Did you know that nearly half of the oxygen held in the Earth’s atmosphere is found below 5500 metres in height? 

This is because gravity holds most of the molecules present in air as close as possible to the Earth.

The higher you climb, the more difficult it will be to find abundant oxygen for human habitation.

This is why we seldom find people living above 6000 metres in height.

Before we get into how altitude sickness affects humans, we are going to take a look at what defines a place as an area of high altitude.

High altitude areas can be divided into 3 parts, depending upon how high one climbs, how severely the altitude affects one’s body:

High altitude (1500-3500 metres)               

At an area of high altitude, ranging from approximately 1500 to 3500 metres, physiological changes start to occur in a climber’s body. These changes include decreased exercise performance, and an increase in the rate of respiration.

It is very common for climbers to get altitude sickness between 2700 to 4500 metres in height due to the large number of people who ascend rapidly to these altitudes.

Very high altitude (3500-5500 metres)

There is a chance of extreme hypoxemia occurring at these levels.

It may occur at any time: during exercise, during sleep, etc.     

Most high altitude illnesses take a severe course at this level of altitude.  

Extreme Altitude (above 5500 metres)             

It is uncommon to find permanent habitation amongst humans at an altitude of 6000 metres above sea level.

Acute mountain sickness

AMS is the mildest form of an illness that is caused by a high altitude. Some symptoms include: Nausea, fatigue, heachaches, dizziness, drowsiness, and insomnia. You may also experience hallucinations, or a tightness in your chest, coupled with difficulty in breathing.

When planning to go on a hike, or an expedition, it is important to follow the process of acclimatisation properly. Acute Mountain Sickness is mostly seen in mountaineers between an altitude of 2700 to 4500 metres as they tend to climb rapidly without proper acclimatisation.

The most serious symptoms of acute mountain sickness arise from oedema, i.e. the accumulation of fluid in body tissues.

Initially, acute mountain sickness does not pose a serious problem, as long as you stay at the same height and acclimatise in a day or two’s time.

However, if your symptoms worsen, it is recommended that you descend, and seek proper medical care.


Causes of acute mountain sickness:

  1. Failure of proper acclimatisation of body
  2. Ascending more than 1200 feet in one day
  3. The body is not physically, and mentally fit to adapt to that environment
  4. If the patient is already suffering from prior diseases of the heart, and lungs.
  5. If anyone has already exerted themselves in an area of high altitude.
  6. Insufficient intake of water, and other fluids.
  7. Low blood cells due to anaemia
  8. Use of sleeping pills, and painkillers which lower the breathing rate


Symptoms of acute mountain sickness:

  1. Headache
  2. Dizziness
  3. Weakness of muscles, and subsequent pain in muscles.
  4. Nausea and vomiting
  5. Rapid heart rate
  6. Swelling of face, hands, and feet.
  7. Shortness of breath
  8. Irritability
  9. Coughing
  10. Chest congestion
  11. Coordination of muscles become weaker
  12. Difficulty in walking properly
  13. Loss of appetite


If these symptoms are not treated properly, they tend to become more severe, day by day, eventually affecting major organs.  



The main reason of acute of mountain sickness is an acute lack of oxygen. It is recommended to use oxygen cylinders to help in maintaining the level of oxygen in the human body at an area of high altitude.

Don’t ascend more if a patient is suffering from acute mountain sickness. Continue stay at the same height to help them acclimatise, or descend if possible.

If the patient is having problem breathing, give them some Diamox(Acetazolamide). If the patient is having a headache, you should give them either Paracetamol/Tylenol (acetaminophen) or Ibuprofen/Advil instead on the recommendation of a doctor.

The patient should be given Dexamethasone to decrease any brain swelling that may be present.

Make sure to drink plenty of water to hydrate the body.



  1. Make sure that you are physically fit to adapt to the new climate.
  2. Follow the proper course of acclimatisation.
  3. Drink at least 3 to 5 litres of water daily.
  4. Eat healthy types of food, especially those which can be easily digested at high altitude.
  5. Don’t keep walking continuously. Make sure to rest a little every 15 to 20 minutes.
  6. Try to sleep at a lower altitude.
  7. Avoid alcohol, and smoking cigarettes when in a high altitude area.


Emergency measures

  1. Use of Diamox or Lasix as a diuretic.
  2. Use of analgesics for headaches.
  3. Descend if possible  
  4. Use of HAPO bag if necessary


High altitude pulmonary oedema (HAPO)

Photo by Pixabay

High altitude pulmonary oedema is a life-threatening form of altitude sickness.  

The illness entails an accumulation of fluids in one’s lungs. If not treated properly, or on time, it may become severe.


Symptoms of High Altitude Pulmonary Oedema:          

  1. Breathlessness at rest
  2. A band like pain across your chest
  3. Wheezing or rattling Sounds produced from the lungs during breathing because of fluid present in the lungs
  4. A feeling of heaviness in your chest
  5. Fast rate of respiration
  6. Swelling in hands and feet
  7. Nails start getting blue in colour
  8. Inability to walk properly
  9. Faster heart rate than normal



For those who are already suffering from HACO(high altitude cerebral oedema) dexamethasone may provide temporary relief from symptoms of HAPO.

