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Lungs and bronchial tree

Asthma is a common lung disease. In a person with asthma, the airways narrow as a result of inflammation within the airway wall, when exposed to different factors, or triggers. As such, individuals with asthma develop symptoms of widespread and variable airflow obstruction. These events can often reverse spontaneously or with appropriate medication.

What is going on in the body? 
In a person with asthma, the airways are narrow as a result of ongoing irritation. During an asthma flare-up, muscles surrounding the airway tubes, or bronchi, tighten. This is the protective way the body traps unwanted particles in the lungs. Asthma causes this normal protective action to be exaggerated. The reaction in the lungs is out of proportion to the amount of stimulation experienced. Airways with asthma tighten so much that breathing becomes difficult.

During an asthma flare-up, the inflammation and tightening in the airways increases, trapping air in the lungs. The person cannot take in a full breath and feels short of breath. Increased narrowing of the airway tubes also causes wheezing, a squeaking sound that can be heard when the person exhales.

The body normally makes mucous to line the bronchial tubes in the lungs. Mucous helps trap and destroy unwanted particles in the airways. In a person with asthma, the overreaction to stimuli causes excess mucous to form in the lungs.

Sometimes the airway overreaction causes swelling throughout the entire bronchial tube. The opening in the centre of the tube then becomes smaller and breathing becomes more difficult. Breathing takes much more effort than usual, and this often causes chest tightness.

When the muscles relax, the bronchial tubes return to a near-normal size. Asthma symptoms then resolve and breathing becomes easier.

What are the signs and symptoms of the disease? 
The main symptoms of asthma are: Some people have all of these asthma symptoms. Others have just a few or only one. Symptoms often get worse in the early morning and during the night. The severity of symptoms often varies from person to person and from one asthma flare-up to another.

In very severe asthma attacks, a person can be so short of breath that he or she cannot breathe without significant help. More commonly, a person experiences a mild, persistent, dry cough and occasional wheezing. Often there are provoking factors, or triggers, that cause asthma symptoms.

Triggers differ from person to person. Asthma triggers include:
  • cold and dry air and wind
  • dust and dust mites
  • pollen
  • mould
  • smoke inhalation
  • indoor and outdoor pollution from exposure to fumes, paint, fireplace smoke, or perfume
  • heartburn
  • medication allergies
  • allergies to food, such as peanuts, or to foods with sulphites, such as beer, wine, processed foods, and seafood
  • pets with fur or feathers
  • stress
  • hormonal changes resulting from pregnancy or menstruation
  • exercise
  • viral infections, such as a cold or flu
What are the causes and risks of the disease? 
Asthma is caused by an immune system response. The immune system overreacts to triggers and causes the airways to become inflamed and tight. Asthma is more common in children who were underweight at birth and those who live in polluted areas. A recent study also showed that the risk of asthma is one and a half times greater in children who were given formula than in those who were breast-fed as infants.

Another study of 1,000 children over 6 years of age compared those who had attended day care before they were 6 months old with those who had not. The children who had attended day care as infants were only half as likely to develop asthma as the group who had not attended day care in their first 6 months of life.

What can be done to prevent the disease? 
There are no immunisations or preventive treatments for asthma. The best prevention is to avoid known triggers. Someone with asthma may find that strong perfume or potpourri makes symptoms worse. If so, avoiding these items may prevent a flare-up. A basic premise is that if you can see or smell it in the air, it can irritate your lungs and make asthma worse. Avoiding triggers is the key to preventing flare-ups. People with asthma definitely should not smoke or be around people who smoke. Working in areas with excessive dust or fumes from manufacturing plastics should also be avoided.

How is the disease diagnosed? 
Asthma is diagnosed primarily by a history of symptoms, such as coughing or wheezing, that occur with physical activity or as a result of exposure to triggers. Pulmonary function tests are simple breathing tests that are often used to measure breathing limitations. Sometimes chest X-rays can show air trapped in the lungs. This occurs in long-term asthma.

However, chest X-rays and pulmonary function tests sometimes don't show the usual changes of asthma, even though the person has the disease. In those situations, a histamine challenge test or methacholine challenge test can be used.

What are the long-term effects of the disease? 
Asthma is characterised by periodic flare-ups, or periods in which symptoms become severe. The flare-ups alternate with periods in which the breathing returns to a near-normal state. Over many years, this pattern can continue without the person getting dramatically worse. In some people, asthma flare-ups increase as they get older. In older adults with asthma, the lungs sometimes retain extra air and cause ongoing shortness of breath.

Some children outgrow asthma. Sometimes symptoms stop and asthma disappears as they grow up. This occurs because the anatomy of the lungs and bronchial tubes changes as they mature. Occasionally an adult who never had asthma before can get asthma after severe bronchitis or pneumonia. This condition can last for a year or 2 and then gradually go away completely. Triggers such as exercise, exposure to fumes and cigarette smoke, or respiratory infections such as colds or flu can cause asthma flare-ups. Asthma is not directly inherited, although it does tend to run in families.

When asthma is poorly treated over a long period of time, a condition called airway remodelling occurs. This is the permanent airway blockage caused by long-term inflammation. These structural changes are not completely reversible, even with treatment.

