DECOMPRESSION CONTROVERSIES 

I'm from Panama City and I have a story for this: "The navy divers were falling over themselves [to participate in the NEDU study]" - My SCUBA instructor was a retired Navy Dive Instructor. He has a tattoo on his calf of a rat wearing SCUBA gear with the caption "Sat Rat." I asked about it and he said he was part of study that gave him the bends, and he and his fellow participants all got commemorative tattoos. I just realized - THIS was the study he participated in, the NEDU study. The Navy divers who participated in that were so proud of their courage (I'm proud of them too) that they went out and got tattoos! I'm proud to have trained with one. Also excellent work as always, Dr. Mitchell. Your talks are always as informative as they are entertaining.

Dr. Simon Mitchell is such a fantastic presenter and a treasured resource to us all. To have a renowned and leading expert in hyperbaric medicine who is also an experienced and avid diver himself is valuable beyond measure to the entire diving community. This video is so incredibly useful, from building a basic knowledge of decompression theory to going into recent advances in our physiological understanding. It's all here. A well put-together presentation that is truly useful to all skill levels and experiences. Thank you sir!

I don't dive and don't ever want to, and this was FASCINATING. I love this kind of in-depth analysis of life-threatening issues.

I'm 79 now and no longer dive but about 20 years ago my VR3 (latest technology at the time) got me bent following a deep dive on tri-mix, now I understand why!

Probably the best visualisation I have ever seen in a comparison of deco models! I wish there was a dive software available that gave you this exact output in your dive planning... You could arguably tinker around with your (GF-)settings until you are okay with the "graphic" of saturation you desire. What a wonderful tool that would be in decompression planning and informing yourself before the dive of what your different settings do to your tissues... I really hope someone comes up with something like this! Great work!

extremely interesting and informative! this gave me a better understanding of the Models used and clarified WHY deep stops don't appear to be beneficial. similar to another presentation, i can't believe no one has commented and thanked you for this presentation! all divers should watch this (especially Technical divers, rebreather divers and those interesting in Technical Diving). i appreciate this presentation very much! thank you!

I am not even a diver (nor do i really aspire to be one) but listening to theese presentations is really interesting. It’s a pleasure to listen to a passioned professional talk.

This is a great presentation! Most divers don't get the differences in the compartments and their effects. The five minute compartment fills rapidly and limits a 100' air dive to 20 minutes. But it also off-gasses just as fast. Slower compartments fill more slowly and may not control the 100' dive, but they also off-gas more slowly. Simply put: This is why deep stops can be a problem.

Very informative, well illustrated and explained! This answered so many questions I had on deco theory. Thank you!

Trouble is that the theory never fully worked like that for me. Getting 1st or 2nd degrees of bent seemed to relate far more to my emotional state on diving, seasickness, cold, dramas and traumas (fears, lost, tangled in guideline etc) than the depth involved. (on air to 30-55m). Best wishes. Dr Alex.

You just have to like Simon Mitchell :) Great presentation!

Excellent talk. It could have done with a note on how gas choices might influence supersaturation under various profiles, as air dives dominated the discussion, but really a really good discussion.

Agreed with all conclusions at 39:42. The proceeding heat charts are fantastic in showing whats really going as to the cause of the DCS. The simple solution is to add 3 missing 'hyper fast tissues' into Buhlmann ZLH16 and and use this model to generate the dive profile and all will be good without having to use gradient factors to devine a model that actually works. Here's the tissues :- #1(t=1.1mins, m=2bars), #2(t=1.8mins, m=2.72bars), #3(t=3mins, m=2.94bars) Cheers.

This was the best explanation of deco models I've ever seen. Have there been any updates on the matter in the past 5 years since this talk? Where would one look for new publications in this field?

Great presentation! Easy to follow and understand.

Excellent, succinct statement of the physics of what is happening during compression at 6:40. Good enough for a five year old, good enough for me. :)

Very interesting, good info. Thank you

Very interesting and informative talk. Thanks!

