Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
V
1 This inven-tion relates to blood oxygenators of the
membrane type wherein a semi-permeable membrane separates the
blood from the oxygen, oxygen passes through the membrane into
the blood and carbon dioxide passes from the blood through the
membrane into the stream of oxygen. When an aqueous solution
of hydrogen peroxide is used instead of oxygen gas the hydrogen
peroxide diffuses into the membrane, is broken down into oxygen
and water by a catalyst and the oxygen passes into the blood.
By "semi-permeable membrane" is mean, in the case where oxygen
gas is employed, a membrane which is permeable to gas but
impermeable to water. Where a solution of hydrogen peroxide is
used, the semi-permeable membrane is permeable to gas and water
and to small solute molecules and ions but not to the larger
component of blood such as red and white corpuscles, platelets,
etc.
Blood oxygenators used during open heart surgery to
take over the function of the natural lungs are of several types,
including the bubble typ~ in which oxygen is bubbled through
the blood in direct contact therewith, and the membrane type
identified in the preceding paragraph.
Bubble type oxygenators are ~impler and for that
reason are widely used, but the trend is toward the membrane
type of oxygenator. The latter functions more nearly like the
- natural lung in that it separates the stream of oxygen from the
blood and allows communication between the oxygen and the blood
only by diffusion through a semi-permeable membrane. There is
evidence that this more nearly natural functioning o~ membrane
oxygenators is less harmful to the blood than the functioning
of bubble type oxygenators, especially during the course of
lengthy (for example, five hours and more~ open heart surgery.
9~
1 ~owever, membrane oxy~enators heretofore h~ve been
much more complex than bubble oxygenators, so that as a practical
matter they must be taken apart, cleaned, sterilized and
reassembled with new membranes after each use. This is an
expensive, time~consumin~ and cumbersome operation. One such
oxy~enator is that described in my U.S. Patent No. 3,413,095,
which has been very successful in use but suffers from the non-
`disposable characteristic described above.
In Bramson and Tyson U.S. Patent No. 3,834,544 there
is described a membrane type blood oxygenator which is intended
to be of the disposable type, that is to say, suf*iciently
inexpensive to manufacture so that it can be used once and
discarded. However, to date that oxygenator has not been
proved to be practicable in use, one of its defects being that
it offers the possibility of inadvertent leakage of water from
the water circuit into the blood circuit. Water leaking into
the blood causes hemolysis and dilution and is harmful to the
patient. Added to this drawback is the fact that inadvertent
leakage of water rom the water circuit into the blood circuit
of a membrane oxygenator is not likely to become evident at
once. This presents the possibility of long continued, harmful
leakage of water into the blood circuit ~efore the leakage is
ascertained.
A further disadvantage of the membrane oxygenator of
U.S. Patent No. 3,834,544 is the fact that to make and keep all
fluid compartments leak-proof, it is necessary to employ
cumbersome clamps to overcome structural problems which are
described hereinbelow.
It is an object of the present invention to provide
improved, disposable membrane-type blood oxygenators.
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1 It is a Eurther o~jec-t of the invention to provide
disposable membrane-type blood oxygenators of simpli~ied
construction, such that it is economically feasihle to employ
the oxygenator once and once only and then discard it, such
oxygenator being free of defects such as the possibility of
leakage of water from the water circuit into the blood circuit,
and/or such that control over critical dimensions such as the
thickness mentioned above is readily accomplished without
inconvenience.
It is a further and particular object of the present
invention to provide a blood unit including a blood compartment,
such unit having inlet and outlet passages for the blood, the
blood unit being so isolated from water units used with it that
leakage of water into the blood units is precluded.
Yet another object is to provide a simplified
construction in which blood, water and oxygen units are clamped
in a stacked arrangement within a box-like housing with a blood
plenum on each side which provides a pool of blood on the outlet
and inlet sides of the blood units, and oxygen plenums at each
end of the stack, the oxygen units being open ended and in
communication with these plenums; this stack being bolted to the
housing to ensure that the blood paths are of uniform depth.
The above and other objects of the invention will be
apparent from the ensuing description and the appended claims.
Certain embodiments of the invention are illustrated
by way of example in the accompanying drawings, in which:
Figure 1 is a perspective view of the apparatus of the
invention shown diagrammatically in its entirety and connected
to sources of water and oxygen and to the circulatory system of
a patient undergoing open heart surgery;
~27~
1 Figure ~ is a largely diagrammatic, exploded perspec- !
tive view showing the end plates in simplified form and showing
a single blood unit, two oxygen units and two water units. In
this figure for the sa]ce o~ simplicity certain components of
adjacent water and oxygen units are shown as separate components
whereas in actual practice (and as will be apparent from the
description below) such components are common to both a water
unit and an oxy~en unit. Further, whereas in practice a number
of blood units and an appropriately larger number o~ oxygen
and water units will be employed, for simplicity only one blood
unit, two oxygen units and two water units are shown.
Figure 3 is a plan view broken away to reveal portions
of a blood unit, a water unit and an oxygen unit;
Figure 4 is a section ta~en along the line 4-4 of
Figure 3;
Figure 5 is a fragmentary perspective view of a blood
unit;
Figure 6 is a section taken along the line 6-6 of
Figure 3. In this figure the end plates (which are shown for
simplicity as simple blocks in Figures 1 and 2) are shown in
reinforced form;
Figure 7 is a fragmentary sectional view of one of the
end plates showing a chamfer along an edge which serves a useful
purpose as described hereinbelow;
Figure 8 is a ~ragmentary, exploded perspective view
showing a water unit and an oxygen unit. In this figure a single
component common to the water unit and the oxygen unit is shown,
for clarit~, as two separate components;
Figure 9 is a perspective view showing an alternative
and preferred form of end insert for the water units, such heing
also used for the oxygen units;
~ ~.Z7~
1 Figure 10 is a fragmentary longitudinal section through
a blood unit;
Figure 11 is a fragmentary longitudinal section through
an oxygen unit;
Figure 12 is a fragmentary longitudinal view through
a water unit;
Figure 13 is a fragmentary transverse sectional view
through a blood unit;
Figure 14 is a plan view of an alternative form of
~ater unit;
Figure lS is a plan viewof an alternative form of
oxygen unit;
Figure 16 is a plan view of the screen for the oxygen
unit of Figure 15;
Figure 17 is a.perspective view of the oxygen unit
of Figure 15;
Figure 18 is a section along the line 18-18 of Figure 17;
Figure 19 is a section along the line 19-19 of Figure 15;
. Figure 20 is a section along the line 20-20 of Figure 14;
Figure 21 is a view similar to Figure 7 but on a
larger scale and showing more clearly the forces acting on the
end plates and the stack of blood, oxygen and water units held
together by the end plates; and
Figure 22 is a view similar to Figure 7 showing an
alternative way of ~orming a chamfer.
