Special Techniques for Apnea Performance?

[efattah]

CO2 narcosis can only occur when there is unusual amounts of oxygen available. This occurs either during pure O2 inhalation at atmospheric pressure, or during hyperbaric conditions, for example deep diving.

It is well known among variable-ballast divers that hyperventilating before the deep dive reduces the narcosis. I have confirmed that with my own experiments.

It is known that CO2 amplifies nitrogen narcosis, and it was previously assumed that by hyperventilating, you simply reduced the 'CO2-N2 amplification effect.'

But now, after the Duke study, we see for sure that there is such thing as narcosis induced only by CO2. If you do the math on the CO2 level of a deep constant ballast or variable weight diver, you will find a PaCO2 way over 90mmHg during the worst phase of the dive (around 1/3 the way up the ascent).

I had the Duke study on my old hard drive, but it has since crashed. Someone on the freedivelist has it I think.

Eric Fattah
BC, Canada

[Jon]

CO2 narcocsis happens all the time in scuba diving. It is one of the top arguments against deep air diving.

A friend of mine was teaching a deco class a couple of weeks ago and it hit a student at 150' on an air dive. This is the max depth we dive air to nowdays, I won't talk about what we used to do. The blank stare and mindless kicking gave it away. He got the guy up and it went away. Nothing serious happened, but it was a gentle reminder of why we got away from this type of diving.

Normal narcosis is compounded by the effect of exercise and co2 build up.
As goofy as it might sound, most of the people I dive with use helium in their mixes for most dives below 100'. I did a dive last night to 90' on a 30/30 trimix. It realy helps if you are doing any kind of work underwater.

There have been many cases over the yeears of divers blacking out at depths far shallower than those that Eric Fattah is reaching. Many of these were do to poor perfroming regualtors and too much exertion at depth. Many of these divers also died.

I still fiind it amazing that divers are pushing 300' on a constant ballast dive. There is a LOT of exertion, co2 build-up, and narcosis involved in swimming up from that depth.

My hats off to all those that can do it, or even come somewhat close.

Jon

[homodelphinus]

I understand the mechanism where CO2 narcosis occurs in deep diving, because you use enriched O2 mixtures, my point is how can you have a BO when deep freediving, where you can say for sure that the cause is CO2 buildup instead of severe hypoxia? can it be a combination of both?

I invite anyone who has any comments on this subject to participate.

[efattah]

The problem is further confounded by the possibility of blacking out at depth from oxygen toxicity. Pipin, Audrey and Stefano Makula have all blacked out (near the bottom) on the sled at 100+m. Because they were on the sled, they were not exerting themselves and producing lots of CO2. So I think we can say quite safely that they blacked out from oxygen toxicity. A freediver who blacks out from CO2 toxicity will likely be diving in physical discipline such as variable, constant, or free immersion. The blackout will likely happen around 1/3 of the way up, when he is the most negative, producing tons of CO2, and yet the pressure is so high that his lungs are still completely collapsed, so the CO2 has nowhere to go except the blood.

When Genoni was attempting 145m on the sled last year, he had a problem with the lift mechanism, so he had to pull himself up the line from that depth. He reported extreme narcosis/hallucinations during the ascent, and he was probably just on the edge of a CO2 blackout. He eventually blacked out around 10m from hypoxia.

So, during his descent on the sled, he risked a blackout from O2 toxicity. During the first 1/3rd of the ascent, he risked a blackout from CO2 toxicity. Then, in the last 20m, he risked a blackout from hypoxia (which actually occured).

There are many ways to black out...of course, if you exhale before you go down, there is only one type of blackout that can happen; hypoxia.


Eric Fattah
BC, Canada

[fpernett]

First I want to clarify that the mix in deep diving is actually hipoxic, not enriched.
I agree with Eric that there is many ways for a BO to occur, and hypercapnia is one of them.
Hypercapnia does cause unconsciousness, by the way it was used in 1928, by Leake, as anaesthesic agent in humans, but it produces too many convulsions.
It's narcotis effects probably is due to the alteration in the intracellular pH, because the narcotic effects correlated better with the cerebrospinal fluid pH, than with the pCO2.
Hypercapnia also causes vasoconstriction in the pulmonary circulation, an as Eric said the lung volume is reduced, so is very difficult to wash out the CO2 from blood.
Hypercapnia also has effects in myocardial contractility, heart rate and arrhytmias threshold. In isolated preparations of heart muscle the high pCO2 produce diminished heart rate and contractility, but in intact subjects (not freedivers) the cathecholamines production overshadow this effect. The study from Ferrigno in the Maiorca family showed a diminished Cardiac Output during deep freediving. Maybe the training and mental focus avoid a high adrenalin production in us. But the low cardiac output is another risk for BO, and if we count the cardiac arrhytmias the risk increases.
Another issue is that high pCO2 displaces O2, the N2 content also can contribute to the narcosis in freedivers.
We have to remember that the BO is not only and Hyperoxic or Hypoxic problem. We have to balance O2, CO2 and N2 in the inmersion.

