What is the minimum pressure the human body can handle? ..

TheFerruccio

This intrigued me and was running through my head. Alright: Suppose you didn't receive your oxygen through your lungs, but your blood was being circulated through a separate device, and you had no need to breathe (all crazy hypothetical stuff). Can the body survive just fine in a vacuum if given sufficient time to equalize? Is there a minimum pressure after which the human body cannot equalize anymore?

Meaning: How much does pressure matter to the human body outside blood oxygenation needs?

cytochrome

I have two concerns/hypotheses about this

First

Even if you didn't have to breathe and you could cover up your nose and mouth, think about all the openings into your body (ears, digestive tracts, eyes, etc... even your pores). I think that contained pressure in the body would strive to get into an equilibrium with the surrounding vacuum and the gasses/fluids in your body would be forced out.

I think it would be similar to a fish that is adapted to pressure in the deepest trenches of the ocean. These creatures (depending on which) sometimes ooze out fluids and gasses when brought to the surface because they are used to such high pressure.

There's a reason that vacuum chambers are sealed so tightly (to form a barrier that prevents equilibrium with the surroundings from happening). I doubt that our mere skin is a sufficient barrier.

Second

I think someone already mentioned this, but wouldn't the water and other liquids in our skin and our eyes evaporate? As the pressure decreases the boiling point should decrease as well.




EDIT: Back to your meaning - I don't think it matters too much when breathing isn't an issue because naturally, we can't even reach pressures that would be considered close to a vacuum on earth. Ergo, we are not meant to float around in space so I think that our bodies (when breathing is not considered) may be well adapted for low pressures.

TheFerruccio

Regarding the first point: Humans are frequently subjected to 8 bars of pressure in hyperbaric medicine, which means that, over a period of time, the human body can go from a pressure of 8 bars to 1 bar, a difference of 7 atmospheres. This happens very slowly. If this were to happen quickly, terrible things happen. The Byford Dolphin incident had divers living in a condition of 9 atmospheres just fine. The problem arose when there was an explosive decompression, which basically liquefied some of the bodies and rapidly filled the blood of the others with fat.

But, anyway, humans can definitely handle pressure changes of many atmospheres, provided they are given enough time for the pressure in various pressure vessels in their bodies to equalize. Wouldn't a difference of one atmosphere (1 atm -> 0 atm) be even less harsh, if given the same amount of time to slowly depressurize? It's been stated here that the min. sustainable pressure is 0.15 atmospheres of pure oxygen, but this is with the breathing requirement in place. But, at that point, they have already depressurized 85% towards a vacuum.

I envision being completely open, not worried about covering up any pores. Let all the air from all the pores evacuate themselves wherever possible. Whatever it is, it will *certainly* be much less of a pressure change to an animal than bringing those deep sea creatures up to the surface. Physically, the pressure change from 1 atm to a vacuum is ~1/500th that of from deep sea to 1 atm.


Your second point is what I was thinking as well. I think the biggest challenge we'd face if "breathing" was taken care of in a vacuum would be drying out. The fluids in our eyes, nasal cavities, ears, etc, probably have some kind of water content which would want to become gaseous when subjected to a vacuum. The rest of our body is actually pretty good at holding in the water against the pressure. Our eyelids would drag across our eyes, the skin in our mouths would be as if we'd just woken up after mouth breathing all night. I can't imagine what a 100% dry nasal cavity would feel like...

So, maybe the biggest challenge to being in a vacuum = dessication?

cytochrome

I agree. Perhaps we could be hooked up to some sort of intravenous tube to slowly supply us with water and moisture at a rate that would be slow enough to prevent any sort of rapid vaporizing reaction.

nitsuj

Sherpas are people too, it's more than 60.

While it's a very impressive feat for a "westerner's" build (6'3" 220lbs), a 5'3" 140lbs Sherpa won't find it as difficult to do work.

Nydoc

I think no matter how your blood gets oxygen or long you take to acclimate it's not a good idea to go beyond the Armstrong limit. If your respitory tract is exposed to vacuum then your saliva will boil and the alveoli in your lungs will boil. You might also experience bodily swelling. In 1960, Joseph Kittenger skydived from a balloon at 102,800 feet (0.009 atmospheres) after ascending for an hour and a half. During the ascent, the pressurization for his right glove malfunctioned and his hand swelled to twice it's normal size. If your whole body were to remain in a vacuum then you would likely end up with tissue damage or at the very least be unable to see due to your face being swollen. Incontinence might also be a problem.

This being said, I find it fascinating that some populations have evolved to live in low pressure environments.