by Ben Best
(Readers looking for good detailed case reports would do better to look at the case report for CI's 72nd Patient or CI's 69th Patient than at this one.)
Our 73rd patient was not in the kind of condition we would want, to say the least. She had been autopsied, her autopsied brain was in her abdomen and she had spent weeks in refrigeration before being shipped to CI in dry ice. Her son was aware that her chances for reanimation are much worse than for the typical cryonics patient, but he felt that a small chance is still better than no chance.
There was no possibility of perfusing this patient, so she was shipped to CI in dry ice. Despite being shipped in dry ice, she had not cooled to dry ice temperature when we received her. She was too solid for us to be able to insert a deep temperature probe, but a probe placed deep in her mouth indicated her temperature was about −20ºC.
We wrapped her in a sleeping bag. When we are cooling a
vitrified patient it is best to cool as rapidly as
possible, but for straight freezing it is best to cool more slowly
-- not much faster than 1ºC per minute. The most damaging ice that
forms is the ice that forms inside of cells. When cooling is slow, ice forms
in the extracellular space rather than inside of cells because the best
nucleators for ice formation are outside of cells rather than inside
cells. With slow cooling most of the water leaves the cells, dehydrating
them, and then freezing.
|Cooling for 13.5 Hours|
The patient was cooled in our computer-controlled cooling box to about dry ice temperature (−79ºC) at about 9ºC per hour, then cooled to about −192ºC at about 16ºC per hour. Total time for cooling was 13.5 hours.
In order to reduce the amount of water vapor entering the cooling box as well as to increase thermal efficiency, Andy placed a long copper pipe on the vent hole. The copper pipe runs along 3 sides of the cooling box and has a copper valve at the end which can vent the nitrogen gas without much air (and water vapor) entering the cooling box. Andy also placed brackets at the top of the cooling box to hold foam board insulation and covered that with batten insulation.
The vent pipe worked fine until the ambient temperature in the cooling box reached cryogenic temperatures (below −100ºC) when the seal on the foam board broke causing the liquid nitrogen gas to shoot out the top rather than through the copper pipe. Nonetheless, the insulation provides some lasting improvement because the ambient temperature in the cooling box bottomed-out at −192ºC rather than at −191ºC -- as was seen for the previous patient. Also, when we removed the patient from the cooling box, there was no frost visible on her sleeping bag.
Better insulation and sealing in the future will hopefully bring
ambient temperature inside the box closer to liquid nitrogen boiling
|Pipe Around Cooling Box||End of Pipe||Insulation Seal|