Nitrox workshop dings - Divers Alert Network

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Rubicon Foundation Archive (http://rubicon-foundation.org)VI. Final Discussion and Workshop Recommendationsmaterials in the product line. I wonder whether this message is a little bit too broad in howit's stated now.D. Kesling: Add "to date" because equipment is going to change.S. Angelini: The history of use is always "to date."B. Hamilton: I appreciate what Sergio is saying, but I wonder if we could say that standards forscuba equipment as of the date of this meeting don't include the exotic materials you'retalking about?S. Angelini: There is between two and three years of experience with probably hundreds ofdives. These materials are lighter and are meant for traveling. On travel is when most of therecreational nitrox diving is done. One could say that there is a history of data. I don't wantto push it too far because these recommendations are being written for a purpose. Although Iwould certainly like to get the liability off of our chest and use something like this, I don'twant to be unfair to the end user.B. Oliver: Michael, I have a suggestion that might help. You might just add another sentencethat says that the level of risk is related to specific equipment configurations and that youshould rely on the manufacturer's recommendations.M. Lang: Sergio, does that put you at ease?S. Angelini: Absolutely.M. Lang: Alright. With no more discussion on this, all those in favor, a show of hands, please.Very good.D. Richardson: Would it be appropriate to add a statement that when an individual's CO2retention status isn't known, it seems the limit of 1.6 atm is appropriate with open circuitscuba? There was a session on CO2 retention for open circuit scuba at 1.6 atm that wouldseem an appropriate limit if we're not going to be screening for retention.M. Lang: Let me ask Dan to respond. Is that a statement you'd want to make?D. Kerem: Right now I wouldn't change the limits, but maybe encourage the mentioning of theratio of CO2 retention in the curriculum.D. Richardson: I'm suggesting a separate bullet.M. Lang: A separate bullet is alright.T. Mount: My concern here is that we may be indirectly implying that we should be testingeverybody's CO2 retention. Most facilities don't have the ability to do that.D. Richardson: I'm saying just the opposite. That we shouldn't be testing, there is no reason to.Basically, you're setting a limit. We have a history of use to that limit. We're not screeningfor CO2 retention, but that's not necessarily a problem using open circuit nitrox at 1.6 atm.Can we say that?B. Wienke: We ought not to be making medical judgments because none of us, except for a fewpeople in this room, are qualified to make such statements.D. Richardson: There was medical evidence presented though that would suggest it's not aproblem. Why was the question even raised and put on the agenda? It should be addressedby this workshop.M. Lang: That's true. Some bullet about the CO2 retention issue needs to go up here. Dan, didyou want to finish any comments?D. Kerem: I can't argue with the fact that the 1.6 atm limit seems very safe. Apparently, evenCO2 retainers get away with it. Notwithstanding the anecdotal cases that we still have ofpeople convulsing on apparently safe PO2's, I would at least educate people to this189
Rubicon Foundation Archive (http://rubicon-foundation.org)Lang (ed.): DAN Nitrox Workshop, Divers Alert Network, November 2000possibility. Suggest to the guys who finish the dives with a lot of gas in the tank after thebuddy emptied their tank to perhaps take more conservative measures with the use of the PO2limit.B. Hamilton: Could we add to the bullet "based on the history of use and assuming no excessiveCO2 accumulation"? That deals with heavy exercise and with the CO2 retainer and it makesme a lot happier.A. Marroni: In one of the two papers that we are referring to, it is said that in the case of theunknown CO2 retainer, a maximum PO2 of 1.4 atm is advised. This has been written and issomething that we should consider.R. Moon: I would make some statement about the possibility that there is physiologicalvariability and susceptibility to CNS O2 toxicity, but that the methods do not yet exist toreliably predict whether somebody is in that subgroup. Simply make the point that there maybe people who are more susceptible for whom 1.6 atm is not appropriate, but at present thereis no reliable way to identify such individuals.M. Lang: Do we want to necessarily tag in the CO2 retention, link it with the maximum PO2 of1.6 atm, or should the CO2 retention be framed as there not being an excessive problem withit as a separate bullet?R. Moon: I would make it a separate bullet.D. Richardson: For open circuit.B. Gilliam: Let me suggest that we're peeling back the layers of the onion pretty far now. If wegot into this same discussion of air, we could be talking about PFO's and all kinds of subbullets.Yes, there are going to be exceptions from the general population rule, but we'regoing way overboard here to try to identify these at such a level right now. From Dan's talk,he identified CO2 retainers as being maybe five percent of the population. We don't havescreening methods to even begin to identify them. This is something that is beingexcessively minutiaed here.M. Lang: Simply stating that CO2 retention might be an issue doesn't say much at all.B. Hamilton: Didn't what we said about using the NOAA limits cover that? Can we just deletethis whole bullet?M.Lang: Which bullet?B. Hamilton: The one about using the NOAA oxygen exposure limits. That's the one that says1.6 atm and a lot of other things too. Does that not meet the requirement right there?M. Lang: For CO2 retention?B. Hamilton: No, just NOAA limits.M. Lang: We're going to leave unchanged what we already agreed upon as consensus statementand that was a maximum PO2 of 1.6 atm. Now we're dealing with the CO2 retention issueand it's been suggested that we create a separate bullet for that.A. Marroni: I would suggest to not mention it here unless it is implicitly defined for open circuitnitrox. Otherwise, we leave the door open for rebreathers and that's a different storyaltogether for which we would have to add multiple other bullets.M. Lang: The overarching factor here is open circuit, entry-level, recreational nitrox. You'reright in pointing out that maybe we need to put a qualifying statement to that effect up front.T. Mount: There are several issues that get involved here. Why do we want to create a liabilityby talking about CO2 retention in the first place? Leave the maximum PO2 at 1.6 atm. Thatis a recognized limit. We don't have a way to screen CO2 retaining divers who would get aheadache all the time, therefore reduce their PO2 limit. That's not practical. One other thing190
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