Info Deeply Safe Labs: A website for dive computer testing

[Deeply Safe Labs]

Sacrilege has been committed! Now waiting to witness the blowback (incl. but not limited to poking holes into the testing methodology, etc., etc.,).

Not an expert on algorithms - but the page “guide to interpreting results” has some interesting and agreeable viewpoints that meet my own personal confirmation bias - as I had watched all the video interviews of Dr. Bruce about the RGBM model before I got the Suunto and decided to risk the stupid lockout mode of their DCs.

Hi @Pearlman ,

Thank you very much for your positive feedback.

We are indeed expecting the blowback. Let me predict some of the arguments that have not yet been brought fourth but might:

• What tells us that computers that "handle" repetitive dives don't do so with a "guessgorithm", completely out of touch with what actually happens physiologically?
• Is it better to spend 15 more minutes of stops or 15 minutes at rest, at the surface, being dry?
• If some computers were widowmakers, we would have heard about it already.
• Anyway the double dive profile can't be done because of the amount of gas required
• These profiles are intrinsincly dangerous, absolutely nothing can be concluded from them!

We find it very interesting how a conflict of interest can push someone to make the most out of touch comments.

I think it it is reasonable to assume good intent on the part of the OP and make allowances for English likely being a second language. There are some fine scientific minds on SB, and with that comes the opportunity to share feedback in a constructive manner.

Best regards,
DDM

Hi @Duke Dive Medicine ,

Thank you very much for your valuable input. This is the exact reason why we came forth on Scubaboard. The Deeply Safe Labs website does not aim to be a scientific paper, but rather a way for anyone to better understand computers behaviour based on reproductible and factual data. Unfortunately, we are French, so english is not our mother thongue.

Best regards,
The Deeply Safe Labs Team.

 

[cerich]

I think it it is reasonable to assume good intent on the part of the OP and make allowances for English likely being a second language. There are some fine scientific minds on SB, and with that comes the opportunity to share feedback in a constructive manner.

Best regards,
DDM

sure, but like him, having been involved in dive computers at the manufs level, I know that a LOT of thought goes into it, and the intended use for the computer is an important factor in implementation decisions. Much of what he is doing is going WELL outside the design use case for many units and ignoring what the actual manuals say. His argument that it's a valid means to test/expose is.. wrong. There are many good reasons why that is, some algorithm, some programming, some hardware, and some design decisions. But, push some units far past design envelope and if the manuf didn't choose to just lock them out, you will see..exactly what he found. Is the problem the computer or the user not using as designed? If I try and do all the aerobatics in a Cessna 150 that a 150 aerobat can do, when the wings fold on me it's my fault, no matter how much I scream on the way down "BUT OTHER CESSNA 150's CAN DO IT, why didn't this one?"

I'm ok with him doing that, IF he CLEARLY annotated with what the manufs recommended use for the unit was, and any specific things regards settings from the manuals. Plus, having like you read many, many papers on deco, some of what he is claiming is.. cherry picking at best and some is just wrong. So, supply references or don't make unsupported claims.

 

[cerich]

Thank you very much for your valuable input. This is the exact reason why we came forth on Scubaboard. The Deeply Safe Labs website does not aim to be a scientific paper, but rather a way for anyone to better understand computers behaviour based on reproductible and factual data. Unfortunately, we are French, so english is not our mother thongue.

Best regards,
The Deeply Safe Labs Team.

Salut!

Si l'utilisation de l'anglais pose des problèmes, puis-je vous suggérer d'écrire en français, s'il vous plaît ?

Même si je suis anglo-canadien et que mon français est médiocre, même pour les normes canadiennes , il vaudrait peut-être mieux éviter tout malentendu.

Je dirais que lorsque l’on parle d’un sujet scientifique et théorique par nature, fournir des références n’est que responsable, d’autant plus que vous essayez de sensibiliser à ce que vous considérez comme un problème de sécurité grave et critique

Merci

 

[lowwall]

Salut!

Si l'utilisation de l'anglais pose des problèmes, puis-je vous suggérer d'écrire en français, s'il vous plaît ?

Touché.

