CA1054010A

CA1054010A - Blood oxygenator utilizing a removable membrane oxygenator unit

Info

Publication number: CA1054010A
Application number: CA210,878A
Authority: CA
Inventors: Ronald J. Leonard
Original assignee: Baxter Travenol Laboratories Inc
Current assignee: Baxter International Inc
Priority date: 1974-01-21
Filing date: 1974-10-07
Publication date: 1979-05-08
Also published as: IL45836A; JPS5528696B2; IL45836A0; LU71206A1; JPS5384392A; US3929414A; BR7500044A; SE7808068L; CH591246A5; AU497069B2; AR203136A1; AU513942B2; IL52283A; SE7500592L; GB1480526A; FR2258190B1; IT1025095B; AU7447274A; AU4127178A; JPS50103198A

Abstract

ABSTRACT OF THE DISCLOSURE

An oxygenator for blood is disclosed which comprises means for removably holding a membrane oxygenator unit, means for conveying blood to a patient through the oxygenator unit in a first flow path and back to the patient. and means for supplying oxygen gas through the oxygenator unit in a second flow path separated from the first flow path in the unit by a semi-permeable membrane. The oxygenator unit holding means carries a selectively removable plate which has an oxygen inlet manifold port positioned to communicate with a mounted oxygenator unit, to provide a sealed oxygen flow path through the plate into the oxygenator unit.

Description

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BL,OOD OXYGEN~TOR UTILIZING A REMOVABLE ::
MEM13RANE OXYGENATO:E~ UNIT

Inventor: Rotlc~ J. I,eonard `

Background of the Invention ., .

Membrane oxygenators for blood are attracting growing ~.
metlical interest because of their capability of partially or com-pletely taking over the respiratory function of a patient for a period of many hours and even days without unacceptable damage `.
to the blood supply. Previously, bubble-type oxygenators in-volving the direct application of oxygen bubbles through a stream . :
of blood had been used in open heart surgery for periods up to four or five hours. However, unacceptable damage frequently is inflicted upon the blood supply of the patient if the bubble ~oxygenators remain in operation for periods significantly longer than this.

Commercially available disposable membrane oxygena~
tor units are disclosed in U. S. Patent No. 3, 757, 955. The . .. .

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same patent describes a meinbrane ox~genator unit currently under development in which ~he membrane is made oE a porous, hydrophobic materia] such as 3 or ~ mil polytetrafluoroethy-lene sheeting havLng an effective pore diameter oE about 0.5 nllcron. Such mater:Lals are capnble of rapidly transferring oxy~en, carbon dLoxide and water vapor, while prevent:Lng the transfer of blood ltself through the membrane. Porous membrane oxy~enator units exhibit an oxygen and carbon dioxlde transfar ~!
capability which greatly exceeds the older membrane oxygenator unit designs which utili%e thin silicone rubber membrane and ' the like. Accordingly, porous membrane oxygenator units can support the total respiratory needs oE a patient with a signi-ficantly smaller total surface area of membrane than a conven-tional silicone rubber membrane oxygenator unit of similar design. As a result of this, the amount of blood which is : ,: .
removed from the body at any one time can be typically less with porous membrane oxygenator units, which is a significant ~ -and important advantage. `
There is, however~ a drawback to porous membrane oxygenator units: it is absolutely necessary for the pressure on the blood side of the membrane to at all times equal or ` exceed the pressure on the gas side of the membrane. If these ' conditions fail, the increased gas pressure may drive gas bubbles through the membrane into the blood flow path, from where the gas bubbles may be conveyed back to the patient. This could " create a life-threatening embolism in the patient. `~
Accordingly, in applicant's U.S. patent 3,927,980, issued December 23, 1975, an oxygenator apparatus is provided for the safe and effective utilization of hydrophobic, porous membrane blood oxygenator units. In the device described in the patent, a manometer means is provided to assure safe and reliable limitation of the gas pressure in the oxygenator unit.

