I'd like to comment on this:
>On 5/1/98 1:36 PM, wwm@sa*.ne* wrote:
>
>>In speaking to a friend of mine who advises insurance carriers I learned
>>that some new requirements may be coming down on the tech diving
>>industry.
>>
>>It seems that given the shocking record of accidents and fatalities of
>>late one means of diminishing some of the risk may be to require Stess
>>testing in conjunction with PFO and oxygen tolerance testing.
One must ask the question, if screening for a particular condition:
Is it relevant?  For an answer re PFO, see below.  However, one thing
that is certain is that oxygen tolerance testing will give no indication
as to the susceptibility of an individual to get hit.  The
susceptibility varies between individuals and between measurements on a
given individual on different days (as is commented below; see also
McDonald's book on Oxygen and the Diver).
>>
>>In my opinion it is very wise to perform these tests regardless of
>>whether they are a requirement or not.  The commercial diving industry
>>considers this form of testing to be a mandatory prerequisite. Tell me
>>why we shouldn't follow suit?
Because you are giving all sorts of ill-informed persons (the assessors
in the insurance industry) a very big stick with which to beat you.
>>
>>Bill
>
>Bill -
>
>I was going to respond to this when Dan Volker first posted the idea of 
>mandatory PFO screenings.  In principal, it's a very good idea -- 
>especially for any kind of decompression diving -- but lets put a 
>practical framework on the PFO issue:  
>
>First, based on DAN statistics, PFOs are present in an estimated 10%-15% 
>of the population
No, in fact a paper in the Am.J.Cardiol. puts the figure at 27% at
autopsy.  Other papers do likewise.  I can give all the references if
you want them.
>
>Second, diagnosing one requires -- at a minimum -- an echocardiogram with 
>contrast (aka a bubble echo) which costs approximately $1,000.00.  (I 
>know -- I just had one done.)
Well, if you must get an expensive cardiologist, you deserve all you
get.  Many cardiologists use aerated saline solution, which is cheap and
gives very good contrast.
>
>Third, even bubble echoes will not diagnose small PFO shunts because of 
>interference from the rib cage. (This was surprise info from my 
>cardiologist while the bubble echo was being performed.) To truly rule 
>out a PFO, you have to get an endotrachial bubble echocardiogram in which 
>a miniturized echo device is actually lowered down your throat to produce 
>an internal picture of blood flow through the heart.  I didn't look into 
>the cost of this procedure, but since it involves intubation and 
>anesthesia, I think it's safe to say that it won't be simple or cheap. Do 
>you know of anyone who's taken it this far? 
Transcranial Doppler is as good.  There are several papers which
indicate this fact.  You don't require anaesthetic or anything down the
throat.  The test is simple and straightforward and detects all shunts,
not just those which are intracardiac.  Which brings me to the question
as to why detect a PFO?  If you look at the paper by Knauth et al. in
the British Medical Journal, you will find that they detected 11 divers
in whom the PFO was "haemodynamically significant".  In only 3 of the
divers did they find that there were any significant MRI lesions.  Now,
I quite accept that they didn't look in the spinal cord, but nonetheless
it is true to say that, if roughly 27% of divers have PFOs, the diving
community is going to shrink quite unnecessarily if all those who have
PFOs are ruled out of diving.  27% of divers do not have problems.
>
>That said -- it you can afford it or have medical insurance that will 
>pick up the tab, it's not a bad idea. I though it was important to do 
>before starting mix dives and squeeked mine through my PPO insurance, but 
>it wasn't easy.  As for Ox tolerance testing -- not sure it would show us 
>much since the ox tox threshold varies so much from day to day and dive 
>to dive even in the same individual.
>
>Perhaps rather than make it mandatory, a bubble echo should be strongly 
>recommended by the tech certification agencies and this recommendation 
>should be backed up with a full and medically graphic description of what 
>can happen to a diver with an undiagnosed PFO on a deco dive.
Most of the time, in the vast majority of divers, nothing.
> Think of it 
>as an informed consent -- "we're recommending this procedure; it's your 
>choice not to get it; but this is what can happen if you don't" -- with 
>that, some divers will have the procedure done and those who don't will 
>at least have made a decision based on a clear sense of the risks and 
>benefits.  (Personally, I think the risks of most diving are underplayed 
>in order to increase the market, but that's another issue.)
Difficult to see what you base this comment on.  The facts are there,
and must be interpreted correctly as they are at present known.
>
>Based on the info you've posted in the past and the DAN accident reports 
>I've read, it seems like the vast majority of scuba accidents and 
>injuries are earned -- from improper training, poor equipment 
>configuration, bad gas planning, diving beyond limits, etc. -- and not 
>from unearned causes like undiagnosed PFOs. Certainly that much is 
>obvious about West Palm. It seems to me that we'd save lives and reduce 
>risks more by setting higher training and equipment standards -- as you 
>and George have been doing all along -- than by requiring expensive 
>medical testing.
This I totally agree with.  Very few of the accidents in the UK are due
to PFO problems.  However, none of the agencies does any kind of audit
of the quality of their training, because none of them seem capable of
collecting denominator data i.e. the number of dives their certified
divers are undertaking.  It's no good trumpeting one year that the
number of accidents has decreased because of good equipment and training
unless one can show that the number of dives performed has not decreased
drastically.
>
>Just my $.04 -- Sorry about the length of the response -- it was a good 
>question! 
>
>
>
>Best Regards --
>
>Bill
>
>--
>Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
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Well, undoubtedly I have echoed some comments.  Doubtless it will set
the cat amongst the proverbials...
-- 
Dr. Chris. Edge
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