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Asthma

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Asthma is one of the diseases that doctors have trouble defining, but recognise when we see it. Physically, asthma is narrowing of the airways (the air passages in the lung). When these airways are narrowed they obstruct air flow in and out of the lung, making it harder to breathe. (It is actually harder to breathe out than in with asthma and other obstructive diseases; many of the problems asthmatics have are caused by not being able to exhale properly, which makes it hard for the body to get rid of carbon dioxide.) Unlike other obstructive-airway diseases such as emphysema, the narrowing of asthma can resolve, either by itself or with treatment. Asthma can be very mild and resolve without treatment, but people can and occasionally do die of status asthmaticus (severe asthma with almost continuous airway obstruction).

Asthma is also known as reactive airway disease. This is because airway narrowing often occurs as a reaction to an irritant such as chemical fumes, dust, or airborne allergens. Tobacco smoke is a notorious, and completely avoidable, cause of airway narrowing, but any other inhaled allergen -- weed, grass, tree, and flower pollens, indoor and outdoor molds, insect droppings, and animal dander, among others -- can cause airway inflammation and narrowing. (These are the same allergens that cause allergic rhinitis, and you can reduce your exposure to these allergens just as you would to avoid allergic rhinitis. Viral infections can also trigger asthma attacks by inflaming the airways; some patients have their attacks mainly or only after a viral cold. Some people have asthma attacks with no apparent triggers. There are also people whose asthma attacks are triggered by moderate or vigorous exercise. These attacks can be disconcerting if not disabling, but can often be prevented by taking a bronchodilator before exercising vigorously. Many well-known athletes (including Jackie Joyner-Kersee and Amy Van Dyken) have exercise-induced asthma, and their asthma does not affect their athletic performance as long as they use their medications properly.

Treatment of Asthma

Treating asthma is largely a matter of reducing the narrowing in the airways, which allows easier air movement. This can be done by dilating (widening) the airways, and by reducing inflammation in the airway walls.

A common way for you and your doctor to measure how well you are breathing normally or during an attack is the peak flow meter. This gadget measures how fast you can exhale; since the airway narrowing of asthma affects expiration more than inhalation, the peak expiratory flow, or PEF, , can tell you how severe the inflammation is. Your doctor may recommend a peak flow meter to you, and show you how to use it and what flow rates are signs of impending trouble. In some cases (usually with experienced patients or parents) your doctor may suggest different or additional medicines for different peak flow rates.

Trouble breathing is, of course, a sign of worsening asthma. An earlier sign in many patients is a cough that worsens or persists for a while, although this could be a simple cold as well. I try to listen to the lungs of any known asthmatic with a persistent cough, since the characteristic wheeze often cannot be heard without a stethescope. A patient with asthma who is having trouble talking is having a lot of trouble moving air, and needs to be seen by a doctor immediately. Again, your doctor can review other danger signs with you.

Bronchodilators

The fastest way to relieve an asthma attack is with medicine that makes the airways widen; these medicines are known as bronchodilators. Your body can do this by itself by releasing adrenaline, or epinephrine; this not only cause your heart to pump faster and stronger, but also makes the airways widen to allow more air to pass (this happens even if you are not an asthmatic -- it's part of the "fight or flight" response to danger that's built into all of us).

However, speeding up your heart isn't absolutely necessary in treating an asthma attack, and may even be harmful in some cases (although an injection of epinephrine is a perfectly good emergency treatment for many asthmatics who cannot breathe well during an attack). For routine and urgent cases, we try to use medicines similar to epinephrine that widen the airways but do not speed up the heart as much as epinephrine. The most commonly used medicine of this sort is albuterol, which is chemically similar to epinephrine but has much less effect on the heart than epinephrine does. (Note, though, that albuterol will speed up the heart to some extent -- and that it should not be used at the same time as other similar medicines, including most over-the-counter decongestants and cold medicines, unless your doctor tells you to do so.)

Albuterol comes in several different forms. It can be given orally, as a syrup (for small children) or pills (immediate or time-release), but albuterol doesn't work all that well if it's taken by mouth. It can also be inhaled, from a pocket-size metered-dose inhaler (MDI) or from a nebulizer which makes a fine mist out of the liquid solution. Inhaled albuterol doesn't have quite as much heart-speeding effect as oral albuterol, but it also works a lot faster than oral albuterol.