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Also, the aforesaid patent discloses heat exchanging means and the l:ike for maintaining the appropriate blood temperature and other desirable parameters of opcration.
For the commerc:ial man~lEacturer oE porous membrane blood oxygenator un:Lts, it is a matter oE great importance to be certain that ~he customers ~ItiLi~e the oxygenator unit ln a correct manner, using the correct equipment for mounting and supplying blood and oxygen to the membrane oxygenator unit, so that there will be no dangerous gas overpressure, driving oxygen bubbles into the blood path, which can instantly create a life-threatening situation.
In accordance with this invention, an oxygenator and membrane oxygenator unit for use therein are provided in which the membrane oxygenator unit is used only with great `, difficulty apart from the oxygenator itself, which can be designed to provide the necessary parameters of operation ` that result in safe use. Accordingly, a relatively foolproof "~
system is provided for the protection of patients.
Furthermore, in accordance with this invention, a system is provided for assured, unrestricted exhaust of gas, to prevPnt any obstruction of the flow of gas from the oxgyenator unit, thus avoiding a consequent, potentially disastrous ; rise in the gas pressure of the oxygen flow path in the oxygen~
ator unit.

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Desc~tion of the Inventlon __ ____ _ _ , The present lnventLon is used in an oxygenator for blood which comprlses bracket menns removably holdlng membrane mcans for the oxygenat:ion of blood, means for conveylng blood from a patLent through the membrane means mounted in ~hc bracket means in a flrst flow path and back to the patient, means for supplying oxygen gas through the membrane means mounted in the bracket means in a second flow path separate ;, : , from the first flow pa~h and separated therefrom in the membrane means by a semi-permeable membrane, the second flow path comprising in the membrane means a plurality of parallel ~`
flow channels. The invention relates to the improvement comprising, in combination the bracket means carrying plate means eelectively removably engaging the membrane means for oxygenation of blood, the plate means including means defining an oxygen inlet manifold port positioned to directly communicate, in engaging position, with the parallel flow channels of the ! j second flow path in the membrane means, to provide a sealed oxygen flow path through the plate into the oxygenator unit. `
. i In a particular embodiment, oxygen comes to the plate -~

by means of an oxygen line, and is manifolded or spread into :: :
a wide flow path for delivery to the individual oxygenator unit flow channels by means of parts carried by the oxygenator itself rather than the oxygenator unit. As a result of this, ~ ~
oxygenator units desired for use with such devices do not ~ ~i carry an oxygen manifolding means, and thus are not conven-iently used with makeshift equipment. Hence, the user of a disposable oxygenator unit is strongly encouraged to utili~e :
the standard equipment for that unit with its tested safety .
features, rather than to inconveniently improvise his own arrangement of apparatus.
A typical membrane oxygenator unit defines blood and , :` :
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oxyKen flow paths comprLsing a plurality of interleavlng, parallel channels. It is contemplated that the typical oxygenator units for use in accordance with preferre~ embodiments of this invention will have a wide ~nouth opening for inlet of oxygen and outlet of spent gases to and ~rom tlle oxygenator unit, with the inlets and outlets of the paralle:l, interleaved oxygen channels in the oxy-genator unLt be:Lng directly exposed to the exterior of the unit through the wide mouth openings. The manifold port on the plate oE the blood oxygenator is accordingly proportioned to surround and seal the wide mouth opening around the inlets of the parallel channels, to provide the sealed oxygen flow path. The wide mouth opening of the oxygen inlet to the membrane oxygenator unit pre-vents the simple attachment of an oxygen line to the oxygenator unit, and thus encourages the use of the standard oxygenator equipment especially manufactured for use with the membrane oxy-genator unit 9 which will include the necessary safety features such as a means for limiting gas pressure, a heat exchange ' unit, and the like.
~` Furthermore, in position of use the plate, with the exception of the manifold port area, is spaced from the membrane oxygenator unit in a position to overlie the gas outlet port of ;~
the second flow path of the oxygenator unit. Accordingly, oxygen gas escapes through the outlet port, then passing in many directions `
` of flow between the oxygenator unit and the plate to the exterior.
The advantage of this is that such arrangement greatly reduces the ~` :
possibility of some accidental obstruction of the gas outlet ' port, such as might take place if the outlet port were a simple `~
tube or opening. The reason this is necessary is that the `
accidental placement of some obstructing object, even momentarily, ` 30 in front of the gas outlet port during operation could cause a ~;
sudden rise of gas pressure within the membrane oxygenator unit~
which is dangerous for reasons discussed above.
Tn the drawings~ ?

