125 feet air dive DCS risk?

[Into the Water]

Thanks everyone for info.

 

[B24L]

Would not recommend deep stops that are not required, as stated above you will on gas, adding to any deco obligation and need to off gassed at shallower depths. The idea of deep stops was an idea that was picked up for a time but had no science behind it. Profile desn't sound extreme but DCS can happen to anyone at anytime. Maybe PFO.

 

[Into the Water]

With deep stops I was meaning more ref. points not really deep stop, when you ascend from 100% to 75% with 1 min stop just for stabilizing, checking and same to 50% with relative-fast speed 30-35 feet /min and after 50% MD continue with 10feet/min with 40, 30, 20, 10 feet stops.
Just in case having BT 25-30min on depth 100-120feet don't think it's good idea for very slow ascending (6-9feet/min or even slower) all the way up to shallow, maybe I'm wrong, that's why just keeping myself in limits until one day I will get t1

 

[Diver0001]

Hi
Would really appreciate if some body with good deco theory experience and deep air diving help me to analyze few dives. And write some arguments.
How safe would be to dive same dives in warmer water in term of DCS? What was main mistake on diving that kind of profiles? Could be DCS be avoided with diving same profile in warm water or with longer deep stop 80%, 50% and shallow stop 20 feet and 10 feet?

Neither one of those dives would carry a significant DCS risk if they were done as the first dive of the day. Given the 1:42 min SI I would also submit that the vast majority of divers would have been able to make the second dive cleanly as well and I suspect that the computer was perfectly happy with those profiles. Both profiles also visually look perfectly responsible. I get no alarm bells from that. I think you just got unlucky.

What I do see as a risk, however, is the water temperature. You mentioned not having dived for a while before this day and you mentioned that the water was very cold. Cold water is clearly implicated in a higher DCS risk because it restricts bloodflow and fatigue can also be a risk factor.

I dive in similar water temperatures (or even colder) in the winter in the Netherlands and we make 1 dive per day, not two. The reason for that is because your body simple can't "catch up" with the cooling you got during the first dive and you *start* the second dive undercooled and it just goes down hill from there. We do make deco dives in the winter here (which your dives were not) but when doing so we extend the deco stops considerably to account for the cold.

So.... it sounds like you're trying to get advice about what to do differently in the future to avoid a repeat. A couple of ideas might help.

1) do one dive a day when it's that cold, not two
2) If you must do two dives then extend the SI. Double it, at least and make SURE you are warmed up before you start gearing up for the second dive
3) extend safety stops
4) use nitrox to extend NDL's
5) set your computer on a more conservative setting
6) make shallower dives

Those are things that come to mind immediately that will help you avoid a repeat.

To address your other question, making a different ascent profile (stops at different depths as you speculated) would have had, in my opinion, no effect on the outcome. Moreover, technical divers generally shy away from RGBM and deep ascent lines because.... well.... the advertising is much more convincing than the results. Most (all most all) technical divers these days use Buhlmann with GF. RGBM is generally considered by technical divers to be ... well ... dangerous.

That said, for recreational dives it shouldn't matter at all if you put in an extra "deep stop" in or not. Since you have an RGBM computer, then the best advice is to follow the deep stops if it recommends them but then to extend the Safety Stop by the same number of minutes (at least) that your computer recommended staying deeper.

R..

 

[Duke Dive Medicine]

Would not recommend deep stops that are not required, as stated above you will on gas, adding to any deco obligation and need to off gassed at shallower depths. The idea of deep stops was an idea that was picked up for a time but had no science behind it. Profile desn't sound extreme but DCS can happen to anyone at anytime. Maybe PFO.

Concur with all of the above except that PFO is not associated with the symptom type or onset time that the OP described. PFO here would probably be a red herring.

