U.S. patent number RE36,774 [Application Number 08/842,528] was granted by the patent office on 2000-07-11 for cylindrical blood heater/oxygenator.
This patent grant is currently assigned to Baxter Healthcare Corporation. Invention is credited to Daniel A. Baker, Louis C. Cosentino, Jeffrey A. Lee.
United States Patent |
RE36,774 |
Cosentino , et al. |
July 11, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Cylindrical blood heater/oxygenator
Abstract
A combination heat exchanger and oxygenator device is provided.
The device includes a generally cylindrical housing having first
and second compartments with hollow heat exchange tubes and hollow
gas exchange tubes disposed therein, a blood inlet, a blood outlet,
a heat exchanges medium inlet, a heat exchange medium outlet, an
oxygenating fluid inlet and an oxygenating fluid outlet. The
housing has a central axis with the second compartment being
concentric thereto. The blood flow passage is defined by blood
entering the device generally axially through a path extending
along the central axis of the housing and flows generally radially
through the second, oxygenating compartment.
Inventors: |
Cosentino; Louis C. (Deephaven,
MN), Lee; Jeffrey A. (Plymouth, MN), Baker; Daniel A.
(Minnetonka, MN) |
Assignee: |
Baxter Healthcare Corporation
(Irvine, CA)
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Family
ID: |
26780011 |
Appl.
No.: |
08/842,528 |
Filed: |
April 24, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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263817 |
Jun 22, 1994 |
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115996 |
Sep 2, 1993 |
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844620 |
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Reissue of: |
511287 |
Aug 4, 1995 |
05578267 |
Nov 26, 1996 |
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Current U.S.
Class: |
422/46;
210/321.64; 210/321.79; 210/321.88; 261/DIG.28; 426/48 |
Current CPC
Class: |
A61M
1/1698 (20130101); B01D 63/02 (20130101); B01D
63/04 (20130101); A61M 1/1629 (20140204); B01D
63/025 (20130101); A61M 1/1625 (20140204); A61M
2206/16 (20130101); Y10S 128/03 (20130101); B01D
2313/38 (20130101); Y10S 261/28 (20130101) |
Current International
Class: |
A61M
1/16 (20060101); B01D 63/02 (20060101); B01D
63/04 (20060101); A61M 001/14 () |
Field of
Search: |
;422/46,48 ;261/DIG.28
;210/321.64,321.79,321.88 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 114 732 |
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Aug 1984 |
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EP |
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0 217 759 |
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Apr 1987 |
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EP |
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24 56 932 |
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DE |
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2 267 138 |
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Dec 1995 |
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DE |
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543400 |
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Mar 1977 |
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SU |
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554869 |
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May 1977 |
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SU |
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Other References
Wickramasinghe et al, "Mass transfer in various hollow fiber
geometrics", Journal of Membrane Science, 69 (1992) pp. 235-250.
.
Yang et al, "Artifical Gills", Journal of Membrane Science, 42
(1989) pp. 273-284. .
Wickramasingle, et al, "Hollow Fiber Modules Made With Hollow Fiber
Fabric", Undated Paper, pp. 1-21. .
Belter et al, "Bioseparations: Downstream Processing for
Biotechnology", A Wiley-Interscience Publication, Chapter 9
(Ultrafiltration and Electrophoresis), (1986), pp. 237-270. .
Treybal, Mass-Transfer Operations, Third Edition, McGraw-Hill Book
Company, (1980), pp. 47-54, 74-75. .
Cussler, Diffusion: Mass transfer in fluid systems, Cambridge
University Press, 1984, Chapter 2,, pp. 15-54 and Chapter 9, pp.
215-248. .
Winston, et al, Membrane Handbook, Prasad et al, Membrane-Based
Solvent Extraction, (1992) Chapter 41, pp. 727-763. .
Bird et al, Transport Phenomena, Wiley, 1980, Sections 2.3,6.2,
6.4. .
Cussler, A Mass Transfer Tutorial, Chemtech, (Jul., 1986), pp.
422-425. .
Semmens et al, Ammonia Removal From Water Using Microporous Hollow
Fibers, undated paper, pp. 1-21. .
Yang et al, Designing Hollow-Fiber Contactors, AlChE. Journal,
(Nov. 1986), vol. 32, No. 11, pp. 1910-1916..
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Primary Examiner: Bhat; Nina
Attorney, Agent or Firm: Workman, Nydegger, Seeley
Parent Case Text
This is a continuation of application Ser. No. 08/263,817, filed on
Jun. 22, 1994, now abandoned which is a divisional of application
Ser. No. 08/115,996, filed on Sep. 2, 1993, now abandoned, which is
a continuation of application Ser. No. 07/844,620, now U.S. Pat.
