Optimum Conditions for the Efficacy and Safety of Cryofiltration Apheresis: An Analysis of Circuit Temperatures Depending on Plasma Flow Rate and Cooling Coil Lengths/Turns

A system providing both appropriate cooling and warming are needed for the efficacy and safety of cryofiltration ( CF ) plasmapheresis. We measured some points of CF circuit temperatures with varying plasma flow rates ( Q P  = 10–40 mL/min) and the numbers of connecting cooling coils (one or two) under the conditions of blood flow rate ( Q B ) 100 mL/min with 7700‐mm coil length, 19 turns, and 50‐mL priming volume. We measured the respective temperatures of each point of starting/returning for an extracorporeal circuit ( T A / T V ), intracooling coil ( T C ), and post‐plasma fractionator ( PF ) ( T PF ). The subtraction of T V from T A ( ΔT ) was used as an indicator of safe return. There were no significant differences in T C , T PF , or ΔT in accordance with each Q P between that of one and two coils. All of the T c values under the condition Q P  ≤ 20 mL/min achieved <4°C. The T PF under the condition Q P  ≥ 20 mL/min was not significantly different compared to that of Q P 30 mL/min (the lowest condition). Although the ΔT increased depending on the Q P increase, the ΔT under the condition Q P  ≤ 15 mL/min was not significantly different from that of the control (one‐way double‐filtration plasmapheresis [ DFPP] ) group. We conclude that (i) one coil is enough for effective cooling in CF , and (ii) an ideal Q P that fulfills the required conditions for both effective cooling and sufficient warming of returning fluid does not exist, but Q P from 15 to 20 mL/min may be a relevant range.