U.S. patent number 3,593,854 [Application Number 04/882,663] was granted by the patent office on 1971-07-20 for blood treating and filtering apparatus.
Invention is credited to Roy Laver Swank.
United States Patent |
3,593,854 |
Swank |
July 20, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
BLOOD TREATING AND FILTERING APPARATUS
Abstract
Stored human blood is treated preliminary to blood transfusions
by passing it through a mat of glass wool or other fibrous material
which removes from the blood the storage-generated platelet
leukocyte aggregates present therein. It is filtered during open
heart surgery by passing it through the same material for removal
of aggregates and leukocytes and separation of entrained air.
Inventors: |
Swank; Roy Laver (Portland,
OR) |
Family
ID: |
34116959 |
Appl.
No.: |
04/882,663 |
Filed: |
December 5, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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826480 |
May 21, 1969 |
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Current U.S.
Class: |
210/326; 210/445;
210/491; 210/446; 604/252; 210/436 |
Current CPC
Class: |
A61M
5/165 (20130101); B01D 35/153 (20130101); A61M
1/3633 (20130101) |
Current International
Class: |
A61M
5/165 (20060101); B01D 35/153 (20060101); B01D
35/14 (20060101); A61M 1/36 (20060101); B01d
029/08 () |
Field of
Search: |
;210/65,472,445,446,489,490,491,492,499,436,500 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Decesare; J. L.
Parent Case Text
This application is a continuation-in-part of the patent
application of Roy L. Swank, Ser. No. 826,480, filed May 21, 1969
for "Blood Treating Method and Apparatus," now abandoned.
Claims
Having thus described my invention in preferred embodiments, I
claim as new and desire to protect by Letters Patent:
1. Apparatus for treat, preliminary to medical application, human
blood containing platelet-leukocyte aggregates, the apparatus
comprising:
a. a vessel having an inlet port near one end and an outlet port
near the other end,
b. within the vessel between the inlet and outlet ports, a filter
assembly comprising
1. a blood clot filter member,
2. downstream from the blood clot filter member a first meat of
finely subdivided blood-contact material comprising a solid fibrous
material the fibers of which are nondegrading to the blood and
characterized by the ability selectively to adhere the
aggregates,
3. downstream from the first mat a second mat of finely subdivided
blood-contact material comprising a solid fibrous material the
fibers of which are nondegrading to the blood and characterized by
the ability selectively to adhere the aggregates, the second mat
having a density greater than the first mat for selectively
removing aggregates of smaller size,
4. downstream from the second mat fiber filter member for filtering
from the blood fragments of mat fiber filter material,
c. means for introducing stored blood into a inlet port and for
passing it through the filter assembly,
d. and means for withdrawing the treated blood from the outlet
port.
2. The apparatus of claim 1 wherein the vessel has resiliently
deformable sidewalls on the upstream side of the filter assembly
adapted to be compressed and re-expanded for pumping blood through
the apparatus.
3. The apparatus of claim 1 including
a. a first perforate support member between the blood clot filter
member and the first mat, supporting the blood clot filter member
and compressing the first mat, and
b. a second perforate support member between the first and second
mats supporting the first mat and compressing the second mat.
4. The apparatus of claim 3 wherein the blood clot filter member
comprises a dome-shaped screen support at its open end on the first
support member, the latter having a central opening through which
the first mat projects into the spacing defined by the screen.
5. The apparatus of claim 4 including inwardly extending
projections on the first support member engaging the first mat to
prevent free escape of the latter into the space defined by the
screen.
6. The apparatus of claim 1 including valve means adjacent the
outlet port operable to prevent back flow of blood from the outlet
port into the vessel.
7. The apparatus of claim 1 wherein the second mat of fibrous
material has a density of about 0.1 to 0.4 grams per cc.
8. The apparatus of claim 1 wherein the mat fiber has a diameter
not substantially great than about 30 microns, the density of the
second mat is about 0.2 grams per cc. and the density of the first
mat is about 1/4--1/2the density of the second mat.