No. 5,270,004 filed on May 11, 1992, .[.which claims priority to
PCT/US89/04314 filed Oct. 1, 1990.]. .Iadd.which is a national
stage application under 35 U.S.C. 371 of PCT/US89/04314, filed Oct.
1, 1989, .Iaddend.the entireties of which are hereby incorporated
by reference.
Claims
What is claimed is:
1. A combination heat exchanger and oxygenator device
comprising:
a housing including structure defining first and second
compartments, a blood inlet, a blood outlet, a heat exchange medium
inlet, a heat exchange medium outlet, an oxygenating fluid inlet
and an oxygenating fluid outlet, said housing having a central
axis, said second compartment being concentric to said axis;
structure defining a flow passage for blood through said housing
from said blood inlet to said blood outlet;
structure defining a flow passage for heat exchange medium from
said heat exchange medium inlet to said heat exchange medium
outlet;
structure defining a flow passage for oxygenating fluid from said
oxygenating fluid inlet to said oxygenating fluid outlet;
a plurality of hollow gas exchange tubes disposed in said second
compartment;
said blood flow passage comprising a heat exchange path through
said first compartment, said blood flow passage further comprising
a central path extending along at least a portion of said central
axis of said housing, said blood flow passage further comprising an
oxygenating path extending generally radially through said second
compartment, around said gas exchange tubes, said central path
being upstream of said oxygenating path, whereby blood flows
axially along at least a portion of the central axis of said
housing and then generally radially through said second
compartment.
2. The combination heat exchanger and oxygenator device of claim 1,
wherein said blood outlet has a central fluid flow axis disposed in
a plane substantially transverse to said central axis of said
housing.
3. The combination heat exchanger and oxygenator device of claim 1,
wherein said oxygenating fluid inlet and oxygenating fluid outlet
respectively comprise a gas inlet and a gas outlet.
4. The combination heat exchanger and oxygenator device of claim 1,
wherein said heat exchange path extends generally radially through
said first compartment.
5. The combination heat exchanger and oxygenator device of claim 1,
wherein said central path is upstream of said heat exchange
path.
6. The combination heat exchanger and oxygenator device of claim 1,
wherein said heat exchange path is upstream of said oxygenating
path.
7. The combination heat exchanger and oxygenator device of claim 1,
wherein said first and second compartments are concentric.
8. The combination heat exchanger and oxygenator device of claim 1
wherein said plurality of hollow gas exchange tubes disposed in
said second compartment are comprised of hollow gas exchange tubes
generally longitudinally disposed within said .[.first.].
.Iadd.second .Iaddend.compartment.
9. The combination heat exchanger and oxygenator device of claim 1
wherein said plurality of hollow gas exchange tubes disposed in
said second compartment are comprised of hollow gas exchange tubes
that are spirally
wound in concentric layers extending generally longitudinally.
10. The combination heat exchanger and oxygenator device of claim 1
wherein said first compartment is upstream of said second
compartment.
11. The combination heat exchanger and oxygenator device of claim 1
wherein said structure defining a flow passage for heat exchange
medium from said heat exchange medium inlet to said heat exchange
medium outlet includes a plurality of hollow heat exchange tubes
disposed in said first compartment.
12. The combination heat exchanger and oxygenator device of claim
11, wherein said heat exchange path is defined around said heat
exchange tubes and said heat exchange medium flows through said
heat exchange tubes.
13. The combination heat exchanger and oxygenator device of claim
11, wherein said blood flow passage extends axially of said first
compartment, via said central path, and then radially through said
first compartment, around said heat exchange tubes, via said heat
exchange path, and then radially through said second compartment,
around said gas exchange tubes, via said oxygenating path.
14. The combination heat exchanger and oxygenator device of claim
11 wherein said plurality of hollow heat exchange tubes disposed in
said first compartment are comprised of heat exchange tubes
generally longitudinally disposed within said first
compartment.
15. The combination heat exchanger and oxygenator device of claim
1, wherein said blood flow passage extends axially of said first
compartment, via said central path, and then radially through said
first compartment, via said heat exchange path, and then radially
through said second compartment, via said oxygenating path.
.Iadd.16. The combination heat exchanger and oxygenator device of
claim 1, wherein said housing is constructed and arranged and said
flow passage for blood is defined such that blood flows vertically
upwardly along at least a portion of the central path.
.Iaddend..Iadd.17. A combination heat exchange and oxygenator
device comprising:
a housing including first and second compartments, a blood inlet, a
blood outlet, a heat exchange medium inlet, a heat exchange medium
outlet, an oxygenating fluid inlet, an oxygenating fluid outlet,
said housing having a central axis, said second compartment being
concentric to said axis, wherein the first and second compartments
are concentric along at least a substantial portion of their
length;
a flow passage for blood through said housing from said blood inlet
to said blood outlet;
a flow passage for heat exchange medium from said heat exchange
medium inlet to said heat exchange medium outlet;
a flow passage for oxygenating fluid from said oxygenating fluid
inlet to said oxygenating fluid outlet;
a plurality of hollow gas exchange tubes disposed in said second
compartment;
said blood flow passage comprising a heat exchange path through
said first compartment and an oxygenating path extending generally
radially through said second compartment, around said gas exchange
tubes, at least a portion of said blood flow passage including a
generally central path generally parallel to said central axis of
said housing, said central path being upstream of said oxygenating
path, whereby blood in said central path flows in a direction
generally parallel to the central axis of the housing and then
generally radially through said second compartment.
