X-Message-Number: 2099
Date: Tue, 13 Apr 93 10:30:30 CDT
From: Brian Wowk <>
Subject: CRYONICS Cooldown Capsules

        Alcor cools its patients below freezing by immersing them in a 
bath of stirred silicone oil to which dry ice is slowly added.  This 
method ensures that the patients' temperature is reduced rapidly and 
uniformly to -79'C (dry ice temperature).  The process is typically 
complete in 36 hours, and costs (according to Alcor's "Blue Book") 
about $1000 for whole body patients.    
 
        Final cooling from -79'C to -196'C is achieved by suspending 
the patient in a dewar and slowly decreasing the ambient air 
temperature by adding LN2 under computer control (the computer control 
recently added by Keith Henson).  The air (actually nitrogen vapor) 
must be vigorously stirred to prevent stratification.  This process is 
complex, labor-intensive, and expensive.  It requires about two weeks 
and costs $7000 for whole body patients (most of the cost being a 
dewar usage charge).
 
        I would like to suggest a way that a -130'C Cold Room can 
further reduce the cost of doing cryonics.  After reaching -79'C, the 
patient can be removed from the silicone oil and placed in a "cooldown 
capsule" with about 6" of fiberglass insulation wrapped around them.  
The capsule is then lowered into the Cold Room where the patient will 
cool at a rate of about 50 watts, or 1'C per hour.  This is the 
initial cooling rate.  Because the rate of cooling is proportional to 
the temperature difference between the patient and -130'C, the patient 
temperature will follow a slow exponential approach to -130'C with 
-128'C reached in about one week.  This is nature's own automation; it 
requires no control system and no supervision.   
 
        The cost and security advantages are obvious.  The patient is 
stored safely underground in the Cold Room during the cooldown, and 
expensive dewars are no longer required.  The savings will accrue 
quickly as our caseload increases and we don't have to buy new dewars 
to cool multiple patients simultaneously.  If the Blue Book accounting 
is correct, using the Cold Room instead of a dewar for cooldowns will 
knock at least $4000 off the front-end costs of suspension.  This is 
significant because front-end savings compound over time.  For 
example, the nominal interest on $4000 can reduce storage costs by 
$150 a year (about *half* the total storage cost in a Cold Room).  
 
        This is just one more reason to build a Cold Room.
 
                                                --- Brian Wowk

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=2099