Baron015
Member
Who is imposing the fine ? For what purpose ? All sounds most unusual.
Diving too carefully?
- Thread starter Ben Field
- Start date
Who is imposing the fine ? For what purpose ? All sounds most unusual.
Baron015
Member
Started 15/85, then moved to 30/80, then 40/80, last year ran 65/75 and this year running 70/80.
I'm certainly not calling for a return to bend and fix ascents and sub-clinical aches and pains on the drive home and day after... but a certain amount of common sense, especially as a backup/bailout is surely in order?
If you need to bailout and have a broken unit on a recreational dive you don't need to creep up doing 10:80 GF ascent over half an hour- just get-off, get up, get out and sort it on the boat.
Sometimes you can be so-far inside the curve it becomes tedious
Thoughts?
I agree. In the 15 years I have been watching trends, I defiantly see more safety being added to more safety added to more..... It keeps growing every year, but why? The real world DCS rate is a tiny tiny fraction, and most of those are caused from conditions of poor planning, preparations or procedures, and not the underlying deco times.
So why does the population want more and more??? One reason is the dive population is getting older, and research tells us that old divers need more deco. But the rest of it seems to be for reasons only that last years extra time, is now today's minimum.
Still can't face the facts..... Here is your report on this from 2001 ... you did NOT go to the pot! Also missed a couple of caveats: it was your own version of VPM code you were testing. You missed stops, you cut the deco short. You wrote "...I knocked about 5min off my 6m stop because I was cold, bored and worried about my car..."
Is this the annual deepstops / GF thread
Matthieu
Looks like it. Lets fix some of those errors, and address some miss-understandings shown so far in this thread.
Our online dive database now has 135,000 dives records from X1's and DR5's. Of those 120,000 are with VPM-B and about 22% are CCR. If we look at the conservatism levels across those, it's like this:
Conservatism level: Zero=8640 One=7428 Two=30741 Three=50263 Four=10810 Five=7985
You can see more people select the fastest, than the slowest speed of deco (though I suspect some of that is modified with add on times).
Mark, there is still an appetite for faster and less conservative deco. Obviously it works well for some, and per Ben's observation above, the majority would seem to be doing "more than enough" deco. I'm in the older group of divers too now (like you), and I realize I need to take it easy, so I'm a +3 now. But sadly, it seems too many of our elderly experienced divers want the entire diving conservatism playing field shifted, just to fit into the aging diver profiles.
You have made an association in two types of microbubble, that is not correct. Tissue microbubble, and venous microbubble (VGE), are not the same thing. VGE are thought to grow in the venous system from passing dissolved gas. You cannot judge tissue microbubble growth from VGE presence or volume, and its documented in research this way too. Most in the science community recognize that fact, but a couple want to trick you into making a connection between tissue and venous micro-bubbles. Don't get sucked into the junk science fad.
VGE come from supersaturation - which is present in every dive, including simple NDL dives. You can lower the overall supersaturation a little by making the deco longer (the DAN experiment), and spreading the off-gas over more time. That is the basic principle of 'longer is safer', which is part of all deco planning. High VGE are present is fast shallow stop dives too, which Spencer first documented in the early 70's.
Bend??? Really? Your report above is a typical visual disturbance that occurs in non-divers and the population in general - ask your eye doctor specialist next time your in for an eye exam. It's also a nitrox hi ppO2 warning symptom. Why would you try to imagine this to a diving or DCS cause?
**********
For those who wish to revisit the NEDU study, some diagrams of the discussion are here: Nedu test diagrams
Also our MultiDeco desktop program has a proper Supersaturation graphing system, where you can see for yourself which profile types are causing the most stress.
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lizardland
Active Member
As I've pointed out every time you trot out the same argument I got bent more than once on vpm. One of which got me a trip to the pot. It was pretty much exactly a year after that one.
GLOC
real name: Gareth Lock!
Originally Posted by GLOC
My bend in Malta (due to PFO) wasn't reported to BSAC and I never went to a chamber as the symptoms (visual disturbances, nothing else) cleared up within 30mins or so of the onset.