Figures 1 to 22 described above are directed to one
embodiment of the invention. Figures 23 to 32 described below
are directed to another embodiment of the invention.
Figure 23 is a top plan view of the device showing the
cover for the same;
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o
1 Figure 24 is a view in side elevation showing o~e side
wall and showing edge views of the top and bottom covers and of
the end walls;
Figure 25 is an exploded view showing a blood unit with
the upper membrane separated ~rom the blood screen and showing
other components of the blood unit and showing also a water unit
sandwiched between two oxygen units;
Figure 26 is a fragmentary horizontal section taken
through the device looking down upon one of the blood units;
Figure 27 is a section taken along the line 27-27 of
Figure 26 showing several water, oxygen and blood units in
assembled condition and showing the means whereby water is
introduced into the water units;
Figure 28 is a section taken along the line 28~28 of
Figure 26 showing the means whereby blood is introduced into the
blood units;
Figure 29 is a section taken along the line 29-29 of
Figure 26 showing the means whereby oxygen is introduced into
thè oxygen units;
~0 Figure 30 is a fragmentary plan view of an alternative
water unit;
Figure 31 is a section taken along the line 31-31 of
Figure 30; and
- Figure 32 is a section taken along the line 32-32 of
Figure 30.
Referring now to the drawings, and first to Figure 1,
the device or apparatus of the present invention is generally
designated by the reference numeral 10 and it is shown as
comprising end plates lla and llb between which is an assem~ly
or stack of water, oxygen and blood units collectively designated
1 by the reference numeral 12, the whole assembl~ being held
together by bolts 13 which pass through the end plates lla and
llb and through the assembly 12.
The device or apparatus 10, i.e., the apparatus of the
present invention, is shown connected to certain external
equipment which may be of well known design. For example, water
and oxygen circulating and/or supply means are shown at 14 and
15, respectively, and they are shown only diagrammatically. The
water supply 14 will include a pump and thermostatic means to
effect circulation of the water and to maintain proper water
and blood temperature and it may include a source of nitrogen
under pressure to pressurize the water circuit. The oxygen
supply 15 will comprise a source of oxygen under pressure and
suitable valving means, pressure gauge and flow gauge. Blood
inlet line 16a and outlet line 16b will be connected to the
venous line and the arterial line from and to the patient,
respectively, by suitable means which are well known in the
art, and which include a pump-in the venous line. Bramson
U.S. Patent No. 3,413,095 describes suitable equipment of this
type.
Referring now to Figure 2, the end plate lla is formed
on its inner surface with a long horizontal blood flow slot or
manifold 17 connected at one end to a blood inlet 18. End plate
lla is also formed with short vertical slots 25 and 26 for water
ànd oxygen outlets, respectively. End plate llb is similarly
formed but is inverted. In Figures 1 and 2, end plates lla and
llb are `shown, for simplicity, as simple blocks but, preferably,
they are constructed in another manner, for example as shown in
Figures 6 and 7, and as described hereinbelow. Between the end
plat~s lla and 11~ a simplified assembly or stack 12a is shown
consisting of (reading from left to right) a water unit 26, an
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.
1 o~ygen unit 27, a single blood unit 28, another oxygen unit 27
and another water unit 26. This simplified drawing serves the
purpose of illustrating the flow of fluids ~blood, water and
oxygen) through the apparatus. In actual practice, the assembly
12 will usually consist of a number of blood units sufficient to
provide a total membrane surface adequate for oxygenatin~ the
patient's blood. In practice, a typical adult size preferred
assembly 12 would have the following stacking order, using the
symbols ~ to indicate a water unit, O to indicate an oxygen unit
and B to indicate a blood unit:
W - O - B - O - B - O - W - o - B - O - B - O
W - O - B - O - B - O - W ~ O - B - O - B - O
W - O - B - O B - O - W - O - B - O - B - O - W
The assembly illustrated above has the advantage of
using fewer water units W (one for each two blood units) and it
therefore results in a more compact assembly of uni-ts, ye* is
sufficient to hold the thickness of the blood units (hence the
depth of the blood path in the blood units) constant and equal
to the thickness of the blood screens described below. However,
for purposè of more adequate temperature control of the blood,
a greater number of water units may be employed, for example,
one water unit W for each blood unit B, thus W - O - B - O -
W - O - B - O - W -. That is, the module is - W - O - B - o -.
- Referring now to Figure 5, a blood unit 28 is there
shown. It comprises a rectangular blood frame 30 including side
members 31 and recessed end members 32 forming, with the side
members, a recessed area 32a. This frame 30 is overlaid by a
pair of membranes 33 which are permeable to gas (ox~gen and
carbon dioxide) but impermeable to liquid (blood and water).
Within the cell or blood space 33a formed by the membranes 33 is
1 a screen 34. ~ypical and preferred materials and charac~ceristics
of the men~branes 33 and the screen 34 are as follows: For the
membrane, microporous polypropylene or microporous Teflon may
be used. Also, silicon rubber or Teflon material in which the
gaseous dissolve and diffuse. Th~ screen 34 may be woven or
extruded from polypropylene or polyester and may have a mesh of
18 to 22 counts per inch and a thickness (which determines the
depth of blood cavity 33a) of ~.020 inch.
The blood frame 30 is shown in three parts consisting
of top and bottom parts (as viewed in Figure 5) 40 and 41 and
an inner part 42. Each of these parts is formed with
longitudinal blood flow-through slots 43 along the side portions
31 and the inner part 42 is also formed with a series of
transverse slots 44 extending from the respe~tive slots 43 to
the inner edge, and therefore to the blood space 33a. The
flow-through slots 43 are in registr~ with one another to
permit flow of blood through the assembly 12 (Figure 1), as well
as out into the blood space, as will be described hereinafter.
The frame members 40, 41 and 42 may be constructed o~ any
~O suitable material having appropriate structural characteristics
for the purpose and also to be compatible with the fluids flowing
in the system and capable of heat sealing with the membrane. A
suitable material is polypropylene. The membranes 33 are heat
sealed at 46 to the frame along side members 31 and end members
32, thus forming a membrane envelope. As will be seen, end
members (of which onl~ one is shown in Figure 5, there being
another one at the other end~ are imperforate.
