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Altitude Sickness
 Altitude
sickness or snow sickness as is commonly called generally occurs when you are
travelling above 2500m (8000ft). Every year many travellers die due to altitude
sickness.
Altitude sickness is a common condition that can happen when you climb to a
high altitude too quickly. The decrease in atmospheric pressure makes breathing
difficult, because you are not able to take in as much oxygen. Most cases are
mild, with symptoms also including: headache, nausea, dizziness, exhaustion.
In rare cases, altitude sickness can cause fluid to build up either on the
lungs or on the brain. These are very serious conditions and require immediate
medical attention. Symptoms of severe altitude sickness can include: a bubbling
sound in the chest, coughing up pink frothy liquid ,clumsiness and difficulty
walking,confusion, leading to loss of consciousness.
Altitude sickness is fairly common among those who spend time at high
altitudes, such as mountaineers and skiers. In its mildest form, altitude
sickness can occur at heights over about 2,500m (8,000 feet) above sea level,
which is a common height for many ski resorts. However, the more severe symptoms
of altitude sickness tend to occur at altitudes of 3,600m (about 12,000 feet)
and above.
Perhaps as many as half the visitors from lower elevations experience some
form of altitude illness. The vast majority of cases are self-limited and
spontaneously resolve as the body acclimatizes. Symptoms include fatigue,
decreased appetite, shortness of breath with minimal exertion, nausea, headache
and sleep disturbances. These symptoms are often worse the second day at
altitude (but resolve in four to five days). Rest is the key to treating mild
forms of altitude sickness.
Avoiding Altitude Sickness
-
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 quarts per day).
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Avoid tobacco and alcohol and other depressant drugs during acclimation,
which can also lead to dehydration.
-
Light Activity during the day is better than sleeping because
respiration decreases during sleep, exacerbating Altitude Sickness symptoms.
Frostbite & Hypothermia:
Frostbite results from cooling of body tissues and subsequent destruction of
these tissues. This occurs when skin is exposed to cold and windy conditions.
Fingers, ears and noses are especially susceptible. The best cure is prevention.
Keep the skin covered and warm up frequently. If blisters, occur or if fingers
or toes are involved, seek medical attention immediately. Over exposure to cold,
wetness or wind can cause a very low internal body temperature known as
hypothermia. Warning signs include shivering, fatigue, slowed pulse and bluish
lip color. Hypothermia is life threatening. Victims of hypothermia should get to
warmth and shelter, remove wet clothes, warm up in blankets, and drink warm,
non-alcoholic beverages. Emergency medical attention should be sought
immediately.
HAPE ( high altitude pulmonary oedema)
 HAPE
is excess fluid on the lungs, and causes breathlessness. It is never normal to
feel breathless when you are resting - even on the summit of Everest. This
should be taken as a sign that you have HAPE and may die soon. HAPE can also
cause a fever (a high temperature) and coughing up frothy spit. HAPE and HACE
often occur together.
HACE ( high altitude cerebral oedema)
HACE is fluid on the brain. It causes confusion, clumsiness, and stumbling.
The first signs may be uncharacteristic behaviour such as laziness, excessive
emotion or violence. Drowsiness and loss of consciousness occur shortly before
death.
Treatment of HAPE and HACE
-
Immediate descent is absolutely essential
-
Dexamethasone and acetazolamide should both be given, if available
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Pressure bags and oxygen gas can buy time
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What causes altitude sickness?
Two things are certain to make altitude sickness very likely - ascending
faster than 500m per day, and exercising vigourously. Physically fit individuals
are not protected - even Olympic athletes get altitude sickness. Altitude
sickness happens because there is less oxygen in the air that you breathe at
high altitudes.
Altitude sickness prevention
Go up slowly, take it easy, and give your body time to get used to the
altitude. The body has an amazing ability to acclimatise to altitude, but it
needs time. For instance, it takes about a week to adapt to an altitude of
5000m.
Can I take drugs to prevent altitude sickness?
As with everything, many 'quack' treatments and untested herbal remedies are
claimed to prevent mountain sickness. These treatments can make AMS worse or
have other dangerous side effects - many herbs are poisonous. Only one drug is
currently known to prevent AMS and to be safe for this purpose: acetazolamide (diamox).
It causes some minor side effects, such as tingling fingers and a funny taste in
the mouth.
The mild form of altitude sickness: acute mountain sickness (AMS)
Where does acute mountain sickness happen?
Most people remain well at altitudes of up to 2500m, the equivalent barometric
pressure to which aeroplane cabins are pressurised. However, even at around
1500m above sea level you may notice more breathlessness than normal on exercise
and night vision may be impaired. Above 2500m, the symptoms of altitude sickness
become more noticeable.