If the symptoms are not severe, then it is recommended to stay at the same height to help the patient acclimatise and get better./

If the degree of illness goes up, then it is necessary to descend as soon as possible.      

You may use cylinders of oxygen as it may give some relief  to the patient.

Giving the patient Diamox or Lasix 125 mg twice a day will  help to flush the fluids out with urine.

Use HAPO bags as it will increase the pressure. The patient will feel like he/she is at an  atmospheric pressure that is equal to that of sea level.   

Drink plenty of water – at least 3 to 5 litres per day.

Nifedipine (procardia), a medication usually given for high blood pressure has been shown to be beneficial for patients of high altitude pulmonary oedema. A dose of Nifedipine 20 mg taken once every 8 hours may prevent HAPO.

Antibiotics may be given if a fever or a lung infection is detected.



  1. It is recommended to start taking diamox at least two days prior to reaching an area of high altitude.
  2. Make sure you drink at least 3 to 5 litres of water per day.
  3. Ascend slowly or stay at same height until you are fully acclimatised.
  4. Take medications as prescribed
  5. Avoid any heavy activity on the first day of arrival.
  6. Avoiding alcohol and smoking cigarettes in high altitude areas.


Emergency measures

  1. Keep in observation for 24 hours
  2. Seek medical attention immediately if symptoms worsen or if new symptoms develop
  3. supply oxygen regularly to the patient
  4. Keep the body well hydrated
  5. Use a HAPO bag to stabilise the patient.


High altitude cerebral oedema(HACO)

Photo by Pixabay

High altitude cerebral oedema (HACO) is a life threatening form of altitude sickness that occurs when you gain altitude too fast. The illness entails an accumulation of fluid in one’s brain.

As a non cardiogenic form of an oedema, it is often considered to be one of the most severe forms of Altitude Sickness, sometimes even being the end stage.


Symptoms of high altitude cerebral oedema:

  1. The most primary symptom of a cerebral oedema is a headache.
  2. Loss of consciousness
  3. Increase in nausea and vomiting
  4. Retinal haemorrhage
  5. Fatigue
  6. Loss of coordination
  7. Illusion
  8. Dizziness
  9. Bowel dysfunction
  10. Coma
  11. Confusion
  12. Hallucinations
  13. Drowsiness



Provide a continuous supply of oxygen to the patient.

If the patient is having a headache, you may give them an aspirin.

Use Diamox if a diuretic is needed.

Use HAPO bags to help the patient stabilise as it will keep them at a pressure  equivalent to that of sea level.

Some steroids, particularly dexamethasone may be effective in relieving symptoms.



The prevention of all altitude sicknesses requires ascent at a gradual rate allowing time for acclimatisation. A general guideline is that at an altitude greater than 3000 metres, one should not spend subsequent nights more than 300 metres higher than the previous night.

A rest day is  recommended every 2 to 3 days. Anyone who shows symptoms of AMS should not ascend until their symptoms improve.

Most climbers usually prefer to follow the proper process of acclimatisation rather than use Diamox or other medicines because it may leave side effects on one’s body.

Peripheral Oedema

Photo by Pixabay

Peripheral oedema is the accumulation of fluid in one’s face, and limbs due to a gain in altitude. When one’s body starts to retain excessive fluids, it starts to collect in various tissues that may impede normal biological function.

However, due to gravity, one’s limbs are the most easily affected parts of the body apart from one’s brain, lungs, or heart. Severe swelling may lead to a permanent damage of nerves if not treated in time.


Early signs or Symptoms of Peripheral Oedema:

  1. Arms or legs start feeling full, or heavy.
  2. Arms and legs start to look swollen.
  3. The affected area becomes warm.
  4. The affected part may be very difficult to move.
  5. When you press a swollen area, it leaves a dent.
  6. Clothing or jewellery starts to feel tight and uncomfortable.
  7. The skin near the oedema feels tight or warm.



Peripheral Oedema tends to resolve spontaneously with descent.

Remove any jewellery you can, and change out of any tight clothes as soon as possible. Keep taking regular breaks when out on a trek, drink plenty of water, and lessen your salt intake while eating.

If needed, the patient may be given a diuretic like Diamox to help with flushing out unwanted fluids.

Elevate any affected body parts above the level of the heart to help in reducing swollen areas.

If a patient has had a sudden, or painful onset of peripheral oedema, it is recommended that you descend and get proper medical care as soon as possible.


Over to you


Do you have any other suggestions on how we should treat these illnesses? Let us know at hello@climbingtrails.com so we can share!

Similar Posts

1 Comment

  1. Just in Time for this post. One of my friend who is going to rock up the mountain in western Australia this month . I will definitely mention these tips regarding high altitude sickness. although he is regular rock climber in Climbfit Kirrawee an indoor bouldering gym, yet this is his first maiden outdoor hike.

    Really useful stuff.

Penny for your thoughts?