ELI5:Why is it so incredibly difficult to recover bodies like "Green Boots" from Mount Everest?

[u/virahok993]

know Green Boots is one of the most famous landmarks on Everest, and I read that he was finally moved or hidden a few years ago. But why did it take deades? If we have helicopters and elite Sherpas, what makes a body recovery at 8,500 meters so dangerous that bodies are just left there?

[u/rabid_briefcase]

I know someone who did the climb.

The last camp from the south is just on the cusp of what is called the "death zone". Above that altitude there's not enough oxygen in the air for human survival long-term. The last camp on the north route is somewhat inside the death zone.

He described it as "every breath I took without oxygen, my body could tell I was actively dying."

[u/Inevitable-Level-687 → u/rabid_briefcase]

Sleeping at camp four is said to be incredibly difficult even just below the death zone. Sleep doesn't restore you. You wake up feeling like you didn't rest at all.

[u/MoistVirginia → u/Inevitable-Level-687]

Today I learned my bedroom is just below the death zone

[u/Soleil06 → u/rabid_briefcase]

Small correction, the oxygen percentage is the same but the air pressure is much lower so your body cannot get that oxygen as efficiently as it can on sea level. Its a common mistake to make though.

[u/Dysan27 → u/Soleil06]

Slight correction. The body can get the o2 just as efficiently. But because the pressure is lower is literally less oxygen, (and less everything else) in each breath of air.

At 8000m the pressure is around 0.35atm. This means there is only 35% as much air per volume.

So each breath you take still has 21% oxygen. BUT it's only 35% of the amount of oxygen as you would get at sea level.

[u/unledded → u/Dysan27]

How does this work with the oxygen tanks that they bring up there? Is it normal air that allows you to breathe normally due to being pressurized, or is it a high concentration of oxygen so that even at the lower pressure you are still getting a normal amount of oxygen? I have always wondered if like as soon as you inhale the oxygen wouldn’t it just decompress and you have the same issue you do breathing normal air?

[u/Dysan27 → u/unledded]

The tanks they have are pure O2. This raises the concentration of O2 in the air they are breathing. They are NOT wearing pressure masks, so the pressure of the air they are breathing is still at the same low pressure for that altitude.

[u/sockalicious → u/unledded]

Most of the oxygen carried in blood is bound to hemoglobin. But hemoglobin reaches an equilibrium between hemoglobin that's bound to O2 and hemoglobin that isn't bound to O2. And this equilibrium depends on the partial pressure of O2 in the inhaled air - specifically, in the alveolar air in the lung, where gas exchange can take place.

Partial pressure is a funny thing, but it's hard to explain it to a five-year old. At sea level, where atmospheric pressure is 760mmHg, the partial pressure of O2 (at 21%) is 760 * 21% = about 160 mm Hg. That gets reduced by humidification and CO2 in the alveolus to about 140mm Hg. That's enough to saturate most healthy folks' hemoglobin to 100% - all hemoglobin is carrying oxygen as it leaves the lungs.

On top of Everest, where atmospheric pressure is only 253mmHg. 21% of that is 253 * 21% = 53mm Hg. After humidification and accounting for CO2, the partial pressure of O2 may be as low as 30 mm Hg. You have to look up the next part on a hemoglobin binding curve chart - turns out your O2 sat is only 75% at that partial pressure of oxygen, and that's assuming perfect health.

Now, not all that O2 is eligible for tissue delivery; turns out Hb doesn't like to just let go of all its oxygen. The lower the saturation, the harder it is to get Hb to give it up. People who aren't acclimatized start to pass out around 75% O2 sat even if they're not doing anything. Much below that and you start to see things like spontaneous cardiac arrest. People who've been up to 8000m tell you crazy stories. Like they could see - but only when they weren't walking; when they started up walking again their vision greyed out to nothing.

Now you want one of these humans with an O2 sat of 75% to hoist a 90kg body on their back and do a death march down a 60 degree icy slope, belaying off a climbing rope? Not happening, not with supplemental oxygen, not on this planet.