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Figure 1 is a schematic view of an oxygenator of thisinvention, with a porous membrane oxygenator unit installed in the holding means.
~ 'igure 2 is a rear plan view of the oxygenator unit holding means of this invention, with one side wall of the hold-ing means removed, without an oxygenator present, and with the heat exchanger means shown in phantom.
Figure 3 is a perspective view of the oxygenator unit holding means of this invention with a side wall removed, showing a typical membrane oxygenator unit prior to installation in the oxygenator unit holding means.
Figure 4 i9 a sidP elevational view of the oxygenator unit holding means of this invention with the oxygenator unit installed, portions of the oxygenator unit and holding means being broken away and shown in section.
Figure 5 is an enlarged view in vertical section of the vicinity of the oxygen inlet of the oxygenator unit as shown ~-in Figure 4.
Referring to the drawings, an oxygenator is shown which comprises, means 12 for removably holding a membrane oxy genator unit 14. Means for conveying blood from a patient through the oxygenator in a first flow path and back to the .. ~ , patient are also provided. Blood in inlet tube 16 is propelled through the oxygenator by a conventional roller pump 20, being drawn out of the venous reservoir 22. Blood is supplied to the venous reservoir through conduit 24 from the patient's venous supply.
Downstream from the oxygenator, blood passes from the oxygenator into blood outlet tubing 18, and from there ~hrough heat exchanger 26 (such as disclosed in U.S. Patent No. 3,640, 340), to arterial reservoir 28 by tube 19, from where it is propelled by a second roller pump 30 into the patientls arter-.
ial blood supply through conduit 32. Heat exchanger 26 is ~ e/O~g~c~mounted onl~bracket 27 with its heat ex~hange fluid flow path , . . , :: , '''' ' ~ i4~
lnlet and outlet in communication with ports 29, which pass through br~cket 27 of holder l~ for connection with a heat ex-change fluid source.
A cardiotomy reservoir 34 can be provided to receive blood from a cardiotomy 3ucker which suc~s blood from the pa-tlent's incision site or the like, and passes it to the re~er-voir through line 36. The cardiotomy reservoir is connected by line 38 to a filter 40, which in turn connects with the venous re~ervoir 22.
Unit holding means 12 is held by bracket 35, which in turn carries a ma~t 37 having hangers 39, 41 ~or remo~ably holding blood containing components of the oxygenator. Bracket 35 is in turn held on a hanger 43 which is attached to suppor-ting member 45.
Referring AlSo to F~gures 2 through 5, details of oxygenator unit holder 12 and related parts are shown.
Holder 12 is shown to carry an oxygenator unit engaging plate ~2, which in turn defines an oxygen inlet manifold port 44 which terminates at its inner end with an O-ring seal 46. A
,source of oxygen gas is provided through oxygen inlet line 48 to communicate with oxygen inlet manifold port 44, which provides a sealed oxygen flow path through the plate into the oxygenator ~ ~`
unit.
`Recessed portion 50 within O-ring seal 46 is provided -to permit the oxygen gas to ~reely flow throughout the entire interior of O-ring seal 46.
Inlet manifold port 44, O-ring seal 46, and recessed ~`portion 50 are positioned to communicate in sealing relation with the oxygen inlet 52 o~ oxygenator unit 14 as shown in Figures 3 and 5. As can be seen from Figure 3, oxygen inlet 52 is elongated sa that the many inlet ends of parallel flow channels 54 of conventional oxygenators are all directly exp~sed to the exterior of the oxygenator unit ~hrough inlet S2. O-ring :
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~eal 46, as part of the mani~old port of plate 42, ls propor-tioned to ~urround and ~eal inlet 52 of oxygenator unlt 14 to provide a s2aled oxygen flow path when unit 14 i8 ingtalled in holder 12.
Oxygen flow path outlet port 56 o~ unit 14 is al~o typically elongated to permit the free exit of surplus oxygen gas~ plus carbon dioxide and water vapor which is passed into the second flow path of oxygenator unit 14.
In Figure 5, a typical construction of the layers which define 10w paths 54 is shown. Porous, semi-permeable membrane 14M overlies support screening 14S in a convoluted, : :
multilayar arrangement as further illustrated in U.S. Patant