.Iaddend..Iadd.18. The combination heat exchanger and oxygenator
device of claim 17, wherein said central path is upstream of said
heat exchange path. .Iaddend..Iadd.19. The combination heat
exchanger and oxygenator device of claim 17, comprising a tubular
wall member defining said central path. .Iaddend..Iadd.20. The
combination heat exchanger and oxygenator device of claim 19,
wherein said tubular wall member is porous.
.Iaddend..Iadd.21. A blood heater and oxygenating device for
heating and then oxygenating a patient's blood, and which is
designed to reduce priming volume required by the device,
comprising:
a housing including first and second compartments internal to the
housing, a blood inlet, a blood outlet, a heat exchange medium
inlet, a heat exchange medium outlet, an oxygenating fluid inlet
and an oxygenating fluid outlet, said housing having a central
axis, said second compartment being concentric to said axis and
including a plurality of hollow gas exchange tubes contained
therein;
said housing including a blood flow passage entirely internal to
said housing and extending from said blood inlet to said blood
outlet thereof;
a heat exchange medium flow passage internal to said housing,
connected to and extending between said heat exchange medium inlet
and said heat exchange medium outlet, whereby heat exchange medium
may be introduced into said heat exchange medium flow passage
through the heat exchange medium inlet and circulated out of said
heat exchange medium flow passage through said heat exchange medium
outlet;
an oxygenating fluid flow passage internal to said housing,
connected to and extending between said oxygenation fluid inlet and
said oxygenating fluid outlet, whereby an oxygenating fluid may be
introduced into said hollow tubes through said oxygenating fluid
inlet, and circulated out of and away from said hollow tubes
through said oxygenating fluid outlet;
said blood inlet connected to said first compartment so that the
blood diffuses directly from said blood inlet into said first
compartment without significant collection of the blood between
said blood inlet and said first compartment, and the blood being
heated as it passes through said first compartment; and
said blood flow passage comprising a heat exchange path through
said first compartment, said blood flow passage further comprising
a central path extending along at least a portion of said central
axis of said housing, said blood flow passage further comprising an
oxygenating path extending generally radially through said second
compartment, and around said hollow gas exchange tubes, and said
central path being upstream of said oxygenating path, whereby blood
flows axially along at least a portion of the central axis of said
housing and then generally radially through said
second compartment. .Iaddend..Iadd.22. The device of claim 21,
wherein said blood outlet has a central fluid flow axis disposed in
a plane substantially transverse to said central axis of said
housing. .Iaddend..Iadd.23. The device of claim 21, wherein said
oxygenating fluid inlet and oxygenating fluid outlet respectively
comprise a gas inlet and a gas outlet. .Iaddend..Iadd.24. The
device of claim 21, wherein said first and second compartments are
cylindrical. .Iaddend..Iadd.25. The device of claim 21 wherein said
plurality of hollow gas exchange tubes disposed in said second
compartment are comprised of hollow gas exchange tubes that are
spirally wound around said central axis. .Iaddend..Iadd.26. The
device of claims 21 or 24 wherein said first compartment is
upstream of said second compartment. .Iaddend..Iadd.27. The device
of claim 21 wherein said housing is constructed and arranged and
said flow passage for blood is defined such that blood flows in a
vertically upward direction along at
least a portion of said central path. .Iaddend..Iadd.28. A blood
heater and oxygenating device for heating and then oxygenating a
patient's blood, and which is designed to reduce priming volume
required by the device, comprising:
a housing including first and second compartments internal to the
housing, a blood inlet, a blood outlet, a heat exchange medium
inlet, a heat exchange medium outlet, an oxygenating fluid inlet
and an oxygenating fluid outlet, said housing having a central
axis, said second compartment being concentric to said axis and
including a plurality of hollow gas exchange tubes contained
therein;
said housing including a blood flow passage entirely internal to
said housing and extending from said blood inlet to said blood
outlet thereof;
a heat exchange medium flow passage internal to said housing,
connected to and extending between said heat exchange medium inlet
and said heat exchange medium outlet, whereby heat exchange medium
may be introduced into said heat exchange medium flow passage
through the heat exchange medium inlet and circulated out of said
heat exchange medium flow passage through said heat exchange medium
outlet;
an oxygenating fluid flow passage internal to said housing,
connected to and extending between said oxygenation fluid inlet and
said oxygenating fluid outlet, whereby an oxygenating fluid may be
introduced into said hollow tubes through said oxygenating fluid
inlet, and circulated out of and away from said hollow tubes
through said oxygenating fluid outlet;
said blood inlet connected to a chamber which is porous throughout
so that the blood diffuses directly into said first compartment
without significant collection of the blood in said chamber, and
the blood being heated as it passes through said first compartment;
and
said blood flow passage comprising a heat exchange path through
said first compartment, said blood flow passage further comprising
a central path extending along at least a portion of said central
axis of said housing, said blood flow passage further comprising an
oxygenating path extending generally radially through said second
compartment, and around said hollow gas exchange tubes, and said
central path being upstream of said oxygenating path, whereby blood
flows axially along at least a portion of the central axis of said
housing and then generally radially through said second
compartment. .Iaddend..Iadd.29. The device of claim 28, wherein
said blood outlet has a central fluid flow axis disposed in a plane
substantially transverse to said central axis of said housing.
