Should TDI Helitrox replace AN+DP?

[leadduck]

I suspect what @cerich was getting at is that net WOB is a function of equipment and gas density.

I don't know what equipment was used to derive the EADD of 102ft and max EADD of 128ft but a different regulator or CCR could alter the WOB and hence the recommended depths.

If you're referring to Anthony and Mitchell: "Respiratory Physiology of Rebreather Diving", these recommendations were given for planned working dives on rebreathers. But they write they also ran tests on OC gear and the results were virtually the same, that some working dives with densities >6g/l lead to "dive failures" such as divers unwilling to continue work for shortness of breath.

 

[cerich]

I suspect what @cerich was getting at is that net WOB is a function of equipment and gas density.

I don't know what equipment was used to derive the EADD of 102ft and max EADD of 128ft but a different regulator or CCR could alter the WOB and hence the recommended depths.

exactly, plus there is a ton of focus on NN which IMHO has been blamed for CO2N issues leading to death.

Frankly NN to kill you needs some serious PPN, CO2N, with high WOB (whatever reason) will get a diver, and often because the true cause is not known, and barring health issues or equipment issues in testing post people see depth and blame NN.. which is pretty unlikely as the PPN needed means that Ox Tox is more likely to occur before you reach the death stage of NN.

 

[cerich]

If you're referring to Anthony and Mitchell: "Respiratory Physiology of Rebreather Diving", these recommendations were given for planned working dives on rebreathers. But they write they also ran tests on OC gear and the results were virtually the same, that some working dives with densities >6g/l lead to "dive failures" such as divers unwilling to continue work for shortness of breath.

YOU said " This is based on CO2 retention as a function of WOB. The only way to modify those numbers is with helium. "

WOB and gas density are interrelated but not the same thing.

My read of that study is that high WOB (which equipment most certainly is a mitigation or contributor to) is by itself a factor in CO2 retention, AND that gas density BY ITSELF is also a contributor to CO2 retention, leading them to recommend a "ideal maximum gas density of 5.2 g/l (equivalent to air at 102 fsw/31 msw), and a hard maximum of 6.2 g/l (equivalent to air at 128 fsw/39 msw)."

Being somewhat familiar with how various regs perform, even the ideal max. gas density if not reached the WOB will still be high enough to cause serious CO2 retention.

 

[rjack321]

If you're referring to Anthony and Mitchell: "Respiratory Physiology of Rebreather Diving", these recommendations were given for planned working dives on rebreathers. But they write they also ran tests on OC gear and the results were virtually the same, that some working dives with densities >6g/l lead to "dive failures" such as divers unwilling to continue work for shortness of breath.

I know that study well.

I didn't connect in my head that someone had back calculated the recommended diluent densities to those precise EADD depth recommendations.

 

[helodriver87]

YOU said " This is based on CO2 retention as a function of WOB. The only way to modify those numbers is with helium. "

WOB and gas density are interrelated but not the same thing.

My read of that study is that high WOB (which equipment most certainly is a mitigation or contributor to) is by itself a factor in CO2 retention, AND that gas density BY ITSELF is also a contributor to CO2 retention, leading them to recommend a "ideal maximum gas density of 5.2 g/l (equivalent to air at 102 fsw/31 msw), and a hard maximum of 6.2 g/l (equivalent to air at 128 fsw/39 msw)."

Being somewhat familiar with how various regs perform, even the ideal max. gas density if not reached the WOB will still be high enough to cause serious CO2 retention.

I said that, not the guy you're quoting.

I understand the difference. But the study didn't qualify those recommendations with anything equipment related. They were flat gas density recommendations. And you can't modify those without changing mix properties. That's the only point I was making.

 

[DiveTucson]

Its almost never just one thing that causes the incident. It's almost always a cascading series of events that leads to an incident. The more of these we break the less likely we are to suffer an incident. Adding Helium and decreasing gas density and inert gas narcosis is helping to eliminate two potential issues thus breaking that chain. Further more it will help with CO2 retention as well.

Have I dove to over 150' on air? Yes. Would I do it again knowing what I know now? Not likely but it would be a calculated decision. Will I teach deep air? Absolutely not. Will I discuss all of this in every class I teach? Absolutely.

The potential for a life threatening incident for me at depth is not worth saving the $'s by not having helium. Is it hard to get and expensive in some places? Yes, but you can almost always figure out the logistics with proper planning.

 

[MomZo]

I am actually looking at the AN/DP and AN/Helitrox courses and I cannot decide on which one to choose.

What are the pros and cons of both courses as Helitrox seems to be exactly the same as DP but with the possibility to dive with 20% He (+/- 5%)

In other words, why not getting Helitrox even if we don't often dive with Helium later, so that at least you could use it if needed.

For instructors, how much is the additional cost relative to helium fills during the course for Helitrox?

 

[martincohn]

He lived
He lost his job as a firefighter
He's on disability
He's partially blind now
He has other nerve damage in his extremities
His bladder function is poor or non-existent
His name is Kirby

"Narcosis management" is a lie by divers who don't know science

Don't end up like Kirby, just breath some damn Helium or don't go as deep.

Life's too short, and diving is too much fun! Keep it that way...

 

[rongoodman]

In other words, why not getting Helitrox even if we don't often dive with Helium later, so that at least you could use it if needed.

No reason at all not to.

 

[MomZo]

But do you confirm that DP and Helitrox are the same course, except the second includes helium fills and probably some explanation about the pros and cons diving with He.

I checked few dive centers and they often offer the package AN/DP or AN/Helitrox for the same price (excluding helium price)