What are the other names for acute mountain sickness?
Acute mountain sickness is sometimes colloquially referred to as altitude
sickness or mountain sickness and in South America it is called soroche.
How are the symptoms of altitude sickness measured?
The most prominent symptom is usually headache, and most people also experience
nausea and even vomiting, lethargy, dizziness and poor sleep. Symptoms are very
similar to a really bad hangover. Acute mountain sickness can be diagnosed using
a self-assessment score sheet. If you have recently ascended to over 2500m, have
a headache and your total score is 3 points or more on the score sheet, then you
have acute mountain sickness.
Who gets acute mountain sickness?
Anyone who travels to altitudes of over 2500m is at risk of acute mountain
sickness. Normally it does't become noticeable until you have been at that
altitude for a few hours. Part of the mystery of acute mountain sickness is that
it is difficult to predict who will be affected. There are many stories of fit
and healthy people being badly limited by symptoms of acute mountain sickness,
while their older companions have felt fine.
There are a number of factors that are linked to a higher risk of developing the
condition. The higher the altitude you reach and the faster your rate of ascent,
the more likely you are to get acute mountain sickness. On the Apex high
altitude research expeditions, flying from sea level to the Bolivian capital, La
Paz (3600m), caused over half of the expedition members to have acute mountain
sickness on the day after they arrived. If you have a previous history of
suffering from acute mountain sickness, then you are probably more likely to get
it again. Older people tend to get less acute mountain sickness � but this could
be because they have more common sense and ascend less quickly.
What causes altitude sickness?
 There is so much less oxygen in the high mountains that it is not surprising
that travelling to high altitude causes people to feel unwell, but how this
shortage of oxygen actually leads to altitude sickness is still not fully
understood. Some scientists believe that it is due to swelling of the brain but
the evidence for this hypothesis is not conclusive. The theory is that in
susceptible individuals, swelling could cause a small increase in the pressure
inside the skull and lead to symptoms of acute mountain sickness. The swelling
may be due to increased blood flow to the brain or leakiness of blood vessels in
the brain.
What are the treatments for altitude sickness (mountain sickness)?
It is better to prevent acute mountain sickness than to try to treat it.
Following the golden rules should mean that your body can acclimatise as you
ascend and so you will be less likely to develop acute mountain sickness.
However, if you need to go up more quickly, you could consider taking a drug
called acetazolamide (also known as Diamox). There is now good evidence [BMJ.
2004;328:797] that acetazolamide reduces symptoms of acute mountain sickness in
trekkers, although it does have some unusual side-effects: it makes your hands
and feet tingle, and it makes fizzy drinks taste funny.
As with any form of altitude sickness, if you do have acute mountain sickness,
the best treatment is descent. Painkillers may ease the headache, but they don�t
treat the condition. Acetazolamide may be helpful, especially if you need to
stay at the same altitude, and resting for a day or two might give your body
time to recover. It is essential that you should NEVER go up higher if you have
acute mountain sickness.
If a travelling companion has symptoms of acute mountain sickness and becomes
confused or unsteady, or develops an extremely severe headache or vomiting, they
may have a life-threatening condition called high altitude cerebral oedema (HACE).
Read more about HACE.
There are many other remedies touted as treatments or 'cures' for altitude
sickness, but there is no evidence to support any of them. On our recent
research expeditions we have conducted drug trials of antioxidants, which did
not prevent altitude sickness, and viagra (Baillie JK et al, QJM 2009
102(5):341-348.
High altitude pulmonary oedema (HAPE)
HAPE is a dangerous build-up of fluid in the lungs that prevents the air
spaces from opening up and filling with fresh air with each breath. When this
happens, the sufferer becomes progressively more short of oxygen, which in turn
worsens the build-up of fluid in the lungs. In this way, HAPE can be fatal
within hours.
If you have had HAPE, please register with the HAPE database and tell us about
your experience
What are the symptoms?
HAPE usually develops after 2 or 3 days at altitudes above 2500 m.
Typically the sufferer will be more breathless compared to those around them,
especially on exertion. Most will have symptoms of acute mountain sickness.
Often, they will have a cough and this may produce white or pink frothy sputum.
The breathlessness will progress and soon they will be breathless even at rest.
Heart rate may be fast, the lips may turn blue and body temperature may be
elevated. It is easy to confuse symptoms of HAPE with a chest infection, but at
altitude HAPE must be suspected and the affected individual must be evacuated to
a lower altitude. If you think you have had HAPE, register on the HAPE database.
Who gets HAPE?