.Iaddend..Iadd.30. The device of claim 28, wherein said oxygenating
fluid inlet and oxygenating fluid outlet respectively comprise a
gas inlet and a gas outlet. .Iaddend..Iadd.31. The device of claim
28, wherein said first and second compartments are cylindrical.
.Iaddend..Iadd.32. The device of claim 28 wherein said plurality of
hollow gas exchange tubes disposed in said second compartment are
comprised of hollow gas exchange tubes that are spirally wound
around said central axis. .Iaddend..Iadd.33. The device of claims
28 or 31 wherein said first compartment is upstream of said second
compartment. .Iaddend..Iadd.34. The device of claim 28 wherein said
housing is constructed and arranged and said flow passage for blood
is defined such that blood flows in a vertically upward direction
along at
least a portion of said central path. .Iaddend..Iadd.35. A blood
heater and oxygenating device for heating and then oxygenating a
patient's blood, and which is designed to reduce priming volume
required by the device, comprising:
a housing including first and second compartments internal to the
housing, a blood inlet, a blood outlet, a heat exchange medium
inlet, a heat exchange medium outlet, an oxygenating fluid inlet
and an oxygenating fluid outlet, said housing having a central
axis, said second compartment being concentric to said axis and
including a plurality of hollow gas exchange tubes contained
therein;
said housing including a blood flow passage entirely internal to
said housing and extending from said blood inlet to said blood
outlet thereof;
a heat exchange medium flow passage internal to said housing,
connected to and extending between said heat exchange medium inlet
and said heat exchange medium outlet, whereby heat exchange medium
may be introduced into said heat exchange medium flow passage
through the heat exchange medium inlet and circulated out of said
heat exchange medium flow passage through said heat exchange medium
outlet;
an oxygenating fluid flow passage internal to said housing,
connected to and extending between said oxygenation fluid inlet and
said oxygenating fluid outlet, whereby an oxygenating fluid may be
introduced into said hollow tubes through said oxygenating fluid
inlet, and circulated out of and away from said hollow tubes
through said oxygenating fluid outlet;
said blood inlet connected to a chamber and from which blood
diffuses directly into said first compartment along substantially
the entire length of said chamber without significant collection of
the blood in said chamber, and the blood being heated as it passes
through said first compartment; and
said blood flow passage comprising a heat exchange path through
said first compartment, said blood flow passage further comprising
a central path extending along at least a portion of said central
axis of said housing, said blood flow passage further comprising an
oxygenating path extending generally radially through said second
compartment, and around said hollow gas exchange tubes, and said
central path being upstream of said oxygenating path, whereby blood
flows axially along at least a portion of the central axis of said
housing and then generally radially through said second
compartment. .Iaddend..Iadd.36. The device of claim 35, wherein
said blood outlet has a central fluid flow axis disposed in a plane
substantially transverse to said central axis of said housing.
.Iaddend..Iadd.37. The device of claim 35, wherein said oxygenating
fluid inlet and oxygenating fluid outlet respectively comprise a
gas inlet and a gas outlet. .Iaddend..Iadd.38. The device of claim
35, wherein said first and second compartments are cylindrical.
