X-Message-Number: 14544
Date: Mon, 25 Sep 2000 14:36:09 EDT
Subject: storage of vitrified patients

Marta Sandberg asks

>How damaging would fluctuations in temperature be to the [vitrified] 

Although the question was not addressed to me, Cryonics Institute has an 
interest in potential new requirements, and research in this direction is on 
our to-do list, with some theoretical work already done.

It has been suggested that vitrified patients should be stored at higher than 
liquid nitrogen temperature--perhaps around - 135 C--for several possible 
reasons. One is to avoid cracking, which occurs more easily at lower 
temperatures, especially if cooling is rapid. (Our own procedures, however, 
using liquid nitrogen storage, do not show any cracking, although they do 
show other damage.) 

Another possible reason is that, depending on the specific cryoprotectant and 
its concentration and cooling rate, lower temperatures might result in 
freezing rather than vitrification. We have new types of storage unit on the 
drawing board that would offer passive stability at an intermediate 
temperature, but the capital cost would be higher than currently and the 
maintenance cost is not yet clear.  

A third possible reason is that rewarming (when the time comes) without 
"devitrification" might be easier if started from a higher temperature.

A fourth possible reason is that cooling below - 135 C (unnecessarily) might 
introduce or exacerbate damage of one kind or another for presently unknown 
reasons. (At various temperature ranges, under various conditions, there are 
types of cooling damage distinct from freezing damage.)  

Robert Ettinger
Cryonics Institute
Immortalist Society

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