You obviously do not dive. Any thing can raise the blood pressure
SUBSTANTIALLY immediately, and it takes little or no differential to open
the flap, a harmless event in a non diving person. I am so sick and tired of
bullshit with no answers, and luckily do not have to listen to it. You have
PFO you do not dive with the WKPP, and what the rest of you do is your
problem, not mine.Believ what you want.

-----Original Message-----
From: Gozum_NT at OIT [mailto:marvin.gozum@ma*.tj*.ed*]
Sent: Monday, June 11, 2001 4:59 PM
To: Matthias Voss; ghmorris@te*.co*
Cc: 'Trey'; 'Rodriguez'; 'Wendell Grogan'; 'Bruce Sherman'; 'Quest@Gu*.
Com'; 'Techdiver List'; marvin.gozum@ma*.tj*.ed*
Subject: Re: Not opening PFO's, waqs RE: Repairing PFO's


Hello All,

I'm not subscribed to your elists, so please forward this email as you
please. I read George's forward.  I've sending the original post at the
very bottom of this message, to improve the formatting.  Matthias commented
that the ff comment appear more in-line, versus a 'DAN' position, I bring
up this further comment extracted from this thread:

> > -- Unfortunately for those with PFO, a rise in pulmonary
> > -- arterial pressure,

While this is one mechanism for a bubble transit via a PFO without
increased chest pressure, in many cases [ as human anatomy varies in
strength, location and response] if significant acute pulmonary
hypertension occured by bubbles embolizing the pulmonary artery, bubbles
must be forming faster than its rate of clearance through the lungs, in
such events even with chamber treatment, deaths from right heart, and
circulatory failure is high.  AGE via a PFO would be the least of your
problems if significant pulmonary hypertension developed via an offgassing
event.  This is close to Chris Rouses' death described in the book, "The
Last Dive."

Mikey's description of a TEE with bubble contrast is superbly researched
and crafted.  I will add that about 0.5ml of air is mixed with 10-20ml of
saline, shaken to view gross bubbles, and injected into the patient to see
if these bubbles transit accross the PFO, hence to the arterial circulation
and the brain.  If doing this test is problematic, you could opt for a new
transcranial doppler to track bubbles within the cerebral circulation, in
both tests no harm occurs from bubbles. Both test are superior to a TTE,
with the TEE the gold standard.  Transcranial doppler is less invasive than
TEE with similar results but its too new to tell. However, if you've got a
positive transcranial or TTE result, why endure a TEE?  To the cost, the
TEE requires a physician to perform the procedure, escalating the cost.  A
TTE is ~$1000.

So how then can post-dive bubbles crossing a PFO be harmful?  There must be
another factor besides the PFO for risk for AGE.  A very large quantity of
bubbles? How large? If routinely individual tech divers stray far from
surfacing M-value in very deep dives and dive profiles produce "more
bubbles" without overt DCS than recreation divers, this maybe cause for
concern.

However, as 'tech' information has been collected by DAN only since 1997,
in the 2000 report info reveals DCS and AGE rates for tech dives no greater
than recreational, but higher death during tech dives, all causes, most
among the most experienced and instructor certification level.  If tech
organizations recommending PFO screening have information DAN doesn't it
would be good to share it, as to Do It Right, suggests use the Right
information.

Repairing a PFO carrys 0.2-1% risk of death via a cardiac catetherization
procedure.  NONFATAL AGE risk with an open PFO is roughly about 0.21% and
if AGE is treated early and heals without residual symptoms, a recovered
diver can dive again.  Thus, beyond cost/benefit, there is no risk/benefit
to PFO screening unless one experiences neurologic symptoms first, and
later find a PFO.

For those into statistics, a Bayesian analysis suggests that anyone pushing
the envelope in decompression theory would opt to minimize any known risk
factor, considering a very high a priori risk for injury.  Just as
astronauts were superb physical specimens to deal with the unknowns of
early space travel, so would pioneers in risky ventures, such as very deep
dives.  The physical requirements for Earth orbit mission astronauts is not
high these days, but those for Mars are.  This analogy maybe an optimal way
for tech divers to approach the issue of PFO.

As apprentice tech diver myself, I put my life where my mouth is, as we all
do in this sport.

My regards to George and Mikey [ I was Mr. Ear trouble that weekend on the
Lowrance].  I regret I haven't the pleasure of meeting/diving with the
others from the "Florida" group, but I hope to in the near future.  George
showed me quite a great deal, and the tech community, equipment, dive
conditions, and support logistics in George's neighborhood is an incredible
phenomenon for nurturing superb technical diving skills.  Alas, all I can
muster safely in Philadelphia is the Atlantic Ocean, or a 100 ft quarry.

Dive safe All!









