What is asthma?
Narrowing of the breathing tubes.
Asthma is a condition that affects the breathing tubes (bronchi) in the lung. The breathing tubes are surrounded by muscle which in people with asthma goes into spasm causing the tubes to narrow. This makes it more difficult to get air in and out of the lung. This is called bronchoconstriction. The main feature of asthma is that this spasm comes and goes quite rapidly over time or as a result of treatment. The air moving through these narrow tubes makes a high-pitched noise called a wheeze, which occurs mainly on breathing out. The narrowing of the breathing tubes causes the chest to feel tight and makes the person feel short of breath. These symptoms are often worse at night and wake people up.
Airway hyper-responsiveness (AHR)
One reason the breathing tubes go into spasm is because they are naturally sensitive to irritants that we breathe in. This is why people with asthma are sometimes uncomfortable around perfumes, dust, smoke and strong smells. This twitchiness is called airway hyper responsiveness or AHR. This can be measured by breathing in a chemical which causes the smooth muscle to go into spasm. People with asthma respond at a lower dose than people without asthma.
The muscle spasm is caused by chemicals released from special cells called mast cells which sit next to the smooth muscle in the breathing tube. The spasm is rapidly relieved by drugs called bronchodilators which are usually given in a blue inhaler. The most common form of bronchodilator used is salbutamol. Mast cells release these chemicals because of allergy to otherwise harmless substances that we breathe in, such as pollens, dust mite, pet hairs and fungal spores. Allergy is the most common cause of asthma especially in children. We can measure allergy with skin prick tests or blood tests
Allergy also causes a certain type of white cell, called the eosinophil, to come into the lungs. This process is called inflammation. Inflammation causes the breathing tubes to become blocked with mucus and debris and this problem is not helped by bronchodilators, but needs steroids, usually given in a brown inhaler. Inflammation with eosinophils is often the cause of severe flare ups of asthma (exacerbation). if these are not promptly treated with tablet steroids they can lead to a severe attack of asthma which requires the person to come into hospital to be treated. Another important cause of flare-ups are viral infections that you get when you have a head cold. We can measure inflammation by taking a sample of sputum, or occasionally placing a camera in the lungs to obtain samples directly from the breathing tubes.
Other problems with asthma
The inflammation and AHR that people with asthma suffer from often leads to a chronic dry cough which can be a troublesome symptom. In addition people who have had asthma for a long time can develop a degree of lung damage. This can permanently narrow the breathing tubes leading to constant breathlessness on exercise rather than varying over time. Another form of damage that occurs in people who have had bad asthma for a long time is where the breathing tubes become twisted and dilated. This complication of asthma, which is called bronchiectasis, causes recurrent infections and a tendency to cough up increased amounts of phlegm.
What sort of research do we do?
At Glenfield Hospital we undertake many different types of research into asthma. This includes laboratory research where we work out how mast cells, eosinophils and smooth muscle work. To do this we use blood and lung samples from people with asthma. We hope this will lead to ideas for new types of treatment. We also make as many measurements as we can on people with asthma to work out how the condition affects each individual. This allows us to tailor our treatment to an individual’s particular needs. We also do clinical trials of new types of treatment to try find better ways to help people with asthma have a better quality of life and reduced risk of running into problems in the future. To do all of this we need your help.