247 Feet -- "We can't stay here for very long"

[Kevrumbo]

A few years back I was diving repetitively to 200 fsw to film at those depths. I took about three months of gradually deeper diving to get there and dove almost daily. I experienced relatively little narcosis while at maximum depth and could locate, frame and follow movement of critters with my camera with no problem. I never went deeper than 201 fsw because I had set that as my limit. More recently I've been noticeably narced at depths as shallow as 107 fsw which I attribute to a decreased frequency of dives and less tolerance of the nitrogen build-up.

When I worked with a few Cousteau dive crews, we rarely went below 100 fsw as bottom time was important in filming.

Cousteau, Dumas (and tragically with Fargues) -they all thought the danger due to Nitrogen Narcosis in deep Air could be accommodated or "gotten used to" in building up a tolerance, rather than today's understanding of the more insidious nature of CO2 poisoning/Hypercapnia, quickly incapacitating and leading into unconsciousness, and/or hyperoxic O2 seizures.

The point is at extreme depth, you may be generating more metabolic Carbon Dioxide due to exertion than you are physically capable of eliminating by exhalation -even just floating there neutrally buoyant at 10 ATA on deep Air (ppO2 2.1) with its increased gas density (13 g/L) ten times greater than at the surface, the work-of-breathing by itself can spiral into excess CO2 retention while also increasing the likelihood of Oxygen Toxicity Seizures.

Breathing air maximum terminal depth

 

[lermontov]

You know there is a difference between ignorance and stupidity and being adventurous and pushing the boundaries. In mountain climbing, the smart ones back away from summiting Mt Everest when they know its stupid (weather, cerebral edema...). Smart divers, say no when the risk is too high. Like calling the dive when it just doesn't feel good. Or refusing to dive when the conditions are poor but you paid $xx.yy for a dive trip.

yes and no - there are climbs I've done as a relative novice that ive turned back on that with more experience and knowledge now realise theres was plenty left in reserve -likewise theres climbs I did in ignorance that i would hesitate to do now with 20+ years experience under my belt.

as one progresses in alpinism the margins for safety get smaller and smaller because they rely on their skill and experience to avoid getting into trouble in the first place, diving ? is it the same ? maybe, the more I dive the more aware of potential hazards I've become but i certainly dont reduce gas volumes or reduce my equipment list - but then again im a lot older and not as driven as i once was -so maybe its related to that.

so you do a dive and the vis isn't great - a novice may remark how desperate it was- an experienced diver might say its not much fun - the objective situation is identical but the threshold of perceived risk is a lot different

 

[USMC CPL.]

yes and no - there are climbs I've done as a relative novice that ive turned back on that with more experience and knowledge now realise theres was plenty left in reserve -likewise theres climbs I did in ignorance that i would hesitate to do now with 20+ years experience under my belt.

as one progresses in alpinism the margins for safety get smaller and smaller because they rely on their skill and experience to avoid getting into trouble in the first place, diving ? is it the same ? maybe, the more I dive the more aware of potential hazards I've become but i certainly dont reduce gas volumes or reduce my equipment list - but then again im a lot older and not as driven as i once was -so maybe its related to that.

so you do a dive and the vis isn't great - a novice may remark how desperate it was- an experienced diver might say its not much fun - the objective situation is identical but the threshold of perceived risk is a lot different

You add gear training and skills for the dive you are doing. I.e. tec training instead of deep dives on air. With the added gear, training and experience you add to your safety margin. Hope this makes sense.

 

[drrich2]

This looks crazy to me -- was the science just not fully developed yet, or were they nuts?

Interesting stuff! I wonder, in the 1950's, how prevalent and reliable were the types of info. we recognized as 'diving tables,' and later dive computers? Did these guys know and choose to disregard NDLs, in other words?

