Method and apparatus for controlling the flow rate of washing solution during the washing step in a blood centrifugation bowl

A method of washing blood mixed with undesirable elements not normally found in healthy whole blood to remove the undesirable elements, the method comprising:

• separating the blood into components according to relative densities of the components with a rotating centrifuge bowl;
• allowing fluid to exit the bowl through a port, the exiting fluid having a concentration of undesirable elements;
• setting an initial flow rate of washing solution in accordance with a size of the centrifuge bowl;
• flowing washing solution into the centrifuge bowl at the initial flow rate;
• monitoring the fluid exiting the bowl with an optical sensor having an output signal indicative of the composition of the exiting fluid;
• and
• increasing the flow rate of the washing solution relative to the initial flow rate if the optical sensor has an output signal indicative of no red blood cells spilling into the exit fluid;
• decreasing the flow rate of the wash solution relative to the initial flow rate if the optical sensor has an output signal indicative of slight red blood cell spilling into the exit fluid as a function of the output signal,
• decreasing the flow rate of the washing solution to zero for a period of time if the optical sensor has an output signal indicative of massive red blood cells spilling into the exiting fluid;
• and
• restarting the washing solution after the period of time has passed.