Posted by MHK on May 10, 2001 at 11:06:23:
In Reply to: On MHK, Liars, and Idiots posted by BillP on May 10, 2001 at 10:58:46:
BillP has taken what was a legitimate issue and turned it into a circus and claims that I didn't respond to him.. I got his e-mail yesterday and I responded within a few hours of getting it..
Here's what I sent him:
Bill you just sacraficed any integrity you had with me and sadly it's all because of an idiot like Seahunt..
BTW, Bill it's a shame you offered up other's research as your own in your game of gotcha...
Bill,
As I noted in my earlier post I was out of the office yesterday so I'm a
little swamped today,
I wouldn't waste a ton on time on Seahunt, he's an idiot that only like to
stir the pot..
Here's what I copied from..
Posted by BillP on 09-23-2000 04:18 PM
Hi Dr. Deco:
George Irvine, III and Bill Mee of cave diving and DIR fame have promoted
the theory on the techdiver mailing list that nitrogen in a diver's
breathing mix somehow causes red blood cells' membranes to become
(?irreversibly?) rigid. This red blood cell rigidity decreases the
deformability of red blood cells causing them to sludge in the circulation,
reducing tissue perfusion, and damaging blood vessel walls. I get the idea
from reading their writings that this damage presumably leads to an
increased risk of DCS. From what I can tell from reading their writings,
they go on to say that adding ANY helium to the breathing mix will alleviate
the deleterious effects of nitrogen on red blood cell membranes.
Followers of GI-3's and BM's writings have been known to use their theories
about nitrogen and cell rigidity to make statements like, "The long term
cell rigidity effects of prolonged exposure to N2 are not to be
underestimated" to support their position that trimix should routinely be
used for recreational diving. As recreational divers typically breathe air
or nitrox on their dives, they are supposedly risking long term damage to
their cells from their exposure to nitrogen, so they should add some
protective helium to their breathing mix.
I have been unable to find anything in the diving or medical literature that
supports the view that nitrogen causes the membranes of red blood cells (or
any other cells) to become rigid. I have found no "long term cell rigidity
effects of prolonged exposure to N2", nor have I found any evidence to show
that helium is protective against the effect- other than in the writings of
GI-3 and BM. (The journal articles BM cited in the link below discuss the
effects of pressure on red cell aggregation, not the effects of nitrogen or
helium on the flexibilty of the red cell membrane.) Are you aware of the
results of any research in the area? Are recreational divers risking cell
injury due to this "cell rigidity" effect of nitrogen and should they add
helium to their mix to protect themselves?
For some reason I haven't been able to directly log onto the techdiver
mailing list archive to get more of GI-3's and BM's writings for you, but I
did find another archive with a couple of GI-3's and BM's notes. You can
find them at:
http://www.nwls.com/list-archive/reademail.asp?id=5573
http://www.nwls.com/list-archive/reademail.asp?id=5609
and
http://www.nwls.com/list-archive/reademail.asp?id=24174
to get an idea of what they're talking about if you haven't seen it before.
This is just an example of their writings on the subject. They go into more
detail and explain their theory more thoroughly elsewhere. I'll be
interested to read your thoughts.
TIA,
Bill
[Edited by BillP on 09-23-2000 at 07:21 PM]
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Posted by Dr Deco on 09-24-2000 10:50 AM
NASA's charter in barophysiology deals with depressurization of
saturation (1 atmosphere) and we are seldom involved in work at increased
pressure. Therefor I am not a close follower of this concept of nitrogen and
red cell rigidity. I have not actually heard of it from Mee and Irvine, two
well respected explorers of the Wakulla Springs system. I could speculate
from a theoretical perspective, however.
1. In general, known pressure effects to date are limited to the nervous
system, i.e., the high pressure nervous syndrome. This has been attributed
to a change in nerve cell membranes by the pressure per se, and nitrogen is
added to the breathing mix to counteract the increased tremors. The result
is the well-known trimix.
2. The effect of nitrogen in the literature on red blood cells (RBC) is with
regard to the clumping (aggregation) of the cells. This is a demonstrable
event in vitro (in a test tube). I am not aware of it occurring in vivo (in
the living system). This aggregation of RBCs is not the same as a stiffening
of the membranes, however.
3. When RBC aggregation does occur in vivo in the dive setting, it was
associated with decompression, intravascular gas bubbles, and was referred
to a "disseminated intravascular coagulation (DIC)." DIC is a serious
condition that occurs in, among other diseases, severe decompression
sickness. Drugs against this (e.g. heparin) have been employed with some
success in severe cases.
4. The addition of helium might or might not reverse the rigidity, but there
is neither data on rigidity or its reversal by helium, at least as far as I
know.
