Multi-unit blood processor with volume prediction

1. A method of predicting the volume of a component separated from whole blood, the method comprising:

sensing, at a known radial location, a fluid pressure in a separation cavity containing whole blood using a pressure sensor in a wall of the separation cavity, the pressure sensor comprising a flexible membrane that moves in response to pressure changes in the cavity and such membrane being connected to a pressure transducer;

predicting the volume of the whole blood from the sensing the fluid pressure step and an outboard volume located between the sensor and the bottom of the separation cavity;

separating the whole blood into at least a first and second component;

expressing the first separated component from the separation cavity to a collection cavity using an expandable chamber in the separation cavity, the expandable chamber being connected to a hydraulic circuit, wherein a pressure gauge is connected to the hydraulic circuit for measuring hydraulic pressure therein;

sensing the movement of the first separated component;

determining the volume of the expressed first separated component from the sensing the movement step; and

predicting the volume of the second component remaining in the separation cavity from the predicted volume of the whole blood and the determined volume of the expressed first separated component.

2. The method of claim 1 wherein the sensing the movement of the first separated component comprises:

sensing the leading edge of the expressed first component by detecting the presence of fluid; and

sensing the trailing edge of the expressed first component by detecting the presence of components not in the first expressed component.

3. The method of claim 2 wherein the step of sensing the leading edge comprises optically sensing the leading edge with a photocell.

4. The method of claim 2 wherein the step of sensing the trailing edge comprises optically sensing the trailing edge with a photocell.

5. The method of claim 3 wherein the step of sensing the leading edge comprises locating the photocell to detect fluid in tubing between the separation cavity and the collection cavity.

6. The method of claim 4 wherein the step of sensing the trailing edge comprises locating the photocell near the exit of the separation cavity.

7. The method of claim 1 wherein the separating step comprises centrifugally separating the whole blood.

8. The method of claim 1 wherein the separating further comprises separating the whole blood into at least a first, second and third component, and the method further comprises:

expressing the third separated component from the separation cavity to the collection cavity after the step of expressing the first separated component;

sensing the movement of the third separated component;

determining the volume of the expressed third separated component from the sensing the movement of the third separated component step;

predicting the volume of the second component remaining in the separation cavity from the predicted volume of the whole blood, the predicted volume of the expressed first component and the predicted volume of the expressed third component.

9. The method of claim 8 wherein, the first component is plasma, the third component is platelets and the second component is red blood cells.

10. The method of claim 1 wherein the first component is plasma and the second component is red blood cells.

11. The method of claim 9 wherein the sensing the movement of the first separated component comprises:

sensing the leading edge of the plasma by detecting the presence of the plasma; and

sensing the trailing edge of the plasma by detecting the presence of platelets.

12. The method of claim 11 wherein the sensing the movement of the third separated component comprises:

sensing the leading edge of the platelets by detecting the presence of the platelets; and

sensing the trailing edge of the platelets by detecting the presence of red blood cells.

13. The method of claim 9 wherein the sensing the movement of the first separated component comprises:

sensing the leading edge of the plasma by detecting the presence of the plasma; and

sensing the trailing edge of the plasma by detecting the presence of a cellular component.

14. The method of claim 1 wherein the step of sensing the fluid pressure comprises:

sensing, with the pressure sensor, the fluid pressure in a separation bag containing the whole blood; and

the step of expressing the separated first component comprises expressing the first component from the separation bag in the separation cavity to a bag in the collection cavity.

15. The method of claim 8 wherein the step of sensing the fluid pressure comprises:

sensing, with the pressure sensor, the fluid pressure in a separation bag in the separation cavity; and

the step of expressing the separated first component comprises expressing the first component from the separation bag in the separation cavity to a first bag in the collection cavity; and

the step of expressing the separated third component comprises expressing the third component from the separation bag in the separation cavity to a second bag in the collection cavity.

16. The method of claim 15 wherein the expressing steps comprise:

squeezing, with the expandable chamber, the separation bag to transfer the first component to the first bag and to transfer the third component to the second bag.