Human Crush Depth

[Rich Keller]

There is a depth that bone either dissolves or is crushed, I have heard it refereed to as the "snow line" but I believe that it is shallower then DocVikingo says. The only bone known to survive below that depth are certain sharks teeth and the inner ear bone of some whales. I think you need to look at deep ocean research projects to find this answer.

 

[DocVikingo]

Everybody is saying that liquids (esp. water but not limited to?) are "incompressible"... ahem.. really? That doesn't make a lot of sense to me just in and of itself.. would someone care to explain for me?

Hey Inochi,

You've asked enough questions that multiple responders can play. I'll take the opening kick off.

Water is not perfectly incompressible, but like most liquids it has a very, very limited ability to be compressed. The reason for this is that its molecules are so densely packed that they can't be forced much closer together--the outer electrons of the atoms will repel one another.

Here’s a table showing the compressibility at room temperature of a number of liquids -> http://www.engineering.uiowa.edu/~cfd/pdfs/tables/1-42B.pdf

As you can see, water’s is pretty darn miniscule.

Regards,

DocVikingo

 

[Inochi_Fumetsu]

Hey Inochi,

You've asked enough questions that multiple responders can play. I'll take the opening kick off.

Water is not perfectly incompressible, but like most liquids it has a very, very limited ability to be compressed. The reason for this is that its molecules are so densely packed that they can't be forced much closer together--the outer electrons of the atoms will repel one another.

Here’s a table showing the compressibility at room temperature of a number of liquids -> http://www.engineering.uiowa.edu/~cfd/pdfs/tables/1-42B.pdf

As you can see, water’s is pretty darn miniscule.

Regards,

DocVikingo

Yeah thanks Doc . That's basically what I thought - though it's a lot less compressible than I had imagined (1% density increase at 150 bar from what I understand).

I'm assuming you're referring to the hydrogen bonding that occurs in water? This would potentially make it less compressible than other liquids in my mind.

And yes, by all means.. anyone and everyone take a stab - answer anything you like! All answers greatly appreciated!

PS - Mercury I understand obviously; but Glycerol is actually less compressible than water?? That's interesting...

PPS - Got any ideas as to what the "crush depth" I'm looking for might be Doc?

---------- Post added March 10th, 2014 at 04:41 PM ----------

There is a depth that bone either dissolves or is crushed, I have heard it refereed to as the "snow line" but I believe that it is shallower then DocVikingo says. The only bone known to survive below that depth are certain sharks teeth and the inner ear bone of some whales. I think you need to look at deep ocean research projects to find this answer.

That's very interesting.. thank you

EDIT - I did some quick research on it and I don't think the CCD (what you were referring to as the "snow line") would really affect the max depth at which humans could dive - but it was an interesting read - thank you for the input .

 

[Inochi_Fumetsu]

No? No one has any idea what the limits are on the human body in regard to the maximum depth / pressure we can withstand?

 

[Duke Dive Medicine]

The compressibility of liquid comes into play with deep saturation dives. Liquids are sometimes referred to as "incompressible" but as DocV pointed out, they actually are not. High pressure nervous system (HPNS) is thought to be related to a reduction in the size of the synapses related to compression. In 1981 we set the record for the deepest manned chamber dive at 2250 fsw. Comex broke it by 50 feet in 1992 but the diver only spent two hours at 2300 fsw. Nobody has pushed it beyond that because the effects of HPNS become unmanageable, at least by present day science and technology.

Best regards,
DDM

 

[Inochi_Fumetsu]

The compressibility of liquid comes into play with deep saturation dives. Liquids are sometimes referred to as "incompressible" but as DocV pointed out, they actually are not. High pressure nervous system (HPNS) is thought to be related to a reduction in the size of the synapses related to compression. In 1981 we set the record for the deepest manned chamber dive at 2250 fsw. Comex broke it by 50 feet in 1992 but the diver only spent two hours at 2300 fsw. Nobody has pushed it beyond that because the effects of HPNS become unmanageable, at least by present day science and technology.

Best regards,
DDM

That's great that sounds like exactly what I was looking for, thank you .

So quick couple questions (if you don't mind):

1) You said it was a "chamber dive". I'm assuming that means a person in some sort of steel capsule? Could be described metaphorically as a being inside a tiny submarine no?
- was the air pressure inside the capsule equal to the water outside the capsule? Do you know?
- would we have been able to reach that depth without the capsule? (Just the diver's body in the water?)