A spacer member 47 is received in the recess 32a at
each end of the blood frame and it is formed with a pair of flow
through slots 48 extending therethrough, which are intended for
>J~
1 -the Elo~ of oxygen and water as described hereinaf-ter. As will
be seen, the side parts 31 oE the frame 30 and the insert 47
are provided with bolt holes ~9, those in the side members 31
being outside the blood flow-through slots 43 and those in the
insert or spacer a7 lying outside the oxygen and water flow
through slots 48.
Referring now to Figure 8, a water unit 26 and an
oxygen unit 27 are shown. This assembly or pair of an oxygen
unit and a water unit have a single side frame member 50 on each
long side, which is common to both the water unit 26 and the
oxygen unit 27. However, as explained above, the side member 50.
is shown twice to show its relation to the water and oxygen units.
As will be apparent, the water and oxygen units may, at
particular places in the assembly 12 be W - 0~ or O - W - 0, or
O alone (i.e., not adjacent a water unit). The thickness of the
side member 50 will vary accordingly. That is, the side piece
for a W - O pair will be equal to the thickness of an adjacent
pair of water and oxygen units; the side pieces for an 0 - W - 0
triplet will be equal to the thickness of two oxygen units and
one water unit; and the thickness of a side piece for a single
oxygen unit will be equal to the thickness of an oxygen unit.
The side members 50 are formed with blood flow-through slots 51
which register with slots 43 in the side members of the blood
units.
A water envelope or mattress 52 is provided which is
of water and gas-impermeable material, for example, flexible
polyvinyl chloride, polypropylene, polyethylene or polyvinyl
alcohol. This material is sealed along all edges at 53, that is
to say, two sheets of the material are seamed together as by
heat sealing, vulcanizing or other suitable means. Instead of
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1 being formed from separate shee-ts and heat sealed, the water
mattress may be formed from a seamless tube and heat sealed ak
the ends. In either case before the ends are sealed, the water
mattress is fitted at each end with an insert 54 which, in the
embodiment shown in Figure 8, is in three parts consisting o~
u~per and lower parts 55 ("upper" and "lower" being used with
reference to Figure 8, it being understood that in use the water,
oxygen and blood units will be on edge) and a third or inner
part 56. All of these components are slotted at 57-W (water flow-
through slots) and 57-O (oxygen flow-through slots), the water
and oxygen slots registering with one another and providing water
and oxygen flow-through passages, respectively. The water ma~tress
is similarly slotted. The inner part 56 is also formed with a
series of slots 58 which extend from the water flow-through slot
57-W inwardly to the edge of the insert, thereby communicating
the slot 57-W with the interior of the water mattress. The-
oxygen flow-through slot 57-O in part 56 is free of such transverse
slots.
Each end of the water mattress is fitted with such an
insert, the two inserts being identical to one another but being
inverted in relation on one another such that Elow of water
through the water mattress is diagonal, as indicated in Figure 2.
Diagonal flow is advantageous because it minimized channeling and
enhances uniform water flow through the mattress.
Each end of an oxygen unit 27 is provided with an end
member or insert 65 having projecting ears 66 which abut the side
frame member 50 and which, together with the frame members forms
an oxygen space 67 within which there is a screen 68. Materials
and characteristics suitable for this screen are as follows:
Pol~propylene or polyethylene ma~ be used or any of a
~ 1 2 ~
l number of weavable or extrudable plastic materials may be usea.
Overall thickness of the screen may be from 0.015 to 0.045 inch.
~lesh of the weave may be 10 to 25 counts per inch.
E~cept for the configuration of its perimeter, the
insert 65 is identical with the insert 54 described above with
reference to ~he water unit. Similar paxts are similarly
numbered. The inner member 56 is form~d with transverse slots 58
as in the case of the insert 54, but these slots connect with
the o~ygen flow through slots 57 0 rather than the water flow
through slots 57-W. As in the case of the inserts 54 of the water
unit, the insert 65 at one end of an oxygen unit is inverted in
relation to the insert 65 at the other end, whereby the flow of
oxygen through the oxygen unit is diagonal and uniform flow is
enhanced.
Referxing now to Figure ~, an alternative and preferred
two-piece construction for the insert 54 is shown and it is
generally designated by the reference numeral 70. It will be
understood that although this depicts an insert for a water unit
26, ~he same construction may be employed for the end inserts 65
f an oxygen unit, with due allowance for the ears 66.
As shown in Figure 9, the insert 70 consists of a
bottom (as viewed in Figure 9) piece 71 formed with transverse
grooves 73 communicating with the water slot 57-W and a top or
cover piece 72. As in the case of the inserts g4 and 65, bolt
holes 49 are provided which lie outside of the slots 57-0 and
57-W.
A similar simplified construction may be employed for
the blood frame 30, such being shown in Figure 13 in transverse
section, and in Figure 10 in longitudinal section.
Referring to Figure 13, the blood side frame member is
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1 generally designated b~ -the reference numeral 30a and it
comprises a lower (as shown in Figure 13) thick strip or plate 80
and a thinner cover plate 81. The lower member 80 is formed
with a series of grooves, one such groove being shown at 82 and
serving to provide blood ~low from the blood flow-through slot 43.
That is to sa~, in this construction the side frame members 30a
are formed with grooves molded in the lower portion 80 rather
than having a third, comb-like component such as shown at 42 at
Figure 5. Also shown in Figure 13 are heat seals 83 between
the membranes 33 and the frame members, and also a heat seal 84
between the top frame member 81 and the bottom frame member 80. .
Such heat seals extend around the entire perimeter of the blood
frame 30a.
From the description above, and with particular
reference to Figure 2 (which, as stated, is a simplified axrange-
ment of blood, oxygen and water units, but which will suffice for
the purpose of illustrating the flow of fluids) it will be
apparent that the flow paths of the three fluids (blood, water and
oxyqen) are as follows: Blood fills the groove or manifold 17
in end plate 14a and flows through blood flow-through slots 51
in the adjacent water unit 26 and oxygen unit 27. (As e~plained
above, a single side member 50 bridges a pair of water and
oxygen units, but for simplicity, each unit is shown with a
separate side member 50). At the le~el of the blood unit 28 a
portion of this stream of blood flows through slots 44 (see
Figure 5), or through grooves 8~ if the construction of Figure 13
is used, into the respective blood space 33a, thence across the
blood envelope to slots 44 (or grooves 82) on the opposite sides
and then through the blood flow-through slots 51 to groove 17
in end plate llb and out of the apparatus, to the arterial system
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1 of the patient. It will be understood that in actual practice
where multiple blood units are employed rather than a single
blood unit as in Figure 2, a portion of the blood will ~low into
each blood unit.
