Shearwater's take on the helium penalty

[Jason]

I was wondering if anybody else read this blog post.

Eliminating The Helium Penalty - Shearwater Research

Sounds like two major shifts will happen if this research holds out.

1) Pretty much all algorithms in use by modern computers will need to be updated...but there is currently no known table worked out for this research.
2) There will be a significant shift from Trimix to Heliox gas mixes.

Thoughts?

 

[nadwidny]

I was wondering if anybody else read this blog post.

Eliminating The Helium Penalty - Shearwater Research

Sounds like two major shifts will happen if this research holds out.

1) Pretty much all algorithms in use by modern computers will need to be updated...but there is currently no known table worked out for this research.
2) There will be a significant shift from Trimix to Heliox gas mixes.

Thoughts?

I think this belongs in the tech section.

 

[rjack321]

1) Pretty much all algorithms in use by modern computers will need to be updated...but there is currently no known table worked out for this research.

Not for decades and its not that critical since you can either fudge the helium %age downwards (which may people have been doing for many years) or just do the minor penalty in an effort to reduce the DCS risk below ~2% (which as a recreational injury rate is very high)

2) There will be a significant shift from Trimix to Heliox gas mixes.

Probably not, the price of helium is not going down anytime soon if ever. People are more likely to be generous in their use of helium in a CCR, but switching to heliox isn't really necessary.

 

[teknitroxdiver]

At a buck a foot or more for helium, there will be no mass exodus to heliox other than perhaps some CCR divers.

 

[Kevrumbo]

The study. . .suggests that there is no evidence for treating helium and nitrogen differently (as reported by Doolette in animals) it is conceivable that the long held belief that helium needs more decompression has compensated for underestimation of required decompression (to achieve acceptable levels of risk) by the decompression algorithms we all use, and that we are doing the right amount of deco but probably for the wrong reason. ~Simon Mitchell.

Helium vs nitrogen decompression

 

[RayfromTX]

It blows me away at how little we know about this stuff. It reminds me of internal medicine. We think we live in a modern age but we are really just wandering around in the dark. Interesting stuff.

 

[KevinNM]

It blows me away at how little we know about this stuff. It reminds me of internal medicine. We think we live in a modern age but we are really just wandering around in the dark. Interesting stuff.

Conducting deco experiments that will produce real data on people is very expensive and nobody wants to fund it these days. ROVs and atmosphere suits are where the commercial firms are going.

 

[rjack321]

Conducting deco experiments that will produce real data on people is very expensive and nobody wants to fund it these days. ROVs and atmosphere suits are where the commercial firms are going.

And intentionally bending people or doing provocative enough profiles to create statistical significance within a modest number of trials between good and bad profiles is (potentially) unethical.

 

[Beau640]

So if I'm reading this right, there's thought that there is no true helium penalty in that just because we add helium to a mix, it doesn't necessarily mean we need to perform more deco by adding deep stops for helium which add in more nitrogen tissue on gassing during those stops. But there is also a "deep" penalty because our models fall apart at greater depths and we know we need more deco. If i'm reading the article right, it's implying that we are doing the right amount of deco for our trimix, but for the wrong reason. We are doing the right amount of deco because of he depth, but not because of the helium.

 

[stuartv]

I feel like the article really just focuses on CCR diving and the question of whether to use HeliOx or Trimix, and, in so doing, leaves a big ole' elephant in the room. From the SW article:

"Their findings: A bounce diver’s decompression requirements depend solely upon the time, depth and level of oxygen (PO2) over the course of the dive regardless of the fraction of helium and or nitrogen used in the breathing mix. In other words the so-called “helium penalty,” i.e. the extra stops and decompression time required when breathing helium mixes on a surface-to-surface bounce dive, does not exist" [emphasis added by me]

This begs the question: For those of us planning OC trimix dives, could we plan the ascent based purely on the FO2 being used and ignore the Helium. I.e. set your Petrel or Perdix to the correct FO2 of the gas(es) you're breathing, but leave the He content set to 0, even if you're actually using trimix? Or, for example, when planning in Multi Deco, set the gases as if they were Nitrox, with the same FO2?

I just talking about doing this to determine the ascent stops and times. If you're really using trimix, obviously there are some other aspects of the planning you'd have to do based on the actual gas you plan to use.

It seems like this would allow you to plan ascents with less time spent doing deco, with, apparently (according to the NEDU study), no increase in risk of DCS.

Or what am I missing?