Altitude Sickness

Altitude Sickness in Mountain

Altitude sickness in Mountain – to know about the safety measures to avoid AMS and to understand the basic  medical treatments once AMS hits you are most important things for you before trekking in Nepal. The Acute Mountain Sickness is an illness caused due to gain in elevation. Compared to sea level the amount of oxygen in higher altitude is less and the oxygen level goes thinner as trekkers continue to gain higher altitude. Here we have listed the details of AMS please have a look.


The symptoms of AMS are can be several. They vary from person to person. However, general symptoms of AMS are as follows. If you are seen with, any of these symptoms do not delay to identify the illness and go for the quick treatment ASAP.

  • Difficulty sleeping
  • Dizziness or light-headache
  • Fatigue
  • Headache
  • Loss of appetite
  • Nausea or vomiting
  • (heart rate) Rapid pulse
  • with exertion Shortness of breath

Severe cases of AMS may lead you to HAPE (High Altitude Pulmonary Edema) or HACE (High Altitude Cerebral Edema). HAPE hits your respiratory system where as HACE hits your Nervous System.

Symptoms that may occur with more severe acute mountain sickness include:

  • Blue color to the skin (cyanosis)
  • Chest tightness or congestion
  • Consufion
  • Cough
  • Coughing up blood
  • Withdrawal from social interaction
  • Gray or pale complexion
  • Cannot walk in a straight line, or walk at all
  • Shortness of breath at rest

Related Oxygen Rate at Different Altitude
Altitude    Oxygen Rate
In Meters    In Feet
8.850    29.035    33%
8.000    26.247    36%
7.000    22.966    41%
6.000    19.865    47%
5.500    18.045    50%
5.200    17.061    52%
5.000    16.404    53%
4.500    14.764    57%
4.000    13.123    60%
3.500    11.483    64%
3.000    9.843    68%

Sea Level    100%


  • HACE or HAPE occur in approximately 1 to 2% of people going to high altitude
  • HAPE and HACE may occur alone or together
  • HAPE is roughly twice as common as HACE
  • HAPE causes many more deaths than HACE
  • HAPE may appear without any preceding symptoms of AMS
  • HAPE is more likely in people with colds or chest infections
  • HAPE often comes on after the second night spent at a higher altitude
  • HAPE can develop even after descending from a higher altitude
  • HACE usually develops after symptoms of AMS have appeared and often gets rapidly worse during the night
  • HACE may develop in the later stages of HAPE
  • HACE (High Altitude Cerebral Edema)

HACE is caused by an accumulation of fluid in or around the brain. Typically, symptoms and signs of AMS become worse and HACE develops. Someone with HAPE may also develop HACE.


  • Severe headache, which often feels worse on lying down and is not relieved by ibuprofen, paracetamol or aspirin
  • Tiredness, severe fatigue
  • Nausea and or vomiting which may be severe and persistent
  • Loss of coordination, clumsiness. The victim needs help with simple tasks such as tying their shoelaces or packing their bag. They cannot do the finger-nose test
  • Staggering, falling. They cannot do the heel to toe walking test or the standing test
  • Blurred or double vision, seeing halos around objects
  • Loss of mental abilities such as memory. They cannot do a simple mental arithmetic test
  • Confusion, hallucinations
  • Change in behavior (aggression, apathy, etc.)
  • Drowsiness, difficult to wake up, coma, death


Heel-to-toe walking test: The victim is asked to take 10 very small steps, placing the heel of one foot to the toes of the other foot as they go. Reasonably flat ground is necessary and the victim should not be helped

Standing test: The victim stands with eyes closed, feet together and arms by their sides

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 (a useful test if the victim is in a sleeping bag)

Mental arithmetic test: Give the victim a mental arithmetic test, eg. subtract 7 from 100, 7 from 93, and so on (but remember some people may be poor at arithmetic even at sea level)

If the victim cannot do any of the above tests easily (or refuses to cooperate), or show excess wobbling or falling over in the two first tests (be prepared to catch the victim if they fall over!), assume they are suffering from HACE. If in doubt about the victim performance, compare with a healthy individual. Be prepared to keep repeating these tests.


Descend immediately (prompt descent will begin to reverse the symptoms). Descend as low as possible, at least 1000m /3280 ft. Descend at night or in bad weather if necessary. Carry the victim if possible, as the exertion of walking can make the illness worse

If descent is not immediately possible (eg. dangerous terrain or weather, not enough helpers or while waiting for a helicopter), oxygen or the use of a PAC and appropriate medications will keep the person alive until descent can be undertaken


  1. From a bottle using a mask (2 to 4 L/min)
  2. By using a pressure bag (this is roughly the equivalent of 2 to 4 L of oxygen/min)

NB: If both oxygen and a pressure bag are available, give the oxygen while the bag is being prepared and after the victim comes out of the bag. Do not give oxygen inside the bag unless it is designed for this purpose and you have been trained to do so.


  1. 8 mg of dexamethasone at once (by mouth, IV or IM) followed by 4 mg 6-hourly. Dexamethasone takes several hours to work. Stop it once below 2500m/8200ft AND after at least 3 days of treatment by tailing off the dose slowly (give the last 3 doses 12-hourly)
  2. Diamox 250 mg 8 to12-hourly
  3. Treat persistent vomiting with anti-vomiting medication

Prop the victim up in a semi reclining position as lying down flat may make their condition worse

Avoid even the slightest exertion if this is possible. Even walking a few steps may make their symptoms worse or reappear. Do not leave the victim alone.

If a person is turning blue or is falling into unconsciousness, give them rescue breathing before they stop breathing


Symptoms of HAPE are due to the accumulation of fluid in or around the lungs. It 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. HAPE can easily be mistaken for a chest infection or asthma: if in doubt treat for both.


A reduction in physical performance (tiredness, severe fatigue) and a dry cough are often the earliest signs that HAPE is developing breathlessness.

In the early stages of HAPE, this may mean just taking a bit longer to get one breath back on resting after mild exercise. Later on, there is marked breathlessness with mild exercise. Finally, breathlessness occurs at rest. Record the respiratory rate (NB: At 6000m/19700ft, acclimatized respiration rate is up to 20 breaths per minute)

The dry cough may later become wet with frothy sputum, which may be bloodstained (pink or rust colored). This is a serious sign

Wet sounds in the lungs when breathing in deeply (place your ear on the bare skin of the victim back below the shoulder blades; compare with a healthy person).

Note: There may be NO wet sounds in even quite severe HAPE: this is called dry HAPE.

There may be: mild fever up to 38.5ºC, a sense of inner cold, pains in the chest

Blueness or darkness of face, lips, tongue or nails due to lack of oxygen in the blood (cyanosis)

Drowsiness, difficulty waking up, coma, death


Same general treatment as for HACE, EXCEPT: Use oxygen or the PAC and appropriate medications will keep the person alive until descent can be undertaken


  1. Nifedipine. This should only be used if bottled oxygen or a pressure chamber is not available and the victim is warm and well hydrated. Give the modified release (MR) form of the tablets (20 mg 12-hourly for 2 or 3 days). If a fall in blood pressure occurs due to nifedipine (pallor, weak rapid pulse, dizzy on standing), treat as shock
  2. Diamox 250 mg 8 to 12-hourly
  3. An asthma reliever spray (2 puffs 4-hourly) may help