FACT ABOUT HIGH ALTITUDE CLIMBING
Myth: The higher the altitude, the less oxygen
Safety on
Kilimanjaro climb, We carry oxygen tank on Kilimanjaro climbs as the
emergency life saving facilities and monitor oxygen saturation
The fact is that the oxygen content of the atmosphere remains exactly the same
from sea level to about 12 miles (20 km) above
the earth. The oxygen content is constant at 21%. The issue is that
the higher the altitude, the less atmospheric pressure there is, and
less oxygen is forced into the bloodstream with each breath. Therefore,
one needs to breathe more quickly in order to maintain an adequate
level of oxygen in the blood. (see "What Causes Altitude Illness"
below)
What Defines High Altitude?
Altitude is defined on the following scale
High (8,000 - 12,000 feet [2,438 - 3,658 meters]), Very High (12,000 -
18,000 feet [3,658 - 5,487 meters]), and Extremely High (18,000+ feet
[5,500+ meters]). Since few people have been to such altitudes, it is
hard to know who may be affected. There are
no specific factors
such as age, sex, or physical condition that correlate with
susceptibility to altitude sickness. Some people get it and some people
don't. Most people can go up to 8,000 feet (2,438 meters) with minimal
effect. If you haven't been to high altitude before, it's important to
be cautious. If you have been at that altitude before with no problem,
you can probably return to that altitude without problems as long as you
are properly acclimatized.
Kevin Ovendenk from British Columbus Canada on they honeymoon Kilimanjaro climb.
What Causes Altitude Illness
The concentration of oxygen at sea level is
about 21% and the barometric pressure averages 760 mmHg. As altitude
increases, the concentration remains the same but the number of oxygen
molecules per breath is reduced. At 12,000 feet (3,658 meters) the
barometric pressure is only 483 mmHg, so there are roughly 40% fewer
oxygen molecules per breath. In order to properly oxygenate the body,
your breathing rate (even while at rest) has to increase. This extra
ventilation increases the oxygen content in the blood, but not to sea
level concentrations. Since the amount of oxygen required for activity
is the same, the body must adjust to having less oxygen. In addition,
high altitude and lower air pressure causes fluid to leak from the
capillaries which can cause fluid build-up in both the lungs and the
brain. Continuing to higher altitudes without proper acclimatization can
lead to potentially serious, even life-threatening illnesses.
ACCLIMATIZATION
The major cause of altitude illnesses is
going too high too fast. Given time, your body can adapt to the decrease
in oxygen molecules at a specific altitude. This process is known as
acclimatization and generally kes 1-3 days at that altitude. For
example, if you hike to 10,000 feet (3,048 meters), and spend several
days at that altitude, your body acclimatizes to 10,000 feet (3,048
meters). If you climb to 12,000 feet (3,658 meters), your body has to
acclimatize once again. A number of changes take place in the body to
allow it to operate with decreased oxygen:
- –The depth of respiration increases.
- –Pressure in pulmonary arteries is
increased, "forcing" blood into portions of the lung which are normally
not used during sea level breathing.
- –The body produces more red blood cells to carry oxygen,
- –The body produces more carbonic
anhydrase, the enzyme that facilitates the release of oxygen from
hemoglobin to the body tissues.
Prevention of Altitude Illnesses
Prevention of altitude illnesses falls into
two categories, proper acclimatization and preventive medications. Below
are a few basic guidelines for proper acclimatization.
- If possible, don't fly or drive to high altitude. Start below 10,000 feet (3,048 meters) and walk up.
- If you do fly or drive, do not over-exert yourself or move higher for the first 24 hours.
- If you go above 10,000 feet (3,048
meters), only increase your altitude by 1,000 feet (305 meters) per day
and for every 3,000 feet (915 meters) of elevation gained, take a rest
day.
- "Climb high and sleep low." This is the
maxim used by climbers. You can climb more than 1,000 feet (305 meters)
in a day as long as you come back down and sleep at a lower altitude.
- If you begin to show symptoms of moderate
altitude illness, don't go higher until symptoms decrease ("don't go up
until symptoms go down").
- If symptoms increase, go down, down, down!
- Keep in mind that different people will
acclimatize at different rates. Make sure all of your party is properly
acclimatized before going higher.
- Stay properly hydrated. Acclimatization is
often accompanied by fluid loss, so you need to drink lots of fluids to
remain properly hydrated (at least 3-4 liters per day). Urine output
should be copious and clear.
- Take it easy; don't over-exert yourself
when you first get up to altitude. Light activity during the day is
better than sleeping because respiration decreases during sleep,
exacerbating the symptoms.
