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A Basic Understanding of Asthma

The impact of asthma on a person's life can be immense. Asthma is often a life long condition that may affect anything from one's performance at school, to exclusion from certain vocations. Asthma affects 5.2 million people in the UK (1). The good news is that today asthma can be well-controlled, allowing asthmatics to lead relatively normal lives.

What is asthma?

Asthma is an incurable (though, some children do seem to grow out of the condition) and chronic condition that affects the smaller airways in the lungs. The small airways swell in response to certain triggers, known as allergens.

Allergens may include pollen, dust mites, fumes, certain medications, and even exercise. Someone who suffers from asthma responds to various triggers with the following reactions:

Reversible narrowing of the small airways
Excessive mucus production inside the small airways

These two factors create resistance to air flow and present with some or all of the following symptoms:

Cough
Breathlessness
Wheezing
Chest tightness

What causes asthma?

Asthma is thought to be an autoimmune condition; this is where the immune system overreacts to certain triggers causing inflammation in the small airways. Factors such as family history, lifestyle choices and environmental factors are also thought to play an important role.

One of the most talked about theories for the cause of asthma is the hygiene hypothesis. According to this theory, our clean and relatively germ free environments sensitise the immune system to relatively trivial everyday allergens. This is speculated as being a possible explanation why asthma is far more common in the “developed” world.

Who gets asthma?

Asthma affect children and adults, though is more common between the age groups 5 – 30 years old. There also seems to be slightly more boys affected than girls; this is a trend reverses later on, however, in adulthood.

Individuals with hay fever or eczema or a family history of these conditions are at a much higher risk of developing asthma themselves. Smokers, or individuals whose mothers smoked during pregnancy, are also at a higher risk of developing asthma (2). There is also good evidence to suggest that children who have been breastfed have a lower incidence of developing asthma.

How is asthma diagnosed?

Asthma cannot be diagnosed with a blood test or a single investigation. GPs or chest physicians usually make the diagnosis from a combination of your history, examination findings and tests such as spirometry. The diagnosis is rarely made below the age of 7, as symptoms such as wheezing and coughing may often be due to successive viral infections, which is common in young children. Additionally, a misdiagnosis at a young age may have lifelong implications.

How is asthma treated?

The treatment of asthma commonly involves the use of inhalers and may also include the use of oral medication. The treatment of asthma revolves around a “step” approach. Each increasing step adds further or increased dose of medication.

This approach to treatment has five steps. Each patient is started on the step most appropriate to the individual's severity of asthma. Treatment is initially reviewed after three months to assess whether the patient is well controlled on their current step. If not, the patient is moved up a step. If the patient is well controlled, however, attempts can be made to drop the patient to lower treatment step. The effectiveness of their new treatment would be evaluated after another three months.

According to the British Thoracic Society (3) good asthma control is assessed on the following criteria:

No daytime symptoms
No night time awakening due to symptoms
No need for rescue medication
No limitation on activity including exercise
Normal lung function
All the above achieved with minimal side effects from treatment

Inhalers

Inhalers can be split broadly into two categories, reliever and preventer inhalers.

Reliever inhalers are used when a patient suffers with a sudden onset of wheezing, breathlessness or cough. It may also be used prior to activities, which normally precipitate symptoms, such as exercise. Examples of reliever inhalers include:

Salbutamol
Terbutaline

Preventer inhalers contain steroids in an aerosol formulation. The introduction of steroid inhalers occurs at step 2. The aims of steroid inhalers are to reduce the inflammation in the lungs, reduce the number of times a reliever inhaler is required, to improve nocturnal symptoms and to reduce progression of the disease. Preventer inhalers are often taken in the morning and before bed. Example of steroid inhalers include:

Clenil
Qvar

Preventer inhalers may also include additional drugs called long acting beta 2 agonists. These are drugs similar to those found in rescue inhalers, but they act over longer periods. For some patients, they reduce the frequency of rescue inhaler use.

Other Medication

Other medication used in asthma, usually added in at steps 3 and 4 include oral medications such as Montelukast and oral theophylline. Montelukast is thought to work by blocking the production of a group of chemicals called leukotrienes. These chemicals are key in the inflammatory process in asthma, which contributes to the narrowing of airways and excessive mucus production. Theophylline works by preventing narrowing of the airways but it also is thought to decrease airway sensitivity to allergens.

Oral Steroids

Oral steroids, in particular prednisolone, are used in acute exacerbations of asthma and the management chronic severe asthma. This is usually offered to patients on step 5. Acute exacerbations, often involve viral chest infections, causing a sudden worsening of patients' asthma control. Oral steroids are potent anti-inflammatory drugs that usually have very minimal side effects when used for short courses (usually high dose for 5 or 7 days). Long-term steroid therapy is generally avoided unless absolutely necessary, as side effects can include osteoporosis, brittle skin and increased weight gain.

Flu Vaccination

Though the flu vaccination doesn't treat asthma directly, it is important that patients with asthma who have been previously admitted to hospital, or who use steroid inhalers or oral steroids, are vaccinated against flu. Steroid use, though important in controlling many asthmatics, does increase the risk of infection, like severe pneumonia secondary to flu. For this reason, getting vaccinated against annual Influenza strains is crucial. Remember Influenza kills thousands of people every year.

Annual Asthma Check

Annual asthma checks are extremely important. As well as assessing control of symptoms, the checks can be used to assess inhaler technique. Poor inhaler technique is a common cause of inadequate asthma control. The annual asthma check can also be used to assess what type of inhaler is best suited to the patient (MDI, breath actuated – see salbutamol). The check often involves spirometry or peak flow assessment. Combined with a history taking of symptoms, this will help assess whether the patient's asthma is being properly managed.

Sources

1 Asthma UK. The Asthma Divide Inequalities in emergency care for people with Asthma in England. Available at: http://www.asthma.org.uk/document.rm?id=322 (Accessed: 1^st March 2010)

2 American Journal of Respiratory care and Critical Care Medicine. Effects of Maternal Smoking during Pregnancy and Environmental Tobacco Smoke on Asthma and Wheezing in Children. Available at: http://ajrccm.atsjournals.org/cgi/content/abstract/163/2/429 (Accessed: 1^st March 2010)

3 The British Thoracic Society Scottish Intercollegiate Guidelines Network. British Guidelines on the Management of Asthma. Available at: http://www.brit-thoracic.org.uk/Portals/0/Clinical%20Information/Asthma/Guidelines/qrg101%20revised%202009.pdf (Accessed: 1^st March 2010)

Author: Dr Shazan Chughtai, MB BS

Editor: Dr Ahmed Farooq, BMedSci, BDS, MJDF (RCS Eng)

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