Mailing List Archive Mailing List Archive
--------------152C2917E6AFAC42C40C7143
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
tgunther@co*.co* wrote:
> In a recent thread the narcotic properties of O2 were compared to that of N2.
> If memory serves me, it was stated that there was little difference. In
> Wienke's "Diving Physics and Applications," page 197, he lists the narcotic
> potency of N2 as 1.0 and goes on to list the narcotic potencies of other inert
> gases (argon, neon, etc). He leaves the potency of O2 blank though. Does
> anyone happen to know what it is?
Tod, this question bears no practical relevance to technical diving. It doesn't
matter if you belive in oxygen narcosis or not. The proper proper
gas selection is dictated by other variables.
If oxygen was highly narcotic it would primarily affect high oxygen
mixtures, but due to oxygen toxity concers these are only used at
shallow depth. As EAN50 at it's maximum operating depth is still a
reasonable safe choice (narcosis wise) I conclude that this is not
the case.
On the other hand if we are talking about bottom mixes where nacosis could
be a potential problem we don't exceed a ppO2 of 1.4bar (mostly lower
anyway) and a ppN2 of 3bar. If we follow that rule and oxygen would be more
narcotic than nitrogen the worst case is like the narcosis experienced when
diving EAN32@11* -- I dont consider this a big threat to diving safety.
Ok now back to the original question: If the mentioned table is based on
the Meyer-Overton hypothesis (ie. lipid solubility) the value should be
cloth to 0.5 (ie. twice as narcotic as nitrogen, comparable to Argon).
However, you should know that this hypothesis was proven wrong for Helium
and Neon (prediced narcotic potency: 4.26 respectively 3.58). In reality
both do not show ANY narcotic effect.
Another reason not to calculate the narcotic potency of oxygen based on
this hypothesis is that oxygen is metabolized and thus no inert gas.
Albano et al. 1962 made an interesting experiment which indeed supports
the assumption that oxygen is actualy less narcotic that nitrogen. He put
6 man in a dry chamber and let them solve arithmethic equations (summs) for
a certain amount of time.
Summs attempted (total) Correct Answers %Errors
Ambient pressure 245 227 7.3%
10bar Air 190 (=22% decrease) 117(=48% decrease) 38.2%
10bar 4%O2/96%N2 152 (=38% decrease) 80 (=65% decrease) 47.3%
There is evidence that O2 is narcotic, but it is not clear to which extent
the effect is cauesd by the oxygen itself or by some synergetic effects.
One of the mentioned synergetic effect is that high oxygen blocks the
haemogobin carrier mechanism. The increased pACO2 will potentiate nitrogen
narcosis.
Regards, Frank
P.S. Recommended reading: Physiology and Medicine of Diving,
Chapter 7: Inert Gas Narcosis
Hesser CM, Fagraeus L, Adolfson J: "Roles of nitrogen, oxygen, and
carbon dioxide in compressed-air narcosis" in Undersea Biomed Res, 1978
Abstract:
In an attempt to determine the roles of nitrogen, oxygen, and carbon
dioxide in compressed-air narcosis, the effects on performance (mental
function and manual dexterity) of adding CO2 in various concentrations
to the inspired gas under three different conditions were studied in
eight healthy male volunteers. The three conditions were: (1) air
breathing at 1.3 ATA; (2) oxygen breathing at 1.7 ATA; and (3) air
breathing at 8.0 ATA (same inspired O2 pressure as in (2)). By relating
performance to the changes induced in end-tidal (alveolar) gas pressures,
and comparing the data from the three conditions, we arrived at the
following results and conclusions. A rise in O2 pressure to 1.65 ATA,
or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused a
significant decrement of 10% in mental function but no consistent effect
on psychomotor function. A rise in end-tidal PCO2 of 10 mmHg caused an
impairment of approximately 10% in both mental and psychomotor functions.
The results suggest that, at raised partial pressures, all three gases
have narcotic properties, and that the mechanism of CO2 narcosis differs
fundamentally from that of N2 and O2 narcosis.
--------------152C2917E6AFAC42C40C7143
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: 7bit
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<tt>tgunther@co*.co* wrote:</tt>
<blockquote TYPE=CITE><tt>In a recent thread the narcotic properties of
O2 were compared to that of N2.</tt>
<br><tt>If memory serves me, it was stated that there was little
difference.
In</tt>
<br><tt>Wienke's "Diving Physics and Applications," page 197, he lists
the narcotic</tt>
<br><tt>potency of N2 as 1.0 and goes on to list the narcotic potencies
of other inert</tt>
<br><tt>gases (argon, neon, etc). He leaves the potency of
O2 blank though. Does</tt>
<br><tt>anyone happen to know what it is?</tt></blockquote>
<tt>Tod, this question bears no practical relevance to technical diving.