 

[cerich]

Hi @lowwall ,

without bringing any argument to why they are not taking into account aggravating factors, like the right-left pulmonary shunt.



Best regards,
Eric Frasquet,
Deeply Safe Labs.

Salut Eric,
Pourquoi pensez-vous que les ordinateurs devraient prendre en compte des facteurs physiologiques tels qu'un shunt droite-gauche ?

Certes, un shunt est un facteur de risque supplémentaire de DCS (Peppas et al, 2023), mais c'est aussi un problème physiologique présent chez environ 25 % de la population générale. Pourquoi est-ce que c'est aux fabricants d'ordinateurs de tenir compte de l'aptitude à la plongée plutôt qu'à l'aspect médical ?

L'industrie de la plongée ne veut pas exclure un quart de sa base de consommateurs potentiels, mais Peppas et al soulignent certainement que le shunt droite-gauche est bien trop bien représenté chez ceux qui obtiennent le DCS. Cela me semble plus préoccupant que les choix de conception faits dans les ordinateurs de plongée qui se rapportent à l'utilisation conçue et prévue. Ne tient pas compte des facteurs aggravants (il existe bien plus qu’un simple shunt droite gauche à des degrés divers). Le problème vient donc des ordinateurs de plongée, ou d'une industrie, y compris des organisations qui ont codifié les examens médicaux de plongée pour la plongée récréative (RSTC, UHMS et DAN), qui savent qu'un shunt droit-gauche peut constituer un risque grave (RSTC Medical, instructions au médecin, 2020), mais ne nécessite-t-il pas de tests pour exclure ?

Ma préoccupation est que l'extrapolation de tous les facteurs susceptibles d'augmenter le risque pour un plongeur dans la conception d'un ordinateur aboutirait à un ordinateur de plongée qui conseille "Ne plongez pas". Après tout, mis à part les problèmes physiologiques, la visibilité de l’eau, la température, l’expérience, le poids, etc. sont tous des facteurs bien établis qui contribuent à de mauvais résultats. Bien qu'en théorie, vous puissiez concevoir un ordinateur de plongée pour mesurer et prendre en compte tous ces éléments (avec des capteurs appropriés, une saisie utilisateur et une capacité de calcul), il semble beaucoup d'efforts pour proposer "Ne plongez pas".

 

[Deeply Safe Labs]

Hi @cerich ,

Votre Français n'est pas si médiocre.

However, with some consideration to the other users of this forum, let's keep this in English. Our writing may not be perfect, but it is good enough to avoid any missunderstanding. If we have trouble understanding someone, we would be asking questions anyway. There is no need to worry on this side.

Salut Eric,
Pourquoi pensez-vous que les ordinateurs devraient prendre en compte des facteurs physiologiques tels qu'un shunt droite-gauche ?

Certes, un shunt est un facteur de risque supplémentaire de DCS (Peppas et al, 2023), mais c'est aussi un problème physiologique présent chez environ 25 % de la population générale. Pourquoi est-ce que c'est aux fabricants d'ordinateurs de tenir compte de l'aptitude à la plongée plutôt qu'à l'aspect médical ?

L'industrie de la plongée ne veut pas exclure un quart de sa base de consommateurs potentiels, mais Peppas et al soulignent certainement que le shunt droite-gauche est bien trop bien représenté chez ceux qui obtiennent le DCS. Cela me semble plus préoccupant que les choix de conception faits dans les ordinateurs de plongée qui se rapportent à l'utilisation conçue et prévue. Ne tient pas compte des facteurs aggravants (il existe bien plus qu’un simple shunt droite gauche à des degrés divers). Le problème vient donc des ordinateurs de plongée, ou d'une industrie, y compris des organisations qui ont codifié les examens médicaux de plongée pour la plongée récréative (RSTC, UHMS et DAN), qui savent qu'un shunt droit-gauche peut constituer un risque grave (RSTC Medical, instructions au médecin, 2020), mais ne nécessite-t-il pas de tests pour exclure ?

