System for blood separation with replacement fluid apparatus and method

1. A method of providing a controlled amount of blood replacement fluid to a blood donor comprising:

providing a disposable blood processing set for use on a centrifugal blood processing device, said disposable set comprising:

a blood separation chamber adapted to be mounted on a rotor of said centrifugal blood processing device;

a blood inlet line adapted to be coupled to a blood donor and to an inlet pump on said centrifugal blood processing device;

an anti-coagulant line in fluid communication with said inlet line, said anti-coagulant line being adapted to be fluidly coupled to a supply of anti-coagulant and being further adapted to be coupled to an anti-coagulant pump on said centrifugal blood processing device;

a reservoir adapted to be coupled to at least one sensor for detecting a level of fluid in said reservoir; a return line in fluid communication with said reservoir, said return line being adapted to be coupled to said blood donor and to a return pump on said centrifugal blood processing device;

a red blood cell line in fluid communication with said blood separation chamber and said reservoir;

a collect line in fluid communication with said blood separation chamber and in selective communication with said reservoir and a collect bag, said collect line being adapted to be coupled to a collect pump;

a plasma line in fluid communication with said blood separation chamber and with said reservoir, said plasma line being adapted to be coupled to a plasma pump; and

a replacement fluid line in fluid communication with said reservoir and adapted to be placed in fluid communication with a source of replacement fluid;

mounting said disposable blood processing set on said centrifugal blood processing device;

removing whole blood from said donor through said inlet line;

providing anti-coagulant to said whole blood in said inlet line;

measuring the flow of said whole blood and said anti-coagulant in said inlet line;

separating said whole blood and said anti-coagulant into a plurality of blood components in said separation chamber;

flowing red blood cells from said separation chamber into said reservoir;

flowing a first blood component from said separation chamber into said reservoir;

measuring the flow of said first blood component into said reservoir;

removing a second blood component from said separation chamber;

measuring the flow of said second component;

selectively flowing at least part of said second component into said reservoir;

selectively flowing replacement fluid into said reservoir;

periodically flowing contents of said reservoir into said return line;

measuring the flow of said contents;

determining a quantity of replacement fluid delivered to said donor from said measured inlet line flow, first blood component flow, collect flow and return flow.

2. The method of claim 1 wherein the step of selectively flowing replacement fluid into said reservoir comprises allowing said replacement fluid to flow without mechanical assistance.

3. The method of claim 2 wherein said replacement fluid flows by gravitational force alone.

4. The method of claim 1 wherein the step of measuring the flow of said contents comprises counting revolutions of a peristaltic pump.

5. The method of claim 1 wherein said step of periodically flowing contents of said reservoir into said return line further comprises

flowing the contents of said reservoir during a first period of time when replacement fluid is not flowed into said reservoir and

flowing the contents of said reservoir during a second period of time when replacement fluid is flowed into said reservoir.

6. The method of claim 5 wherein said first and second periods of time alternate.

7. The method of claim 6 wherein said first period is at least as long as said second period.

8. The method of claim 5 wherein each of said periods comprise at least one cycle, each cycle comprising a discrete step of removing whole blood and a discrete step of flowing contents of the reservoir into the return line.

9. The method of claim 8 wherein the ratio of the number of cycles in said first period to the number of cycles in said second period is at least 1 to 1.