At 04:25 PM 6/11/2001 +0200, Matthias Voss wrote:
>I think Mike's comment is much closer to the point than the DAN's
>insights.
>Matthias
>
>George Morris schrieb:
> >
> > Commentary from Marvin Gozum, DAN trained physician. Forwarded with
> > permission.
> >
> > >--
> > >--  >-- Yes, this is the mechanism that does it, and unfortunately
> > >--  >-- is what allows
> > >--  >-- for the dive industry's RJ Reynolds twist of the facts. Most
> > >--  >-- PFO's require
> > >--  >-- the bubbles to raise the pressure to open the flap, so many
> > >--  >-- people can do
> > >--  >-- hundreds or even thousands of dives without consequence, and
> > >--  >-- then end up in
> > >--  >-- a wheelchair . The morons at DAN call that an "unearned
> > >--  >-- hit". I call it
> > >--  >-- lying and denial. 30% of us have it. Do you feel lucky?
> > >-- Well do ya?
> > --
> > -- At 09:17 PM 6/7/2001 -0400, wrote:
> > --
> > -- >Sure, that's the point behind not exerting yourself for a
> > -- while after
> > -- >the in water part of your off gassing.  Until you stop bubbling,
> > -- >anything you do that causes a rise in chest cavity
> > -- pressure- bending and
> > -- >lifting, straining, etc- can open the PFO and shunt bubbles
> > -- into your
> > -- >brain.
> > --
> > -- Unfortunately for those with PFO, a rise in pulmonary
> > -- arterial pressure,
> > -- and retrograde rise in right atrial pressure secondary to
> > -- the pulmonary
> > -- embolization of nitrogen/helium bubbles at the alveolar-capillary
> > -- complex would also cause right-to-left shunting through the PFO - no
> > -- exertion required.
> > --
> > -- All the more reason to get tested if you're doing technical diving.




http://www.emedicine.com/ped/topic2494.htm


"
Comment in:
Undersea Hyperb Med. 1999 Spring;26(1):49-50

Risk of decompression sickness with patent foramen ovale.

Bove AA.

Cardiology Section, Temple University Medical School, Philadelphia,
Pennsylvania, USA.

Several reports have described populations of divers with decompression
sickness (DCS) who have a patent foramen ovale (PFO). The presence of a PFO
is known to occur in about 30% of the normal population, hence 30% of
divers are likely to have a PFO. Although observations have been made on
the presence of a PFO in divers with and without DCS, the risk of
developing DCS when a diver has a PFO has not been determined. In this
study, Logistic Regression and Bayes' theorem were used to calculate the
risk of DCS from data of three studies that reported on echocardiographic
analysis of PFO in a diving population, some of whom developed DCS. Overall
incidence of DCS was obtained from the sport diving population, from the
U.S. Navy diving population, and from a commercial population. The analysis
indicates that the presence of a PFO produces a 2.5 time increase in the
odds ratio for developing serious (type II) DCS in all three types of
divers. Since the incidence of type II DCS in these three populations
averages 2.28/10,000 dives, the risk of developing DCS in the presence of a
PFO remains small, and does not warrant routine screening by
echocardiography of sport, military, or commercial divers.

""

That incidences of venous bubbling by doppler [ regardless of the Spencer
Scale] occurs in a very large fraction of dives, the current Summer 2001
issue of Immersed reports it exceeds 85% if one does >1 dive/day, and over
67% of these are 'high grade' in size;  37% occurred in a single dive, as
far as 90 minutes post-dive.

The above findings already reinforce that the relationship between having
venous bubbles and DCS is poor, otherwise we'd all have been bent,
paralyzed or stroked by now since bubbles occur nearly in all dives.

Further, despite the high incidence of venous bubbles in dives from either
well executed deco dives or no-stop dives and the 30% incidence of PFOs in
the population, the incidence of _all_ DCS in toto is still < .07% or
7/10,000.  The status quo is not to ban diver with PFOs nor screen for PFOs
in general yet the incidence of AGE among divers is not proportionate to
the baseline population risk of PFO ~30%. Clearly some other factor is at
work to make AGE occur in a setting of PFOs.

As Dr. Bove notes, there is a 2.5x increase in 'odds ratio' for DCS 2 with
PFO, which we translate here loosely as 'risk'.

A Valsalva or coughing, after bubbles are intentionally injected into the
venous system, is done routinely in a bubble contrast echocardiogram to
view bubble transits in diagnosing PFO. Despite that, patient's don't
stroke.  This test suggests large quanitities and size of the bubbles are
vital to cause harm.

As for technical diving, anything increasing the decompression obligation
increases the production of venous bubbles, and this means diving deep,
and/or multiple dives per day.  Its is unknown if He with nitrox deco
decreases the risk of venous bubbles versus air in deep dives, however its
assumed logically that properly executed He, nitrox or 100% 02 dives
significantly diminishes the nitrogen load, and logically allow these
divers to dive deep and assume a risk akin to recreational divers for
venous bubbling.

You can still have right-to-left shunting from within the lungs itself,
either congenital OR acquired lung trauma [barotrauma, smoking damage, age
related weaknesses.]  This allows bubbles to squeeze through the
lungs and removes its filtering effect, and there's no way to test for it
to date.

Finally, assuming you do do the recommendation of determing your existence
of a PFO before embarking on a technical dive.  What do you do if you find
a PFO?  If divers have been diving with a PFO without incident, would you
repair an asymptomatic PFO to lower a theoretical risk for AGE with diving
or stop diving?  An echocardiogram is ~>$1000 and the cath will set you
back $10,000 plus endure a 1.0->0.2% risk of death, a risk higher than the
3 fold risk [~.21%] of _nonfatal_ AGE from PFO, assuming a baseline DCS
risk of .07%.



Warm regards,


Marv



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