X-Message-Number: 5067
From: 
Date: Sun, 29 Oct 1995 13:09:45 -0500
Subject: mildly hyperbaric freezing

Here's a wild idea; maybe someone out there can tell me right off the bat why
it won't work, or that it has been broached before.

Background: Slow freezing tends to produce movement and mixing of material,
obscuring or perhaps even destroying information. Hyperbaric methods can
produce very quick solidification, but Greg Fahy and Harry Waitz e.g. have
used very high pressures, which tend themselves to be damaging, and complete
success has eluded them.

Now suppose we lower our sights a bit, and aim just to minimize mixing and
information degradation; could this be done using mild overpressures? My
reference books are not unpacked yet, so I don't have numbers available, but
in qualitative terms it might go something like this:

First we cool the patient as usual to near freezing. Then we put him in a
hyperbaric chamber and pressurize him just enough to lower the effective
freezing point a little. Then we cool him down to the new freezing point and
release the pressure. He freezes almost instantly, producing damage including
small intracellular ice crystals,  but there isn't time for much movement or
mixing of materials, so presumably there is a high level of preservation of
information or relatively easy inferrability.  (Then of course we cool
further for storage in liquid nitrogen.) (This procedure might be combined
with a relatively low level of cryoprotectant perfusion.)

How much do we need to depress the (average or minimum) freezing point of the
body's solutions? Just enough so that measuring and controlling the
temperature isn't too difficult--perhaps several degrees. Not having my
tables at hand, I don't remember how much pressure that would require, but
perhaps only a few atmospheres--not very difficult or expensive.

Ready for the firing squad.

Robert Ettinger


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