Diving too carefully?
- Thread starter Ben Field
- Start date
Simon Mitchell
Well-Known Member
Excellent post (I can't give you any reputation apparently). Clearly not Michael's "fault", but an excellent example of what can happen even if the "model math" as another poster refers to it seems to think you are OK.
Simon M
Simon Mitchell
Well-Known Member
Dissolved gas accumulated in the tissues during the dive, and bubbles formed in the tissue microcirculation when the tissues became supersaturated on ascent.
According to what Ross? Your "model math"? So when something actually happens we should say it didn't happen because it is not predicted by the "model math"? It happens Ross, and although you can't predict it sitting in front of your computer, I, my colleagues, and the diving medicine literature can assure you that we see it sitting in front of our patients. Thankfully rarely. Sorry.
No, what you are asking is for me to reject decades of received wisdom, enshrined in the clinical diving medicine literature, based on the opinion of a helicopter mechanic.
I really do harbour a level of disquiet that this is the level of deductive reasoning exhibited by someone who sells a "life support product" within this industry.
Simon M
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So if they didn't come from him and his own gas load, what killed him? Are you saying the apparent froth in his lungs was AGE paradoxical to his actual gas load? I need an alternative explanation, with some data not just that the model says he's fine so its impossible to die from VGE...
I looked back and perhaps I missed it, but I am pretty sure I'm not the only person in the world who has felt they were bent, descended and done additional deco with resolution of symptoms. Are you still saying in water hits are not possibly due to VGE?
... and are off gassed in the normal amounts during his deco. Leaving normal amounts of excess tissue and VGE micro-bubbles upon surfacing.
But, minutes after surfacing clutching his chest, he collapses and dies shortly afterwards.
Does that sound like normal? I hope not, because millions of divers every year do exactly the deco profiles and weekend diving, that this man did.
The physics of dive medicine, do not support your diagnosis. Using the Occam's razor principle, there are several other more likely explanations for the events, that do comply with diving physics.
I really do harbour a level of disquiet that this is the level of deductive reasoning exhibited by someone who occupies a senior position in the "dive medicine life support", who (when it suits him) ignores the psychics and math that makes up so much of this field of science.
Hi,
This guy did a normal small deco dive, and he did a normal and conservative deco every time. It was the last of 4 dives over 2 days, with 4 hour surface intervals each day.
But on the last dive, minutes after surfacing and boarding, he clutched his chest, collapsed, and died shortly there after.
What would you think caused his death?
The diving physics and math do not support a "Massive VGE" as reported by Simon. The only validation he has for that, so far is his opinion.
Other possible causes might be (note: i am not a doctor): Arterial gas embolism, heart failure, or respiratory failure from a combination of his medications and exhaustion of 4 dives. These causes sound and fit the events far better.
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Simon Mitchell
Well-Known Member
Millions? Hmmm, but in any event no, it obviously doesn't sound "like normal", but it sure sounds like what Dr Carl Edmonds writes about pulmonary DCS in his on line diving medicine text (see bottom of page 15-4)....
http://www.divingmedicine.info/Ch 15 SM10c.pdf
Here is the key bit (after he explains that it is caused by too many VGE reaching the lungs):
Clinical features also include a tight feeling in the chest, chest pain, difficult and rapid breathing. Coughing is often observed, and may be precipitated by smoking,
hyperventilating or exercise. Frequently the symptoms come on very soon after ascent, from relatively deep dives (over 30 metres) or after prolonged dives. Death may supervene.
....and he certainly does not contextualise the condition as only occurring after surdO2 dives or omitted decompression dives as you have tried to.
rossh said:
They do actually, when you add in the extraordinary biological variability that arises at the interface of physics and real human physiology. But when I was at medical school, and throughout my subsequent 25 year medical career during which I have treated 100s of sick divers, I came to know that the history and clinical features are what makes a diagnosis. Not preconceptions about decompression modelling.
Listen to yourself! If the physics were always right and all that mattered, no one who follows a dive table algorithm properly would get sick.... but it happens all the time (Michael on this thread).
Ross, as long as you have an appetite for making a fool of yourself over this issue, I will continue to point out that you are what you aspire to be. What I won't do is allow you present an unopposed misrepresentation of decades of science and knowledge to our diving colleagues in the interests of supporting your commercially driven agenda.
Simon M
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Simon Mitchell
Well-Known Member
You really do have problems with short term memory. Don't forget the Queensland Coroner, whose opinion was derived from those of Drs Gorman, Edmonds, Mitchell, Fock and Acott (forgot to add his name to my previous list). None of these experts disagreed with the diagnosis of cardiopulmonary DCS. Andrew (Fock) also raised the possibility of a cardiac cause (as a less likely option) in his report, but the autopsy largely ruled that out.
