Human Crush Depth

[RikRaeder]

Just wondering what the theoretical crush depth for a human would be. I'm not planning any record breaking dives, I'm not up to anything nefarious, and I understand that we're 70% or so water which is for all intents and purposes incompressable. What about the other 30%? There must be some depth at which the human body would succumb. Any of you diving mathamagicians have some arcane way to figure this one out (if you haven't already)? Just for fun? Sorry if this has been asked before (tried a search) or is in the wrong forum.

 

[cutlass]

The trick to the problem is that the remaining 30% is made up of non-water non-gaseous minerals and tissues which are also practically incompressible; e.g. salts, proteins, fats/lipids, etc., etc.

"Crushing" implies the collapse of a sealed rigid gas-filled structure and I'm not aware of any in the human body. If anything, hollow tissues will collapse to their elastic limit and then fluids will infiltrate any residual spaces. For example, leakage of fluids into the lungs (pulmonary edema) is a particular hazard of very deep breathhold diving. Basically, capillary disruption follows from chest/diaphragm compression limits being reached and lung tissue no longer able to support any remaining miniscule air spaces. Surprisingly, this effect has also been noted in (endurance) surface swimming, called swimming-induced pulmonary edema (SIPE); for example, here.

 

[DocVikingo]

Hi RikRaeder,

Bone crushes at about 24,600 lbs per sq inch. 33 ft=1 atmosphere and one atmosphere=14.6 psi. Thus, somewhere about 22 miles down the bones might be expected to crush. For the purpose theorizing, this leaves the likely dissolution of bone (e.g., calcium remaining in a solid state) at such depths.

Of course on standard SCUBA you'd expire of other causes (e.g., gas toxicity related to Dalton's Law of partial pressures) long before even remotely approaching that depth. Now, if you had an equal-pressure suit that would balance inside and outside pressures, crushing (and gas toxicity) wouldn't be a problem, but obviously no such device exists that can make it anywhere near that depth.

Since we're having theoretical fun, what would be a SCUBA diver's deco obligation if s/he could dive to 117,766 ft on air? ; )

Regards,

DocVikingo

 

[fire_diver]

Since we're having theoretical fun, what would be a SCUBA diver's deco obligation if s/he could dive to 117,766 ft on air? ; )

Regards,

DocVikingo

According to V-Planner....

36,264 minutes (604.4 hours or 25.18 days) This was assuming a 30ft/min decent rate.

Also,

Off gassing starts at 76729.4ft

OTU's this dive: 4026684
CNS Total: 3069601.9%

16035538.9 cu ft Air
16035538.9 cu ft TOTAL

 

[DocVikingo]

Bravo ; )

DocV

 

[Inochi_Fumetsu]

Hi RikRaeder,

Bone crushes at about 24,600 lbs per sq inch. 33 ft=1 atmosphere and one atmosphere=14.6 psi. Thus, somewhere about 22 miles down the bones might be expected to crush. For the purpose theorizing, this leaves the likely dissolution of bone (e.g., calcium remaining in a solid state) at such depths.

Of course on standard SCUBA you'd expire of other causes (e.g., gas toxicity related to Dalton's Law of partial pressures) long before even remotely approaching that depth. Now, if you had an equal-pressure suit that would balance inside and outside pressures, crushing (and gas toxicity) wouldn't be a problem, but obviously no such device exists that can make it anywhere near that depth.

Since we're having theoretical fun, what would be a SCUBA diver's deco obligation if s/he could dive to 117,766 ft on air? ; )

Regards,

DocVikingo

Ok, so I realise this is a 13 year old thread.. but I was looking around online for the answer to OP's question here and I found this thread and you guys seem to be saying the same thing as virtually everyone else. I AM CONFUSED lol..

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?

Secondly, while I realise that there are a MULTITUDE of other factors surrounding a realistically achievable max depth (for example, inert gas narcosis, heliox tremors, oxygen toxicity, air reserve consumption rates, ambient water temperature?, and minimum fluid flow rate using mechanical assisted ventilation for purposes of blood CO2 diffusion and maintenance for, at present theoretical, liquid ventilation systems using a perfluorocarbon liquid as the oxygen-carrying medium *gasps for air* ETC.!).. While I realise that all of those factors are perfectly valid when discussing a realistically achievable max depth - what I'm looking for is an anatomically / biologically derived restriction / upper limit (if there is one?)

