Air Breaks and CNS

[Superlyte27]

I had an idea. It seems like just last week there was a post by a college student looking for a diving related experiment to run, and those type of posts come in every so often. It seems like it would be possible to get some idea of how air breaks influence this so-called clock with an experiment using lab rats or mice.

I'm thinking of something like keeping them in a small chamber with pressurized O2 (flowing, to keep CO2 from building up), and observe them for seizures. A range of pressures could be tested, anywhere from high enough to seize very quickly, to just high enough to reliably cause a seizure before they die from pulmonary toxicity. Once the range is established, experiments could be repeated within the range but with air breaks of varying lengths inserted. Multiple rats would be needed I'm sure, so this could also give data on individual variation in susceptibility to CNS.

It wouldn't give us any better understanding of why CNS occurs, and rat physiology probably doesn't directly translate to ours so that we'll know exactly what an air break schedule should be once the report comes out. But it seems like it might teach us some rough idea about the decay rate, if there is one.

Thoughts or opinions? Does it sound useful? I'm thinking about posting this in a thread of its own, maybe it could shape up with all the details, maybe someone could run it someday.

The problem with this is that what happens in the chamber, stays in the chamber. What I mean by this is that the chamber does not mimic what happens in the water. It's the reason we quit doing Oxygen Tox test. Back before the late 90's most commercial divers had to do 100% O2 at 60' for 30 minutes. I've conducted this test more than 100 times on 100's of divers. To this day, with more than 300 divers, I've never seen any diver tox at 60' for 30 minutes on 100% O2 in a chamber. However, this test, if conducted in water would certainly have a different outcome.

 

[PfcAJ]

True, but it can shed light on the subject, and potentially pave the way for more advance experiments. Since the entire thing is so poorly understood, anything would help at this point.

 

[kotik]

I've read a few studies that are procedurally similar to the one you envision, but they used implanted electrodes for EEG. Cool stuff.

I'm not sure what would be a good method for observation-- a video monitor doesn't sound completely reliable, but having to do brain surgery on a population of rats to attach the electrodes sounds like a pretty high barrier to be able to run the experiment. Maybe external electrodes could detect the EEG signals? Sounds like a good problem for the college kids to work out.

The problem with this is that what happens in the chamber, stays in the chamber. What I mean by this is that the chamber does not mimic what happens in the water. It's the reason we quit doing Oxygen Tox test. Back before the late 90's most commercial divers had to do 100% O2 at 60' for 30 minutes. I've conducted this test more than 100 times on 100's of divers. To this day, with more than 300 divers, I've never seen any diver tox at 60' for 30 minutes on 100% O2 in a chamber. However, this test, if conducted in water would certainly have a different outcome.

We humans take experimental data in a controlled setting all the time in order to learn about phenomena we encounter in the real world. For one example, the first serious research into DCS was done on goats in a lab, and since then we've developed various models to explain the observations. We don't rely on the models so much that we take our bodies to the exact bent/not bent line that a model generates, but they're still useful I'd say. We just stick in some padding.

What if we got some data and it pointed strongly to something? If we find that air breaks don't seem to really do anything at all then some people might give up their false sense of security. If we found that a short air break has a big effect for some reason, maybe the spare air will finally gain legitimacy in tech diving? :cool2:

Well, there's one vote of "cool" and one vote of "not gonna tell us much". Is the idea interesting to anyone else? Either positive or negative? If not, it's probably not an important enough question to sweat over...

 

[boulderjohn]

For one example, the first serious research into DCS was done on goats in a lab, ...

Just to be an obnoxious PITA....

John Haldane used goats in the creation of his decompression tables, but the first serious work on DCS was done by Paul Bert long before that. It was Bert who first identified nitrogen as the culprit in DCS, and he is also the one who discovered that slow decompression was the key to preventing it. He did his experiments on dogs.

Bert is also responsible for the discovery of CNS toxicity, and for that reason it is sometimes called the Paul Bert effect. that experimentation was done on a variety of animals.

Of course, that minor correction does not affect the point of your post.

 

[PfcAJ]

Upgrade my vote to "potentially enlightening and worthy of further consideration."

I hope there is a bulk discout for lab rats. Costco?

 

[kotik]

the first serious work on DCS was done by Paul Bert

I knew I'd end up sticking my foot in my mouth quoting history without checking it over first...

Thanks, the correction is welcome and not PITA at all--

 

[GrimSleeper]

I'll throw in a vote for 'be interested to see the results, while cautious about how applicable to real-life wet O2 exposures they'd be', if that helps. I've done plenty of very satisfactory decompressions using VPM, the underlying theory for which was tested, in part, by observing bubble-growth in agar jelly if I recall correctly. That seems to work, so why not see if we can learn something from toxing rodents?

I always wondered how Haldane's goats equalised...

 

[ajduplessis]

Reducing PPO2 in bottom gas and less rich deco gasses will also lower CNS risks. You don't have to deco on 100% all the time, 60-70 works well on long deco schedules.