Past NDL. And then this???

[azstinger11]

The whole trip was on subsurface as downloaded from my computer! I know that surface intervals make huge difference in all these.

Thanks a lot guys. I got to go get some sleep for now.

It was a pleasure and I hope by tomorrow I will have plenty more replies to study.

My mistake, I knew it had a dive planner but didn't know it could show it's own deco/none deco profiles.

 

[BRT]

Does that come with "a more liberal physiology" included as standard?

I mean, seriously,... you read what scenario the OP managed to get himself in... and your advice is that he gets a less forgiving computer?!?

Manufacturers make recreational computers so conservative EXACTLY BECAUSE of the sort of incompetent diving behaviour so clearly illustrated in this thread.

If people dove a little more responsibly, with some sincere respect for their limits and the agency recommendations they're given.... then perhaps the long trend wouldn't have been for manufacturers to make dive computers ever more and more conservative...

On the other hand a more liberal computer wouldn't have told him he was in trouble to start out with and we would not have had this thread.

 

[DevonDiver]

Thanks a lot for all the advices. I do take them all seriously.

And thanks also...to you....for sharing this incident with us.

It's always a courageous thing to share events that expose our fallibility. There'll hopefully be substantial debate from this post.. that will benefit everyone.

 

[DevonDiver]

On the other hand a more liberal computer wouldn't have told him he was in trouble to start out with and we would not have had this thread.

And that is known how?

Because it can be retro-modelled until a sufficiently liberal algorithm is found that would have kept it out of deco?

If he'd had a liberal algorithm, so what??

Mindset would have remained aggressive.

He'd have still have dived three times per day ... pushing NDL on every dive... until EVENTUALLY a lapse of awareness pushed him into cascading slower tissue decompression.

So... same outcome... but instead he'd have been on a liberal algorithm that afforded him much less forgiveness for his dilemma.. and may have led to a different (more painful, and expensive) outcome... .

You can change the numbers 'problem' ... but you aren't changing the real-world inert gas dissolved in tissues problem...

Mindset versus Algorithm

A LIBERAL (aggressive) algorithm combined with a LIBERAL mindset affords you very little capacity for error or ill-luck.

If you dive a LIBERAL (aggressive) mindset, you're better protected by a CONSERVATIVE algorithm.

Vice versa, if you're inclined to be a disciplined and CONSERVATIVE diver in attitude, then you afford yourself the option of using a LIBERAL algorithm without negative consequence.

 

[DevonDiver]

Don’t I risk turning that gas to bubbles by going up “fast” ??? And obviously by fast I don’t mean faster than 30 feet-10m/min.

Further to what BoulderJohn contributed earlier, my 2013 article on "optimal ascent speeds" may help explain some concepts:

Best Ascent Speed for Scuba Diving

 

[scubadada]

Cressi RGBM is arguably the most conservative of the commonly used commercial decompression algorithms. Once going into deco, your ascent should have taken about 3 minutes, rather than 20 min. Regardless, it is unbelievable to me that you could have chalked up 35 min of deco time. If I may ask, what deco algorithms were your buddies diving and did they also incur a deco obligation. I don't think you are diving an algorithm that will allow you to dive with your buddies.

 

[DevonDiver]

Cressi RGBM is arguably the most conservative of the commonly used commercial decompression algorithms..... . If I may ask, what deco algorithms were your buddies diving and did they also incur a deco obligation. I don't think you are diving an algorithm that will allow you to dive with your buddies.

From the OP:

"I knew from previous dives that my computer (Cressi Leonardo) was quite conservative (compared to my fellow divers’ computers - mostly suuntos zoop, d4 etc) so I didn't worry too much about diving very near my NDL"

All the Suuntos would have been running a roughly equivalent RGBM.

This was a multi-day, aggressive, repetitive dive schedule. Dives were routinely pushed to NDL.

With such an aggressive and extended diving history, there would be so much variance between divers that a comparison of algorithm performance would be near-irrelevant.

This really is classic "a bend waiting to happen" diving behaviour.

Dismissing it as a 'conservative algorithm issue' is a disservice to what should be highlighted from the OP's candid admittances.

Even if the dive hadn't gone into a deco (a more liberal model, anyone?).... the diving is so repetitively aggressive that only a few other seemingly insignificant (pre-disposing) factors need to arise before the story changes into real-life "undeserved bends" in a hyperbaric chamber.

 

[scubadada]

From the OP:

"I knew from previous dives that my computer (Cressi Leonardo) was quite conservative (compared to my fellow divers’ computers - mostly suuntos zoop, d4 etc) so I didn't worry too much about diving very near my NDL"

All the Suuntos would have been running a roughly equivalent RGBM.

This was a multi-day, aggressive, repetitive dive schedule. Dives were routinely pushed to NDL.

With such an aggressive and extended diving history, there would be so much variance between divers that a comparison of algorithm performance would be near-irrelevant.

This really is classic "a bend waiting to happen" diving behaviour.

Dismissing it as a 'conservative algorithm issue' is a disservice to what should be highlighted from the OP's candid admittances.

Even if the dive hadn't gone into a deco (a more liberal model, anyone?).... the diving is so repetitively aggressive that only a few other seemingly insignificant (pre-disposing) factors needed to arise to scenarios like these into real-life "undeserved bends" in a hyperbaric chamber.

I don't think anybody is saying that diving a more liberal deco algorithim, DSAT, for instance, is contributing to a higher rate of DCS. Some deco algorithms are limiting, without demonstrable benefit. The OP did not know how to dive his chosen deco algorithm.

 

[DevonDiver]

. Some deco algorithms are limiting, without demonstrable benefit. The OP did not know how to dive his chosen deco algorithm.

I'll include this again, as I was adding/editing it to a previous post as you typed your reply.

The benefit is tangible in the way it protects against certain user behaviours.

1. Mindset versus Algorithm
   
   A LIBERAL (aggressive) algorithm combined with a LIBERAL mindset affords you very little capacity for error or ill-luck.
   
   If you dive a LIBERAL (aggressive) mindset, you're better protected by a CONSERVATIVE algorithm.
   
   Vice versa, if you're inclined to be a disciplined and CONSERVATIVE diver in attitude, then you afford yourself the option of using a LIBERAL algorithm without negative consequence.

What we often see on Scubaboard is EXPERIENCED (inherently learned and conservative mindset) divers expressing opinions on algorithm safety margin.

There's an issue when INEXPERIENCED divers attempt to emulate those sentiments and attitudes.

We know the saying... "there's old divers and there's bold divers, but there's no old, bold divers".

The old divers have learned the lessons that earn them the right to use liberal algorithms without escalated risk.

The bold divers... are better advised to stick with conservative models pending those lessons being learned over the years..

 

[kafkaland]

Does that come with "a more liberal physiology" included as standard?

Thank you, Andy, for pointing this seemingly trivial issue out. I really wish it was as easy to change my physiology and the environmental conditions as easily as I can change the parameters on my computer. Wouldn't it be nice if I could shave twenty years off of my age, or heat the Great Lakes by twenty degrees (well, maybe not for ecological reasons) as easily as it is to increase my gradient factors by ten?

The very basic principle that you have to make your dive profile fit the algorithm that you deem safe for yourself and not the other way around does not seem to be universally understood. I had a DM on a dive boat in Cozumel admonishing all of us to set our computers to the most aggressive setting, because he didn't want anyone to go into deco *sigh*.