Altitude and acclimatization

Height, our bodies and some tricks to properly acclimate


Jordi Tosas, director of Off Trail Academy, on route to a virgin 7,000-meter peak of Langtang Himal, near the Tibetan border.
Jordi Tosas headed for a 7,000-meter peak of Langtang Himal, near the Tibetan border.

Any mountaineer that has ascended to extreme heights has always sought out physical training, but more particularly, to adjust the variables to be ready to carry out those activities. Among those variables, there is altitude, an invisible element, but which affects us to the point of being able to bring our dreams or even our life to an end. This is why it is paramount to fully understand altitude, its effects on our body and how we can get acclimated to it so we can achieve what we set out to do there, just where the land ends and the sky begins.

Why does altitude affect us?

Blanca Cotore on a new Sita Chuchura route, a barely attempted 6,000-meter mountain in Dhaulagiri Himal.
Blanca Cotore on a new Sita Chuchura route, a barely attempted 6,000-meter mountain.

The further we move in a vertical direction over the land, the more the air column shrinks. In other words, the thickness of the atmosphere gets smaller as we go higher and higher. This reduction results in a decrease in the partial pressure of the gases that it is composed of. One of these gases is oxygen, the atmospheric gas that allows us to live and make physical efforts. To give us a clear idea, at the peak of Mt Everest, a well-prepared mountaineer can only take advantage of 20% of oxygen compared to that at sea level. We can imagine then that making any kind of effort, including breathing, is much more difficult and taxing.

Basic physiology of altitude

When exposed to great altitudes (starting at 3,000 meters), we see that our breathing becomes faster and we hyperventilate more easily. Moreover, our heartbeat goes up, including while at rest. If we take our blood pressure, it will be higher than it would have otherwise been at a lower altitude. Without taking into consideration any medical analysis, what we experience on a personal level is very important, altitude always gives us information that we can observe with the naked eye, in real time and it will allow us to be alert in case of any pathology. In continuation, we will see what these symptoms are.

Nevertheless, if we look more deeply, in just a few hours, we will find a hormone called erythropoietin starting to demand the development of new red blood cells in order to increase hemoglobin levels and improve oxygen transport. This leads to a decrease in the effective volume of plasma. Somewhere around the second or third day, there is an increase in the blood pH due to exposure to hypoxia (lack of oxygen in the blood). Nearing the end of the first week, our muscle cells begin to reduce in size and increase in muscle capillary density.

This is the process of acclimatization on a physiological level, but, What happens if we don’t give our body time to complete each phase of it?

Altitude sickness

When we do not allow our body to adapt progressively to altitude, we are at fault for not letting the acclimatization to hypoxia develop optimally and therefore our health takes a turn for the worse. As I mentioned previously, height is tough but fair. And with that I mean to say that it will tell us in any given moment if we are, or aren’t, well-acclimated.

How can I understand the symptoms that warn me if something isn’t going quite in the right direction? Let’s get to know if we have altitude sickness or if we are suffering from acute mountain sickness (AMS).

Altitude sickness is the clinical picture of when we are getting acclimated. Each time we expose our bodies to a superior scale of altitude, we will notice how uneasy we are there as our body is clearly out of its comfort zone. The symptoms are very similar to fatigue, but we should always attribute them to altitude. When it comes to altitude sickness, for the most part, we will detect an increase in our breathing and heartbeat. It is also marked by having a more pronounced sense of fatigue than usual and especially by slight headaches. Furthermore, we won’t be as hungry as usual, and everything will take much more effort than usual. Do not try to do things quickly, since that will result in breathlessness. It is quite normal to get acclimated in the first couple of days and experience these, or other, symptoms. Once we get acclimated at that height, these symptoms will fade little by little. If they do not, however, they can become serious and get worse, moving on to the next clinical picture, acute mountain sickness.

AMS increases fatigue, even develops into something more severe and abnormal in light of our normal sensations. There will be a decreased urine output (the amount of urination we release), loss of appetite and a display of apathy towards others in the group. Headaches tend to be sharp and intense and generally do not respond to analgesics. Nighttime is afflicted with insomnia and a key aspect to watch out for is vomiting. This clinical picture should be given the utmost importance since this is the warning altitude gives us before becoming aggravated to the point which all too often is irreversible. There is medication to help soften these anomalies, but the best medicine for altitude sickness is GO BACK DOWN. Dropping your altitude and getting properly acclimated is the only medicine we should take before continuing the ascent.

A friend helping the sherpas during an exploration expedition by snowboard in a remote valley of Annapurna Himal.
A friend helping the sherpas during an expedition of a remote valley in Annapurna Himal.

If the AMS gets worse, it can easily lead to edemas. Cerebral and pulmonary edemas are the most well-known and it is noteworthy to add that if we reach this serious state, our lives will truly be at risk if we do not have professional medical help on hand as well as oxygen and the right pharmaceuticals.

The art of acclimatizing

In this subtle process, the first thing worth pointing out is the importance of drinking. Staying perfectly hydrated is absolutely essential in order to get properly acclimated. Let’s remember that the physiology of altitude is directly connected to the decrease in the volume of plasma. This affects us on so many levels that won’t be detailed here, but this increase in the blood density causes us to be colder, since it is not circulating properly in our small external capillaries. Drink, if possible, more than three liters of liquid a day. We cannot consider ourselves to be well-hydrated until our urine comes out colorless, and this is something we cannot forget. What’s more, it should be our constant goal.

Having said this, we will see how to plan our ascent towards the sky:

The traditional way is the rule of 500 meters. This means that we can go with a true 500 meters in elevation gain on a daily basis and sleep at a higher altitude without any risk to our health. The changes our body undergoes are not sharp enough for us to set off a severe clinical picture. This is quite manageable to do on multiple-leg trekking trips, but in other activities as is the case in mountaineering, it’s a bit trickier to pull off.

Another method we’d like to bring up here which can be useful if we have to climb well above the already acclimatized height, as in expeditions or trekkings that last several days and include stages where you have to cross a high mountain pass or hill. This does not present a problem if we later descend and sleep at a lower altitude. This would be the same altitude at which we are acclimated or, at most, 500 meters above that. For example, let’s say that we feel very well walking in Tibet at 4,000 meters above sea level. One day we have to cross a mountain pass at 5,200 meters. If we do this in one single day and go back down to sleep at 4,000 meters, or at 4,500 meters maximum, it does not present a danger to us. We can call this, “I go up high, but I sleep low.”

I would like to mention that we should not put our body under any intense strain during the first few days of the process. The pace should be adapted and gentle, avoiding carrying excessive weight. It is not good to overexert yourself during the period of acclimatization. In competitive sports, they do play with the combination of great heights and high intensity with plenty of rest and low altitude in a type of specific acclimatization in programs geared at high performance. Yet, that would open up a whole other article which does not concern us at the moment.

To sum up, I would only like to reiterate that altitude doesn’t lie to us. During the process of acclimatization we should be humble enough to listen to each and every symptom we feel. When in doubt, the cause should ALWAYS be attributed to the altitude and the best and only medicine is to DESCEND.