Blood processing systems and methods using apparent hematocrit as a process control parameter

• US 6,059,979 A
• Filed: 10/30/1997
• Issued: 05/09/2000
• Est. Priority Date: 12/23/1991
• Status: Expired due to Term

• Current Assignee: Fenwal Incorporated (Fresenius SE & Co. KGaA)
• Original Assignee: Baxter International Inc.
• Inventors: Brown, Richard I.
• Primary Examiner(s): Drodge, Joseph W.
• Application Number:
  US08/960,674
• Time in Patent Office: 922 Days
• Field of Search: 210/85-87, 210/96.1, 210/143, 210/145, 210/149, 210/194, 210/195.1, 210/257.1, 210/512.1, 210/739, 210/767, 210/787, 210/789, 604/4-6, 604/65-67, 364/413.07, 364/554, 364/555, 364/564, 364/567, 364/569, 128/DIG. 13, 422/44, 494/1, 494/37
• US Class Current: 210/739
• CPC Class Codes: A61M 1/0209 Multiple bag systems for separating or storing blood components
• CPC Class Codes: A61M 1/0218 with filters
• CPC Class Codes: A61M 1/025 Means for agitating or shaking blood containers A61M1/0245 takes precedence; shaking in general B01F31/00
• CPC Class Codes: A61M 1/30 Single needle dialysis ; Reciprocating systems, alternately withdrawing blood from and returning it to the patient, e.g. single-lumen-needle dialysis or single needle systems for hemofiltration or pheresis
• CPC Class Codes: A61M 1/302 having a reservoir for withdrawn untreated blood
• CPC Class Codes: A61M 1/303 having a reservoir for treated blood to be returned
• CPC Class Codes: A61M 1/308 Volume control, e.g. with open or flexible containers, by counting the number of pump revolutions, weighing
• CPC Class Codes: A61M 1/3603 in the same direction
• CPC Class Codes: A61M 1/3624 Level detectors; Level control
• CPC Class Codes: A61M 1/3672 Means preventing coagulation
• CPC Class Codes: A61M 1/3693 using separation based on different densities of components, e.g. centrifuging
• CPC Class Codes: A61M 1/3696 with means for adding or withdrawing liquid substances during the centrifugation, e.g. continuous centrifugation
• CPC Class Codes: A61M 1/385 taking into account of the patient characteristics
• CPC Class Codes: A61M 2202/0071 product to be retained or harvested, e.g. by pheresis
• CPC Class Codes: A61M 2202/0092 starting product created by centrifuging
• CPC Class Codes: A61M 2202/0415 Plasma
• CPC Class Codes: A61M 2202/0427 Platelets; Thrombocytes
• CPC Class Codes: A61M 2205/331 used as turbidity change detectors, e.g. for priming-blood or plasma-hemoglubine-interface detection
• CPC Class Codes: A61M 2205/3344 Measuring or controlling pressure at the body treatment site
• CPC Class Codes: A61M 2205/3351 Controlling upstream pump pressure
• CPC Class Codes: A61M 2205/3355 : Controlling downstream pump pressure
• CPC Class Codes: A61M 2205/3393 : by weighing the reservoir
• CPC Class Codes: B01D 17/0217 : by centrifugal force
• CPC Class Codes: B01D 21/2405 : Feed mechanisms for settling tanks
• CPC Class Codes: B01D 21/245 : Discharge mechanisms for the sediments
• CPC Class Codes: B01D 21/26 : Separation of sediment aided by centrifugal force or centripetal forcecentrifuges B04B; cyclones B04C
• CPC Class Codes: B01D 21/262 : by using a centrifuge
• CPC Class Codes: B01D 21/34 : Controlling the feed distribution; Controlling the liquid level ; Control of process parameters
• CPC Class Codes: B01D 2221/10 : Separation devices for use in medical, pharmaceutical or laboratory applications, e.g. separating amalgam from dental treatment residues
• CPC Class Codes: B04B 13/00 : Control arrangements specially designed for centrifuges; Programme control of centrifuges control arrangements for feed, charge, or discharge B04B11/00
• CPC Class Codes: B04B 5/0442 : with means for adding or withdrawing liquid substances during the centrifugation, e.g. continuous centrifugation
• CPC Class Codes: B04B 7/08 : Rotary bowls centrifugal casting machines B22D

