What happens to your body at the top of Mount Everest - Andrew Lovering
If someone teleported from sea level
to the top of Mt. Everest,
things would go bad fast.
At an altitude of 8,848 meters,
barometric pressure is approximately
33% of what it is at sea level.
This means there's significantly
less oxygen in the air,
and our teleported individual would
likely suffocate in minutes.
However, for people that make this same
journey over the course of a month,
it's possible to survive
at the peak for hours.
So what can happen to our bodies
in just one month
that allows us to endure
this incredible altitude?
Let’s imagine you’re one
of the 5.8 billion people
living less than 500 meters
above sea level.
When you take a breath at this altitude,
your lungs fill up with air composed
of numerous gases and compounds.
Most important among these
are oxygen molecules,
which bind to the hemoglobin
in your red blood cells.
Blood then circulates
throughout your body,
bringing essential oxygen
to all your cells.
But as altitude increases,
the air starts to get thinner.
The relative amounts of each compound
remain the same
well into the upper atmosphere,
but overall, there is less oxygen
for our bodies to absorb.
And if you ascend to altitudes
above 2,500 meters,
the resulting oxygen deprivation can cause
a form of altitude sickness
known as AMS,
often causing headaches,
fatigue and nausea.
Fortunately, AMS only happens
when we ascend too fast,
because our bodies have numerous ways
of adapting to high altitudes.
Within minutes or even seconds
of reaching altitudes of 1,500 meters,
carotid chemoreceptors in your neck
sense your blood’s low oxygen pressure.
This triggers a response that increases
the rate and depth of your breathing
to counteract the lack of oxygen.
Your heart rate also increases
and your heart contracts more tightly
to pump additional blood with each beat,
quickly moving oxygenated
blood around your body.
All these changes happen relatively fast,
and if you were to keep ascending,
your heart rate and breathing
would speed up accordingly.
But if you stayed at this altitude
for several weeks,
you could reap the benefits
of some longer-term adaptations.
Within the first few days
above 1,500 meters,
the volume of plasma
in your blood decreases,
which increases the concentration
of hemoglobin.
Over the next two weeks, your hemoglobin
levels will continue to rise,
allowing your blood to carry
even more oxygen per milliliter.
Paired with your high heart rate,
this new hemoglobin-rich blood efficiently
distributes oxygen throughout your body.
So much so that the volume of blood
being pumped with each heartbeat
can return to normal levels.
Over this same time, your breathing
also increases even further
in a process called
ventilatory acclimatization.
After this several weeks
of extended acclimatization,
your body has made enough significant
changes to climb even higher.
However, you’ll still have to spend
additional time acclimating along the way,
often climbing back down to recover
before ascending even higher.
Because the summit of Everest
isn't just high,
it’s the highest place on Earth.
And at altitudes above 3,500 meters,
our bodies are under incredible stress.
Arteries and veins in the brain
dilate to speed up blood flow,
But our smallest blood vessels,
called capillaries,
remain the same size.
This increased pressure can cause
blood vessels to leak,
and fluid to build up in the brain.
A similar issue can occur in the lungs,
where low oxygen causes blood vessels
to constrict,
leading to more leaking vessels
and fluid buildup.
These two conditions—
known as HACE and HAPE, respectively—
are incredibly rare,
but can be life-threatening
if not dealt with quickly.
Some Tibetans and South Americans
with family histories
of living at high altitude
have genetic advantages that can
prevent minor altitude sickness,
but even they aren’t immune
to these severe conditions.
Yet despite these risks,
climbers over the last century
have proved people can go higher
than scientists ever thought possible.
Pushing past their body’s limitations,
these climbers have redefined
what humanity can adapt to.
