CA1128827A - Bubble oxygenator - Google Patents

Abstract

BUBBLE OXYGENATOR

ABSTRACT OF THE DISCLOSURE
The oxygenator is used for arterializing blood during open heart surgery. The oxygenator is factory-assembled and sterilized and is of economic and efficient design so that it can serve as a throwaway unit. Blood from the patient is oxygenated as it passes through the center of a tubular sparger with porous walls which supplies oxygen bubbles of the optimum size. The foaming blood is delivered to the top of the main oxygenator body where it is distributed by gravity flow downward across the heat exchanger tubing. The heat exchanger is wound as a flat coil with all connections outside of the oxygenator body. A silicone-coated sponge is located below the heat exchanger so that downwardly flowing foaming blood is defoamed as it passes through the sponge. Carbon dioxide and other gases are vented, and liquid blood gravitates into a tapered arterial reservoir.

Description

- 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 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 ' ', ~ , 3~28~
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.

3L12~ 7 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 ~%~
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 ~æ~
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 _ g _ .t 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 ~ D~ t~e ~

l~Zt~38~7 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 .

1~88f~
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 ~%~
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.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A blood oxygenator comprising:
a substantially rigid housing blood foaming means carried by said housing, including a venous blood inlet passageway, an oxygen inlet passageway and porous sparger means associated with said blood and oxygen inlet passageways to provide a flow of oxygen bubbles into the venous blood to create venous blood foam blood foam passage means communicating between said blood foaming means and an upper portion of said housing a heat exchanger carried in said housing below said upper portion to control the temperature of blood foam, and passage means for delivering blood foam to said heat exchanger defoaming means carried in said housing below said heat exchanger to receive by gravitational flow the blood foam from the heat exchanger and to separate liquid blood and gas and thereby defoam the blood and an arterial blood reservoir, including an outlet therefrom, defined in said body below said defoaming means to collect liquid blood gravitating from said defoaming means.

2. An oxygenator in accordance with claim 1, wherein said sparger is made of hydrophobic material and generally tubular shaped, with said venous blood inlet passageway extending therethrough.

3. An oxygenator in accordance with claim 2 further comprising an oxygen filter on the exterior of said sparger to filter oxygen passing therethrough.

4. An oxygenator in accordance with claim 1, wherein said heat exchanger is horizontally disposed and substantially spans the flow path of blood foam between said blood foam passage means and said defoaming means.

5. An oxygenator in accordance with claim 4, wherein said heat exchanger comprises a flat wound tubular coil.

6. An oxygenator in accordance with claim 1, further comprising distributor means above said heat exchanger for receiving venous blood foam from said venous blood foam passage means and distributing it to said heat exchanger, said distributor means comprising a substantially flat, imperforate distributor plate adjacent the blood foam passage means and a perforated distributor plate therebelow, said perforated plate having perforations above said heat exchanger to relatively evenly deliver blood foam to said heat exchanger.

7. An oxygenator in accordance with claim 1, wherein said heat exchanger comprises a continuous tube, the ends of which extend through said housing above the blood foaming level in said housing.

8. An oxygenator in accordance with claim 1, further comprising an interior funnel-shaped support member carried in said housing below said heat exchanger, said member carrying said defoaming means at its upper end and tapering toward its lower end to direct blood into said reservoir.

9. An oxygenator in accordance with claim 8, further comprising filter means carried at the lower end of said support member to filter blood received from said support member as it passes into said reservoir.

10. An oxygenator in accordance with claim 9, wherein said filter means comprises a tubular frame depending from said support element and carrying a synthetic polymer filter fabric.