X-Message-Number: 1112
Subject: CRYONICS - Freezing/Thawing Technique
From:  (Edgar W. Swank)
Date: Fri, 07 Aug 92 15:14:31 PDT

I thought I would add my 2-cents worth to the recent discussions about
possible improvements to current freezing techniques.
First, note that we already have good freezing/thawing technology for
single cells (sperm) or small groups of cells (embryos). The problems
occur when we try whole organisims because we can't freeze (or thaw)
all the cells in a whole organism as fast or as uniformly.
I note that the nature has already solved providing a necessary
environment for each of our cells by means of the circulatory system.
Unfortunately, current freezing technique clogs up the circulatory
system with ice and frozen perfusate chemicals. The only thawing
technique we can currently imagine requires an army of nanotech
ice-chippers to re-open the circulatory system before resuscitation of
cells can proceed.
My proposal is that we at some point in the freezing process change
from a liquid perfusate to a gas (such as helium) which will remain
a gas down to LN2 temperatures. Use of a cold gas through the
circulatory system will probably provide the most uniform cooling
possible, all the way down to LN2.
One problem changing from a liquid to a gas is bubbles (emboli) caused
by surface tension and the likelihood that large sections of the
circulatory system will remain full of liquid while gas is passing
through other sections.  There is a lot of room for experimentation
trying to find fluids of low surface tension and/or high volatility to
substitute before changing to gas phase.  One solution might be to
enclose the entire body in a (partial) vacuum chamber.  At low enough
pressure, water will change to vapor at any temperature above
In any case, once the technique is perfected, we will have a method
of quickly and uniformly introducing cryoprotectants to every cell,
lowering temperature of all cells, and finally achieving LN2
temperature with the circulatory system down to the fine capillaries
free and clear.  It's my hope that then revival might be achieved
by essentially a reversal of the above process. The clear circulatory
system could be warmed quickly and uniformly by circulating gas up to
around the ice point. Then liquid phase (without bubbles) would be
re-introduced, possibly by filling the system with water vapor under
vacuum, then releasing the vacuum. Then you wash out the
cryoprotectants, introduce blood or blood substitute, warm to body
temperature and attempt to revive.
It would be my hope that research along this line might provide
a demonstration of cooling a complete organism to LN2 temperatures and
revival in the near term, without waiting for development of advanced
I mentioned this idea to Trans-Time researcher Paul Segal a few years
ago.  He thought he remembered some experimentation with gas perfusion
in preserving kidneys, but couldn't recall much detail.

 (Edgar W. Swank)
SPECTROX SYSTEMS +1.408.252.1005  Silicon Valley, Ca

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