Info Deeply Safe Labs: A website for dive computer testing

[tursiops]

@cerich you still haven't answered my question.

And you have not answered my question in post #8.

 

[Duke Dive Medicine]

Experimental dives and statistics (DAN, BSAC) confirm a higher risk of decompression sickness for repetitive dives. Microbubbles in the venous blood obstructing a part of the lung capillaries produce ventilation-perfusion trouble, a right-left shunt well known in lung physiology. The arterial nitrogen pressure is for a few hours distinctly higher than the nitrogen pressure in the inspired air. Therefore the nitrogen elimination by respiration is retarded.

Point of clarification for readers here based mostly on my own failure to thoroughly read @Deeply Safe Labs ' post #16. The right-to-left shunt described here is different than a right-to-left shunt that allows venous gas emboli to arterialize. This is an important distinction to make. What is described above is a type of ventilation-perfusion (VQ) mismatch (likely what @cerich was thinking when he initially responded to this post - @cerich, my own misinterpretation, apologies).

VERY mild VQ mismatch, aka shunting, could possibly occur if venous gas emboli (a normal occurrence on many dives) partially obstruct blood flow through the pulmonary capillaries. Pulmonary DCS is the extreme end of this. In this case, it's blood that's being shunted, not bubbles. @Deeply Safe Labs mentioned Dr. Buhlmann's assertion that this can theoretically impair off-gasing since some blood is not passing by alveoli, and that some deco models do not take this into account. Bubbles trapped in the pulmonary capillary bed on the pulmonary arterial side are dynamic - they are reduced in size due to the partial pressure gradient between the bubble, the surrounding blood, and the alveoli in close proximity. People with more knowledge than I have on the subject may be able to weigh in on whether this phenomenon can be isolated in the context of a decompression model. @Dr Simon Mitchell ?

A right-to-left shunt that allows bubbles to pass through to the arterial circulation is shunting bubbles (and to a certain extent blood as well, since it doesn't pass by the alveoli). This is where PFO and other cardiac septal defects come in, along with the intrapulmonary shunt in @Johnoly 's diagram.

Best regards,
DDM

 

[kierentec]

Am I the only one expecting a PDF of the most revolutionary dive computer every to be dropped in the near future? Is “deeply safe” a spin-off of OSEL?

 

[tursiops]

Am I the only one expecting a PDF of the most revolutionary dive computer every to be dropped in the near future? Is “deeply safe” a spin-off of OSEL?

You mean a computer that takes care of me, whether or not I want it or need it? Don't we already have some of those, and mostly distrust and dislike them?

 

[dmaziuk]

@Deeply Safe Labs is asserting that this can theoretically impair off-gasing since some blood is not passing by alveoli, and that some deco models do not take this into account. Bubbles trapped in the pulmonary capillary bed on the pulmonary arterial side are dynamic - they are reduced in size due to the partial pressure gradient between the bubble, the surrounding blood, and the alveoli in close proximity. People with more knowledge than I have on the subject may be able to weigh in on whether this phenomenon can be isolated in the context of a decompression model.

You'd have to have a model that models physiology to begin with.

M-values are derived from statistics. If the sample they are derived from is representative of the population as a whole (as it seems to be), then they do account for 25% chance of PFO, shunts, the fact that some people have a lot of bubbles some or all of the time, and so on.

 

[Deeply Safe Labs]

@Deeply Safe Labs is asserting that this can theoretically impair off-gasing since some blood is not passing by alveoli

Deeply Safe Labs is not asserting such a thing. Pr. Bühlmann is:

https://www.uhms.org/archived-publications1/workshops/the-effectiveness-of-dive-computers-in-repetitive-diving.html

Pages 11 to 18.

Tauchmedizin

link.springer.com

Section 6.6, pages 119 to 125.

Yes, these references are old. I fail to understand how that makes them invalid. Unless there is some more recent study showing otherwise, they still are valid.

