Re: cryonics risk/payoff matrix

Date: Sun May 13 2001 - 15:57:58 MDT

Dave Sill wrote:

> me> This [freezing and reviving a *healthy* human without any damage at all]
> me> is impossible.
> I'd like to see your proof.

Volume/surface ratio of a human indicates you can't cool a human body via
surface transfer without requiring some rather fancy fractal heat exchanger
inserted into your body (recursive pipes going down all the way to
(sub)micrometer scale). Even then, you'll probably need perfusion with
iceblockers prior to that and removal of said iceblockers after devitrification
(could use ohmic heating or chemical enthalpy (catalyzed oxygen/hydrogen
combustion in situ)). Of course, this is quick, since the fractal plumbing
can double as cryoprotectant loading/unloading infrastructure.

Now this is asking for some fancy (stiff (since high-throughput), intelligent
(inserting and retracting that heat exchanger is rather nontrivial)) NEMS
plumbing, and even then, there will be damage. You'll live, but I very much
would not like to go through the ordeal unaesthesized. It would hurt like
the dickens, and the aftermath of the process will weigh upon you heavily
for days.

So unless you shut down the higher cortical function for hours to days,
to repair the bulk of the damage occured, allowing the patient to recover
until enabling brain activity, the procedure will be rather, er, disruptive.

The organ vitrification thing is rather different. It's a single organ,
monotyped tissue allows you to optimize cryoprotectant solutions in a way
that is impossible a complex system. Volume/surface ratio is way better than
a human (in absence of fractal heat exchangers). And you're willing to
tolerate a lot of tissue damage, because your alternative is 100% tissue
damage. A kidney doesn't think, and a brain with 50% of the cells taken
out of circulations will still produce an EEG.

So "without any damage at all" boundary conditions is rather harsh. It is
not being met by any imaginable technology, i.e. based on known physics.

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