X-Message-Number: 5076
Date: 31 Oct 95 00:38:34 EST
From: Mike Darwin <>
Subject: CRYONICS: flash freeze

Bob Ettinger writes:

>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.


It will take a fair amount of pressure and it won't be cheap.  If I remember
correctly (300 ATM) a la La Chatier (sp?) Effect yeilds a freezing point
depression of -20 C with 15% DMSO present.  If I recall correctly, the curve is
not linear.  I DO have reference books but also have a dog who, unless
micromanaged, will soon have his endotracheal tube out; something for which
neither he nor I are ready.


We have a chamber here big enough to do a human brain (barely) and pressurizable
to a max of 35, 000 psi.  It has built in cooling channels and about 8" thick
walls.  It cost (with pressurization system) about $75,000.  I understand cost
rises as the exponent of the chamber diameter :).

You will certainly get intracellular ice, but it will not stay small!  One of

the major drawbacks to low concentration DMSO or low glyc blood freezing methods

(in the absence of hyperbaria) is that the blood must be cooled very rapidly and
it must be stored at -135 or below (usually in LN2 vapor).  Why?  Because the
small crystals quite rapidly recrystallize into large ones.  This may not be a
problem from an inference standpoint.  I don't know.  I have watched it happen
under the cryomicroscope both personally and on videotape (the latter being
other peoples' work).  Father Luyet spent a lifetime examining this and related
phenomena.  I have a complete bound set of his journal BIODYNAMICA, and can
guarantee you that it is a good source of information on this topic.  Some
larger medical school and University libraries may have the whole set through
volume 10.


One thing I can tell you, at least after thawing intracellular ice doesn't leave
much :(.

Since Bob has offered his hide to the firing squad I'll do the same.  We all
know that decreasing atmospheric pressure causes water to boil at progressively
higher temperatures until it will boil at room temperature in a hard vacuum.  I

have always wanted to try the REVERSE of what Bob suggests: cool to near 0 C and
then PULL A VACUUM.  Will that cause the liquid to freeze instantly at a higher
point?  I may be exposing some embarassing lack of understanding of basic
physics.  But, as they say, no pain, no gain.

Mike Darwin


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