.Iaddend..Iadd.39. The device of claim 35, wherein said plurality
of hollow gas exchange tubes disposed in said second compartment
are comprised of hollow gas exchange tubes that are spirally wound
around said central axis. .Iaddend..Iadd.40. The device of claims
35 or 38 wherein said first compartment is upstream of said second
compartment. .Iaddend..Iadd.41. The device of claim 35 wherein said
housing is constructed and arranged and said flow passage for blood
is defined such that blood flows in a vertically upward direction
along at
least a portion of said central path. .Iaddend..Iadd.42. A
combination heat exchanger and oxygenator device comprising:
a housing including first and second compartments internal to the
housing, a blood inlet, a blood outlet, a heat exchange medium
inlet, a heat exchange medium outlet, an oxygenating fluid inlet
and an oxygenating fluid outlet, said housing having a central
axis, said second compartment being concentric to said axis;
a blood flow passage entirely internal to said housing extending
through said housing from said blood inlet to said blood
outlet;
a heat exchange medium flow passage connected to and extending from
said heat exchange medium inlet to said heat exchange medium
outlet;
an oxygenating fluid flow passage connected to and extending from
said oxygenating fluid inlet to said oxygenating fluid outlet;
a plurality of hollow gas exchange tubes disposed in said second
compartment; and
said blood flow passage comprising a heat exchange path through
said first compartment, said blood flow passage further comprising
a central path extending along at least a portion of said central
axis of said housing, said blood flow passage further comprising an
oxygenating path extending generally radially through said second
compartment, and around said hollow gas exchange tubes, said
central path being upstream of said oxygenating path, whereby blood
flows axially along at least a portion of the central axis of said
housing and then generally radially through said second
compartment. .Iaddend..Iadd.43. The device of claim 42, wherein
said blood outlet has a central fluid flow axis disposed in a plane
substantially
transverse to said central axis of said housing. .Iaddend..Iadd.44.
The device of claim 42, wherein said oxygenating fluid inlet and
oxygenating fluid outlet respectively comprise a gas inlet and a
gas outlet. .Iaddend..Iadd.45. The device of claim 42, wherein said
first and second compartments are cylindrical. .Iaddend..Iadd.46.
The device of claim 42 wherein said plurality of hollow gas
exchange tubes disposed in said second compartment are comprised of
hollow gas exchange tubes that are spirally wound around said
central axis. .Iaddend..Iadd.47. The device of claims 42 or 45
wherein said first compartment is upstream of said second
compartment. .Iaddend..Iadd.48. The device of claim 42 wherein said
housing is constructed and arranged and said flow passage for blood
is defined such that blood flows in a vertically upward direction
along at least a portion of said central path. .Iaddend.
Description
FIELD OF THE INVENTION
This invention relates to a blood oxygenator having an integral
heat exchanging unit, the oxygenator being of the outside perfusion
type.
BACKGROUND OF THE INVENTION
Blood Oxygenators
In known blood oxygenators, hollow fibers are used as a means to
bring blood into contact with oxygen and provide a means for
removal of carbon dioxide from the blood. The fibers are typically
made of a homogeneous membrane of gas-permeable material such as
silicone or of hollow fibers made of a microporous membrane of
hydrophobic polymeric material such as polyolefins.
There are two types of hollow fiber blood oxygenators: the inside
perfusion type in which blood is passed through the bores of the
hollow fibers while oxygen is passed on the outside of the hollow
fibers, and the outside perfusion type. Blood oxygenators of the
outside perfusion type pass oxygen through the bores of the hollow
fibers while blood is flowed past the outside of the hollow
fibers.
Examples of inside perfusion type hollow-fiber oxygenators are
disclosed in U.S. Pat. Nos. 4,239,729 and 4,749,551.
In blood oxygenators of the outside perfusion type the oxygen can
be distributed uniformly through the spaces between adjacent fibers
and the blood can be expected to move with better mixing. However,
outside perfusion has had the disadvantage of being subject to less
than the desired oxygenation of the blood because of region
channeling of the blood as it passes the outsides of the hollow
fibers. Blood-side convective mixing is essential for efficient gas
transfer in blood oxygenators. Without such mixing, sharply defined
boundary layers of fully oxygenated blood develop near the exchange
surfaces and the fluxes of oxygen and carbon dioxide tend to be
low. Low transport efficiency results in bulky devices with
undesirable high blood priming volumes.
Outside perfusion type blood oxygenators are known in which the
hollow fibers are in perpendicular orientation to the direction of
blood flow so as to produce more mixing of the blood as the blood
flows than inside perfusion constructions. This arrangement can
bring about an improvement in oxygenation rate. However, if the
number of fibers used in such a blood oxygenator is large (as is
desirable) and/or the flow rate of blood is increased in order to
treat large volumes of blood, problems arise. For example,
unacceptable pressure drop of the blood between inlet and outlets
and/or channeling of the blood between groups of fibers may occur.
By channeling it is to be understood that a significant flow of
blood takes place through relatively large area voids between
fibers so that there is little or no mixing. As the rate of oxygen
transfer primarily takes place in a thin boundary layer adjacent
the hollow fibers, the effectiveness of desired oxygenation is
reduced.
Examples of blood oxygenators of the outside perfusion type are
disclosed in copending application PCT/US89/00146 filed Jan. 13,
1989; WO 89/00864; and U.S. Pat. Nos. 3,794,468; 4,352,736;
4,622,206; 4,659,549; 4,639,353; 4,620,965; 4,791,054; and
4,808,378, all incorporated herein by reference.
