Can O2 hits reoccur on a dive

[scuubaadoo]

I am nitrox, adv nitrox and deco procedures certified. I was wondering if the mechanisim is purely mechanical as Ian implied or if there might be a "metabolic" reaction that mimics say pain medication, the more you take the more your body tolerates it. The body has a wonderful ability to adapt, so it might be able to adapt to higher O2 pp for a short period of time. Again thank you to those that answer with a thoughtful response.

 

[Thalassamania]

You started off by asking:

Got to talking with a diving buddy and this question came up. If you are wearing a FFM , have an O2 hit and it passes, do you have to cut some time off ascent to get to the surface quickly b4 it happens again or now that you've had your hit are you "tolerant" and can take your time coming to the surface. Side question are so "tolerant" because you have already had any hit your going to get, that you can continue to dive.

For the record, The answer to this is NO. You do not build up a tolerance. There are a lot of unknowns concerning oxtox. You can do a O₂ tolerance test one day and pass and yet flunk it the next day. The Navy's approach was (is?) you take the test (100% O₂ at 60FSW in a chamber) and if you flunk you're out, now and forever.

Then a bunch of us expressed our amazement (with some attempts at humor I’ll grant you) that you don’t seem to see a convulsion as a serious problem, as long as you’re wearing a FFM and don’t drown. That, combined with the thesis of adapting to a high ppO2 led DivingDoc to assume that you’d never taken a NITROX class. But you tell us:

I am nitrox, adv nitrox and deco procedures certified.

If that’s the case, and I’ve no reason to assume that it is not, you need to take a cold hard look at what the instructor(s) of those courses “taught” you (or just to be fair, possibly your ability to learn) because somewhere along the line you were seriously short-changed.

An O2 seizure is the bodys mechanism to stop the input of more damaging oxygen.Stop breathing for a while and you cut off the oxygen supply.
A seizure indicates that the body has reached its limit. When breathing resumes after a few minutes I would imagine that you are still very close to that limit. (Backed off a little but still very close) If the PO2 is not immediately reduced the chance of seizing again will be very high. IMHO

Ian is absolutely correct in that either a significant ascent or a switch to a significantly leaner mix will almost always relieve the symptoms. But his idea that the seizure is an adaptive response to a high ppO2 is without support, or just not quite worded the way he meant it.

I was wondering if the mechanisim is purely mechanical as Ian implied or if there might be a "metabolic" reaction that mimics say pain medication, the more you take the more your body tolerates it. The body has a wonderful ability to adapt, so it might be able to adapt to higher O2 pp for a short period of time. Again thank you to those that answer with a thoughtful response.

The mechanism is “mechanical”, in the sense of being caused by a high ppO2 and relieved by lowering the ppO2, it is not (as you call it) metabolic, there is no adaptation or build up of tolerance due to exposure.

I don’t mean to give you a hard time or put you down, what I say, I say out of a very real concern for your safety. Oxygen convulsions are a serious condition. I have never experienced one, despite my routine use (in years gone by) of oxygen at 2.0 ATA. I have witnessed oxygen seizures in others, and that is a bad scene, all the way round, FFM or no FFM. I still use deco mixes to 1.8 ATA and dive operationally to 1.6, but that comes from the experience of decades of using oxygen at the higher _ppO₂ that was SOP back then.



Please reread the texts from the courses that you took and look back over your notes and/or speak with the Instructor(s), because something went very wrong there. I’m sorry to say that your questions are unexpected coming from someone who has take NITROX, Advanced NITROX and Decomression Procedures. In another sense, there are no stupid questions, especially concerning life threatening problems, so let’s be thankful that you had to the good sense to ask the questions here and thus did not have to discover this gap in your training in of those horrible “Oh S***!” moments.

 

[Gene_Hobbs]

The Navy's approach was (is?) you take the test (100% O₂ at 60FSW in a chamber) and if you flunk you're out, now and forever.

