An age-old question: ways to 60m.

[CG43]

Your empirical observations (and mine) are statistically insignificant to the volume of data that goes into a scientific study.

Here you leave the path of science.
You must be able to explain every dive, or specify the validity range of your statements.
However, if you proceed without a validity range and take a value that is conservative, thus applying it to almost all dives and divers, you have no reason to call that a physiological limit.

So I'm genuinely curious, what training does FFESM/CMAS provide that overcomes physiology?

Who must overcome physiology?
You know that a few diver can hold their breath for over 15 minutes or dive to 132 meters deep using just fins! When you create a statistic of what the average scubsdiver's freediving performances are, it has little relation to the physiological limits of humans.
What applies to freediving also applies to a lesser extent to scuba diving.
If you are really interested in "air deep" training, then you should write here in another way .
May be then you would receive responses.

 

[Kay Dee]

If you are really interested in "air deep" training, then you should write here in another way .
May be then you would receive responses

I might be wrong right, but I dont think that @wetb4igetinthewater is looking for any(thing to do with) deep air training.

Who must overcome physiology?
You know that a few diver can hold their breath for over 15 minutes or dive to 132 meters deep using just fins! When you create a statistic of what the average scubsdiver's freediving performances are, it has little relation to the physiological limits of humans.

 

[leadduck]

The thing with hypercapnia due to workload while breathing gas with high density is described here: https://dan.org/alert-diver/article/performance-under-pressure

Full paper: https://www.omao.noaa.gov/sites/def...rs and Scientific Diving Proceedings 2016.pdf page 66.

Since this research was published in 2016, older training programs won't mention it. Training agencies underestimated the risks of deep air diving, and overestimated the possibility of adaptation, too. This doesn't mean that you could overcome physiology by taking a class that somebody created 20 years ago. It just means that their training program is outdated.

 

[wetb4igetinthewater]

Here you leave the path of science.
You must be able to explain every dive, or specify the validity range of your statements.
However, if you proceed without a validity range and take a value that is conservative, thus applying it to almost all dives and divers, you have no reason to call that a physiological limit.


Who must overcome physiology?
You know that a few diver can hold their breath for over 15 minutes or dive to 132 meters deep using just fins! When you create a statistic of what the average scubsdiver's freediving performances are, it has little relation to the physiological limits of humans.
What applies to freediving also applies to a lesser extent to scuba diving.
If you are really interested in "air deep" training, then you should write here in another way .
May be then you would receive responses.

You completely misunderstood my post.

The thing with hypercapnia due to workload while breathing gas with high density is described here: https://dan.org/alert-diver/article/performance-under-pressure

Full paper: https://www.omao.noaa.gov/sites/def...rs and Scientific Diving Proceedings 2016.pdf page 66.

Since this research was published in 2016, older training programs won't mention it. Training agencies underestimated the risks of deep air diving, and overestimated the possibility of adaptation, too. This doesn't mean that you could overcome physiology by taking a class that somebody created 20 years ago. It just means that their training program is outdated.

Thank you for posting the direct links. You would think that these studies after peer review would end arguments. But then some people think the earth is flat even though the ancient Greeks figured out the circumference of the earth thousands of years ago. I guess news travels really slowly in places. So I should accept that this debate will still be going on in 4500 AD

 

[CG43]

The thing with hypercapnia due to workload while breathing gas with high density is described here: Performance Under Pressure

Full paper: https://www.omao.noaa.gov/sites/def...rs and Scientific Diving Proceedings 2016.pdf page 66.

Without the diver's workload, this article is very incomplete.
I can't find this extremely important value, but perhaps someone can ?
If not, why hasn't anyone noticed it yet?
In the paper you read :

Gas density : One of the most important influences on work of breathing in diving is the increase in density of respired gas that occurs as depth increases.

Okay, but what has the greatest influence on dynamic airway compression,
breathing power, and breathing work is the gas velocity, which is squared (exponent of 2) while the density is linear (exponent of approximately1).
You will find the result of this very important topic later inplizit (hidden) in the paper .

