Saturday, April 16, 2011


When a person ascends to altitudes above 2000m, the body has to acclimatize to the decreasing amount of Oxygen available. The three main acclimatization mechanisms are:
Deeper breathing and an increased respiratory rate (from 8 to 12 breaths/min at rest at sea level to around 20 breaths/min at 6000m). This starts immediately on arrival at altitude Producing more urine. This starts after few hours and takes a day or two. If this mechanism is not efficient, the characteristic puffiness of early AMS appears in the face, hands and feet (water retention) An increase in the number of red cells in the blood. This only begins after a week at high altitude. If the ascent is too fast and/or the height gain too much, these mechanisms do not have time to work and symptoms and signs of altitude illness (also called high altitude illness or altitude sickness) will appear. Altitude illness becomes common above 2500m and presents in the following ways:

AMS (Acute Mountain Sickness): common but not life-threatening if dealt with correctly
HACE (High Altitude Cerebral Edema): less common but life-threatening
HAPE (High Altitude Pulmonary Edema): less common but life-threatening

Depending on the altitude gain and speed of ascent, the incidence AMS ranges from 20 to 80%. HAPE is roughly twice as common as HACE and together they occur in approximately 1 to 2% of people going to high altitude. These three forms of altitude illness can vary from mild to severe, and may develop rapidly (over hours) or slowly (over days). HACE and HAPE can occur individually or together.
People often refuse to admit they have altitude illness and blame their symptoms on cold, heat, Infection, alcohol, insomnia, exercises, unfitness or migraine, and risk death by continuing to ascend.

Warning: do not ascend with symptoms or signs of altitude illness, as this has led to many deaths from
In any group there will be ‘fast’ and ‘slow’ acclimatizers needing different ascent rates. While a flexible
schedule is always preferred, the fact is that many trekkers are on tight schedules (often, but not always, members of commercial groups) leading to a higher incidence of altitude illness. Slow acclimatizers in these tight schedule situations are at extra risk, and prompt diagnosis and treatment becomes even more important. However, even if a trekker has a flexible schedule, they may still feel pressurized to ascend with symptoms (by pride, peer pressure, rivalry, not wanting to appear weak, etc). Interestingly, fit and impatient young people can be more at risk of altitude illness than unfit and patient older ones! Flexible schedule Tight schedule

AMS varies from mild to severe and the main symptoms are due to the accumulation of fluid in and
around the brain. Typically, symptoms appear within 12 hours of the ascent. If the victim now rests at
the same altitude, symptoms usually disappear quickly over several hours (but for ‘slow acclimatizers’
this can take up to 3 days!) And they are now acclimatized to this altitude. AMS may reappear as they
ascend higher still, as acclimatization to the new altitude has to take place all over again.
Symptoms & signs
A diagnosis of AMS is made when there has been a height gain in the last few days, AND:
The victim has a headache (typically throbbing, often worse when bending over or lying down)
PLUS there is one or more of the following symptoms:
− Fatigue and weakness
− Loss of appetite, or nausea, or vomiting
− Dizziness, light headedness
− Poor sleep, disturbed sleep, frequent waking, periodic breathing
In AMS, the victim’s level of consciousness is normal. The Lake Louise Score can be helpful as a guide to quantify your diagnosis of AMS and assess progression.
Note: AMS and HACE are two extremes of the same condition and it can help to think of AMS as ‘mild
Note: the only early signs of altitude illness in a young child (under 7 years old) may be an increased
fussiness, crying, loss of interest and/or loss of appetite.
HACE is the accumulation of fluid in and around the brain. The important symptoms and signs are: severe headache, loss of physical coordination and a declining level of consciousness.
Typically, symptoms and signs of AMS become worse and HACE develops (but HACE may come on so quickly that the AMS stage is not noticed). Also, HACE may develop in the later stages of HAPE.
Symptoms & signs
A diagnosis of HACE is made when there has been a height gain in the last few days, AND:
The victim has a severe headache (not relieved by ibuprofen, paracetamol or aspirin)
There is a loss of physical coordination (ataxia):
− Clumsiness: the victim has difficulty (and often asks for help) with simple tasks such as tying their
shoelaces or packing their bag. When examined they fail to do, or have difficulty doing (or refuse to do!) the finger-nose test
− Staggering, falling over. When examined they fail to do, or have difficulty doing (or refuse to do)
the heel-to-toe walking test or the standing test
Their level of consciousness is declining:
− Early on, this presents as loss of mental abilities such as memory or mental arithmetic. When asked, the victim cannot do or have difficulty doing (or refuse to do) simple mental tests
− Later on, they become confused, drowsy, semiconscious, unconscious (and will die if not treated
urgently) Other symptoms and signs that may appear:
− Nausea and/or vomiting, which may be severe and persistent
− Changes in behaviour (uncooperative, aggressive or apathetic, “Leave me alone”, etc)
− Hallucinations, blurred or double vision, seeing haloes around objects, fits or localized stroke signs
may all occur but are less common

