In November, Steve Graber reported on a table cooldown test to -80C using saline water which demonstrated that the water bags in the cooldown chamber experienced difficulty passing through the ice temperature barrier, resulting in a very long cooldown process. Ultimately the test was stopped before the bags reached any appreciable cooling. Additionally, the research and development team noticed the table was cooling the leg portion much quicker than the remainder of the table.
The test was designed to more closely approximate the cooling characteristics of an actual patient scenario by using a mixture of anti-freeze and water in a 70/30 mix, rated to -65C. Steve’s test was run in essentially the same fashion as the previous run with identical LN2 consumption (two 200-liter dewars), and the data collection continued for an additional day to record the warmup segment. The table cooling tuning has been slightly over-corrected with the head and torso areas now cooling more quickly than the leg area. This should now allow him to dial in corrected vent opening settings for even cooling across the table. In the test the team noticed a significant improvement in the temperature drop vs saline water. At the end of our 10 hour test both the head and torso bags are nearing terminal temperature and the leg bag lagging behind. We achieved close to -80C cooling on our test bladders using LN2 at about the same rate as our current cooldown equipment.