U.S. patent number RE32,089 [Application Number 06/235,093] was granted by the patent office on 1986-03-04 for blood fractionating process and apparatus for carrying out same.
This patent grant is currently assigned to Amicon Corporation. Invention is credited to Edward A. Agranat, William F. Blatt, Peter N. Rigopulos.
United States Patent |
RE32,089 |
Blatt , et al. |
March 4, 1986 |
Blood fractionating process and apparatus for carrying out same
Abstract
A process for separating blood plasma from whole blood that
dispenses with the known centrifugal-separation techniques and
involves passing whole blood along a flow path which is shallow and
substantially parallel to the upstream side of filtration membrane,
recovering plasma from the downstream side of said membrane, and
recovering the retained blood components (formed elements) from the
upstream side of the membrane. .Iadd .
Inventors: |
Blatt; William F. (Framingham,
MA), Agranat; Edward A. (Weston, MA), Rigopulos; Peter
N. (Melrose, MA) |
Assignee: |
Amicon Corporation (Lexington,
MA)
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Family
ID: |
26747032 |
Appl.
No.: |
06/235,093 |
Filed: |
February 17, 1981 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
066675 |
Aug 25, 1970 |
03705100 |
Dec 5, 1972 |
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Current U.S.
Class: |
210/651;
210/321.85; 210/456 |
Current CPC
Class: |
A61M
1/3496 (20130101); A61M 1/3603 (20140204); B01D
61/18 (20130101); B01D 63/087 (20130101); B01D
61/145 (20130101); A61M 2206/12 (20130101) |
Current International
Class: |
A61M
1/34 (20060101); B01D 61/18 (20060101); B01D
63/08 (20060101); B01D 61/14 (20060101); A61M
1/36 (20060101); B01D 013/00 () |
Field of
Search: |
;128/214R,224
;210/DIG.927,433M,651,456,321.1,433.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Bixler et al., "The Development of a Diafiltration System for Blood
Purification", from Trans. Amer. Soc. Artif. Int. Organs, vol. XIV,
Jun. 14, 1968, 99-108..
|
Primary Examiner: Spear; Frank
Parent Case Text
This application is a continuation of Ser. No. 940,969, filed Sept.
11, 1978, now abandoned, and a reissue of Ser. No. 05/066,675,
filed Aug. 25, 1970, now U.S. Pat. No. 3,750,100..Iaddend.
This application is a continuation-in-part of U.S. Ser. No.
828,935, filed May 29, 1969, now abandoned, and of Ser. No.
833,090, filed June 13, 1969, now abandoned.
Claims
We claim: .[.1. Apparatus constructed and arranged to carry out a
separation of whole blood into a plasma fraction and a cellular
fraction, said apparatus comprising
(1) a reservoir for holding whole blood which is to be
fractionated,
(2) a filtration membrane having a pore size from about 0.1 to 0.8
micron diameter,
(3) a flow directing means adjacent one side of said membrane for
conducting whole blood from said reservoir across the face of said
membrane in a zone having a maximum depth of 20 mils measured
vertically from the face of said membrane, and
(4) pressure-generating means constructed and arranged to drive
said whole blood to be fractionated through said flow path only
within the range of a pressure differential from 1 to 15 p.s.i. and
at a flow velocity across the face of the membrane from 2 to 50
feet per minute..]. .[.2. Apparatus as defined in claim 1 wherein
said reservoir is formed of the barrel of a hypodermic syringe,
wherein said pressure-generating means comprises the piston of a
hypodermic syringe, and wherein said syringe is detachably
connected to said membrane and flow directing means..]. .[.3.
Apparatus as defined in claim 1 wherein said filtration membrane
has a pore size from about 0.4 to about 0.7 micron in diameter..].