Moderating expectations of work capacity at depth Unsurprisingly (given the above discussion) it is widely recognised among experienced divers that as depth increases there should be a corresponding moderation of expectation of work capacity. Hard work (with an inevitable increase in CO2 production) is best avoided on a rebreather at any time, but this is particularly so at increased deep depths where the respired gas density is likely to be trending toward (or exceeding) the ideal limit. There are many practical strategies which help with reducing work at depth including exhibition of basic dive skills (such as maintenance of good buoyancy control and good trim/streamlining in the water), intelligent task planning, and the use of assistive technology such as diver propulsion vehicles. However, the use of such strategies is not a substitute for minimising the work of breathing in a UBA and strategic planning of gas density because events such as an emergency situation requiring extra work, or failure of a diver propulsion vehicle can occur unexpectedly.

And there are more and more practical strategies which help to reduce work and production of CO2 at depth for a recreational diver who can chose his way to dive witch a working pro diver can't do .

 

[wetb4igetinthewater]

Without the diver's workload, this article is very incomplete.
I can't find this extremely important value, but perhaps someone can ?
If not, why hasn't anyone noticed it yet?
In the paper you read :

Gas density : One of the most important influences on work of breathing in diving is the increase in density of respired gas that occurs as depth increases.

Okay, but what has the greatest influence on dynamic airway compression,
breathing power, and breathing work is the gas velocity, which is squared (exponent of 2) while the density is linear (exponent of approximately1).
You will find the result of this very important topic later inplizit (hidden) in the paper .

Moderating expectations of work capacity at depth Unsurprisingly (given the above discussion) it is widely recognised among experienced divers that as depth increases there should be a corresponding moderation of expectation of work capacity. Hard work (with an inevitable increase in CO2 production) is best avoided on a rebreather at any time, but this is particularly so at increased deep depths where the respired gas density is likely to be trending toward (or exceeding) the ideal limit. There are many practical strategies which help with reducing work at depth including exhibition of basic dive skills (such as maintenance of good buoyancy control and good trim/streamlining in the water), intelligent task planning, and the use of assistive technology such as diver propulsion vehicles. However, the use of such strategies is not a substitute for minimising the work of breathing in a UBA and strategic planning of gas density because events such as an emergency situation requiring extra work, or failure of a diver propulsion vehicle can occur unexpectedly.

And there are more and more practical strategies which help to reduce work and production of CO2 at depth for a recreational diver who can chose his way to dive witch a working pro diver can't do .

Please explain the workload reduction procedures for dealing with emergencies: burst disk failure, hose ruptures, and other equipment failures. Dive buddy emergency like loss of consciousness or oxto convulsions.

While I used to ridicule GUE (before the science caught up with them) for switching to trimix at 30 meters, I have since learned that their configuration and philosophy is based on how to return safely after a serious emergency occurs.

While I don't dive their configuration, I try to adopt their philosophy of how do I and my buddies get out alive when something serious happens. Keeping gas density at 5.2 g/L gives some room with increased gas density caused by increased CO2 generation.

Maybe I'm too paranoid from when Andy Grove ran Intel (he wrote Only the Paranoid Survive). But I have a little girl I hope to walk down the aisle one day.

Edit: now just to be clear, the complexity diving at the same depth varies on conditions. Surely we can all agree that diving inside a real wreck (not an artificial reef) in cold water is not the same as a tropical dive in the blue with no overhead.

If you disagree, please click on disagree so I can add you to my ignore list.

 

[johndiver999]

I thought it interesting that at least one member now refers to diving between 100 and 130 ft as the "deep air" range. I think that is kinda ridiculous.

I have done a good bit of diving around 180 ft + on air, and my primary problems have been narcosis and nothing that I can identify as a problem with gas density - but I do know from experience that you can't work too hard at depth, and if/when you do, it is really hard to get caught up again.

I don't agree with the general idea that the narcosis from deep air is necessarily a huge danger (particularly to those that do it relatively often, or who have acclimated to it or to people that have demonstrated the ability to function pretty well below, say 160 feet many dozens of times.