Bend??? Really? Your report above is a typical visual disturbance that occurs in non-divers and the population in general - ask your eye doctor specialist next time your in for an eye exam. It's also a nitrox hi ppO2 warning symptom. Why would you try to imagine this to a diving or DCS cause?
Ross,
The symptoms I experienced are indeed similar to visual aura associated with migraine (which I have never had) but it did appear to be a fairly major coincidence that I had never had visual disturbances before, that when I lifted the twinset from the ground to the back of the LDV approximately 30mins or so from surfacing, holding my breath as you do when lifting something like that, that I got a very large visual disturbance. I also had some minor disturbances on the boat but that would have been 2-3 mins after surfacing and so my pO2 levels would have dropped (and I have never seen anything validated about the 'off effect'. Admittedly I had no other symptoms such as you would associate with DCS and they went away after time. However, when I got back to the UK I had a PFO test with Dr Mark Turner and found that I had an 8mm x 12mm PFO which has been subsequently fixed with an Amplaster device. As part of my RAF medical I had to see the medical board and the only thing the President of the board, one of the world leading doctors on high altitude rapid decompression, could think of was excessive bubbling in the eye as there were no other symptoms, but seeing as that is nigh on impossible to test in lab conditions following dives, then there is limited evidence to prove one way or another.
However, the point I was making that the prevalence of DCS is likely to be much higher than actually reported because people don't report it to systems like BSAC or the HSE or they don't go to a chamber to get treated.
Regards
So you merged two stories into one, and never told anyone about the second occurrence in 2002 ???? This I find hard to believe.
"I got bent more than once..." ... this I believe, but blaming the model was not going to solve the issue. Do you work with hand tools? How many fingers do you have left?
lizardland
Active Member
And your many outbursts like these are why I won't use your products.
Believe what you like, I couldn't give a **** and I'm not wasting my time arguing the point.
"You must spread some Reputation around before giving it to lizardland again."
No, but it has gone woefully off-topic
My OP was less about extreme dives but more the mundane recreational stuff being done after reading too much online and using GF's and VPM fancy deco computers on no or minimal stop dives and doing hugely excessive (from a point of view of necessity) decompression.
I can think of several instances of divers getting cold or hurting themselves rushing to dekit and get to the heads because they've done or waited with a dubby who deco'd their arse off for no reason- divers should know what the bare safe minimum is... my query was do the computer only divers know that minimum and how much they are overshooting?
For the non BSAC divers, the Dive Conduct Slate as mentioned...
View attachment 7370
The table looks "normal" for me re: no deco limits.
Deco-wise I would be bent like a pretzel with such minimal stop times. I know because I have been bent and slightly bent before and I don't really see the point in being aggressive with deco like that. Sure I would rather be bent than drowned, but I don't think that's where this thread started.
Ben Field
All IMVHO obviously...
My point was that that isn't aggressive, its just the "old" numbers for safe deco.
Not that you personally should/would use anything but very conservative deco if you've already had two twangs (I hope fully recovered from and you established why/had a PFO check?)
I know some divers, even BSAC divers with age/experience to remember the '88 tables who think (I don't know why) that so little deco is dangerous- yet those are air tables and they are now doing triple the deco on Nitrox and CCR- I agree abit of conservatism comes with age but it borders on the silly at times.
I wonder if some divers Like to be seen reporting lots of stops as it suggests great feats where achieved to require it?
Yeah I have been checked for PFO - negative. I believe my deco needs arise from scar tissue related to spinal disk surgery. I don't really mind/care although sometimes my buddies look at me quizzically when I ask for 5-10 more mins in the 3 to 6m window.
Yeah or that very precise stops are required.
On my first CCR cave diving trip this past week I have to admit I really liked being able to deco where it was convenient which was rarely at 6m. More like 7 or 9m. Just happened to be where I could settle down, but I wouldn't have breathed O2 there and would have been inefficient to hang there on OC EAN32.
Yeah or that very precise stops are required.
On my first CCR cave diving trip this past week I have to admit I really liked being able to deco where it was convenient which was rarely at 6m. More like 7 or 9m. Just happened to be where I could settle down, but I wouldn't have breathed O2 there and would have been inefficient to hang there on OC EAN32.