The flow of water and oxygen are opposite to the flow
of blood in the sense that they enter thro~gh end plate llb and
leave through end plate lla, whereas blood enters through end
plate lla and leaves through end plate llb, but within the
respective water and oxygen units 26 and 27 the flow is as shown
in Figure 2, a portion of the flow oE each fluid being diverted
at the level of each respective water or oxygen unit for flow
through that unit. It will be seen that the flow of blood and
the flow of water are upwards. Thus at the level of each blood
unit 28 that portion of the stream of blood which is diverted
into such unit flows upwards into the blood space 33a, and at the
level of each water unit 26 that portion of the stream of water
which is diverted into such unit also flows in an upward direction.
This aids in avoiding entrapment of air or other gas which is
esp~cially important in the case of the blood because such
entrapment could cause an embolism.
In start up (after the water and blood units 26 and 28
are tested and the completely assembled apparatus is tested as
described below) the apparatus is primed and in priming care is
taken to remove-all air or other gas from the blood and water
circuits. This is aided by the upward flow patterns noted above
and shown in Figure 2 and it is also aided by tilting the
apparatus (see Figure 1) so that the lower edge of end plate lla
is lower than the lower edge of end plate llb and so that the
right-hand ends ~as viewed in Figure 1) of the end plates are
hi~her than their other ends. Therefore, the blood flow at all
74~
1 times has an upward componen-t. Therefore when the apparatus is
primed and ready for use it is free of entrapped gas, and it
remains free of gas during use. This is, as noted, especially
important in the case of the blood circuit. The apparatus is
held, by suspension or otherwise, in the doubly tilted attitude
(i.e., tilted about one edge and about one end) during use.
As noted above, the end plates lla and llb are shown
in Figures 1 and 2 as rectangular prisms, but their preferred
construction is otherwise. A suitable construction is shown
by way of example in Figures 6 and 7. As will be seen from
Figure 6, each of the end plates comprises a solid plate 90 of
suitable material, for example polycarbonate, acrylic resin or
acrylonitrile-butadiene-styrene resin. This plate is rein~orced
by longitudinal ribs 91 and lateral r:ibs 92. The entire
construction may be molded in one piece. Bolt holes are shown
at 93 to receive the bolts 13. Referring now particularly to
Figure 7, it will be seen that outer edge 94 is chamfered, the
angle of the chamfer ~eing typically about 1.
The chamfer surfaces 94 intersect the major, interior
20 flat surface of the plate along fulcrum lines 94a which are
locatea inwardly not only of the bolt holes 93 but also o~ the
flow-through slots 43 and 48 (see Figure 8) and the blood flow
grooves or manifolds (see Figure 2). Therefore! as the bolts 13
are tightened the chamfered edges 94 (which extend around the
entire periphery o~ the end plates) are pulled toward one
another with the intersection of the chamfers and the flat
central portions of the end plates acting as fulcrums. When the
water mattresses are filled with water under pressure, typicall~
about 12 psi gauge, the water pressure also tends to force the
30 chamfered edges of one plate toward those of the other plate.
These forces in turn act on the edge portions of the stack 12
~Z7~30
1 cf blood, wa-ter and oxy~en units, thereby ensuriny more nearly
uniform pressure intensity between the joint making contact
surfaces in the periphery of the stack. This feature and a
variant are further described below with reference to Figures 21
and 22.
In assembling and testing the components of the
apparatus described hereinabove and illustrated in the drawings,
the following procedure is recommended:
Each blood unit 28 is tested separately and each water
unit 26 is tested separately before assembling. Each blood
unit is tested by clamping it in a testing device comprising
plates similar to the end plates lla and llb, filling it with
distilled water, and observing whether water leaks, either by
observation of pressure change or by observation of drop in a
column of water in a transparent tube extending up from the ou~let.
The water unit may ~e tested similarly but more
conveniently by filling it with air under pressure and observing
a pressure gauge to determine holding or loss of pressure.
Then the blood and water units are assembled including
~0 spacers as shown at 50 and 65 in Figures 8, oxygen screens as
shown in Figure 8, and inserts as shown at 47 in Figure 5,
also end plates lla and llb as shown in Figure 6 and bolts 13
are applied and their nuts are tightened. A room temperature
vulcanizing adhesive is applied to the spaces 100 between the
spacers 50 and the stack of water and oxygen units 26 and 27.
There are four such spaces, one at each corner, two such spaces
being shown at 100 in Figure 3, the cured or vulcani2ed adhesive
being shown at 101. Then the assembly of blood, oxygen and
water circuits is tested as follows:
The water circuit is filled with compressed air and a
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1 pressure gauge is e~ployed to determine whether there is a drop
in pressure. Then the blood circuit is tested by Eillin~ it
with distilled water while maintaining air pressure in the water
circuit. ~ny outward leakage from the blood circuit is visibly
evident. A leak from the interior of the blood circuit, e.g.,
from one of the blood envelopes, is made evident by the presence
of water in the oxygen circuit which remains open and will leak
water through its outlet.
All parts of the oxygenator to be in contact with any of
the circulating fluids (blood, water and oxygen) are sterilized,
for example, by known ethylene oxide sterilization procedures.
In use, the assembled apparatus is connected as shown
in Figure 1 and as described above, to water and oxygen supplies
and to the venous and arterial systems of the patient and to
other necessary equipment.
In the description above and in Figures 3, 5 and 13
the semi-permeable membranes 33 are shown as being heat sealed
at 46 to the side members 31 of blood frame 30. Difficulty may
be encountered at the ]unctions of the heat seals along the side
members 31 and the end members 32, such as wrinkles in the
membrane in the adjacent area. This may be remedied by relying
upon pressure seals along the side members rathér than heat seals,
leaving heat seals only along the end members 32. The chamfers
94 (see Figure 7) and the advantages conferred by them as des-
cribed above allow such pressure seals to be used if such are
deemed advisable.
