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HPNS and Deep Saturation Diving on Trimix

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HPNS and Deep Saturation Diving on Trimix

Post Number:#1  Postby John F SeaDemon » Sun Apr 01, 2007 2:48 am

Deep diving on Trimix is good as it lessens the chance of getting Nitrogen Narcosis and Oxygen Toxicity (if using hypoxic mix, true to a certain depth for normoxic mix). If a diver cannot afford to use Helium in his/her mix, then it is best for the diver to stay shallow.

However, there are four disadvantages of Helium:

1) Really expensive (a normoxic mix of 18/33 in a 12L twin-set can cost up to RM300 per dive if filled to 200 BAR),

2) It has high heat conductivity: it robs the diver of body heat at a rapid rate,

3) More difficult to decompress (requires longer deco stops than on air),

4) High risk of serious decompression sickness if deco plans are not adhered to strictly.

However, another risk divers face when diving deep on Trimix (and Heliox) is HPNS.

What are the steps/limitations a diver should know about how to avoid HPNS?
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Re: HPNS and Deep Saturation Diving on Trimix

Post Number:#2  Postby Snafu » Sun Apr 01, 2007 11:05 pm


However, another risk divers face when diving deep on Trimix (and Heliox) is HPNS.

What are the steps/limitations a diver should know about how to avoid HPNS?


Dive above 150m.

;D
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Re: HPNS and Deep Saturation Diving on Trimix

Post Number:#3  Postby John F SeaDemon » Sun Apr 01, 2007 11:10 pm

I believe there is also the factor of rate of descent right? Mostly applicable to Sat Divers on Heliox? Is that correct? What's the recommended rate of descent?
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Re: HPNS and Deep Saturation Diving on Trimix

Post Number:#4  Postby Snafu » Sun Apr 01, 2007 11:18 pm

I believe there is also the factor of rate of descent right? Mostly applicable to Sat Divers on Heliox? Is that correct? What's the recommended rate of descent?


Rate of descent is as good as the speed of you able to equalize your ears while blow down.

22m/min - 24m/min sounds about right.

;D
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Re: HPNS and Deep Saturation Diving on Trimix

Post Number:#5  Postby santadive » Mon Apr 16, 2007 6:44 pm

Another factor would be cause of the HPNS.
Just like Nitrogen Narcosis will be brought on by higher Partial Pressures on the N2 -HPNS is the cause of High ppHe!

A simpel way to look at it is basically like this:
We know nitrogen slows you down and interferes with your thought-proces (one of the reasons why we at depth would add He to the gas)
Helium sort of "speeds you up" -partially due to the heat-conduction it will give you tremors (shakes)

If you get your trimix-blend right, the nitrogen helps you against HPNS by enabeling you to control your shakes...
That is why HPNS is more commonly found with Heliox divers or Extreme Deep Divers (record breaking levels)

But the world does look a lot different at 50+   ;D
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Re: HPNS and Deep Saturation Diving on Trimix

Post Number:#6  Postby Snafu » Tue Apr 17, 2007 12:34 pm

That is why HPNS is more commonly found with Heliox divers or Extreme Deep Divers (record breaking levels)

But the world does look a lot different at 50+   ;D


That is right  ;D

;D
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Re: HPNS and Deep Saturation Diving on Trimix

Post Number:#7  Postby bigjoe74 » Tue May 01, 2007 10:30 pm

;D
That is why HPNS is more commonly found with Heliox divers or Extreme Deep Divers (record breaking levels)

But the world does look a lot different at 50+   ;D


That is right  ;D

;D

;)
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