UTD Decompression profile study results published

[Dr Simon Mitchell]

When it comes to Ratio Deco, it has evolved since the original version. The italian project found ways to optimize it, and so it was optimized.

Hello Dan,

Let me say that I agree with many of the sentiments expressed in your post.

However I want to take issue with the quoted statement. Ratio deco has not been "optimized"; it has been adjusted. The stops still begin very deep and there is no basis for a claim that what they are now prescribing is "optimal". Indeed, there is good reason to suspect that deep stops are still over-emphasized.

It may seem like a minor semantic point, but I think that unsubstantiated claims that their methods are "optimal" (see the self-congratulatory video in post 1) which in the case of ratio deco turned out to be wrong are probably behind some of the ongoing conflicts.

Simon M

 

[Dan_P]

Let me say that I agree with many of the sentiments expressed in your post.

However I want to take issue with the quoted statement. Ratio deco has not been "optimized"; it has been adjusted.

Hello Simon,

Thank you for that.

You're right - by "optimized" I did not mean to imply "optimal" in the sense of certainly perfect, rather "adjusted" as you say, or, preferably, "improved".
As you say, it might seem a minor semantic point, but it's only right. There is still no certainty of all factors involved, nor full mapping of the mechanics of the decompression process, so it's quite obvious to me that I can't have any way to reasonably stipulate any method "perfect".

In my view, there are benefits to the methodology of Ratio Deco that transcend any single decompression schedule (optimal or not), but that view must stand on my own accord entirely.
Further, a discussion on the benefits of Ratio Deco, however interesting and warranted I might find it, is different in nature to a comparative analysis of two specific decompression profiles.


On another note, I want to take the chance to applaud your contribution to diving, particularly with your paper "Respiratory Physiology of Rebreather Diving", which I have found to be a highly valuable reference - particularly in talks about maximal operative depth of gasses (namely air on O/C) based on density, and the relevance of hypercapnia versus nitrogen narcosis, even if that may not have been the context for which it's significance was originally intended.

In the end, for all the discussions on the "optimal" deco table, the vast majority of our fellow divers are still prompted to dive to 40m, 50m or 56m on air, which in my view dwarfs the relative significance of our talk, however enlightening or pleasant I may find it.


Sincerely,

Dan

 

[Dr Simon Mitchell]

Hello Dan,

In my view, there are benefits to the methodology of Ratio Deco

I have no problem with that.

On another note, I want to take the chance to applaud your contribution to diving, particularly with your paper "Respiratory Physiology of Rebreather Diving", which I have found to be a highly valuable reference

Thanks. Made possible by Gavin Anthony allowing his QinetiQ density data to be published.

Someone emailed me to ask how to get the paper. It is in the Rebreathers in Scientific Diving Workshop proceedings which I link to here:

Rebreathers and Scientific Diving Proceedings 2016.pdf | Office of Marine and Aviation Operations

Simon M

 

[Michael Guerrero]

So...I looked at page 1. RD induces more inflammatory response than even a 30/85 GF Buhlmann ascent curve. And 30/85 is pretty heavy on the deep stops in my opinion (I dive 70/70). So I guess my thought is you can bin RD in the group of schedules that produce acceptable, yet sub-optimal outcomes as compared to traditional schedules that get your ass off the bottom more quickly and let you fizzle out at the shallow stops.

And seriously, is there any research on the utility of consuming anti-inflammatories prior to a dive, with timing that would result in a reduced inflammatory response during a dive (maybe an hour before)?

Thanks,
Mike

 

[Dr Simon Mitchell]

Hello Mike,

The significance of the inflammatory changes in producing the symptoms of DCS is uncertain, though common sense would suggest that less change is better. To answer your question, I am fairly confident in suggesting that no one has studied the effect of anti-inflammatory drugs taken prior to diving, though interestingly, we published a study of the effect of using them as an adjunct to recompression in treatment of DCS. The divers with DCS who received the anti-inflammatory (as opposed to the placebo) required less recompressions to reach full recovery or a plateau in recovery. That study remains the only randomised double blind placebo-controlled study of anything in the treatment of DCS. I have uploaded the pdf of the paper below.

