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In the 16th century, Flemish physician
Andreas Vesalius described
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how a suffocating animal could be
kept alive
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by inserting a tube into its trachea
and blowing air to inflate its lungs.
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In 1555, this procedure didn’t warrant
much acclaim.
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But today, Vesalius’s treatise
is recognized
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as the first description of
mechanical ventilation–
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a crucial practice in modern medicine.
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To appreciate the value of ventilation,
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we need to understand how the
respiratory system works.
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We breathe by contracting our diaphragms,
which expands our chest cavities.
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This allows air to be drawn in, inflating
the alveoli –
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millions of small sacs inside our lungs.
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Each of these tiny balloons is surrounded
by a mesh of blood-filled capillaries.
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This blood absorbs oxygen from the
inflated alveoli
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and leaves behind carbon dioxide.
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When the diaphragm is relaxed,
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the CO2 is exhaled alongside a mix
of oxygen and other gases.
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When our respiratory systems are working
correctly,
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this process happens automatically.
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But the respiratory system can be
interrupted by a variety of conditions.
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Sleep apnea stops diaphragm muscles
from contracting.
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Asthma can lead to inflamed airways
which obstruct oxygen.
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And pneumonia, often triggered by
bacterial or viral infections,
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attacks the alveoli themselves.
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Invading pathogens kill lung cells,
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triggering an immune response that
can cause lethal inflammation
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and fluid buildup.
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All these situations render the lungs
unable to function normally.
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But mechanical ventilators take over
the process,
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getting oxygen into the body when
the respiratory system cannot.
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These machines can bypass constricted
airways,
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and deliver highly oxygenated air to
help damaged lungs diffuse more oxygen.
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There are two main ways ventilators
can work –
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pumping air into the patient’s lungs
through positive pressure ventilation,
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or allowing air to be passively drawn
in through negative pressure ventilation.
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In the late 19th century,
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ventilation techniques largely
focused on negative pressure,
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which closely approximates natural
breathing
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and provides an even distribution
of air in the lungs.
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To achieve this, doctors created a
tight seal around the patient’s body,
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either by enclosing them in a
wooden box or a specially sealed room.
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Air was then pumped out of the
chamber, decreasing air pressure
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and allowing the patient’s chest cavity
to expand more easily.
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In 1928, doctors developed a portable,
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metal device with pumps powered
by an electric motor.
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This machine, known as the iron lung,
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became a fixture in hospitals
through the mid-20th century.
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However, even the most compact
negative pressure
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designs heavily restricted a patient’s
movement
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and obstructed access for caregivers.
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This led hospitals in the 1960’s to shift
towards positive pressure ventilation.
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For milder cases, this can be
done non-invasively.
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Often, a facemask is fitted over the
mouth and nose,
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and filled with pressurized air which
moves into the patient’s airway.
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But more severe circumstances
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require a device that takes over
the entire breathing process.
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A tube is inserted into the patient’s
trachea
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to pump air directly into the lungs,
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with a series of valves and branching
pipes
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forming a circuit for inhalation
and exhalation.
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In most modern ventilators,
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an embedded computer system
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allows for monitoring the patient’s
breathing and adjusting the airflow.
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These machines aren’t used as a standard
treatment, but rather, as a last resort.
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Enduring this influx of pressurized air
requires heavy sedation,
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and repeated ventilation can cause
long-term lung damage.
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But in extreme situations, ventilators can
be the difference between life and death.
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And events like the COVID-19 pandemic
have shown
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that they’re even more essential
than we thought.
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Because current models are bulky,
expensive,
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and require extensive training to operate,
most hospitals only have a few in supply.
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This may be enough under normal
circumstances,
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but during emergencies, this limited
cache is stretched thin.
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The world urgently needs more low-cost
and portable ventilators,
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as well as a faster means of producing and
distributing this life-saving technology.