I am also concerned about the dangers of  'o2 on'.  When switching to 
a higher (but still safe) ppo2 there is the danger of blackout.  This problem
is being more widely reported, but still not widely anticipated.   Sorry I
missed the earlier thread.

> Date:          Tue, 4 Jun 1996 09:10:28 -0700 (PDT)
> From:          "Peter N.R. Heseltine" <heseltin@hs*.us*.ed*>
> Subject:       Re: What's a *safe* pPO2?
> Tom,
> 
> Many thanks for your reply to my post. I don't know whether you have seen
> the original threads of this discussion.
> 
> My concern is that, with the new availablility of nitrox to sport divers,
> they will be facing the possibility of attaining pPO2s that simply were
> beyond the reach of most a few years ago. Very few were diving on air to
> 186 fsw let alone 218 fsw. While it is clear that tech divers and even
> those trained in tech nitrox will have both the knowledge, training and
> fitness to vary their pPO2s and reasonably assess risk (as you describe in
> your post), I am not so convinced that the average sport diver will do so.
> 
> If nitrox is to gain wide acceptance in the sport diving community it must
> be seen as having reasonable rules that provide a reasonable level of
> safety. Your e-mail to me and many others that I have received on this
> topic, suggest reasonable guidelines that (as you point out) do not seem
> difficult to plan and are consistent with all the training I have
> received. On the other hand, Brett Gilliam, in a letter to Undercurrent
> published in May 96, states that *no-one* has ever suffered O2 toxicity at
> pPO2s less than 1.6, unless they has also exceded their CNS clock. Because
> of his reputation, that statement will be taken as gospel by many who read
> his books, attend his lectures or know that he is now the CEO of Uwatec
> USA.
> 
> If Brett is right, then 'nuff said. But it seems that the perception of
> the knowlegeable dive community is that caution is needed. As a physician
> who advises sport divers on health and diving medicine issues, I am
> concerned that statements like Brett's undermine safety practices and
> possibly mislead. I would like to see the safety caveats that you
> mentioned in your e-mail operationalized in published letters/articles to
> sport divers, when absolute limits are discussed.
> 
> Many thanks
> 
> Peter Heseltine, MD
> 
> 
> 
> 
Richard Ramsden
email: ramsdenr@cs*.or*.za*
Voice: +27 21 790-4917
Cell: 082-9005729
SMail: 11 Plumtree Avenue, Hout Bay, 7800, South Africa

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