.[.4. Apparatus as defined in claim 2 comprising additionally a
spring for automatically operating
the piston of said hypodermic syringe..]. 5. A process for
separating blood plasma from the other components of blood
.Iadd.without substantial hemolysis .Iaddend.comprising the steps
of
(1) conducting whole blood in a flow path which is substantially
parallel to the upstream side of a filtration membrane and has a
maximum depth of 20 mils measured vertically from the face of the
membrane, said membrane having a pore size from about 0.1 to about
0.8 micron in diameter,
(2) applying sufficient pressure to said whole blood to cause
.Iadd.a .Iaddend.pressure differential from 1 to 15 p.s.i. between
upstream and downstream sides of said membrane and to provide a
flow velocity across the face of the membrane from 2 to 50 feet per
minute,
(3) recovering plasma ultrafiltrate from the downstream side of
said membrane, and
(4) recovering the retained blood components from the upstream side
of the membrane.Iadd.,
said plasma ultrafiltrate being substantially free of evidence
of
hemolysis.Iaddend.. 6. A process as defined in claim 5 wherein said
filtration membrane has a pore size from about 0.4 to about 0.7
micron in
diameter. 7. A process as defined in claim 6 wherein the
pressure
differential is from 2 to 5 p.s.i. 8. In a process for removing
whole blood from a blood donor and returning the blood constituents
to the donor while keeping the plasma for medical use, the
improvement consisting of
(1) transferring said whole blood from said donor into contact with
the upstream side of filtration membrane having a pore size from
about 0.1 to about 0.8 micron in diameter,
(2) conducting said whole blood across the surface of the membrane
in a path which is substantially parallel to the upstream side of
said membrane and has a maximum depth of 20 mils measured
vertically from the face of the membrane,
(3) applying sufficient pressure to said whole blood to provide a
pressure differential of 1 to 15 p.s.i. between upstream and
downstream sides of said membrane and to provide a flow velocity
across the face of the membrane from 2 to 50 feet per minute,
and
(4) recovering the retained blood components from the upstream side
of the membrane and transferring them back to the blood
donor.Iadd.,
said plasma being removed from the downstream side of said membrane
and being substantially free of evidence of hemolysis.Iaddend..
Description
When obtaining blood from a blood donor, it is very often desirable
to be able to return the cellular components to the donor so that
more frequent bleedings can be made. When only the plasma component
of the blood is desired for emergency use, the formed elements of
the blood (which include the red blood cells, white blood cells and
platelets) can be discarded or used for other purposes or can
profitably be returned to the donor. Such a return is particularly
important because (1) it allows the donor to recuperate to a state
where he can donate again within two weeks rather than in about 2
months as is the case when the non-plasma component of the blood is
not returned to him, and (2) it avoids the temporary weakness
suffered by some donors after they donate a pint of blood. The
importance of a donor's being able to contribute blood at
relatively frequent intervals is obvious in circumstances such as
those wherein injuries are incurred during military operations or
wherein a donor bears a rare blood-type for which an emergency need
exists.
However, blood fractionating of the type described is not used as
frequently as desirable because no really convenient means for
carrying out the process has been available. In general, this type
of blood-fractionating has been done by
(1) transferring the blood from a donor into a blood bag by means
known to most blood donors, then
(2) transferring the blood bag into a centrifugal separating
apparatus, then
(3) "spinning" the blood at a rate which optimizes the separation
of plasma from other blood components, but substantially avoids
damage to blood cells, then
(4) separation of plasma by bag compression or withdrawal to a
receiving vessel, and finally
(5) returning the formed elements back into the patient by the
usual transfusion techniques.
Not only does this process involve relatively expensive apparatus,
but it also comprises a sufficiently large number of handling steps
to significantly increase the chance of contamination and/or
cellular damage in the relatively crude environments of the type
that may be encountered at accident scenes, in military operations,
etc.
Moreover, there are many situations in which it is desirable to
separate blood components without returning any of them to the
donor in order to use diagnostic tests without interference from
either the formed cell or plasma components thereof.
The present invention provides a process and apparatus for simple
fractionation of whole blood into a plasma component and a cellular
component while subjecting the components to only very slight
stress. The present invention is furthermore readily applicable to
blood-donation procedures, making it possible to return the
non-plasma component or fraction to the donor virtually
simultaneously with the donation.
