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General information about
altitude sickness |
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What is altitude sickness? |
Altitude
sickness is the name given to the physiological and symptomatic reactions of
the human body to the low oxygen pressure (thinner air) that occurs at high
altitude. It is also known as acute mountain sickness.
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Where do you get
altitude sickness? |
About
20 % of people experience mild symptoms at altitudes between 2200 and 2500m
above sea level. The incidence of altitude sickness, which varies from one individual to
another, is directly related to the rate of ascent. It is also significantly
related to how long a person stays at that height.
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How do you get
altitude sickness? |
When
oxygen pressure falls, the body puts in place a number of counter measures. Breathing
and pulse rates increase, as does the heart's pumping efficiency, and the size
and number of red blood cells, which are responsible for the blood's oxygen
carrying capacity.
However, the shortage of oxygen also has a number of unwanted consequences:
increased pressure in the pulmonary (lung) circulation, changes in blood pH
(acidity) values, disturbances in the fluid/electrolyte (salt) balance, as well
as the leakage and spread of blood or fluid into surrounding vessels and
tissues (fluid extravasations or edema).
Altitude sickness can occur by traveling
relatively quickly to a greater height and staying at the new height for
more than 24 hours, without adequate acclimatization beforehand. Altitude
sickness is not dependent on a person's fitness and can affect even the most
experienced athletes.
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How can altitude sickness be
prevented? |
- By taking a graded
ascent. Climb relatively slowly to higher levels, and allow adequate
periods of acclimatization (two to three days) at a given height (starting
from 2200m) before spending a night at a greater height.
- It's fine to climb up
during the day, but you should try to get down to 2200m (or the height you
are currently acclimatized to) in the course of the same day. Then you can
move up, depending on your individual tolerance, by 300 to 500m, until you
rest and get acclimatized again for at least a couple of days, and so on.
- If you feel ill at a
particular height, come down to your previously acclimatized height.
- Drink plenty of
liquids (at least three litres a day).
- Avoid drinking alcohol.
- Avoid getting cold.
- To a certain extent,
altitude sickness can be prevented by taking 750mg acetazolamide (Diamox SR)
per day from one day before ascent until two days after reaching the maximum
height.
Some experts suggest that to get to know the possible drug side effects it is
wise to give it a two-day trial before the trip. This is an unlicensed use of
this medicine, which is also only available on prescription, so it should only
be undertaken on the advice of a doctor.
Possible side effects include: nausea taste disturbance, tingling hands and
feet, frequent and copious urination, visual disturbances and skin rash.
However, taking Diamox SR does not mean people can ignore advice about slow
ascent.
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Danger signals for altitude
sickness |
Danger
signals usually develop in the first 36 hours. They affect more than 50 per
cent of travelers above 3500m and almost 100 per cent of people who climb
quickly to 5000m without acclimatizing.
- An insignificant
headache that disappears with one to two ordinary headache tablets.
- Nausea and general malaise.
- Slight dizziness.
- Some difficulty sleeping.
With these symptoms at
heights below 3000m, you can usually allow yourself to stay on and to rest
for a couple of days before further permanent ascents. At heights around
3500m, you should try moving down 300 to 500m and stay there for two days
before further permanent ascents.
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Serious symptoms
of altitude sickness |
- A severe, enduring
headache, which is not cured by a couple of ordinary painkillers.
- Marked nausea and
repeated vomiting.Irritating dizziness
or actual difficulty with balance and direction.
- Regular visual
disturbances with flickering vision and problems judging distance.
- Pressure in the chest,
rapid breathing and pulse rate, crackles in breathing and shortness of breath.
- Swelling beneath the skin
(edema), typically around the eyes and in some cases swollen ankles and
hands.
- Confusion.
- Convulsions.
In the presence of these
symptoms, medical attention must be sought immediately, and the patient
brought down to the lowest possible height.
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Acute mountain sickness |
Acute
mountain sickness is the name given to two life-threatening complications of
acute altitude sickness. Both have a high mortality rate and may occur when you
have already spent 24 to 36 hours at 'too great' a height (typically over
3500m). These are:
- HAPE - high altitude
pulmonary edema (water in the lungs).
- HACE - high altitude cerebral edema
(fluid on the brain).
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High altitude
pulmonary edema (HAPE) |
The
symptoms of HAPE are predominantly severe and include increasing difficulty
breathing, dry cough, pressure in the chest, palpitations and fatigue. A
bubbling noise may be heard during breathing (edema in the lungs). The lips,
outer edges of the ears and nails may look blue (cyanosed) due to a shortage of
oxygen.
- The patient should be
transported to the lowest possible altitude as soon as possible.
- If possible, oxygen
should be given by nasal catheter, or if an oxygen mask and bottle are
available as CPAP (continuous positive airways pressure), or better still,
hyperbaric treatment (Gamow-bag).
- A calcium antagonist
(nifedipine capsules 10-20mg [quick-acting] should be given - this must
not be repeated, but followed by slower acting nifedipine tablets 20mg
every six hours).
- Dexamethasone
injection (into a vein or a muscle) should be given. The victim should be
transported sitting on a stretcher or something similar.
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High altitude
cerebral edema (HACE) |
The
symptoms of HACE are essentially very severe headache, visual disturbances,
light shunning, irritability, vomiting, vagueness and confusion, possible
unconsciousness and convulsions.
- The patient should be
transported to the lowest possible altitude as soon as possible.
- Oxygen (CPAP) or
better still, hyperbaric treatment (Gamow-bag) should be given.
- Dexamethasone
injection (into a vein or a muscle) should be given.
- Convulsions may be treated
with a benzodiazepine - e.g. diazepam.
- Transportation should be
in the natal position (strapped lateral) to avoid vomit getting into the
lungs.
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Who should never
be exposed to high altitude? |
- People with chronic
diseases of the heart/lungs (e.g. angina
pectoris or chronic
bronchitis, emphysema and some people with severe asthma
- People with anemia,
including sickle-cell anemia (low hemoglobin content in the blood).
- People with untreated
blood clotting disorders and a history of thromboses (clots).
- People who have
previously developed HAPE or HACE.
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Who should be careful at high
altitude? |
- People with successfully treated heart/lung
diseases (e.g. emphysema, asthma).
- Pregnant women.
- Children.
- People with severe diabetes
- People with high
blood pressure
- People with a tendency
to sleep apnoea
- People who have
previously developed HAPE or HACE.
Other problems to consider
are the prevention of sunburn, snow blindness, cold, frostbite and sunburn.
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