Co2 Toxicity

[gehadoski]

Dear all

I'm not sure if I am posting in the right place or not. I need more information about CO2 Toxicity. Like what is Pco2 the cause CO2 toxicity, what are the symptoms, things of that sort.

 

[knotical]

For diving related, here’s a link to part 1 of an article on hypercapnia and diving. I guess if you need part 2, you could buy his book here, or contact diver magazine and enquire about back issues.

You could also do a Google search on carbon dioxide poisoning, or perhaps ask the question again on either the Ask Dr. Decompression or the Diving Medicine forum.

 

[Mako Mark]

good article,

there has been a renewed interest in CO2 and its effects on divers over the last couple of years with respect to two main areas

CO2 and Oxygen toxicity, CO2 is known to aggravate or bring on symptoms

CO2 and Inert gas narcosis. again a contributing factor that is little understood.

Both these effects have caused a drastic rethink on deep air diving and its merits. I personally have done extreme air dives, but with the emerging information and the contribution of CO2 as a problematic gas, I have also moved away form deep air diving.

It used to be that air was perfectly acceptable, in fact the "ideal" gas for 200 ft dives, but now it is widely recognized that any extended dive below 100 to 130 ft should consider trimix as a better option.

 

[padiscubapro]

although Helium is a better gas for deeper dives there is also evidence that higher narcotic exposure lowers CNS risk..
We must remember we have to balance all the variables, keep the co2 down, keep the po2 reasonable along with exposure time..

There needs to be more study, more divers using hyperoxic helium mixes as opposed to how they have been used in the past (moderate exposures). This MAY increase the incidence of CNS issues..

All the people who have done very deep air dives with high po2s have not had issues with CNS, their problems were narcosis.. exposures that have caused people problems on deco mixes (low inert gas content) seem to have a higher incidence if symoptoms as opposed to the same exposures on a highly narcotic mix..

Am I advocating deep air?.. no! Just pointing out for people not to follow blindly.. in my book that means backing the acceptable po2 off a bit for dives with He..

 

[cornfed]

although Helium is a better gas for deeper dives there is also evidence that higher narcotic exposure lowers CNS risk..

Do you have any references?

 

[padiscubapro]

There really isn't a whole lot in print but there is evidence through accidents and record dives that it needs to be quantified..

All the record deep air dives (over 400 fsw) the divers never reported any CNS issues (I'm not saying their might not have been some present, but there were no siezures/convulsions or issues reported). Lots of the older deep air diver routinely ran exposures in the range of 1.8 or higher on working dives without major cns issues (I'm not saying there were none but I am unaware of any incidents).

Now on the flip side of the coin there have been plenty of CNS related incidents with po2 exposures in the same range with low narcotic mixes..

This is why I said study has to be conducted (and why not be a little cautious). In discussions I have had in the past with others and various theories I have heard, they basically come down to nitrogen acts as a depressent and slows the nervious system down, while oxygen proplems appear to be caused by the system being excited or acclerated, so it appears that there is SOME level of offsetting of symptoms, just like it appears adding nitrogen to heliox mixes for very deep dives offsets HPNS..

I hope some scientific studies are done because too many people are jumping into high heliumhigh oxygen mixes without any real data on side effects..

Personally I have done dives many years ago with PO2 exposures of greater than 2.0 (as a bottom gas) without any problems, but have experienced some symptoms on deco mixes with lower po2s than that.

 

[modlin1]

Hi I have been around diving since 1954 including over 20 years in the Navy. Did some speciality and a lot of different mixed gases some are way out of the realm for the sport diver. However the Navy always started with a check of the persons individual Oxygen toxicity. So you had a general idea of where you tox out with PO2. However I know it was found to change for many reasons. The military was always pushing the envelope. Now that I am considerably older and have gotten out of shape (knees went bad two knee replacements)with a higher degree of body fat I try to error on the safe side when diving. Do you know of any new tables for PO2 that take into account body fat. Thanks modlin1