The process of the present invention comprises conducting the whole
blood in a flow path parallel to one face of a porous filter
membrane having effective pore diameters from 0.1 to 0.8 micron,
the path having a maximum depth of 20 mils measured vertically from
the face of the membrane, collecting from the opposite face of the
membrane the plasma component, and collecting from the end of said
flow path the cellular component while maintaining the pressure
differential between opposite faces of the membrane from 1 to 15
p.s.i. For best results the rate of flow of the whole blood across
the face of the membrane is maintained from 2 to 50 ft. per minute
and the pore diameter is from 0.4 to 0.7 micron. The precise
diameter of the pores within the stated ranges of size which gives
best results depends upon the precise pressure differential
employed, higher pressure differentials within the stated range
requiring smaller pore diameters. The pressure differential is
critical because it provides the driving force for controlling the
velocity of the blood across, and plasma through the membrane, and
also affects the degree of hemolysis which occurs during
filtration.
It is essential that the blood being filtered travel in a path
substantially parallel to and within 20 mils of the membrane
surface. Attempts to utilize the same membranes under conditions
whereby the whole blood is forced through the membrane by
conventional filtration techniques (i.e., putting the blood in a
reservoir over filtration membrane and applying a pressure
difference across the membrane to push or pull the plasma fraction
through the membrane) results in almost immediate "plugging" of the
membrane.
The term "filtration membrane" is used in this application to means
that class of filters normally supplied in thin sheet form and
capable of effecting separation of very small particulate or
molecular components from suspensions or solutions. Both
anisotropic and depth-filter membranes are included within this
description. The former type of membrane is preferred when
conveniently availble, but a particularly surprising feature of the
invention is that homogeneous depth filters may be utilized in the
blood separation process.
The filtration process of the invention is carried out at
relatively low pressure differentials, e.g., from 1 to 15 p.s.i, as
measured both from one side of the filter membrane to the other and
as measured from the inlet of the whole blood passage to the outlet
for the blood fraction which fails to pass through the filter
membrane. As a matter of convenience, both the receptable for the
filtrate (plasma) and for the rejected blood (non-plasma fraction)
are preferably maintained at atmospheric pressure. Pressure
differentials near the lower end of this range, i.e., from 1.5 to 5
p.s.i. are most advantageous, in part because they can be utilized
in equipment which is less rigorously designed to avoid undue
stress on the cells contained in the blood being fractionated.
Likewise the velocity across the face of the membrane is relatively
low, i.e., in the range of from 2 to 50 feet per minute. Under
these conditions, the flow is substantially laminar. In the more
preferable embodiments of the invention the blood, after passing
over the surface of the membrane, is recycled back to the whole
blood reservoir. The velocity of the stream being dissipated in the
contents of the reservoir aids in keeping the blood mixed well.
In order to point out more fully the nature of the present
invention, the following specific example is given as an
illustrative embodiment of the present process and products
produced thereby.
FIG. 1 shows a view in elevation, partly in section, of a thin
channel ultrafiltration cell useful for carrying out the process of
the invention.
FIG. 2 is a perspective view from the bottom of the reservoir and
flow-directing means showing the apparatus of FIG. 1.
FIG. 3 is an exploded view in perspective showing a novel apparatus
useful in the process of another embodiment of the invention which
comprises a means to attach a hypodermic needle thereto.
FIG. 4 is a view in elevation showing the apparatus of FIG. 3 in
operation.
Referring to FIGS. 1 and 2, it is seen that an ultrafiltration cell
10 comprises a top cap 12, a bottom cap 14 and a cylinder assembly
16. The cylinder is compressed and sealed between caps 12 and 14 by
means of toggle clamping assembly 18, top O-ring seal 20, and
bottom O-ring seal 22.
Top cap 12 comprises a pressure relief valve 24 and a means to
drive fluid across the membrane comprising a port 25 adapted for
connection to a pressurized gas source for pressurizing liquid in
reservoir 28.
Resting on bottom cap 14 is a macroporous support plate 30 formed
of sintered polypropylene. Over plate 30 is a cellulosic ester
filtration membrane 32 having a mean pore size of 0.45.+-.0.02
micron and available from Millipore Corporation under the trade
designation HAW PO 9025. Lower O-ring seal 22 is compressed against
the outer periphery of membrane 32, thereby providing an efficient
edge sealing means.