Ma préoccupation est que l'extrapolation de tous les facteurs susceptibles d'augmenter le risque pour un plongeur dans la conception d'un ordinateur aboutirait à un ordinateur de plongée qui conseille "Ne plongez pas". Après tout, mis à part les problèmes physiologiques, la visibilité de l’eau, la température, l’expérience, le poids, etc. sont tous des facteurs bien établis qui contribuent à de mauvais résultats. Bien qu'en théorie, vous puissiez concevoir un ordinateur de plongée pour mesurer et prendre en compte tous ces éléments (avec des capteurs appropriés, une saisie utilisateur et une capacité de calcul), il semble beaucoup d'efforts pour proposer "Ne plongez pas".


View attachment 833564

Are you refering to the article named "Right-to-Left Shunt in Divers with Neurological Decompression Sickness: A Systematic Review and Meta-Analysis"?

There seem to be some kind of missunderstanding here. This study focuses on the patent foramen ovale (PFO), as one of the contributing factors to what is generally refered as right to left shunt (RLS). I suppose that is why you mention 25% of the population, but the article clearly talks only about PFO:

[...] PFO is common in the general population, with an estimated prevalence of 25–30%.

What we are talking about is specifically the right-left pulmonary shunt, which is described briefly in the introduction of the article you mention:

[...] the supersaturation of tissues with dissolved gas that overwhelms pulmonary filtration capacity [...]

You are asking why we believe this right-left pulmonary shunt should be accounted for in dive computers. What we do or don't believe does not matter. What seems more important is what Pr. A. A. Bühlmann wrote:

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.

The algorithm ZH-L8 ADT takes into consideration this risk in extreme repetitive dives [...]

The algorithm ZH-L8 ADT is not only a needed modification, it is an essential improvement.

Source: Albert A. Bühlmann, Behavior of dive computer algorithms in repetitive dives : experience and needed modifications, in Hamilton R.W. edition, UHMS Workshop 81, 6-1-1994, Undersea and Hyperbaric Medical Society.

sure, but like him, having been involved in dive computers at the manufs level, I know that a LOT of thought goes into it, and the intended use for the computer is an important factor in implementation decisions. Much of what he is doing is going WELL outside the design use case for many units and ignoring what the actual manuals say. His argument that it's a valid means to test/expose is.. wrong. There are many good reasons why that is, some algorithm, some programming, some hardware, and some design decisions. But, push some units far past design envelope and if the manuf didn't choose to just lock them out, you will see..exactly what he found. Is the problem the computer or the user not using as designed? If I try and do all the aerobatics in a Cessna 150 that a 150 aerobat can do, when the wings fold on me it's my fault, no matter how much I scream on the way down "BUT OTHER CESSNA 150's CAN DO IT, why didn't this one?"

I'm ok with him doing that, IF he CLEARLY annotated with what the manufs recommended use for the unit was, and any specific things regards settings from the manuals. Plus, having like you read many, many papers on deco, some of what he is claiming is.. cherry picking at best and some is just wrong. So, supply references or don't make unsupported claims.

I have trouble understanding how the lack of source invalidates our claims. Let me take an example, with this conference:


At 15:00, @Dr Simon Mitchell talks about the inverse correlation between decompression time and DCS risk, however he never gives any source to back that up. Does that mean that Dr Mitchell is not a scientist? Does that mean that his claim is wrong? I don't think so, it probably just means that he is simplifying his speech for the sake of his audience.

Now, let's be constructive and leave these petty arguments behind us. You seem to disagree with us, and that's fine, but please make your point clearly:
Which claims exactly are you denying? Why?
Do you have a specific example of a computer that, in its manual, makes a mention of a scope of use that we would have breached?

Best regards,
Eric Frasquet,
Deeply Safe Labs.

Edit:

There seems to be a problem with embedding the youtube video. Here's a direct link:

https://www.youtube.com/live/jR0Fu20zlYQ?si=fo-K0X2OiaPVy0F0&t=900

 

[cerich]

Hi @cerich ,

Votre Français n'est pas si médiocre.

However, with some consideration to the other users of this forum, let's keep this in English. Our writing may not be perfect, but it is good enough to avoid any missunderstanding. If we have trouble understanding someone, we would be asking questions anyway. There is no need to worry on this side.



Are you refering to the article named "Right-to-Left Shunt in Divers with Neurological Decompression Sickness: A Systematic Review and Meta-Analysis"?

