Note: Descriptions are shown in the official language in which they were submitted.
- 1 BA CKGROUND 1 ?12'B~
2 This invention is directed to an oxygenator for
3 oxygenating and temperature-controlling blood in extra-
4 corporeal circulation during surgery.
Extracorporeal circulation has been a routine
6 procedure in the operating room for several years. An
7 important component in the extracorporeal blood circuit is
8 the blood oxygenator. The function of the oxygenator is to
9 transfer oxygen into the venous blood so that the oxygen
19 reacts with the hemoglobin with the resultant absorption of
11 the oxygen and release of carbon dioxide. A historical survey
1~ of blood oxygenators was published in the December, 1961 issue
13 of Surgery. The article was entitled "Theme and Variations
14 of Blood Oxygenators," by R. A. DeWall, et. al~
Three principle types of blood oxygenators are
16 known. In the membrane oxygenator, a semi-permeable membrane
17 separates the blood from the ox~gen, and gas exchange takes
18 place by diffusion through the membrane. One type of
19 membrane oxygenator is described in U. S. patent 3,413,095.
In the film oxygenator, a thin film of blood is
21 exposed to an oxygen atmosphere. One type of film oxygenator
22~ is described in the December 15, 1956 issue of Ths ~ancet,
23 page 1246, in an article entitled "Design of An Artificial
24 Lung Using Polyvinyl Formal Sponge."
The bubble oxygenator introduces ~ubbles of oxygen
26 directly into the blood. In the bubble oxygenator described
27 in U. 5. pa,tent 3,578,411, the bubble chamber has a continuous
28 convoluted path to promote the intermixing of the blood and
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1 the oxygen. U. S. patent No. 3,807,958 describes a bubble
2 oxygenator which employs a plurality of vertical tubes
3 through which the blood and oxygen mixture rises. U. S.
4 patent No. 3,898,045 describes a bubble oxygenator having
5 a lattice chamber tightly packed with spherical beads which
6 are asserted to improve gas exchange. In a bubble oxygenator
7 described in an article published in the August, 1957 issue
8 of Surgery, which was entitled "Preliminary Studies On the
9 Sponge-Oxygenator," by Adriano Bencini, et. al, a long
10 multi-perforated needle is positioned in a cylindrical piece
11 of polyurethane sponge. In U. S. patent 4,067,696, the
12 rising flow of the blood and oxygen admixture passes through
13 a three-dimensional open cell material which is asserted to
14 aid in gas exchange on the hemoglobin.
15 S UMMA RY
16 In order to aid in the understanding of this
17 invention, it can be stated in essentially summary form
18 that it is directed to a bubble oxygenator for use in an
19 extracorporeal blood circuit wherein oxygen bubbles are
20 delivered to the blood to cause foaming thereof, and the
21 foaming blood is distributed over a heat exchangex whence
22 it gravitationally descends and passes to a defoamer.
23 Carbon dioxide is vented upward out of the defoamer, and
24 liquid blood gravitates downward therefrom into an arterial
?5 blood reservoir~
26 It is thus an object of this invention to provide
27 a bubble oxygenator which is a high performance unit and
28 which offers significant clinical advantages, as well as
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1 conveniences to the user in a presterilized, low-cost,
2 disposable unit. It is another object to provide a bubble
3 oxygenator which has a substantially hard shell ~o that
4 it can maintain structural shape, as well as provide good
5 appearance and economic production methods by utilizing
6 injection-molded synthetic polymer composition materials.
7 It is another object to provide a blood oxygenator which
8 is economic so that it can be disposable to eliminate the
9 need for cleaning a~ter use, to overcome the possibility
10 of cross-contamination and to eliminate the cost of
11 cleaning a unit. It i5 a further object to provide a
12 factory-assembled blood oxygenator where assembly can be
13 accomplished with appropriate jigs and fixtures to provide
14 quality control in a "clean room" where the oxygenator can
lS be assembled and later pre-sterilized to be ready for use
16 to thus overcome the clinical and economic problems of
17 attempting to clean an oxygenator.