9. A high volume, continuous blood filter comprising:
a. upstream and downstream end pieces,
b. a tubular body secured between the end pieces to form a
chamber,
c. an inlet port at the center of the upstream end piece,
d. an outlet port below the top of the downstream end piece,
e. the inlet and outlet ports thereby enabling substantially
horizontal blood flow through the chamber,
f. a quantity of blood-filter material between the end pieces,
g. upstream perforated, filter-material-retaining means locating
the filter material in the path of the blood flow,
h. means spacing apart the downstream retaining means and end piece
and forming therebetween a recess at the downstream end of the
chamber for separating and collecting air entrained in the blood,
and
i. air-exhaust port means communicating with the top of the recess
for exhausting collected air therefrom.
10. The blood filter of claim 9 wherein spacing means comprises a
peripheral boss on the downstream end piece projecting inward
therefrom for abutment by the downstream retaining means.
11. The blood filter of claim 9 including means spacing apart the
upstream retaining means and end piece and forming therebetween a
recess at the upstream end of the chamber.
12. The blood filter of claim 11 wherein the spacing means
comprises a peripheral boss on the upstream end piece projecting
inward therefrom for abutment by the upstream retaining means.
13. The blood filter of claim 9 including baffle means opposite the
inlet port for diffusing the blood laterally over the entire area
of the blood filter material.
14. The blood filter of claim 13 wherein the baffle means comprises
an imperforate central portion of the upstream retaining means.
Description
In blood transfusions and heart surgery it has become routine to
employ blood bank blood. This is prepared by withdrawing blood from
donors, adding heparin or other preservative, and then storing the
blood under carefully controlled conditions until its use is
required.
Whether it is used directly in transfusions or in heart surgery,
there sometimes have been observed in the patient an ensuing
cessation of circulation and other reactions not attributable to
mismatching of blood types. Although the cause of this regrettable
result has been unknown, it has been recognized as a function of
blood storage duration. Accordingly, it has been common practice to
discard blood bank blood after it has been stored for a
predetermined time.
Another difficult problem exists when handling blood during heart
surgery, kidney dialysis, etc. In these procedures not only is the
blood altered to produce harmful constituents, but it becomes
contaminated with extraneous material such as epithelium, pieces of
muscle, fat emboli, fragments of suture material and entrained air.
This foreign material must be removed in order successfully to
consummate the surgical procedure.
It is the general object of this invention to provide method and
apparatus for treating blood to be used in transfusions and heart
surgery which will overcome the foregoing problem, reducing the
likelihood of transfusion reactions due to circulatory failure and
related conditions, and enabling the use of blood bank blood even
though it has been stored for long periods of time.
Another object is the provision of a continuous, high capacity,
blood filter which contemporaneously filters and deaerates the
blood.
In the drawings:
FIG. 1 is a longitudinal sectional view of the herein described
blood treating apparatus, as used in transfusing blood;
FIGS. 2 and 3 are plan views of support elements employed in the
apparatus of FIG. 1;
FIGS. 4 and 5 are graphs illustrating the effect of fiber diameter
and filter density on the performance of filters contained in the
apparatus; and
FIGS. 6, 7 and 8 are sectional, exploded and schematic views
illustrating respectively, the construction and application of a
modified form of the apparatus, as used in heart surgery.
It has been discovered that when blood bank blood is stored, its
leukocyte and platelet components are altered, developing
characteristics which are responsible for the transfusion
complications described above. The alteration is evidenced in two
ways. First, some of the platelets become adhesive. Second, some of
the platelets form aggregates with some of the leukocytes. The
aggregates primarily are responsible for the adverse results
occurring when old blood is used in blood transfusions.
In view of the correlation between the altered component content of
the stored blood and the occurrence of transfusion complications
when such blood is applied in medical practice, the importance of
removing these altered components prior to transfusion and during
heart surgery becomes strikingly apparent.
The present invention provides an efficient method and apparatus
for accomplishing the removal of such components.
FIGS. 1--3 illustrate apparatus for use particularly in
transfusions. The apparatus comprises a tube 10 which may be made
of rigid material such as glass, but which preferably is made of a
nonpyrogenic, sterilizable, resilient material such as polyethylene
plastic. Such material makes of the tube a hand pump so that the
flow of blood through the apparatus may be increased by slowly
compressing the tube sidewalls in the manner shown in dotted
outline in FIG. 1.
