Method and Apparatus for Recirculating Elutriation Fluids

1 . A method of fractionating a blood product comprising:

loading a fluid chamber through its inlet with a blood product having at least first and second particles;

adding a low density fluid to the loaded blood product in the fluid chamber;

sedimenting the particles in the fluid chamber in accordance with their sedimentation velocities; and

re-circulating the low density fluid from the fluid chamber back to the inlet of the fluid chamber for use in the adding step.

2 . The method of claim 1 further comprising:

removing at least one of the first or second particles having the greater sedimentation velocity through the inlet of the fluid chamber leaving the other of the first and second particles in the fluid chamber.

3 . A method of claim 1 further comprising:

repeating the loading, adding, sedimenting, and re-circulating steps until all blood product has been fractionated.

4 . The method of claim 1 further comprising:

removing one of the first and second particles from the fluid chamber; and

collecting one of the first and second particles.

5 . The method of claim 4 further comprising:

concentrating one of the first and second particles prior to the collecting step.

6 . The method of claim 1 wherein the re-circulating step comprises:

adding the re-circulated low density fluid to a source container for the low density fluid.

7 . The method of claim 1 wherein the adding step comprises:

pumping low density fluid to the fluid chamber with a pump; and

the re-circulating step further comprises adding the re-circulated low density fluid fluidly above the pump prior to the pumping step.

8 . The method of claim 1 wherein the re-circulating step further comprises:

pumping the re-circulated fluid to the inlet of the fluid chamber.

9 . The method of claim 1 further comprising:

flowing some of the low density fluid to a waste bag prior to the re-circulating step.

10 . The method of claim 1 further comprising:

debulking one of the first and second particles through the inlet of the fluid chamber.

11 . A system for separating first particles from second particles in a blood product comprising:

a source of blood product having at least first and second particles;

a low density fluid source;

a collection container;

a fluid chamber having an inlet and an outlet;

a first conduit fluidly connecting the blood product source and the low density fluid source to the inlet of the fluid chamber;

a second conduit fluidly connecting the outlet of the fluid chamber to the collection container for separated particles; and

a re-circulation conduit fluidly connecting the outlet of the fluid chamber to the first conduit for re-circulating low density fluid back to the inlet of the fluid chamber.

12 . The system of claim 11 wherein the re-circulation conduit is connected to the low density fluid source to provide any re-circulated low density fluid to the first conduit.

13 . The system of claim 11 wherein the re-circulation conduit is connected to the first conduit and the second conduit.

14 . The system of claim 11 wherein the re-circulation conduit is connected to the first and second conduits and forms a re-circulation pump loop between the first and second conduits.

15 . A system of claim 11 further comprising

a particle concentrate line fluidly connected to the outlet of the fluid chamber; and

fluidly connected to the collection container.

16 . The system of claim 15 further comprising:

a separation vessel fluidly connected to the particle concentrate line and the collection container to concentrate the particles for collection.

17 . A disposable particle separation system comprising:

a first coupling adapted to be connected to a source of particles to be separated;

a second coupling adapted to be connected to a source of low density fluid;

a first conduit fluidly connected to the first and second couplings;

a fluid chamber fluidly connected to the first conduit wherein the fluid chamber further comprises

an inlet;

an outlet

a collection container;

a second conduit fluidly coupled to the fluid chamber outlet and the collection container;

a re-circulation line fluidly coupled to the second conduit and the first conduit.

18 . The disposable particle separation system of claim 17 wherein the fluid chamber further comprises:

a wall having a smooth interior surface extending between the inlet and outlet;

a maximum cross-sectional area in the wall wherein the wall tapers from the maximum cross sectional area to the inlet and from the maximum cross-sectional area to the outlet; and

the disposable particle separation system further comprises a particle concentrator fluidly connected to the outlet of the fluid chamber and to the second conduit.

19 . The disposable particle separation system of claim 17 further comprising:

a debulking conduit for receiving particles fluidly connected to the inlet of the fluid chamber.

20 . The disposable particle separation system of claim 19 further comprising:

a three-way connector for fluidly connecting the first conduit to the inlet of the fluid chamber and for fluidly connecting the debulking conduit to the inlet of the fluid chamber.

21 . The disposable particle separation system of claim 20 further comprising an inlet conduit connected to the inlet of the fluid chamber and to the three-way connector.

22 . The disposable particle separation system of claim 19 further comprising a debulking collection container fluidly connected to the debulking conduit.

23 . The disposable particle separation system of claim 17 wherein the particles to be separated include white blood cells to be separated into white blood cell subsets.

24 . The disposable particle separation system of claim 19 wherein the particles received by the debulking conduit include red blood cells.

25 . A method of separating a white blood cell product having white blood cells and red blood cells into white blood cell subsets comprising:

loading a fluid chamber through its inlet with the white blood cell product;

adding a low density fluid to the white blood cell product;

sedimenting the white blood cells and the red blood cells in the white blood cell product in the fluid chamber;

re-circulating a portion of the low density fluid added to the white blood cell product to be used in the adding step; and

collecting the white blood cells.

26 . The method of claim 25 further comprising

separating by elutriation the white blood cells into white blood subsets prior to the collecting step.

27 . The method of claim 26 further comprising:

removing the separated white blood cell subsets through the outlet of the fluid chamber;

providing the removed separated white blood cell subsets to a particle concentrator;

separating in the particle concentrator fluid from the white blood cell subsets prior to the collecting step.

28 . A method of claim 25 further comprising:

removing the sedimented red blood cells through the inlet of the fluid chamber.