Simon M

 

[Tassi Devil Diver]

Could some one explain to me what is the point of ratio deco!! I cant see how it can optimize deco or any "benefits to the methodology of Ratio Deco that transcend any single decompression schedule".

Yes I see there are patterns in decompression like for every minute I spend at 40m equates to minute of decompression or for every 1 minute at 70m equates to 3 minutes of deco. But a computer will do a far better job at optimizing deco based on actual depth changes and variations in ascent rate, and as for using ratio deco as a back up I carry two trimix dive computers, heck I could even carry a third with me.

I just don't see the point of any agency persisting with ratio deco, other than as some sort of gimmick to set them apart from other training agencies.

 

[boulderjohn]

Could some one explain to me what is the point of ratio deco!! I cant see how it can optimize deco or any "benefits to the methodology of Ratio Deco that transcend any single decompression schedule".

As it was explained to me when I was with UTD, never, ever use computers. It is possible for computers to make errors or quit working. The human mind, however, ("the computer between the ears") never makes mistakes, and so it can be trusted to calculate average depth, ascent rates, deco schedules, (etc.) while you are engaged in your diving activities and thus arrive at a reliable and "optimal" dive plan.

 

[PfcAJ]

Could some one explain to me what is the point of ratio deco!! I cant see how it can optimize deco or any "benefits to the methodology of Ratio Deco that transcend any single decompression schedule".

Yes I see there are patterns in decompression like for every minute I spend at 40m equates to minute of decompression or for every 1 minute at 70m equates to 3 minutes of deco. But a computer will do a far better job at optimizing deco based on actual depth changes and variations in ascent rate, and as for using ratio deco as a back up I carry two trimix dive computers, heck I could even carry a third with me.

I just don't see the point of any agency persisting with ratio deco, other than as some sort of gimmick to set them apart from other training agencies.

I'll give you a real life example of a dive I did where ratio deco was super helpful.

We were on a wreck at like 150' and had lapped it a few times on scooters. We knew another wreck was a few hundred feet away at 130'. We were able to have a quick powwow and communicate a change in plan based on an adjusted avg depth, then scooter over and enjoy the wreck for that remaining time.

It's immensely handy to know the impact a change in depth has to your deco schedule before you actually do it. It's proactive (I know I can spend this time at this depth and incur this deco with these gases) vs reactive (I did this time at this depth what's my deco obligation?).

 

[Remy B.]

I'll give you a real life example of a dive I did where ratio deco was super helpful.

We were on a wreck at like 150' and had lapped it a few times on scooters. We knew another wreck was a few hundred feet away at 130'. We were able to have a quick powwow and communicate a change in plan based on an adjusted avg depth, then scooter over and enjoy the wreck for that remaining time.

It's immensely handy to know the impact a change in depth has to your deco schedule before you actually do it. It's proactive (I know I can spend this time at this depth and incur this deco with these gases) vs reactive (I did this time at this depth what's my deco obligation?).

Will a Shearwater not tell you the same ?

As well that is a abnormal or ill diving behavior to change your dive plan, how did that impact the gas calculated? or was that 1st wreck not intended for a Deco dive anyway

 

[Patoux01]

I'll give you a real life example of a dive I did where ratio deco was super helpful.

We were on a wreck at like 150' and had lapped it a few times on scooters. We knew another wreck was a few hundred feet away at 130'. We were able to have a quick powwow and communicate a change in plan based on an adjusted avg depth, then scooter over and enjoy the wreck for that remaining time.

It's immensely handy to know the impact a change in depth has to your deco schedule before you actually do it. It's proactive (I know I can spend this time at this depth and incur this deco with these gases) vs reactive (I did this time at this depth what's my deco obligation?).

Yah, but there's a difference in "knowing roughly how much it's gonna change" and "using RD". I mean, any monkey should eventually understand after some deep dives (or some planning of these) that there is something of a correlation between depth and deco, I don't feel like that's "using RD", at least not in the sense of the complete deco schedule (and not in the sense of using RD discussed here, although I get your point).