Altitude sickness, also known as acute mountain sickness, occurs due to acute exposure to low air pressure at high altitudes above 2,400 meters and can progress to life-threatening conditions such as high altitude pulmonary edema or cerebral edema if left untreated. The most effective treatment is rapid descent to lower altitudes. Other treatments include supplemental oxygen, acetazolamide medication to aid acclimatization, or portable hyperbaric chambers in severe cases when descent is not possible. Preventive measures include gradual ascent to allow acclimatization and avoiding alcohol and strenuous activity during initial exposure.

1. Altitude sickness
Altitude sickness, also known as acute mountain sickness (AMS), altitude illness,
hypobaropathy, or soroche, is a pathological effect of high altitude on humans, caused by acute
exposure to low air pressure (usually outdoors at high altitudes). It commonly occurs above
2,400 metres (approximately 8,000 feet).[1][2] Acute mountain sickness can progress to high
altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE).
The cause of altitude sickness is still not understood. It occurs in low atmospheric pressure
conditions but not necessarily in low oxygen conditions at sea level pressure. Although treatable
to some extent by the administration of oxygen, most of the symptoms do not appear to be
caused by low oxygen, but rather by the low CO2 levels causing a rise in blood pH, alkalosis.
The percentage of oxygen in air remains essentially constant with altitude at 21% up until 70,000
feet (21,330 m) but the air pressure (and therefore the number of oxygen molecules) drops as
altitude increases - consequently, the available amount of oxygen to sustain mental and physical
alertness decreases above 10,000 feet (3,050 m) . Altitude sickness usually does not affect
persons traveling in aircraft because modern aircraft passenger compartments are pressurized at
an air pressure equivalent to an altitude of 8,000 feet (2,440 m).
A related condition, occurring only after prolonged exposure to high altitude, is chronic
mountain sickness, also known as Monge's disease.
 An unrelated condition, although often confused with altitude sickness, is dehydration,
due to the higher rate of water vapor lost from the lungs at higher altitudes.
Introduction
High altitude or mountain sickness is defined when someone feels sick at high altitudes, such as
in the mountains or any other altitude-related sicknesses. It is hard to determine who will be
affected by altitude-sickness as there are no specific factors that compare with this susceptibility
to altitude sickness. However, most people can climb up to 2500 meters (8000 ft) normally.
Generally, different people have different susceptibilities to altitude sickness. For some
otherwise healthy people, Acute Mountain Sickness (AMS) can begin to appear at around 2000
meters (6,500 ft) above sea level, such as at many mountain ski resorts, equivalent to a pressure
of 80 kPa. AMS is the most frequent type of altitude sickness encountered. Symptoms often
manifest themselves 6-10 hours after ascent and generally subside in 1 to 2 days, but they
occasionally develop into the more serious conditions. Symptoms include headache, fatigue,
stomach illness, dizziness, and sleep disturbance. Exertion aggravates the symptoms.

2. High altitude pulmonary edema (HAPE) and cerebral edema (HACE) are the most ominous of
these symptoms, while AMS, retinal hemorrhage, and peripheral edema are less severe forms of
the disease. The rate of ascent, altitude attained, amount of physical activity at high altitude, as
well as individual susceptibility, are contributing factors to the onset and severity of high-altitude
illness.
Altitude sickness usually occurs following a rapid ascent and can usually be prevented by
ascending slowly. In most of these cases, the symptoms are temporary and usually abate as
altitude acclimatisation occurs. However, in extreme cases, altitude sickness can be fatal.
The word "soroche" came from South America and originally meant "ore", because of an old,
incorrect belief that it was caused by toxic emanations of ores in the Andes mountains.
Signs and symptoms
1. Headache is a primary symptom used to diagnose altitude sickness, although headache is also
a symptom of dehydration. A headache occurring at an altitude above 2,400 meters (8000 feet =
76 kPa), combined with any one or more of the following symptoms, can indicate altitude
sickness:
 Lack of appetite, nausea, or vomiting
 Fatigue or weakness
 Dizziness or light-headedness
 Insomnia
 Pins and needles
 Shortness of breath upon exertion
 Persistent rapid pulse
 Drowsiness
 General malaise
 Peripheral edema (swelling of hands, feet, and face).
Symptoms that may indicate life-threatening altitude sickness include:
 pulmonary edema (fluid in the lungs):
o persistent dry cough
o fever
o shortness of breath even when resting
 cerebral edema (swelling of the brain):
o headache that does not respond to analgesics
o unsteady gait
o increased vomiting
o gradual loss of consciousness.