- Avoid tobacco and alcohol and other
depressant drugs including, barbiturates, tranquilizers, and sleeping
pills. These depressants further decrease the respiratory drive during
sleep resulting in a worsening of the symptoms.
- Eat a high carbohydrate diet (more than 70% of your calories from carbohydrates) while at altitude.
- The acclimatization process is inhibited by dehydration, over-exertion, and alcohol and other depressant drugs.
Preventive Medications
- Diamox (Acetazolamide)
allows you to breathe faster so that you metabolize more oxygen, thereby
minimizing the symptoms caused by poor oxygenation. This is especially
helpful at night when respiratory drive is decreased. Since it takes a
while for Diamox to have an effect, it is advisable to start taking it
24 hours before you go to altitude and continue for at least five days
at higher altitude. The recommendation of the Himalayan Rescue
Association Medical Clinic is 125 mg. twice a day (morning and afternoon
). (The standard dose was 250 mg., but their research showed no
difference for most people with the lower dose, although some
individuals may need 250 mg.) Possible side effects include tingling of
the lips and finger tips, blurring of vision, and alteration of taste.
These side effects may be reduced with the 125 mg. dose. Side effects
subside when the drug is stopped. Contact your physician for a
prescription. Since Diamox is a sulfonamide drug, people who are
allergic to sulfa drugs should not take Diamox. Diamox has also been
known to cause severe allergic reactions to people with no previous
history of Diamox or sulfa allergies. Frank Hubbell of SOLO recommends a
trial course of the drug before going to a remote location where a
severe allergic reaction could prove difficult to treat.
- Dexamethasone is a
prescription steroid that decreases brain and other swelling reversing
the effects of AMS. Dosage is typically 4 mg twice a day for a few days
starting with the ascent. This prevents most symptoms of altitude
illness. It should be used with caution and only on the advice of a
physician because of possible serious side effects. It may be combined
with Diamox. No other medications have been proven valuable for
preventing AMS.
Acute Mountain Sickness (AMS)
AMS is common at high altitudes. At
elevations over 10,000 feet (3,048 meters), 75% of people will have mild
symptoms. The occurrence of AMS is dependent upon the elevation, the
rate of ascent, and individual susceptibility. Many people will
experience mild AMS during the acclimatization process. Symptoms usually
start 12-24 hours after arrival at altitude and begin to decrease in
severity about the third day. The symptoms of Mild AMS are headache,
dizziness, fatigue, shortness of breath, loss of appetite, nausea,
disturbed sleep, and a general feeling of malaise. Symptoms tend to be
worse at night and when respiratory drive is decreased. Mild AMS does
not interfere
with normal activity and symptoms generally subside within 2-4 days as
the body acclimatizes. As long as symptoms are mild, and only a
nuisance, ascent can continue at a moderate rate. When hiking, it is
essential that you communicate any symptoms of illness immediately to
others on your trip. AMS is considered to be a neurological problem
caused by changes in the central nervous system. It is basically a mild
form of High Altitude Cerebral Edema (see below).
Basic Treatment of AMS
The only cure is either acclimatization or
descent. Symptoms of Mild AMS can be treated with pain medications for
headache and Diamox. Both help to reduce the severity of the symptoms,
but remember, reducing the symptoms is not curing the problem. Diamox
allows you to breathe faster so that you metabolize more oxygen, thereby
minimizing the symptoms caused by poor oxygenation. This is especially
helpful at night when respiratory drive is decreased. Since it takes a
while for Diamox to have an effect, it is advisable to start taking it
24 hours before you go to altitude and continue for at least five days
at higher altitude. The recommendation of the Himalayan Rescue
Association Medical Clinic is 125 mg. twice a day (morning and night).
(The standard dose was 250 mg., but their research showed no difference
for
most people with the lower dose, although some individuals
may need 250 mg.) Possible side effects include tingling of the lips and
finger tips, blurring of vision, and alteration of taste. These side
effects may be reduced with the 125 mg. dose. Side effects subside when
the drug is stopped. Contact your physician for a prescription. Since
Diamox is a sulfonamide drug, people who are allergic to sulfa drugs
should
not take Diamox.
Diamox has also been known to cause severe allergic reactions to people with no previous history of Diamox or sulfa allergies. A trial course of the drug is recommended
before going to a remote location where a severe allergic reaction could prove difficult to treat.
