Fish and decompression

[blacknet]

Hello,

Diverl, they have what is known as the mammilian effect. They shut down the vessels/capilaries to non-critical sections of the body, thus hindering gas uptake in that region and saving vital o2 to critical regions like the brain, heart and the like.

Ed

 

[Liquid]

Blacknet- I am not sure if the effect works the same for marine mammals as it works for us. After all- they spend their entire life in the water,so how can they swim with less blood to ther legs/fins?
Same goes for sea turtels. They dont have any mammal effect, not being mammal and all, yet still, they do fin in the sea.

 

[blacknet]

Hello,

well another thing to is they do NOT breath compressed gas while submerged.

Ed

 

[rcohn]

We've covered this before. See:
http://www.scubaboard.com/showthread.php?threadid=1734

Ralph

 

[The Chairman]

Hey all,

Actually the law Dr Deco referred to is "Henry's Law". Not very well known, for sure and it states...

"The amount of any given gas that will dissolve in a liquid at a given temperature is a function of the partial pressure of that gas in contact with the liquid..."

As to how whales etc, manage that deep diving gig, you have to remember their time going down is probably roughly equivalent to their time going up. Ergo, most, but probably not all of their deco occurs naturally. I also wonder if they have a way of shielding their lungs from the ambient pressure of the ocean. Rib cages, blubber and such could keep the actual pressure in the lungs to tolerable levels. Ah, but this is mere conjecture on my part.

Check out the "Fizzyology" section on the IANTD website for a wonderful analysis of partial pressures and diving physiology... it's where my quote came from!

http://www.iantd.com/rebreather/phys.html

Don't give in to peer or ambient pressure ya'll...

:tease:

 

[Liquid]

Netdoc- I belive that in whales there is no deco risk becouse of the total amount of nitrogen dissolved in their tissue. It's simply not enough to couse DCS. They still have the amount of O2 they got from above, and that's enough to sustain their systems. Comercial divers, for example, when diving deep use gas mixes with 4% O2, even less, so all in all they get slightly more oxigen than on the surface.

As for dealing with the ambient pressure: If humans can so can they. Humans have riched over 150 meters deep (about 650 feet) in free dives. what happens is that blood flows to the capaleria surounding the lungs, and feels the space of the compressed gas, when it get's smaller than cruiciall volume.

 

[The Chairman]

We were watching the Discovery channel on Whales a couple of weeks before... they asserted that whales went to 1500' all the time in search of their fav food... giant squid. THAT'S a lot of pressure!

 

[Liquid]

I can't agree without tasting it...

 

[Dr Deco]

All of these sea creatures simply do not carry enough gas with them to get DCS. If they took along a scuba bottle, the story might be different!

Dr Deco

 

[rcohn]

Dr Deco,

How much gas is needed to get DCS? The bubbles are very small. How much N2 is dissolved in the body during a typical dive?

Ralph