5. Certainly, the increase of rigidity would be bad in low flow situations
(low shear) since it would further retard gas elimination. Again, I do not
know that this RBC rigidity actually occurs.
Thanks for the question, Bill.
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Posted by BillP on 09-24-2000 02:42 PM
Re: Your point #2- "The effect of nitrogen in the literature on red blood
cells (RBC) is with regard to the clumping (aggregation) of the cells."
Looking at the abstracts of the articles that Bill Mee cited to support his
views on nitrogen and red cells, they seem to discuss the effect of PRESSURE
on red blood cell aggregation and not specifically the effect of nitrogen on
red cells. I have searched the medical literature for the effect of nitrogen
on red cell aggregation, but came up empty handed. There are articles on
nitrogen _microbubbles_ and _platelet_ aggregation, but I didn't find
anything on nitrogen gas and red cell aggregation. Did I miss the articles?
Are they in the aerospace literature?
TIA,
Bill
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Posted by Dr Deco on 09-24-2000 05:25 PM
These are the articles I found in the MEDLINE search. The first shows the
effect of pressure per se [Chen S; Gavish B; Barshtein G; Mahler Y; Yedgar S
Red blood cell aggregability is enhanced by physiological levels of
hydrostatic pressure. Biochim Biophys Acta 1994 Jun 22;1192(2):247-52 ].
Another shows the effect of in vivo nitrogen in humans [Taylor WF; Chen S;
Barshtein G; Hyde DE; Yedgar S Enhanced aggregability of human red blood
cells by diving. Undersea Hyperb Med 1998 Fall;25(3):167-70 ]. In my last
reply, I mistakenly referred to it as an in vitro study; it is in human
subjects. The nature of the bottom gas was not listed in the abstract.
I still doubt that this has a big role in recreational SCUBA diving under
the conditions normally encountered.
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Posted by mike on 09-24-2000 09:55 PM
if i am not mistaken, RBC's typically have a lifespan of roughly 3 to 4
months. In addition, we tend to produce on average, 2,500,000 of the little
buggers per second. even if they are damaged at pressure by N, there
shouldn't be too much long term damage, unless one is diving deep day after
day month in month out? and the mechanics of clotting as caused by bubble
formation are interesting. What could it be about either the N-pressure or
the bubbles that would initiate agglutination? sorry to be a pest but this
stuff really is interesting!
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Posted by BillP on 09-25-2000 03:14 AM
Thanks Dr. Deco. I noticed those studies, and Bill Mee did use them to
support his views on nitrogen and red cell rigidity. Again, the first study
looked at the effect of *hydrostatic pressure* (up to 15 bar for up to 2
hours) on the aggregability of red blood cells in vitro and found that the
aggregability increases up to three-fold.
The second study was indeed an in-vivo study with volunteer divers in
chambers diving up to 300ft. They again looked at the effect of *pressure*
on RBC aggregability and found increases in red cell aggregability at 66'
and 300'.
But again, neither study specifically looked at the effect of *nitrogen* on
RBC aggregability and neither looked at rigidity of RBC membranes, so I
frankly don't see how either study supports GI-3's or BM's views. If I were
to propose the hypothesis that second hand tobacco smoke in bars causes an
increase in car accidents, quoted a study that showed an increased incidence
in car accidents in people who had been drinking in bars, and then said,
"See! It was that awful tobacco smoke that cause the accidents!" I would be
considered a scientific stroke. ("Stroke" is a cave diving term for someone
who, er, doesn't know what they're doing.) I might still be right in my
conclusions about second hand smoke and car accidents, but it would be,
shall we say premature, for me to publish my findings without further study,
and improper for me to use an unrelated study to support my views.
Apparently GI-3 and BM have tried to do some studies on the subject, or have
at least talked about it. I would like to see them publish their findings in
a peer review journal rather than the techdiver list.
Now, mike, the life span of a red blood cell is about 180 days, but if RBC
aggregability is increase by diving it could lead to clot formation in small
vessels. The clot could obstruct blood flow leading to tissue damage or even
cell death. The effects of that tissue injury *could* be long term and
additive over multiple dives. Dunno what it is about pressure that seems to
increase aggregability but Dr Chen et al's studies seem to indicate that it
does. I just don't see data that show that it's the nitrogen in the pressure
that causes the problem or that helium prevents the problem as GI-3 and BM
propose. It's an interesting idea, but I think that I'd like to see a little
more data before I start promoting trimix to reduce the risk of dangerous
cell rigidity in recreational diving.