Now, let's read again post #1:

Some of them simply confirmed that absence of additionnal procedures, without bringing any argument to why they are not taking into account aggravating factors, like the right-left pulmonary shunt.

You will notice that we mentioned this pulmonary shunt as just one example of the aggravating factors that require a specific procedure to compute decompression for repetitive dives. There are others factors that must be considered. The use of "must" is intentional, and again, this is not an assertion from Deeply Safe Labs:

Dr. Alf O. Brubakk (SINTEF, Trondheim, Norway): Two points to make on that. First of all, you do not need any gas bubbles at all to have asymmetry. An example is a saturation dive. It is quite easy to calculate. In a non-saturation dive the lower compartment tensions as you decompress, in relation to compressing, will give you quite a substantial asymmetry. So, one of the points about this repetitive diving is that if you do not take into account the asymmetry that is caused simply by the gas tensions, then you run into trouble. [...]

Source: https://www.uhms.org/archived-publi...s-of-dive-computers-in-repetitive-diving.html , page 17

@cerich

You still haven't the question explicitly. You pretend to love debating and learning, still you keep your cards close to your chest. That is not very scientific.

Now, you seem to be unconvinced, you pretend that it is the case of multiple people that "know this subject well". You should probably take a look at the discussion that followed the 1994 UHMS workshop, as it is included at the end of the article:

Anyway, let's play your game. Which dive computer might you be talking about?

Is it the Shearwater Perdix 2? Because here is what the manual states:

The Shearwater Perdix 2 is a dive computer for beginner to expert divers.

Shearwater Perdix 2, Recreational Modes Operating Instructions, page 4, https://www.shearwater.com/wp-content/uploads/2022/05/Perdix-2_RECREATIONAL_Manual_RevC.pdf

Is it the Shearwater Petrel 3? Because here is what the manual states:

The Shearwater Petrel 3 is a dive computer for beginner to expert divers.

Shearwater Petrel 3, Recreational Modes Operating Instructions, page 4, https://www.shearwater.com/wp-content/uploads/2022/05/Petrel-3_RECREATIONAL_Manual_RevC.pdf

Is it the OSTC 2? Nothing in the manual states any limit of use. They even seem to say that the computer is fully able to compute decompression for repetitive dives:

Take OSTC2 with you on every repeat dive – don’t lend it to anyone.

A correct calculation of tissue saturation requires that OSTC2
• is configured correctly
• is used on every dive
• is only used to record data during your own dives (and not shared with other divers)

OSTC2 Owner's Manual, page 10, http://heinrichsweikamp.com/media/wysiwyg/OSTC2_EN_web.pdf

Is it the Mares Sirius? The manual does not state any limit of use. Here is what the product description says:

The recreational diver can see dive data in a simple, intuitive way, with the possibility of integrating tank data using the optional tank module. The Extended Range diver can insert up to five nitrox and trimix mixes.

Sirius watch-style dive computer | Mares

Mares designed the watch-style Sirius dive computer with the aim of perfectly combining technology and elegance. The characteristics of this dive computer feature top-of-the-range technology, both for the recreational and Extended Range diver. Buy now on

www.mares.com

Now, which one is it? With computers that can be used both by recreational and technical divers, how exactly are we outside of their intended use scope with our tests?

If you wish to join the team, I would be very happy to recieve your resume.

Best regards,
Eric Frasquet,
Deeply Safe Labs.

 

[lexvil]

I know everyone loves to play with their big deco brains BUT wasn’t the op just showing what some computers do in repetitive dive testing? Why has it dissolved into a Johnson waving contest?

 

[Duke Dive Medicine]

Deeply Safe Labs is not asserting such a thing. Pr. Bühlmann is:

https://www.uhms.org/archived-publications1/workshops/the-effectiveness-of-dive-computers-in-repetitive-diving.html

Pages 11 to 18.





