Riding GF99 instead of mandatory/safety stops

[rjack321]

Quite an emotional outburst. All this chest beating because you disagree with me on isobaric counter diffusion.

Well ICBD doesn't exist outside of diving bells and commercial scenarios where the divers are immersed in a helium gas. No sports diver ever does this because you'll freeze into a popsicle with trimix in your drysuit - especially with the really high mixes like 10/70 or 8/80

But you seem to think otherwise based on chatgpt or google or some 2005 era bro-science, it's hard to tell.

 

[JMarc]

Isobaric - a process in which the pressure remains constant.

An it refers to the ambient pressure.

That doesn't change the fact that diffusion of is driven by a difference of concentration, and more precisely for gases of tension (which is a way of measuring concentration using a pressure unit and allows to compare concentration in different mediums)

And BTW there is diffusion when the ambient pressure doesn't change even without switching mixes, that's the whole point of doing a stop.

 

[boulderjohn]

NAUI went all in on RGBM, which seemed like a good idea at one point but empirically doesn't seem to work very well.

It's the sort of thing that happens when the developer, owner, and seller of a product is on your board of directors.

 

[lostsheep]

All this chest beating because you disagree with me on isobaric counter diffusion.

It’s not just Nick that disagrees with you, the data do too.

 

[boulderjohn]

This is just a general observation that this thread as a whole shows a problem within the scuba diving community as a whole. I first saw it when one of my former students did a dive with a tech instructor who freaked out when he saw the GFs my former student was using. The instructor had learned back in the very deep stop era when 20/80 was the norm and had no idea that current thinking had left all that behind. I did a quick Google search and found that well over 90% of the articles were still extolling the virtues of deep stops. I wrote an article summarizing current thinking, hoping to make some attempt to balance it out, but there was no good place to put it that was general enough to override that old-school thinking.

That's the problem. We learn current thinking and then don't have a good way to find out years later that the thinking has changed.

 

[rjack321]

That's the problem. We learn current thinking and then don't have a good way to find out years later that the thinking has changed.

It's not really that different than needing to do continuing education like in any other industry. The seminars, literature, conferences are out there.

But otherwise, this is a flaw in the "AI learning model" aka I googled it and chatgpt told me something. That is functionally just web crawling for anything related and putting the results into a synopsis paragraph. If there's a mountain of writing about a flawed and known or erroneous concept like the oxygen window or ICBD or deep stops then you get a whole very 'expert' sounding paragraph about them which is more than likely state of the art for 25 years ago.

 

[Nick_Radov]

That's the problem. We learn current thinking and then don't have a good way to find out years later that the thinking has changed.

I guess that's like the "law of primacy" in education: students tend to believe whatever they heard first, regardless of later contrary information. Maybe technical training agencies should require a certain number of "continuing education" credit hours every year to maintain certification, like doctors. Probably not realistic, though.

 

[EFX]

The instructor had learned back in the very deep stop era when 20/80 was the norm and had no idea that current thinking had left all that behind.

That's the problem. We learn current thinking and then don't have a good way to find out years later that the thinking has changed.

There hasn't been any scientific study done on bubble models that incorporate deep stops that I know of. The shift away from bubble models is partly due to the simpler dissolved gas model and the ease in modifying the model through GF's for personal use. Bruce Weinke who has since passed away developed the RGBM (Reduced Gradient Bubble Model). Bruce kept a database of RGBM dive profiles. Out of 2800+ profiles, 20 cases of DCS were reported for a 0.71% incident rate. This is compared to 0.45% incident rate for Buhlmann models.

 

[boulderjohn]

I guess that's like the "law of primacy" in education: students tend to believe whatever they heard first, regardless of later contrary information.

Recent studies spurred by the torrent of lies and other forms of misinformation flooding the political landscape have shown that when a person is misinformed, that person will not only continue to believe the misinformation after being given accurate information, that person's misinformed resolve will deepen--they will defend the misinformation vigorously.

Maybe technical training agencies should require a certain number of "continuing education" credit hours every year to maintain certification, like doctors

Where would someone take such a course? That's my point. To my knowledge, such a place does not exist.

PADI's trimix course required training on deep stops, including requiring dives using deep stops. The course also urged student to stay current with changing thinking. I wrote and pointed out the change in thinking on deep stops and said it was a conflict--what was I to do? They told me that new knowledge negated the requirement--I could ignore the deep stop requirement for my students. A few months later they sent that message to all instructors.

If that sort of thing were done by all agencies, that would help, but it would do nothing for the average diver who learned and is not receiving that information.

 

[rjack321]

There hasn't been any scientific study done on bubble models that incorporate deep stops that I know of. The shift away from bubble models is partly due to the simpler dissolved gas model and the ease in modifying the model through GF's for personal use. Bruce Weinke who has since passed away developed the RGBM (Reduced Gradient Bubble Model). Bruce kept a database of RGBM dive profiles. Out of 2800+ profiles, 20 cases of DCS were reported for a 0.71% incident rate. This is compared to 0.45% incident rate for Buhlmann models.

Well the NEDU study is fairly relevant here even, if they didn't test VPM or RGBM vs Buhlmann which would have both more directly applicable to recreational/sports divers.