Simon M
"The pathologist who did not have training in diving medicine and did the autopsy (and found gas everywhere as you do following a fatality early after a dive) initially said arterial gas embolism, but immediately changed his opinion when he heard evidence from the diving medicine experts."
So the only one who saw the body changed his opinion. Hmm. Maybe he was right and changed his opinion under the pressure of several experts...
Simon Mitchell
Well-Known Member
Unlike participants on diving forums, most medical witnesses at inquests know how to recognise what is referred to as "overwhelming weight of evidence" that contradicts their opinion, and to change their opinion as a result.
The pathologist was not aware of the fact that gas comes out of solution everywhere post-mortem in when someone with a significant dissolved inert gas load dies, and of the consequent difficulty interpreting the distribution of gas at an autopsy.
The finding of no obvious cardiac cause of death on the autopsy coupled with the pattern of onset of observed symptoms are by far the most important factors in determining most likely cause, as judged in the formal environment of a Coroner's court (can I remind you of that), in this case.
I don't think I need to say any more about the matter.
Simon M
Igor P
New Member
Under the pressure of several experts (scientists)... experts that think they never make mistakes, experts that lot of times are blind for simple answers because their knowledge limits their vision and understanding....experts that are normal humans with their limitations and mistakes.
I have seen kids solving problems that experts in the field couldn't (because their knowledge limited them to see solution).
Couldn't they be wrong...?!?
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Simon, I acknowledge that the physiological world behavior, is sometimes only vaguely connected to the physical world properties, and the two diverge often.
You have made good reference to supporting information - thank you. However, the references and the experts opinions are all from the same source.
******
Here is the problem: You stated that it was a "massive VGE". OK, maybe you embellished that a bit for shock value.
Now, in order to make significant VGE, one needs a significant gas supply to make it from, that resides in the tissues. Then it needs to be removed from tissue, converted to VGE quickly and in large volumes.
To achieve that you need a big dive with fast deco. Or one could take a normal dive, and drive gas out fast under extreme conditions like SurD or direct ascent. Or one could do a really deep dive and surface with significant gas to off load, and drive it out by exertion.
But the victim did not do any of those procedures or conditions. He did a normal small deco dive, a normal easy deco ascent, and promptly dropped dead. Nothing of his dive procedure was capable of making an extra large dose of VGE.
As they say "you cannot make strawberry jam from dog pooh". The ingredients of "massive VGE" were not there.
*****
Lets examine the other side:
Now if you wanted to say something like - he had normal gas loads, normal VGE levels, but a failing respiratory system that was not function fully, and finally give up at the end of this dive - I'd believe you. Under this situation, his lungs are not performing as expected, and the accumulation of VGE overwhelms him. Is such a thing possible?
****
The basic difference between these two explanations:
The first implies extraordinary volumes of VGE and dissolved gas are in motion, in a healthy individual.
The second implies that normal levels of gas and VGE are in motion, but the individual is suffering from a weak or failing respiratory system, that eventually cause his death under the added stress of normal decompression.
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Mark Chase
ATB=AlwaysTalkingBollocks
Yes but wernt they given a solution by the pathologist but rejected it?
Its hardly a case of cant see the wood from the trees
If the patholagists initial explination was reasnoble I am strugling to see the benifit of altering it for any of the people involved.
HOWEVER
I am intreagued by the comment from Ross that this was a small dive with little deco, so why were the VGE numbers so high?
I need some clarification on how high VGE can result from an aparently recreational dive profile?
That said i remember being in the chamber at whips cross (Carbon Monoxide poisening) and discussing shallow diveing with the hyperbaric doctor during my treatment and he laughed when I sugested 30m was a shalow dive.
Anything below 6m is deep, he said
I rememberd that when the coment of "deep dive" was asociated with max 30m
Thinking about it I have probably witness more suspected bends and proper full on bends on 30m dives than I have on tec dives.
ATB
Mark
Simon Mitchell
Well-Known Member
You asked for a second opinion on the issue of cardiopulmonary DCS occurring after "normal" dives. I give you Carl Edmonds, plus the other experts in the case I linked to, but now you imply they don't count basically because we were all involved in the same case and we all agreed???? What sort of twisted logic is that?
rossh said:
No Ross, I'll tell you what the problem is. It is that your theoretical calculation of what should be happening does not match what actually did happen (and what I and many other diving physicians have seen happen multiple times in perfectly fit and well divers over our careers). That is why it is in all the text books. I have seen a number of such cases (probably ~10). Mostly they develop shortness of breath and cough early after surfacing, and most rapid resolve with oxygen administration. I have seen one other fatal case and a couple that went on to develop spinal symptoms as well. The coroner's case is just one that I can link to and name because it is in the public domain.