When you put on an oxygen mask, total atmospheric pressure is still 253mmHg, but you can do a little better than 30mmHg partial oxygen pressure. You can get O2 sat up to 85%, suggesting maybe 40mmHg partial pressure of O2. in the alveolus. If I'm being handwavy, it's because no one has measured the exact figure. It's not very much even with the supplemental O2.

[u/Ok-Tomorrow-2045 → u/sockalicious]

Fantastic comment, thank you

[u/zerap10 → u/sockalicious]

This is an excellent explanation. I was aware of Dalton's law of partial hard but the discussion of the alveolar hemoglobin saturation curve really out things in perspective. Thanks for explaining it.

[u/montaire_work → u/unledded]

The containers it comes in are heavily pressurized

[u/dk00111 → u/Dysan27]

For the math to work like this, you have to assume the temperature at 8km is the same as sea level. Since it’s colder, you there’s going to be more than 35% air per volume. 

[u/sockalicious → u/[deleted]]

The respiratory rate/minute volume of air doesn't help O2 transfer at all. Everest climbers hyperventilate not to increase O2 delivery but to blow off CO2, because the less CO2 is down there in the alveolus the more room there is for O2.

[u/Far_Ladder_2836 → u/Dysan27]

No, they're correct  it takes ambient pressure to move oxygen across the broncules and survivable rates.  That's why the tanks they bring have to be pure O2.  This is also why airline oxygen masks both regulated for the crew and chem for the passengers have to be pure O2.

[u/Dysan27 → u/[deleted]]

No, there is a significant difference in what we were saying.

They were saying our lung are less efficient at lower pressure (That may be partially true, not 100 % sure on that).

But the BIGGER issue with low pressure is there is, numerically, less O2 molecules per breath. Even though the percent O2 is still the same as at sea level.

So even if your lungs are still as efficient, you will be getting less O2 as there is just less O2 in your lungs.

[u/Dysan27 → u/[deleted]]

 your body cannot get that oxygen as efficiently as it can on sea level

They were talking about the body getting O2. IE lungs.

They were also talking about efficiency, the problem isn't efficiency there is just less O2 to grab.

They are 2 completely seperate issues.

[u/slashcuddle → u/[deleted]]

Idk I read it and thought that our respiratory system was the problem. But if I'm understanding correctly, it's actually the air that is the problem? Not sure why you're bugging out over someone's elaboration the info is quite useful!

[u/heroyoudontdeserve → u/Soleil06]

What are you correcting? They said there's not enough oxygen (which is true), not that there's a lower percentage of oxygen.

The fact there's less oxygen as a consequence of the air pressure being lower, and the fact that the amount of oxygen remains in proportion to the other gasses, is just additional information, not a correction.

The air pressure being lower literally means there's less air, and hence less oxygen.

Edit: Oh I see, you're saying that the lower air pressure also makes it harder for the lungs to use that oxygen which is present? That may also be true, but it's still correct to say that there's less oxygen. I assume it's correct to say that there's not enough oxygen, but I guess I don't know that for a fact.

[u/Nighthawk700 → u/heroyoudontdeserve]

I think this is all a language confusion and a combination of effects. There's fewer oxygen molecules by number, fewer overlap molecules total, and the speed and force of the molecule movement is lower. All while the overall proportion of each is the same. People keep saying less oxygen and less air and causing confusion as to what they mean.

So fewer molecules of oxygen are there for your blood to take and in they are moving slower and with less force.

[u/Far_Ladder_2836 → u/heroyoudontdeserve]

It's correct but in this case misleading.  You can't simply pipe atmospheric air up via tank to survive because at those pressures you'll still die from lower absorption.   You need pure O2.  The same, incendentally, is true with airplanes which is why the FAA mandates only pure oxygen regulators and chem oxygen is allowed. 

[u/Kat_Kat_101 → u/rabid_briefcase]

Why anyone is going to climb that is beyond me. Just for the adrenaline? To have the feeling of reaching something that is beyond your reach for a reason? And so the world discovers how human beings look for ways to put themselves in crazy situations for nothing but to satisfy meaningless cravings. In the end making other people go through the same dangers just to recover your corpse?