Combined Oxygenator and Heat Exchanger Devices
In the prior art it has been recognized that there is considerable
heat loss in all extracorporeal circuits and various devices have
been introduced for the purpose of maintaining the temperature of
blood within the normal physiological range. Devices which combine
the function of blood heating and oxygenation are known. U.S. Pat.
No. 4,111,659 describes an embossed film membrane
heater/oxygenator. U.S. Pat. No. 4,138,288 describes a bubble-type
oxygenator with an integral heater at the blood outlet side of the
oxygenator. U.S. Pat. No. 4,620,965 describes an outside perfusion
type hollow fiber blood oxygenator with an associated heat
exchanger, also located on the blood outlet side of the device, in
which the blood flows longitudinally through the oxygenator portion
of the device and generally parallel to the hollow gas exchange
fibers. U.S. Pat. Nos. 4,639,353, 4,659,549 and 4,791,054 also
disclose outside perfusion type hollow-fiber oxygenators in which
blood flowing longitudinally through a generally rectangular or
cylindrical device passes through multiple hollow fiber exchange
chambers separated by narrow channel baffles. In some embodiments
of the latter device, separate heat and Oxygen exchange chambers
are provided.
U.S. Pat. No. 4,645,645 describes a hollow-fiber blood oxygenator
to which a helical heat exchanger may be attached. Heat exchange is
accomplished by passing blood across the outside of a helical
coated metal coil.
U.S. Pat. No. 4,424,910 describes another form of hollow-fiber
oxygenator with an attached heater compartment displaced
longitudinally on a generally cylindrical device.
A problem with prior blood oxygenator/heater combination devices
which has been recognized in the prior art is the considerable
bulk, with consequent large priming volume of the combined devices.
A flat device is described in WO 89/00864 and co-pending
application, PCT/US89/00146 filed Jan. 13, 1989, which locates
heated exchange fibers and gas exchange fibers in adjacent
compartments separated by a porous wall so as to eliminate
collection and distribution manifolds between the devices. Such
flat devices, however, are difficult to manufacture because of the
difficulty of properly packing the gas exchange fibers for optimal
efficiency.
SUMMARY OF THE INVENTION
The present invention pertains to a novel compact integrated blood
heater/oxygenator in which the blood advantageously flows
transversely to the axial direction of hollow heat exchange and
oxygenation fibers, the device having a minimal priming volume and
which is easily assembled using conventional fiber winding
techniques for packing the gas exchange fibers.
The inventive blood heater oxygenator is a generally cylindrical
device which is constructed so that the blood enters a central
chamber extending longitudinally along the axis of the device and
then moves radially through respective annular hollow heat exchange
and oxygenation fiber bundles in a direction generally
perpendicular to the axis of the device and generally transverse to
the axial direction of the fibers toward the outer wall of the
device where the temperature adjusted and oxygenated blood is
collected and passed out of the device via an exit port.
DESCRIPTION OF THE FIGURES
FIG. 1 is a side perspective view of a blood heat
exchanger/oxygenator of the invention.
FIG. 2 is a side plan view with parts cut away of the heat
exchanger/oxygenator of FIG. 1.
FIG. 3 shows a sectional view of the heat exchanger/oxygenator of
the invention taken along line 3--3 of FIG. 2.
FIG. 4 is a side view of a portion of the device as seen from line
4--4 of FIG. 3.
FIG. 5 is an enlarged perspective view of the portion of FIG. 2
indicated by the bold numeral 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention is best described by reference to the preferred
embodiment as illustrated in FIGS. 1-5.
The preferred heat exchanger/oxygenator device of the invention is
generally designated in the figures by the numeral 10. The exterior
of device 10 comprises a generally cylindrical exterior wall
portion 12, proximal cover member 14 and distal cover member 20.
The distal cover 20 includes a central blood inlet port 26, a
heating fluid outlet port 28 and a gas outlet port 30.
The proximal cap 14 includes a blood outlet port 32, a heater
exchange fluid inlet port 36 and a gas inlet port 38. Raised
circular portions 40 and 42 define heat exchange fluid and gas
distribution manifolds, respectively, which provide fluid
communication between the respective inlet ports 36 and 38 and
respective hollow bundles of heat exchange and gas exchange fibers,
respectively, within the device. A raised circular portion 44
defines a blood collecting manifold which, as shown in FIG. 1,
increases in dimension as it approaches the exit port 32.
On the distal cover 16 there are also included raised circular
portions 46 and 48 which define manifolds for collecting and
directing heat exchange fluid and oxygenation gas from the fiber
bundles to their respective outlet ports.
The interior of the device includes a series of annular cylindrical
chambers 50, 54, 58 and 62 separated by tubular porous wall members
52, 56 and 60.
