Imperforate bowl: centrifugal separators – With means for filtering
Reexamination Certificate
2001-01-18
2003-10-07
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
With means for filtering
C494S037000, C494S067000
Reexamination Certificate
active
06629919
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to centrifugation bowls for separating blood and other biological fluids. More specifically, the present invention relates to a centrifugation bowl having an improved core that aids in separating and harvesting individual blood components from whole blood.
2. Background Information
Human blood predominantly includes three types of specialized cells (i.e., red blood cells, white blood cells, and platelets) that are suspended in a complex aqueous solution of proteins and other chemicals called plasma. Although in the past blood transfusions have used whole blood, the current trend is to collect and transfuse only those blood components or fractions required by a particular patient. This approach preserves the available blood supply and in many cases is better for the patient, since the patient is not exposed unnecessarily to other blood components and the risks of infection or adverse reaction that may be attendant with those other components. Among the more common blood fractions used in transfusions, for example, are red blood cells and plasma. Plasma transfusions, in particular, are often used to replenish depleted coagulation factors. Indeed, in the United States alone, approximately two million plasma units are transfused each year. Collected plasma is also pooled for fractionation into its constituent components, including proteins, such as Factor VIII, albumin, immune serum globulin, etc.
One method of separating whole blood into its various constituent fractions, including plasma, is “bag” centrifugation. According to this process, one or more units of anti-coagulated whole blood are pooled into a bag. The bag is then inserted into a lab centrifuge and spun at very high speed, subjecting the blood to many times the force of gravity. This causes the various blood components to separate into layers according to their densities. In particular, the more dense components, such as red blood cells, separate from the less dense components, such as white blood cells and plasma. Each of the blood components may then be expressed from the bag and individually collected.
Another separation method is known as bowl centrifugation. U.S. Pat. No. 4,983,158 issued Jan. 8, 1991 to Headley (“the '158 patent”) discloses a centrifuge bowl having a seamless bowl body and an inner core including four peripheral slots located at the top of the core. The centrifuge bowl is inserted in a chuck which rotates the bowl at high speed. Centrifugation utilizing this device is accomplish by withdrawing whole blood from a donor, mixing it with anticoagulant and pumping it into the rotating centrifuge bowl. The more dense red blood cells are forced radially outward from the bowl's central axis and collected along the inner wall of the bowl. The less dense plasma is displaced inwardly toward the core and allowed to escape through the slots. The plasma is forced through an outlet of the bowl and is separately collected.
The centrifugation bowl of the '158 patent can also be used to perform apheresis. Apheresis is a process in which whole blood is withdrawn from a donor and separated and the blood components of interest are collected while the other blood components are retransfused into the donor. By returning some blood components to the donor (e.g., red blood cells), greater quantities of other components (e.g., plasma) can generally be collected.
Despite the centrifugation system's generally high separation efficiency, the collected plasma can nonetheless contain some residual blood cells. For example, in a disposable harness utilizing a blow-molded centrifuge bowl, the collected plasma typically contains from 0.1 to 30 white blood cells and from 5,000 to 50,000 platelets per need to keep the bowl's filling rate in excess of 60 milliliters per minute (ml/min.) to minimize the collection time, thereby causing slight re-mixing of blood components within the bowl.
Another method of separating whole blood into its individual components is membrane filtration. Membrane filtration processes typically incorporate either internal or external filter media. U.S. Pat. No. 4,871,462 issued to Baxter (“the '462 patent”) provides one example of a membrane filtration system using an internal filter. The device of the '462 patent includes a filter having a stationary cylindrical container that houses a rotatable, cylindrical filter membrane. The container and the membrane cooperate to define a narrow gap between the side wall of the container and the filter membrane. Whole blood is introduced into this narrow gap during apheresis. Rotation of the inner filter membrane at sufficient speed generates so-called Taylor vortices in the fluid. The presence of Taylor vortices basically causes shear forces that drive plasma through the membrane, while sweeping red blood cells away.
The prior art membrane filtration devices can often produce a purer blood product, i.e., a blood fraction (e.g., plasma) having fewer residual cells (e.g., white blood cells). However, they typically comprise many intricate components some of which can be relatively costly, making them complicated to manufacture and expensive to produce. Prior art centrifugation devices, conversely, are typically less expensive to produce because they are often simpler in design and require fewer parts and/or materials. Such devices, however, may not produce blood components having the same purity characteristics as membrane filtration devices.
Centrifugation and membrane filtration can also be combined into a single blood processing system.
FIG. 1
, for example, illustrates a bowl centrifugation system
100
that also includes an external filter medium
142
. The system
100
includes a disposable harness
102
that is loaded onto a blood processing machine
104
. The harness
102
includes a phlebotomy needle
106
for withdrawing blood from a donor's arm
108
, a container of anti-coagulant solution
110
, a temporary red blood cell (RBC) storage bag
112
, a centrifugation bowl
114
, a primary plasma collection bag
116
and a final plasma collection bag
118
. An inlet line
120
couples the phlebotomy needle
106
to an inlet port
122
of the bowl
114
, and an outlet line
124
couples an outlet port
126
of the bowl
114
to the primary plasma collection bag
116
. A filter
142
is disposed in a secondary outlet line
144
that couples the primary and final plasma collection bags
116
,
118
together. The blood processing machine
104
includes a controller
130
, a motor
132
, a centrifuge chuck
134
, and two peristaltic pumps
136
and
138
. The controller
130
is operably coupled to the two pumps
136
and
138
and to the motor
132
which, in turn, drives the chuck
134
.
In operation, the inlet line
120
is fed through the first peristaltic pump
136
and a feed line
140
from the anti-coagulant
110
, which is coupled to the inlet line
120
, is fed through the second peristaltic pump
138
. The centrifugation bowl
114
is also inserted into the chuck
134
. The phlebotomy needle
106
is then inserted into the donor's arm
108
and the controller
130
activates the two peristaltic pumps
136
,
138
, thereby mixing anticoagulant with whole blood from the donor, and transporting anti-coagulated whole blood through inlet line
120
and into the centrifugation bowl
114
. Controller
130
also activates the motor
132
to rotate the bowl
114
via the chuck
134
at high speed. Rotation of the bowl
114
causes the whole blood to separate into discrete layers by density. In particular, the denser red blood cells accumulate at the periphery of the bowl
114
while the less dense plasma forms an annular ring-shaped layer inside of the red blood cells. The plasma is then forced through an effluent port (not shown) of the bowl
114
and is discharged from the bowl's outlet port
126
. From here, the plasma is transported by the outlet line
124
to the primary plasma collection bag
116
.
When all the plasma has been rem
Egozy Yáir
Pages Etienne
Rose Lelie E.
Vernucci Paul J.
Bromberg & Sunstein LLP
Cooley Charles E.
Haemonetics Corporation
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