Thanks very much, that was excellent. Easy to understand.

What an impressive way of presenting a complex topic in a simple way. Thanks for sharing!!!!!

Can you explain more about how deep is shallow and deep stop in meters and how long should we wait until surfacing? Can we trust our dive com for each stop it tells us ? Excellent presentation indeed

What an excellent lecture! Thanks a lot!

very informative, thanks!

This is really useful info!!! Excellent presentation.

Excellent video and presentation.

nice presentation, thanks!!

Thank you. Raphael Santore

Excellent video! Very informative.

this is a fantastically interesting video. true science

thanks a million

Great video. It demonstrate than trying to be smarter than the rules are not always a good idea.

Awesome presentation and well illustrated!

I'll suggest that the tables should ensure that the first stop is a decompression stop NOT a continuing absorption stop.

great presentation, super informative!

Lovely to hear you again Simon after your helpful advice back in 2012 re my son's lung problem!

great content...

This is brilliant! So many questions answered in an excellent and clearly presented way. I’ll try some dive plans based on GF50/75 and see if I like ‘em 😀

This is just GREAT!

Excelente presentación.

Hello Simon. Thanks very much for the brilliant presentation.

Great overview! Is this still true today or are there already new studies suggesting/proofing otherwise? Is there a number telling us how many Tec Divers do use GF / VPM ?

Awesome presentation, I'm not an expert at all and could follow everything clearly!

Are there any kind of studies of this type (bülhman) for recreational divers profiles? Very very interesting indeed.

Very well done, Simon. I provide this to my students, as part of their Basic Trimix training course.

But alas deep stops give several times more frequent DCS and larger bubbles. I stick to shallow stops with the upper GF’s. Statistics is such. Btw, There were 11 DCS with bubble model, but that case was considered as inconsistent.

It seems like everyone wants that 1 magical answer that tells them what profile to dive. From my perspective there seems to be too many variables to nail down a “one size fits all” answer. It seems the best answer (at least to me) is to learn the model you use and stick with it. I’ve had older tec divers tell me they been using the same profile for 20 years and to not break what works.

Thank you so much for this presentation. Very interesting and informative. Definitely makes me want to stick with GCM over Bubble Models. I've watched this at least 3x

Thank you for uploading.

Am not a diver but the notion of fast tissue vs slow tissue rate absorption has been known for so long I can not for the life of me understand how the dive community could not see the issue with deep deco stops. It’s elementary and even surprised the navy chased the theory because it was an incomplete theory that surely could have been exposed by modelling known slow tissue deco profiles. Very strange.

Imo especially in the military decompression is simple u make ur stops at the proper depths for your body and the depth u dived def make sure u have enough fuel(air/oxy/helium/trimix/etc) def don’t dive alone if possible and def plan dives on the surface with plan abcd

fantastic vid much information how do i get a copy ?

Hi, at the end he says that he likes GF 50/75 ... but without saying for what deco gases ...?

Does the navy use gradient factors in their gas content models? Probably not right?

Could this be used in the development of drug delivery or treatment procedures?

44:25 - GF 50/75 -> 50/70

I'm working on the jab deco tables. We must cut down on clotting.

Am i the only one who is watching this and then all of a sudden my left ear gets blocked rofl

If you dive deeper than 40m, recreational dept, listen and learn.

I'm afraid the # of forum hits alone is not a relevant metric for determining the popularity of anything. Much like the number of pages Google serves up in response to any given key phrase: it is simply not indicative of anything by itself. Most sites don't track "hits" anymore for this reason. More than half of that traffic is robotic anyway.

You should turn off comments instead of deleting them (assuming that's happening because there's 48k views and 0 comments). Please do it to stop people wasting their time commenting.

I can’t believe theirs no discussion on this!

Nope way toooo much talk………KISS theory mate