Abstract

Blood processing systems and methods separate whole blood into red blood cells and a plasma constituent within a rotating centrifugal separation device. The systems and methods convey whole blood into the separation device through an inlet path including a pump operable at a prescribed rate. The systems and methods remove plasma constituent from the separation device through an outlet path including a pump operable at a prescribed rate. The systems and methods derive a value H_b representing an apparent hematocrit of whole blood entering the separation device, where: ##EQU1## and where H_rbc is a value relating to hematocrit of red blood cells in the separation device. The systems and methods generate outputs and control commands based, at least in part, upon H_b.

Claims

1. A blood processing system comprising

a centrifugal separation device rotatable about a rotational axis at a controlled rate of rotation, the separation device having an area A,

an inlet path operable to convey whole blood at a determinable rate Q_b into the separation device for separation into red blood cells and a plasma constituent, the whole blood in the inlet path having an actual whole blood hematocrit value, the red blood cells in the separation device having an actual red blood cell hematocrit value,

an outlet path operable to remove plasma constituent from the separation device at a determinable rate Q_p at least in part while whole blood is conveyed into the separation device,

an outlet path operable to remove red blood cells from the separation device at least in part while whole blood is conveyed into the separation device and plasma is removed from the separation device,

a controller including a stage operable to derive a value H^rbc representing an apparent hematocrit of red blood cells within the separation device at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device, where:

space="preserve" listing-type="equation">H.sub.rbc =f(Q.sub.b,Q.sub.p,A,g,RBC)

where;

g represents a centrifugal acceleration factor based upon the controlled rate of rotation, and

RBC represents at least one red blood cell dependent factor not including the actual red blood cell hematocrit value,

the controller including a stage operable to derive a value H_b representing an apparent hematocrit of whole blood entering the separation device at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device, based upon a relationship among H_rbc, Q_b, Q_p, and not including the actual whole blood hematocrit value, expressed as follows;

##EQU44## and the controller including a stage operable to generate a control command at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device, based, at least in part, upon H_b.

2. A system according to claim 1

wherein the control command recirculates at least a portion of plasma constituent for mixing with whole blood conveyed into the separation device.

3. A system according to claim 1 wherein the control command controls Q_b.

4. A system according to claim 1 and further including an element that generates an output based, at least in part, upon H_b.

5. A system according to claim 4

wherein the output comprises a value η

representing efficiency of separation in the separation device, where;

##EQU45##

6. A system according to claim 1 wherein the value H_rbc represents apparent hematocrit of red blood cells in the separation device, where:

##EQU46## where;

q_b is inlet blood flow rate (cm³ /sec), which when converted to ml/min, corresponds with Q_b,

q_p is measured plasma flow rate (in cm³ /sec), which, when converted to ml/min corresponds with Q_p,

β

is a shear rate dependent term, and S_y is a red blood cell sedimentation coefficient (sec) and β

/S_y =15.8×

10⁶ sec_-1,

A is the area of the separation device (cm²),

g is the centrifugal acceleration (cm/sec²), which is the radius of the separation device multiplied by the rate of rotation squared Ω

² (rad/sec²), and

k is a viscosity constant=0.625, and K is a viscosity constant based upon k and another viscosity constant α

=4.5, where;

##EQU47##

7. A system according to claim 6 wherein the separation device is free of any sensor operable to measure the actual whole blood hematocrit value.

8. A system according to claim 1

wherein the inlet path is free of any sensor operable to measure the actual whole blood hematocrit value.

