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FALL 2016
DIVE INTO
THE BLUE
unexso
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renowned dive crew;
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Freeport, Grand Bahama
Near The Port Lucaya Marketplace
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by venous blood bypass the
pulmonary filter, enter arterial
circulation and block blood flow in
terminal vessels (embolism), which
results in ischemic injury of tissue
downstream of the obstruction.
The most common form of
embolism is caused by blood clots
from peripheral veins passing
through the PFO and causing a
stroke. Paradoxical embolism
may occur in divers with a PFO
if the RLS occurs postdive when
a lot of venous gas emboli (VGE)
are present. Paradoxical embolism
caused by VGE may manifest
with symptoms of neurological
(spinal, cerebral and vestibular) or
cutaneous decompression
sickness (DCS).
The overall incidence of DCS
in recreational divers is two to
four per 10,000 dives, and the
incidence of neurological DCS is
less than one per 10,000 dives. In
the presence of a PFO, however,
the incidence of neurological
DCS increases fourfold. While
the average DCS risk for divers
with a PFO seems low, for some
individuals the risk may be greater
than overall statistics predict. The
main question regarding PFOs
and diving is how to identify
individuals who are likely at an
increased risk of DCS and how to
mitigate that risk. The workshop’s
consensus guidelines provide some
answers.
WHO SHOULD BE TESTED
FOR A PFO?
The consensus maintains that no
routine screening for PFOs in all
divers is necessary. It recommends,
however, that divers with a
history of more than one episode
of DCS with cerebral, spinal,
vestibulocochlear or cutaneous
manifestations should be tested for
a PFO. On the other hand, divers
with mild (other than cutaneous)
DCS need not be tested.
HOW TO TEST FOR A PFO
Experts well practiced in the
procedures should conduct
the test. The most appropriate
testing method is transthoracic
echocardiogram (TTE) with
DIVE SLATE
PATENT FORAMEN OVALE AND FITNESS TO DIVE
“Divers should always remember
that the main factor causing DCS
is the dive exposure itself —
the depth, time and ascent rate.
With a significant exposure, anybody
is at risk of DCS. Most people who
get DCS do not have a PFO.”