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ASTHMA
A GROWING PROBLEM
What is Asthma?
• Asthma is a chronic, inflammatory lung disease in which the airways
become blocked or narrowed. These effects are usually temporary,
but they cause shortness of breath, breathing trouble, and other
symptoms. If an asthma episode is severe, a person may need
emergency treatment to restore normal breathing.
• Asthma is characterized by acute episodes in which breathing
becomes more difficult. Typical symptoms of asthma include
wheezing, shortness of breath, chest tightness, and coughing.
People with asthma typically have extra sensitive or
hyperresponsive airways in their lungs. An acute asthma episode
results when trigger substances irritate tissues in the airways,
causing them to become red, swollen, and narrow. The resulting
bronchoconstriction (muscles that encircle the airways tighten or go
into spasm) makes it difficult for the asthma sufferer to take air in
and out of the lungs.
Asthma
Lung
Prevalence of Asthma
• It is this country's most common and costly
illness.
• The prevalence of asthma has been increasing
since the early 1980s across all age, sex and
racial groups. However, the prevalence of
asthma is higher among children than adults,
and higher among blacks than whites.
• An estimated 17 million Americans suffer from
asthma, nearly 5 million are under age 18. It is
the most common chronic childhood disease,
affecting more than one child in 20.
Deaths
• Asthma is the only chronic disease, besides
AIDS and TB, with an increasing death rate.
Each day 14 Americans die from asthma.
• From 1979 to 1992, asthma death rates
increased 58 percent overall. The death rate for
children 19 years and younger increased by 78
percent between 1980 and 1993.
• More females die of asthma than males and
more blacks die of asthma than whites.
• Certain factors indicate that many asthmarelated deaths and hospitalizations are
preventable when asthma is properly managed.
The Costs
• The cost of asthma in 1998 was estimated to be $11.3 billion. Direct
costs accounted for $7.5 billion and indirect costs were $3.8 billion.
Hospitalizations accounted for the single largest portion of the cost.
• Among children ages 5 to 17, asthma is the leading cause of school
absences from a chronic illness. It accounts for an annual loss of
more than 10 million school days per year and more hospitalizations
than any other childhood disease. Children with asthma spend an
estimated 7.3 million days per year restricted to bed.
• For adults, asthma is the fourth leading cause of work loss, resulting
in nine million lost workdays each year.
• Asthma also accounts for about 1.8 million emergency room visits
and 10 million doctor office visits each year.
• Asthma results in about a half million hospitalizations each year.
What Triggers Asthma?
• An asthma episode is triggered by things in the environment. These
triggers vary from person to person, but common ones include cold
air; exercise; allergens (things that cause allergies) such as dust
mites, mold, pollen, animal dander or cockroach debris; and some
types of viral infections.
• It is in the bronchi and bronchioles that asthma has its main effects.
• Here is how the process occurs. When the airways come into
contact with an asthma trigger, the tissue inside the bronchi and
bronchioles becomes inflamed. At the same time, the muscles on
the outside of the airways tighten up (constriction), causing them to
narrow. A thick fluid (mucus) enters the airways, which become
swollen. The breathing passages are narrowed still more, and
breathing is hampered.
Lymphocyte
Lymphocytes produce IGE
and various interleukins.
IGE may be bound to mast
cells or basophils.
If they are produced in the
presence of allergens, they
May bind to the cells and to
the allergen. They release
histamine which causes
inflammation of tissue and
allergy problems. The cells
Also release cytokines,
Interleukins and prostaglandins which attract
eosinophils and other cells.
Eosinophil
Who Gets Asthma?
• The process just described can be normal, up to a point.
Everyone's airways constrict somewhat in response to
irritating substances like dust and mold. But in a person
with asthma, the airways are hyperreactive. This means
that their airways overreact to things that would just be
minor irritants in people without asthma.
• To describe the effects of asthma, some doctors use the
term "twitchy airways." This is a good description of how
the airways of people with asthma are different from
those without the disease.
• People with asthma have too much leukotrienes.
What Are Risk Factors for Asthma?
• Heredity. To some extent, asthma seems to run in families.
