Abstract P137: Rapid Cooling Technology: Ice-slurry on Demand
Goal: Animal studies suggest that maximal benefit from hypothermia is achieved when hypothermia is induced during the intra-arrest period before ROSC. Inducing hypothermia before ROSC is a daunting engineering task, as 280 Kcal of energy need to be removed from a 70 kg human to achieve the 4 degrees Celsius of cooling. In a 5 minute timeframe this translates into 3.9 KW of power that needs to be applied to the body. Space and electrical power are significantly limited in the pre hospital scenario. Ice-particulate slurry is a promising phase change coolant that delivers 50% more cooling power per unit volume as ice cold saline. The goal of this project was to create a device that can create a pumpable 50% ice-saline slurry for use as a human coolant on demand from room temperature saline without the requirement of significant electrical power for refrigeration.
Methods: Dry ice is used to supply the cooling power for the slurry on demand device. A cooling coil is submerged in a dry ice-alcohol bath. A secondary coolant is re-circulated between the submerged cooling coil and a heat exchanger in the device. Saline flows through the heat exchanger in the slurry on demand device, and is cooled to its phase transition temperature. The dendritic ice crystals that form in the heat exchanger are then smoothed by the add-mixing of higher concentration saline.
Results: The presented device is capable of creating ice-saline slurry from room temperature saline. The ice content can be controlled by changing both the coolant and the saline flow rates. Heat transfer rates and over-all cooling capacity are dependent on mean particle size and ice volume fraction.
Conclusions: It is feasible to create ice slurry on demand without significant electrical power needs. Because of the lowered electrical needs, this design has potential for use in the pre-hospital setting. Additionally, the heat transfer measurements suggest that an appropriate dosage of 50% ice saline slurry with particles smaller than 100 um could be delivered to a patient in 10 minutes or less.