Mailing List Archive

Mailing List: techdiver

Message Display

A quick follow up regarding some additional information gleamed from a
quick search of other studies investigating the occurrence of PFO and
decompression sickness, especially given George's "gentle" comdemnation of
my last post suggesting PFO may not be a factor associated with
decompression sickness.
Before I go further for the sake of the list I retract any suggestion I may
have made regarding PFO not being associated with an increased risk of
decopression sickness.  In my haste of seeing an article relevant to a
thread on the list I posted it without doing alittle background check to
ensure its validaty. Thanks to George for his comments and provoking me to
look beyond that single article.  I only post this stuff so people don't
only remember the one study suggesting PFO does not increase your chances
of suffering decompression sickness.  I won't waste your time and bandwidth
with my own opinions on the studies listed below, as any reasonable person
should be able to realise what they mean and what each individual diver
should be doing to reduce their risks.  If you're uncertain then reread
George's rebuttal to my initial post.

Bove (1998) found using statistical analysis of subjects from sport diving,
US navy and comercial diving populations that the presence of a PFO
produces a 2.5 times increase in the odds for developing serious (type II)
DCS in all three types of divers.  Unfortunately the author then suggests
that as the odds ratio for developing DCS is small anyway, the risk of
devloping DCS in the presence of a PFO remains small and therefore doesn't
warrant routinue screening by echocardiography of sport, military or
commercial divers. Before you hit that reply button read on...

Germonpre et al (1998) compared the presence of a PFO in belgian divers
that had suffered from neurological DCS with a control population that had
not suffered any DCS.  The statistics are staggering:
Of divers suffering from neurological DCS 59.5% had a PFO while the only
36% of control divers had a PFO.  For divers suffering cerebral DCS 80% had
a PFO compared to 25% in controls and for divers with spinal DCS there was
no differences between those with DCS and the control populations.  When
divers with UNEXPLAINED cases of DCS were examined 83% had a grade 2 PFO
(grade 2= score of greater or equal to 20 bubbles contrast passage at rest
or after Valsalva strain).
 To summarize, this study suggests that a PFO is strongly correlated with
cerebral DCS.
The authors also noted that there was a striking difference in the method
used for middle ear equalization between divers suffereing cerebral and
spinal DCS.  Whereas spinal DCS divers had no problems equalizing (yawning
or light Valsalva), the divers suffering from cerebral DCS reported they
had to "push hard" to clear their ears.  This might be relevant as the
Valsalva maneuver induces a major rise in right atrial pressure, a major
cause of blood shunting thru the PFO.
They recomend divers with unexplained DCS or with cerebral DCS hits be
investigated for PFO.  If a grade 2 PFO is present then those divers are
advised to follow dive profiles that are very low "bubble-prone" (perhaps
the list might want to comment on what sort of dive this might be???? ie.
<3m) or give up diving.

I won't bore you all to tears with details of the results of animal models
except to say that using anesthetized pigs with PFO the risks of arterial
bubbles and air embolism is higher.

Phil Davies

Bove AA (1998) Risk of decompression sickness with patent foramen ovale.
Undersea Hyperbar Med 25:175-178.
Germonpre, P Dendale, P unger P and Balestra C (1998) Patent foramen ovale
and decompression sickness in sports divers. J. Appl Physiol 84:1622-1666.


--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]