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I come out of my "lurker" corner to comment on this topic. A disclaimer is
that although as a lipid neurochemist (Prof. of Biochem and Biophys. and of
Neurobiology) I am competent to read and evaluate the literature in this
area, I have not done so. Nevertheless, the concept of nitrogen under
pressure as an anaesthetic is well known and is presumed to be due to its
lipid solubility, it intercalates into the membrane and causes it to
"spread". This is presumed to alter the operation of ion channels (maybe at
synaptic junctions) and this perturbation in information processing results
in narcosis (similar to the results of alcohol which also is lipid soluble).
High pressure, from a gas mixture whose components are not as soluble in
lipids as is nitrogen, counteracts the membrane spreading by forcing the
nitrogen back out of the membrane. HPNS is, I assume, due to the opposite of
membrane spreading when the membrane is just compressed - hence the idea of
adding back small amounts of nitrogen to heliox when at great depth. Even
my casual glance at the relevant chapters in Bennet and Elliot (I stopped at
the library a few minutes ago) indicates this is a most murky field. I will
try to get a better look at this material in the near future and post if this
version is far off.
Pierre Morell
Instructor PADI 69985 SSI 5202
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