With increasing altitude, the air pressure and the absolute (not relative) oxygen content per cubic meter of air decrease. At an altitude of 5000 m, the oxygen partial pressure is only half that at sea level.
For the height problem, a distinction is made between different height levels:
- 0 – 3000 m: medium altitude. Generally only minor problems above 2500 m.
- 3000 – 5000 m: high altitude, problems with altitude occur, but full acclimatization possible up to approx. 5300 m.
- 5000 – 7500 m: very high altitude. Only incomplete acclimatization is possible.
- above 7500 m: death zone. Acute loss of strength, only short stay possible.
Due to the above conditions, less oxygen is absorbed into the body through the lungs. The oxygen content in the blood decreases. The body tries to compensate for the deficiency by increasing the heart rate and breathing more.
The body reacts: Breathing becomes deeper and faster -> more air gets into the lungs -> oxygen partial pressure in the alveoli increases -> carbon dioxide concentration in the blood decreases -> acid/base balance in the body is disturbed -> more hydrogen carbonate is excreted to reduce the PH – keep the value constant. Reactions begin about 1/2 day after reaching critical levels.
In addition, the number of (oxygen-transporting) red blood cells (by up to 30-50%) is increased in a slower process (4-5 days) (risk of thrombosis).
Normally 20-30% of the blood capillaries are inactive. In the case of altitude sickness, some of them are activated to better supply the tissue with blood. At the same time, the anaerobic (oxygen-independent) metabolism is promoted.
The AMS (Acute Mountain Sickness) can cause severe problems from 3000 m. One or more of the following symptoms may occur: fatigue, headache, dizziness, hallucinations, insomnia, and loss of appetite, vomiting, dry cough with sputum, and blue/grey discoloration of the lips and nail beds (cyanosis).
In order to supply the brain with enough oxygen, the blood flow is increased. The pressure in the brain increases -> headaches. Since the blood is needed elsewhere, the gastrointestinal tract is undersupplied -> nausea, loss of appetite, and vomiting.
Cheyne-Stokes breathing: The depth of breathing increases in stages, followed by a pause in breathing of 5-50 seconds -> oxygen levels continue to decrease (especially during sleep when breathing cannot be controlled). The problems get worse.
Altitude sickness often worsens overnight. Usually, the symptoms subside after a while. Relief can only be achieved by descending to lower altitudes.
Slow acclimatization is important. One should sleep 2-3 nights below 3000 m. For tours at high altitudes, acclimatization days should be planned.
Climb high – sleep low: The climber should only increase the sleeping altitude by 500-600 m at a time. Intermittent climbing is more beneficial than harmful if not overdone.
After 10 days, the average adjustment increases to 80%, and after another 5 weeks to 95%.
Nutrition: Drinking a lot is crucial, at least 4-7 liters/day, this dilutes the thickened blood and helps to adjust the pH value in the body. Little coffee/alcohol, little fat, lots of vitamins and carbohydrates.
Eat enough but not too much; It is better to eat a little more often than to fill your stomach! A lot of oxygen is burned during digestion.
Avoid overexertion from the start of the tour, walk extremely slowly, take small steps, and keep your pulse as low as possible from day one. Move like the sloths! If you only start when you are slowed down by the height, it is often too late.
Control your breathing, breathe through your nose if possible (dehydration, cold). Telescopic sticks can make breathing easier.
Good sun protection is important at high altitudes. The symptoms of altitude sickness are often exacerbated or superimposed by exposure to the sun, exhaustion, or dehydration.
HAPE = high altitude pulmonary edema. accumulation of water in the lungs. Water is squeezed out by high blood pressure. The onset of high-altitude pulmonary edema is possible from 2500-3000 m. Symptoms usually begin 24-96 hours after the start of the ascent. Shortness of breath on exertion and dry cough (as in AMS), pulse, and respiratory rate continue to rise, and signs of cyanosis are possible.
Later, the shortness of breath persists even with little exertion, and general exhaustion. Headache, severe cough, loss of appetite. Nail bed cyanosis, rales in the lungs (stethoscope). Listen: place the ear between the shoulder blades of a patient who is to breathe deeply. Comparison with a healthy person.
Late resting shortness of breath, pulse over 110/min (normal 60-80), respiration rate over 30 (normal 14-18). Bubbling in the lungs, cough mixed with secretion, in extreme cases bloody, bright red foam. pain in the chest area. Risk of Cheyne-Stokes breathing (see above), unconsciousness possible.
