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Harry, =20
Your explanation sounds solid. The fatty membrane (lipid) surrounding =
neurons is call the myelinated sheath. One of the purposes of the =
myelinated sheath is thought to be conductivity. Nerve impulses move =
faster along neurons that are mylinated. Your defininitly on the right =
track. =20
Forgive my ignorance here, but what mechanism are you referring to? =
What action does it represent? Give me more information on that.
Hope this helped a little,
Brian =20
-----Original Message-----
From: Harry Dewhurst <_dewhurst@at*.me*.ne*>
To: Mike McDiarmid <mmcdiarm@ya*.co*>
Cc: cavers@cavers.com <cavers@cavers.com>
Date: Wednesday, December 30, 1998 12:42 PM
Subject: Re: Narcosis Question
=20
=20
I wonder what the physical mechanism is. I once heard an =
explanation
that goes something like this. The membranes surrounding the =
neurons
have a high fat content, so that when they are exposed to a high =
partial
pressure of lipid soluble inert gas (such as Nitrogen) they swell =
up.=20
This produces the narcotic effect. With Helium, the opposite =
happens
and the membrane shrinks. This is the cause of HPNS. It takes a =
much
greater pressure, though. With trimix, the effects tend to cancel. =
I
tried to check this out in Bennett and Elliot, but I was overcome by =
the
MEGO effect (My Eyes Glaze Over). One thing I did notice is that =
lipid
solubility is highly correlated with narcotic potency. This seems
strange since the water/lipid solubility ratio apparently doesn't
matter. I didn't see any data for Oxygen solubility.
=20
Mike McDiarmid wrote:
>=20
> There are others on this list with far more knowledge than I, but =
I
> have been told that in determining the narcotic effect of a gas =
you
> must consider its lipid solubility. Oxygen has a high lipid
> solubility so therefore is in fact narcotic and should be =
considered
> when determining the END of a mixture. He does not, or is very =
low,
> so not a factor in the calculations. Bill Mee, George or JJ can
> answer this one better. My apologies if I have mis-stated =
anything.
> Traditional teachings by the agencies do not account for the =
O2
> content of a mixture in determining the END. This is a mistake. =
End
> of subject.
>=20
> Mike
>=20
> ---Jsuw@ao*.co* wrote:
> >
> > When determining the acceptable narcosis exposure for a dive, it
> seems that
> > only the narcotic effect of nitrogen is considered. Oxygen is =
at
> least as
> > narcotic as nitrogen. Although helium is far less narcotic than
> either, it
> > still is an inert gas with potential to have narcotic =
properties.
> >
> > With this in mind, why is it that only nitrogen's narcotic =
effects are
> > considered? How can the narcotic effect of the other gases be
> accounted for?
> > Does it matter?
> >
>=20
> _________________________________________________________
> DO YOU YAHOO!?
> Get your free @yahoo.com address at http://mail.yahoo.com
=20
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<DIV><FONT color=3D#000080 face=3DFixedsys size=3D2>Harry, =
</FONT></DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys size=3D2>Your explanation =
sounds=20
solid. The fatty membrane (lipid) surrounding neurons is call the=20
myelinated sheath. One of the purposes of the myelinated sheath is =
thought=20
to be conductivity. Nerve impulses move faster along neurons that =
are=20
mylinated. Your defininitly on the right track. =
</FONT> </DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys
size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys size=3D2>Forgive my ignorance =
here, but=20
what mechanism are you referring to? What action does it =
represent? =20
Give me more information on that.</FONT></DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys
size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys size=3D2>Hope this helped a=20
little,</FONT></DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys
size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000080 face=3DFixedsys size=3D2>Brian =
</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000080 solid 2px; MARGIN-LEFT: 5px; PADDING-LEFT: =
5px">
<DIV><FONT face=3DArial size=3D2><B>-----Original =
Message-----</B><BR><B>From:=20
</B>Harry Dewhurst <_<A=20
=
href=3D"mailto:dewhurst@at*.me*.ne*">dewhurst@atl.mediaone.net</A>&g=
t;<BR><B>To:=20
</B>Mike McDiarmid <<A=20
=
href=3D"mailto:mmcdiarm@ya*.co*">mmcdiarm@yahoo.com</A>><BR><B>Cc: =
</B><A=20
href=3D"mailto:cavers@cavers.com">cavers@cavers.com</A> <<A=20
=
href=3D"mailto:cavers@cavers.com">cavers@cavers.com</A>><BR><B>Date:
=20
</B>Wednesday, December 30, 1998 12:42 PM<BR><B>Subject:
</B>Re: =
Narcosis=20
Question<BR><BR></DIV></FONT>I wonder what the physical
mechanism =
is. =20
I once heard an explanation<BR>that goes something like this. =
The=20
membranes surrounding the neurons<BR>have a high fat content, so =
that when=20
they are exposed to a high partial<BR>pressure of lipid soluble =
inert gas=20
(such as Nitrogen) they swell up. <BR>This produces the narcotic=20
effect. With Helium, the opposite happens<BR>and the membrane=20
shrinks. This is the cause of HPNS. It takes a =
much<BR>greater=20
pressure, though. With trimix, the effects tend to =
cancel. =20
I<BR>tried to check this out in Bennett and Elliot, but I was =
overcome by=20
the<BR>MEGO effect (My Eyes Glaze Over). One thing I did =
notice is=20
that lipid<BR>solubility is highly correlated with narcotic =
potency. =20
This seems<BR>strange since the water/lipid solubility ratio =
apparently=20
doesn't<BR>matter. I didn't see any data for Oxygen=20
solubility.<BR><BR>Mike McDiarmid wrote:<BR>> <BR>> There
are =
others=20
on this list with far more knowledge than I, but I<BR>> have been =
told=20
that in determining the narcotic effect of a gas you<BR>> must =
consider=20
its lipid solubility. Oxygen has a high lipid<BR>> =
solubility so=20
therefore is in fact narcotic and should be considered<BR>> when=20
determining the END of a mixture. He does not, or is very =
low,<BR>>=20
so not a factor in the calculations. Bill Mee, George or JJ=20
can<BR>> answer this one better. My apologies if I have =
mis-stated=20
anything.<BR>> Traditional teachings by =
the=20
agencies do not account for the O2<BR>> content of a mixture in=20
determining the END. This is a mistake. End<BR>> of=20
subject.<BR>> <BR>> Mike<BR>> <BR>><A=20
href=3D"mailto: ---Jsuw@ao*.co*"> ---Jsuw@ao*.co*</A> wrote:<BR>> =
><BR>> > When determining the acceptable narcosis exposure =
for a=20
dive, it<BR>> seems that<BR>> > only the narcotic effect of =
nitrogen is considered. Oxygen is at<BR>> least as<BR>> =
>=20
narcotic as nitrogen. Although helium is far less narcotic=20
than<BR>> either, it<BR>> > still is an inert gas with =
potential to=20
have narcotic properties.<BR>> ><BR>> > With this in =
mind, why=20
is it that only nitrogen's narcotic effects are<BR>> >=20
considered? How can the narcotic effect of the other gases =
be<BR>>=20
accounted for?<BR>> > Does it matter?<BR>> ><BR>> =
<BR>>=20
_________________________________________________________<BR>> DO =
YOU=20
YAHOO!?<BR>> Get your free @yahoo.com address at <A=20
=
href=3D"http://mail.yahoo.com">http://mail.yahoo.com</A><BR></BLOCKQUOT
E>=
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