Replacement fluid control system for a blood fractionation apparatus and the like

摘要

An apparatus for separating and collecting plasma from whole blood includes a ratio control system which enables replacement fluid to be added by a replacement fluid pump within the apparatus to processed plasma-deficient blood at a predetermined ratio to the volume of plasma collected in a collection container. A transducer within the system develops an electrical signal frequency-dependent on the weight of the collected plasma. This signal is applied through a first rate multiplier circuit to the up-count input of a bidirectional counter. A second signal derived from a tachometer on the replacement fluid pump is supplied through a second rate multiplier circuit to the down-count input of the counter. A digital-to-analog converter converts the count in the counter to an analog control signal which controls the operation of the replacement pump motor. The multiplication factors of the rate multipliers are set by a user-operated switch to obtain a desired replacement ratio. In an alternative autologous mode the replacement pump is connected to withdraw plasma from the collection container and the system varies the pump speed to maintain a constant collected volume in the container as plasma is withdrawn for processing and return to the donor.