You will notice that we mentioned this pulmonary shunt as just one example of the aggravating factors that require a specific procedure to compute decompression for repetitive dives. There are others factors that must be considered. The use of "must" is intentional, and again, this is not an assertion from Deeply Safe Labs:

I stand corrected on the source. That said, I don't know that it would be possible to quantify the effect with any accuracy since the quantity of venous gas emboli varies so much from diver to diver, and from dive to dive in the same diver.

Best regards,
DDM

 

[cerich]

Deeply Safe Labs is not asserting such a thing. Pr. Bühlmann is:

https://www.uhms.org/archived-publications1/workshops/the-effectiveness-of-dive-computers-in-repetitive-diving.html

Pages 11 to 18.

He also in same period was terribly excited about a new UWATEC computer he was involved in (page 12 where he says that he validated it.. poorly obviously), that bent divers and became a very expensive lawsuit for UWATEC. He was a true innovator, brilliant person who added much to our understanding and dive safety, however he wasn't always right. In some ways, this paper is a pitch for it..just saying.

But, I haven't read it for at least 20 years (but did a bunch of times back in the day, for reasons) and while I am pretty sure I recall the gist, I shall refresh myself. Reading and poorly filtered thoughts incoming (see what I did there?)

Again, and last time, regards pulmonary shunting, he specifically used right-left, repeatedly and no shunting in the lungs that I have been able to find , and the actual structure of the lungs doesn't support that there is any such thing regards shunting occurring right-left. yeah, guess i am arrogant enough to assert that his use of right-left in this context was wrong. Now, there is enough else there to give an idea of where he is going, and certainly the computer I alluded to was an early attempt regards better consideration for micro bubble formations, but micro bubble considerations and understanding aren't (and weren't) exclusive to the lungs. His comments regarding right left shunting in lungs causing blood (with microbubbles) to bypass the lungs (via the mythical right left in the lungs shunt) and join the party in the muscles and dermas where they wreck the place is an interesting theory but, yeah no, it doesn't hold up, and as discussed in this thread, there is better understanding now . For the degree of shunting to occur via pulmonary shunting to cause real issues would require enough lung damage that you would have what the professionals call a patient or victim, not someone that is doing 5-6 repetitive dives that day to invite the whole world to join the hypothetical pulmonary shunted micro bubble party and rave.

By the way, did his recounting of using altitude dives and applying this theory of his not raise any alarms? It should have, it does for me, because for folks that live at lower altitudes, then going higher, I would consider the stage being set for there being a higher likelihood of pulmonary shunting (not left right because that is BS however). That whole how altitude impacts folks is well researched, just saying (hint 18 hours is not even close to enough to acclimatize). He is a crappy American university article on that , but you may not care because these folks don't even hire gardeners that know how to get vines off of buildings Princeton

I am curious to what research ethics panel/committee that whole mountain diving adventure went thru however. For reasons...

Regardless of all the above, we KNOW that the computer he was using was fatally flawed, and this entire article/paper/sale pitch via "academia" is suspect on that alone, the mysterious and non existent right left pulmonary shunt hooligan notwithstanding. Oh, and the alleged extrapolations for skin temp based on water temperature is beyond silly, whatever math he decided on is a SWAG, also, I don't think that using tank pressure to modify the algorithm in real time was very smart at all. That someone is breathing faster is not by itself indictive of faster absorption of gas . He associated higher breathing with exertion (logical in ways) but, yeah, not exclusively at all when we are talking recreational divers, and higher respiration without higher exertion isn't gonna to mean more on or off gassing to a level of concern sans other factors. Because physics.

Anyhow.. you have decided 30 years later that his sales pitch for his new product that was poorly tested and implemented and recalled after grievously harming divers is a solid basis to say that there is this massive safety issue with current computers.(irony here that that was kinda exactly what he was doing to get the world to flock to the new computer he was involved in, thank god it didn't happen.) You also seem to take everything in this whatever it is as gospel, and understanding of the subject beyond a very superficial manner indeed should be shooting red flags into the sky like Russia doing a massive "exercise" on your borders should.

