Hydro Atlantic Incident 9-30-2012

[danvolker]

Anecdotally... Another part of the 2.0 PO2 is as my associate tells people regarding his commercial diver training. They did a PO2 tolerance test. Candidates were put in the chamber and taken to 2 ATA on 100% O2. If the candidate could handle 30 minutes without toxing, then they could be commercial divers. He doesn't think this practice is still done.

As you stated... Workload I believe is a big part of the equation.

Additionally, some people believe that "work up" dives can acclimate a body to higher PO2 and additionally more adaptation to narcosis effects at greater depths. I bet when you guys were doing routinely deep air dives, that you worked up to it, and progressively pushed the limits rather than going full bore. Yes?

My personal feeling/belief is that your PO2 max is an individual/genetic issue, and can be modified by diet/vitamins/free radicals....nights out parting could be very bad...one reason George was dead against drinking in WKPP exploration team divers.

As to the aclimatization, I don't think so at all for Po2, but for some people, the gradual deepening of dives they do helps them to remain calm at the onset of a strong narc..like what happens at around 185 to 200 feet deep.
Myself personally, I had done 150 foot Hole in the Wall dives almost weekly for years with Frank Hammett. The first HydroAtlantic dive I did --around 165 was nothing for me, and I met George Irvine and Bill Mee on this dive.This was around 1994 or 95......they liked my spearfishing composure and apparent lack of narcotic effects on the dive, so they invited me to do a 280 foot deep dive with them the following week, using some of George's doubles.
This was a huge change in the narcotic sensation.....we dropped heavily negative for currents, and descent was close to 200 feet per minute or more. As I hit the deck of the ship at around 265, I recall feeling so high I was not sure how to swim anymore for a few seconds...George then pointed to a big Blag Grouper swimming overhead, and my hunting mode took over, and the effects of the narc were no longer bothering me....However, I found I could only juggle about 3 thoughts in my head at the same time, and add one more, and one or more of the first three would be lost... I began with "check air constantly/check computer for time/look for fish to shoot"....the problem was once I shot a fish, and was being "wagon trained" by a dozen more big grouper--fish I knew I had to shoot....time and air lost there immediacy....Fortunately, 25 minutes into the dive as we had all agreed to, George had his hand on my shoulder, and then began pointing at my computer--like "hey--it's time!!!!
From that dive on, I realized the big deal of good buddies on deep dives, and on NOT getting task burdened....and if spearfishing, there should really be 2 non-spearfishing and non-task burdened buddies with me...which we always had.

Each of us knew to avoid doing any significant work effort on any deep dive. My use of steel 72's jacked a bit, was enforcement of this--you would not have enough air to work hard, so you would not dare work. Hand over hand was the only way to move against current, and getting out of the current immediately by planning your down-current traverses, was big.

There were some people that would dive with us in the 95 to 96 time span, that never felt good deeper than 200 feet, and we assumed this was an O2 tox issue for them...so they would only go on wrecks where the superstructure was 150 to 200 at most, so they could have fun at the upper areas of the wreck.
Somewhere around 96-to 97, I don't remember exactly, George switched us to trimix and reduced O2, and from then on, the depth was a non-issue ....at least on the deep wrecks and deep reefs we liked. While there was a deeper, 350-400 foot deep reef line we knew of, we decided that the in-ocean deco penalty was to lengthy to be safe--if someone had a problem, the deco would be too big to blow off( shorten), and that made this type of dive to foolish for us....and maybe that is saying something

 

[peterbj7]

some people believe that "work up" dives can acclimate a body to higher PO2 and additionally more adaptation to narcosis effects at greater depths. I bet when you guys were doing routinely deep air dives, that you worked up to it, and progressively pushed the limits rather than going full bore. Yes?

Yes, in my case. I've routinely dived to 75msw on air, and occasionally down as far as 109mfw. All totally incident free. Wouldn't do it now though, and the fact that I'm 10-15 years older is one factor.

In hospitals in the UK pressure chamber O2 treatment is sometimes given therapeutically, and they go up to ppO2 of 3.0. They do get the odd convulsion which isn't terribly pleasant, but they reckon it's worth the risk for the benefits the regime gives.

 

[John C. Ratliff]

Anecdotally... Another part of the 2.0 PO2 is as my associate tells people regarding his commercial diver training. They did a PO2 tolerance test. Candidates were put in the chamber and taken to 2 ATA on 100% O2. If the candidate could handle 30 minutes without toxing, then they could be commercial divers. He doesn't think this practice is still done.