Since the blood preferably passes through the apparatus by gravity
flow, tube 10 normally is arranged vertically and has at its upper
end an inlet port and at its lower end an outlet port.
To facilitate application of the apparatus in blood transfusions,
the inlet port of the tube preferably is fitted with a hollow,
penetrating spur 12 adapted to pierce the cap 14 of a bottle 16 of
blood bank blood.
Spur 12 preferably extends inwardly within tube 10 and accordingly
acts as a metering device by which drop flow of blood may be
monitored. The open lower end of tube 10 is fitted with a cap 18
having an integral valve chamber 20 and a stub exhaust conduit 22.
A ball valve assembly 24 is seated within the valve chamber better
to control the flow of blood during pumping of tube 10. The ball
valve assembly may be omitted, however, where the head of blood in
container 16 is sufficient to prevent reverse flow.
A rubber tube or other conduit 26 is attached to stub conduit 22.
It conveys the blood to the patient, usually through an interposed
flow valve.
Tube 10 thus provides a housing for filter elements which
selectively remove the undesirable altered components of the stored
blood. To this end there are welded or otherwise secured to the
inner sidewalls of the lower portion of the tube, below the pumping
area, an upper support 28, an intermediate support 30, and a lower
support 32. Upper support 28 is illustrated in detail in FIG. 2
while lower supports 30, 32 which may be substantially identical,
are illustrated in FIG. 3. All three supports may be made from
substantially rigid plastic.
Support 28 mounts a blood clot filter screen 34 of stainless steel
or other suitable material. It has a screen size dimensioned to
screen out any clots which may be present in the blood.
Support 28 also guides the blood to the central area of the tube To
this end it comprises a ring 36 which is glued or otherwise affixed
to the inner walls of tube 10 and an inwardly projecting, annular
flange 38. The latter has inwardly extending projections 40,
particularly evident in FIG. 2.
Supports 30, 32, on the other hand, serve the function of
supporting the filter material. Each comprises a ring 42 mounting a
characteristic pattern of crosspieces 44. Ring 42, like ring 36, is
glued or otherwise fastened to the inner wall of the tube.
The three support rings thus provide three chambers 46, 48, 50 of
progressively smaller volume. These chambers contain the filter
material determining the desired performance of the filter.
Chambers 46, 48 contain the filter material 52 responsible for
removing the blood aggregates and the altered leukocytes and
platelets. For use in this application, the filter material must
adhere these storage-altered components selectively; must permit
free passage of the other blood components; must have a large area
of absorbing surface; must not be nonpyrogenic; must not pack; must
not collapse nor plug; and must not be affected adversely by
repeated subjection to heat and chemical sterilization.
To meet the foregoing requirements, the filter material is used as
filaments or fibers which may be formed into a resilient mat
compressible as required to produce passageways or channels of
optimum size. The diameter or cross-sectional area of the
individual particles of the material is of primary importance in
determining its suitability.
In general, as will be demonstrated hereinafter, the material
should comprise fibers or filaments having lengths of not less than
100 microns and diameters of less than 60 microns, preferably less
than 30 microns. Such fibers are sufficiently large so that they
will not pass through the filter and into the bloodstream of the
patient. They are sufficiently small in diameter so that the
storage-altered aggregates can completely surround them with
overlapping portions which stick to each other, anchoring the
aggregates to the fibers.
Material suitable for the present invention purpose thus are
fibrous or filamentous polyester resins (Dacron and kodel), filter
polyamide resin (Nylon), filamentous polyacrylic resin (Orlon),
glass wool, steel wool, cotton, and cellulose (paper). However, the
fibrous or filamentous materials meeting the above noted
requirements may also be used.
In achieving the purposes of the invention, it further is desirable
that the upstream portion of the filter material should be rather
loosely packed to allow penetration of the large aggregates and
their distribution through the entire filter, thus increasing its
capacity. Downstream, there should be provided a quantity of the
filter material which is relatively closely packed. This provides
the large surface area necessary to selectively absorb the storage
altered components of smaller size.
Chamber 46, and to a certain extent the interior of dome-shaped
clot filter 34, receive the more loosely packed filter material.
The central opening and inwardly directed projections 40 of support
28 allow the filter material to fluff up above the support, without
freely escaping from the chamber below.
