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Asthma
is a disease of the branches of the windpipe (bronchial
tubes), which carry air in and out of the lungs. There
are two types of asthma -- one is triggered by an allergy
(for example, pollen or mold spores) and the other has
no known cause.
Air
is normally taken into the body through the nose and
windpipe and into the bronchial tubes. At the end of
the tubes are tiny air sacs called alveoli that deliver
fresh air (oxygen) to the blood. The air sacs also collect
stale air (carbon dioxide), which is exhaled out of
the body. During normal breathing, the bands of muscle
surrounding the airways are relaxed and air moves freely.
But during an asthma episode or "attack,"
there are three main changes that stop air from moving
freely into the airways:
The
bands of muscle that surround the airways tighten, causing
them to narrow. This is called a bronchospasm.
The lining of the airways becomes swollen, or inflamed.
The cells that line the airways produce more mucus,
which is thicker than normal.
The narrowed airway traps stale air (carbon dioxide)
in the lungs. As a result, people with asthma feel they
cannot get enough air into the lungs. All of these changes
make breathing difficult.
What
Are the Most Common Symptoms of Asthma?
Symptoms
strike when your airways undergo the three changes described
above. Some people can go a long time between asthma
episodes while others have some symptoms every day.
Common symptoms of asthma include:
Frequent
cough, especially at night
Shortness of breath
Wheezing * Chest tightness, pain, or pressure
Not every person with asthma has the same symptoms in
the same way. You may not have all of these symptoms,
or you may have different symptoms at different times.
Your symptoms may also vary from one asthma episode
to the next. Symptoms may be mild during one asthma
episode and severe during another.
Mild
asthma episodes are generally more common. Usually,
the airways open up within a few minutes to a few hours.
Severe episodes are less common, but last longer and
require immediate medical help. It is important to recognize
and treat even mild symptoms to help you prevent severe
episodes and keep asthma in control.
If
you suffer from allergies and asthma, a reaction to
any offending allergy-causing substance can worsen asthma
symptoms.
What
Are the Early Warning Signs of an Asthma Attack?
Early
warning signs are changes that happen just before or
at the very beginning of an asthma attack. These changes
start before the more prominent symptoms of asthma and
are the earliest signs that a person's asthma is worsening.
Early warning signs and symptoms include:
Frequent
cough, especially at night
Losing your breath easily or shortness of breath
Feeling very tired or weak when exercising, in addition
to wheezing, coughing, or shortness of breath
Decreases or changes in peak expiratory flow, a measurement
of how fast air comes out of your lungs when you exhale
forcefully
Signs of a cold, upper respiratory infections, or allergies
Difficulty sleeping
If you have any of these symptoms, seek treatment as
soon as possible to prevent experiencing a severe asthma
attack.
Who
Gets Asthma?
Anyone
can get asthma, although it tends to run in families.
An estimated 12 million adults and children in the U.S.
have asthma. For unknown reasons, this disease is becoming
more widespread.
What
Causes Asthma?
Asthma
is a problem in the airways, but the exact cause is
unknown. The airways in a person with asthma are very
sensitive and react to many things, or "triggers."
Coming into contact with these triggers often produces
asthma symptoms.
There
are many kinds of asthma triggers. Reactions are different
for each person and vary from time to time. Some people
have many triggers while others have none that they
can identify. One of the most important aspects of asthma
control is avoiding triggers when possible.
Common
asthma triggers include:
Infections:
colds, viruses, flu, sinus infections
Exercise: very common in children*
Weather: cold air, changes in temperature
Tobacco smoke and air pollution
Allergens: substances that cause allergic reactions
in the lungs, including dust mites, pollens, pets, mold
spores, foods, and cockroaches
Dust or items causing dust
Strong odors from chemical products
Strong emotions: things such as anxiety, crying, yelling
or laughing hard
Medicines: including aspirin, ibuprofen and beta blocker
medications used to treat high blood pressure, migraines
or glaucoma
*Note: Exercise is one trigger you should not avoid.
With a good treatment plan, you can exercise as long
and as much as desired, except during an asthma attack.
How Is Asthma Diagnosed?
Doctors
can use a number of tests to diagnose asthma. First,
the doctor reviews your medical history, symptoms, and
general health. Next, tests may be given to check the
general condition of your lungs, including:
Chest
X-ray, in which a picture of the lungs is taken.