Bill
[Edited by BillP on 09-25-2000 at 06:27 AM]
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Posted by Dr Deco on 09-25-2000 05:21 AM
Thanks to Mike and Bill for their recent remarks. I have now been able to
review the article on RBC aggregation as performed at the US Navy facility
[Taylor WF; Chen S et al. Enhanced aggregability of human red blood cells by
diving]. Curiously, the authors report that the greatest change in
aggregability was between the surface and the 66-fsw level. This pressure
was achieved using air as the compression gas. The increase in aggregation
was little changed from there to the 300-fsw level where the compression gas
was helium (added to the air from the 66 fsw level). If helium is purported
to prevent or REVERSE this aggregation, these data do not at all to
demonstrate that.
The authors state that the effect appears to be one of hydrostatic pressure
and that helium has no effect and does not reverse this. ("In the pressure
chamber, fractions of gases were adjusted to maintain the same partial
pressure of oxygen and nitrogen at all depths below 66 fsw.. Therefore, as
the depth increases below 66fsw, the helium partial pressure increases. If
an increase in RBC aggregation is in part caused by an increase in partial
pressure of inert gas, one would expect a proportional increase in RBC
aggregation at 300 fsw. That was not observed."]
I therefore do not see that the data support the concept that helium will
reverse this pressure-induced aggregation, nor is it obvious (from the in
vitro study) that nitrogen itself is responsible for the increased
aggregability of RBCs.
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Posted by BillP on 09-25-2000 08:54 AM
Thanks Dr. Deco. I pulled the studies too. The studies do leave some
questions unanswered, but your analysis of their findings seems right on the
money. Interesting that BM and GI-3 would quote studies that don't support
and even contradict their views to promote their theory.
It might help to use a 1 ATA diving suit for recreational diving to avoid
red cell aggregation (hmmm, maybe that's overkill), but I don't see the need
to recommend adding helium to the breathing mix to avoid "long term cell
rigidity effects of prolonged exposure to N2" just yet.
Bill
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Posted by Dr Deco on 09-25-2000 04:48 PM
They do indeed seem to have used the references in a reversed way. In the
end, the best thing that a diver can do for his blood is to keep well
hydrated to insure proper perfusion and not allow surface tension to drop to
a lower level.
Thanks again for the fine questions......
Michael R. Powell, Ph.D.
NASA/Johnson Space Center
Environmental Physiology/Biophysics Group
Mail Code SD3
281-483-5413 [FAX 281 483-2888]
e-mail michael.r.powell1@jsc.nasa.gov
----- Original Message -----
From: "BillP"
To:
Sent: Wednesday, May 09, 2001 11:07 AM
Subject: A Reminder
> Hi Michael:
>
> Just a reminder. On the diver.net BBS you made the following comments
> to Seahunt (and to the "wider audience" of the other diver.net board
> members and lurkers) regarding quotes that you attributed to me by name:
>
> "let's assume that I cut and paste his" [my] "post will you then admit
> you are a liar and an idiot????"
>
> "BillP did NOT post it to the tech list but a different list, and he
> posted every syllable I said he did."
>
> and
>
> "If you are going to call someone a liar be prepared to back it up or
> shut the hell up for once.."
>
> Again, I don't recall when or where I made the statements that you said
> I did. I believe that you may have misquoted me. Even if you didn't
> misquote me the "facts" implied in the "quotes" (as I understand them
> from your posts) are in error and deserve clarification. You seem to be
> implying in your messages on diver.net that you can directly access my
> statements to "cut and paste" them, so I would appreciate it if you
> would point me to where you found them. No, I don't necessarily agree
> that "If you are going to call someone a liar be prepared to back it up
> or shut the hell up for once". I feel that if you are going to quote
> someone you should be prepared to reference where you got the quote, and
> if you MIS-quoted them you should publicly retract your statement rather
> than just "shut the hell up". If you make a claim, you should be
> prepared to effectively support it or publicly recant.
>
> I know that you must be terribly busy getting ready for your trip to
> Akumal on the 12th, but I take having my name used as you have used it
> very seriously and would appreciate it if you would help me clear this
> matter up before you leave.
>
> TIA,
>
> Bill
>
> BTW, I understand that you will be with JJ in Akumal 5/12-5/20. Sounds
> like a great trip. Again, I know you both must be busy with
> preparations, but do you think he will be able to get you the literature
> references you're looking for before you leave, or should we wait until
> you get back? I know that you have no control over what JJ does, but if
> we need to wait until you get back, how long do you estimate it to take
> for you to get everything together? Are you trying to use sources other
> than JJ to track down these "many studies"?
>
> Another reminder of another quote of yours: "Bullshit... I answer every
> question and I don't evade any answers." Candid answers to the above
> questions will be appreciated. (And if you would like links to where
> you made the statements that I quoted, I can provide them.)