3. Severe cases
The most serious symptoms of altitude sickness are due to edema (fluid accumulation in the
tissues of the body). At very high altitude, humans can get either high altitude pulmonary edema
(HAPE), or high altitude cerebral edema (HACE). The physiological cause of altitude-induced
edema is not conclusively established. It is currently believed, however, that HACE is caused by
local vasodilation of cerebral blood vessels in response to hypoxia, resulting in greater blood
flow and, consequently, greater capillary pressures. On the other hand, HAPE may be due to
general vasoconstriction in the pulmonary circulation (normally a response to regional
ventilation-perfusion mismatches) which, with constant or increased cardiac output, also leads to
increases in capillary pressures. For those suffering HACE, dexamethasone may provide
temporary relief from symptoms in order to keep descending under their own power.
HAPE occurs in ~2% of those who are adjusting to altitudes of ~3000 m (10,000 feet = 70 kPa)
or more. It can progress rapidly and is often fatal. Symptoms include fatigue, severe dyspnea at
rest, and cough that is initially dry but may progress to produce pink, frothy sputum. Descent to
lower altitudes alleviates the symptoms of HAPE.
HACE is a life threatening condition that can lead to coma or death. It occurs in about 1% of
people adjusting to altitudes above ~2700 m (9,000 feet = 73 kPa). Symptoms include headache,
fatigue, visual impairment, bladder dysfunction, bowel dysfunction, loss of coordination,
paralysis on one side of the body, and confusion. Descent to lower altitudes may save those
afflicted with HACE.
A person suffering from serious symptoms of altitude sickness has a relatively short period of
time of useful consciousness in which corrective action can be taken. The following is a
correlation of altitude to the amount of time that a person will have useful consciousness:
 ~20,000 ft / 6,100 m = 5-12 minutes (peak of Mount McKinley or Mount Kilimanjaro)
 ~25,000 ft / 7,620 m = 3-5 minutes;
 ~29,000 ft / 8,840 m = 1-2 minutes; (peak of Mount Everest)
 ~40,000 ft / 12,200 m = 9-15 seconds (represents the oxygen that was in a person's
system before the exposure)[6]
Prevention
1. Avoiding alcohol ingestion
As alcohol tends to dehydrate, avoidance in the first 24 hours at a higher altitude is optimal.

4. 2. Strenuous activity
People with recurrent AMS note that by avoiding strenuous activity such as skiing, hiking, etc in
the first 24 hours at altitude reduces their problems.
3. Altitude acclimatization
Altitude acclimatization is the process of adjusting to decreasing oxygen levels at higher
elevations, in order to avoid altitude sickness.[9] Once above approximately 3,000 metres (10,000
feet = 70 kPa), most climbers and high altitude trekkers follow the "golden rule" - climb high,
sleep low.[10] For high altitude climbers, a typical acclimatization regime might be to stay a few
days at a base camp, climb up to a higher camp (slowly), then return to base camp. A subsequent
climb to the higher camp would then include an overnight stay. This process is then repeated a
few times, each time extending the time spent at higher altitudes to let the body adjust to the
oxygen level there, a process that involves the production of additional red blood cells. Once the
climber has acclimatised to a given altitude, the process is repeated with camps placed at
progressively higher elevations. The general rule of thumb is to not ascend more than 300 metres
(1,000 ft) per day to sleep. That is, one can climb from 3,000 (10,000 feet = 70 kPa) to 4,500
metres(15,000 feet = 58 kPa) in one day, but one should then descend back to 3,300 metres
(11,000 feet = 67.5 kPa) to sleep. This process cannot safely be rushed, and this explains why
climbers need to spend days (or even weeks at times) acclimatising before attempting to climb a
high peak. Simulated altitude equipment that produce hypoxic (reduced oxygen) air can be used
to acclimate to altitude, reducing the total time required on the mountain itself.
Altitude acclimatization is necessary for some people who rapidly move from lower altitudes to
more moderate altitudes, usually by aircraft and ground transportation over a few hours, such as
from sea level to 8,000 feet (2,400 m) of many Colorado, USA mountain resorts. Stopping at an
intermediate altitude overnight can reduce or eliminate a repeat episode of AMS.
4. Drugs
Acetazolamide may help some people to speed up the acclimatisation process when taken before
arriving at altitude, and can treat mild cases of altitude sickness. A typical dose is 250 mg twice
daily starting the day before moving to altitude.
A single randomized controlled trial found that sumatriptan may help prevent altitude
sickness.[11]
For centuries, indigenous cultures of the Altiplano, such as the Aymaras, have used coca leaves
to treat mild altitude sickness.