9. A blood processing system comprising

a centrifugal separation device rotatable at a controlled rate of rotation, the separation device having an area A,

an inlet path operable to convey whole blood at a determinable rate Q_b into the separation device for separation into red blood cells and a plasma constituent, the whole blood in the inlet path having an actual whole blood hematocrit value, the red blood cells in the separation device having an actual red blood cell hematocrit value,

an outlet path operable to remove plasma constituent from the separation device at a determinable rate Q_p at least in part while whole blood is conveyed into the separation device,

a recirculation path operable to recirculate at least a portion of the plasma constituent at a determinable rate Q_Recirc for mixing with whole blood conveyed into the separation device,

an outlet path operable to remove red blood cells from the separation device at least in part while whole blood is conveyed into the separation device and plasma is removed from the separation device,

a controller coupled to the recirculation path operable to maintain Q_Recirc to achieve a desired hematocrit H_i for whole blood conveyed into the separation device at least in part while red blood cells are removed from the separation device and plasma constituent removed from the separation device is recirculated for mixing with whole blood conveyed into the device, as follows:

##EQU48## where H_b is a value representing an apparent hematocrit of whole blood entering the separation device based upon a relationship among H_rbc, Q_b, Q_p, and not including the actual whole blood hematocrit value, expressed as follows;

##EQU49## and where H_rbc is a value relating to an apparent hematocrit of red blood cells in the separation device where;

space="preserve" listing-type="equation">H.sub.rbc =f(Q.sub.b, Q.sub.p, A, g, RBC)

where;

g represents a centrifugal acceleration factor based upon the controlled rate of rotation, and

RBC represents at least one red blood cell dependent factor not including the actual red blood cell hematocrit value.

10. A system according to claim 9

wherein the value H_rbc represents apparent hematocrit of red blood cells in the separation device, where:

##EQU50## where;

q_b is inlet blood flow rate (cm³ /sec), which when converted to ml/min, corresponds with Q_b,

q_p is measured plasma flow rate (in cm³ /sec), which, when converted to ml/min corresponds with Q_p,

β

is a shear rate dependent term, and S_y is a red blood cell sedimentation coefficient (sec) and β

/S_y =15.8×

10⁶ sec^-1,

A is the area of the separation device (cm²),

g is the centrifugal acceleration (cm/sec²), which is the radius of the separation device multiplied by the rate of rotation squared Ω

₂ (rad/sec²), and

k is a viscosity constant=0.625, and K is a viscosity constant based upon k and another viscosity constant α

=4.5, where;

##EQU51##

11. A system according to claim 10 wherein the separation device is free of any sensor operable to measure the actual blood hematocrit value.

12. A system according to claim 9

wherein the inlet path is free of any sensor operable to measure the actual whole blood hematocrit value.

13. A system according to claim 9

wherein H_i is no greater than about 40%.

14. A system according to claim 9

wherein H_i is about 32%.

15. A blood processing method comprising the steps of

rotating a centrifugal separation device at a controlled rate of rotation, the separation device having an area A,

conveying whole blood having an actual whole blood hematocrit value into the separation device at a determinable rate Q_b for separation into red blood cells and a plasma constituent, the red blood cells in the separation device having an actual red blood cell hematocrit value,

removing plasma constituent from the separation device at a determinable rate Q_p at least in part while whole blood is conveyed into the separation device,

removing red blood cells from the separation device at least in part while whole blood is conveyed into the separation device and plasma is removed from the separation device,

deriving at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device a value H_rbc representing an apparent hematocrit of red blood cells within the separation device where:

space="preserve" listing-type="equation">H.sub.rbc =f(Q.sub.b, Q.sub.p, A, g, RBC)

where;

g represents a centrifugal acceleration factor based upon the controlled rate of rotation, and

RBC represents at least one red blood cell dependent factor not including the actual red blood cell hematocrit value,

deriving at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device a value H_b representing an apparent hematocrit of whole blood entering the separation device based upon a relationship among H_rbc, Q_b, Q_p, and not including the actual whole blood hematocrit value, expressed as follows;

##EQU52## and generating a control command based, at least in part, upon H_b at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device.

16. A method according to claim 15

wherein the control command recirculates at least a portion of plasma constituent for mixing with whole blood conveyed into the separation device.