Chamber 48 receives the more tightly packed filter material. In
general, it may be packed to advantage from two to four times more
densely than the filter material contained in chamber 46, i.e. to a
density of from 0.1 to 0.4 grams per cubic centimeter.
Chamber 50 receives a sponge filter 54 having for its function
preventing fragments of the filer material contained in the
superimposed chambers from reaching conduit 26, and hence the blood
stream of the patient. The sponge filter preferably has a pore size
of 60 to 100 pores per square inch. It preferably comprises porous
polyurethane or other porous plastic. In the alternative, it may
comprise a stainless steel screen or sponge.
The importance of filter element diameter and degree of compression
in chamber 48 has been determined by tests, the results of which
are shown in FIGS. 4 and 5.
To determine the effect of filter material diameter, the apparatus
of FIG. 1 was filled with filter materials of varying identity and
cross-sectional dimensions. Blood bank blood outdated by several
weeks was gravitated through the apparatus at room temperature.
The treated blood then was tested for the presence of residual
storage-altered components, i.e. adhesive platelets, and leukocytes
and aggregates of the same by passing it through the pressure test
apparatus described in the patent of Roy L. Swank, U.S. Pat. No. A
3,266,299, and measuring the developed filtration pressure. The
results follow in Table 1
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and are graphed in FIG. 4. 67 TABLE I
Material Average Fiber Filtration Diameter (microns) Pressure (mm.
Hg)
__________________________________________________________________________
Nylon 58.+-. 6 180 Nylon 42.+-. 4 96 Nylon 26.+-. 2 27 Nylon
20.+-..+-.2 16 Nylon 14.+-. 1 10 20 Dacron 13.+-. 1 23 Dacron
17.+-. 1 , 25 Dacron 20.+-. 4 , 39 Glass wool 10.+-. 2 24 Steel
wool 28.+-. 4 , 36 Stainless Steel Wool 50.+-. 10 , 120 Cotton
20.+-. 4 , , 33 Verel 20.+-. 5 , 25 Kodel 20.+-. 5 , 25 Cellulose
30 and smaller , 40 (defiberized paper)
__________________________________________________________________________
It will be observed from the table and graph that the efficiency of
the treatment is affected markedly by the diameter of the packing
fibers. To be effective, the fibers should have diameters of less
than 60 microns, preferably less than 30 microns. As the diameter
decreases, the efficiency of the altered blood component removal
increases dramatically.
To test the effect of filter material compression in chamber 48,
samples of clot-free blood were allowed to flow gravitationally
through the filter packed with packings of varying density. In each
case the same amount of blood was employed and the time noted for
passage through the filter. The results are given in FIG. 5.
It will be noted that a marked point of inflection occurs at a
density of about 0.2 grams per cc. In general, best results are
obtained where the density of the filtering material lies within
the range of from 0.1 to 0.4 grams per cc. At lower densities,
efficient filtration is not obtained. At higher densities, the
filtration rate is too slow to be practical.
In the use of the filter stored blood contained in the container 16
passes through hollow spur 12 which meters it dropwise into
resiliently collapsible tube 10. There it passes first through clot
filter 34, which screens out the clots, and onto flange 38 of
support 28, which directs it centrally of the tube.
Within clot filter 34, and to a greater extent within camber 46
through which it next flows, the blood contacts loosely packed
filter material 52 contained in camber 46. This removes the larger
aggregates.
Next, it flows through more tightly packed filter material 52
contained in chamber 48 which selectively removes the
storage-altered leukocytes and aggregates of smaller size.
Next it passes through sponge or screen filter 54 which prevents
particles of the filter material from leaving the apparatus and
entering the bloodstream of the patient.
While this is occurring, the upper resiliently deformable portion
of the tube 10 may be slowly compressed and allowed to re-expand.
This pumps the blood through the filter and makes possible rapid
transfusion in emergency situations.
FIGS. 6, 7 and 8 illustrate apparatus useful for filtering blood
during open heart surgery, kidney dialysis procedures, etc. The
general arrangement of the various units employed in the system is
illustrated particularly in FIG. 8.
A conduit 110 may be tied to the superior or inferior vena cava 112
using known techniques. A branch conduit 114 having a suction tip
115 made of stainless steel or other inert material is placed in
the chest cavity for removal of accumulated blood.
