This the paper he self-published in "World Divers"
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My summary of that paper: the DCIEM algorithm should be the gold standard for repetitive, mandatory stop diving and any computer using any other algorithm should state it is different from DCIEM. (Somehow, that seems obvious to me. If I wanted a DCIEM computer, I would have bought one.)
There is always a balance to be found between stop time and safety. If this had been submitted to a peer-reviewed journal, I'm quite certain it would have been rejected with the admonishment to incorporate data backing up the author's contention.
ETA: It was also strange that they evaluated computers using anything other than ZHL-16C-GF at their default conservatism, but somehow they didn't do that for those using it. Who does mandatory stop dives (repetitive or not) at 90/90?? It's certainly not the default conservatism setting for any computers with which I am familiar.
Well the quote in the paper is “ The fact that this default mode uses in most dive computers corresponds to GF 90/90 has been reported in 2021. 7”
Footnote 7 is
Rosenblat, Miri & Vered, Nurit & Salm, Albi. (2021). On the reliability of dive computer generated run-times, Part I. 10.13140/RG.2.2.16260.65929.
In which I see no reference to GF 90/90
Mozzz
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@cerich
Since the beginning of this thread, I have been trying to give you hints that I saw through your game. It does not seem that you understand my gentle hints that you are not fooling us. You are leaving me with no choice but to write this message.
Your arguments are obviously biased.
Your first message on this thread (#5) suggests that we would present fake data. All of our tests are accompanied with pictures at different points in the test protocols. You can cross reference any information we display using these pictures to match dive time, depth, stop time, TAT, even time of the day for the models that display it in dive mode. It would be doable to spot an error in our data, and quite easy to demonstrate that it is an error. Yet, when @Peralman asks you for some pointers about which data is fake, you remain silent, and have not brought the subject back on since. This visibly looks like an unsupported claim. You can of course prove me wrong by giving one single specific example of such fake data.
In messages #12, #24 and #30, you have been saying that our tests are out of scope for the intended use case of some dive computers, without ever bringing any proof to support your statement. I have asked for this multiple times, yet you do not deliver. I took it a step further, doing it your way, quoting manuals to support our claim that we are indeed in the intended scope. You have not denied these proofs, neither have you brought evidence that you were asked for in your response message, #39. We have reviewed the computers we tested and never have we found any mention saying that we were out of the intended use scope, in manuals, websites or any communication from manufacturers. You can of course prove me wrong by giving one specific quote from a manual that supports your claims.
You keep cherry picking on the fact that the "right-left shunt" term for the lungs makes no sense. I have tried to explain why such term is used, yet you don't seem to understand. I can understand that my explaining isn't perfect, but @Duke Dive Medicine explained it in a way that makes perfect sense in post #32. Yet, you still deny the words of Pr A. A. Bühlmann. You presented an argument to why you deny it in post #39, and this is where it gets interesting.
You are saying that the UWATEC lawsuit is Pr Bühlmann's fault. The recalled computer (CPSC, UWATEC AG Announce Recall of 1995 Aladin Air X NitrOx Dive Computers) is the Aladin Air X NitrOx, which was released more than a year after Pr Bühlmann passing away. The error was specific to nitrox diving (Did Uwatec conceal a known computer flaw?). The prototype computer that was tested for the UHMS workshop was the Aladin Air X, which didn't have nitrox capabilities. There is no way Pr Bühlmann could possibly identify the fault with the prototype he had then.
In conclusion, your arguments are not only biased, they are obviously selected and filtered to serve your purpose. You mention the Aladin Air X NitrOx lawsuit, because you can use it to serve your point, without specifying any of the details, which go against it.
I believe you are being emotional about the fact that we question ZH-L16 C implementations. You are Chief Diving Officer at Deep Six, which sells a dive watch, the Deep 6 Excursion Dive Computer. Remind me, what algorithm does it run again? If you are so doubtful about Pr Bühlmann's work, why do you sell a computer that uses his algorithm? There is obviously a conflict of interest here. You are the one in a conflict of interest.
Now that this is out of the way, I believe the situation is fit to answer the questions that actually serve the debate. Yet, this post is already long enough, so, to be continued.
Best regards,
Eric Frasquet,
Deeply Safe Labs.
Since the beginning of this thread, I have been trying to give you hints that I saw through your game. It does not seem that you understand my gentle hints that you are not fooling us. You are leaving me with no choice but to write this message.
Your arguments are obviously biased.
Your first message on this thread (#5) suggests that we would present fake data. All of our tests are accompanied with pictures at different points in the test protocols. You can cross reference any information we display using these pictures to match dive time, depth, stop time, TAT, even time of the day for the models that display it in dive mode. It would be doable to spot an error in our data, and quite easy to demonstrate that it is an error. Yet, when @Peralman asks you for some pointers about which data is fake, you remain silent, and have not brought the subject back on since. This visibly looks like an unsupported claim. You can of course prove me wrong by giving one single specific example of such fake data.
