Acclimatizing for climbing above 8,000 m: Mt. Manaslu

Acclimatization is the process of “training” your body to function as much as possible within normal values, with the intake of less and less oxygen. As the air pressure decreases with the altitude, the amount of oxygen in the air is more spread out, and therefore the body needs to adjust to this. The process happens by gradually ascending various levels of altitude, while also spending time at each level in order to acclimatize.

In this article we’ll explain more about the acclimatization process and specifically how this goes in case of Mt. Manaslu, as Radu went through the process of documenting what’s next for him. He is currently climbing the mountain, and is going through the acclimatization cycle. Once he is back, we will write an update on the actual data Radu monitored during the expedition (level of oxygen in his body correlated with altitude).

Some facts: air density, oxygen and altitude

There is a close relation between the air density, level of oxygen and altitude, and this relation is basically the starting point of the discussion around acclimatization.

At sea level, the air is composed of 21% oxygen, and a barometric pressure of 760 mmHg. At 3,600 m though, the air is still composed of 21% oxygen, but the pressure is much lower, roughly 480 mmHg. This means that the air density greatly decreases, as the air (and the oxygen as well) is spread out more because of the lower pressure. At extreme altitude, the barometric pressure goes as down as 250 mmHg above 8,000 m, so basically the amount of air available reduces to 1/3 compared to the sea level.

The lowest tolerable barometric air pressure is of approx. 350 mmHg, recorded at 6,000 m. Going above that altitude comes with significant risks and body damages directly proportional with the amount of time spent there.

 SaO2: blood oxygen saturation

The way a human body adjusts to the decreased oxygen level is by breathing faster and deeper, even when resting, so that the needed oxygen is still taken in the bloodstream (known as blood oxygen saturation – SaO2).

As shown in the chart below, the SaO2 at 6,000 m (where the air pressure is still tolerable by a human being) is down by 20%, while at 8,000 m it goes down by 40%.

There are three main levels of altitude. “High altitude” refers to 2,500 – 3,500 m, “very high altitude” is up to 5,500 m, while the “extreme altitude” above 5,500 m is where the body is really going under too much damage. No one can predict how anyone will react to the different altitude levels as no previous research could prove any correlation between age, gender, fitness level, etc. and altitude.

How to acclimatize

The correct way to acclimatize is to walk up on your own feet (no chopper or car), taking it slowly, gaining between 300 and 500 m altitude level a day, and resting as low as possible or spending some time to adjust at the new altitude. You also need to stay well hydrated (water contributes to bringing oxygen into your body) and avoid overdoing yourself physically.

The point when a person starts feeling the symptoms of altitude sickness is called the acclimatization line. Once you reach that acclimatization line, you need to stop and spend a day or two there in order for your body to get used to the height and oxygen level. And only then continue to climb.

Acclimatizing for Manaslu’s summit push

To make sure Radu and his team are well acclimatized for the summit push at the end of the month, they’ve been careful about taking each step properly.

The first acclimatizing day started in Tilije, from 2,700 m, going up to the Larkye La pass at 5,212 m, and the finishing the day and sleeping at Samagaon at 3,390 m. This was an acclimatization line, as all of them experienced different altitude sickness symptoms such as headaches, diarrhea or dizziness. They’ve spent a few days there to get used to the altitude and overcome the altitude sickness symptoms.

From Samagaon they went up to Manaslu’s base camp at 4,895 m, to a new acclimatization line, where they’ve also spent a few days to adjust. As usually things don’t go as planned, they’ve experienced weather conditions that challenged them beyond altitude sickness (such as low morale or catching a cold), but they’ve kept as much as possible to the schedule.

The next step in the acclimatization cycle was going up to Camp 1, at 5,700 m, and returning in the same day at base camp and resting there for another few days.

Now, the teams have returned from their last acclimatization trip, which lasted for a few days. They went up to Camp 1 at 5,800 m and slept there for the night. The next day, they went even further, to Camp 2, at 6,400 m, and slept there. Then the plan was to continue up to Camp 3 at 6,800 m and go down to sleep in one of the lower camps. Because of the high avalanche risks, they only climbed up to 6,700 m and then slept down in Camp 2, then returned to Base Camp the following day.

This being accomplished, Radu and his team is now ready for the summit push. They’ll stay in the Base Camp waiting for the good weather window and then start climbing to Manaslu’s top at 8,163 m. Some climbers use supplemental oxygen above 7,500 m where the air pressure makes breathing and moving extremely difficult, but Radu’s intention is to do a “clean” climbing, hoping his body and genetics will cope with the extreme altitude. Fingers crossed for this experience to be a successful one in every way!

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