As I have been writing notes as I refresh myself reading that sales pitch, I laughed out loud at Powell's comments on page 17, that is worth reading and considering, just saying. Yeah, when there are enough to be a problem, it's already killing, you don't need to adjust the algorithm, you need to call a priest for last rites.

Brubakk ( a smart guy that hasn't gotten the spot light like he should have), his comments seem to suggest that he interpreted the right left pulmonary shunting as actually being being asymmetrical, THAT actually starts to make sense versus using left right which is ..again BS. I think he was being the gentleman and nudging a correction.

Peterson confirms that the temp issue I addressed above is indeed, a SWAG (as defined in the link above) , the answer to Peterson is.. telling.

Tauchmedizin

link.springer.com

Section 6.6, pages 119 to 125.

Yes, these references are old. I fail to understand how that makes them invalid. Unless there is some more recent study showing otherwise, they still are valid.

Now, let's read again post #1:



You will notice that we mentioned this pulmonary shunt as just one example of the aggravating factors that require a specific procedure to compute decompression for repetitive dives. There are others factors that must be considered. The use of "must" is intentional, and again, this is not an assertion from Deeply Safe Labs:


Source: https://www.uhms.org/archived-publi...s-of-dive-computers-in-repetitive-diving.html , page 17

@cerich

You still haven't the question explicitly. You pretend to love debating and learning, still you keep your cards close to your chest. That is not very scientific.

Now, you seem to be unconvinced, you pretend that it is the case of multiple people that "know this subject well". You should probably take a look at the discussion that followed the 1994 UHMS workshop, as it is included at the end of the article:

I did, and my run and gun commentary as I read it again above addresses, and commentary then by other experts supports.

Anyway, let's play your game. Which dive computer might you be talking about?

Is it the Shearwater Perdix 2? Because here is what the manual states:



Shearwater Perdix 2, Recreational Modes Operating Instructions, page 4, https://www.shearwater.com/wp-content/uploads/2022/05/Perdix-2_RECREATIONAL_Manual_RevC.pdf

Is it the Shearwater Petrel 3? Because here is what the manual states:



Shearwater Petrel 3, Recreational Modes Operating Instructions, page 4, https://www.shearwater.com/wp-content/uploads/2022/05/Petrel-3_RECREATIONAL_Manual_RevC.pdf

Is it the OSTC 2? Nothing in the manual states any limit of use. They even seem to say that the computer is fully able to compute decompression for repetitive dives:



OSTC2 Owner's Manual, page 10, http://heinrichsweikamp.com/media/wysiwyg/OSTC2_EN_web.pdf

Is it the Mares Sirius? The manual does not state any limit of use. Here is what the product description says:

Sirius watch-style dive computer | Mares

Mares designed the watch-style Sirius dive computer with the aim of perfectly combining technology and elegance. The characteristics of this dive computer feature top-of-the-range technology, both for the recreational and Extended Range diver. Buy now on

www.mares.com

Now, which one is it? With computers that can be used both by recreational and technical divers, how exactly are we outside of their intended use scope with our tests?

Glad you are starting to look more closely.

If you wish to join the team, I would be very happy to recieve your resume.

I don't have one, I haven't needed one in a couple decades. Here is my Linkedin, it's sparse but kinda covers things. I don't list consulting stuff for reasons. I am not a scientist, nor MD etc. Just someone that has been following this for 3 and a half decades or so and in the industry for 3 (decades). I have done some diving, some product design and lots of pot stirring (in the literal and figurative manner actually.)

Any team stuff and we need to establish a very clear conflict of interest statement, and would expect disclosure from the entire team, whomever they are.

https://www.linkedin.com/in/christopher-e-richardson-mba-75561345/

Best regards,
Eric Frasquet,
Deeply Safe Labs.

 

[cerich]

I knoweveryone loves to play with their bib deco brains BUT wasn’t the op just showing what some computers do in repetitive dive testing? Why has it dissolved into a Johnson waving contest?

It's online, it's a thing