3,757,955. The edges of the membrane and screening are sealed together by a line of cured potting compound 14P, and the struc- :
ture iB encased between walls 15, which are held together by fasteners 17 ~Figure 3).
A~ ~hown in Figure 4, oxygenator unit engaging plate 42 i~ positioned to be spaced from and define an unbroken wall 58 over gas outlet port 56 of the oxygenator unit in position of use and separated by space 59, which is typically about 1/8 inch wide. As a result of this, exhaust gas from outlet 56 has un~estricted exit in a plurality of directions through :;
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spa~e 59 between plate 42 and unit 14. The re ult o~ this is to ~ ;
greatly reduce the probability of accidental obstruction of out-.- .
A let 56, ~in~e ga~ will vent adequate}y from oxygenator uni~ 14 ; as long as any substantial portion of elongated space 59 remain open to the exterior.
Plate 42 i~ attached to holder 12 by a removable nut 60 at one end and conventional detent means 62 at its other end, ~o that plate 42 i8 easily removable from holder 12.
Line 64 and conduit 65 through cover 70 provide com- :
munication between the oxygen inlet maniold port 44 and ~afety .... . .

n1calls G6, hc](l l-y braclict 27, Eor preventirlp, thc pressure of oxygen gas ln tile inlet m~lnifo]d port frol~ reaching a level suff iC:iell~ to ca~lse gas bubbles to pass thro~ the porotls, semLpermeable membrane l4m of oxygcll~t:or unlt :t4. Ihis saEety means 66 com~rises a lL~Iu~ ELlled tubc h~vlng a rlgl(l, tub~llar ext:ens:Lon 68 of line 6~, which sAEety meclns funcLLons as a preC~s~lre ]:LmitLng devLce in the manner described ln U.S. Patent 3,~27,980.
Oxygenator unit holder 12 ~lso comprises top and ~ -bottom plates 12p, 12q~ and side walls 12s, which are secured together in the manner previously described for plate 42, by means of nuts 12n which fit on bolts 12b, and detent means 12d.
Plate 12p ls attached by gluing or welding to bracket 35.
Oxygenator unit 14 is optionally not enclosed along its rear, blood flow side.
In the specific embodiment shown herein, in]et manifold port 44 does not pass straight through plate 42, but `" makes t~o right angle turns as shown in Figure 4 so as to pass through a U-shaped heater block 69 which is mounted within cover 70 which, in turn, is carried by plate 42. Heater block . , ~
69, through which inlet manifold port 44 passes as an elongated ~-- channel, provides means to warm the oxygen gas entering into ,; - :
the oxygenator unit to a predetermined temperature. ~ typical heater block 69 usable herein can be a typical 45 watt, 120 volt, 3-ohm electric cartridge heater. Conduit 65 also passes through heater block 69 to communicate with manifold port 44 i therein. `~ ~-- . Heater block 69 is controlled by two thermostats 72, - ~-electrically connected together so that the disconnection of 30 either thermostat deactivates heater block 69. The purpose of this is to provide a high degree of assurance that the oxygen gas is not overheated, since oxygen gas temperatures iTI excess of 42C. could cause serious damage to blood in the oxygenator.
Fuse 73 is also provided for added safety.