Simon Mitchell
Well-Known Member
Just in case anyone actually pays any attention to this:
There is not a single person in the "science community" who would endorse that interpretation.
"Passing dissolved gas"? Passing from where??? The tissues receive blood via the arterial circulation. The arterial circulation effectively starts in the lungs where blood inert gas pressure equilibrates with ambient pressure before the blood enters the arteries themselves. There is thus no supersaturated inert gas in the arterial blood. The arterial blood only becomes supersaturated when it then enters the capillaries of tissues that are supersaturated. Indeed, these capillaries are effectively part of the tissue. By the time blood emerges from the other end of those capillaries as venous blood, some bubbles (VGE) may have formed, but make no mistake, they have formed from supersaturated inert gas that the blood has 'acquired' from the tissues. For obvious reasons more VGE almost certainly indicates greater tissue supersaturation (and a greater propensity for bubbles to form in the tissues themselves). No one has ever claimed that VGE and tissue bubbles form in direct proportion to each other, but it is nonsensical to try to argue that the two processes are completely unlinked.
Utterly unbelievable that you would comment authoritatively on this medical matter which is totally beyond your very limited expertise.
The onset of visual symptoms immediately after lifting or straining early after a dive in someone with a large PFO is entirely consistent with an effect of a shower of small venous bubbles entering the arterial circulation.
Simon M
There is not a single person in the "science community" who would endorse that interpretation.
"Passing dissolved gas"? Passing from where??? The tissues receive blood via the arterial circulation. The arterial circulation effectively starts in the lungs where blood inert gas pressure equilibrates with ambient pressure before the blood enters the arteries themselves. There is thus no supersaturated inert gas in the arterial blood. The arterial blood only becomes supersaturated when it then enters the capillaries of tissues that are supersaturated. Indeed, these capillaries are effectively part of the tissue. By the time blood emerges from the other end of those capillaries as venous blood, some bubbles (VGE) may have formed, but make no mistake, they have formed from supersaturated inert gas that the blood has 'acquired' from the tissues. For obvious reasons more VGE almost certainly indicates greater tissue supersaturation (and a greater propensity for bubbles to form in the tissues themselves). No one has ever claimed that VGE and tissue bubbles form in direct proportion to each other, but it is nonsensical to try to argue that the two processes are completely unlinked.
Utterly unbelievable that you would comment authoritatively on this medical matter which is totally beyond your very limited expertise.
The onset of visual symptoms immediately after lifting or straining early after a dive in someone with a large PFO is entirely consistent with an effect of a shower of small venous bubbles entering the arterial circulation.
Simon M
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Mark Chase
ATB=AlwaysTalkingBollocks
Lets not confuse conservatism with the holy grail of the most efficient profile
First off I want the best way to aproach deco (which is where age / fitness are irelevent) and then I decide how to pad it.
Strangly 20 years ago when I started deco I was running much more conservitive profiles than I am running today. As my depths and run times have grown I have started looking for efficiency and have tried to balance that against A: The risk of a bend & (in many ways more importantly) B: the risk of long term sub clinical dammage.
I know and have dived, with a lot of people young and old who have run agressive deco (by which I meen in excess of 100GF for the shalow stops) be that as a result of VPMB profiles, ratio deco profiles or Bhulman profiles.
Not all, but most of them have started to develop a low tolerance for decompresion dives. Some have gone for PF0 testing and found they have PFOs. Some were clear or havent been tested. Most have now settled on doing either less deco + softer profiles, softer profiles or no deco at all.
I know people who have been diveing for 20 years and doing 60-100m dives with 3-4 hour run times who suddenly starts getting bent and blame it all on a PFO?
I dont beleive it.
The statistical chance of having a PF0 is very high and I am unconvinced it would cause sudden suseptabuility to getting bent after so many years of getting away with it.
Yes health and fitness deterioation with age is an issue (but cirtainly not with some of them) but I beleive they were all running far too agressive deco and over time sub clinical dammage turned to clinical dammage.
I have no proof but I find it odd that almost all of them were doing what id call agressive run times on the shalow stops.
ATB
Mark
I'm not saying "... that the two processes are completely unlinked..": those are your words Simon. That is your gross miss interpretation. It is you trying twist matters out of proportion in some pompous manner.