The central chamber 50 communicates with blood inlet port 26. The
next outward annular chamber 54 comprises the heat exchanger
portion of the device and is filled with heat exchange tubes 70 of
known type which extend generally in an axial direction. Annular
chamber 58 comprises the oxygenator portion of the device and is
filled with tubes 74 of a gas exchange membrane material, also of
known type. The gas exchange tubes 74 are also preferably oriented
generally in an axial direction. Between the porous wall 60 and the
inner surface of the outer wall 12 of the device is a hollow
cylindrical blood collection chamber 62.
The tubular porous walls 52, 56, 60, the heat exchange tubes 70,
and gas exchange tubes 74 are all potted together with a
conventional potting material 76 which holds the various interior
components of the device together as a unit and isolates the open
ends of the tubes 70 and 74 from the blood flow path.
The respective bundles of heat exchange and gas exchange fibers are
desirably simultaneously end potted so as to produce a unitary
assembly which can be readily sheared to produce open tube ends as
best shown in FIG. 5. The covers 14 and 16 are aligned so that they
sealingly engage the potted assembly between the respective fiber
bundles. Suitably the porous tubular wall members 52, 56 and 60 are
provided with continuous non-porous end portions 80 entrained in
the potting material such that when the potted assembly is sheared
the end portions 80 expose continuous annular rings which provide
sealing surface to engage the covers and isolate the respective gas
blood and heating fluid distribution and collection manifolds, as
shown in FIGS. 2 and 5. Most preferably the cover assemblies are
heat or sonically welded to the end portions 80 and to the ends of
outer cylindrical wall 12.
The tubular porous wall members 52, 56 and 60 provide separation
between the chambers while allowing blood to pass therethrough
without offering substantial resistance or directional change. Any
porous structure which allows the passage of blood without
significant damage may be used. However, it is preferred that these
wall members be constructed of a biocompatible plastic material
containing a plurality of spaced orifices 82. The orifices 82 are
preferably no greater than 1/2 inch (1.27 cm) and preferably 3/8
inches (0.95 cm) in diameter. Larger diameter orifices will allow
the fibers to bulge into the orifices and thereby potentially
create void spots in the fiber bundle therebelow. Another
disadvantage in fibers bulging into the orifices is that pinching
to close a fiber may occur. Smaller diameter orifices may be used,
by spacing must be selected so that the total area of the orifices
82 is sufficient to assure that the respective porous tubular wall
members do not themselves create significant resistance to blood
flow or dead spots where blood may collect and coagulate.
Suitable gas exchange membrane material for fibers 74 may be made
of polypropylene, polyethylene or other biocompatible material
which provides gas exchange. The fibers are liquid impermeable.
Suitable fibers for this purpose are well known and commercially
available from a number of manufacturers including Mitsubishi Rayon
Sale, Ltd. of Tokyo, Japan and Celanese Chemical Company of New
York, N.Y., U.S.A.
The heat exchange tubes 70 are preferably formed from a
polyurethane resin such as B. F. Goodrich Estane 58091. The tubes
are much larger than the hollow fibers in the oxygenator, typically
being about 0.033 inches (840 microns) in outside diameter with a
wall thickness of about 0.004 inches (102 microns). In contrast, a
typical oxygenator fiber has an outside diameter of about 200-450
microns and a wall thickness of less than 50 microns. The formation
of heat exchanger tubes from polyurethane rather than the stainless
steel, polyethylene, or polypropylene is preferred. While the
efficiency of the heat exchange it an important design
consideration, it is vital that there must be no leakage. The end
seals where polyurethane potting compounds are used with stainless
steel tubes represent potential leakage areas of the cooling fluid
into the blood.
The use of polyurethane heat exchange tubes with the polyurethane
end potting compounds provides a positive seal which ensures that
no leakage will occur. This compatibility with the potting compound
greatly increases the safety of the product.
The hollow heat exchange tubes are packed into chamber 70 such that
channeling is minimized. However, performance of the heat exchanger
is not greatly affected if some channeling is present. A pack
density of between about 40% and 60% provides an efficient heat
exchanger with an accept&hie pressure drop. It is preferred to
pack the polyurethane tubes at about 45%-55% pack density which
provides an efficient unit, low pressure drop and low blood priming
volume. The thin walled polyurethane hollow tubes provide good heat
transfer. The efficiency desired is in ensuring that all of the
blood is heated or cooled as desired, not in how much heat exchange
fluid is required. The temperature differential between the blood
and heat exchange fluid should be low to provide better
control.