17. A method according to claim 15

wherein the control command controls Q_b.

18. A method according to claim 15

and further the step of generating an output based, at least in part, upon H_b.

19. A method according to claim 18

wherein the output comprises a value η

representing efficiency of separation in the separation device, where;

##EQU53##20.

20. A method according to claim 15 wherein the value H_rbc represents apparent hematocrit of red blood cells in the separation device, where:

##EQU54## where;

q_b is inlet blood flow rate (cm³ /sec), which when converted to ml/min, corresponds with Q_b,

q_p is measured plasma flow rate (in cm³ /sec), which, when converted to ml/min corresponds with Q_p,

β

is a shear rate dependent term, and S_y is a red blood cell sedimentation coefficient (sec) and β

/S_y =15.8×

10⁶ sec^-1,

A is the area of the separation device (cm²),

g is the centrifugal acceleration (cm/sec²), which is the radius of the separation device multiplied by the rate of rotation squared Ω

² (rad/sec²), and

k is a viscosity constant=0.625, and K is a viscosity constant based upon k and another viscosity constant α

=4.5, where;

##EQU55##

21. A method according to claim 20 wherein the method is free of a step of using a sensor to measure the actual whole blood hematocrit value in the separation device.

22. A method according to claim 15

wherein the method is free of a step of using a sensor to measure the actual whole blood hematocrit value in the inlet path.

23. A blood processing method comprising the steps of

rotating a centrifugal separation device at a controlled rate of rotation, the separation device having an area A,

conveying whole blood having an actual whole blood hematocrit value into the separation device at a determinable rate Q_b for separation into red blood cells and a plasma constituent, the red blood cells in the separation device having an actual red blood cell hematocrit value,

removing plasma constituent from the separation device at a determonable rate Q_p at least in part while whole blood is conveyed into the separation device,

recirculating at least a portion of plasma constituent from the separation device at a determinable rate Q_Recirc for mixing with whole blood conveyed into the separation device,

removing red blood cells from the separation device at least in part while whole blood is conveyed into the separation device and plasma is removed from the separation device,

controlling Q_Recirc to achieve a desired hematocrit H_i for whole blood conveyed into the separation device at least in part while red blood cells are removed from the separation device and plasma constituent removed from the separation device is recirculated for mixing with whole blood conveyed into the device, as follows:

##EQU56## where H_b is a value representing an apparent hematocrit of whole blood entering the separation device based upon a relationship among H_rbc, Q_b, Q_p, and not including the actual whole blood hematocrit value, expressed as follows;

##EQU57## and where H_rbc is a value relating to an apparent hematocrit of red blood cells in the separation device where;

space="preserve" listing-type="equation">H.sub.rbc =f(Q.sub.b, Q.sub.p, A, g, RBC)

where;

g represents a centrifugal acceleration factor based upon the controlled rate of rotation, and

RBC represents at least one red blood cell dependent factor not including the actual red blood cell hematocrit value.

24. A method according to claim 23

wherein the value H_rbc represents apparent hematocrit of red blood cells in the separation device, where:

##EQU58## where;

q_b is inlet blood flow rate (cm³ /sec), which when converted to ml/min, corresponds with Q_b,

q_p is measured plasma flow rate (in cm³ /sec), which, when converted to ml/min corresponds with Q_p,

β

is a shear rate dependent term, and S_y is a red blood cell sedimentation coefficient (sec) and β

/S_y =15.8×

10⁶ sec^-1,

A is the area of the separation device (cm²),

g is the centrifugal acceleration (cm/sec²), which is the radius of the separation device multiplied by the rate of rotation squared Ω

² (rad/sec²), and

k is a viscosity constant=0.625, and K is a viscosity constant based upon k and another viscosity constant α

=4.5, where;

##EQU59##

25. A method according to claim 24 wherein the method is free of a step of using a sensor to measure the actual whole blood hematocrit value in the separation device.

26. A method according to claim 23

wherein the method is free of a step of using a sensor to measure the actual whole blood hematocrit value in the inlet path.