There are bronchodilators on the market that are similar to albuterol but act more slowly. These are often used for "maintaining" asthmatics who are relatively well-controlled. Some of these medicines will NOT work fast enough to stop a severe asthma attack. If you are on one of these slow-acting bronchodilators, be sure to ask your doctor about what to do differently in an emergency.

In the past, theophylline was used routinely as a bronchodilator for asthmatics. Theophylline is chemically similar to caffeine, and has the same stimulant effects; both theophylline and caffeine (to a lesser extent -- don't pig out on coffee to treat your asthma) will help open up air passages, although we're not completely sure about how they work. Theophylline can be given orally or through an IV. Albuterol and epinephrine work faster than theophylline in most patients, and often with fewer side effects, so at present theophylline is not widely used.

Steroids

Steroids, which are hormones normally produced by your body, help regulate many bodily functions including inflammation. Giving extra steroids for a short period of time may help reduce inflammation; in particular, steroids can help open an asthmatic patient's airways by reducing the inflammation in the airway walls. Other steroid hormones help regulate such things as reproduction, blood pressure, and mineral balances (like sodium and potassium, which are crucial to many important functions) as well as body development and growth.

Steroids have their drawbacks. Your body must make steroids all the time for many processes to work right. If you take steroids for too long, your steroid-making system will think it's not needed any more and shut down, and if you then face a situation where you need the steroids (any kind of stress, including surgery) all sorts of things can go wrong -- like your blood pressure, to take one example.

When we give steroids to asthmatics, we can do so orally (very convenient), through an IV line (which actually doesn't work any faster than oral in many patients -- but if you are having so much trouble breathing that you can't take the time to swallow, it might be useful), or by inhalation (either with a nebulizer or with a metered-dose inhaler). Inhaled steroids are nice for long-term treatment of asthmatics because the medicine tends to stay in the lungs, and so the side effects on the rest of the body aren't as bad. In more severe asthmatics we will occasionally give 3-5 day "pulse" treatments with oral steroids. If we give steroids for longer than that the body starts getting lazy about making its own, and so we have to "taper" the dose over a few days at the end. Even so, some bad asthmatics may become steroid-dependent if they have to take steroids often enough. (On the other hand, if you're an asthmatic who needs steroids now, you may not have the luxury of worrying about the long-term effects until your breathing is better.)

Mast Cell Stabilizers

The mast cells are part of the lining of the air passages; they are part of your immune system, reacting immediately to allergens and other obnoxious stimuli. The mast cells release many different substances when they are stimulated, including histamine, which is a chemical responsible for most allergic reactions including the airway inflammation of asthma.

Cromolyn is a drug that "stabilizes" airway mast cells, making them less prone to releasing histamine and other substances in response to allergens. This makes cromolyn a good drug for helping to prevent asthma attacks, or at least making them less severe if they occur. The stabilizing effect seems to help with exercise-induced asthma as well. There are other mast-cell stabilizers available, including nedocromil, which have similar uses. These medicines must be inhaled so that they get to the airway walls properly -- they do not work if swallowed.

To repeat: cromolyn does not relieve an asthma attack in progress. It only helps prevent them -- and it works best if and only if you use it regularly.

Leukotriene Esterase Inhibitors

Leukotriene esterase is an enzyme that is part of our bodies' immune system, and which helps inflammation happens. Drugs such as zafirlukast and montelukast block this enzyme and so make inflammation less likely to happen. In this respect they are like cromolyn, but their mechanism is very different. Like cromolyn, these medicines must be taken regularly, and they will not relieve an asthma attack in progress -- you will still need the fast-acting bronchodilators.


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PLEASE NOTE: As with all of this Web site, I try to give general answers to common questions my patients and their parents ask me in my (real) office. If you have specific questions about your child you must ask your child's regular doctor. No doctor can give completely accurate advice about a particular child without knowing and examining that child. I will be happy to try and answer general questions about children's health, but unless your child is a regular patient of mine I cannot give you specific advice.

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Copyright © 1998, 2001, 2007, 2011, 2013 Vinay N. Reddy, M.D. All rights reserved.
Written 06/22/98; last revised 09/12/13 counter