Unfortunately, it is currently impossible to predict who will get HAPE. This is
one of the reasons why we have established the HAPE database. People who have
had HAPE before are much more likely to get it again. Therefore, there must be
some factor that puts certain individuals at high risk of the condition.
However, just like acute mountain sickness, there are some known risk factors. A
fast rate of ascent and the altitude attained will make HAPE more likely.
Vigorous exercise is also thought to make HAPE more likely and anecdotal
evidence suggests that people with chest infections or symptoms of the common
cold before ascent may be at higher risk.
What causes HAPE?
Despite years of careful research the exact causes of HAPE remain poorly
understood. Fluid has been shown to fill up the air pockets in the lungs
preventing oxygen getting into the blood and causing the vicious circle of
events that can kill people with HAPE. As with many biological processes many
factors play a role in the disease and there is good evidence to support a
number of theories about how this fluid gets there.
Normally, oxygen gets into your blood and is supplied to the body from your
lungs. Each time you take a breath in, air rushes into the tiny air pockets at
the end of all the airway branches in your lungs. At the same time, blood from
your heart is brought close to these thin-walled air pockets, so that oxygen can
move into your blood while waste products move out. Oxygen-rich blood then
returns to the heart and is supplied to the body. If, by accident, you inhaled a
small object into your lungs, it would become stuck in one of the airways
branches. Little oxygen would get to the downstream air pockets. To prevent this
area of lung supplying blood starved of oxygen back to the heart (and therefore
the rest of body), blood vessels in the area closed down or constrict. This is
normally a very good thing and is an example of the body protecting itself.
At altitude however, this same process is a cause of the disease HAPE. Because
the whole lung is starved of oxygen, the whole lung reacts in the same way �
blood vessels constricting all over the place and not just in small areas. The
blood in these vessels is squeezed and the pressure goes up forcing fluid out of
blood and into air pockets. Click for a more detailed explanation of what
happens to the lungs at high altitude.
Very dangerous and reactive substances are formed in your blood when you are
starved of oxygen and these can directly damage the special membrane between air
and blood in your lungs causing further fluid leak and worsening HAPE.
How is HAPE treated?
 The most important treatment for HAPE is descent. Providing extra oxygen and/or
raising the air pressure around a victim with a Gamow bag (see right) can
reverse the underlying process, lack of oxygen, but these measures are really no
substitute however for rapid descent down the mountain. Some drugs can be
helpful, but should only be used by trained doctors. Nifedipine is a drug that
helps to open up the blood vessels in the lungs. By doing so, it reduces the
high pressure in those vessels that is forcing fluid out into the lungs.
Sildenafil (Viagra�), by a different mechanism, also opens up the blood vessels
in the lung and may be a useful treatment for HAPE. Following recent research,
medics may also give the steroid, dexamethasone. Drug treatment should only ever
be used as a temporary measure; the best treatment is descent.
High altitude cerebral oedema (HACE)
HACE is a build-up of fluid in the brain. HACE is life-threatening and
requires urgent action.
What are the symptoms?
HACE is thought to be a severe form of acute mountain sickness. A severe
headache, vomiting and lethargy will progress to unsteadiness, confusion,
drowsiness and ultimately coma. HACE can kill in only a few hours. A person with
HACE will find it difficult to walk heel-to-toe in a straight line � this is a
useful test to perform in someone with severe symptoms of acute mountain
sickness. HACE should also be suspected if a companion starts to behave
irrationally or bizarrely.
Who gets HACE?
About 1% of people of ascend to above 3000m get HACE. The lowest altitude at
which a case of HACE has been reported was 2100m. HACE can also occur in people
with HAPE and vice versa. Factors that increase the risk of HACE are similar to
those for acute mountain sickness and HAPE. The faster the rate of ascent and
the higher the altitude, the more likely it is that HACE will develop. HACE is
thought to occur mainly in trekkers or climbers who have ignored symptoms of
acute mountain sickness and climbed higher rather than staying at the same
altitude or descending.
What causes HACE?
The cause of HACE remains unknown. Several factors may play a role including
increased blood flow to the brain. An increase in blood flow is a normal
response to low oxygen levels as the body needs to maintain a constant supply of
oxygen to the brain. However, if the blood vessels in the brain are damaged,
fluid may leak out and result in HACE. Although we know that reactive chemicals
are released when oxygen levels are low and that these chemicals can damage
blood vessel walls, it still hasn�t been proven that the blood vessels in the
brain are actually more leaky.
How is HACE treated?
Descent is the most effective treatment of HACE and should not be delayed if
HACE is suspected. A Gamow bag, or portable altitude chamber, can be used as a
temporary measure and, if available, oxygen and a drug called dexamethasone
should be given.
Dated 14 June 2013
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