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Welcome
to the EverestNews.com Lesson plans developed by
Kevin Cherilla ( base camp manager of the NFB
2001 Everest Expedition and 7th and 8th grade
physical education teacher from Phoenix, Arizona)
and the staff at EverestNews.com, the largest
mountaineering publication in the world.
If
you would like to hire Kevin as an Everest speaker e-mail us at
everestnews2004@adelphia.net
today !
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The
Physiology of High Altitude Climbing: What
happens to your body at high altitude? Why do some
people get sick and even die? According to Dr. Eric
Weiss, when trekkers first started to going to
Everest, one out of every 50 died. Nowadays, thanks to
awareness of the consequences of high altitude, that
figure is one in 10,000 to 50,000. The medical
syndromes encountered at altitude all come down to the
body's response to the decline of oxygen
pressure.
Atmospheric
pressure is a gauge of how many oxygen molecules are
available per given volume, say a breath. While there
is the same percentage of oxygen in the air up high,
lower atmospheric pressure at higher altitudes means
fewer oxygen molecules are available with each
breath.
Cerebral
Edema:
Many people who travel from sea level to over 8,000
feet report symptoms ranging from headache to loss of
appetite and nausea. Why? As the available oxygen
falls, the body responds by increasing the blood flow
to the brain, but it can overcompensate, and fluid
leaks from the blood vessels into the brain causing it
to swell. The result is Acute Mountain Sickness. Cases
can run the spectrum from mild to life threateningly
severe swelling called High Altitude Cerebral Edema
(HACE).
Not
surprisingly, the greater the elevation gain, the more
severe the swelling. In severe cases the brain can get
squeezed down the spinal cord which results in death.
The way to avoid falling victim is to ascend
gradually, about 1,000'/day over 8,000' which gives
your body time to acclimatize properly.
You
can treat, and indeed preempt, Acute Mountain Sickness
by using a diuretic called Diamox and drinking plenty
of water. Signs to watch for with HACE are persistent
severe headache, loss of coordination, and problems
with thought processes. Treatment is immediate
descent, and Decadron or oxygen if available.
Pulmonary
Edema:
Groups of trekkers are occasionally struck by a
mysterious flu-like illness near the high point of
their trek, and, just as mysteriously, they get better
when they head down. What they had was not flu, but
High Altitude Pulmonary Edema (HAPE), which is a
build-up of fluid in the lungs, and can lead to a
feeling of profound fatigue.
As
the body tries to get as much oxygen from the air as
it can, Pulmonary edema can result from the greatly
increased blood flow through the lungs. The heart
increases the flow by increasing the pressure, causing
leakage from the blood vessels into the air sacs. It
usually takes a few days to develop, and is
exacerbated by overexertion. In bad cases, you can
hear a gurgling of fluid in the lungs, and the victim
brings up a bloody sputum. This is a serious condition
which can kill in only a matter of hours. HAPE is best
avoided by gradual ascent. Treatment is immediate
descent by several thousand feet and oxygen if
available.
Too
Much of a Good Thing:
The body also responds to the lower oxygen levels by
putting more red blood cells into circulation. Up to a
point, this is a good thing. However, if it goes too
far, the blood becomes thick and prone to clotting.
Clots which get dislodged float around and can cause
strokes, heart attacks, and pulmonary embolisms. The
only treatment for thick blood is to be bled. Since
this condition takes weeks to develop, it is rarely an
issue, except on the Himalayan giants.
Many
climbers who have been to over 14,000' have
experienced listening to their tent-mates repeatedly
stop breathing, gasp, breathe heavily for a while and
then stop breathing again. This is called periodic
breathing, and is caused when the system which
regulates breathing gets out of whack. The sleeper
responds to a build-up in carbon dioxide by
hyperventilating. This leads to respiratory alkalosis,
and the breathing center responds by shutting off
respiration. CO² levels then increase and the cycle
repeats. It is a relatively benign condition, and
responds well to a low dose of Diamox taken at bed
time.
The
Khumbu Cough:
A common complaint of high altitude climbers is a
persistent dry cough (high altitude hack), which can
be so bad it results in broken ribs. This condition
results from a drying out of the bronchi caused by
breathing the cold, dry air. The best prophylaxis is
to avoid overexertion, thereby keep the breathing rate
down, so that the bronchial mucosa stay moist.
If
you would like to pursue high altitude medical topics
further,
check out Medicine
for Mountaineering by James Wilkerson and "Wilderness
Medicine, Ch.1, by Auerbach.
JUST
THE FACTS
The concentration (percentage) of oxygen in the air is
the same at all altitudes.
The amount of oxygen available to the human body is
determined by atmospheric pressure which decreases
with altitude the air thins leaving fewer
molecules of oxygen per breath.
Atmospheric pressure determines how much air is
"pushed" into the lungs with each
breath.
The atmospheric pressure at the summit of Mount
Everest (29,035') is about a third that of sea
level.
Heartbeat rate, breathing rate, and the production of
red blood cells, which carry oxygen through the body,
increase as the body acclimates to high altitude,
allowing more oxygen to be "grabbed" from
every breath.
Acute
Mountain Sickness (AMS)
Often occurs
around 8,000'
Symptoms:
Vomiting
Headache that doesn't respond to usual medicine
Shortness of breath
Exhaustion that doesn't fade with rest
This
may be a warning sign for the onset of more serious
altitude illness.
Treatment
is rest with further ascent recommended only after
symptoms have ceased.
Severe AMS
Altered balance or muscular coordination
Altered mental state
Extreme shortness of breath with almost any
activity
Person is angry, combative, or
incomprehensible
Further
ascent is not recommended unless there are options for
easy and rapid descent should symptoms recur.
HACE
Symptoms
Has occurred as
low as 10,000'
Ataxia or loss of balance and muscle coordination
Decreased mental functioning
Severe headache
Nausea and vomiting
Hallucinations or stroke-like symptoms of impaired
speech
Coma
and death may rapidly follow. The only treatment is
immediate descent.
HAPE Symptoms
Rarely occurs
below 8,000'
Extreme difficulty breathing and inability to catch
one's breath
Very rapid pulse and breathing rate (over thirty
breaths per minute)
Extreme exhaustion and difficulty with any
exertion
Coughing which may progress to sounding bubbly as
lungs fill with fluid
Fever and blue coloring, especially the lips and
fingernail beds
Death
can come on quickly. The only treatment is immediate
descent.
Acclimating
Climb as high as you want during the day, but
raise sleeping altitude by no more that 1,000' a day.
Factor in a rest day every 3,000'.
Spend at least one night below 10,000' before
ascending higher.
If you don't feel good, don't raise sleeping
altitude until you feel better.
If you don't feel better at the current sleeping
altitude, descend to below where you first felt
sick.
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