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Re: Power Snorkel, Snuba, or Helmet Diving? Posted on: Thu, 15 Mar 2007 23:56:14 -0500



-hh wrote:


> Adults have a PFO incidence rate of 20%, but some DCS injury studies
> have found that PFO's are overrepresented in injured divers, which
> indicates at least a correlation and likely causality.
>
> DAN had a report on DCS incidence rates as it correlated to the
> presence of PFO's. In short, the study suggested that the incidence
> of DCS increased fourfold (4x) if a PFO was present.
>
> Since PFO's are present in the womb and tend close (heal) slowly as
> the child grows up, this correlation would infer that kids might have
> up to 4x the risk of incurring a DCS injury than adults.
>
>
>
> -hh

Those numbers sound in line with what I've read. 20 - 35% of the
population affected. 4.5x the risk for DCS.

While the prevalence of PFO decreases with age, the size of the PFO
increases. In the study I cited earlier, 6 divers went from a grade 1
defect (minimal or 1-5 bubbles) to a grade 2 defect (moderate or 6 to 20
bubbles - anything greater than 20 being severe). Was diving causing an
increase in the size of the defect due to repeated Valsalva maneuvers or
increased pressure on the atrium, or was it simply the act of aging 7
more years? Not enough there to indicate that just diving was causing
the increased size.

While PFOs are the most likely cause of strokes in those under 55 years
of age, I believe that the risks increase as we age due to the increased
size of the defect - therefore, I'm not so sure we could infer that kids
of 10 to 18 years of age have any greater risk of a DCS injury than an
adult based solely on the presence of a PFO.

This discussion probably belongs on rec.scuba, but for now I'm outta
here to actually go diving rather than discuss it :)