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It starts with a cough,

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or a wheeze.

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Soon, your chest feels tight.

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Your breathing speeds up
and gets shallower,

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making you feel short of breath.

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These are common symptoms
of an asthma attack.

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Around the world, more than 300 million
people suffer from asthma,

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and around 250,000 people 
die from it each year.

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But why do people get asthma
and how can this disease be deadly?

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Asthma affects the respiratory system,

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particularly the smaller airways,

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such as the bronchi and bronchioles.

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These airways have an inner lining
called the mucosa

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that's surrounded 
by a layer of smooth muscle.

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In people with asthma, the airways
are chronically inflamed,

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which can make them hyper-responsive
to certain triggers.

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Some of the many asthma triggers
include tobacco smoke,

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pollen,

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dust,

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fragrances,

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exercise,

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cold weather,

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stress,

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and even the common cold.

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When people with asthma are exposed
to these triggers,

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an asthma attack, or exacerbation,
can occur.

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But how exactly do such everyday factors
lead to an asthma attack?

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If an asthmatic is exposed to a trigger,

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the smooth rings of muscle that circle
the small airways in their lungs

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contract and become narrow.

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Simultaneously, the trigger
worsens inflammation,

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causing the mucosal lining
to become more swollen

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and secrete more mucus.

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Under normal conditions,

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the body uses this mucus to trap
and clear particles, like pollen or dust,

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but during an asthma attack,

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it blocks the narrowed airways,
making it even harder to breathe.

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These effects lead 
to this symptoms of asthma.

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Smooth muscle constriction results
in the feeling of chest tightness.

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Excess mucus and increased inflammation
can cause coughing.

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And the wheezing noise?

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That happens because 
as the airways constrict,

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air whistles as it passes through
the narrowed space.

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These symptoms may make a person
feel like they're running out of air.

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Yet counterintuitively, 
during an asthma attack,

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the inflammation can make it harder
to exhale than inhale.

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Over time, this leads to an excess
of air in the lungs,

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a phenomenon known as hyperinflation.

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The trapping of air inside the lungs
forces the body to work harder

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to move air in and out of them.

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Over time, this can lead to reduced oxygen
delivery to the body's organs and tissues.

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Sometimes, in untreated 
severe asthma attacks,

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the body can't keep up,

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which can lead to death from
lack of oxygen.

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So how do we prevent these uncomfortable
and potentially fatal attacks

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in people who have asthma?

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One way is to reduce the presence
of triggers.

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Unfortunately, the world 
is an unpredictable place

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and exposure to triggers can't
always be controlled.

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This is where inhalers, the primary
treatment for asthma, come in.

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These medications help asthmatics both
control and prevent their asthma symptoms.

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Inhalers transport medication along
the affected airways

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using a liquid mist or fine powder
to treat the problem at its source.

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They come in two forms.

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There are reliever medications,

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which treat symptoms immediately
and contain beta-agonists.

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Beta-agonists relax constricted muslces,

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allowing the airways to widen so more air
can travel into and out of the lungs.

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The other form of inhalers serve
as preventive medications,

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which treat asthma symptoms
over the long term,

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and contain corticosteroids.

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Corticosteroids reduce airway sensitivity
and inflammation,

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so asthma can be kept under control.

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They're also crucial in preventing
long-term damage

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from chronic inflammation,

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which can cause scarring of the airways.

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Inhalers are known to be very effective,

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and have helped many people
live better lives.

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Although we've come a long way
in improving how we treat

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and diagnose asthma,

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we still don't know its exact causes.

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We currently believe that a combination
of genetic and environmental factors

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play a role,

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potentially acting during early childhood.

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Recent research has even linked
poverty to asthma incidents.

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This may be due to reasons ranging

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from exposure to additional pollutants
and environmental irritants

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to difficulties in obtaining medical care
or treatment.

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As our understanding of asthma improves,

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we can continue to find better ways to
keep people's airways happy and healthy.