less frequently. If one level of treatment is not controlling your asthma, you move up to the next level.
If you are an adult newly diagnosed with asthma, treatment may start with a reliever drug only. Preventers may be added gradually if you find that you are using relievers more than a few times a week. Your doctor will closely monitor your progress over a period of time to determine whether your treatment plan needs to be changed. If you use your peak flow meter to monitor your asthma every day, you will get an early warning sign of worsening of your condition and can adapt your treatment in accordance with the prescribed plan. Discuss your treatment plan with your doctor and ensure that you understand it. Your plan should include specific advice on what to do if you experience a severe attack of asthma.
If you have a sudden, severe attack of asthma, you should use your reliever inhaler as instructed by your doctor. If this treatment does not appear to be working, call for an ambulance immediately. If you have been given a reserve supply of corticosteroids as part of your treatment plan, take them as advised by your doctor. You should try to stay calm and sit in a comfortable position. Place your hands on your knees to help to support your back; do not lie down. Try to slow down the rate of your breathing to prevent yourself from becoming exhausted.
In hospital, you will probably be given oxygen and corticosteroids and also bronchodilators at a high dose, either through a nebulizer or using a spacer. On the rare occasions when emergency drug treatment is not immediately effective, mechanical ventilation to force oxygen-enriched air into the lungs may be needed.
What is the prognosis?
The majority of children and adults with asthma are able to lead normal lives if they receive medical advice for their condition and then follow their treatment plans. Asthma that begins during childhood disappears by the age of 20 in at least half of all cases.
Generally, the outlook is excellent for adults who have asthma but are otherwise healthy as long as there is careful monitoring of their condition.
In spite of this encouraging outlook, about 1,200 people in the UK died from severe asthma attacks in 2006. In most cases, the cause of death is a delay in recognizing the severity of an asthma attack and consequently a delay in getting to hospital.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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