Physical pressure

Mentallic

What kind of air or water pressures can a human withstand? Approximately when does it become difficult to breathe and eventually impossible to breathe? After this point, would the person being succumb to these extremes be able to hold air in their lungs? What would be the first factor to cause death?

berkeman

Keep in mind that when diving underwater with a scuba tank, you are breathing pressurized air. You can't breathe surface-pressure air more than a few feet down.

Andy Resnick

Echoing what berkeman said, your lungs can only pull a [tex]\Delta P[/tex] of about 20-30 inH20. But, if you had a pressure-regulated breathing device (SCUBA, etc), your body can physically withstand quite high and low hydrostatic pressures.

Pythagorean

In the movie Abyss, they had to use an embryonic style delivery for oxygen (the synthesized embryonic fluid was 'charged' with a finite amount of oxygen and then the diver had to inhale the fluid into their lungs.)

Of course, it's a movie, but I think the rationale is that the oxygen tanks themselves couldn't withstand the pressure at the depths they were going...

But if that's the case, then is there a depth at which the pressure is so much that we can't expand our lungs to inhale, even with SCUBA equipment? I mean if it will crush a metal cylinder of oxygen, what would it do to the ribcage and/or internal organs?