CA1054012A - Blood oxygenator utilizing a removable membrane oxygenator unit - Google Patents

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 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. The port is transversely elongated whereby simple connection of an oxygen line to the second flow path of the oxygenator is prevented.

Description

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Background of the Invention - ' ' Membrane oxygenators for blocd are attracting growing ~-medical interest because of their capability of partially or com~
pletely taking over the respiratory ~unction oE 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. i: .

Commercially available disposable membrane oxygena- - -- tor units are disclosed in U. S. Patent No. 3, 757, 955. The ~; '"`~: ' ~`

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same pa~ent describes a membrane oxygenator unit currently under developn~ent in which the membrane is made o~ a porous, hydrophobic materia] such as 3 or ~ m:il polytetrafluoroethy-lene sheeting having an effectLve pore diameter of about 0.5 micron. Such mater:ials are capable of rapidly transferring oxygen, carbon d:Loxlcle and water vapor, whLle preventing the transfer oE blood itself through the membrane. Porous membrane oxygenator units exhibit an oxygen and carbon dioxide transEer capab~lity 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 of 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 3,927,9~0, 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 like for maintaining the appropriate blood temperature and other desirable parameters of operation.
For the commcrcial manufacturer of porous membrane blood oxygenator units, it is a matter of great lmportance to b~ certaLn that the customers utili2e the oxygenator unit ln a correct manner, using the correct equipment for mountin~
and supplying blood and oxygen to the membrane oxygenator unit, so that there will be no dangerous gas overpressure, driving oxygen b~lbbles into the blood path, which can instantly I
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. According]y~ a relatlvely foolproof I
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 prevent any obstruction of the flow of gas from the oxgyenator 1 unit, thus avoiding a consequent, potentially disastrous rise in the gas pressure of the oxygen flow path in the oxygen-ator unit.
; Description of the Invention The present invention is used in a blood oxygenator unit which defines a first plurality of blood flow channels and a ¦
~` second plurality of oxy&en flow channels in interleaving relation to the first flow channels, the first and second flow channels being separated by a semipermeable membrane, and an outer casing enclosing the membrane and the flow channels, the outer casing - having separate blood and oxygen inlets and outlets. The i`

~ 3 -jvb/jib .~ , , . .. . ,i , ' ' " ' . ,` .',! ' ~ , ~ ' ~C)5~2 invention relates to tl~e improvement wherein the oxygen inlet comprises a transversely elongated port defined in the casing, positioned to directly expose one end of all of tlle plurality of the second flow channels to the exterior of tile casing, whereby slmple connection oE thc second fLow ch~nnels to an oxygen l:lne is prevented.
~ s a result of thls arrangement, oxygen comes to the plate by mealls of an oxygen line, and is ~lanifolded 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 the device of this invention do not carry an oxygen manifolding means, and thus ` are not conveniently used with makeshift equipment. Hence, the user of a disposable oxygenator unit is strongly encouraged to utilize 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 oxygen flow paths comprising a plurality of interleaving, parallel channels. It is contemplated that the typical oxygenator units for use in accordance with preferred embodiments of this invention will have a wide mouth opening for inlet of oxygen `-`~ and outlet of spent gases to and from the oxygenator unit, with the inlets and outlets of the parallel, interleaved oxygen ; channels in the oxygenator unit being directly exposed to the exterior of the unit through the wide mouth openings. The manifold port on the plate of 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 jvb/jib . ~ .: :. : ' ' ; :

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to the membrane oxygenator unlt prevents the simple attach-ment of an oxygen line to the oxygenator unit, and thus encourages the use of the standard oxygenator equ.ipment especia].].y manuFclctured for use with the membrane oxygenator un:l.t, whlch w:Lll inc:Lude the neces;ary sa~ety :Eeatures such ~s a mealls for :I.imitlng ga~ pressure, a heat exchange unit, ~nd the like.
Furthermore, in position of use the plate, with the exception oE 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, 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 :;
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discussed above.

In the drawings~

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Figure l is a schemat:ic vlew of an oxygenator of this :;nvention, ~ith a porous membrane oxygenator unit installed in the holding means.
Figure 2 is a rear plan v:Lew of the oxygenator ~Init hold:Lng means of th:is lnvention, wltll one slde wall oE the ho:Ldlng meuns removed, wLthout an oxygenator present, and wlth the heat exchanger tneans shown ln phantom.
Figure 3 is a perspectlve vlew of the oxygenator unlt holdlng means of thls invention w:Lth a side wall removed, showing a typical membrane oxygenator unit prior to lnstallation in the oxygenator unit holdlng means.
Figure 4 is a side 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 oxygenator unit 14. ~eans 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 oxy- -genator 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.
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Downstream from the oxygenator, blood passes Erom the oxygenator into blood outlet tubing 18, and from there through heat exchanger 26 (such as disclosed in U.S. Patent ~o. 3,640,340)~
to arterial reservoir 28 by tube 19, Erom where it is propelled by a second roller pump 30 into the patient's arterial blood supply through conduit 32. Heat exchanger 26 is mounted on an elongated bracket 27 with its heat exchange fluid flow path mb/l~ - 6 ~
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inle~ and outlet in co~unication with ports 29, which pass through bracket 27 of holder 12 for connection with a heat ex-change fluid source.
A cardiotomy reservoir 34 can be provided to receive blood from a cardiotomy sucker which sucks blood from the pa-tient's incision site or the like, and passes it to the reser-' voir through line 36. The cardlotomy reservoir is connected by ¦ lin~ 38 to a filter 40, which in turn connects with the venous ' reservoir 22.
i 10 Unit holding means 12 is held by bracket 35, which in i turn carries a mast 37 having hangers 39, 41 for 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 Figures 2 through 5, details of oxygenator unit holder 12 and related parts are shown.
¦ Holder 12 is shown to carry an oxygenator unit engaging i `
t plate 42, 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 ~-I 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 freely 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 of oxygenator unlt 14 as shown in Figurès 3 and 5. As can be ssen from Figure 3, oxygen inlet 52 is elongated so that the many inlet ends of paralleI flow ;
, channels 54 of conv~:ntional oxygenators are all directly exposed to the exterior of ~he oxygenator unit through inlet 52. O-ring seal 46, as part of the m~nlfold port of plate 42, is propor-tioned to surround and seal inlet 52 of oxygenator unit 14 to provide a sealed oxygen flow path when unit 14 is installed in holder 12.
Oxygen flow path outlet port 56 of unit 14 is also typi.cally elongated to perm:it the free exit oE surplus oxygen yas, plus carbon dioxide and water vapor whi.ch is passed into the second flow path of oxygenator unit 14.
In Figure 5, a typical const.ruction of the layers which define flow paths 5~ is shown. Porous, semi-permeable membrane 14M overlies support screening 14S in a convoluted, multilayer arrangement as further illustrated in U.S. Patent

