What is asthma?
Asthma is an allergic condition that affects the respiratory tract. It is long lasting (chronic), however the individual episodes of asthmatic signs and symptoms may be short lived. There is inflammation in the airways, meaning white blood cells have been activated and chemicals involved with immunity (such as histamine) are present in the airways. The airways are also hyperresponsive, which means that they will narrow (bronchoconstriction) with certain triggers that wouldn't cause the airways to narrow in many other unaffected people. There is also an increased amount of mucus in the airways too during an exacerbation of asthma. This causes the typical signs and symptoms of coughing, wheezing, shortness of breath (especially on exertion), and a tightness in the chest.
Asthma is a dynamic disease, meaning that it can vary hugely between people and over time.
Who gets asthma?
Asthma is becoming increasingly common. Studies have calculated that 15 % of children and 7 % of adults suffer from asthma. Prevalence (how common asthma is) varies a lot between countries – New Zealand, Australia, and the UK have high rates, whereas countries like China and Malaysia have low rates.
Asthma is more common in certain groups of people. Asthma, like other allergies, can run in families. This is especially true for asthma which appears in childhood. Although a few genes have been identified which might play a part in asthma, it is likely that many genes are involved, as well as environmental and lifestyle factors. Some people with asthma will have other allergies as well, such as allergic eczema, hives, or hay fever.
It has also been thought that people who live in a cleaner environment develop more allergies. This is because exposure to bacterial and viral infections can cause a change in the composition of our immune system – more of certain types of white blood cells are produced if we are not exposed to infections. These white blood cells are known as TH2 cells, and through a variety of chemical reactions, can increase the chances of getting allergies. TH2 cells can cause changes in other white blood cells, known as B cells. TH2 cells can stimulate B cells to make IgE. IgE is an immune chemical that binds to allergens (foreign chemicals that cause allergic symptoms) and stimulates mast cells (another type of white blood cell) to make histamine. Histamine, and other related chemicals, cause the symptoms of allergy, including the signs and symptoms of asthma.
Exposure to cigarette smoke and other forms of air pollution have also been linked with asthma. In addition, chemicals like nitrogen dioxide, ozone, and sulphur dioxide have also been linked to asthma. Changes and interactions between airborne pollution and the weather can cause exacerbations of asthmatic symptoms. Smoking during pregnancy has been shown to increase the risk of your baby going on to develop asthma.
Occupational asthma and a few other lung conditions (such as pigeon-fancier's lung or black lung disease) can be caused by exposure to airborne dust, pollution, and allergens. It tends to start later on in life, and there may not be any asthma or allergies in the rest of the family.
What are the signs and symptoms of asthma?
During an exacerbation of asthmatic symptoms, signs and symptoms can include coughing, wheezing, shortness of breath and difficulty breathing, and tightness in the chest. These can first occur at any age. Wheezing is a high or low pitched whistling sound that can be heard when someone suffering from asthma breathes out, it is often polyphonic (composed of many different tones).
The symptoms can be persistent or can only occur at certain times following certain triggers. Asthma with constant symptoms is more common in adults, whereas asthma with episodic symptoms is more common when asthma has started in childhood. Triggers can include cold weather, dust, airborne allergens or air pollution, certain drugs, anxiety or stress, or exercise.
The signs and symptoms of asthma can vary through the day. Symptoms may be much worse at night or the early hours of the morning and you may be kept awake by coughing.
An asthma attack is a dangerous exacerbation of asthma. Signs and symptoms include very fast and heavy breathing, an inflated chest, sweating, and a fast heartbeat. If you see the nail beds or lips turn blue, it means that the asthma attack is very severe. Slow breathing and no breathing sounds are very ominous signs.
What happens during asthma?
There are two phases in asthma – the early reaction and the late reaction. The early reaction is caused by an inhaled allergen triggering the immune system. The allergen interacts with IgE, a chemical involved with the immune system. IgE triggers mast cells, which are a type of white blood cell also involved with immunity. These mast cells make histamine and a few other chemicals which causes the symptoms of asthma. Histamine causes the muscles surrounding the airways to contract, thus narrowing the airways and causing a wheeze and shortness of breath. The airways also produce more mucus. Blood vessels in the walls of the airways can become leaky, and fluid can leak into the walls of the airways – this can also further narrow the airways. This reaction is short lived, and can last from a few minutes to an hour or a little more.
In the late reaction, different types of white blood cell arrive and cause further inflammation and further symptoms. This reaction lasts longer than the early reaction, lasting up to several hours.
How can asthma be diagnosed?
Talk to your doctor about your own or your child's symptoms. Your doctor will come up with a list of possible conditions you or your child may have. Your doctor may need to do additional tests to aid or confirm a diagnosis. Additional tests may also be needed to rule out other lung conditions.
A classic feature of asthma is the variation in the airways and symptoms over the day. Symptoms may keep you or your child awake at night or the early hours of the morning, and tend to be worse in the early morning. You or your child may be asked to do a peak flow test – this involves breathing as fast and hard as possible into a tube. Peak flow, or peak expiratory flow, tells you how well you can breathe air out. Your doctor may give you one to use at home, and may ask you to use it multiple times a day to see if there is any variation over one day. Peak flow meters are also extremely useful in the management of asthma, in order to examine whether treatments are having any effect.
You may also be asked for additional lung function tests. This is done using a machine called a spirometer. Spirometry can measure many different aspects of lung function, but the one of importance in asthma is known as FEV1/FVC. This compares the amount of air you can force out of your lungs in one second with the amount of air you can force out of your lungs in total. FEV1, which measure the amount of air you can breathe out in one second, can also be useful. If you look at the trace on a spirometer, you should see a rise at a constant slope, followed by a fall, which starts steep but ends shallow. This is a sign that your airways are not letting air in and out as efficiently as they should.
