What is Asthma
Asthma is a condition that affects the airways - the small tubes that carry air in and out of the lungs. Asthma is a common disease. In Hong Kong, it is estimated that around 10% of children and 5% of adults have experienced symptoms of asthma. Asthma is not infectious. It is found to be more related to genetic factors and the environment.
When a person with asthma comes into contact with something that irritates their airways (an asthma trigger), the muscles around the walls of the airways tighten so that the airways become narrower and the lining of the airways becomes inflamed and starts to swell. Sometimes, sticky mucus or phlegm builds up, which can further narrow the airways.
These reactions cause the airways to become narrower and irritated - making it difficult to breath and leading to symptoms of asthma.
It's difficult to say for sure what causes asthma
What we do know is that you're more likely to develop asthma if you have a family history of asthma, eczema or allergies. It's likely that this family history, combined with certain environmental factors, influences whether or not someone develops asthma.
Many aspects of modern lifestyles - such as changes in housing and diet and a more hygienic environment - may have contributed to the rise in asthma over the past few decades. Environmental pollution can make asthma symptoms worse and may play a part in causing some asthma
Research has shown that smoking during pregnancy significantly increases the risk of a child developing asthma. Similarly, children whose parents smoke are more likely to develop asthma.
There may not be complete cure for asthma but with proper care, and by following a doctor’s prescription, patients can manage the disease and lead a normal life, just as many Olympic medalists who are asthmatics did.
Symptoms of asthma
The usual symptoms of asthma are
- Persistent or chronic cough (especially at night, during seasonal changes, a few weeks after a flu, during or after exercis
- Wheeze (a whistling sound when breathing ou
- Breathlessness, difficulty breathing or tightness in chest
Not everyone will get all of these symptoms. Some people experience them from time to time; a few people may experience these symptoms all the time.
A spirometry test measures the volume of air that you are able to expel from the lungs after taking a full breath in. This is done by a technician or a specialist nurse trained to carry out this test.
Your age, height and gender will be entered into the machine (a small electronic device) first so that predicted spirometry values can be made. You then breathe in fully, seal your lips around the mouthpiece of the spirometer and blow out as fast and as far as you can until your lungs are completely empty. This can take several seconds. You may also be asked to breathe in fully and then breathe out slowly as far as you can. Various readings can then be taken and compared with the predicted values. Spirometry is a safe, low-risk test and is usually recommended by a GP or respiratory specialist. It is the best single diagnostic test for people with airflow limitation.
When you do the test, a value is calculated for the amount of air you can blow out in one second (this is the Forced Expiratory Volume or FEV1). This is then divided by the total amount of air blown out until all air is expired (known as the Forced Vital Capacity or FVC). The results can be discussed with your doctor or asthma nurse. This is then expressed as a percentage value.
A spirometry reading usually shows one of four main patterns:
- An obstructive pattern
- A restrictive pattern
- A combined obstructive/restrictive pattern.
Normal readings vary, depending on your age, size and gender. The range of normal readings is published on a chart and doctors and nurses refer to the chart when they check your spirometry readings.
If your airways are narrowed, then the amount of air that you blow out quickly is reduced. So your FEV1 is reduced and the ratio FEV1/FVC is lower than normal. This is an obstructive pattern of spirometry. The main conditions that cause this pattern are asthma and chronic obstructive pulmonary disease (COPD). So spirometry can help to diagnose these conditions.
Before carrying out this test, you may receive some instructions from your doctor, nurse or hospital department that will be carrying out the test. They may include advice on omitting your reliever inhaler for a set time before the test (several hours or more depending on the inhaler). It is recommended that you don't have alcohol, a heavy meal, or do vigorous exercise for a few hours prior to the test. Ideally, you should not smoke for 24 hours before the test.