18 Other objects and advantages of the oxygenator
19 of this invention will become apparent from a study of the
20 following portion of the specification, the claims, and the
21 attached drawings.
22 BRIEF DESCRIPTION OF T~E DRAWINGS
23 FIGURE 1 is a plan view of the oxygenator of this
24 invention.
FIGURE 2 is a perspective thereof on reduced scale
26 showing the manner in which the oxygenator is connected to
27 a system and is mounted.
28 FIGURE 3 is an isometric view similar to FIGURE 2,
29 but showing the oxygenator mounted on a stand.
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1 PIGURE ~ is a section taken generally along the
2 line 4-4 of PIG~RE 1, with parts broken away and parts
3 taken in section.
4 FIGURE 5 is a section taken generally along the
5 line 5-5 of FIGURE ~, with parts broken away.
6 FIGURE 6 is a detailed isometric view of the
7 support clamp.
8 DESCRIPTION OF THE PREFER~ED EMBODIMENT
9 The preferred embodiment of the oxygenator of
10 this invention is generally indicated at 10 in FIGURES 1
11 through 4. Oxygenator 10 is manufactured as a permanently
12 assembled, low-cost, disposable unit which is principally
13 made of injection-molded parts so as to produce a substan-
14 tially rigid structure which can be presterilized. The
15 use of injection-molded parts makes for high quality,
16 reliable parts which 5an be inexpensively reproduced and
17 assembled, and yet provide for the cleanliness and reproduci-
18 bility which is important in such a structure.
19 In studying oxygenator 10 in structural and
20 functional detail, it will be considered in the direction
21 of blood flow therethrough. Venous blood inlet connection 12
22 is directed downwardly. This permits the venous connection
23 tubing 14 ~see FIGURE 2) which is directly connected to a
24 venous cannula in the patien~ to hang in a half loop which
25 makes it impossible for gas bubbles from the oxygenator to
26 escape back toward5 the patient. Side fitting 16 is also
27 an inlet fitting and is for the connection of tubing 18
28 from a cardiotomy reservoir, if one is used. If no cardiotomy
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lreservoir is used in the procedure, then tubing 18 is clamped.
2 Sample port 19 is connected by line 21 to connector 12 to obtain
3 venous blood sample. A Luer opening is provided for the sample
4syringe.
Sparger assembly 20, seen in sectional detail in
6FIGURE 4, has a cylindrical tubular body within which is
7itted sparger tube 22. An exterior, cylindrical, tubular
8space around the sparger tube is open for the receipt of
9oxygen from oxygen connector 24. The interior of sparger
lOtube 22 has approximately the interior diameter of venous
llblood inlet 12. Sparger tube 22 is a porous sparger. The
12porosity of sparger tube 22 is critical because it determines
13the size of the bubbles emitted. A porosity in the range of
1490 "TEGRAGLAS," as manufactured by 3M company, of Minneapolis,
15Minnesota, is proper, although another similar structure may
16be used. If the oxygen bubbles are too small, they oxygenate
17the blood but do not remove carbon dioxide. If the bubbles
18are too large, the opposite occurs with removal of carbon
gdioxide, but with inadequate oxygenation. With the porosity
20indicated, less than 1:1 gas-to-blood flow ratio produces
2lthe correct bubble size. A lesser oxygen flow produces
22sma11er bubbles and more oxygenation and vice versa.
23 The tubular shape of the sparger tube ensures that
24the entire volume of oxygen is evenly mixed with blood in a
25non-traumatic fashion. Since the oxygen bubbles flow inward
26into the blood, the blood is virtually floated over the inner
27surface of the sparger tube.
28 The sparger tube 22 may be made of or coated with
2ga hydrophobic material. This would prevent the outward flow
30of blood therethrough should the oxygen supply lose pressure.
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1 Furthermore, the outside of the spargPx tube 22 may ha~e
2 coating thereon which serves as an anti-bacterial filter,
3 to filter from the oxygen flow particles graded larger
4 than 0.2 micron. The coating is a layer of paste which
5 dries to a porous surface.
