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In-Reply-To: <9604291437.AA18562@nw*.an*.co*>
> I'm posting this for a buddy who got hit, and does not have net access.
Sorry to hear about your buddy. Something similar happened in our branch
several years ago; an advanced diver with many dives under his belt
suddenly got CNS effects after a not particularly provocative dive. He
made a full recovery, but took the medical advice to hang up his
regulator. Very sad for him, and a great loss to our club.
> Who rejects confirmed PFOs?
I suppose this depends who your certifying agency is. With the BSAC you
must have a current medical to dive, and a known PFO would almost
certainly disqualify you as the doctor is likely to take the view that it
is only a passtime and err on the side of caution. You could cover it up
and probably get away with it, particularly on holiday dives, but is it
worth it?
> Why?
> Reconcile this with medical proof of 30% PFO incidence in normal
> population? With 30% of the pop affected, why aren't divers tested
> and 30% rejected?
Cost. Also, the figures are 10%-30% of the population depending on who
measured it. A couple of quotes from Bennett & Elliott may help:-
"The question of qualification of the diver with a right to left shunt in
the circulatory system has become important following a study by Moon,
Camporesi and Kisslo in 1989. Thirty divers with decompression suckness
were studied by echocardiography and in the 18 divers with serious DCI
61% had evidence of shunting through a PFO during Valsava manouvre. This
incidence of PFO is far in excess of a normal population and suggests the
possibility of assymptomaticbubbles entering the arterial circulation by
right to left shunting. At the present time [1993] there are no
conclusive findings. The individual with a known PFO should be made aware
of the possible increased risk in diving. The diver who has had serious
decompression illness and is found to have a PFO requires individual
counselling concerning future diving, particularly if examination of teh
dive profile shows that decompression illness was unmerited. There is no
recommendation for screening all divers for PFO, although some
authorities recommend offering such screening to every candidate for
diver training. Certainly there are currently divers with an undiagnosed
PFO diving with no difficulty at all." p64
"The prevalence of PFO in the healthy, adult population is estimated to
be between 10% and 30% depending on the detection method used. A number
of recent cross-sectional studies have shown a higher incidence of PFO in
divers who have suffered decompression illness compared with control
populations. On the other hand there are examples of highly experienced
professional divers who have not had clinically overt DCI and yet have
been found to have a PFO. The proposal of inter-arterial defects as
conduits for the right to left shunting of blood and bubbles is
particularly plausible in divers, since the effects of cold, immersion
and pulmonary artery gas embolism will increase right heart pressures.
However further studies will be necessary before the association between
arterial septal defects and DCI can be considered causal." [references
omitted] p457
> The heart pumps both sides simultaneously and as the freshly oxygenated
> supply
> is to the whole body, the pressure will be higher on that side than the
> other,
> hence the cross-flow will be just to recirculate. The 'victim' saw this
> clearly on the enhanced U/S Doppler image. PFO under normal situations
> cross-flows from the newly oxygenated lungs back into the CO2 and N2
> rich feed
> to the lungs so no increased risk there.
See above. There is a difference between a hospital setting and diving
setting.
> This
> is only going to present a potential risk when outgassing, ie
> ascending+decompressing and again is transitory.
So you are only at risk of DCI when outgassing. Presumably if you can
dive without decompressing you are safe. :-)
> So thats it - he's in a sitaution where info is hard to find
Its not that hard to find, but it may be hard to accept if you love
diving. If your friend can get to Huddersfield it would be worth seeing
if he can make an appointment with Peter Wilmshurst who is a world
expert in PFO and diving. Contact details are:-
Dr Peter Wilmshurst
Huddersfield Royal Infirmary
Huddersfield
HD3 3EA
UK
Tel: +44 1484 422191
Good luck!
Steve
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