While
hiking a peak in Bolivia,
Hackett developed a bad
headache, felt nauseated and
drowsy and started to lose his
coordination.
"It
came on so quickly and was so
severe, I had to immediately
descend," said Hackett, a
physician and expert in
altitude sickness at the
University of Washington in
Seattle.
Hackett's
troubles are common for
flatlanders who ascend to high
altitudes too fast. But recent
research shows not everyone is
as vulnerable. And, it turns
out, different groups of
people have evolved different
ways of adjusting to living in
high altitude, low oxygen
places.
Scientists
are just starting to
understand these differences
and they say their work could
someday help flatlanders like
Hackett trek in good health.
Understanding
how thin air affects the lungs
and brain could also extend
beyond the relatively small
world of climbers and skiers
who suffer from altitude
sickness. It could also lead
to new treatments for other
afflictions, including
migraines and obesity.
"I
think we've only begun to
scratch the surface when it
comes to finding common ground
with other conditions,"
said Robert Roach, research
director at the Colorado
Center for Altitude Medicine
and Physiology in Denver.
Heavy
Breathers, Thick Blood
Even
top athletes are vulnerable to
the symptoms of acute mountain
sickness, which range from
headaches to dizziness to
severe nausea and vomiting.
Above 14,000 feet, two
afflictions can become deadly
— high altitude pulmonary
edema (HAPE), which results
from the constriction of blood
vessels and build of fluid in
the lungs, and high altitude
cerebral edema (HACE), a
swelling and build up of fluid
in the brain.
One
way to understand how high
altitude makes some people
sick is by understanding why
others don't get sick.
Cynthia
Beall of Case Western Reserve
University in Cleveland,
recently examined inhabitants
of plateaus in Tibet, Ethiopia
and the Andes and found that
each group of people have
developed their own ways of
boosting their bodies' oxygen
levels.
Indigenous
people of the Andes, she
found, carry more hemoglobin
— a carrier of oxygen — in
their blood.
"There
are fewer oxygen molecules in
a breath and so with more
hemoglobin you have a bigger
sponge, essentially,"
explains Beall.
Tibetans,
who have the longest history
of living in highlands, have
evolved a completely
different, and some argue,
superior strategy — they
breathe more. By increasing
their rate of breathing,
Tibetan highlanders cram more
oxygen into their lungs.
Meanwhile,
Ethiopians living in the
highlands of East Africa have
adapted in ways that
scientists don't yet
understand. Their blood
appears to have normal levels
of hemoglobin, says Beall and
their breathing rate is not
unusually rapid. Still they
somehow extract more oxygen
from the thin air.
"It's
as if they weren't even at
high altitudes," she
said.
Pharmaceutical
Solutions
The
findings are of interest to
anthropologists who use the
adaptations as markers to
measure how long people have
lived — and evolved — in
the high altitude regions.
The
information is also useful to
those looking for ways of
helping people avoid altitude
sickness.
Diamox,
a drug commonly prescribed for
HAPE, borrows a trick from
native Tibetans and stimulates
faster, deeper breathing.
Hackett
explains that most people
going to high altitudes begin
to gradually build up more
hemoglobin in their blood to
carry more oxygen — as the
Andean people naturally do.
But having too much hemoglobin
can become a problem for most.
"It's
like having motor oil in your
blood," he said. "It
gets too thick and you get
sick and have trouble
sleeping."
Understanding
how native high-altitude
Andeans increase their
hemoglobin levels and manage
to avoid the "motor
oil" problem could be
instructive. Hackett and Beall
are also interested in the
body's ability to produce
nitric oxide — an agent that
effectively expands the
diameter of blood vessels and
prevents constriction of blood
vessels the lungs.
Some people automatically
produce more nitric acid when
exposed to thin air, but not
everyone is so naturally
equipped. In recent years,
scientists have found that
Viagra, a drug designed for an
entirely different purpose,
has similar effects as nitric
oxide and triggers the
expansion of blood vessels in
the lung (as well as in a
lower organ), preventing
pulmonary edema.
"There
aren't many people who get
pulmonary edema in high
altitudes," said Hackett.
"So it won't be a huge
use of the drug, but it seems
to be effective."
At
the Colorado Center for
Altitude Medicine and
Physiology, Robert Roach is
looking for news ways of
preventing and treating
altitude sickness in research
that he hopes will extend
benefits to those in all
altitudes.
New
Cures for Migraines, Obesity?
Altitude
headaches and migraines, for
example, may share some
features. Roach hopes by
investigating altitude
headaches he may stumble upon
new explanations and possibly
treatments for migraines,
which afflict about 24 million
Americans.
Roach
has two main tools at his
disposal: a chamber that
mimics the low oxygen
atmosphere of high altitudes
and a magnetic resonance
imaging machine that takes
snapshots of the brain.
"It's
more difficult to study
migraine sufferers because
their headaches aren't very
predictable," Roach
explained. "But altitude
is very reproduceable. If I
put you in our high altitude
chamber, I can give you a real
bad headache."
Another realm of interest is
obesity. For reasons that
scientists don't yet fully
understand, people who spend
time in high altitudes tend to
shed weight.
Roach
cautions, "We're still
shooting in the dark,"
but he and his colleagues are
investigating whether
subjecting people to the
effects of high altitude by
having them sleep in
specialized tents at night,
might lead to weight loss.
"It
may not be rocket
science," he said.
"But we may learn
something we don't know about
obesity and weight loss."
Although
people like Roach, Beall and
Hackett are learning more
about the afflictions
associated with high altitude,
they all emphasize that simple
awareness is the best way to
avoid trouble.
Roach
points out that altitude
sickness is mostly a modern
one since airplanes can now
transport people to high
altitude places like
Telluride, Co. (at 9,000 feet)
fairly quickly. Forcing the
body into this kind of abrupt
adjustment is what leads to
problems.
"In
the old days it usually took
months to get to high
altitudes so the body had time
to adjust," he said.
"That window of
adjustment is critical. Today,
people fly to Colorado to go
skiing and have no clue they
could be vulnerable." 