6 Some of the oxygenation and consequent carbon
7 dioxide removal takes place in the initial bubbling phase
8 as the blood foams in sparger tube 22 and as the foaming
9 mass rises. The blood with the entrained oxygen bubbles
(with oxygen-CO~ exchange beginning) proceeds upwardly
11 propelled by gas flow, buoyancy, and the venous inflow of
12 blood. Manifold 26 guides the upward flowing, foaming
13 blood into the top of dome 28 of the main body 30 of
14 oxygenator lO. The dome 28 is part of the cover of the
15 lower part of the body. Within dome 28, flat distributor
16 plate 32 receives the foaming blood. The foaming blood
17 proceeds horizontally across distributor plate 32. As the
18 blood foam flows across flat distributor plate 32, it is
l9 visible because the cover of the dome is transparent.
20 Thus, it is easy to inspect the blood to see that it
21 becomes bright red (as compared to the dark red venous
22 blood at the inlet) as the blood acquires oxygen. Should
23 the inflow of venous flow be uneven (for example, the result
24 of a suction that is too high), waves of foam can be seen
25 traversing flat distributor plate 32. This serves as a
2& good indicator to the perfusionist who will then reduce
27 the inflow rate.
28 The path through which the blood foam travels is
29 torturous, thus insuring ~otal mixing and gas exchange.
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1 This makes it possible to use small amounts of oxygen per
2 volume of blood. The low oxygen-to-blood ratios mean les~
3 agitation of the blood, and thus less trauma to the blood
4 cells. The lower oxygen ratio also produces less foaming
5 so that less defoaming is required, together with the
6 reduced oxygen cost.
7 Flat distributor plate 32 is spaced about 1/4 inch
8 from the outside shell of dome 28, and thus the foaming
9 blood is distributed around the edges where it descends by
10 gravity onto perforated distributor plate 34, The flow
11 space 36 around the edge of flat distributor plate 32 allows
12 the blood foam to flow downward without a~lowing any large
13 gas bubble accumulation. Perforations 3~ may be circular
14 holes or slots. The slots may be radially or angularly
15 di.rected, or arranged in any distribution to e~enly disburse
16 the foam as it passes downward through the perforations 38.
17 A thin disc-shaped dispersing layer 39 of foam may
18 be placed below distribution plate 34 and above heat
1~ exchanger 40. The foam is open-celled to permit blood flow
20 therethrough. The layer 39 may be uncoated to act as a
21 distributor to evenly distribute the blood foam over heat
22 exchanger 40, but preferably the foam layer 39 is silicone~
23 coated. The silicone coating starts the vapor-liquid separation
24 from the blood foam. This improvesliquid blood contact with
25 the coils of heat exchanger 40 to improve heat exchange
26 efficiency. This layer is not always necessary~
27 Heat exchanger 40 1S a pair of pancake-wound flat
28 coil heat exchanger coils. Cone 42 in the center of the
2~ coils is inserted to prevent the ~lood escaping through
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1 the center of coils without heat exchanging. The coils o
2 heat exchanger 40 are wound in opposite spirals in the ~ws
3 pancakes and are wound onto a mandrel which produces the
4 interior opening into which cone 42 is inserted. The heat
S exchanger coils have a small space between the pancake
6 windings, such as small space 44 and, with the pancakes
7 wound in opposite spirals, inevitably there are small spaces
8 between the coils of the two pancakes. ~hese spaces permit
~ the downward flow of the blood foam between the coils, and
10 yet with the small space, heat exchange is efficient.
11 - The positioning of the coiled heat exchanger tubing
12 is horizontal; the pancake position provides for slow,
13 parallel blood flow on the surface of the coils and through
14 the openings between the coils. This also results in less
15 cell damage. The horizontal positioning of the heat exchanger
16 is useful in producing a low overall structure and in maxi-
17 mizing the arterial reservoir volume. The coils may be
18 silicone-coated to encourage wet blood flow directly on the
lg heat exchange coils without the insulating effect of entrained
20 gas bubbles which provide the foam.