If not, then it stands to reason their perceptions of dive limits (e.g.: depth & time) were informed experientially; they gradually pushed the limits till the limits pushed back in an alarming way. Perhaps advanced divers with a good mix of natural aptitude and seasoned experience could handle narcosis and deep air diving well enough for that? Divers with a higher purpose to explore & share their findings with the human race, acting as ambassadors for the natural world? Or at least make a living...

Even then, somebody got the bends, narcosis was perhaps accepted as a fairly common aspect of diving to learn to deal with, and there was a recompression chamber on board?

Can you imagine a modern day recreational scuba dive boat (no recompression chamber!) taking people out and advising dive parameters that'd result in somebody in the group getting bent, at least a few getting narced, and all these the typical 'dive tourists' crowd?

To determine 'nuts,' we need to consider what they were trying to do, was it reasonable, under what circumstances (e.g.: knowledge base to draw from, equipment options) and if all that was legit, were they conducting themselves in a reasonably safe manner given the resources they had?

Richard.

 

[beester]

Well to the OP: First of all you need to understand that "the silent world" and subsequent films are just that... movies. Many of the things you see in these are staged, edited, to progress an adventure story.

I licked it up as a small boy... specially since my uncle was a 3 * cmas dive instructor who had met JJC (his dive cert was signed by JJC). However much is make believe. From the opening scene of divers carrying torches underwater (a bit like 20000 leagues under the sea or the james bond movie thunderball) to the famous "narcosis" scene... but just remember most of it is (bad) acting.

That being said they were for a while on the cutting edge of diving experiments and technology. From cave diving (Cousteau almost lost his life diving the fountain de vaucluze) to progressively deeper and deeper air dives (Maurice Fargues died during a 390ft attempt). Which is by the way the reason why most CMAS high level certifications are depth limited to 300ft (90m) on air (my CMAS cert still has this).

They kept experimenting, on camera's, underwater communication, living underwater (conshelf 1 and 2), dpv's, and deep diving (later COMEX)... very fascinating stuff.

Luckily we have moved on and hopefully keep slowly progressing. In any case deep diving on air has become for various reasons frowned upon, because there are better ways to doing it then 65 years ago.

 

[Akimbo]

I took about three months of gradually deeper diving to get there and dove almost daily. I experienced relatively little narcosis while at maximum depth and could locate, frame and follow movement of critters with my camera with no problem.

I have seen and experienced the same thing. It was actually predictable and planned on by diving supervisors on the deep air jobs. Experienced deep air commercial divers would start to acclimatize after about 4-6 dives (2x dives/day). Deep air is restricted a lot more now, starting in the North Sea to a max depth of 50M/165' in the late 1970s. That rule did a lot to accelerate the use of saturation diving and purpose-built DSVs (Diving Support Vessels).

Cousteau, Dumas (and tragically with Fargues) -they all thought the danger due to Nitrogen Narcosis in deep Air could be accommodated or "gotten used to" in building up a tolerance, rather than today's understanding of the more insidious nature of CO2 poisoning/Hypercapnia, quickly incapacitating and leading into unconsciousness, and/or hyperoxic O2 seizures.

Keep in mind that relationship had been "recognized" for a very long time, but is still poorly understood. Surface supplied commercial and military divers have used deep breathing to optimize CO2 elimination as long as I can remember.

 

[Compressor]

I am curious as to the physiologic mechanism for adapting to nitrogen narcosis with repetitive acclimatization. There is some evidence that nitrogen at depth alters the cell membrane of brain cells leading to altered function.
Thanks for your input.

 

[Akimbo]

I am curious as to the physiologic mechanism for adapting to nitrogen narcosis with repetitive acclimatization

You're not alone.

It "may" not be physiologic mechanism in the classic sense at all. It is "possible" that part of the adaptation is brain-driven* acclimatization that affects lung ventilation and managing some abnormal influences on brain processing. * I'm reluctant to use the word psychological because it has some loaded connotations.

For example, consider the reported effects on arthritis changes from weather . I submit that it is too widespread and repeatable over generations and cultures to be completely imaginary. However, I have yet to read that medical science has been able to find the cause and effect... yet. That lack of evidence is too often interpreted as "it's all in your head". Yeah it probably is in our head (brains) like almost everything else that is controlled in the body, but that's not the same thing as it is unfounded and only a figment of your imagination.