Failure or difficulty doing any one of these tests means the victim has HACE. If the victim refuses to
cooperate, assume they are suffering from HACE. If in doubt about the victim’s performance of the tests, compare with a healthy person. Be prepared to repeat these tests to monitor progress.
• Finger-nose test. With eyes closed, the victim repeatedly and rapidly alternates between touching
the tip of their nose with an index finger, then extending this arm to point into the distance (useful test if the victim is in a sleeping bag or cannot stand up).
• Heel-to-toe walking test. The victim is asked to take 10 very small steps in a straight line, placing the heel of one foot in front of the toes of the other foot as they go. Reasonably flat ground is necessary and the victim should not be helped, but be prepared to catch the victim if they fall over! Excessive wobbling is difficulty (to do the test), falling over is failure.
• Standing test. The victim stands, feet together and arms folded across their chest, and then closes their eyes (the victim should not be helped, but be prepared to catch the victim if they fall over! Excessive wobbling is difficulty (to do the test), falling over is failure.
• Mental tests are used to assess level of consciousness. You must take into consideration preexisting
verbal/arithmetic skills and culture; it is a decline in ability over time that is significant.
Examples of tests include: “Spell your name backwards”, “Take 3 from 50 and keep taking 3 from
the result”, or ask their birth date, about recent news events, etc.

HAPE is the accumulation of fluid in the lungs. The important sign is breathlessness. HAPE may appear
on its own without any preceding symptoms of AMS (this happens in about 50% of cases) or it may develop at the same time as AMS or HACE. Severe cases of HAPE may result in the development of
HACE in the later stages.
HAPE may develop very rapidly (in 1 to 2 hours) or very gradually over days. It often develops during or after the second night at a new altitude. HAPE can develop while descending from a higher altitude. It is the commonest cause of death due to altitude illness. HAPE is more likely to occur in people with colds or chest infections. It is easily mistaken for a chest infection/pneumonia. If you have the slightest doubt, treat for both.
Symptoms & signs
Reduced physical performance (tiredness, fatigue) and a dry cough are often the earliest signs of HAPE
− Early stages: more breathless than usual with exercise, takes a little longer to get breath back after exercise
− Later stages: marked breathlessness during exercise, takes longer to get breath back after exercise. This finally progresses to breathlessness at rest
− At any stage, the victim may become breathless while lying flat and prefer to sleep propped up

Breathing rate at rest increases as HAPE progresses. (At sea level, resting breathing rate is 8 to 12 breaths/min at rest. At 6000m, normal acclimatized resting breathing rate is approximately 20 breaths/min) A dry cough As HAPE gets worse; the cough may start to bring up white frothy sputum. Later still, this frothy sputum may become bloodstained (pink or rust coloured): this is a serious sign ‘Wet’ sounds (fine crackles) may be heard in the lungs when the victim breathes in deeply (place your ear on the bare skin of the victim’s back below the shoulder blades; compare with a healthy person)
Note: wet sounds may be difficult to hear (or absent), even in severe HAPE
As HAPE gets worse, lips, tongue or nails may become blue due to lack of oxygen in the blood
There may be: fever (up to 38.5ÂșC), a sense of inner cold, or pains in the chest or even upper belly
As HAPE worsens, the victim becomes confused, drowsy, semiconscious, and unconscious (and will die if not treated urgently)

The Author, Shauky Putoo is a full time adventurer & has been organising activities in Very High Altitudes in Greater Himalayas, trained in wilderness medicine, rescue & Basic Life Support Systems, apart from being a coach for mountain, aquatic & aero sports. presently looking after Operations of O2 Adventure & Travels, & can be contacted via email to or +91 9419550663.

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