You or your child may be given a bronchodilator (a drug which makes your airways wider), and may then be given a peak expiratory flow test or spirometry tests again. If there is more than a 15 % improvement, there is a good chance you or your child will have asthma.
Other tests might also be necessary if peak flow measurements or spirometry do not lead to any conclusions. You or your child may be given an exercise test, or may be given a small amount of allergen, histamine, or methacholine to see if the airways narrow with these triggers.
How can asthma be managed?
You have to realise that a large part of managing your asthma is going to be your responsibility. Your doctor will explain to you the nature of asthma and how to deal with asthma. You or your child's asthma and lung function will also need monitoring regularly, either by peak flow or by spirometry. Peak flow measurements are quick and easy to do, and you can do it at home. Spirometry might require you to see your doctor.
It is important that you avoid any factors that make your symptoms worse. This might involve avoiding animals or pets, or avoiding dusty places or places with lots of air pollution. Asthma can be triggered by a mould or house dust mite allergy as well – both of these organisms can be removed by reducing the humidity of your house and cleaning regularly. If your child suffers from asthma when he or she is doing exercise, you might need to explain this to school so they can have special provisions made. Avoiding the cold weather is difficult – wear lots of layers during the cold months. Central heating can encourage growth of moulds and house dust mite colonies, so this might not be a great idea if you or your child has a mould allergy or a house dust mite allergy.
There are also medications available to help you out. Inhalers are given out by prescription by your doctor.
You are most likely to be given the "blue" inhaler first. This is likely to contain terbutaline or salbutamol, which are beta-2 adrenergic agonists. This means they act on the nervous system to relax the muscles around your airways and allow your airways to open up again. One puff of this inhaler should be taken whenever necessary, and the effects can last 3 – 4 hours. You might need to take the blue inhaler with you when you are out or if you go for exercise in case your symptoms appear.
If you still require more medication for symptoms of asthma, you may be given the "brown" inhaler. This contains a corticosteroid, which stops some important immune chemicals being produced (these chemicals are leukotrienes and prostraglandins). These chemicals can worsen symptoms by making blood vessels wider (vasodilation) and leaky, and can attract other white blood cells to the area, making symptoms worse. Examples of corticosteroids used for treating asthma symptoms are beclometasone dipropionate and budesonide. These drugs should be taken twice a day, and you should continue using the blue inhaler as needed.
Should you still require medication, your doctor may decide to add a long-acting beta-2 adrenergic agonist to your plan. This group includes drugs like salmeterol and formoterol, and are the "green" inhalers. They provide relief for approximately 12 hours. You should still continue using the brown and blue inhalers too. The effects of the green inhaler can last the whole night and might be the key to a good night's sleep if your symptoms are severe.
If this is still ineffective, your doctor may change the dosage of your brown inhaler, and may also decide to give you other drugs. One class of these other drugs are leukotriene receptor antagonists. These drugs stop additional white blood cells being drawn to the area, and have fewer side effects than steroid drugs. Examples of leukotriene receptor antagonists are montelukast and zafirlukast. Alternatively, you might be given theophylline in a tablet form, which can relax the muscles around your airways and open up your airways. If your asthma symptoms continue to be troublesome, you may be given corticosteroid tablets too.
What is acute severe asthma - asthma attack?
Acute severe asthma is more commonly known as an asthma attack. These are exacerbations of asthma that come on suddenly. Signs and symptoms might include a wheeze, fast breathing, a fast heart rate, altered consciousness, inability to speak or speak full sentences, a silent chest, prolonged expiration (breathing out takes longer than it should), sweating, or numbness.
Signs and symptoms that indicate the asthma attack is moderate include a pulse rate over 110 beats per minute (this can be checked by taking a pulse, for example, on the wrist), fast breathing, inability to speak in full sentences, and a peak expiratory flow reading which is 50 % less than normal. There can also be a loud wheeze. In even more severe asthma attacks, the heart rate can increase to over 120 beats per minute and the breathing rate can increase to over 30 breaths per minute. They might be breathless, agitated, or unable to speak full words. If a person suffering from an asthma attack is breathing extremely slowly, appears confused, exhausted, or unconscious, cannot speak at all, and has blue fingernails or blue lips, it is a sign that the asthma attack is becoming life threatening and needs urgent treatment. If you suspect someone is having an asthma attack, call for an ambulance.
In a severe asthma attack, the peak expiratory flow reading is between 0 % (they are unable to perform the test) and 50 % of what it should be. In this case, doctors will give high-concentration (60 %) oxygen, as well as high dose beta-2 adrenergic agonists like salbutamol. Oral prednisolone or an injection of hydrocortisone, which are corticosteroids, may also be given. Further investigatsions may be done at the hospital. In moderate asthma attacks, the peak expiratory flow is between 51 % and 75 % of what it should be. Here, oxygen, beta-2 adrenergic agonists, and corticosteroids are also given. However, there is less urgency to get to a hospital for additonal tests, and these treatments may completely relieve their symptoms. If the signs and symptoms do not improve after 30 minutes, they may be admitted to a hospital for further investigations and treatments. In mild asthma attacks, peak expiratory flow is over 76 % of what it should be. Here, a beta-2 adrenergic agonist inhaler may be enough to relieve symptoms.
Asthma attacks are rarely fatal if treated adequately.
Medic8® Family Health Guide : Asthma