Screening for oxygen intolerance in U.S. Navy divers.
Butler and Knafelc 1986
RRR ID: 3046, PubMed ID: 3705251

...Conclusions from this paper are: Screening for oxygen intolerance is complicated by intraindividual variation in oxygen tolerance; U.S. Navy diving using 100percent oxygen during the period studied has had an acceptable safety record according to the data on record at the Naval Safety Center; the OTT as currently administered by the U.S. Navy does not identify all individuals who are relatively susceptible to oxygen toxicity; those individuals who do fail the OTT are unusually susceptible to oxygen toxicity; and because of the need to continue to identify these unusually susceptible individuals, the OTT should continue to be administered to U.S. Navy diver candidates.

Screening for oxygen sensitivity in U.S. Navy combat swimmers.
Walters et. al. 2000
RRR ID: 2358, PubMed ID: 10813436

...Many factors other than individual sensitivity to HBO2 may contribute to the occurrence of O2 toxicity episodes during combat swimmer operations. The authors conclude that O2 tolerance testing of U. S. Navy SEAL candidates is not a useful screening test and recommend discontinuation of this test.

Test are no longer administered.

 

[Thalassamania]

Have O₂ tollerance tests be scrubbed for all MOS? Just for combat swimmers? How about fleet divers?

 

[Gene_Hobbs]

Have O₂ tollerance tests be scrubbed for all MOS? Just for combat swimmers? How about fleet divers?

No longer being done at all.

 

[Thalassamania]

Is anyting being done to identity those individuals who are unusually susceptible to oxygen toxicity?

 

[Gene_Hobbs]

Is anyting being done to identity those individuals who are unusually susceptible to oxygen toxicity?

The simple answer is yes, the longer answer is not so much operationally as much biochemically.

If really interested... The current research was talked about some in the GUE "The Mysterious Malady: Toward an Understanding of Decompression Injuries." DVD with the researchers interviewed (Piantadosi). Abstracts are also presented on these topics every year at the UHMS meeting. Those abstracts are posted in the Rubicon Research Repository.

 

[Tonio Anastasi]

Oh gee ... we can continue the dive as soon as I stop twit, twit, twitch, twitch, twitching ... ah ... that's it, now were was I.


What the F!?[/quote

Thanks for that I needed a good laugh.

 

[scuubaadoo]

not to take this thread somewhere it was not intended, but I feel I need to answer your insulting tone. Your first reaction was "what the F!@#", very educational. My point was is there a metabolic response or is it strictly mechanical. The fact that I mention a FFM is for the assumption that drowning was not the issue at hand.

As for my educators I have look at many book on Nitrox, Adv Nitrox and Deco form the major certifing agencies, none approach it from the medical aspect, yes thet all talk about pp rising as depth increases, heck this is OW stuff. If you know of any agaency that has a book that covers the issue , please enlighten me. I will be glad to read anything that may help. And yes the standard answer is abort the dive, but questioning conventional answer can lead to more questions and hopefully more answers.

Yes I am very appreciative of Doc and Ian for answering without the need to put me down. BTW Please do not hide behind others by saying "Then a bunch of us expressed our amazement ". Do you now speak for eveyone, or are you holding conversations about me without the decency to ask me to participate?

Go have all the fun you want, as I have said this is no place to learn, unless you already know it all and want every one to pat you n the back because you follow the convetional wisdom of scubaboard.

 

[Thalassamania]

If you know of any agaency that has a book that covers the issue , please enlighten me. I will be glad to read anything that may help. And yes the standard answer is abort the dive, but questioning conventional answer can lead to more questions and hopefully more answers.

Try the NOAA Manual or the U.S. Navy Manual or query the Rubicon database and read the original papers. I learned something from Gene in the interchange, did you?

Go have all the fun you want, as I have said this is no place to learn, unless you already know it all and want every one to pat you n the back because you follow the convetional wisdom of scubaboard.

With all respect that is due you, I took you for a Troll and was just having fun with the Troll (at least some of us saw it as fun.

When I found that you were serious, that you'd completed NITROX, ADVANCED NITROX and DECOMPRESSION PROCEDURES and that you're asking questions that were appropriate to an entry-level diver, I changed my tune. I remain seriously concerned about your safety. Please read more and be sure you understand or get some competent instruction.