The scientifically accepted source of VGE is what I briefly described - they are thought form on the venous endothelium from passing supersaturated venous blood. That's what the Bennett and Elliotts' Physiology and Medicine of Diving, book is saying.
But I sense you want to change that concept to suit your new "VGE is bad" paradigm.
A person "with a large PFO", is going to have all kinds of deco issues, and should not be doing high risk dives at all, and most likely have a long history of troubles.
Further, your theory fails given the following study:
J Appl Physiol (1985). 2013 Sep 1;115(5):716-22. doi: 10.1152/japplphysiol.00029.2013. Epub 2013 Jun 13.
Exercise after SCUBA diving increases the incidence of arterial gas embolism. Madden D1, Lozo M, Dujic Z, Ljubkovic M.
Here they found more than half of the subjects created AGE, just from post dive exercise (they were all non PFO people). So one might assume if half of us can have AGE from shore diving and climbing the ladder, your vision cause theory would be common place in diving. But i don't think it is.
I also had a private conversation with G on this matter, and I'm sticking by what I said above.
........
Once again we see you Simon taking every opportunity to make attacks against me... because I dare to stand up to his egotistical arrogance and fallacies.
Hi Mark,
That holy grail you seek, does not exist. All deco is detrimental in some way, has risk, and is a compromise between bad factors. The "most efficient" is not an appropriate term to describe deco. You should instead state your acceptable risks in certain areas of deco, and choose a plan accordingly. You can bias your profile to favour certain features of deco, but they all come at a cost.
Remember we are forcing high pressure gas into tissue and bone, and letting it out again slowly, in a way that has never been part of our human evolution. Fiddling the deco a little this way or that way, is not likely to change the long term outcome.
Our bodies age - we get old sore and slow, and have reduced physical abilities. Diving is a physiological activity. Why do you think that divers should be excused/absolved of that process?
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You got to be f*cking kidding:
Is that right? I'm totally surprised!
There's at least 2 reasons they would form there:
- the venous blood is less (super)saturated than the tissues, bubbles will tend to form where oversaturation is maximal, and that's at the interface: the endothelium.
- the endothelium provides asperities, irregularities that helps bubble form - just like bubbles form on the surface of a glass.
In any case, that's not the source. It's the location. The source is the gas from the tissues. Just like tissue bubbles.
Did you even read that? Or even the abstract?
Nobody's talking about creating anything. Only arterialisation.
Basically, there's shunts in the lungs that allow blood to bypass the capillaries around the alveoli. Exercise will increase pressure, and that will tend to open those shunts, and increase the probability of arterialisation (i.e. venous bubbles crossing into arteries).
It's another way to get bubbles into arteries, very much like a PFO, but a different location for the shunt.
So to sum up, GLOC said he had a bend diving VPM, and a PFO was found. You said it wasn't a bend at all. GLOC's doctor said it was. Simon Mitchell said it was consistent with the effect of opening the PFO through strain. And your argument that it wasn't a bend is that there's other ways to get one from arterialisation beside a PFO?
Are you for real?
DepthCharge
Member
Can quote the reference to that exact process description you have made here? I don't disagree, but in the literature, its still assumptions mostly.
Part of your comment is being argumentative about semantics (source/location/etc)
I wrote create AGE (arterial gas emboli) .... that is "arterialisation".
Again, why are you being argumentative about semantics?
And the result is called AGE (arterial gas emboli).
No. He didn't write anything of the sort. No VPM here, no doctor visit. You are making those parts up.
Why are you doing these things emmbee?
silentbob
Member
No Ross he doesn't make anything up, he merely read what GLOC had written more closely than you (which is the same thing as saying he actually bothered to read it).
"However, when I got back to the UK I had a PFO test with Dr Mark Turner and found that I had an 8mm x 12mm PFO which has been subsequently fixed with an Amplaster device. As part of my RAF medical I had to see the medical board and the only thing the President of the board, one of the world leading doctors on high altitude rapid decompression, could think of was excessive bubbling in the eye as there were no other symptoms, but seeing as that is nigh on impossible to test in lab conditions following dives, then there is limited evidence to prove one way or another.