Dimensions of the apparatus are of importance in the
light of requirements of a patient. Following criteria and
recommendations will be of help in the practice of the inventionO
The blood circulation of the average adult person at
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1 rest is about 5 litres oE blood per minute, and the p~tient will
require about 200 cc of oxygen per minute at atmospheric pressure
and body temperature (98.6F). It has been found that these
requirements are met by apparatus having approximately twelve
blood units each 7-1/2 inches from blood inlet to outlet side,
and 1~ inches in width of blood paths. More precisely, these
dimensions are 7-1/2 inches from the outlet ends of the slots
~4 (or grooves 82 in Figure 13) to the inlet ends of the cor-
responding slots or grooves in the opposite side member, and
18 inches from the inner edge o~ one end of member 32 to the
inner edge of the other end member 32. The thickness of the
blood screen, which determines the thickness of the blood space
33a and hence the thickness of the blood path, is preferably
about 0.020 inch. Typical dimensions of the water and oxygen
units are 23 inches by 7-1/2 inches. The oxygen screen 68 and the
blood screen 34 promote uniform flow of the respective fluids.
Moreover, the blood screen 34 provides a gentl~ turbulent flow
of blood which does not harm the blood yet promotes e~ficient
contact with the oxygen that diffuses through the membranes 33
and efficient trans~er of carbon dioxide from the blood units to
the oxygen units.
There may, of course, be departures from these dimen-
sions. The length of the blood path in each blood unit, that is,
the distance bet~een the inner edges of the side members 31 of
the blood frame, may be increased thereby allowing more oxygen
to be adsorbed by the blood in its transit through a hlood unit,
and also a correspondingly greater diffusion of carbon dioxide
from the blood into the oxygen stream. However, longer blood
paths present more resistance to flow~ so that greater pressures
will be required.
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1 The length of each hlood unit may depart from the 18
inch figure described above; thus more than 12 units may be used,
each having a shorter dimension than 1$ inches, or this dimension
may be increased and fewer units employed. In the latter case,
if the departure is considerable, the size of the components
may introduce manufacturing difficulties, and the device may be
somewhat cumbersome.
It has been found that a flow rate designed to effect
about 95% saturation of the blood with oxygen is satisfactory.
Since oxygen is relatively inexpensive and is vented from the
system, high oxygen flow rates are favoured, such as seven litres
per minute per s~uare meter o~ effective m~mbrane area.
Among advantages of the apparatus described and
illustrated above are the following: The components may be
made of readily available and relatively inexpensive plastic
material by economical methods, such as molding and/or stamping.
The overall dimensions are typically about 23 lnches in length,
10 inches in width, and 4 inches in height (a total volume of
920 cubic inches) which is a convenient size for use in an
operating facility. (Length is the ~ong dimension in Figure 1,
width is the distance between the outer surfaces of the end
plates and height is the distance between the upper and lower
edges of the end plates in Figure 1.)
The apparatus can be manufactured at a cost such that
it is disposable and may be used once and discarded.
The water and blood circuits operate at pressures
higher than the pressure in the oxygen circuit, and the water
and blood circuits are so designed that any leakage from tha
water circuit will be either to the exterior of the apparatus or
into the oxygen space. Therefore, leakage of water into the
blood circuit is precluded.
-- 19 --
~L~2~
1 The chamfer 94 described above with reference to
Figure 7 ensures a tight, even application of pressure.
Reference is now made to Fi~ure 21 which also shows one of two
gaskets 95 of compressible material such as rubber which are
placed only on those long sides where there are no blood manifolds
17 in the end plates lla and llb. To prevent contact of rubber
with blood, these gaskets are covered with a blood-compatible
plastic polyethylene on the side facing the stack. As bolt
pressure is applied the tapered edges of the cover plates bend
about the fulcrum lines 94a where the plane of the chamfer 94 meets
the plane of the flat major interior surfaces of the end plates.
This causes the central portion of the end plates to bend
outwardly. When the apparatus is in operation with water
flowing through the water mattresses at, ~or example, 12 psi
gauge pressure, the water pressure combined with the tension in
the bolts causes additional outward bending of the central portion
of the end plates. It will be understood that such a bending
is very small in magnitude but is sufficient to reduce the
pressure intensity along the inside seal line. If the elasticity
o the compressed stack is low, leakage of blood` into the oxygen
space may result. This elasticity is ensured by the presence of
the gasket 95 to prevent leaks. The directions of the forces
involved are shown in Figure 21 by the arrows.
Referring now to Figure 22, which is similar to
Figure 7, the use of a tapered wedge 96 is shown which provides
the chamfer 94. An advantage of this construction is that
tapered wedges may be less expensive to manufacture than
chamfered end plates. Another advantage is that i dlfferent
chamfers are required for different materials of construction
of the stack 12 and/or for different sizes of stacks, the end
plates may be uniform but fitted with appropriate wedges.
- 20 -
1 Referring now to Figures 1~ and 20, an alternative
form of water unit is there shown and is designated generall~
by the reference numeral 26a. It comprises a water mattress
or bladder 110 formed of water-impermeable, gas-impermeable,
flexible material as in the case of the bladder or mattress 52
shown in Figure ~ and described hereinabove. This mattress is
fitted at one end (the right-hand end as viewed in Figure 1~)
with two inserts 111, each formed with a water flow-through
slot 112 and with lateral passages or grooves 113. At its other
end the bladder is fitted with an oxygen insert 114, which is
of solid construction and is formed with two oxygen flow-through
slots 115. Side members (not shown) such as those shown at 50
in Figure 8 will be employed.
The construction of the water insert 111 may be as
shown in Figure 8, that is to say, it may be formed of three
pieces, or it may have, and preferably it does have, the simpler
two-piece construction shown in Figure 9. The water mattress
110 is sealed at 116 from one end (the right end or water end~
to a point short of the oxygen insert, thereb~ leaving a space
or channel 117.
In operation with this type of water unit, oxygen
flows through the slots 115 in the oxygen insert 114 without
access to the interior of the waker bladder. Meanwhile water
flows in through the slot 112 in one of the inserts 111 and a
portion of the water flows through the lateral passages 113
into the interior of the water mattress on one side of the seal
116, then through the space 117 to the other side and out through
lateral passages 113 and slot 112.
An advantage of this type of construction is that
it minimizes the extent of stagnant areas of water.
- 21 -
~ 1 2 ~
1Referring now ~o Figures 15 -to 19, an alternative form
of oxygen unit is there shown which is generally designated by
the reference numeral 120. It comprises a screen 121 which,
except in the respects mentioned immediately below, is identical
with the screen 68 shown in Figure 8. The screen 120 is slotted
at 122 and is punched with holes 123.
