Asthma is a common condition that affects the breathing of more than five million UK adults. Even more children get asthma, but a significant proportion grow out of it in their teens.
Someone having an asthma attack often describes a tight feeling in their chest and he or she complains of not being able to breathe in or breathe out as easily as usual. An asthma attack is also often accompanied by coughing and wheezing, and people with asthma find it difficult to exercise, work out and take part in sports when their condition is not under control.
Do we know why people get asthma?
For such a common health breathing problem it is maybe surprising that the medical profession does not yet fully understand why some people are affected but not others. It may be due to a mixture of their genes and the environment they were exposed to in early life, and possibly to viruses and bacteria that have caused infections in their respiratory system. Exactly which genes, environmental factors or infections are involved is still quite a puzzle and we do not really understand the mechanisms through which they lead to asthma.
What do we know about asthma?
It is well established that asthma is due to chronic inflammation of the tissues that line the airways. The respiratory tissues in someone with asthma are oversensitive to substances such as animal dander, flower and tree pollen, dust mite faeces and fungal spores. Being exposed to any of these asthma triggers can set off a sequence of events that leaves the person affected struggling for breath.
An asthma attack can be very frightening, particularly if you have no inhaler available. Anything more than a mild attack can require emergency medical attention. Fortunately, if the asthma can be kept under control using medical treatment and lifestyle changes, the impact of asthma on everyday life can be minimised. It is also reassuring to know that even frequent asthma attacks do not damage the lung tissue in the long term.
What happens during an asthma attack?
In a healthy person, air enters the lungs through the main windpipe, the trachea. It then passes into the bronchi of each lung and on into the smaller bronchioles that form narrower branches as they extend deeper into the lungs. Each one ends at a terminal bronchiole, which opens up into several tiny air sacs. These alveoli are responsible for exchanging oxygen and carbon dioxide between the air inside them and the blood in the capillaries that surround the lung tissue.
In someone with asthma, inflammation in the airways causes the tissue in the walls of the trachea, bronchi and bronchioles to swell and also to produce more fluid and mucus. The larger airways stay open, but can narrow and become clogged with mucus, causing the characteristic wheezing and coughing. However, the smallest bronchioles tend to collapse because they are not supported by the same rigid collagen fibres that are present in the walls of the bronchi and trachea. These smaller airways tend to collapse on breathing out, so someone with asthma often finds it more difficult to breathe out than to breathe in.
What sets off an asthma attack?
Small particles that are produced from other living things – plants and animals – are breathed into the lungs all the time. Several key asthma triggers will set off the wheezing and shortness of breath typical of an asthma attack:
House dust: this is made up largely from dead human skin cells but it also contains house dust mite faeces. These mites can live just about anywhere in the home, particularly in mattresses and bedding, producing faeces constantly
Allergies to animals: particles that form within the fur, feathers, saliva or urine of animals such as cats, dogs and farm animals can trigger an asthma attack
Flower and tree pollen: people with hay fever often have asthma as one of their seasonal symptoms
Foods in the diet: many different foods and some food additives can trigger an allergic response that leads to an asthma attack
The spores from fungi.
How is asthma controlled?
It is possible to help control your asthma and reduce the number of attacks you have by avoiding anything you know is one of your asthma triggers. Working with the windows closed during days when pollen levels are high if you have hay fever-related asthma or avoiding any foods that set off an attack is sensible and relatively easy. Avoiding other triggers, such as house dust, is more difficult.
Most people with asthma need medical treatment and sticking to medical advice about using inhalers can help reduce the severity of individual asthma attacks, and can mean you have fewer attacks too.
Inhalers are available in several different models, including ones that automatically deliver a dose of the drug they contain when you breathe in through the mouthpiece. This draws the drug deep into the lungs. Inhalers contain two types of drugs that can help control asthma:
Drugs that are used in an asthma attack are called relievers. These are taken during an asthma attack to relax the walls of the terminal bronchioles, reducing chest tightness. The most common asthma reliever is salbutamol. This is a powerful bronchodilator but it is also short-acting, so it can be used regularly without causing too many problems
Drugs that are taken regularly to prevent attacks are called preventers. Inhalers that are used to prevent asthma attacks usually contain corticosteroids. These are longer-acting and reduce the level of the inflammatory response in the airways. This makes your airways less sensitive to the asthma triggers you are exposed to in everyday life.