"Asthma" comes from the ancient Greek word meaning "panting"and, if you've experienced an asthma attack, you'll understand why. For some, an asthma attack feels as though an elephant is sitting on their chest, while for others breathing becomes so laboured that it’s like trying to suck peanut butter through a straw. So, what is asthma?
Asthma is a long-term (chronic) disease of the respiratory system that affects the tubes carrying air to the lungs.
When we breathe in, air passes through the voice box and down the windpipe (trachea). The windpipe branches into the two main bronchi that take air into the two lungs. These bronchi then divide further becoming smaller and smaller as they take air deeper into the lungs to the point where oxygen passes into the blood stream and carbon dioxide is released and breathed out.
The walls of the bronchi can be divided into four layers:
- The very thin smooth inner lining called the mucosa;
- The layer below this contains mucus-secreting glands;
- The third layer is cartilage which acts like scaffolding holding these tubes open;
- The outer layer is a muscle.
Asthma is characterised by narrowing of the bronchi caused by:
- Swelling of the mucosa;
- Increased sticky mucus or secretions lying in the airways produced by the mucus glands. The swelling and increased secretions are called inflammation;
- Muscles go into spasm. Spasm occurs only when there is inflammation.
When the bronchi become too narrow or are partially obstructed from inflammation and spasm, typical asthma symptoms develop. These include:
- Coughing which often occurs more frequently at night or with activity. It can be dry or wet and is persistent;
- Tightness of the chest with breathing difficulty;
- Shortness of breath, especially after exercise.
Asthma often develops in childhood or during the teens. It’s the most common long-term childhood disease. People with other lung diseases, such as chronic obstructive pulmonary disease (COPD) can also develop asthma. Although it’s not clear exactly what causes asthma, it’s thought to be triggered by an allergy or when the lungs are irritated by something in the air. Taking cough medicine won’t help relieve asthma symptoms.
Robin J Green (PhD), updated July 2007