21 Another design feature presented by the particular
22 heat exchange structure is the fact that the point where the
23 heat exchanger tubing enters and leaves the oxygenator shell
24 is above the blood level llne at its highest point~ In this
25 way, complex sealing structures are not required, and there
26 is no blood loss at the tube juncture and the body. There
27 are no tubing joints within the body 30 of the oxygenator,
28 but both free ends of the heat exchanger tubing are brought
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1 out of the body. As is seen in FIGURES 1 through 4, the
2 coil ends 46 and 48 are shaped to have downwardly directed
3 connections. This permits the connection of water tubing,
4 such as tubing 50 and 52 (see FIGURE 2) by which the water
5 circulation is established through the heat exchanger tubing.
6 Withoùt a joint in the tubing within the shell, there is no
7 danger of water leakage into the blood. The downwardly
8 directed water connections enable the water-filled, heavily
9 loaded iines to drape naturally. Three-eighthsor one-half
10 inch outside diameter aluminum tubing is the preferred
11 material to use as the heat exchanger. Such material i5
12 easily formed and sterilized, is inexpensive, and has good
13 heat exchange properties. However, other suitable materials
14 can alternatively be used.
.,
Defoamer 54 is located interiorly of body 30 below
lS heat exchanger 40. The foaming blood flow which is distri-
17 buted all over the heat exchanger coil descends from the
i 18 héat exchanger coil onto defoamer 54. An open cell synthetic
19 polymer composition material such as "Scottfoam," which is
20 coated with silicon~ is employed as the defoamer. The surface
21 effect of the silicone separates the entrained gas from the
22 liquid blood so that the gas moves upward and can be vented.
23 Vent 56 is an opening in the cover of dome 28 for tne
24 addition of fluids and medications. Gap 60 is provided at
25 the periphery of dome 28 where it extends down around the
~6 top of the main body of the oxygenator.
27 The vent fitting 58 is provided so that vacuum
28 can be~attached to conduct harmful gases away from the
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1 oxygenator. Some of the anaesthetic gases used in the
2 operating room are placed in the blood and are vented along
3 with the carbon dioxide into the operating room when no
4 other provision is made. This may harm operating room
5 personnel. (There have been some reported cases of trauma
6 in opexating room personnel caused by exposure to such
7 anaesthetic gases.) Vent connector 58 permits the employment
of vacuum to withdraw the vented gases out of the operating
9 room. Dome 28 engages over body 30 and seals thereagainst,
10 except the gap 60 is a vent opening which allows the free
11 escape of the waste gases to the atmosphere. This escape
12 is provided for those cases where lt is not necessary to vent
13 the gases out of the operating room. When vacuum is used
14 through vent connector 58, free air is sucked into vent
15 opening 60 and thus pxevents lowering the pressure within
16 the oxygenator 60 to subatmosphere.
17 Dome 28 has skirt 62 depending downwardly there-
18 from. This skirt guides the downwardly flowing blood foam
19 onto the top of defoamer 54, and at the same time, provides
20 an outer passage through which the separated gases can
21 escape. Another circumferential body of defoamex sponge 64
22 is provided in this annular opening to ensure that no blood
23 foam reaches the chamber 84 or outside of the oxygenator
24 through vent connection 58 or vent opening 60.
Tray 66 supports the lower part of defoamer-body 54
26 and has exterior walls 68 which constrain the sponge around
27 the outer periphery. Tray 66 has feet 99 to rest on
28 reservoir 84 of oxygenator body 30. Gases or blood may pass
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1 between upper and lower parts of oxygenator 10. Filter
2 section 72 is part of the tray and is a conical or cylin-
3 drical structure 72 having a bottom 74. The filter
4 section 72 has its interior open to the space above tray 66
5 and may contain defoamer body 76. Filter 80 is a woven
6 filter which presents little resistance to the flow of
7 blood which passes down from the de~oamer body 54 interiorly
8 of filter section 72. Alternatively, filter 72 may be a
9 molded homogeneous porous structure. The blood outflowing
10 through filter 80 from filter section 72 is thus subjected
11 to final filtration. Filter 80 is preferably a woven.mesh
12 made from blood-compatible synthetic polymer composition
13 material with a preferred porosity between 100 and 250 microns.