Best regards,
DDM

 

[Into the Water]

Neither one of those dives would carry a significant DCS risk if they were done as the first dive of the day. Given the 1:42 min SI I would also submit that the vast majority of divers would have been able to make the second dive cleanly as well and I suspect that the computer was perfectly happy with those profiles. Both profiles also visually look perfectly responsible. I get no alarm bells from that. I think you just got unlucky.

What I do see as a risk, however, is the water temperature. You mentioned not having dived for a while before this day and you mentioned that the water was very cold. Cold water is clearly implicated in a higher DCS risk because it restricts bloodflow and fatigue can also be a risk factor.

I dive in similar water temperatures (or even colder) in the winter in the Netherlands and we make 1 dive per day, not two. The reason for that is because your body simple can't "catch up" with the cooling you got during the first dive and you *start* the second dive undercooled and it just goes down hill from there. We do make deco dives in the winter here (which your dives were not) but when doing so we extend the deco stops considerably to account for the cold.

So.... it sounds like you're trying to get advice about what to do differently in the future to avoid a repeat. A couple of ideas might help.

1) do one dive a day when it's that cold, not two
2) If you must do two dives then extend the SI. Double it, at least and make SURE you are warmed up before you start gearing up for the second dive
3) extend safety stops
4) use nitrox to extend NDL's
5) set your computer on a more conservative setting
6) make shallower dives

Those are things that come to mind immediately that will help you avoid a repeat.

To address your other question, making a different ascent profile (stops at different depths as you speculated) would have had, in my opinion, no effect on the outcome. Moreover, technical divers generally shy away from RGBM and deep ascent lines because.... well.... the advertising is much more convincing than the results. Most (all most all) technical divers these days use Buhlmann with GF. RGBM is generally considered by technical divers to be ... well ... dangerous.

That said, for recreational dives it shouldn't matter at all if you put in an extra "deep stop" in or not. Since you have an RGBM computer, then the best advice is to follow the deep stops if it recommends them but then to extend the Safety Stop by the same number of minutes (at least) that your computer recommended staying deeper.

R..

Thank you for your answer, I think you get it wrong, to be clear it's not me who was diving
My diving limit is 30m and only in warm water I can go little bit deeper and 32% is default in my tanks. Myself I using bottom timer.

If I gonna start diving 40m and below then first I would go t1 course and not gonna relay on any speculations or free advices on diving forums. Again, under deep stop I mean as ref point, instead for crawling up to shallow you could ascend quicker with very short stops for stabilizing. And nobody was talking about deco diving with RGBM deep deco stop.

My question was how to explain with arguments to some individuals that diving on air below 30 meter in cold environment is irresponsible and unsafe way of diving. And as ref. I linked their dive profile which cause DCS.

 

[Diver0001]

My question was how to explain with arguments to some individuals that diving on air below 30 meter in cold environment is irresponsible and unsafe way of diving. And as ref. I linked their dive profile which cause DCS.

I think the reality is that it is not. What you're suggesting is more of a religious discussion than a scientific one. The statistics for accidents will not support your belief. Ratio deco has been implicated in many more bends to the best of my knowledge than diving to 40m on air, assuming it is done responsibly and it is much more likely that it is the limitations of ratio deco that make diving deeper than 30m on air unsafe than anything else.

If you want to discuss this in terms of safety then there are two aspects that follow logically from the depth. (1) that if something goes wrong it goes wrong faster and (2) accidents that happen at that depth tend to be severe. Deep diving shouldn't be taken lightly, of course, but there are more ways than 1 to do so safely.

R..

 

[Steve_C]

Might be a graphical effect, and may not be relevant, but it looks to me like the diver did the last 10 ft very quickly on both dives.

 

[MaxBottomtime]

The profiles do not look like risky dives. Diving on air to 130 feet has been done safely for decades. The only problem I see is the rapid ascents from ten feet at the end of each dive. That's the last place you want to ascend quickly.

 

[RainPilot]

I suspect that might be a factor of rounding on a computer that reads in 10' increments