How did old-school deep air divers avoid ox tox hits?

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Yes. Very conservative, and another KEY point I'm not seeing above is this:

OxTox is NOT just a function of PPO2, but TIME at exposure. It's not like spending 2 minutes at 1.8 is going to cause OxTox, or even 10 minutes at 2.0 is unlikely to cause Tox. These key points are left out of basic Nitrox, and even Advanced Nitrox, and cause many people turmoil, when they feel like they must "Violate" the MOD to either make a rescue, or recover something which might put them at a very high PO2 (1.8 or 2.0 even)

My associate John Chatterton tells me that when he was becoming a commercial diver, he was put in a chamber, and dropped to a 2.0 PPO2 for 30 minutes to see if they toxed. He says, "If you toxed, you couldn't be a commercial diver. If you didn't, you were good." Obviously John didn't tox, since he was a commercial diver in NY for many years prior to the Shadow Divers days. Also, 1.6 PPO2 for Air is about 218 feet.

So... Remember this the CNS Clock for 1.6 PPO2 is 45 minutes on a single dive and for a 24 hour period. For most people, 10-15 minutes won't cause tox. Most of John's dives on the Uboat were less than 25 minutes of bottom time, at depths above 215. Brett Gilliam's record breaking dives were bounces.

If you ask me... The reason 1.6 is the MOD is because your clock ticks off very quickly at that PO2, which could greatly effect your subsequent dives, or an extended dive with longer decompression times.

For more information on CNS Ox Tox... read Steve Lewis' (Doppler) article here on SB. http://www.scubaboard.com/forums/content/357-daily-limits-cns-oxygen-toxicity.html

Absolutely right.... In the Jane Orenstein tech diver student death, Jane breathed pure O2 accidentally ( due to what many would call the negligent instructor watching her) from 100 feet to 20 feet, through the 100 to 50 foot traverse, then 50 foot stop, 40 foot stop, 30 foot stop, and then when headed for 20 feet, she blacked out and sank, with the instructor just watching her ( he was her buddy also). Point being, she was on pure O2 at 100 feet, and did not instantly die.
 
Although after 50 years of diving, I'm certainly "old" school, my deepest dives on air were only to 200 ft. My experiences cannot be translated to others due to the differences in individual response to both narcosis and oxygen toxicity. I gradually worked my way deeper and deeper over a few months time and tested my response to narcosis. I was also doing about 300-350 dives a year when I did my deep dives over about a 2 year period. The purpose was to film for an episode of my cable TV show on "deep ecology." One day I average 180 ft on three dives (200, 180 and 160 respectively). Most days I would only do one dive to 200 ft and the rest relatively shallow.

I found that I could be pretty functional at 200 ft... narced yes, but still highly functional (measured by ability to locate subjects, frame them well and film them as they moved). I never experienced any indication of ox tox, but I did not remain at my maximum depth longer than a few minutes and did not exert myself at any depth very much.

Today, just a few years later, I could be narced sufficiently at 120 ft to not feel totally comfortable and would have to resume a period of training to resume dives like that again. However, there is no longer the need to do so. I filmed what I needed to get back then and now focus on maximizing bottom (and filming) time.
 
... OxTox is NOT just a function of PPO2, but TIME at exposure...

Add physical stress including workload and thermal. Recreational oxygen toxicity limits are extremely conservative, especially given the comparatively low stress and exposure times. Confirmed OxTox hits are nearly unheard of in military or commercial diving -- though supervisors are very alert to possible symptoms and pull divers off the mask at the slightest suspicion.
 
Divers who went into tox early were sidelined from doing Sat. It was an incredibly unethical practice.

I don't think so at all. I have sidelined many divers who I felt were high risk. I pulled you out of Sat when you puked in your helmet, in my opinion toxed, in yours HPNS - but mine was the opinion that counted.
As Akimbo says - we look for signs and react. If we can react before the dive, we will.
 
... I have sidelined many divers who I felt were high risk. I pulled you out of Sat when you puked in your helmet, obviously toxed...

I'm confused. I have never been around a sat with PPO2s above 0.8 ATA in the water, usually more like 0.3. Granted, it's been a while since I was offshore but why bother unless you are running crazy deep excursions (diving well below the saturation holding depth in the deck chamber)? Deep bounce dives with a small bell system is another matter but I didn't think much of that was done anymore.

Barfing in a hat is a good reason to pull a diver even if they are in 30' on air. Burping often gets the mask yanked, at least for 10-30 minutes. All the barfing in hats I have witnessed had more to do with excessive Tabasco on breakfast or the previous night's celebration than gas mixes.

---------- Post added May 16th, 2012 at 10:12 AM ----------

In my transition from Air to Sat diver in 1989, we were put in a chamber and exposed to increasingly higher PPO2 to determine what our individual tolerance was...

Are any military or commercial diving schools still running Oxygen Toxicity tests? I heard the US Navy stopped years ago concluding they were not very predictive of individual sensitivity. It is ironic that they would test you before going into sat since Sur-D-O2 usually exposes divers to far higher risks.

Personally I am glad I did the test for the self-confidence factor… but it was only my second chamber ride so it was still fun at that point.
 
No, the nitrogen just made you more narced as you got deeper :) You could say it made some people calmer and more relaxed, though essentially losing half of their functional IQ.

