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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[br]and gets shallower,

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making you feel short of breath.

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These are common symptoms[br]of an asthma attack.

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Around the world, more that 300 million[br]people suffer from asthma,

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

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But why do people get asthma[br]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[br]called the mucosa

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that's surrounded [br]by a layer of smooth muscle.

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In people with asthma, these airways[br]are chronically inflamed,

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which can make them hyper-responsive[br]to certain triggers.

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Some of the many asthma triggers[br]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[br]to these triggers,

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an asthma attack, or exacerbation,[br]can occur.

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But how exactly do such everyday factors[br]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[br]the small airways in their lungs

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contract and become narrow.

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Simultaneously, the trigger[br]worsens inflammation,

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causing the mucosal lining[br]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[br]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,[br]making it even harder to breath.

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These effects lead [br]to this symptoms of asthma.

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Smooth muscle constriction results[br]in the feeling of chest tightness.

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Excess mucus and increased inflammation[br]can cause coughing.

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And the wheezing noise?

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That happens because [br]as the airways constrict,

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air whistles as it passes through[br]the narrowed space.

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

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Yet counterintuitively, [br]during an asthma attack,

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the inflammation can make it harder[br]to exhale than inhale.

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Over time, this leads to an excess[br]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[br]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[br]delivery to the body's organs and tissues.

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Sometimes, in untreated [br]severe asthma attacks,

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the body can't keep up,

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which can lead to death from[br]lack of oxygen.

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So how do we prevent these uncomfortable[br]and potentially fatal attacks

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in people who have asthma?

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One way is to reduce the presence[br]of triggers.

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Unfortunately, the world [br]is an unpredictable place

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and exposure to triggers can't[br]always be controlled.

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

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

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Inhalers transport medication along[br]the effected airways

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using a liquid mist or fine powder[br]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[br]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[br]can travel into and out of the lungs.

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The other form of inhalers serve[br]as preventive medications,

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which treat asthma symptoms[br]over the long term,

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and contain corticosteroids.

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Corticosteroids reduce airway sensitivity[br]and inflammation,

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so asthma can be kept under control.

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They're also crucial in preventing[br]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[br]live better lives.

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Although we've come a long way[br]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[br]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[br]poverty to asthma incidents.

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This may be due to reasons ranging

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from exposure to additional pollutants[br]and environmental irritants

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to difficulties in obtaining medical care[br]or treatment.

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As our understanding of asthma improves,

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