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

LennoxLewis

.....assuming very slow adaptation is possible. How low can one go?

And something else: if you're at very low pressure, water or blood would boil at RT (pressure is lower than the vapor pressure of water). Would this mean a relatively innocent cut wound would make you lose a lot of blood?

The person is allowed to use breathing equipment, like a diver, but not a pressure-suit or anything similar.

mgb_phys

Long term anything below about 0.15atm pure O2 means you aren't going to live

Short term nothing is actually going to kill you, except by removing all the O2 from your system

Andy Resnick

People have been exposed to vacuum in explosive decompression tests:

http://www.geoffreylandis.com/vacuum.html (about 1/2 way down).

There's a video I've seen of the 1966 test, it's actually kind of boring to watch.

Chronically, people can live up to about 15,000 feet altitude:

http://news.nationalgeographic.com/n...evolution.html

And their bodies have undergone significant adaptation. The article states that death from hypoxia occurs around 25,000 feet in altitude, corresponding to about 282 mmHg (37.6 kPa)- atmospheric pressure is 101 kPa and 760 mmHg. Assuming 20% of the air is O2, the partial pressure at 15,000 feet agrees well with mgb_phys: those folks are living right at the edge of existence.

LennoxLewis

Just to clarify, I'm not talking about the threshold of being able to draw too little oxygen. I'll edit the first post.

Let's say the person is allowed to use breathing equipment. But no space suit or anything similar that manually retains a high pressure.

LennoxLewis

Thanks a lot for that link!

Those kind of sites are what I love about the Internet. Unique knowledge being shared for non-commercial reasons. Unfortunately, these kind of pages are more and more hard to find as search machines first list E-bay and all kind of commercially related sites. Back to the topic now...

mgb_phys

Lowest pressure is about 0.15atm with breathing apparatus, that's the lowest partial pressure of O2 you need and you can't breathe with breathing apparatus if the outside pressure is less

LennoxLewis

What is the reason you can't breath with apparatus when the outside pressure is less than 0.15atm? And would that (hypoxia) be the cause of death in such a situation, or are do other lethal effects take place?

nucleus

By 1996 more than 60 men and women had reached the top of Mount Everest without oxygen.
http://www.pbs.org/wgbh/nova/everest...firstwoo2.html
The first was Reinhold Messner and Peter Habeler. Here is Messner’s account of the accent:
http://www.pbs.org/wgbh/nova/everest...firstwoo2.html
There is more than one form of Hypoxia:
http://www.faa.gov/pilots/training/a...oxia/index.cfm.

DHF

.15 is the triple point of O2. I am not sure what the exact effect a zero pressure environment would have on O2 but if you are looking at such low pressures you are facing a vacuum, and in a vacuum you would be exposed to extremely cold temperatures its possible that without a pressurized environment the 02 would convert to ice at those temperatures .

However at such temperatures breathing would be the least of your problems. with nothing more then a breathing mask on, exposed to a vacuum you would freeze to death very quickly.

Don

snipertje

No you don't freeze to death, because despite the low temperature (i'm not even sure if it has to be cold in a near vacuum) there is no matter to exchange heat with, so your body temperature will stay the same.

A.T.

You loose heat trough radiation.

russ_watters

...but the reason you can't breathe is because your lungs would burst if the pressure differential is too high, even if you were strong enough to exhale.

snipertje

You generate heat inside your body as well...

Lsos

I could see that in space, but on the earth? With your surroundings being similar temperature?

Infinitum

You'd still radiate heat. You are, right now. The matter surrounding you radiates heat too, and there is a balance of the heat absorbed and radiated by you, and this forms a dynamic equilibrium. When you're in vacuum, there is no 'matter' to radiate heat so that you can absorb it. Your heat is just radiated out, without you getting anything back.

Edit : Also, vacuum has no temperature, since there are no molecules to vibrate.

Lsos

Perhaps you mean when you're in space? Just because you're in a vacuum doesn't mean there's no matter around you. Maybe not in direct contact with you, but surely the thick stainless steel walls which have to fully surround you (if you hope to create a vacuum on earth) count as matter, and they radiate just as much heat back to you as you radiate to them?

Infinitum

Given a long enough interval for the attainment of equilibrium, yes, they would.