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Insulating wall 74 p~events undue heat loss from heater block 69. If desired, an alarm means can be provided to activate alarm huzzer 78 when a pressure switch 79 mounted in fluid communication with the inlet manifold port 44 is not sensing a gas pressure in excess of a standard pressure of at least 6 inches of water, which i5 equivalent to approximately 5 liters per minute of oxygen flow through port 44 when the port diameter is about 1/4 inch, This arrangement may comprise a conventional relay 80 activating buz~er 78 when the predeter-mined gas overpressure is not sensed.
Port 82 is defined completely through plate 42 and cover 70 to permit the passage of inflation line 84 of oxygen-ator unit 14 therethrough. Inflation line 84 communicates with an inflatable shim inside of oxygenator 14 which can be used to pressurize the screening layers 14s and membrane layers 14m together to counter-balance the tendency of the oxygenator unit to expand due to the blood pressure pushing the screening and membranes apart.
The inflatable shim may be placed at the midpoint of the stack of screening and membrane layers, or it can be of U-shaped cross-sectional construction to provide a pair of e,xpan~
sion members on each side of the stack for the same purpose.
Other designs of inflatable shim can also be used.
Typically,unit holder 12 is positioned at an angular relation~hip to the vertical by bracket 35, to elevate the blood outlet as ~hown in Figure 4, to facilitate the priming of the ~ ; ;
oxygenator unit with blood or saline solution. The angular relationship facilitates the removal of all air bubbles from the oxygenator unit into outlet line 18 during priming. Bottom plate 12q has a beveled lower edge 86 so that unit holder 12 a3sumes the same angular relationship to the vertlcal when resting on a horizontal surface, before being hung by bracket 35 on arm 43. Thus, unit holder 12 can be conveniently loaded with - ~5~
an oxygenator unit, and the unit primed with saline solution, prior to hanging on arm 43.
The above has been offered for illustrative purposes only, and is not intended to limit the invention of this appli-cation which is as described in the claims ~elow.

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Claims

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

1. In an oxygenator for blood which comprises:
bracket means removably holding membrane means for the oxygenation of blood, means for conveying blood from a patient through said membrane means mounted in said bracket means in a first flow path and back to said patient, means for supplying oxygen gas through said membrane means mounted in said bracket means in a second flow path separate from said first flow path and separated therefrom in said membrane means by a semi-permeable membrane, said second flow path comprising in said membrane means a plurality of parallel flow channels, the improvement comprising, in combination:
said bracket means carrying plate means selectively removable engaging said membrane means for oxygenation of blood, said plate means including means defining an oxygen inlet manifold port positioned to directly communicate, in engaging position, with said parallel flow channels of the second flow path in said membrane means, to provide a sealed oxygen flow path through said plate into said oxygenator unit.

2. The oxygenator of claim 1 which carries means for heat exchanging in flow communication with blood passing through said oxygenator.

3. The oxygenator of claim 1, the improvement further comprising said parallel flow channels of the second flow path being directly exposed to the exterior of said membrane means for the oxygenation of blood, and said second flow path of the membrane means having an inlet which is transversely elongated to facilitate said exposure, said oxygen inlet manifold port means being porportioned to surround and seal said inlet to provide said sealed, oxygen flow path.

4. The oxygenator of claim 3 which includes safety means carried by said oxygenator for preventing the pressure of said oxygen gas from reaching a level sufficient to cause gas bubbles to pass through said membrane and to enter said first flow path, and in which said oxygen inlet manifold port means is in fluid communication with a conduit for providing gas pressure communication between said oxygen flow path and said safety means.

5. The oxygenator of claim 3, the improvement further comprising said plate means, in its position of engagement with the membrane means for oxygenation of blood, being positioned to be spaced from and to define an unbroken wall over the outlet of said second flow path of the membrane means, whereby exhaust gas from said second flow path has unrestricted exit in a plurality of directions between said plate means and membrane means to prevent accidental obstruction of said outlet of the second flow path.

6. The oxygenator of claim 5 in which an O-ring seal is positioned between said oxygen inlet manifold port means and the inlet of the second flow path of the membrane means.

7. The oxygenator of claim 6 in which said semi-permeable membrane is a porous, hydrophobic material capable of preventing the passage of blood while permitting the passage of oxygen and carbon dioxide therethrough.

8. The oxygenator of claim 7, the improvement further comprising said membrane means for the oxygenation of blood being disposed in angular relationship to the vertical to elevate the first flow path outlet from said membrane means above all other flow portions in said membrane means, to facilitate gas bubble removal from the first flow path.