In the preferred embodiment the overall size of the unit is
approximately 5 inches (12.5 cm) in diameter by 7.5 inches (18.75
cm) long. The heat exchange tubes are polymeric tubes having an
approximate diameter of 0.033 inches (0.83 mm or 830 .mu.), and the
heat exchange chamber containing approximately 2750 tubes. The gas
exchange fibers suitably are microporous hollow polypropylene
membrane is sufficient quantity to provide a total blood contact
surface area of approximately 3.8 square meters. The device permits
an outlet blood oxygen tension of 150 torr or more, tested on
bovine blood with a hemoglobin concentration of 12 gram-percent;
with an inlet saturation of 55% a blood flow of 6 liters per minute
and an oxygen flow of 6 liters per minute. The heat exchanger
provides an effectiveness level of 45% as measured by the protocol
of the American Association of Medical Instrumentation (AAMI).
The heat exchange tubes are preferably cut to length and then
placed into the chamber 52. Winding the tubes about central core 52
is less preferable as it tends to cause the hollow tubes to bend
and may cause cracks or breaks.
The gas exchange fiber bundle is most suitably prepared by spiral
winding fibers 74 around the tubular wall member 56, successive
layers being angled relative to each other to produce a crisscross
pattern. The crossing fiber arrangement is preferred over parallel
fiber packing since it forces the blood into effective but gentle
transverse, mixing without traumatizing the blood. Winding
techniques for producing cylindrical bundles of hollow fibers are
well known and are described in such references as U.S. Pat. No.
3,755,034, 3,794,468, 4,224,094, 4,336,138, 4,368,124 and
4,430,219, all incorporated herein by reference. The preferred
angle between the fibers of successive layers is in the range of
between about 10.degree. and 30.degree., more preferably between
about 15.degree. and 20.degree., most preferably 18.degree.. The
fibers run in a generally axial direction, so that an axial plane
bisects the angle between the successive layers of the fibers. For
instance, in the most preferred embodiment, one layer will deviate
from the axial direction by +9.degree. and the next layer will
deviate from the axial direction by -9.degree.. The pack density of
the gas exchange fibers 74 should be between about 45% and 60%,
most preferably about 50% and 55%. When the pack density is too
high the resulting resistance to blood flow reduces oxygenation
efficiency. Likewise, when the pack density is too low channeling
and reduced turbulent flow of the blood also reduces oxygenation
efficiency. Within the preferred range oxygenation efficiency is
maximized.
For potting the ends of the assembly of fiber bundles and porous
wall members 52, 56 and 60, a polyurethane potting compound is
preferred. Suitable potting compounds are available from Caschem,
Inc. of Bayonne, N.J., U.S.A. A polyurethane casting system of
Caschem, Inc. is described in U.S. Pat. Reissue No. 31,389. After
potting the hollow fibers are reopened by conventional techniques
such as shearing the potting with a sharp knife so as to expose the
interiors of the fibers.
After insertion of the potted and sheared assembly into cylinder 12
the cover members 14 and 20 are inserted in line so that they
sealingly engage the potted assembly between the respective fiber
bundles.
The covers 14 and 20, cylinder case 12 and the porous tubular wall
members 52, 56 and 60 are all preferably made from nontoxic
biocompatible plastic resins. Suitable resins are polycarbonate
resins such as the Lexan brand resins of General Electric Company,
Polymer Product Department, Pittsfield, Mass. Lexan 144 grade
polycarbonate resins are currently preferred.
In operation, blood entering the device through the central inlet
port 26, fills chamber 50 and then passes in a direction generally
perpendicular to the axis through porous wall 52, around heat
exchange fibers 70, through porous wall 56, around gas exchange
fibers 74, through wall 60, into collection chamber 62 and then up
into the blood collecting manifold 44 in cover 14, finally exiting
the device via blood exit port 32.
An advantage provided by the compact structure of the device is a
reduction in priming volume which results because blood is directly
passed from the heat exchange chamber 54 to the oxygenation chamber
58 without passing through intermediate collection and distribution
manifolds.
Yet another advantage of the invention compared to many of the
prior art devices described in the Background section, above, is
the location of the heat exchange chamber upstream from the gas
exchange chamber. Since gas solubility varies significantly with
temperature, it is important that the blood is oxygenated at the
temperature it will enter the body. If the blood is heated after it
is oxygenated, the oxygenation level may exceed the gas saturation
point at the higher temperature, resulting in formation of
dangerous emboli. If blood is cooled after oxygenation inefficient
oxygenation can result.
Compared to the rectangular devices of WO 89/0864 and
PCT/US89/00146, the device of the present invention also provides a
significantly less complicated device to manufacture. In
particular, to obtain the desired angular and Offset orientation of
the gas exchange fibers in the prior art rectangular device it was
necessary to employ a manufacturing technique which not only laid
alternate layers in a crisscross pattern angled with respect to
each other approximately 18', but also required offsetting each
successive parallel layer to minimize channeling. In the
cylindrical device of the invention the desired crisscrossing of
successive layers can readily be performed by conventional spiral
winding techniques and the increasing diameter of the winding
naturally results in an offset of successive parallel layers
without complex controls.
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