You cannot explain all DCS cases in terms of your "model math". As I said, if you could, then there would be no such thing as DCS in situations where the diver adhered to the model math. This sort of case, for some reason, develops much higher numbers of VGE than might be predicted after a dive. The one thing virtually all cases have in common is that they follow deepish dives usually involving decompression. And yes, the risk is obviously higher if there is omitted decompression. But there have been plenty, like the one I linked to, where the case followed a dive with no decompression error.
rossh said:
I think your metaphor is in poor taste given we are talking about the death of a fellow diver. And you are wrong. High bubble grades are commonly measured after decompression diving conducted precisely to the prescribed algorithm. For some reason, on this day, this diver formed even more than normal. But be my guest: continue to ignore reality (and the opinions of multiple leading experts with a huge collective experience of actually treating sick divers) in favour of your theory.
rossh said:
There was no evidence to support such a hypothesis in the autopsy.
Ross, this debate is about whether VGE are harmless and should be ignored as you have claimed. This case is just one of many cardiopulmonary DCS cases (which are caused by VGE), and cardiopulmonary DCS is far from the most important form of DCS linked to VGE (as I have pointed out many times).
Simon M
Ben Field
All IMVHO obviously...
Unsurprising IMO (trying to steer back on topic) "tec" divers (I hate that terminology) are knowingly going into deco and are prepared and should be armed for it, sometimes recreational divers get into deeper dives that they planned in the 30-40mtr range which is easy on simple kit and safe with good planning but deep enough to bend the snot out of you if it goes wrong.
Perhaps this is what has led some to do what my OP referred too- treating 30-40mtr dives like serious exploration dives with multiple stages and excessive deco, because it is deep enough to get "proper" decompression some divers feel they have to go in belt and braces?
My rebreather was awaiting sensors a couple of years ago and I'd signed up to do a 52mtr dive I didn't want to miss, there wasn't time to do anything else so I took a single 15ltr with light mix, a little stage of nitrox for good old-fashioned Air&80 ascent and a scooter to avoid any effort. I got funny looks for being "under equipped" but after the dive it transpired I had done the same BT of 20min as most of the others and faster ascent on pre-written tables than their deco computers.
In hindsight it was completely safe, in fact much safer that dives I'd done previously to 45-60mtrs on single tanks of air with no bailout except a similarly equipped buddy. Given the choice I'd have had a CCR with a stage- so many precautions its not hard to see why deepish recreational diving is possibly more risky that diving slightly deeper but over-equipped "Tec" diving?
Mike Ferguson
WTF is that?
must be something to do with being in the pacific rather than the Atlantic.
I seem to recall spending a lot of years doing a lot of 60m plus dives on air (a lot with single tanks) and I'm neither dead, permanently disabled or blind. nor are any of my mates that I regularly did those dives with.
these days I'd rather do those dives on a rebreather with trimix because it's about a hundred times easier for old blokes like me, but deep air dives do not equal instant death.
I seem to recall spending a lot of years doing a lot of 60m plus dives on air (a lot with single tanks) and I'm neither dead, permanently disabled or blind. nor are any of my mates that I regularly did those dives with.
these days I'd rather do those dives on a rebreather with trimix because it's about a hundred times easier for old blokes like me, but deep air dives do not equal instant death.
Igor P
New Member
Well writen! You deserve some green! I am alive too
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I know of two single tank deaths both at 50+m. One is bad hit (was on doubles but passed out due to narcosis and blew off a bunch of deco). He's now partially blind and on permanent disability. In the last ~7yrs.
I wouldn't know how many quit (at least a few I'm aware of), other than the disabled guy who enjoyed his solo narcosis dives, most of the local deep air folks are not contributors to boards like this. They tend to do the same shore site repeatedly, but may or may not have any deco training at all.
Michael Thornton
Rebreather Enthusiast
I just moved something on my desk and found an old BSAC '88 Tables Dive Conduct Slate, for non-UK divers its a plastic square with the bare minimum amount of Decompression tables on the back for just-in-case scenario, you are supposed to write your dive plan on the front and 3 alternates- Longer, Deeper and Worse case, its actually a brilliant little thing.
What piqued my interest was a couple of weeks ago we dived a 45mtr wreck and despite the majority of the boat being on CCR or Nitrox no-one did much more than 25min BT and all did considerable, multiple stops... These old tables only give 1@9 and 6@6 for such a dive- on AIR!
Has made me wonder if the modern cautious, deep stop filled, mixed gas capable all-singing computers have made the current divers a bit nervous/careful. I see people using heavy GF's on bailout slates for pity's sake- not to mention doing many minutes of deco on dives well above 40mtrs.
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?
Sorry I am late to the thread. I have had a busy couple weeks and couldn't catch up with all the posts. Are less or more people getting bent these days? It's hard to tell. There are more tech divers now and it is easy to hear of their stories of being bent with Internet and forums it may seem like more are being bent but it could be the opposite.
Are the cases of bends increasing or is the reporting of them just getting better?
With the ratios of how someone's physiology can sway presented in this thread how far under the limit do you think we should stay?
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