X-Message-Number: 5084
Date: Wed, 1 Nov 1995 01:03:02 -0500 (EST)
From: Ben Best <>
Subject: Back to high pressure tactics

    Robert Ettinger's "mildly hyperbaric freezing" suggestion is similar
to what I presented as potential use of pressure number (2) on page 20
of my piece "High Pressure Cryonics" in the Autumn 1994 issue of 
CANADIAN CRYONICS NEWS. In discussing this idea I raised the point 
about heat of fusion (as Brian Wowk has done). In the Winter 1995 issue
of CANADIAN CRYONICS NEWS I experienced the "firing squad" in the form of
a letter from Dr. Fahy in which he said (page 9) "rapid freezing is 
utterly different from vitrification", adding "Even a passing familiarity
with phase diagrams would have prevented this absurd idea from appearing
in print."

    But Robert has not argued that this procedure might cause vitrification,
he has instead offered it to "reduce freezing damage". I can't say for
certain that his idea would not *reduce* freezing damage, but it is 
an open question as to whether the reduction great enough to be worth
the effort. Water is not very viscous at freezing temperatures, and 
I'm not sure that the effects of a rapid pressure change would be 
propagated through the liquid rapidly enough to reduce crystal formation
or to reduce the damaging effects of ice crystals. The reason that 
Audrey Smith was able to turn 60% of hamster brains into ice was that 
*slow* freezing allowed the pure ice to form *outside* the cells. It 
is intracellular freezing that does the most damage. And, of course, 
intra and extra cellular fluids are not pure water, but are salts -- which
depress freezing point. NaCl has a eutectic temperature of -21.6C and 
CaCl2 has a eutectic temperature of -55C. None of these points mean
that Robert's suggestion would be of no value, but they do imply that
they might not be as valuable as an initial uncritical examination of
the idea might lead one to believe.

    Robert added that "this procedure might be combined with a relatively
low level of cryoprotectant perfusion". Why a "low level"? With a good
level of cryoprotectant, the "freezing point" (closer to vitrification 
temperature) would be considerably lower and the liquid would be 
considerably more viscous. Thus, the use of this technique could give
us a "freezing" which causes some level of damage mid-way between 
freezing with cryoprotectant and vitrification. I think the heat of 
fusion would be lessened -- and in any case would not be great enough
to eliminate the benefit under these conditions.

     I think the main problem with these high pressure methods is
that they could involve extremely awkward procedures requiring 
extremely expensive equipment. The work of Dr. Fahy on kidney vitrification
without this expensive overhead is so promising that is would be a shame
to blow vast amounts of money on equipment to somewhat *reduce* damage 
when the same money has the potential to *eliminate* freezing damage
and maybe even retain viability.

                       -- Ben Best () 


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