At higher elevations, atmospheric pressure decreases: there is so much less available oxygen for the body. The oxygen quantity reachable at 3,000 meters corresponds to the two thirds of that accessible at sea level. At 5,000 meters, it is half lower.
Why do low oxygen levels cause altitude sickness?
Altitude sickness is the name given to the human body’s physiological reactions that occur as a result of low oxygen pressure that exists at high altitudes.
The body actually reacts to this shortage of oxygen in two steps.
Heart rate acceleration and ventilation regularity to get more oxygen and convey it more quickly to concerned organs. This response is costly for the body on the energy level because respiratory muscles and heart are more requested.
The immediate effect is replaced or completed by a more economic body mechanism: the increase of the number of oxygen mover i.e. red blood cells. It is a quite long process which requires spending at least one week at high altitude to see a result. The frequency of heart rhythm then slows down, without recurring however to the basic values.
The problem of Acute Mountain Sickness starts when acclimatization does not keep pace with your ascent to high altitude. This happens when you ascend too quickly or go from sea level to high altitudes in a day and your body cannot get as much oxygen as it needs or is accustomed too.
Who can get altitude sickness?
Anyone who goes to high altitude can get altitude sickness. It is primarily related to individual genetics and how fast you go up. There is no difference in age, gender, physical fitness, or previous visits.
Some people acclimatize quickly, and have no problems; others acclimatize slowly and feel bad for a few days and others progress to the more serious forms. There is no way to predict who is likely to get sick at high altitudes.
It is considered that high sickness affects approximately
• 15 % of people at 2,500 meters;
• 60 % of people at 4,000 meters;
• everybody at very high altitude (more than 5.000 meters).
Symptoms of altitude sickness
The reaction to the height is proper to every individual. Most patients have mild symptoms and acute mountain sickness is characterized by diverse disorders which arise separately or associated to others; they appear from the first hours of the stay at high altitude.
Symptoms of Altitude Sickness include:
• Headache (headache)
• Fatigue (physical exhaustion)
• Sleep Disorder / insomnia
• Nausea and Vomiting
• decreased appetite / Digestive Disorders
These symptoms, frequent and normal, fade away generally from themselves (or at least fall mostly) after a few hours at high altitude and by taking analgesic.
In some rare cases serious complications can occur:
- High altitude pulmonary oedema: When this happens, the sufferer becomes progressively more short of oxygen, which in turn worsens the build-up of fluid in the lungs. 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. Typically the sufferer will be more breathless compared to those around them, especially on exertion.
- High altitude cerebral oedema: it 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. A person with high altitude cerebral oedema 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. High altitude cerebral oedema should also be suspected if a companion starts to behave irrationally or bizarrely.
Those are extreme forms of high altitude diseases which call for an urgent action:
- Descent is the most effective treatment and should not be delayed ;
- Seek advice from a specialized doctor; some drugs can be helpful, but should only be used by trained doctors.
Unfortunately, it is currently impossible to predict who will be affected, about a case of severe crisis every two years approximately (it arises generally from the first days at high altitude). Our teams of guides are qualified to diagnose oedemas when they arise, and to react in a most appropriate way.
A physical training is recommended before a stay at high altitude. Gain a good physical state through biking, swimming or hiking (if possible at high altitude) would constitute a good training.
Seek advice from your usual doctor so that he detects possible deficiencies or affections. Possibly check with a centre specialized in mountain medicine.
How to Acclimate to High Elevation
Higher Elevation Requires Adjustment; to limit the effects of the altitude sickness and limit the risks of worsening, two golden rules are to be respected:
o Increase elevation gradually. One week at high altitude is generally enough for a fine acclimatization. Your program should be smooth, with, in the first days, activities or short testing excursions, near care centres if necessary and possible rest times;
o It is recommended beyond 3,500 meters to increase your elevation slowly – 700 meters per day, including one night of sleep at each level.
In the first days:
- Particularly the first 24 hours try to save your strengths, move slowly;
- Do not make useless or gratuitous physical efforts «to test» you, even when you feel in good shape (it can favour the appearance of mountain sickness).
During a trek or an ascent
- Avoid the aggressive efforts (big footstep, jumping, running);
- Limit physical exertion -- activity increases the body's oxygen demand, and less oxygen is available in the thinner air at higher elevations;
- To sleep well, once arrived at the campsite, go up 200 to 300 meters without bag, stay there one hour and come down again;
- In case of suffering (with the exception of headaches relieved by tablets), it is essential to stop rising and resting;
- If the signs persist, it is then needed to get down again from 300 to 400 meters, and to take back the progress only the next day if the signs disappeared; should the opposite occur, it is important to give up pursuing the trek or the ascent.
Stay hydrated by drinking 3 to 4 quarts of water per day. Avoid alcohol for the first two days once you've arrived at your destination. The altitude makes you dehydrated and alcohol will make the dehydration worse. The effects of alcohol can also be stronger at a higher altitude.
- Balanced food;
- Take a copious and complete breakfast;
- Get fresh supplies regularly;
- For your first meal at high altitude, eat light.