14 The ~ilter material is blood-wettable so that, when it is
15 wet with blood, it prevents gaseous bubbles from passing
lS through. This is the final separation of gas from the
17 blood with the gas constrained on the inside of filter
18 section 72. Despite this constraint, the arterial reservoir 82
19 also has its top open to the vents by the opening between the
20 fit of the tray 66 onto shoulder 70 by means of feet 99.
21 Arterial reservoir 82 has enlarged large volumes
22 at the top by means of shoulders 108and 84 and a small
23 volume at the bottom by the tapered body 86 of the arterial
24 reservoir. This shape provides more resolution at the bottom
25 end with a larger storage capacity at the top~ The top end
26 widens suddenly by shoulder 84, but this is at a level which
~7 is normally above the usual, normal blood level. Thus,
28 should sudden reservoir capacity be required, it is available
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1 in a manner which requires little vertical space~ Further
2 space is in shoulder 84 until reservoir o~erflow through
3 vent opening 60.
4 Outlet pocket 88 is formed on the bottom of tapered
5 body 86 of the reservoir. Outlet fittings 90 and 92 are for
6 connection to outlet tubes 94 and 96. The arterial outlet
7 fitting 92 and its arterial tube line 96 deliver blood to
8 the arterial pump and thence to the patient. Arterial
9 fitting 90 and its tube 94 serve as a coronary pexfusion
10 outlet. Anti-vortex plate 98 is positioned over arterial
11 outlet 88 to prevent vortex formation. Blood flow is
12 unobstructed around the edges of the plate. The vortex
13 plate permits the blood level to be drawn considerably lower
14 in arterial reservoir 82 without ingesting air into the
15 arterial outlet line by means of vortexing. The arterial
16 outlet fittings 90 and 92 are directed downward so that
17 outflow is straight downward. This permits the arterial
1~ tubing to hang down in a natural arch under the arterial
19 reservoir without kinking.
Sample portllO has a Luer opening for arterial
21 blood sample-taking. The sample is taken through a tube
~2 positioned inside filter 80 and near the bottom of reservoir 82.
23 If air is blown in through arterial sample port 110, the
24 bubbles stay inside filter 80 and do not pass into the main
25 arterial blood reservoir.
26 In use in the operating room, the heart-lung pump
27 console usually has a vertical support rod 100 secured
28 thereto. Clamp lQ2 carries an open metal hoop 104 thereon.
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1 Hoop 104 fits unaer shoulder 70 of body 30. Hoop 10~ pivots
2 around pin 105 50 that the oxygenator can swing to any
3 convenient position. The open gap 106 permits the oxygenator
to be removed while the tubing is still attached to it without
5 the necessity of removal or cutting the tubing. This makes
6 removal and cleanup more convenient, yet allows the operator
7, to rotate the oxygenator into the desired position. Thus,
8 the oxygenator 10 is easy to use.
9 The shape of the oxygenator is such that it can be,
lO placed close, to the floor when in use, and thus blood can
11 be drained into it more efficiently. Little priming volume
l~ is required so that the hiological priming fluid or blood
used for priming prior to surgery is of smaller volume to
14 result in less cost, weight, and less risk of material
lS contamination. Dynamic holdup is reduced to produce fast
16 response.
17 Dimple 97 supports the filter structure and can
l~ receive an arterial reservoir temperature sensor.
l9 This invention having been described in its
2~ preferred embodiment, it is clear that it is susceptible to
21 numerous modifications and embodiments within the ability of
22 those skilled in the art and without the exercise of the
23 inventive faculty. Accordingly, the scope of this invention
24 is defined by the scope of the following claims.
26
27
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