As you stated... Workload I believe is a big part of the equation.

Additionally, some people believe that "work up" dives can acclimate a body to higher PO2 and additionally more adaptation to narcosis effects at greater depths. I bet when you guys were doing routinely deep air dives, that you worked up to it, and progressively pushed the limits rather than going full bore. Yes?

This oxygen tolerance test was also done on all candidates for the U.S. Navy School for Underwater Swimmers in 1967. We all got the O2 tolerance test. It sounds like this is not done for Nitrox divers today though.

SeaRat

---------- Post Merged at 10:16 PM ---------- Previous Post was at 09:35 PM ----------

DandyDon stated:

2: Correct, CO can come from tainted air at the intake - as Peter described, or be produced by a hot compressor internally - as I explained, or in NetDoc's case, it was adding pure O2 to partially full tanks that seemed to have contained oil residue - with tanks heating as filled, the O2 & oil partially combusting. Only in recent years have we been able to test in the ppm range and test to be sure, rather than just trying & hoping.

I don't think that the addition of oxygen, especially under pressure, to oil will lead to the formation of carbon monoxide. Here is an explanation of "Drying Oils" in the presence of oxygen. Note that in the reaction there is no release of CO, but instead a linking of the long carbon chains. So I don't feel that the presence of some oil in a nitrox mix would lead to CO. CO is a product of incomplete combustion.

There was a comment about use of a nitrox mix at less than 60 feet or so, and the consensus was that there was no hazard. The problem is that some of these nitrox divers also carry around cylinders of pure oxygen. This in itself is hazardous, as these cylinders can explode if roughly handled. But using pure oxygen can have disastrous results (convulsions) at only 25 feet; indeed this is what led Jacques Cousteau to turn his back on pure oxygen rebreathers and instead invent the open circuit scuba using air as the breathing medium.

I decided years ago not to pursue nitrox diving; I did not want the complications and the potential hazards.

SeaRat

 

[danvolker]

This oxygen tolerance test was also done on all candidates for the U.S. Navy School for Underwater Swimmers in 1967. We all got the O2 tolerance test. It sounds like this is not done for Nitrox divers today though.

SeaRat

I think with the testing the Navy was doing, part of this went to figuring out the individual depth potentials the divers would have on air or pure O2.....and part went to the Navy creating statistics they could use as general guideline.
After enormous numbers of divers were O2 tolerance tested, the 1.6 PO2 number became one considered "statistically safe" on a dive where no intense work effort was being performed. And the 1.4 PO2 level became a much more conservative limit, based on this inherent fudge factor.

So Nitrox divers never come close to the O2 levels experienced by the NAVY divers in the testing scenarios....
Tech divers however, could gain some benefit from being tested, particularly the ones pushing the envelope after more extreme tech dives. This, not so much for the average tech diver, but so that the tech divers with uniquely POOR O2 tolerance, would discover their issue, and realize they would forever need to modify their O2 use as far more conservative.

At issue for a group of tech divers doing one of our 280 foot deep wrecks or reefs off of Palm Beach, is that a massive amount of nitrogen and helium can be dumped at the 20 foot stop, using pure Oxygen. The decompression effects at 20 feet on pure O2 create a larger gradient to pull out the inert gasses for this, than you get with a 30 foot stop and use of 80/20 Oxygen. Some divers mistakenly think the 80/20 mix is safer, in case they don't hold the stop depth well, yet tech diving should not be attempted by those without the very basic skills of holding a stop depth....and a few seconds off the mark is not going to cause an enzymatic shutdown--that is a process that takes a great deal longer.
the bigger issue for the tech diver, is what they might do should they find they ARE having a DCS issue. The pure O2 with it's bigger gradient, is much more effective at resolving the DCS event, and if the diver has to get out of the water, staying on the pure O2 is still effective on the surface as everyone knows--while 80/20 gas is not effective at all for this, given the gradient is then much too low.
Tech diving offers many, many issues to complicate the discussion.
In the case of this greater Nitrox and recreational discussion, it is much simpler. A Nitrox diver staying in the recreational diving mixes of 32 or 34 %, are not going to be at risk for toxing, on any dives shallower than 100 feet....When they decide to begin diving deeper than 100 feet, many new variables begin to come into play, and more training, and more options need to be considered...for instance, GUE would mandate that the "smart" nitrox diver desiring to do a 120 foot dive, would have gotten the training so that this nitrox diver would do the 120 foot dive, with 21/30 Trimix. The benefits include sharper mental functions, from acute lessening of narcosis for most divers, and on off-gassing, the helium will actually clear out of the diver's body much faster than nitrogen will during the surface interval...meaning the second dive will have this diver "cleaner"....the flip side of this, is that this diver can't do a high speed ascent as could be stupidly done on air or nitrox, typically with no ill effects....with the 21/30 trimix, the diver does need to go a bit slower, and with more frequent stopping...though even just one minute of a stop doesa a great deal with helium....this is all easy for a diver with the simple training for this. And the training "needed" for using 21/30 really is not much more complicated than what is needed for Nitrox.