Obviously, being impaired reduces safety, but safety itself is a relative thing. If we strived for total safety, we would never leave the swimming pool.

From my perspective, "deep air" needs to be approached with extreme caution (if at all). People have to realize or acknowledge that SOME people are seriously impaired at 100, 130, 160, 200 ft. I know some very accomplished divers, who just won't dive to even 130 ft, because they don't like how it feels or they don't trust themselves. It is extremely important to understand and respect divers who just aren't suitable for deeper air. If someone is a new diver, they really have no idea where they are going to fall on the narcosis spectrum, so EXTREME caution and very slow progression is essential if they think they might want to try it.

Another "problem" I have with a lot of the opinions expressed in this thread, is that they are taking a very crude approach to it. "Deep Air" is either (a) horrible, terrible, irresponsible or (b) reasonably "safe" with proper gear, training and precautions. In order to have a reasonable discussion about deep air and safety, you have a more nuanced approach and also to narrowly define the depth range you are talking about, rather than ranting about "deep air".

I think the true answer about deep air is that we really need to be more precise and narrowly define the depth ranges one is considering. From my perspective, there is a HUGE difference between diving say 130 or 160 or 190 ft. They are NOT similar with respect to the narcosis.

I personally don't expect to be going past 200 ft on air any more, because I can just feel how strongly my senses are impacted and my inability to think critically becomes uncomfortable to me. When the discussion starts to involve world record dives and/or going well past 300 ft on air, it really doesn't have much relevance to someone who might want to dive to 60 meters.

I also find it strange that this community and many diving agencies are perfectly fine with "shark diving" (at least with regard to the diver's personal safety), when we have ample recent examples of just how dangerous it is when done with certain protocols and certain shark species.

Somehow we accept that some OW diver from Iowa can make a REASONABLE assessment of the dangers of shark diving, (when they have zero experience with it), but another diver who has many hundreds of solo deep dives, can not reasonably explore going past 130 ft on air (in a logical, incremental and somewhat informed) manner. The hypocrisy in attitudes toward diver safety between the "shark huggers" and "deep-air-is-deadly"advocates is glaring to me.

In general, I think diving to 180 ft on air is not really safe. I almost always do it alone because who wants to dive with another idiot who thinks they can function that deep? You know your buddy is going to be impaired and compromised - so their ability to help you is probably pretty limited, unless they have done a ton of it.

I am pretty comfortable to about 190 in conditions I am acclimated to, but a somewhat recent deep dive was a real eye opener. I have never had an issue (even well past 200 ft) where I felt like I was completely losing track of time, or the situation or remembering what was going on during the dive. However, on my last deep dive (with a buddy) we made a free descent very rapidly to 195 or so, and found an adverse current (going the wrong way) and the visibility was limited at 30 feet and pretty dark.

We had to swim/crawl on the sand (busting ass) into the current for maybe 600-700 feet to reach the desired wreck. Time and air was limited, so we swam hard, and I felt that I was working at very close to the absolute limit of my physical (aerobic) capacity (for this depth). I was able to control my respiration, but it was a real chore to force myself to take very deep inhalations and exhale almost fully - which is required to work hard and survive at 190.

My buddy and I made it to the desired wreck (about 6 minutes later than we hoped). I knew the wreck well but still ended up making a significant (and stupid) navigational error by going the wrong way on the wreck. I did not realize until I got up top on the deck around 160 (and slowed the swimming effort down considerably). I never really felt "bad" narcosis on any portion of the dive and felt pretty good at 160 ft and was able to spear a fish and deal with it, without any difficulties.

The problem was... when my buddy and I were talking about the dive, he commented about the sawfish that we saw which he said was well over 20 ft long. This would be extremely unusual and literally "unforgettable" for anyone with their senses. I agued that perhaps the sawfish was not that close or obvious and perhaps I was a little buzzed and distracted and just didn't see it. What REALLY opened my eyes, was when I reviewed some crappy go pro video that was dark and misaligned but actually SHOWED the giant sawfish was within 8 or 10 feet from my face and had to be completely visible - but I have no recollection of it- Only remnant of a weak memory is about thinking "there are some big animals this deep" - but nothing about a sawfish or anything clear.