• Allergies: For reasons that are not fully known, some people seem
to inherit a tendency to develop allergies. This is not to say that a
parent can pass on a specific type of allergy to a child. In other
words, it doesn't mean that if your mother is allergic to bananas, you
will be too. But you may develop allergies to something else, like
pollen or mold.
• Substances in the environment that cause allergies—things like
dust, mold or pollen—are known as allergens. In a person with
allergies, the body responds to allergens by producing certain kinds
of proteins called immunoglobulin E (IgE) antibodies. Antibodies are
proteins that the body produces to fight off foreign invaders. One
way to test a person for allergies is to perform skin tests with
extracts of the allergens or do blood tests for IgE antibodies to these
allergens.
What Are Some Asthma Triggers?
• Allergens. In many people with asthma, the same substances that
cause allergy symptoms can also trigger an asthma episode. These
allergens may be things that you inhale, such as pollen or dust, or
things that you eat, such as shellfish.
• Tobacco smoke. Smoking and secondhand cigarette smoke.
Studies have shown a clear link between secondhand smoke and
asthma, especially in young people. Passive smoking worsens
asthma in children and teens and may cause up to 26,000 new
cases of asthma each year.
•
Exercise. Exercise—especially in cold air. A form of asthma called
exercise-induced asthma is triggered by physical activity. The kind of
physical activities that can bring on asthma symptoms include not
only exercise, but also laughing, crying, holding one's breath, and
hyperventilating (rapid, shallow breathing).
Common Asthma Triggers
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Dust/Dust Mites
Cockroaches
Mammal fur/saliva/urine
Mold
Pollen
Second hand cigarette smoke
Chemical irritants: Scented products,
fabric finishers
Dust Mites
Dust mites are
microscopic, insect-like
creatures that live in
bedding, carpets and
upholstered furniture. The
waste they produce
causes allergic symptoms
in 30-60 million
Americans. Pillows
and mattresses are a
virtual paradise for dust
mites because they thrive
in warm, humid conditions
while gorging themselves
on shed human skin cells.
Cockroaches
• Cockroaches
Many people with
asthma are allergic to
the dried droppings
and remains of
cockroaches.
Pollen from Plants
How Is Asthma Treated?
• Because each case of asthma is different, treatment needs to be
tailored for each person. One general rule that does apply, though,
is removing the things in your environment that you know are factors
that make your asthma worse. When these measures are not
enough, it may be time to try one of the many medications that are
available to control symptoms.
• Asthma medications may be either inhaled or in pill form and are
divided into two types—quick-relief and long-term control. Quickrelief medicines are used to control the immediate symptoms of an
asthma episode. In contrast, long-term control medicines do not
provide relief right away, but rather help to lessen the frequency and
severity of episodes over time.
Causes of Asthma
•
People spend more time indoors. We are therefore exposed to more indoor
allergens, such as dust mite allergen, that cause asthma. Our houses are
now hermetically sealed to save heating and cooling energy and
unfortunately this causes more indoor allergen exposure.
•
People today live in cleaner, more sanitary conditions than they did before
the industrial revolution, relatively free of disease-causing viruses and
bacteria. This clean living affects our immune system. The immune system's
defensive white blood cells, called T cells, have two basic "settings”. Th1
cells fight infectious viruses and bacteria. Th2 cells fight parasites but are
also involved in allergic reactions.
We are exposed to fewer viruses and bacteria than people were 100 years
ago, so perhaps our immune systems have not learned to make Th1 cells
as well. That means we have a greater proportion of Th2 cells in our
bodies, which might lead to more allergies and asthma.
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Other theories point to increased levels of air pollutants, a decline in the
amount of exercise people get, or rising obesity as factors in the increase of
asthma.
Diagnosing Asthma
• A diagnosis of asthma usually is based on the patient's
symptoms, medical history, a physical examination, and
laboratory tests that measure pulmonary (lung) function.
Doctors typically look for signs that the patient's airflow is
obstructed and that the obstruction is at least partially
reversible.