In messages #12, #24 and #30, you have been saying that our tests are out of scope for the intended use case of some dive computers, without ever bringing any proof to support your statement. I have asked for this multiple times, yet you do not deliver. I took it a step further, doing it your way, quoting manuals to support our claim that we are indeed in the intended scope. You have not denied these proofs, neither have you brought evidence that you were asked for in your response message, #39. We have reviewed the computers we tested and never have we found any mention saying that we were out of the intended use scope, in manuals, websites or any communication from manufacturers. You can of course prove me wrong by giving one specific quote from a manual that supports your claims.
You keep cherry picking on the fact that the "right-left shunt" term for the lungs makes no sense. I have tried to explain why such term is used, yet you don't seem to understand. I can understand that my explaining isn't perfect, but @Duke Dive Medicine explained it in a way that makes perfect sense in post #32. Yet, you still deny the words of Pr A. A. Bühlmann. You presented an argument to why you deny it in post #39, and this is where it gets interesting.
You are saying that the UWATEC lawsuit is Pr Bühlmann's fault. The recalled computer (CPSC, UWATEC AG Announce Recall of 1995 Aladin Air X NitrOx Dive Computers) is the Aladin Air X NitrOx, which was released more than a year after Pr Bühlmann passing away. The error was specific to nitrox diving (Did Uwatec conceal a known computer flaw?). The prototype computer that was tested for the UHMS workshop was the Aladin Air X, which didn't have nitrox capabilities. There is no way Pr Bühlmann could possibly identify the fault with the prototype he had then.
In conclusion, your arguments are not only biased, they are obviously selected and filtered to serve your purpose. You mention the Aladin Air X NitrOx lawsuit, because you can use it to serve your point, without specifying any of the details, which go against it.
I believe you are being emotional about the fact that we question ZH-L16 C implementations. You are Chief Diving Officer at Deep Six, which sells a dive watch, the Deep 6 Excursion Dive Computer. Remind me, what algorithm does it run again? If you are so doubtful about Pr Bühlmann's work, why do you sell a computer that uses his algorithm? There is obviously a conflict of interest here. You are the one in a conflict of interest.
Now that this is out of the way, I believe the situation is fit to answer the questions that actually serve the debate. Yet, this post is already long enough, so, to be continued.
Best regards,
Eric Frasquet,
Deeply Safe Labs.
No, I replied to someone else that was talking about RGBM and BW (who I knew) and he was who I was talking about regards RGBM. Your comprehension is poor. I NEVER said the results you got were fake.
Because digging into how BW started to slog about his invented dive history database to try and save RGBM when it started to fall apart would have just been a distraction from this.
Sigh, you are lacking reading comprehension and paranoid.
How about you do the work, it's your project and many have pointed out issues, you are choosing to ignore because you seem a zealot
Oh, let's cut the BS, you are WRONG about the right left pulmonary shunt in the lungs. A right left shunt is heart and it shunts/bypasses the lungs. You have been hanging your whole premise on that, and it's wrong. I have tried to point this out since the start and even went far too deep into talking about what shunting could occur in the lungs (and sure not right left) that actually is a nothing burger regards deco except in extremely fringe cases that nobody sane would use in a dive computer algorithm..
It was a team effort regards fault, and I recall it all very well. Given that you founded UWATEC and sold to Scubapro, and were well involved, are you really going to try and revise history? I don't know you personally, but do many of the folks involved with UWATEC in the states at the time (I am TDI #17), and followed it all pretty closely, especially when friends started to get well bent. I also had dove UWATEC since the go, and like many found myself with subclinical DCS when pushing it.
I am curious if this is all an effort by you to sort your legacy in the industry from that disaster while you still think you all went down the right path, but the fact the rest of the industry didn't follow that path is.. well, not exactly validation of your work. I mean, with so many of the folks you involved with you at the time of all this now dead, it does clear the way for you to do some legacy shaping, as those right there (primary sources) being dead aren't going to correct you.
Oh, none of this changes that you are also one hella innovator and did a LOT that should be admired as well. Like many humans, we sometimes innovate then when we think we have sorted it out, others come along and do derivative innovation in the blind spots for us. It's a thing, and that hits the ego (and wallet) for many people. Me, it just means up my game or admire what is new. Sometimes it annoys me for a second, then I remind myself that I have done the same, just at a different time, so get back at it.
I have been giving lots of information so as to help look at it holistically and foundational stuff, which eludes you obviously, so you throw I am biased. How about YOUR bias? Dude, I have NOTHING to gain by participating in this discussion, except hope that people don't fall for your very wrong conclusions.
