PADI Deep Diver course- gas management

[therookie]

This is a tad outside the topic, but, as you should be aware, decompression science is still a bit of an art. We are still using data based on extrapolations from experiments done on goats from 1908. The slow tissue/fast tissue is merely "modeling".

DAN's experiments with doppler ultrasound testing really was a game changer and revealed that our "no decompression" dives produced quite a few bubbles on some divers. Bubbles out of saturation? Sounds like a decompression dive to me? And then of course you have plenty of data on divers getting bent on "no decompression" dives.

So I will agree to disagree based on current data. But, to bring this back on topic, that is the whole reason GUE teaches minimum gas standards in REC1, day one, every dive is a decompression dive and you should, at all costs, have enough gas to surface at a safe rate and do "safety" stops.

And this is why I am so grateful to sites like ScubaBoard and threads like this one that raise these topics. My entire exposure to the diving industry comes from years of visiting Roatan, because it is close to where I live, and in all those years of walking on the beach of West Bay, and then up the beach to West End's main road with its multitude of dive shops literally a stone's throw from each other, I have never seen Global Underwater Explorers advertised. Possibly I have just missed it - I will look again when we go next. Having someone put their principles of gas management planning out in public where anyone, regardless of the agency they trained with, can access that information is incredibly valuable for all. It has allowed me, as @boulderjohn just posted, to do the research myself - which has done wonders for my confidence.

The really sad part? All this conversation about SAC rates and minimum gas and all the rest of what I've been reading on ScubaBoard this week is really making me want to convince my wife to book us flights from SAP to RTB so that I can spend most of the mornings at safety stop depth or lower, and afternoons on the beach with her (particularly magical on cruise ship days after 3pm since the day trippers usually need to be back on the boat by 4, and West Bay/West End sunsets are so amazing even the people who live there will regularly pull out their phones and take pictures of them...)

But I simply do not have the time at the moment...

 

[tursiops]

A few years ago, I published an article on current thinking on deep stops in decompression diving, with an enormous amount of help from Simon Mitchell. I wanted to do the same thing for ascent profiles in NDL dives, and asked Simon for similar help. He said he couldn't help me, because NDL dives are different, and he himself did not have strong feelings on it.

So I researched myself. As part of that research, I contacted GUE headquarters and asked for an explanation for the thinking behind their min deco philosophy. I got a very thorough explanation, so I am quite sure I understand it.

What I don't understand is what you say here, because that wasn't mentioned. In response to my statement saying that there is a difference between decompression dives and no decompression dives, you reply that it is very important to have enough gas to do your ascent on an NDL dive. I am not clear on the connection.

Give it up. You are arguing with people who don't think anymore, and instead just quote GUE, wheter it is applicable or not.

 

[jadairiii]

What I don't understand is what you say here, because that wasn't mentioned. In response to my statement saying that there is a difference between decompression dives and no decompression dives, you reply that it is very important to have enough gas to do your ascent on an NDL dive. I am not clear on the connection.

I can say that it is taught in GUE REC1.

As to current science on that matter, a good look at what David J. Doolette, Ph.D. is doing at the Navy Experimental Diving Unit in Panama City (I think that is the city). Interesting work and dealing with deep stops, HE vs N2, and deep "bounce" diving (what we all do). And, to repeat myself, DAN doppler research.

What I found to be one of the most interesting topics Dr Doolette discussed was the fact that Navy tables past 150' were all all extrapolations and all based on sat diving, not recreational "bounce" diving. That is something he has been studying now for a while.

 

[tursiops]

As to current science on that matter, a good look at what David J. Doolette, Ph.D. is doing at the Navy Experimental Diving Unit in Panama City (I think that is the city). Interesting work and dealing with deep stops, HE vs N2, and deep "bounce" diving (what we all do). And, to repeat myself, DAN doppler research.

What I found to be one of the most interesting topics Dr Doolette discussed was the fact that Navy tables past 150' were all all extrapolations and all based on sat diving, not recreational "bounce" diving. That is something he has been studying now for a while.

Out of dae and irrelevant to the PADI Deep Diver course.

 

[boulderjohn]

DAN's experiments with doppler ultrasound testing really was a game changer and revealed that our "no decompression" dives produced quite a few bubbles on some divers.

And, to repeat myself, DAN doppler research.

I am not sure what DAN research you are talking about. Could you please link to it?

To the best of my knowledge, the first use of Doppler blood imaging was done by PADI nearly a half century ago in the studies that led to the PADI Recreational Dive Planner. Those studies did indeed show that pretty much everyone bubbles to some degree while diving, with some people bubbling more than others. They were called "silent bubbles." One of the researchers, Dr. Michael Powell, was particularly interested in that. He mentioned it on a number of occasions on ScubaBoard back when he was ScubaBoard's Doc Deco. He was confounded by the fact that some people bubbled so much--his theory, which he could never prove, related to micronuclei created by exercise.

The point of that is that the fact that people bubble during NDL dives has been known for decades. It is not anything new, and I don't understand how it relates to this discussion.

BTW, more recent research on this, done by Dr. Doolette, indicates that not only does pretty much everyone bubble, but the degree to which they bubble varies from dive to dive.

 

[jadairiii]

I am not sure what DAN research you are talking about. Could you please link to it?

Comparative Testing of Ultrasound Devices in Monitoring VGE

In this study, DAN researchers compare the effectiveness of three different ultrasound devices used to monitor post-dive venous gas emboli in healthy divers.

dan.org

 

[boulderjohn]

Comparative Testing of Ultrasound Devices in Monitoring VGE

In this study, DAN researchers compare the effectiveness of three different ultrasound devices used to monitor post-dive venous gas emboli in healthy divers.

dan.org

This is a comparison of different ultrasound devices. It is not a revelation about bubbling in NDL divers. For that, I believe we need to go way, way back to the PADI studies.

 

[jadairiii]

This is a comparison of different ultrasound devices. It is not a revelation about bubbling in NDL divers. For that, I believe we need to go way, way back to the PADI studies.

But the fact is, there are bubbles. The assumption, going back to Haldane was "no bubbles, no troubles", and no decompression needed.

We now know, for a fact, that even on, supposedly, NDL dives, we got bubbles.

 

[tursiops]

"no bubbles, no troubles",

Haldane did not say that, that I can find. Who are you quoting?

 

[boulderjohn]

But the fact is, there are bubbles. The assumption, going back to Haldane was "no bubbles, no troubles", and no decompression needed.

We now know, for a fact, that even on, supposedly, NDL dives, we got bubbles.

Yes, there are bubbles. As I wrote, PADI discovered that well over 40 years ago. There is nothing new there. So what is your point about them?