Just a question

[peter k]

Is there a limit to how deep a human body can theoreticly go?I realise the logistics involved in going to extreme depths(I'll use the Marianas trench as a severe example), but is it technically and medically possible if gases are staged all the way down and back up for you?

It's just a question that's been annoying me and I can't see a reason why not!!!

Peter

[MATTBIN]

As I recall Peter nobody knows, there have been various max. depth theories ever since we (man/woman) started diving. All through this time max. depths have been quoted and broken so even if some scientist says its X now I would view that with suspicion. I suppose there must be one, not least the damage caused by the deco procedure even from a bounce dive to great depths as it would be extreme.

Matt

[Richie]

The serious commercial guys like Comex (French and barking) have consistantly pushed the physical and practical maximum depths and have a research facility in the S of F.
They really do push the limits and according to the website have managed 701m using mainly hydrogen as a dilutent. Je pense.

Deep enough for mere mortals IMHO, just cold, dark and a long way from home.  

Hmm, a 12000m dive, never considered trying that!
The deco involved would take months never mind the time to descend which would have to be slow enough to fully equalise all the tissues with the ambient pressure.
 The biggest problem would be the narcotic effects of the gases which at these depths would as far as I am aware ALL be narcotic to some extent or another.
 The medical side I am unsure on, it is possible the pressures would cause disruption to some of the chemical reactions making the body work but this is only a guess.
  The main technical problem though would be getting the gas at pressures that would be higher than the surrounding water and and work out a way of getting toffee like gas through a reg of some sort at roughly 18000lts a min

[Dominic]

Hmm… I'm pretty sure that the complex molecules in our bodies, such as globular proteins, would be deformed by pressure and can't equalize as they're too small for gas molecules to enter them.
On the other hand, anesthetics and pressure have complementary effects, so by doping someone to the gills, you may well overcome the effects of pressure, but I'm not sure that extends below the cellular level.
However, there is absolutely a depth limit for humans. Eventually, to get the depth you wanted, a planet would have such a high gravitational pull that you'd be squashed flat by gravity long before the water pressure got you.
Imagine strapping on a twinset to go diving in a black hole
I suspect you'd need liquid breathing systems before you could attempt such a dive. After all, at the very high pressures you'd experience, most gases would be liquid anyway. Plus, with a liquid breathing system, you don't have any deco obligations, as you can be supplied with the gas at surface partial pressures.

The molecules wouldn't really be compressed at all, water is a liquid and to all intents and purposes incompressible. I was thinking more along the line of the reactions being supressed to to pressure effects. This does have an effect of reactions and some will only take place within a narrow band of pressure/temp constraints.
 If you were to take your time you would end up still Peter shaped and whole on the bottom, you just may not be alive!
I don't understand what you mean by the gravitational pull, not sure what you mean if we are talking about earth
 gaseous oxygen is still around at the bottom of the ocean dissovled in the water, as far as I know it is more temp that causes it to liquify. liquid based breathing systems still wouldn't solve the narcocis effects though and you would still have deco obligations as you would have to breathe something as a dilutent and this would saturate your tissues big time

[steve-k]

question
i thaught your cells absorbed gasses at a given pressure untill they become fully sacturated
so at 20 m it might take 20 hours to become fully saturated and at 100m it might take only 2 hours?
in theory you would hit a depth where you will be fully saturated
my question is if you keep increasing your depth will you still absorbe nitogen/helium/o2, or do the cells hit a point where no more gasses can fit

[MATTBIN]

Steve
I read the cells/tissues get full regardless of depth its just time related, isnt that how sturation diving works? Once they are full it doesnt matter how long you stay down your deco requirements are the same.

Matt

[Mark Scott-Simons]

Restrictions due to problems proteins would have folding would probably limit the depths human can tolerate. Afterall certain deep sea fish die when brought to the surface cos there body chemistry goes askew due to the reduced pressure altering the shape of enzymes.

I read an article that suggested a limit of 1000m (IIRC)

Scotty

[Andy Phillips]

Yup, saturation is saturation, just lookat the cup of tea and sugar trick. Personally, I think the pressure down there would hurt, plus would the capacity of your lungs be sufficient to supply your body with O2, also, how would you mix a gas, you would have to have a very low initial percentage of O2 to end up with a low enough PPO2 to avoid a hit.

Just a few thoughts

Andrew