Conduit 110 and 114 merge to form main conduit 116 which transfers
the blood to a reservoir 118 of suitable capacity.
The blood then passes through a first pump 120, an oxygenator 122
and a second pump 124. The latter discharges it into the herein
described blood treating and filtering apparatus 126. It should be
noted, however, that this apparatus may be located variously in the
system to meet the needs of various situations. Typical alternate
locations are illustrated in dotted outline.
The oxygenated, treated, and filtered blood then continues through
conduit 116, the discharge end of which is tied into the femoral or
other artery 128.
The construction and manner of assembly of blood treating and
filtering unit 126 is shown in detail in FIGS. 6 and 7.
The unit comprises an upstream end piece 130, a downstream end
piece 132 and a tubular body 134. End pieces 130, 132 may be made
from stainless steel or plastic, while body 134 may be made from
transparent plastic or glass.
The upstream end piece 130 is provided with a central inlet port
136 with outwardly projecting nipple 138 for attachment of one
segment of conduit 116. The downstream end piece 132 is provided
with a discharge port 140 communicating with a nipple 142 designed
to receive another length of conduit 116.
These three elements of the unit, i.e. upstream and downstream end
pieces 130, 132, and body 134 provide a central chamber 144
arranged for horizontal flow of the blood. The chamber is sealed by
providing in the inner face of the end piece 130 an annular groove
146 seen clearly in FIG. 7. A similar groove, not visible in the
same figure, is present in end piece 132. Seal rings 148, 150 are
seated in the grooves.
The entire assembly then is clamped together with the parts in
sealed relationship by suitable means such as bolts 152 penetrating
one of the end pieces and threaded into the other.
Housed within chamber 144 in laterally spaced relation to the two
end pieces is a blood treating and filtering assembly comprising a
mat 154 of filter material, a perforated, upstream filter-material
retainer 156, a screen 158, and a downstream filter-material
retainer 160.
Retainers 156, 160 serve to locate filter element 154 centrally in
the path of flow of the blood. They may be fabricated from suitable
durable inert material such as stainless steel or plastic.
Screen 158 serves to screen out pieces of filter material 154 which
otherwise might be entrained in the blood. It may be made of fine
mesh stainless steel, Nylon or other suitable material.
Baffle means prevent channeling of the blood through the central
part of filter 154 and insure that the blood diffuses through the
entire filter area, thus insuring efficient filtration. In the
illustrated form of the invention, the baffle means comprises a
central, unperforated section 156a of perforated retainer 156. This
is located directly opposite inlet port 136.
Further to improve the efficiency of the filter, and to enable it
to remove entrained air, the subassembly including elements 154,
156, 158 and 160 are maintained spaced apart from end pieces 130,
132. This provides an infeed recess 144a and an outfeed recess
144b.
Although various structural arrangements may be provided for
accomplishing this purpose, a preferred arrangement comprises
forming infeed end plate 130 with a peripheral boss 162 and outfeed
end plate 132 with a similar peripheral boss 164. These serve as
spacers by providing shoulders against which the margins of
retaining plates 156, 160 bear in the final assembly of the
apparatus.
Recess 144a, cooperating with baffle area 156a of retaining plate
156, serves the valuable function of causing distribution of the
blood over the entire filter area.
Recess 144b at the downstream end of the unit serves the valuable
function of providing an air trap which permits removal of
entrained air from the blood. Such air, when it reaches the
downstream end of the unit, will bubble upwardly to the top of
recess 144b. There it passes through a port 166 located at the to
of end piece 132. A nipple 168 is received in the port and mounts a
valve 170 which may be used to exhaust the air as desirable or
necessary.
Thus in the application of the form of the invention illustrated in
FIGS. 6, 7 and 8, blood entering through inlet port 136 spreads out
over the area of the filter in recess 144a, and passes through
filter 154, into recess 144b where the entrained air bubbles
upwardly and escapes via port 166.
The filter element removes the altered leukocytes and platelets,
the leukocyte-platelet aggregates, the fat emboli, the epithelium,
the pieces of muscle and suture material, and other debris from the
blood. This all is accomplished efficiently, continuously and at a
high rate sufficient to accommodate the needs of open heart surgery
techniques.
* * * * *