Blood processing systems and methods that alternate flow of blood component and additive solution through an in-line leukofilter

1. A blood processing method comprising the steps of

(a) conveying blood cells from a blood cell source into a blood component collection flow channel that includes a blood cell storage container and an in-line filter to remove leukocytes from blood cells before entering the blood cell storage container,

(b) conveying additive solution from an additive solution source into the blood component collection flow channel, and

(c) repeatedly alternating steps (a) and (b) according to a pre-established pumping sequence to mix the additive solution with the blood cells at a substantially constant ratio.

2. A method according to claim 1

further including a step (d) comprising terminating step (a) when a desired volume of blood cells has been conveyed from the blood cell source and performing step (b) to flush residual blood cells from the filter into the blood cell storage container.

3. A method according to claim 1

further including a step of holding the filter in a restraining fixture during steps (a) and (b).

4. A method according to claim 1

further including a step of deriving a value reflecting volume of blood cells present in the blood cell collection container after passage through the filter as a percentage of volume of blood cells conveyed from the blood cell source to the filter.

5. A method according to claim 1

wherein the blood cells comprise red blood cells.