Risk of death! Immediate helicopter evacuation. Oxygen administration 6 l/min. Descent at least 1000 m. Transport in a semi-sitting position, breathing easier. Fighting panic in the patient. Keep warm, as cold can also trigger stress. Avoid any exertion for 2-3 days after the descent.
HACE = high-altitude cerebral edema, relatively rare, possible from 3500 m, usually from 5000 m. The brain mass swells due to the accumulation of fluid and dead brain cells. Symptoms are visual disturbances, headache, numbness in extremities, coordination difficulties, memory loss, arithmetic problems, extreme fatigue, prolonged repeated vomiting, nausea, cyanosis, and seizures.
The headaches associated with HACE are unresponsive to painkillers and are worse when lying down.
Risk of death! Evacuate immediately. Transport lying down with the head slightly elevated. give oxygen.
Dehydration reduces blood volume at high altitudes, and red blood cells (which the body produces more at high altitudes) can stick together. Blockages can cut off the blood supply.
Long waiting times in the tent and tight clothing support thrombi, especially in the legs/calves. A painful swelling develops, and the part of the body behind the arterial thrombus becomes white and cold. Erupting thrombi can cause a pulmonary embolism.
Prevention: Plenty of fluids (4-7 liters/day), exercise. Measures: loosen clothing, stop clotting with aspirin, and transport to a lower altitude.
Also encountered problems
- peripheral high-altitude edema
- retinal hemorrhages
- higher tendency to frostbite
Adaptation cannot be trained. Nevertheless, it is good if you have often been at high altitudes (over 2,500 m) within the last 6 months before the decisive tour.
Climb High – Sleep Low is an old rule. In my experience, however, it is disadvantageous if you climb too high between overnight stays. This uses a lot of oxygen. It is better to overcome only moderate increases in altitude during the day.
- Don’t climb too fast.
- No anaerobic effort in the adaptation phase.
- Daily sleeping height gains a maximum of 300 – 500 m.
- An additional rest day every 1000 m.
- If possible, do not use climbing aids.
- High hydration (4-7 liters/day).
- carbohydrate-rich food.
- Don’t go up until symptoms go down! (Watch out for signs of height issues!)
The adjustment can be influenced by the form of the day, fitness, and psychological factors. Young and fit athletes in particular often have problems because they don’t take height seriously.
Up to an altitude of approx. 5,500 m, you can fully acclimate over time (18-20 days). With less than 7 days you are in the critical area at this altitude!
With a pulse oximeter, for example, the inexpensive device Pulox PO-100 Solo for a good 20 €, you can check the pulse and oxygen saturation in the blood quickly and easily. This provides information about successful or unsuccessful acclimatization.
sign of adjustment
- Training endurance
- Resting heart rate dropped back to personal normal value (measure beforehand!)
- Deep breathing at rest and under stress
- periodic nocturnal breathing
- adequate altitude diuresis (urge to urinate)
Anyone can get altitude sickness, but nobody has to die from it!
- In case of doubt, every health problem is related to altitude! Any serious illness is AMS unless clearly stated otherwise!
- Only climb higher without symptoms!
- If it deteriorates, descend 500 – 1000 m immediately!
- Don’t run into traps, such as high valleys, from which you can only get out over even higher passes.
- Never leave altitude-sick people alone!
In case of emergency
Descend 1000 hm, oxygen 2-4 l/min., 250 g Diamox 2 x per day
Gamow Bag: The person comes in the sack, and the sack is pressurized with a hand or foot pump. This method alleviates problems in mild AMS, but can also buy time in more severe cases. Problem: claustrophobia, drum cases can burst. Duration of treatment maximum 4-6 hours.
The medications commonly used to treat altitude sickness are:
- acetazolamide (used to prevent or treat “acute mountain sickness”)
- Nifedipine (mainly used for high-altitude pulmonary edema)
- Dexamethasone (mainly used for high-altitude cerebral edema)
The remedies can improve the symptoms of altitude sickness, but also mask the warning signs!! A serious hazard to the body from climbing to dangerous heights is no longer sufficiently perceived so altitude sickness can take a serious and life-threatening course.
