Asthma

YOUR LUNGS ARE LIKE A "TREE"

Your lungs are like a "tree". When you breathe in, air passes into the windpipe, the trunk of the tree. Air passes from the windpipe into two large bronchial tubes (bronchi), one supplying air to each lung. These bronchi are the first "branches" of the tree. They divide into smaller and smaller branches, finally delivering air into tiny air sacs, called alveoli. The alveoli are the "leaves" of the tree. From these alveoli, oxygen is taken from the breathed-in air, and passes into the bloodstream. The oxygen is to be taken to all the or gans of the body.

ASTHMA: A DISEASE OF THE BRANCHES OF THE TREE (BRONCHI)

The bronchi deliver oxyg en to the lungs. Thr oughout the day and night, the width of theses tubes is not fixed, because they are constantly opening and closing. By closing, we mean that the tubes narrow slightly, rather than closing altogether. The tubes tend to be widest at 4pm and narrowest at 4am. In nor mal people, there is very little difference in the width of the tube whether it is open or closed. This means the flow of air to the lungs is virtually the same, day and night.
In people with asthma, this process of opening and closing is exag gerated. The tubes tend to close down more than usual. This makes the bronchi nar rower than usual, and more difficult to br eathe through. This excessive narrowing is caused by inflammation and spasm of the muscle within the tubes. Inflammation and muscle spasm can be triggered by a number of things (see below). The inflammation causes the cells lining the bronchi to produce large amounts of mucus. The mucus can be very thick and, in addition to the muscle spasm, can partially block the bronchi. The end result of this is to narrow the bronchi , making it difficult to breathe i.e. an exacerbation or wor sening of asthma.

WHAT CAUSES ASTHMA?

The cause of asthma is not known. In all people, there are tiny cells in the bronchi that are part of the lung's immune system. In asthmatics, there may be a greater number of these cells than usual, or these cells may be producing more chemicals than usual. This leads to inflammation in the tubes. The reason a person develops asthma is not always known. There are definite genetic factors, so that asthma tends to "run" in families. Some asthmatics are prone to allergy, so that exposure to cer tain things triggers inflammation in the bronchi. These triggers include mites in household dust, smoke, dog and cat hair, tree and grass pollens, deodorants, air freshener sprays, to mention but a few. If these are inhaled from the air, then symptoms develop. Asthmatics that are prone to allergy are called "atopic" asthmatics. Those that are not prone to allergy are called "non-atopic" asthmatics. Atopic people often suffer from hay fever and/or eczema (an allergic skin rash). There are many other things that can trig ger symptoms in an asthmatic. These are discussed in the section on symptoms below.

ASTHMA IS A VERY COMMON ILLNESS

Ireland has the fourth highest number of asthmatics in the world after the UK, Australia and New Zealand, affecting about 300,000 people, to some degree. There are about 5 times as many cases of asthma now in Ireland than there were 30 years ago for causes that are not known. This probably relates to changes in the environment. Asthma is more common in city dwellers. You can develop asthma at any age, from infancy to old age but it is more common in children.

WHAT SYMPTOMS WILL I NOTICE?