Moderate AMS
Moderate AMS includes severe headache that is
not relieved
by medication, nausea and vomiting, increasing weakness and fatigue,
shortness of breath, and decreased coordination (ataxia). Normal
activity is difficult, although the person may still be able to walk on
their own. At this stage, only advanced medications or descent can
reverse the problem. Descending even a few hundred feet (70-100 meters)
may help and definite improvement will be seen in descents of
1,000-2,000 feet (305-610 meters). Twenty-four hours at the lower
altitude will result in significant improvements. The person should
remain at lower altitude until symptoms have subsided (up to 3 days). At
this point, the person has become acclimatized to that altitude and can
begin ascending again. The best test for moderate AMS is to have the
person "walk a straight line" heel to toe. Just like a sobriety test, a
person with ataxia will be unable to walk a straight line. This is a
clear indication that
immediate descent is required. It is important to get the person to descend
before the ataxia reaches the point where they cannot walk on their own (which would necessitate a more complicated evacuation).
Severe AMS
Severe AMS presents as an increase in the severity of the aforementioned symptoms, including shortness of breath
at rest, inability to walk, decreasing mental status, and fluid buildup in the lungs. Severe AMS requires
immediate descent to lower altitudes (2,000 - 4,000 feet [610-1,220 meters]).
There are two other severe forms of altitude
illness, High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary
Edema (HAPE). Both of these happen less frequently, especially to those
who are properly acclimatized. When they do occur, it is usually with
people going too high too fast or going very high and staying there. The
lack of oxygen results in leakage of fluid through the capillary walls
into either the lungs or the brain.
High Altitude Pulmonary Edema (HAPE)
HAPE results from fluid buildup in the lungs.
The fluid in the lungs prevents effective oxygen exchange. As the
condition becomes more severe, the level of oxygen in the bloodstream
decreases, and this can lead to cyanosis, impaired cerebral function,
and death. Symptoms include shortness of breath even at rest, "tightness
in the chest," marked fatigue, a feeling of impending suffocation at
night, weakness, and a persistent productive cough bringing up white,
watery, or frothy fluid. Confusion, and irrational behavior are signs
that insufficient oxygen is reaching the brain. One of the methods for
testing yourself for HAPE is to check your recovery time after exertion.
If your heart and breathing rates normally slow down in X seconds after
exercise, but at altitude your recovery time is much greater, it may
mean fluid is building up in the lungs. In cases of HAPE,
immediate descent is a necessary life-saving measure (2,000 - 4,000 feet [610-1,220 meters]). Anyone suffering from HAPE
must be evacuated to a medical facility for proper follow-up treatment.
High Altitude Cerebral Edema (HACE)
HACE is the result of swelling of brain
tissue from fluid leakage. Symptoms can include headache, loss of
coordination (ataxia), weakness, and decreasing levels of consciousness
including, disorientation, loss of memory, hallucinations, psychotic
behavior, and coma. It generally occurs after a week or more at high
altitude. Severe instances can lead to death if not treated quickly.
Immediate descent
is a necessary life-saving measure (2,000 - 4,000 feet [610-1,220
meters]). There are some medications that may be prescribed for
treatment in the field, but these require that you have proper training
in their use. Anyone suffering from HACE
must be evacuated to a medical facility for proper follow-up treatment.
Other Medications for Altitude Illnesses
- Ibuprofen is effective at relieving altitude headache.
- Nifedipine rapidly decreases pulmonary artery pressure and relieves HAPE.
- Breathing oxygen reduces the effects of altitude illnesses.
Gamow BagThis clever invention
has revolutionized field treatment of high altitude illnesses. The bag
is basically a sealed chamber with a pump. The person is placed inside
the bag and it is inflated. Pumping the bag full of air effectively
increases the concentration of oxygen molecules and therefore simulates a
descent to lower altitude. In as little as 10 minutes the bag can
create an "atmosphere" that corresponds to that at 3,000 - 5,000 feet
(915 - 1,525 meters) lower. After a 1-2 hours in the bag, the person's
body chemistry will have "reset" to the lower altitude. This lasts for
up to 12 hours outside of the bag which should be enough time to walk
them down to a lower altitude and allow for further acclimatization. The
bag and pump weigh about 14 pounds (6.3 kilos) and are now carried on
most major high altitude expeditions
.
Cheyne-Stokes Respirations
Above 10,000 feet (3,000 meters) most people experience a periodic
breathing during sleep known as Cheyne-Stokes Respirations. The pattern
begins with a few shallow breaths and increases to deep sighing
respirations then falls off rapidly. Respirations may cease entirely for
a few seconds and then the shallow breaths begin again. During the
period when breathing stops the person often becomes restless and may
wake with a sudden feeling of suffocation. This can disturb sleeping
patterns, exhausting the climber. Acetazolamide is helpful in relieving
the periodic breathing. This type of breathing is
not considered
abnormal at high altitudes. However, if it occurs first during an
illness (other than altitude illnesses) or after an injury (particularly
a head injury) it may be a sign of a serious disorder.
Source: Princeton University Outdoor Action Program
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Quazi from America on top of summit of Kilimanjaro
Fact about high altitude