Cylinder assembly 16 comprises reservoir 28 and an aperture 34
leading from reservoir 28 into a spiral flow path 36 which is
formed by spiral grooves 38 on the bottom surface 39 of assembly
16. This flow path 36 is 0.125 inch wide and 0.010 inch (10 mils)
high. It follows a spiral path in a plane parallel to the membrane
surface, terminating at a fluid outlet port 40 through which the
retained liquid may, via conduit 41, be collected or recycled for
another concentrating step. Filtrate, i.e., that fraction of
material which comes through the filter is carried out of the cell
through conduit 42 which is machined into bottom cap 14.
A sample of whole blood (treated with ACD) was inserted into
reservoir 28 and, under a 2 p.s.i.g. driving force, was divided
into a plasma fraction and a cellular fraction. The whole blood was
forced through aperture 34 in cylinder assembly 16, and thereupon
is caused to follow spiral flow path 36 over the surface of
membrane 32. The blood plasma fraction passed through the
filtration membrane, and was collected through conduit 41 at
atmospheric pressure. About 60% of the plasma content of the blood
was recovered and there was no evidence of hemolysis in the plasma
so collected.
Although the optimum operation of the illustrated device was
realized with an operating pressure of from 2 to 4 p.s.i.g., it is
stressed that higher operating pressures may be used when
particular care is taken to smooth blood-contacting surfaces in
such a way as to avoid excessive mechanical shear on the formed
elements of the blood. For example, a stream-lined or
smooth-surfaced wall 49 with gently rounded corners of aperture 34
is advantageous in this respect. In general, however, a
low-pressure process is most desirable for use in emergency
blood-donation procedures.
Another embodiment of the apparatus is disclosed in FIG. 3. In this
apparatus, which is most useful in analytical work, a hypodermic
syringe 50 has been utilized to withdraw a blood sample from a
patient. The needle (not shown) of the syringe is then removed and
the syringe is attached, by means of a fastening means 52, such as
Luer lock 54, to filtration cell 56. Filtration cell 56 comprises a
top retaining plate 58, filtration membrane 60, a sintered porous
polyethylene support disk 62, and a bottom retaining plate 64.
Retaining plate 58 comprises a spiral ridge forming a shallow flow
path 66 having a depth of 6 mils, a width of 0.5 cm. and a length
of 70 cm. between inlet port 68 and outlet port 70. Retaining plate
64 comprises a filtration outlet port 71.
In order to achieve the most reproducible filtration results, it
has been found more desirable to provide the above-described
apparatus with a positive pressure control means rather than to
rely upon the manual pressure exerted by a number of different
operators. Therefore, a spring means 72 is mounted, at one end 74
thereof, on projecting outlet port 70. The other end 76 of the
spring is adapted to press on plunger 78 of the hypodermic syringe
50. When spring means 72 is so mounted as to rest on plunger 78, a
controlled amount of pressure, about 2.5 p.s.i., is generated for
filtering the blood. Another advantage is that one operator can
utilize a number of these devices at a single time since they do
not require close attention during the filtration operation.
FIG. 4 shows a schematic diagram showing the analytical device of
FIG. 3 in operation. A plasma fraction of the blood is being
collected in vessel 82 while the other blood components are being
collected in vessel 80.
Using the cellulosic ester membrane described above, less than 0.1%
hemolysis was observed, and the plasma obtained was not detectably
different from that obtained by conventional centrifugation. From a
10 ml. sample of fresh blood of normal hematocrit, there was
obtained, in a filtering time of 15 to 20 minutes, approximately
3.0 to 3.4 ml. of plasma. Similar results were obtained using under
the same conditions a polycarbonate membrane 1-10 mils thick)
having a pore size of 0.5.+-.0.06 microns available under the
trademark Nuclepore from the General Electric Company.
Various other advantages and modifications will be apparent to
those skilled in the art and fall within the scope of the appended
claims.
* * * * *