What are the risks to others? 
Asthma is not contagious and poses no risk to others.

What are the treatments for the disease? 
Successful treatment of asthma involves 2 important factors:
  • avoiding known irritants or triggers
  • taking medications to reduce airway inflammation
Irritants in the air are the main asthma triggers. Avoiding known irritants is key to controlling asthma. Avoid anything that one can see or smell in the air, especially cigarette smoke, dust, strong perfumes, and strong chemical odours, such as household cleaners.

Many people with asthma also have allergies. Allergic reactions can trigger an asthma flare-up. Avoiding things that cause the allergies, called allergens, is important. Many people continue to have asthma problems, even though they try to avoid irritants and allergens.

Two types of medications are used to treat asthma:
  • relievers
  • preventers
Since inflammation is a primary factor of asthma, anti-inflammatory medications are often used to maintain long-term control. This is the first line of treatment after trigger avoidance. Established treatment guidelines recommend that anyone with persistent asthma be treated with an inhaled corticosteroid for long-term control. Inhaled corticosteroids, such as budesonide, beclomethasone and fluticasone work in the lungs to help reduce inflammation.

Oral corticosteroids such as prednisone, prednisolone, or hydrocortisone, are used for asthma control when significant inflammation is present. Use of these medications for a short period of time dramatically reduces inflammation and swelling. The bronchial tubes can then open further and breathing becomes easier. However, long-term use of oral corticosteroids can cause significant side effects. Side effects are less common with inhaled corticosteroids, since less medication is absorbed into the bloodstream through the lungs.

Theophylline, oral corticosteroids, long-acting inhaled beta-2 agonists, and leukotriene modifiers are other types of controller medications that are used when inhaled corticosteroids alone do not work. Leukotriene modifiers are new types of oral medication that work differently than corticosteroids to block the chemicals that start the inflammation process. For many people, the controller medications are very effective and rarely cause side effects.

Long-acting inhaled beta-2 agonists, such as salmeterol, may also be used on a regular basis to relax the airways. A person usually inhales 2 puffs twice a day to relax bronchial tubes and reduce the need for inhaled short acting bronchodilators.

Reliever medications prevent or help reduce the tightening of the muscles around the bronchial tubes, called bronchoconstriction. Everyone with asthma should keep a short-acting inhaled beta-2 agonist, their quick- relief or rescue medication, on hand for flare-ups.

Beta-2 agonists are also known as bronchodilators, for example; salbutamol and terbutaline. They are usually taken through a metered dose inhaler or nebuliser, but they are also available in tablet and liquid forms. A common example is the medication salbutamol. Sometimes ipratropium bromide is also used for quick relief of an asthma flare-up. Oral medications such as theophylline and beta-2 agonists can also help open up breathing passages, but they do not work quickly enough to relieve an acute flare-up.

What are the side effects of the treatments? 
When taking beta-2 agonists, a person may feel a bit jittery, as if drinking too much coffee. The individual may have a rapid heart rate, mild shakiness in the hands, and trouble sleeping. This passes when the medication wears off. Overuse of beta-2 agonists can lead to serious arrhythmias, or irregular heartbeats.

Corticosteroids have few side effects when given by inhaler. One common side effect of inhaled corticosteroids is a yeast infection in the mouth called oral thrush. Two recent studies have shown that the benefits of inhaled steroids in children significantly outweigh the risks. Children who were on inhaled steroids were much less likely to be taken to the emergency department or need treatment with more powerful medications. Although there was an initial lag in growth in children taking inhaled steroids, the lag quickly disappeared, and there was no measurable difference in adult height.

When taken as tablets or liquid, corticosteroids may cause a variety of side effects, particularly when used long term. Water retention, swelling, and increased blood sugar levels can occur. An individual should talk to his or her doctor about any side effects. If corticosteroid treatment needs to be stopped, the doctor will work with the individual to develop a plan for gradually tapering off the medication.

What happens after treatment for the disease? 
Effective treatment of asthma reduces inflammation and tightening, bringing relief of symptoms. Medications do not make the underlying airway tightening and inflammation go away; they simply control it. Successful treatment allows people with asthma to enjoy a full life without significant breathing problems.

How is the disease monitored? 
A person with asthma needs to keep track of symptoms with an asthma diary, and should talk with their doctor about having a Asthma Action Plan. If there is an increase in shortness of breath, coughing, or wheezing, it is important to notify your doctor. Medication may need to be changed.

An individual with asthma can monitor breathing at home with a device called a peak flow meter. Some people use peak flow meters every day and keep a record in their asthma diary. Looking for patterns can show how changes in symptoms affect breathing ability. Sometimes airway changes show up on a peak flow meter before symptoms are even felt. This measurement is useful for both the person with asthma and the doctor as they work together to plan treatment.

Periodic pulmonary function testing allows very specific measurements to be done and helps guide the doctor in prescribing medications.

A yearly chest X-ray is not necessary but it is often done during an initial evaluation of a person with asthma.

Author: Nina Sherak, MS, CHES
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 20/09/2004
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.

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