• Evidence of reversible airway obstruction is often
detected in the physical examination or by physiologic
testing. Physiologic testing generally is recommended to
confirm the diagnosis. During an asthma attack,
wheezing can be heard by listening to the chest with a
stethoscope. The airway obstruction is considered
reversible if the wheezing disappears in response to
treatment, or when the suspected triggering factor is
removed or resolved.
Spirometry Test
• Spirometry
The most reliable way to determine reversible airway
obstruction is with spirometry, a test that measures the
amount of air entering and leaving the lungs. This simple
test can be performed in the physician's office.
• Spirometry uses a measuring device called a
spirometer that is connected by a flexible tube to a
disposable cardboard mouthpiece. The patient exhales
and inhales deeply, then seals his or her lips around the
mouthpiece and blows as forcefully and for as long as
possible until all the air is exhaled from the lungs.
Asthma attacks are not all the same—some are worse than others. In a severe
asthma attack, the airways can close so much that not enough oxygen gets to vital
organs. This condition is a medical emergency. People can die from severe asthma
attacks.
Treatment for Asthma
A leukotriene antagonist. This drug binds
to receptors and blocks the ability of
leukotrienes to bind and trigger asthma. This
drug provides long term treatment.
Albuterol: rescue drugs for acute
asthma attacks. This drug provides
quick relief.
Medications
• Long-term-control medications. These
are used regularly to control chronic
symptoms and prevent asthma attacks.
• Quick-relief medications. You use these
as needed for rapid, short-term relief of
symptoms during an asthma attack.
• Allergy control. Decrease sensitivity to
allergens.
Long-Term Medication
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Inhaled Corticosteroids
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The most effective medications for asthma. They reduce inflammation in your airways and
prevent blood vessels from leaking fluid into your airway tissues.
Help decrease the frequency of attacks and reduce the need for other medications. Because
inhaled corticosteroids control most forms of asthma by delivering medication directly to your
airways, they have a lower risk of side effects than are associated with oral corticosteroids.
Inhaled corticosteroids include Floven), Pulmicort, Azmacort, Aerobid, Qvar.
Side effects associated with inhaled corticosteroids can include hoarseness or loss of voice,
oral yeast infections (thrush), and cough. Long-term use of inhaled corticosteroids may
slightly increase the risk of skin thinning, bruising, osteoporosis, eye pressure and cataracts.
In children, inhaled corticosteroids may slow growth.
Long-acting beta-2 agonists. A group of medications called bronchodilators,
which open up constricted airways.
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Leukotriene modifiers. Reduce the production or block the action of leukotrienes
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Cromolyn (Intal). Preventative inhaler.
— substances released by cells in your lungs during an asthma attack. Leukotrienes
cause the lining of your airways to become inflamed, which in turn leads to wheezing,
shortness of breath and mucus production. Leukotriene modifiers include Singulair
and Accolate.
New from Genentech
• Anti-IgE monoclonal antibodies. If you have
allergies, your immune system produces allergycausing IgE antibodies to attack substances that
generally cause no harm, such as pollen, dust
mites and pet dander. If you have allergic
asthma that's difficult to control (Xolair) may
reduce the number of asthma attacks you
experience by blocking the action of these
antibodies. That way your immune system isn't
prompted to react and cause the inflammation
that makes breathing difficult.
Respiratory System
Lung Capacities
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The amount of air a person breathes in and out at rest is called the Tidal
Volume (Vt about 500ml). During such breathing, a person could actually
take in more air or blow more out. The additional amount a person could
inhale, such as during maximum physical activity, is called the Inspiratory
Reserve Volume (IRV 3,000 ml). The additional amount a person could
exhale is called the Expiratory Reserve Volume (ERV 1,000 ml). The
Residual Volume (RV) is the amount of air that stays in the lung even after
maximum expiration.
"Capacities" are combinations of two or more volumes.
The Total Lung Capacity (TLC) is the total amount of air the lungs can
contain:
TLC = RV + ERV + Vt + IRV
The Vital Capacity (VC) is the total amount of air the person can breathe in
and out:
VC = ERV + Vt + IRV
Functional Residual Capacity (FRC) is the total amount of air left in the
lungs at the end of a normal exhalation: FRC = RV + ERV