Yes

There seem to be some kind of missunderstanding here. This study focuses on the patent foramen ovale (PFO), as one of the contributing factors to what is generally refered as right to left shunt (RLS). I suppose that is why you mention 25% of the population, but the article clearly talks only about PFO:

Hmmm..... the paper uses the term "shunt" a lot, in context of PFO

What we are talking about is specifically the right-left pulmonary shunt, which is described briefly in the introduction of the article you mention:

Where specifically? Both me and "ctl F" are missing finding a specific use of the term "pulmonary shunt". In fact, the right-left shunts refers to something that happens in the heart, most commonly by far a PFO. Unless I am reading you wrong, you seem to think that right-left shunting occurs in the lungs based on his comment??? "Right left" is REALLY important.. to the heart. Pulmonary shunting such as in ARDS isn't gonna be exclusively right left, left right, up down or down up, it could be all of that or some of that.

You are asking why we believe this right-left pulmonary shunt should be accounted for in dive computers. What we do or don't believe does not matter. What seems more important is what Pr. A. A. Bühlmann wrote:







Source: Albert A. Bühlmann, Behavior of dive computer algorithms in repetitive dives : experience and needed modifications, in Hamilton R.W. edition, UHMS Workshop 81, 6-1-1994, Undersea and Hyperbaric Medical Society.



https://www.youtube.com/live/jR0Fu20zlYQ?si=fo-K0X2OiaPVy0F0&t=900

OK, this is when using sources is handy, you have quoted Bühlmann, are you sure you are correct in your understanding? Other than PFO or some physical damage/defect to the heart, by what mechanism is right left shunting occurring? I don't read that comment by him to infer that there is any right-left shunting occurring in the lungs.. umm because it makes no sense. Micro bubbles interfering with perfusion in the alveolar/pulmonary capillaries does. I believe he was mentioning the right-left shunt because it is quarter of folks (PFO) and in them, they are more likely to have unfiltered microbubble lodge there. Honestly, beyond PFO and right left shunting I can think of other reasons for there to be reduced efficiency of perfusion (like inflammation, variety of potential causes, some specific to diving).

These should help you understand

Physiology, Pulmonary Ventilation and Perfusion

Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches


Some other papers that help paint a bigger picture

Decompression Illness in Repetitive Breath-Hold Diving: Why Ischemic Lesions Involve the Brain?



Risk mitigation in divers with persistent (patent) foramen ovale

Increased Risk of Decompression Sickness When Diving With a Right-to-Left Shunt: Results of a Prospective Single-Blinded Observational Study (The “Carotid Doppler” Study)

Relationship between right-to-left shunts and cutaneous decompression illness

and of course the paper we have both mentioned for those that don't know what we are talking about

Right-to-Left Shunt in Divers with Neurological Decompression Sickness: A Systematic Review and Meta-Analysis


Now, can shunting occur in the lungs? Yes. In folks with ARDS, but while there is some insight in looking at that situation, for diving you would have to be talking about massive bubbling from severe DCS or fluid from IPE etc., I can't see microbubbles from those with right left shunting causing this in any measurable amount within the context of dive computers accounting for. I mean, for that we are talking BENT very badly, with all the ancillary crisis things that come with for treatment(when I leave as chamber attendant and a person with MD, possibly a hyperbaric and emergency medicine trained PA enters as chamber attendant) I can see IPE however giving folks a nice dose of it. In fact, I can see IPE and right left shunting combined as being a real PITA in certain circumstances.

Pathophysiology and Clinical Meaning of Ventilation-Perfusion Mismatch in the Acute Respiratory Distress Syndrome

 

[lowwall]

Hmmm..... the paper uses the term "shunt" a lot, in context of PFO

Where specifically? Both me and "ctl F" are missing finding a specific use of the term "pulmonary shunt". In fact, the right-left shunts refers to something that happens in the lung, most commonly by far a PFO.

I believe the text in bold was made in error. It should read "heart", not "lung".

As cerich was saying in the rest of the post, the term shunting in the context of DCS is about bubbles moving from the venous to arterial side of the heart in divers with a PFO.

 

[cerich]

I believe the text in bold was made in error. It should read "heart", not "lung".