For example, I see our bones will "crush" at 22 miles depth (ok that's ridiculous no one's ever diving that deep lol) - but I would have THOUGHT, that our vital organs or vital functions would become screwed up to the point of malfunction enough to result in certain death LOOONGGG before we hit that depth. And I'm talking physically (resulting from our natural anatomical/biological design).

So for the purposes of theoretical argument, assume that breathing was never going to be an issue for us no matter how deep we went (either we're using some sort of futuristic liquid-ventilator or we've come up with the perfect gas mix that works at any depth with no ill effects etc. etc.). Is there a depth at which the structural integrity of our rib cage would fail (breaking every rib in our chest and collapsing our lungs so we physically CAN'T breathe?) Or is there a depth at which our small blood vessels and capillaries would burst? Resulting in hypoxia or pulmonary embolism or pulmonary edema or exsanguination or something else? Is there a depth at which our skulls would implode? (the bone itself would remain intact.. not flattened into a calcium "paste" necessarily (requiring a depth of 22 miles apparently)) - but intact, it just couldn't structurally hold the pressure anymore and it broke? A depth at which our eyeballs would pop out of our heads? Or a depth at which the pressure is too great for our heart to be able to move blood through our veins and arteries anymore? Like the blood vessels had been clamped shut? Or where we'd simply lose consciousness for a reason along these lines and (obviously) die if we lost consciousness or went blind or something alone that far underwater? Perhaps at a certain depth the pressure would actually screw up cellular passive or active osmotic processes (messing up our metabolism or various biochemical processes at the cellular level (and almost certainly resulting in death)? I'm looking for a realistic physical limitation to the functioning of our bodies as it relates to the ambient pressure we're experiencing - regardless of any other factors.

Freezing to death could count but if you thought that would happen first then I'd kindly ask that you list the depth at which you believe we would logistically freeze to death and then list the first subsequent depth at which you believe our body would encounter a structural physical limitation to the biological / anatomical functioning of our bodies as a result of ambient pressure --> fail --> and result in death. I would please like to know what you believe that physical limitation would be - what would happen to us? start to finish, how would we die? and at what depth would this occur??

Sorry for the novel I just can't find an answer to this (even a theoretical one) anywhere on the internet!
Looking forward to any and all answers I receive with great anticipation!

Thanks so much in advance

 

[DandyDon]

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?

Correct. If liquids could be compressed, brake fluid and hydraulic lines would not work well.

On a home well pressure tank, you have to have air above the water so it can be compressed to push the water thru the lines. Most today have air bladders but I've had some that did not, and the air would dissolve in the water over time - needing to be replaced.

 

[BRT]

And if water compressed each 10 meters down would weigh more than the 10 meters above it and atmospheres at depth would get hard to calculate.

 

[hroark2112]

Ok, so I realise this is a 13 year old thread.. but I was looking around online for the answer to OP's question here and I found this thread and you guys seem to be saying the same thing as virtually everyone else. I AM CONFUSED lol..

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?

Thread is 3 years, not 13 years old.

Check out this article Water Compressibility, USGS Water Science School

Hope this helps!

 

[Inochi_Fumetsu]

And if water compressed each 10 meters down would weigh more than the 10 meters above it and atmospheres at depth would get hard to calculate.

Yes. This is exactly what I expected. The same way air compresses as you go down.. Although granted it would be a much less noticeable effect at first, given the massive difference in initial density of water vs. that of air - however I would expect that once you got down far enough it would become quite noticeable and the rate at which pressure increased (measured in bars) would become geometric (where it is still technically geometric at shallow depths, but the acceleration on the rate at which pressure is increasing due to initial pressure would be so small it would be almost negligible and therefore could be treated as a linear relationship for quick calculations).

However.. I'm just about to read the article hroark2112 posted so maybe that'll explain it better to me

EDIT: Just read that article; I was right, but at a depth of 1 mile (150 bar), water density has increased only 1%. Therefore you need to go very deep before estimating the water pressure at depth using a linear realtionship would become inaccurate.

Thread is 3 years, not 13 years old.

lol... oops.. my bad. I read the initial post as 2001 not 2010 for some reason


....

So does anyone have any ideas as to the "crush depth" to which I was referring in the rest of my (ridiculously long) question??