There are many different patterns of symptoms in asthma. The usual symptoms are shortness of breath, wheezing, cough and a feeling of tightness in the chest. You may have one or all of these symptoms either all the time to some degree , or have 'flare-ups' every few months that are often confused with chest infections. Wheezing refers to the high-pitched whistling noise heard when air is flowing through narrowed bronchial tubes. Some people can actually hear this themselves, or your doctor may hear it when he listens to your chest. Cough can be dry or productive of small amounts of clear or yellow sputum. When cough is the only symptom, this is called cough variant asthma. Generally speaking when present, symptoms are worse during the night and first thing in the morning. Some people notice that certain things trigger their symptoms, such as inhaling pollen, dog or cat hair, smoke, etc. In others, exercise, even walking, can bring on symptoms (exercise induced asthma). Some asthmatics develop symptoms after taking aspirin or aspirin-like drugs (aspirin sensitive asthma), and these drug should be generally avoided in asthmatics. Betablockers used for angina and high blood pressure and some medications for arthritis or rheumatism should also be avoided. Many asthmatics notice symptoms, or worsening of symptoms, when they get a cold or viral infection. Asthma can be caused or worsened by bad sinusitis causing a post-nasal drip into the back of the thr oat. Therefor e, treatment of sinusitis can sometimes improve or even cure asthma! Some asthmatics have symptoms related to reflux of acid from the stomach into the lungs. This reflux can be silent (no symptoms), or cause heartburn and indigestion. In general, most asthmatics notice their symptoms coming on gradually over a period of time. However, there is a small group of asthmatics whose symptoms come on very suddenly, over a period of hours, and these symptoms can be very severe and frightening. These people have so-called brittle asthma. When symptoms of asthma wor sen, at any time, sometimes causing the sufferer to seek medical advice, this is called an asthma attack, a 'flare-up' or an exacerbation.

HOW DO DOCTORS DIAGNOSE ASTHMA?

Doctors will often be able to diagnose asthma by listening to your symptoms and listening to your chest. No fur ther tests may be required. If there is doubt about the diagnosis, the doctor may give you a small plastic device to use at home called a peak flow meter. This is a device that you blow in to, and it measures flow of air thr ough the bronchial tubes. If there is a decrease in the measurement expected for your age, or if there is a large variability in the measur ements between different times of the day, this suggests that you have asthma. Other special breathing tests may be required, and are performed in a special lung function laboratory in the hospital. When doing these tests, you will be asked to breathe in and out, through a mouth-piece, into a device that measures how narrow your bronchial tubes are. In the same laboratory, skin allergy tests can be performed to assess if you are allergic to cer tain things, suc h as house dust mite and pollens. Blood test and x-rays are sometimes required.

HOW DO DOCTORS TREAT ASTHMA?

Asthma is caused by inflammation and musc le spasm within the bronchi causing them to narrowing. Treatment is therefore aimed at reducing the inflammation and muscle spasm and so reversing the nar rowing. Most medications f or asthma are given through an inhaler whic h delivers the medication straight to the lung. There are many different types of inhaler de vice, and it is important that the inhaler is used correctly and at the appropriate times for successful treatment of asthma. In some cases, tablets may also be used. People with very mild asthma may only need occasional use of an inhaled medication called a bronchodilator. This opens up the tubes for a few hours and gives temporary relief of symptoms (known also as a "reliever"). This is only taken as needed, i.e. w hen symptoms are present. People with moderate or severe asthma will require another inhaler to reduce bronchial inflammation and musc le spasm, and so prevent symptoms. This is an inhaled steroid, and is also known as a "preventer". It must be used regularly, usually twice a day, to be effective, and it is taken even on days when you feel well. These inhalers are safe, and do not cause the problems associated with steroid tablets. The only precaution is to use a mouthwash or brush y our teeth after taking the inhaler, because medication can build up in the throat leading to soreness and hoarseness. Most asthmatics take an inhaled steroid twice a day, and an inhaled bronchodila tor as needed. It is very important to know wha t the inhalers ar e for, when to take them, and how to use them pr operly. If not sure, ask your doctor! Sometimes, tablets are added in if symptoms are not controlled with inhalers. Temporary worsening or "attacks" of asthma are usually treated with a short course of steroid tablets, and often an antibiotic if your doctor thinks that you have a chest infection. A severe attack may need to be treated in hospital. People with hay fever, eczema, sinusitis and acid r eflux will r equire specif ic treatments for these complaints. Nowadays, most asthmatics are well controlled if they take their medication as prescribed. Unfortunately, a few people still die every year , but much less than years ago. This can be prevented by correct use of medication, and early recognition that your symptoms ar e getting worse. It is very important that you see y our doctor if your symptoms are increasing. If in doubt, seek medical advice sooner rather than later!