As cerich was saying in the rest of the post, the term shunting in the context of DCS is about bubbles moving from the venous to arterial side of the heart in divers with a PFO.

it was, thanks and fixed.

 

[duke dive medicine]

Yes

Hmmm..... the paper uses the term "shunt" a lot, in context of PFO

Where specifically? Both me and "ctl F" are missing finding a specific use of the term "pulmonary shunt". In fact, the right-left shunts refers to something that happens in the heart, most commonly by far a PFO. Unless I am reading you wrong, you seem to think that right-left shunting occurs in the lungs based on his comment??? "Right left" is REALLY important.. to the heart. Pulmonary shunting such as in ARDS isn't gonna be exclusively right left, left right, up down or down up, it could be all of that or some of that.

OK, this is when using sources is handy, you have quoted Bühlmann, are you sure you are correct in your understanding? Other than PFO or some physical damage/defect to the heart, by what mechanism is right left shunting occurring? I don't read that comment by him to infer that there is any right-left shunting occurring in the lungs.. umm because it makes no sense. Micro bubbles interfering with perfusion in the alveolar/pulmonary capillaries does. I believe he was mentioning the right-left shunt because it is quarter of folks (PFO) and in them, they are more likely to have unfiltered microbubble lodge there. Honestly, beyond PFO and right left shunting I can think of other reasons for there to be reduced efficiency of perfusion (like inflammation, variety of potential causes, some specific to diving).

These should help you understand

Physiology, Pulmonary Ventilation and Perfusion

Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches


Some other papers that help paint a bigger picture

Decompression Illness in Repetitive Breath-Hold Diving: Why Ischemic Lesions Involve the Brain?



Risk mitigation in divers with persistent (patent) foramen ovale

Increased Risk of Decompression Sickness When Diving With a Right-to-Left Shunt: Results of a Prospective Single-Blinded Observational Study (The “Carotid Doppler” Study)

Relationship between right-to-left shunts and cutaneous decompression illness

and of course the paper we have both mentioned for those that don't know what we are talking about

Right-to-Left Shunt in Divers with Neurological Decompression Sickness: A Systematic Review and Meta-Analysis


Now, can shunting occur in the lungs? Yes. In folks with ARDS, but while there is some insight in looking at that situation, for diving you would have to be talking about massive bubbling from severe DCS or fluid from IPE etc., I can't see microbubbles from those with right left shunting causing this in any measurable amount within the context of dive computers accounting for. I mean, for that we are talking BENT very badly, with all the ancillary crisis things that come with for treatment(when I leave as chamber attendant and a person with MD, possibly a hyperbaric and emergency medicine trained PA enters as chamber attendant) I can see IPE however giving folks a nice dose of it. In fact, I can see IPE and right left shunting combined as being a real PITA in certain circumstances.

Pathophysiology and Clinical Meaning of Ventilation-Perfusion Mismatch in the Acute Respiratory Distress Syndrome

You may be referring to intrapulmonary shunting in the sense of blood in pulmonary capillaries bypassing non-functioning alveoli - your ARDS example is a good one. I would add that anatomic AV intrapulmonary shunts have been documented in healthy adults as well.

Intrapulmonary shunt during normoxic and hypoxic exercise in healthy humans - PubMed

This review presents evidence for the recruitment of intrapulmonary arteriovenous shunts (IPAVS) during exercise in normal healthy humans. Support for pre-capillary connections between the arterial and venous circulation in lungs of humans and animals have existed for over one-hundred years...

pubmed.ncbi.nlm.nih.gov

Clinical implications of pulmonary shunting on saline contrast echocardiography - PubMed

Pulmonary right-to-left shunting can be encountered using transthoracic contrast echocardiography (TTCE) with agitated saline. Diseases associated with pulmonary shunting on saline TTCE include hereditary hemorrhagic telangiectasia (HHT), hepatopulmonary syndrome, and some congenital heart...

pubmed.ncbi.nlm.nih.gov

https://journals.physiology.org/doi/full/10.1152/japplphysiol.00137.2004

https://journals.physiology.org/doi/full/10.1152/japplphysiol.00208.2007

Best regards,
DDM