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 is encased between walls 15, which are held together by fasteners 17 (Figure 3).
As shown in Figure 4, oxygenator unit engaging plate 42 is 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 tvpically about l/8 inch wide. As a result of this, e~haust gas from outlet 56 :~ has unrestricted exit in a plurallt,y of directions through space 59 between plate 42 and unit 14. ~he result o~ this is to greatly reduce the probability of accidental obstruction o~ out-let 56, since gas will vent adequately from oxygenator unit 14 ~:
as long as any substantial portion of elongated space 59 remains ' open to the exterior. .
Plate 42 is attached to holder 12 by a removable nut :~
: 60 at one end and conventional dete{lt means 62 at its other end, so that plate 42 is easily removable from holder 12.
.- Line 64 and conduit 65 through cover 70 provide com- :
'~. munication between t,he oxygen inlet manifold port 44 and safety .

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mea;l~s 66, hcl(l by bra(~c~ 27, ror prevenL:I~g the pr~ssure of `-oxygen gas in the :inle~ manirold port frorn reaching a level suff:ic:Lent to cause gafi bubbles to pass through the porous, sem:i.permeable membrane 14m oE oxygenator unit 14. 'I`his safety mealls 66 comprises a l:i.qui(l-fLlled tube having a r:igid, tubuLar ext~ns:l.on 68 of li.ne 6/~, whlch saEety means funct.i.ons as a pressllle lim:iting devlce in the manner descr:Lbecl l.n U.S. Patent 3,~27,~0.
Oxygenator un:it holder 12 a].so comprises top and bottom plates 12p, ].2q, and side walls 12s, wh:lch 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 is 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, inlet -maniEold port 44 does not pass straight through plate ~l2, but ;~
; makes two 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 :
therein. :
. Heater block 69 is controlled by two thermostats 72, electrically connected together so that the disconnecti.on of ~ 30 either thermostat deactivates heater b:lock 69. The purpose of : ::
. this is to provide a high degree of assurance that the oxygen : gas is not overheated, si.nce oxygen gas temperatures in excess .:~

of ~2C. could cause serious damage to hlood in the oxygenator.
Fuse 73 is also provided for added safety. .: :

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Insul~ting wall 74 prevents ~ndue heat loss from heater block 69. If desired, an alarm means can be provided to activate alarm buzzer 78 when a pressure switch 79 mounted in fluid communication with the inlet manifold port 44 is not sensing a gas pressure in excess o a standard pressure of at least 6 inches of water, which is equivalent to approximately 5 liters per minute of oxygen flow throucJh port 44 when the port diameter is about 1/4 inch. This arrangement may comprise a conventional relay 80 activating buzzer 78 when the predeter-10 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 lii~e 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 20 the stack of screening and membrane layers, or it can be of U-` shaped cross-sectional construction to provide a pair of qxpan- ~
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 ;~
`~ relationship to the vertical by bracket 35, to elevate the blood outlet as shown in Figure 4, to facilitate the priming of the ` oxygenator unit with blood or sallne solution. ~he angular relationship facilitates the removal of all air bubbles from the oxygenator unit into outlet line 18 during priming. Bottom 30 plate 12q has a beveled lower edge 86 so that unit holder 12 assumes the same an~ular relationship to the vertical when ~` resting on a horizontal surface, before being hung by bracket 35 on arm 43. Thus, unit holder 12 can be conveniently loaded with ; : - ., . , ~ .
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an o~ygenator unit, and the unit prirned with saline solution, prior to hanyiny 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 below.

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Claims (2)

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

1. In a blood oxygenator unit which defines a first plurality of blood flow channels and a second plurality of oxygen flow channels in interleaving relation to said first flow channels, said first and second flow channels being separated by a semipermeable membrane, and an outer casing enclosing said membrane and said flow channels, said outer casing having separate blood and oxygen inlets and outlets, the improvement wherein said oxygen inlet comprises a transversely elongated port defined in said casing, positioned to directly expose one end of all of said plurality of said second flow channels to the exterior of said casing, whereby simple connection of said second flow channels to an oxygen line is prevented.

2. The blood oxygenator unit of claim 1 in which said semipermeable membrane is a porous, hydrophobic material capable of preventing the passage of blood while permitting the passage of oxygen and carbon dioxide therethrough.