This along with the gross navigational error I made on a very familiar wreck, has really surprised me. I assume that I was significantly impaired from CO2 retention from working too hard (along with the obvious narcosis) but I was clearly diving past my limits and was too numb to realize it.

 

[Celt]

Without the diver's workload, this article is very incomplete.
I can't find this extremely important value, but perhaps someone can ?
If not, why hasn't anyone noticed it yet?
In the paper you read :

Gas density : One of the most important influences on work of breathing in diving is the increase in density of respired gas that occurs as depth increases.

Okay, but what has the greatest influence on dynamic airway compression,
breathing power, and breathing work is the gas velocity, which is squared (exponent of 2) while the density is linear (exponent of approximately1).
You will find the result of this very important topic later inplizit (hidden) in the paper .

Moderating expectations of work capacity at depth Unsurprisingly (given the above discussion) it is widely recognised among experienced divers that as depth increases there should be a corresponding moderation of expectation of work capacity. Hard work (with an inevitable increase in CO2 production) is best avoided on a rebreather at any time, but this is particularly so at increased deep depths where the respired gas density is likely to be trending toward (or exceeding) the ideal limit. There are many practical strategies which help with reducing work at depth including exhibition of basic dive skills (such as maintenance of good buoyancy control and good trim/streamlining in the water), intelligent task planning, and the use of assistive technology such as diver propulsion vehicles. However, the use of such strategies is not a substitute for minimising the work of breathing in a UBA and strategic planning of gas density because events such as an emergency situation requiring extra work, or failure of a diver propulsion vehicle can occur unexpectedly.

And there are more and more practical strategies which help to reduce work and production of CO2 at depth for a recreational diver who can chose his way to dive witch a working pro diver can't do .

Work load is the problem with gas density for the working diver, but you can take measures to avoid getting out of breath. Pace yourself to your individual fitness level is the main thing. We would also clean the work area of any fouling and put an up line close to the diver. In the photos is a cleared area of brass bar ingot and the up line in place beside a working diver. At the first sign of an insufficient breath you must rest and get your breathing under control.

 

[tursiops]

I was clearly diving past my limits and was too numb to realize it.

THIS is exactly the point. Thanks for being so honest. It may save someone's life.

 

[CG43]

Dr. Simon Mitchell page 78 :

SIMON MITCHELL: Unfortunately, CO2 retention is synergistic with nitrogen narcosis. There is enough evidence to believe that there is a synergy between the two; that is they are actually worse than the sum of their parts. CO2 retention is bad for narcosis. CO2 is a very narcotic gas. There was even a proposal at one stage that CO2 could be used as an aesthetic agent because if you breathe enough of it, it will render you unconscious. It never caught on. But certainly it is worse for narcosis. The other thing that you mentioned is the interaction between CO2 retention and oxygen toxicity. This interaction probably accounts for the higher risk of oxygen toxicity when divers are in the water compared to sitting in a chamber breathing oxygen through a low resistance system. In the water we all probably retain a little bit of CO2, especially if we are working hard or our breathing resistance is high. For a given PO2 this increases the risk of oxygen toxicity because CO2 dilates the cerebral blood vessels. So blood flow to the brain is much higher when CO2 is elevated, and this increases oxygen delivery and thus the oxygen tension in the brain. There are very good experimental data demonstrating this.
Many have had similar experiences.
When experimenting, I only varied one size whenever possible. If that was the depth, then that usually meant that ideal conditions prevailed. So warm water, good visibility, no current, easy navigation, buddies who suited me or solo. And the depths were then what the good JYC described, nothing more and nothing less.
The dense air was never a problem; we simply breathed more slowly, and I still had good rests between inhaling and exhaling, even with double hoses.
I will write something more about this topic, but it is too late today.