[Alun]

This thread started off discussing supplements and such things. My personal view about this is that if we want to improve our performance in freediving, then we're far better off working on our technique in the water than trying to optimise supplement intake.

The gains we (may?) get from these would be insignificant to the gains made from improving technique to make it as O2-efficient as possible. Taking constant weight dives for example, having a more efficient descent will generate less CO2 in the body, which should help minimise CO2 narcosis too later in the dive...

Sea mammals have millions of years of evolution behind them to teach them how dive as efficiently as possible. Even the best freedivers only have perhaps a few hundred hours of dive time logged. Do we really believe that we can truly perfect a technique (for whatever discipline) in that amount of time? I don't think so.

Technique also applies to static too. In the early stages of doing a static, I often think: "ok, I'm relaxed now", then when I scan my body I actually find lots of tension, without even realising it was there. Sometimes, wastfeul muscular tension is obvious even to an observer, when you see someone clinging onto the side of the pool in a hunched position.

Same sort of thing applies to diving too... relaxing muscles that aren't actually being used for propulsion. This is something I always try to look out for when diving. It's not an easy thing to do though - it takes a lot of practice.

As well as striving for the most oxygen efficient technique, I think the equipment we use also has a massive bearing on performance, much more than supplements. There are lots of variables to experiment with, such as thermal protection, weighting, position of weights, monofin (or bi-fin) design... Correct me if I'm wrong, but I doubt that any serious research has been done on these things to maximise performance for diving, for eg. academic standard fluid dynamics reasearch on monofin design. New equipment and designs are just waiting to be discovered! Fluid goggles and lenses being classic examples.

I think supplements have their place, but they're certainly no substitute for technique/equipment improvements and most importantly of all... spending time in the water.

"That's all I have to say about that"

alun

ps: On that note... I am now off for the weekend, when I'll be testing out my new Henx monofin. So far I use only Waterway monos, but I think this one will be very good for depth. I may post my initial thoughts about it next week.

[efattah]

Alun,

At this very moment I'm in the process of designing custom monofins for freediving (WaterWay will be building the blades). Suffice it to say that I'm trying some very radical ideas; I did take some fluid dynamics at UBC but doing the math on the fin is a bit beyond me. The way I figure it, I'll try several strange shapes/stiffness-profiles, and see which works best. Hopefully one of them will turn out to be better than the existing monofins, and maybe I can market the result as a freediving monofin. I figure if a world record was set with a strange looking fin, everybody would want it!


Eric Fattah
BC, Canada

[Bill]

> Suffice it to say that I'm trying some very radical ideas

Eric
Did you ever see a propulsion device called Aqueon, or something similar? It was developed by a Pasadena engineer. He had an ad in Skin Diver in '69. It looked like a model airplane, attatched to your shins and had a propulsion hydrofoil that operated in front of your solar plexus. I lost mine in '72. The navy ran some tests on it, by scuba divers, and air consumption was reduced, big time.
Aloha
Bill

[efattah]

Bill,

I don't quite understand the design. Could you sketch a jpg of the design and post it?


Eric Fattah
BC, Canada

[Bill]

Eric
Please excuse the 'art' work.
Bill

[ivan]

hi alun

Im with you pure practice on your chosen event whether it be dynamic, constant, static makes a improvement.

cheers

ps eric are you the guy who is diving to 111m in training

[Alun]

Eric,
those customs monofins sound interesting. I look forward to see what you come up with.

I picked up my Henx mono today... "dissappointed!"
It was meant to come with a Waterway footpocket. Instead it came with some really awful footpockets (Mat-Mas). The size is theoretically ok for me (45/46) which is UK10/11. But they are way too big for me. Does anyone know if it's possible to remove footpockets, and how easy it is to glue new ones on etc... They are so bad, I can't even try it in the water - it would be a waste of time - the blade would probably slip off my feet and end up at the bottom (90m+) . The blade looks and feels nice though, which makes it all the more frustrating!

alun

(I would have put this in a new thread, but it follows on from what I mentioned earlier...)

[Bill]

What's the latest thinking on packing for static? The last I read, the French team was going to try it. The first time I tried, it was so uncomfortable that I had trouble getting relaxed. I just tried again (about 0.25 litres) and there was no discomfort. It seemed to help on the time too.
I've been slowly increasing the packs for over a year now and the Vc measurement is about 10% higher.
Aloha
Bill