At one end the screen 121 butts against a water flow-
through insert 124 having slo~s 125 which register with the slots
112 of the water units. At its other end the oxygen unit is
provided with an oxygen distributor or insert 125 which is formed
with oxygen flow-through slots 126 and lateral passages 127. As
will be seen in Figure 17, the inner edge of the insert 125 is
bifurcated to receive the adjacent end of the screen 121~
Further, the oxygen insert 125 is of two-piece construction as
shown in Figure 18, and the bottom piece is provided with pegs
128 which extend through holes 123 in the screen 121 and into
holes 130 in the top piece.
As will be further seen, a T-member 135 is provided
` the leg of which fits into the slot 122 in the screen 121 and
is also received in a notch 136 in the insert 125 to lock the
screen 121 and the insert 125 together. This oxygen unit will
be provided with side pieces 50 as shown in Figure 8.
In operation, water flows through the passages 125
without access to the interior of the oxygen unit and oxygen
flows through one of the slots 126 and a portion of the oxygen
flows through the lateral passages 127 into the interior of the
oxygen unit on one side of the T, then around through the space
137 at the end of the T and through the passages 127 into the
other slot 126 and thence to the next level.
30The blood oxygenator described above employs a gas-
permeable, water-impermeable member through which only gases
- 22 -
~ 7 ~ ~
1 flow. ~lowever, the apparatus of the invention is applicable
-to a more recent type of oxygenator which employs an aqueous
solution of hydrogen peroxide as the source of the Qxygen gas.
This type of oxygenator employs a semi-permeable membrane through
which water as well as gas may flow and through which small
solute molecules such as inor~anic salts may also pass. The
membrane is provided with a catalyst that acts to break down
the hydrogen peroxide diffusing through it into water and oxygen.
The hydrogen peroxide solution also contains salts to maintain
a suitable osmotic pressure, such salts being compatible with
the blood of the patient. This type of oxygenator is described
in U.S.Patents Nos. 3,846,236 and 3,996,141 and in papers by
the patentee, Stuart Updike, in Transactions of the American
Society of Artificial Internal Organs, Vol. 19, page 529, and
Vol. 20, page 286.
In applying the present invention to this type of
oxygenator, the ~nly changes (other than size, which could be
smaller with the hydrogen peroxide system) would be to use an
appropriate semi-permeable membrane which is permeable to gas,
water and small solute molecules but impermeable to the ~ormed
elements of the blood such as red and white blood cells, platelets
etc., and to proteins carried by the blood, etc. The membrane
would also embody a catalyst. Further, the oxygen circuit and its
components would be used with aqueous hydrogen peroxide solution
rather than gaseous oxygen.
The embodiment of Figures 23 to 32 will now be
described.
Referring now to the drawings and preliminarily to
Figures 23, 24 and 25, the device is indicated generally by the
reference numeral 210 and it comprises a container of box 211
- 23 -
~12~
1 having a tc>p 212, two sides 213 (one of which is sho~n in Figure 24),
two end walls 214 and a bottom 215. Bolts 216 and nuts 216a (see
Figures 27 and 28) serve to bolt the side and end walls to the
bottom. Bolts 217 and nuts 217a bolt the top 212 to the bottom 215
and serve also to clamp the blood, water and oxygen units together
and to resist water pressure and to maintain uni~ormity of the
blood paths. ~s shown in Figures 27, 28 and 29, O-rings are pro-
vided at 218 in grooves 218a as seals between the side and end walls
213 and 214 and bottom 215. The cover 212 is provided with ton~ues
220 which fit into grooves 221 in the side and end walls, the
spaces between the tongues and grooves being filled with a water-
proof cold setting glue 222. A blood inlet is shown at 225, an
oxygen outlet at 226 and a water inlet at 227. A blood outlet is
shown at 225a, an oxygen inlet at 226a and a water outlet at 227a.
(See Figures 23 and 24.)
Referring again to Figures 27, 28 and 29, a typical
assembly is shown including (from top to bottom) a water unit
230, an ox~gen unit 231 and a blood unit 232, a second oxygen unit
231, a second water unit 230, etc. As will be seen, each blood
unit 232 is sandwiched between two oxygen units 231 and in every
instance a blood unit 232 is separated from the adjacent water
unit or units 230 by an oxygen unit or units 231. The order or
sequence of units 230, 231 and 232 is elaborated herein~elow.
Referring now to Figure 25, the topmost blood unit 232
shown in that figure is illustrated in exploded view. It includes
two membranes 233 which form a blood space or path 233a between
them (see the blood unit below that shown in exploded view), a
screen 234 located in the blood space 233a between the top and
bottom membranes 233, side frame members 235 and end frame members
236, one at each end of the unit. Each side member 235 is made in
24 -
1 two parts consisting of a lower part 237 and an upper part 238.
The lower part 237 is formed with parallel transverse grooves 239
which provide channels for the flow of blood (inflow on the entry
side of the blood unit and outflow on the ~xit side of the blood
unit). Spaced at intervals along each side member 235 are bolt
holes 240 to receive bolts 217. Elsewhere, as will appear, there
are other bolt holes 240 which together with bolts 217 and nuts 217a
serve to secure the cover on the box, to hold the assembly o~ blood,
water and oxygen units together, and to resist the pressure of the
water units in a manner and for a purpose which is explained
hereinbelow. At each end each of the side members 235 is formed
, with a notch 245 and with a chamfered end por~ion 246 to mate with
a similarly chamfered portion 247 of the adjacent e~d piece 236.
At each end, each end piece 236 is also formed with a notch 248.
The notches 245 and 248 (also similar notches in other elements of
the apparatus as shown in the drawings) are intended to receive
tongues 249 projecting in from the side and end walls of the housing
so as to key together the inner components of the apparatus and
to align them properly. See Figure 26.
Ref~rring again to Figure 25, water units 230 are there
shown, each comprising a bladder or envelope 260 sealed along its
long sides or molded in the form of a seamless sleeve. At each
end of the envelope there is an insert 261 made in two pieces con-
sisting of a lower piece 262 and an upper piece 263, hoth of which
are slotted at 264, the lower part being also formed with trans-
verse grooves 265. The envelope 260 is sealed at its end at Z68
and it is formed with slots 269 in registry with slots 26~. Also,
the envelope 260 is formed with bolt holes 240 in registry with
bolt holes 240 in inserts 261. The pattern o~ these bolt holes is
shown in Figure 26 and is discussed below.