Normal prophylaxis: 250 – 500 mg Diamox (acetazolamide) per day, starting the day before ascending. Duration of intake until descent. Supply plenty of fluids. Do not combine with high doses of ASA (Aspirin or Alcacyl). Do not use if allergic to sulfonamides.
dr Holzer writes: “Acetazolamide (Diamox®) is mainly used for prophylaxis. This carbonic anhydrase inhibitor leads to metabolic acidosis and thus to stimulation of the respiratory center with a reduction in the periodic breathing that is typical at altitude. 125 mg twice a day to Acetazolamide 250 mg twice daily starting the day before crossing the 2500 m limit until returning to that altitude.”
Alternative possible prophylaxis: 1/4 Tbl Diamox 250 once in the morning (or 2 x 1/2 250 tablets per day). Start the day before the ascent to the day after the descent. Symptoms are said not to be disguised. You should still keep an eye out for any signs of altitude sickness!
In extreme conditions and certain tactics, Diamox worsens the adaptation!
Prophylaxis of high-altitude pulmonary edema: Adalat-CR-30-60 once a day.
In case of emergency
Active substance Acetazolamide (Diamox) :
dr Holzer writes: “In mild cases, therapy can be carried out with 2 times 250 mg acetazolamide or prednisolone 50 mg (e.g. Spiricort®) every 8 hours, severe cases are treated with a bolus of dexamethasone (Decadron®) 8 mg iv followed by 4 mg every Treated orally for 4 to 6 hours. Descending to an altitude below 2500 m above sea level is very important in any case.”
Anyone who takes Diamox longer should take calcium at the same time to avoid muscle problems! Drink a lot!
Therapy HACE: Immediately down by 1000 m. Dexamethasone (Fortecortin, tab. a 4 mg, initially 2 tabs., then every 6-8 h 1 tab.) or prednisone (tab. a 50 mg, 1 tab., then all 8-12 h 1/2 tab.)
Therapy HAPE: immediately down by 1000 m. In case of severe symptoms and/or delay in the descent, nifedipine retard (Adalat retard, 20 mg) 1 tab. every 6 hours. Only swallow Adalat 10 mg in a life-threatening condition and repeat this if necessary after 15-20 minutes. Attention: this can lead to a severe drop in blood pressure in sensitive people!
Aspirin is not without its problems because of its blood-thinning properties. It is even very dangerous if internal bleeding occurs. Ingestion may delay necessary surgeries.
Ibuprofen and paracetamol help against headaches better than aspirin. Paracetamol has fewer side effects than ibuprofen.
Sleeping pills can lead to decreased breathing activity.
Antidepressants and drugs can lead to overconfidence and a reduced ability to take criticism.
The birth control pill increases the risk of thrombosis and embolism. A lot of drinking!
The relationships between medication intake and height are complicated and not fully understood. People who regularly take medication should consult a specialist beforehand. This is especially true for diabetics. The heart, circulatory, blood pressure, blood coagulation, asthma, and psychotropic drugs are also particularly affected.
In addition, it could perhaps be said that the topic is discussed very emotionally and controversially among mountaineers. Philosophical aspects (“by fair means”), half-knowledge, and know-it-all also play a role.
To acclimatize to great heights, you can of course simply go up high before the big tour in the Alps. For example, if you are planning a trip to Peru or the Himalayas, you could rent high-altitude alpine huts for a few days and do a few tours there.
However, the preparatory tour should then be as close as possible to the departure date, since the adjustments you have made will quickly wear off. But if you spend a week in the Alps at around 3000 m and fly to Lhasa or Cuzco, for example, shortly afterward, you have a measurable advantage.
Acclimatization via pressure chamber etc.
I have no personal experience with it. From the experiences with my guests, however, I suspect that the acclimatization attempts at home contribute very little to the real acclimatization on site. The truth is still out there! That means: Good planning of the tour and correct behavior on site are the decisive factors for a good altitude adjustment.
Faq high altitude medicine
Does it make sense to take your own medication (Diamox and Dexamethasone) with you, or do you have something like that with you on organized tours?
We don’t have any medication with us in the center … also because we as guides – unless we are also doctors – are strictly forbidden to give anything to the guests.
I usually have Diamox with me. I also take this as a prophylactic when I have difficulties with the altitude adjustment due to some illnesses (traveler’s diarrhea, colds, etc.). My family doctor thinks that you should take potassium in parallel with Diamox to prevent muscle problems.
It is up to you whether you want to do this as a guest.