2) You mentioned that the effects of HPNS become unmanageable beyond 2300fsw..
- firstly, "fsw"? (sorry I'm not a diver myself)
- second, what are the effects of HPNS to which you are referring? I'm guessing the obvious thinking is that you'd probably die if you went deeper than 2300fsw due to the effects of HPNS - how would that happen? Would you speculate for me what the effects would be and how would you die?
(I know, seems a pretty morbid question but I'm curious exactly what our limits are and why )

Thanks so much for your answer, I hope you don't mind elaborating a little for me.. I'm awfully curious in general (sorry).

Regards,
IF

 

[emoreira]

That's great that sounds like exactly what I was looking for, thank you .

So quick couple questions (if you don't mind):

1) You said it was a "chamber dive". I'm assuming that means a person in some sort of steel capsule? Could be described metaphorically as a being inside a tiny submarine no?
- was the air pressure inside the capsule equal to the water outside the capsule? Do you know?
- would we have been able to reach that depth without the capsule? (Just the diver's body in the water?)

2) You mentioned that the effects of HPNS become unmanageable beyond 2300fsw..
- firstly, "fsw"? (sorry I'm not a diver myself)
- second, what are the effects of HPNS to which you are referring? I'm guessing the obvious thinking is that you'd probably die if you went deeper than 2300fsw due to the effects of HPNS - how would that happen? Would you speculate for me what the effects would be and how would you die?
(I know, seems a pretty morbid question but I'm curious exactly what our limits are and why )

Thanks so much for your answer, I hope you don't mind elaborating a little for me.. I'm awfully curious in general (sorry).

Regards,
IF

1) Chamber dive refers to a dry dive, where the diver is introduced in a pressurized chamber. The interior pressure of the chamber is increased in the same way the water column would increase pressure.
The capsule (chamber) is on land, at surface level. No need to submerge it.
The interior pressure inside a submarine is 1 atmosphere. There is no need to increase the interior pressure of the living quarters.
I do not recall any diver diving so deep in water. You can google several depth records for different types of dives, I mean, freediving, diving in scuba, with air, with gas mixtures, sat diving, Atmospheric diving, etc.

2) fsw stands for "feet of salt water" 2300 fsw corresponds to a depth of 701 meters and an absolute pressure of 71 atmospheres.
HPNS stands for High Pressure Nervous Syndrome, which causes trembling and delayed reactions.

 

[mike.chuanshi]

What about the "crushing" of the middle ear, paranasal sinuses, teeth, or temporal lobe of the brain? As these are all susceptible to barotrauma, it seems these areas would be at higher risk of damage and that such damage may likely lead to other life-threatening injuries.

Back in 2005 there was an article published in AJNR (American Journal of Neuroradiology) that described how they used CT imaging on a scuba diver complaining of headaches to identify "blood and gas...within the epidural space of the middle fossa and over the petrous bone, as well as hemorrhage within the adjacent temporal lobe."

Doesn't sound like much fun...

 

[ScienceDiscoverer]

So I researched this question for a very long time... And it seems there is very little informations and interest in it, which is strange, as this is very important topic!

Now, in this video:

Author gives very specific figure of 1 km (which I doubt very much, as he didn't provide any sources on this figure). But the reason for actual crush depth is very interesting and I think it is the real limiting factor for humans.

So, reason is as follows. At very high pressures, as water IS compressible, just much less than air, our own cells membranes will fail us. Because the ambient pressure will be so high, proteins in cell membranes would be squished so hard, they would fail to pass nutrients/oxygen into the cell. This will result in cell death, and first one to go would be, probably, brain cells... Good example of this is Blob fish, you know, one from meme of "ugliest animal". It has very soft, jelly like cell membranes, optimised for 1.6 km depths it lives in. Under such high pressure, it's membranes are as strong as our own on the surface. But bring the poor creature to the sea level, and it will turn into a blob.

Now, the only important question now is to figure out exact depth it would happen to human... I think video author just chose it randomly without much thought. Because many deep diving whales dive to 2 km depths and Cuvier's beaked whale can dive up to 3 km depth. And this whales don't turn into jelly when they surface. So when guessing human crush depth, we should at least take 3 km as maximum. Again, I don't know if Cuvier's whale reached his cell membrane limit at 3 km or there is just no food for him deeper. But that's the most accurate figure we have, for now...

To determine this with certainty, however, somebody need to do a set of simple experiments. In fact, it's so simple, I'm puzzled how nobody ever done this before...

The equipment is pressure chamber capable of simulating water pressure of up to 11 km depth. With this, its just the matter of placing some cells inside this chamber and rise pressure gradually, then monitor the survival rates. First some bacteria can be tested, then human cells like liver cells, for example, or maybe even some neurons. If this tests would be successful, then lab rat test with liquid breathing and CO2 scrubbing can be made.

But for now, I shell assume human crush depth to be 3 km.