- 25 -
~ ~ 2~
1 Referring now to Figures 25, 27 and 28, each oxygen unit
231 is formed by a screen 275 located be-tween the membranes 233 of
the neighbouring blood units 232 (or by an adjacent membrane 233 of
a blood unit and the wall of a bladder 260 as at the top and bottom
of the assembly as shown in Figures 27, 28 and 29 and by side frame
pieces 276. The side pieces 276 are of a thickness equal to the
combined thickness of two oxygen units 232 and one water unit 230
except at the top and bottom of the stack where they are of a
thickness equal to the combined thickness of a single oxygen unit
231 and a single water unit 230. See Figure 28.
Spacers 277 are provided at the ends of the assembly
between neighbouring water units 230. These spacers 277 are co-
extensive with the inserts 262 in the water units and therefore
leave open the ends of the oxygen units beyond these spacers. See
Figures 25 and 29. This provides oxygen plenums as and for a
purpose described below. The spacers 277 are slotted at 278 in
registry with the slots 269 in the water envelopes and the slots
264 in inserts 261.
The inserts 261 of each water unit 230 are preferably
diagonally situated as are the open ends of th~ oxygen units,
whereby the flow of water through each water unit is ~rom one
corner to the diagonally opposite corner and the flow of oxygen
through each oxygen unit is from one corner to the diagonally
opposite corner.
Blood passes through the assembled device from blood
inlet 225 to a plenum 285 (see Figure 28) and at the level of each
blood unit 232 a portion of the blood flows through grooves 239
into the blood space 233a between the membranes 233, thence across
the blood space to the opposite side member 235 and through its
grooves 239 to a blood plenum 285, thence out through blood outlet
225a to the arterial system of the patient.
- 26 -
~2~
1 Water flows in ~hrough water inlet 227 then through slots
269 in the water envelopes 260, throuyh slots 264 in the inserts 261
and through slots 278 in spacers 277. At each level a portion of
the water flows throuyh ~rooves 265 into the respective envelope
at one end ana diagonally across the envelope out through-grooves
in the other end piece~ See Figures 25 and 27 (~s described above
with reference to Figures 1-22, diagonal flow is preferred
because it minimizes channeling and uneven flow.) The water in
the water units ~30 per~orms not only the function o~ applying
pressure but a]so of controlling blood temperature. The water
units therefore function as internal, integral heat exchangers and
dispense with the need of a heat exchanger external to the
oxygenator.
Referring now to Figures 26 and 29,an oxygen plenum 290
is provided at each end of the assembly, one such plenum being
shown in Figures 26 and 27 (the oxygen inlet end), there being a
similar plenum (not shown) at the other end which is preferably
diagonally situated with respect to the inlet plenum~ At the
level of each oxygen unit 231 a portion of the oxygen flows into
the respective oxygen unit (as indicated by the arrows in Figure 29
thence through the unit to the plenum at the other end and out
through oxy~en outlet 226.
Referring to Figure 26, as noted above the side and end
walls of the housing are formed with tongues 249 to fit into the
corresponding notches 245 of the various side and end members. This
construction serves to align the elements of the assem~ly properly,
and it leaves cavities 295 to receive a cold setting glue 296 which
is introduced after the units 230, 231 and 232 are assembled in the
housing and before the cover 212 is applied. The glue serves to
seal the assembly and to prevent shunts or leaks. That is to say,
- 27 -
1 leakage of ox~en and of the fluidx around corners is prevented.
The apparatus illustrated in Figures 23 to 32 is, of
course, usecl in conjunction with auxiliary equipment such as
that described in connection with Figures 1 to 22 and the same
order of water (W), oxy~en (o) and blood (B) units are preferably
employed.
Also, materials of construction may be as described
in connection with Figures 1 to 22.
Similar procedures may be employed in testing the
components of the apparatus o~ Figures ~3 to 32 but for the sake
of completeness and because there are differences these procedures
are described below.
Each blood unit 232 is tested separately for leaks and
each water unit 231 is tested separately for leaks before assem-
bling. Each blood unit is tested by clamping it between plates in
a testing device, filling it with distilled water, and observing
whether there are water leaks, either by observation of pressure
change or by observation of drop in a column of water in a trans-
parent tube extending up from the outlet.
The water units 230 may be tested similarly but more
conveniently by filling them with air under pressure and observing
a pressure gauge to determine holding or loss of pressure.
When the units have been assembled the water circuit is
filled with compressed air and a pressure gauge is employed to
determine whether there is a drop in pressure. Then the blood
circuit is tested by filling it with distilled water while main-
taining air pressure in the water circuit. Any outward leakage
from the blood circuit is visibly evident. A leak from the inter-
ior of the blood circuit, e.g., from one of the blood envelopes,
is made evident by the presence of water in the oxygen circuit
.
- 2~ -
1 which remains open and will leak water through its outlet.
After assembly the oxygenator is sterilized, for
example, by approved ethylene oxide sterilization procedures.
Assembly is carried out as follows: The housing 11 is
constructed except for the cover 212, by applying O-ring-seals
218a to grooves 218 and applying bolts 216 and nu~s 216a to erect
the side and end walls 213 and 214 on the bottom or base 215.
Referring now to Figures 25, 27, 28 and 29, bolts 217 ~without nuts
217a) are installed. Then the first side pieces 276 are installed
by threading them over bolts 217 along the sides of the housing.
Then the first (bottommost) water unit 230 is installed by thread-
ing end bolts 217 through bolt holes 240 in inserts 261 and water
bladder 260. End spacers 276 are then installed. Then an oxygen
screen 275 is laid over the water bladder within an area defined
b~ side pieces 276 and end spacers 277. Then a blood unit 232 is
installed by threading bolts 217 through bolt holes 240 in the side
pieces 235 and the membranes 233 of the blood unit. This procedure
is then repeated until the full complement of blood, water and
oxygen units and the necessary side pieces 276 and end spacers ~77
have been installed, care being taken to select side pieces 276 of
proper thickness to bridge the space between successive modules.
Also, account is taken of the order of W, O and B units. The top
and bottom units are water units. The cover 212 is applied by
fitting the circumferential tongues 220 into the grooves~221,
passing the bolts 217 through bolt holes 240 in the cover and
applying and tightening nuts 217a. Adhesive is applied through
injection ports (not shown) in the cover to the circumferential
grooves 221 in side and end walls 213 and 214.