When George Irvine, Bill Mee and I were doing our deep air dives between 93 and 1996, prior to George bringing Trimix to us, we did many hundreds of dives to as deep as 290 feet, on air.
The belief we had at the time, is that each individual had their own unique tolerance for high PO2's. Some divers could not really handle much deeper than 200, others could go considerably deeper. The entire enzyme and reaction cascade that would create the seizures, would sometimes be preceeded by a distinct malaise. Some divers believed they could feel good down to a certain depth, and then they felt this was as deep as they could go....George, Bill and I all felt comfortable to 280 or 290, though the narcosis was so intense that you had to be careful not to add too many thoughts into your head beyond checking time and remaining tank psi....I could handle three basic concurrent thoughts at 290...hunt( look for fish to spear), check time, check air.....If I shot a fish, stringing it meant I had added a 4th, and this would mean losing track of time or psi or both.....fortunately, we had a strong buddy system, and I was the only spearfisherman--so if I lost concentration on duration, Bill or George would swim up and tap on computer.

I had one incident where I shot an 80 pound grouper on a 250 foot deep wreck off of Fort Pierce, where the fish fought me as I tried to hold it at the spear, and use the knife to finish him off...the exertion level became so high that after 20 seconds of this, I felt a sudden massive shutdown coming on, in myself, so I hit my inflator and rocketed to 100 feet, where I dumped the bc, and then began feeling better quickly...this would have been ox tox, just before it became critical. Not something you would expect would always provide such a warning, but in my case, this was the only time I had not been careful enough to AVOID significant exertion at depths over 140 feet deep.

And this avoidance of exertion was our primary technique to avoid ox tox. Never swim fast, don't get excited, keep heart rate low, etc...I was always taking huge amounts of Alacer Supergram II vitamin C every 3 hours back then, along with 1000 IU's of high gamma Vitamin E, and several other antioxidants... i believed that this was protection for Ox tox, and the enzyme issues created by deeper than 200 foot dives on air.

The more streamlined and horizontally trimmed the diver was( as DIR pioneers, we were always maximally streamlined) , the less work they did moving around, and the less exertion was there to make Ox tox occur.
The less gear you carried, the less drag and less work in water....Some divers would drag 4 big tanks, huge bellowing BC,s and tons of junk with them...they would exert far too much, and were at much greater risk over 200 feet deep ( in our way of thinking) ... We would use double al 80's or double steel 72's, and then have one 20 or 30 cu ft Oxygen pony slung stage style on the left. It was negligible drag in this position and size, so did not effect our swimming underwater. This was for the final 20 foot stop.

Out of about 30 people we dived with back then, there were about 12 of us that were comfortable at 290, and the rest never felt good below 200. There was some talk about ability to get rid of Co2 being quite different from person to person, and that this may have been a key difference in depth potential...George and Bill and I were all doing competitive level aerobic sports, so by definition, we were good at getting rid of CO2. As CO2 levels climb, obviously Oxtox becomes far more likely.

Some blamed their regulators on not getting rid of CO2 well, but I never really bought into that one. I did most of my deep dives with a scubapro mark2 first stage, and R190 second :)


Thank you for this response. This is exactly the type I was looking for. Very informative! Not that the others werent =P
This one in particular just struck me as a great response.
 
A lot of posts have gone into the depth and time angle, but what kept our bottom times short? It was that all we had were steel 72's, aluminum 80's and some got hold of old navy 100's but they were few and far between. So, on a 200-230 foot dive you just didn't have the gas to get too far into deco/bottom time. Dives to 200+ feet were set to 15 to 20 minutes with a few able to get to 25 minutes. Also, all we had was air, so your bottom time and deco were all on air so we had to keep it short.

A lot of this is why the Doria got the rep for being the Mount Everest of diving and why we had to work up to her by doing progressively deeper dives over years. But the only diver I know of who did 250 on air on the Doria was Gary Gentile.

We also learned not to use our legs and to pull along with our hands and fingers - this was way before DIR type kicks, so use of the larger muscles was kept to a minimum. This wasn't to cut down on the Oxtoc issues but keep from silting out and as an attempt to lower our breathing and cut down the SAC rate at depth.
 
The RB Johnson / cory'n /chris shipwreck was about 280 to the sand...we would do this on air for 25 minutes with dual 80's or dual 72's.
Wrecks like the hopper barges at 270 off Singer island were much harder, due to huge currents, which would have us pulling along the steel frame rather than kicking--just too much current until inside it....The RB was normally under a knot current, so we could do what we wanted easily on it.

And for many of our high current dives, we used Gavin Scooters, pulling a torpedo float with at least one scooter, so the boat would know where we were after a 3 mile run at 280 :)
 
As Howard mentioned, in 1982 when I started commercial diving, it was standard for all USN and commercial divers to pass an oxygen tolerance test prior to acceptance into any program. Industry standard was 30 minutes on O2 at 30', in a chamber. In my class we had one guy tox, and he was out. Later conventional wisdom evolved. Vulnerability on any given day was extremely subjective, so the test proved nothing, it was canned.

There was a guy in the early days who died diving one of the NY wrecks on a very hot Nitrox mix. He knew the mix was hot, he tested it on the boat, but he was convinced that he handled O2 better than mortal men. He was diving with Chrissy Rouse in a little over 130' of water, and had like a 50 minute BT. The last time anyone saw him alive his CNS O2 toxicity was later calculated to be like 4,000%, due to PP and duration. He died from ignorance.

Technical diving offered more exposure to O2 than deep air, or so it seems to me in retrospect. For those deep air days, we did a lot of diving, some times deep, but shorter duration as a rule. Nitrogen seemed like the gas we had the most trouble with, at least that was the way pretty much everyone I knew thought at the time?

Modern standards are so conservative, at least in part, because it is virtually impossible to determine if you are having a good O2 day...... or not.


CHeers

JC
 
Then there is the Cousteau dives on the Brtannica back in the 70's. Three hundred seventy FSW on Heilox. The thing is they start from the surface breathing the same gas as they did on the bottom. What's the 02 content of that mix? Must have been a quick swim down from the surface!
 
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