Sigh, I never hid who i was, you didn't even look when I started to reply in this thread? That says something. Bühlmann made many iterations, I said very clearly he was brilliant and added to safety. Yeah, I think he went down wrong road for a bit in the early 90's, work since has built upon his earlier foundational work than the stuff he was doing at the end. When I said we would have to have a clear conflict of interest policy, you obviously took that to mean you.. that is silly, I meant everyone, including me. I can only speculate why that triggered you it seems, and be amused.
Dive safe, don't set 90/90, NOBODY thinks that is a good idea, except some dude screaming it's default when it isn't it seems
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Spending more time on decompression is generally safer than less time, but we’re always trying to balance Total Decompression Time (TDT) against the probability of DCS (pDCS).
What is the difference in the pDCS between DCIEM dive 2 and the various other algorithms for dive 2?
How much does the extra time reduce the risk? You’ve made several assertions that the current implementations are not safe, but you did so by presenting theories about why there should be a second dive penalty without providing, from my perspective, meaningful evidence that what we’re currently doing needs to change.
Hello,
This post raises a number of questions. It implies (though you don't state it definitively) that some of the computers you tested did "take account of aggravating factors". I would be curious to know what factors were taken into account by those computers?
There are many reasons why uptake and elimination of inert gas might be asymmetrical such as being warm during uptake and cold during elimination, or exercising during uptake and resting during elimination. I agree that these sorts of factors might come into play during a surface interval between dives.
The idea that "right-left pulmonary shunt" might be a factor is much less well established. For those who have become confused by the debate on this let me explain. Eric is arguing (or at least citing Buhlmann as suggesting) that venous bubbles passing to the lungs after a dive can impair gas exchange. They could do this by altering blood flow through the lung (we will return to this below). To understand this, think about how the lung works. It relies on well-ventilated alveoli (i.e., plenty of gas moving in and out of lung air sacs) being exposed to good blood flow through the network of capillaries that surround them. This balance between gas movement (ventilation) and blood flow (perfusion) to optimize gas exchange is referred to as the "ventilation-perfusion ratio".
It is easy to conceive how changes in ventilation or perfusion could disturb this. For example, imagine if there was no ventilation of an alveolus, but blood continued to pass through its surrounding capillaries. With no ventilation (gas movement) there will be no gas exchange, and so the incoming venous blood can pass that alveolus into the arteries without getting oxygenated (or eliminating nitrogen). This is sometimes referred to as 'shunt' (as Eric did) which has confused some divers on this thread who are more used to hearing this term in relation to problems like patent foramen ovale. In fact, the correct term where it is happening in the lungs is actually 'venous admixture'. Moreover, in most of the lung, things are not quite as black and white as in my example. Problems are more often a case of ventilation and perfusion not being perfectly matched rather than one or the other being totally absent. Either way, the net effect is a reduction in the efficiency of gas exchange.
So, returning to the debate about whether venous bubbles can cause ventilation-perfusion mismatch with a reduction of gas exchange efficiency and therefore a reduction of inert gas elimination between dives.... Yes, Buhlmann mentions it in the computer workshop proceedings, but he does not say how he knows it to be true. No references are cited. I do not have a translated copy of Tauchmedizin, so I don't know what he says in there.
The only definitive study of this phenomenon that I am aware of was published by the famous respiratory physiologist Michael Hlastala in 1979 [1] (attached). He and colleagues exposed anaesthetized dogs to venous gas (helium or nitrogen or sulphur hexafluoride) infused at 0.2ml/kg/min. This is a lot of gas - equivalent to 14ml / min in a 70 kg human. This is a level of venous gas embolisation that would not be seen in a human diver, and if it was I suspect it would be rapidly symptomatic. Despite this very high gas load the clearance of nitrogen in a single pass through the lung only fell from 96% to 93% over a 15-minute infusion of gas. Perhaps this result is not surprising given that venous bubbles tend to obstruct perfusion rather than reduce ventilation, and blood from obstructed vessels would tend to be 'diverted' through areas of the lung where flow remains less impaired thus maintaining gas exchange. Nevertheless, the usual efficiency of the lung would be impaired a little, hence the fall from 96 to 93%.
Bearing in mind that this was, in human terms, a massive gas infusion, I think it reasonable to conclude that in asymptomatic divers, venous bubbles arriving in the lungs during a surface interval are very unlikely to materially affect nitrogen elimination to produce the sort of asymmetry in gas uptake and elimination that Eric is talking about.
To answer @Duke Dive Medicine's question, even if between-dive VGE did reduce inert gas elimination, it is not clear to me (given the marked potential variability in bubbling even when the same profile is performed) how a computer would be able to take account of this unless it was interfaced in real time to a bubble counting device. In any event, it seems likely, based on the available evidence, that venous bubbling only exerts a minor / inconsequential effect on inert gas elimination.
Simon M
1. Hlastala M, et al. GAS EXCHANGE ABNORMALITIES PRODUCED BY VENOUS GAS EMBOLI. Respiration Physiology. 1979;36:1-17.
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