5. 5. Oxygen enrichment
In high-altitude conditions, oxygen enrichment can counteract the effects of altitude sickness, or
hypoxia. A small amount of supplemental oxygen reduces the equivalent altitude in climate-
controlled rooms. At 3,400 m (67 kPa), raising the oxygen concentration level by 5 percent via
an oxygen concentrator and an existing ventilation system provides an effective altitude of 3,000
m (70 kPa), which is more tolerable for surface-dwellers.[12] The most effective source of
supplemental oxygen at high altitude are oxygen concentrators that use vacuum swing absorption
(VSA) technology.[neutrality disputed] As opposed to generators that use pressure swing absorption
(PSA), VSA technology does not suffer from performance degradation at increased altitude. The
lower air density actually facilitates the vacuum step process.
6. Other methods
Drinking plenty of water will also help in acclimatisation[13] to replace the fluids lost through
heavier breathing in the thin, dry air found at altitude, although consuming excessive quantities
("over-hydration") has no benefits and may lead to hyponatremia.
Oxygen from gas bottles or liquid containers can be applied directly via a nasal cannula or mask.
Oxygen concentrators based upon PSA, VSA, or VPSA can be used to generate the oxygen if
electricity is available. Stationary oxygen concentrators typically use PSA technology, which has
performance degradations at the lower barometric pressures at high altitudes. One way to
compensate for the performance degradation is to utilize a concentrator with more flow capacity.
There are also portable oxygen concentrators that can be used on vehicle DC power or on
internal batteries, and at least one system commercially available measures and compensates for
the altitude effect on its performance up to 4,000 meters (13,000 ft). The application of high-
purity oxygen from one of these methods increases the partial pressure of oxygen by raising the
FIO2 (fraction of inspired oxygen).

6. Treatment
The only reliable treatment and in many cases the only option available is to descend.
Attempts to treat or stabilize the patient in situ at altitude is dangerous unless highly controlled
and with good medical facilities. However, the following treatments have been used when the
patient's location and circumstances permit:
 Oxygen may be used for mild to moderate AMS below 12,000 feet (3,700 m) and is
commonly provided by physicians at mountain resorts. Symptoms abate in 12-36 hours
without the need to descend.
 For more serious cases of AMS, or where rapid descent is impractical, a Gamow bag, a
portable plastic pressure bag inflated with a foot pump, can be used to reduce the
effective altitude by as much as 1,500 meters (5,000 ft). A Gamow bag is generally used
only as an aid to evacuate severe AMS patients not to treat them at altitude.
 Acetazolamide may assist in altitude aclimatisation but is not a reliable treatment for
established cases of even mild altitude sickness.
 Some claim that mild altitude sickness can be controlled by consciously taking 10-12
large, rapid breaths every 5 minutes, (hyperventilation) but this claim lacks both
empirical evidence and a plausible medical reason as to why this should be effective .If
overdone, this can remove too much carbon dioxide causing hypocapnia.
 The folk remedy for altitude sickness in Ecuador , Peru and Bolivia is a tea made from
the coca plant.
.
 Other treatments include injectable steroids to reduce pulmonary edema, this may buy
time to descend but treats a symptom, it does not treat the underlying AMS.