 

[Johnoly]

....the flip side of this, is that this diver can't do a high speed ascent as could be stupidly done on air or nitrox, typically with no ill effects.....

This is a very important quote because as that He leaves the tissues, it will most likely be replaced with O2 and putting the diver in danger. Like you said, Trimix has it's place in diving, but it takes detailed training just like nitrox to understand it's use. I also think the discussion of knowing the effects of an OxTox hit and what it looks like is good, so divers understand when it happens. The whole effect of "work" at depth is something our dive computers can't even calculate accurately and I really watch what kind of fight I want to get into below 110 and if the fish is worth the risk.

 

[PfcAJ]

Oxygen toxicity has high inter and intra subject variability. Just because you don't have a toxic event at a ppo2 of x.y doesn't mean you won't have a toxic event at that same ppo2 a week later. That little tidbit kinda invalidates the idea of 'tolerance'.

 

[ianr33]

This is a very important quote because as that He leaves the tissues, it will most likely be replaced with O2 and putting the diver in danger.

Huh??

 

[danvolker]

Oxygen toxicity has high inter and intra subject variability. Just because you don't have a toxic event at a ppo2 of x.y doesn't mean you won't have a toxic event at that same ppo2 a week later. That little tidbit kinda invalidates the idea of 'tolerance'.

Absolutely!
And the amount of CO2 you are creating during the dive, is certainly variable even beyond workload...it is not enough that you would just try not to work at all on the dive...there will be times your metabolism runs hotter, and you put out more CO2....times when your Heart Rate will be more elevated due to either pre-dive exertions or mental/emotional stresses...and the amount of CO2 in the deep diver's system will gave a major effect on toxing as you approach the 2.0 level or beyond.

Just in case I did not make my message on this clear before, I am VERY AGAINST divers running above a 1.4 PO2 level, with us knowing what we know today. I am also dead set against divers using Nitrox for dives to 120 or 130 feet or deeper.. I think that is something that does need addressing, because there are Nitrox divers that think this is a good practice.

 

[boulderjohn]

This is a very important quote because as that He leaves the tissues, it will most likely be replaced with O2 and putting the diver in danger.

Are you saying that He occupies space in the tissues, and as it leaves it creates empty space that has to be filled by something, and that something will likely be O2? I am just trying to understand what you are saying.

 

[danvolker]

Huh??

Well, what I had been talking about was how Nitrogen can super-saturate in the blood quite well, whereas Helium busts out of solution very quickly.

supersaturation example....a problem forces a tech diver from 280 to the surface in one minute ( 300 ft per minute ascent). On air, this diver may be able to instantly drop straight back down to 100 feet, and never feel any symptoms of bubbling (DCS) because the nitrogen was BEING HELD IN SOLUTION) ... it was super saturated, but had not yet begun leaving solution( forming bubbles).

In contrast, the Trimix diver with 30 to 50% helium mix, would experience massive bubbling by the time they reached the surface, and they may not have even been physically capable of returning to 100 or 200 feet to get the bubbles to resolve.

To be clear, tech divers are NOT supposed to have problems that pull them from 280 to the surface in a minute...but the example does illustrate a major difference between using air or using helium.

Also...if the deep air diver does the correct ascent rate, and does a 2 hour surface interval, and the Trimix diver does the same bottom time with correct ascent rate and correct stops for trimix....two hours later, the trimix diver should have cleaned out much more inert gas during this surface interval, than the air diver. Helium leaves the blood faster than Nitrogen.