Medical Guides - Asthma

What is asthma?

Asthma is a condition in which the airways of the lungs become either narrowed or completely blocked, impeding normal breathing. However, in asthma, this obstruction of the lungs is reversible, either spontaneously or with medication,. Asthma is a condition that affects the airways (bronchi and bronchioles) – the small tubes that carry air in and out of the lungs. Lung tissue where gas exchange occurs (the air sacs) are not affected.

Asthma can be very different from one person to another and from one episode (attack) to another. For some, asthma causes only mild symptoms once in a while. For others, every day can be a struggle to breathe. Some asthma attacks last only a few minutes-others go on for days. Similarly severity also varies with some asthma attacks being only mild while others can quickly become life threatening1,2.

How common is asthma?

Asthma is a very common disorder. Asthma affects nearly 12 million people in America and about 5,000 Americans die of asthma each year. Asthma affects more than three million people in the UK, including one in seven school children and one in 25 adults,.

Asthma is generally more common in children than in adults. This is because some children "outgrow" their asthma attacks when they grow up About 50% of children who develop asthma between 2 and 10 years of age will naturally outgrow the attacks. Asthma is the number one reason why children miss school and the leading reason why children are admitted to the hospital4

What causes asthma?

Everyone's airways have the potential for constricting in response to allergens or irritants. However in asthmatics, the airways are oversensitive or hyperreactive,. Hence there is an excessive response to the stimuli leading to obstruction of the airways by one or more of the following mechanisms

  • constriction of the muscles around the airway;

  • inflammation and swelling of the airway; or

  • increased mucus production by glands in the lining of the airways, which clogs the airway (normally the sticky mucus helps to trap small particles therefore helps to clean the airways)


Once the airways have become obstructed, it takes more effort to force air through them, so that breathing becomes more difficult. When air is forced through the constricted airway it can make a whistling or rattling sound (wheezing). Irritation of the airways by excessive mucus can also provoke coughing6.

The irritants and allergens that cause this hypersensitive reaction are called triggers. The most common triggers of asthma are 6,2,.

  • viral respiratory infections, such as influenza (the flu) or bronchitis;

  • bacterial infections, including sinus infections

  • allergic rhinitis

  • irritants, such as pollution, cigarette smoke, perfumes, dust, or chemicals;

  • sudden changes in either temperature or humidity, especially exposure to cold air;

  • allergens, for people with allergies

  • emotional upsets, such as stress; and

  • exercise.


What are the symptoms of asthma?

The most common symptoms of asthma are1,2:

  • Recurrent wheezing (a whistling or hissing sound as you breathe out)

  • Recurrent shortness of breath

  • Recurrent feeling of tightness in the chest

  • A cough that lasts for more than a week


Not all people with asthma wheeze. For some, coughing - especially during the night or after exercise -may be the main symptom.

How is asthma diagnosed?

The aim in diagnosis is to establish that your airflow is significantly limited at times and that this is reversible. Your doctor is likely to do this by asking you to use a peak flow meter which measures the fastest rate at which air comes out of your lungs when you blow into it as hard as you can
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