It doesn't matter if you belive in oxygen narcosis or not. The proper
proper</tt>
<br><tt>gas selection is dictated by other variables.</tt>
<p><tt>If oxygen was highly narcotic it would primarily affect high
oxygen</tt>
<br><tt>mixtures, but due to oxygen toxity concers these are only used
at</tt>
<br><tt>shallow depth. As EAN50 at it's maximum operating depth is still
a</tt>
<br><tt>reasonable safe choice (narcosis wise) I conclude that this is
not</tt>
<br><tt>the case.</tt>
<p><tt>On the other hand if we are talking about bottom mixes where
nacosis
could</tt>
<br><tt>be a potential problem we don't exceed a ppO2 of 1.4bar (mostly
lower</tt>
<br><tt>anyway) and a ppN2 of 3bar. If we follow that rule and oxygen
would
be more</tt>
<br><tt>narcotic than nitrogen the worst case is like the narcosis
experienced
when</tt>
<br><tt>diving EAN32@11* -- I dont consider this a big threat to diving
safety.</tt>
<p><tt>Ok now back to the original question: If the mentioned table is
based on</tt>
<br><tt>the Meyer-Overton hypothesis (ie. lipid solubility) the value
should
be</tt>
<br><tt>cloth to 0.5 (ie. twice as narcotic as nitrogen, comparable to
Argon).</tt>
<p><tt>However, you should know that this hypothesis was proven wrong for
Helium</tt>
<br><tt>and Neon (prediced narcotic potency: 4.26 respectively 3.58). In
reality</tt>
<br><tt>both do not show ANY narcotic effect.</tt>
<p><tt>Another reason not to calculate the narcotic potency of oxygen
based
on</tt>
<br><tt>this hypothesis is that oxygen is metabolized and thus no inert
gas.</tt>
<p><tt>Albano et al. 1962 made an interesting experiment which indeed
supports</tt>
<br><tt>the assumption that oxygen is actualy less narcotic that nitrogen.
He put</tt>
<br><tt>6 man in a dry chamber and let them solve arithmethic equations
(summs) for</tt>
<br><tt>a certain amount of time.</tt>
<p><tt> &
nbsp;
Summs attempted (total) Correct Answers %Errors</tt>
<br><tt>Ambient pressure
245
;
227
;
7.3%</tt>
<br><tt>10bar Air 190
(=22%
decrease) 117(=48% decrease) 38.2%</tt>
<br><tt>10bar 4%O2/96%N2 152 (=38%
decrease)
80 (=65% decrease) 47.3%</tt>
<p><tt>There is evidence that O2 is narcotic, but it is not clear to which
extent</tt>
<br><tt>the effect is cauesd by the oxygen itself or by some synergetic
effects.</tt>
<br><tt>One of the mentioned synergetic effect is that high oxygen blocks
the</tt>
<br><tt>haemogobin carrier mechanism. The increased pACO2 will potentiate
nitrogen</tt>
<br><tt>narcosis.</tt>
<p><tt>Regards, Frank</tt>
<p><tt>P.S. Recommended reading: Physiology and Medicine of
Diving,</tt>
<br><tt>Chapter 7: Inert Gas Narcosis</tt>
<p><tt>Hesser CM, Fagraeus L, Adolfson J: "Roles of nitrogen, oxygen,
and</tt>
<br><tt>carbon dioxide in compressed-air narcosis" in Undersea Biomed Res,
1978</tt>
<p><tt>Abstract:</tt>
<br><tt>In an attempt to determine the roles of nitrogen, oxygen, and
carbon</tt>
<br><tt>dioxide in compressed-air narcosis, the effects on performance
(mental</tt>
<br><tt>function and manual dexterity) of adding CO2 in various
concentrations</tt>
<br><tt>to the inspired gas under three different conditions were studied
in</tt>
<br><tt>eight healthy male volunteers. The three conditions were: (1)
air</tt>
<br><tt>breathing at 1.3 ATA; (2) oxygen breathing at 1.7 ATA; and (3)
air</tt>
<br><tt>breathing at 8.0 ATA (same inspired O2 pressure as in (2)). By
relating</tt>
<br><tt>performance to the changes induced in end-tidal (alveolar) gas
pressures,</tt>
<br><tt>and comparing the data from the three conditions, we arrived at
the</tt>
<br><tt>following results and conclusions. A rise in O2 pressure to 1.65
ATA,</tt>
<br><tt>or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused
a</tt>
<br><tt>significant decrement of 10% in mental function but no consistent
effect</tt>
<br><tt>on psychomotor function. A rise in end-tidal PCO2 of 10 mmHg
caused
an</tt>
<br><tt>impairment of approximately 10% in both mental and psychomotor
functions.</tt>
<br><tt>The results suggest that, at raised partial pressures, all three
gases</tt>
<br><tt>have narcotic properties, and that the mechanism of CO2 narcosis
differs</tt>
<br><tt>fundamentally from that of N2 and O2 narcosis.</tt>
<br> </html>
--------------152C2917E6AFAC42C40C7143--
--
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]