In the case of acclimatization to Narcosis, the effect is easily and widely observed in diver performance. That "performance" is much easier to observe in surface-supplied divers because the diving supervisor, who obviously isn't narked, can communicate with the diver, can often see the diver via head-mounted and ROV video cameras, and can compare the time and mistakes it takes for "comparable" work be completed. That data does NOT provide science-level comparable data to prove anything conclusively and it would be a huge mistake to think that acclimatization to Narcosis is some kind of binary switch. It is also not consistent from person to person but is relatively repeatable for the individual.

Performance is also a pretty complex topic. Take a diver performing a mechanical assembly. Sensory perception, muscle control/texterity, the ability to concentrate, balance, and about a hundred other factors interact. I think it is fair to say that we all perform better with familiar tasks and experience managing distractions. I cringe when Narcosis is compared to alcohol or hallucinogenic narcotics because the analogy is very misleading.

@drbill's slow workup approach is the most prudent approach for individual self-discovery. Unfortunately very few divers get the opportunity to dive often or deep enough to experience the relatively short-lasting acclimatization phenomenon. However, the gradual and repeated baby-steps nearing increased levels of Narcosis does help you manage and, more importantly, detect how and to what extent Narcosis is compromising you. Once detected and it exceeds your comfort level the cure is pretty simple... go up.

 

[mdb]

Once, while testing a pair of new Computers-The early Farallon Computers, off the north side of Oahu,
I was on a down line with multiple computers strapped on both arms.

We were diving on air.

I got narced out at about 180 fsw.

I was pulled back to the line and started a slow ascent.

At about 120 fsw I cleared up a bit and looked at the computers.

They all had different readings.

The early stages of decompression computers.

Now we have some very advanced devices.

 

[Compressor]

You're not alone.

It "may" not be physiologic mechanism in the classic sense at all. It is "possible" that part of the adaptation is brain-driven* acclimatization that affects lung ventilation and managing some abnormal influences on brain processing. * I'm reluctant to use the word psychological because it has some loaded connotations.

For example, consider the reported effects on arthritis changes from weather . I submit that it is too widespread and repeatable over generations and cultures to be completely imaginary. However, I have yet to read that medical science has been able to find the cause and effect... yet. That lack of evidence is too often interpreted as "it's all in your head". Yeah it probably is in our head (brains) like almost everything else that is controlled in the body, but that's not the same thing as it is unfounded and only a figment of your imagination.

I the case of acclimatization to Narcosis, the effect is easily and widely observed in diver performance. That "performance" is much easier to observe in surface-supplied divers because the diving supervisor, who obviously isn't narked, can communicate with the diver, can often see the diver via head-mounted and ROV video cameras, and can compare the time and mistakes it takes for "comparable" work be completed. That data does NOT provide science-level comparable data to prove anything conclusively and it would be a huge mistake to think that acclimatization to Narcosis is some kind of binary switch. It is also not consistent from person to person but is relatively repeatable for the individual.

Performance is also a pretty complex topic. Take a diver performing a mechanical assembly. Sensory perception, muscle control/texterity, the ability to concentrate, balance, about a hundred other factors interact. I think it is fair to say that we all perform better with familiar tasks and experience managing distractions. I cringe when Narcosis is compared to alcohol or hallucinogenic narcotics because the analogy is very misleading.

@drbill's slow workup approach is the most prudent approach for individual self-discovery. Unfortunately very few divers get the opportunity to dive often or deep enough to experience the relatively short-lasting acclimatization phenomenon. However, the gradual and repeated baby-steps nearing increased levels of Narcosis does help you manage and, more importantly, detect how and to what extent Narcosis is compromising you. Once detected and it exceeds your comfort level the cure is pretty simple... go up.

Very nice explanation and appreciated just as much if not better.