Pulmonary function test (spirometry): A test that measures
how much air is in the lungs and how forcefully this
air can be exhaled (lung function). The patient blows
into a tube placed between the lips.
Peak expiratory flow: A test that measures how fast
air can be exhaled from the lungs. The patient blows
into a hand-held device called a peak flow meter.
Methacholine challenge test: A test, more commonly used
in adults, to see if the airways are sensitive to methacholine,
an irritant that tightens the airways.
Other tests, such as allergy tests, blood tests, sinus
X-rays, imaging scans, and stomach and esophageal (throat)
pH tests may also be ordered. These tests can help your
doctor find out if other conditions are affecting your
asthma.
How Is Asthma Treated?
By
avoiding asthma triggers, taking medicines, and carefully
monitoring daily asthma symptoms, asthma attacks can
be avoided or at least limited. Proper use of medicines
is the basis of good asthma control. Medicines used
to treat asthma include bronchodilators, anti-inflammatories,
and leukotriene modifiers.
Bronchodilators
These
medicines relax the muscle bands that tighten around
the airways. This rapidly opens the airways, letting
more air in and out of the lungs and improving breathing.
Bronchodilators
also help clear mucus from the lungs. As the airways
open, the mucus moves more freely and can be coughed
out more easily. In the short-acting form, bronchodilators
relieve or stop asthma symptoms and are very helpful
during an asthma attack. The three main types of bronchodilators
are beta2 agonists, anticholinergics, and theophylline.
Anti-inflammatories
These
medicines, which include inhaled corticosteroids such
as Advair, Flovent, Beclovent, reduce swelling and mucus
production in the airways. As a result, airways are
less sensitive and less likely to react to triggers.
Anti-inflammatories are taken daily for several weeks
before they begin to control asthma. These medicines
lead to fewer symptoms, better airflow, less sensitive
airways, less airway damage, and fewer asthma episodes.
If taken every day, they can control or prevent asthma
symptoms.
Leukotriene
modifiers
Leukotriene
modifiers are newer asthma drugs. They include Zyflo,
Accolate, and Singulair.
Leukotrienes
are chemicals that occur naturally in our bodies and
cause tightening of airway muscles and production of
mucus and fluid. Leukotriene modifiers work by limiting
these reactions, improving airflow and reducing asthma
symptoms. They are taken as pills one to four times
a day and decrease the need for other asthma medications.
The
most common side effects are headache and nausea. Leukotriene
modifiers may change how the body responds to other
drugs, like Coumadin and theophylline. Inform your doctor
about any medications you are taking. Other side effects
may be found as these medications become more widely
used.
Many
asthma medicines are taken using a device called a metered
dose inhaler, a small aerosol canister in a plastic
container that releases a burst of medication when pressed
down from the top.
Several
medicines can also be taken as a powder inhaled through
the mouth from a device called a dry powder inhaler.
Asthma medicines can also be taken as vapors, pills,
liquids, and shots.
It's
also important to keep track of how well your lungs
are functioning. Asthma symptoms are monitored using
a peak flow meter -- a device that measures how fast
air comes out of your lungs when you exhale forcefully.
This measurement is called peak expiratory flow (PEF)
and is calculated in liters per minute.
The
meter can alert you to changes in the airways that may
be a sign of worsening asthma. By taking daily peak
flow readings you can learn when to adjust medications
to keep asthma under good control. Your doctor can also
use this information to adjust your treatment plan.
Can
Asthma Be Cured?
There's
no cure for asthma, but it can be treated and controlled.
In most cases, people with asthma can live free of symptoms
by following their treatment plan.
What
Research Is Being Done on Asthma?
There
are many people studying asthma and how it can be controlled.
A recent study by the National Institute of Allergy
and Infectious Diseases found that cockroaches are a
leading asthma trigger among children in inner-city
areas. Recent studies have also focused on asthma in
the elderly and pregnant women.
Reviewed
by the doctors at The Cleveland Clinic Department of
Pulmonary, Allergy and Critical Care Medicine.
Edited
by Charlotte E. Grayson, MD, Feb. 2004, WebMD.
Portions
of this page © The Cleveland Clinic 2000-2004
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