In start up and after testing the apparatus is primed
and in priming care is taken to remove all air or other gas from
- 29 -
~L~Z7~a9~
1 the blood ancl water circuits. This is aided by tilting the
housing 211 so that the long edge o~ the housing (i.e., the edge
viewed in ~igure 24) is lower than the opposite edge and so that
the blood inlet~ right-hand end of the housing (as viewed in
Figure 24) is lower than the left-hand end. Therefore, the blood
flow (also th~ water flow) at all times has an upward component.
Therefore, when the apparatus is primed and ready for use, it is
free of entrapped gas, and i~ remains free of gas during use. This
is, as noted, especially important in the case of the blood circuit.
The apparatus is held, by suspension or otherwise, in this doubly
tilted attitude (i.e., tilted about one edge and about one end)
during use.
Referring to Figure 26, it will be seen that water
outlet 227a which is shown in broken line (also water inlet 227
diagonally opposite and at the other end of the housing) are
centered on slots 264 and that end bolts 217 are symmetrical with
respect to slots 264 (although the inside bolts 217 are spread
farther apart to avoid interference with the grooves 265, see
Figure 25). This provides (when nuts 217a are tightened) a more
secure and uniform seal between end spacers 277 and the water
bladder 260. Also, joints between the top and bottom bladders 260
and the water inlets and outlets 227a and 227 are made more secure
and leakproof.
The cover 212 serves to react against or resist the
water pressure in the water units 230. The water pressure is
controlled to exceed that of the blood pressure in blood units 232.
If the water envelopes 260 were allowed to expand freely, unequal
pressures would be applied to the membranes 233. The cover 212 acts
to prevent this, to apply pressure evenly to the membranes 233 and
to hold them against screens 234 (which define the depth of the
- 30 -
1 blood pa-ths) ~o as to ensure uniformity of depth of the blood
paths.
As in the case oE the apparatus o~ Figures 1 to 22,
dimensions of the apparatus are o~ impor-ta~ce in the light of
requirements of a patient. The same or similar criteria and
recommendations apply to the apparatus of Figures 23 to 32.
As in the case of Figures 1 to 22 the water and blood
circuits operate at pressures higher than the pressure in the
oxygen circuit, and the water and blood circuits are so designed
that any leakage from the water circuit will be either to the
exterior of the apparatus or into the oxygen space. Therefore, .
leakage of water into the blood circuit is precluded. ~lso, as
in ~igures 1 to 22 gas permeable-wa-ter impermeable membranes may
be used or, in the event that hydrogen peroxide is used, membranes
permeable to water and small solute molecules but impermeable to
larger constituents of the blood may be used.
Among advantages of the apparatus o~ Figures 23 to 32
(in addition to advantages shared with the apparatus of Figures
1 to 22) are the following: The blood plenums 285 (see Figures
23, 26 and 28) ensure a more uniform flow of blood through the
hlood paths 233a. Note that they are oppositely tapered, being
widest at the blood entry end in the case of the plenum on one
side ~the blood entry side) and narrower at the ot'ner end while
on the opposite (blood outlet) side the taper is opposite to
adjust for the diminishing flow of blood on the entry side from
the blood inlet to the opposite end and for the increasing volume
of blood in the same direction on the outlet side. Blood does
not flow vertically (as viewed in Figure 28) through the side
members 235 of the blood frame, but only horizontally through the
grooves 239. This simplifies construction and it avoids stagnant
regions in the blood supply.
- 31 -
~12~
1 The oxygen plenums 290 (see Figures 26 and 29) provide
similar advantages.
Looking at Figure 28 it will be seen that bolts 217 are
on the center lines of side frame pieces 276. Likewise, as
explained above and as shown best in Figure 26, bolts 217 passing
through inserts 261 and through end spacers 277, although not on
center lines, are symmetrical to ~he center lines of these members.
The pressure exerted on the assembly of members 235, 260, 276 and
277 therefore acts uniformly and applies a uniform sealing pressure
to the blood and oxygen units and prevents leakage of any of the
fluid into the wrong units.
In the assembly shown in Figures 23 to 32 and described
above, the water circuit is at a higher pressure (e.g., at 14 psig)
than the blood (e.g., 6 psig). Therefore the water envelopes 260
will tend to expand. The expansive force of the water envelopes
260 is resisted by the cover 212 and bottom 215 whereby the depths
of the blood paths 233a are kept uniform. It is an advantage of
the structure shown that the cover may be of relatively thin,
flexible material, e.g., 1/16" to 1/8" polypropylene.
Yet another advantage is that it permits the use of a
box-like housing 211 which, together with the assembly of units
230, 231 and 232 and side pieces 276 and end spacers 277 form inlet
and outlet blood and oxygen plenums. This considerably simplifies
construction, e.g., it avoids the need to provide blood and
oxygen flow through passages (i.e., for flow from one blood or
oxygen ùnit to the next) in frame members used to construct the
blood and oxygen units.
Referring now to Figures 30, 31 and 32 an alternative
type of water unit is there shown and is generally designated by
the reference numeral 300. The unit 300 has an integral (albeit
- 32 -
~lZ~9~
1 made in two parts which are sealed together) frame 301 having end
portions 102 (only one being shown in Figure 30), side portions 303
and at each end a widened portion 304 which serves, in the manner
described below, as a water distributor and flow through member.
This frame is made of two identical parts/ an upper part (as
viewed in Figures 31 and 32) 305 and a lower part 305a which are
sealed together at 306 by any suitable means. Polyethylene or
other suitable flexible, expansible water-impervious sheets 307
are sealed, e.g., by heat, to the top and bottom halves of the
frame to form a water spacer 307.
The distribution and flow through member 304, which
corresponds to the insert 261 in the other figures described herein-
above, is formed with slots 308 and grooves 309~ The sheets 307
are formed with slots 310 in registry with slots 308. It will be
apparent that slots 308 and 310 are in registry with slots 278
in end spacers 278 (see Figure 27) for flow of water from one water
unit 300 to the next, and that at the level of each water unit a
portion of the water will flow through grooves 309 into water space
311 across the water space and out through an identical distributor
member 304 (not shown) at the other end and preferably diagonal
to the distributor shown in Figure 30.
It will therefore be apparent that new and advantageous
oxygenators of the membrane type and new and useful components of
such oxygenators have been provided.
- 33 -
