U.S. patent application number 13/084100 was filed with the patent office on 2014-03-06 for paracorporeal respiratory assist lung.
This patent application is currently assigned to UNIVERSITY OF PITTSBURGH-OF THE COMMONWEALTH SYSTEM OF HIGHER EDUCATION. The applicant listed for this patent is William J. FEDERSPIEL, Brian J. FRANKOWSKI, Brendan C. MACK, Scott W. MORLEY, Meir ROSENBERG, Robert G. SVITEK. Invention is credited to William J. FEDERSPIEL, Brian J. FRANKOWSKI, Brendan C. MACK, Scott W. MORLEY, Meir ROSENBERG, Robert G. SVITEK.
Application Number | 20140065016 13/084100 |
Document ID | / |
Family ID | 36738019 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140065016 |
Kind Code |
A1 |
FEDERSPIEL; William J. ; et
al. |
March 6, 2014 |
PARACORPOREAL RESPIRATORY ASSIST LUNG
Abstract
A paracorporeal respiratory assist lung is configured with an
annular cylindrical hollow fiber membrane (fiber bundle) that is
rotated at rapidly varying speeds. Fluid (for example, blood) is
introduced to the center of the device and is passed radially
through the fiber bundle. The bundle is rotated at rapidly changing
velocities with a rotational actuator (for example, a motor or
magnetic coupling). The rotation of the fiber bundle provides
centrifugal kinetic energy to the fluid giving the device pumping
capabilities and may create Taylor vortexes to increase mass
transfer. Rotation of the fiber bundle increases the relative
velocity between the fluid and the hollow fibers and increases the
mass transfer. The porosity of the fiber bundle may be varied to
enhance gas exchange with the blood. Alternatively, a rotating core
may be used with a stationary fiber bundle.
Inventors: |
FEDERSPIEL; William J.;
(Pittsburgh, PA) ; FRANKOWSKI; Brian J.;
(Imperial, CA) ; MACK; Brendan C.; (Pasadena,
CA) ; MORLEY; Scott W.; (Pittsburgh, PA) ;
ROSENBERG; Meir; (Newton, MA) ; SVITEK; Robert
G.; (Pittsburgh, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FEDERSPIEL; William J.
FRANKOWSKI; Brian J.
MACK; Brendan C.
MORLEY; Scott W.
ROSENBERG; Meir
SVITEK; Robert G. |
Pittsburgh
Imperial
Pasadena
Pittsburgh
Newton
Pittsburgh |
PA
CA
CA
PA
MA
PA |
US
US
US
US
US
US |
|
|
Assignee: |
UNIVERSITY OF PITTSBURGH-OF THE
COMMONWEALTH SYSTEM OF HIGHER EDUCATION
Pittsburgh
PA
|
Family ID: |
36738019 |
Appl. No.: |
13/084100 |
Filed: |
April 11, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11408650 |
Apr 21, 2006 |
7927544 |
|
|
13084100 |
|
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60688809 |
Jun 8, 2005 |
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60673885 |
Apr 21, 2005 |
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Current U.S.
Class: |
422/48 |
Current CPC
Class: |
A61M 2205/3334 20130101;
A61M 1/1006 20140204; A61M 1/1698 20130101; A61M 1/1086 20130101;
B01D 2313/10 20130101; A61M 1/1025 20140204; B01D 63/16 20130101;
A61M 1/267 20140204; A61M 1/265 20140204; B01D 63/02 20130101; A61M
1/101 20130101; A61M 1/1013 20140204 |
Class at
Publication: |
422/48 |
International
Class: |
A61M 1/16 20060101
A61M001/16 |
Goverment Interests
FEDERALLY SPONSORED RESEARCH
[0002] The U.S. Government has a paid-up license in this invention
and the right in limited circumstances to require the patent owner
to license others on reasonable terms as provided for by the terms
of Grant Nos. DAMD 17-02-1-0717 awarded by the Department of the
Army and Grant No. RO1 HL 70051 awarded by the National Institutes
of Health.
Claims
1. A paracorporeal respiratory assist lung, comprising: a housing
having a smooth inner cylindrical surface, a liquid inlet, a liquid
outlet, a gas inlet and a gas outlet; a plurality of tubular gas
permeable fiber membranes configured to form a cylindrical annular
fiber bundle, the annular fiber bundle being disposed within the
housing and connected to and in fluid communication with the gas
inlet and the gas outlet wherein gas is passed through the lumens
of the cylindrical annular fiber bundle, wherein a first annular
gap is configured between the housing and the fiber bundle; a
stationary cylindrical core with a smooth outer surface being
positioned concentrically within the annular fiber bundle, wherein
a second annular gap is configured between the smooth outer surface
the core and the annular fiber bundle; a stationary cylindrical
core with a smooth outer surface being positioned concentrically
within the annular fiber bundle, wherein a second annular gap is
configured between the smooth outer surface of the core and the
fibers of the annular fiber bundle; an impeller having the same
diameter as the core and in fluid communication with the liquid
inlet via a conduit within the core, the impeller fixed to the
interior of a lower portion of the annular fiber bundle; the
impeller comprised of a plurality of arcuate arms each culminating
in an exit port aligned with the smooth outer surface of the
stationary core and ending in the lower portion of the second
annular gap; and means for rotating the annular fiber bundle and
fixed impeller, wherein rotating the annular fiber bundle
cooperates with the smooth inner surface of the housing and the
first annular gap to create and maximize Taylor vortices within the
first annular gap; and wherein the housing, annular fiber bundle
and core are configured such that liquid traveling at a low flow
rate enters the liquid inlet, travels down the conduit through the
impeller which pumps the liquid in to the second annular gap and
radially through the tubular gas permeable hollow fiber membrane,
having the Taylor vortices cause the liquid to pass the back and
forth through the fiber bundle and the annular gaps to maximize gas
exchange, the liquid eventually exiting through the liquid
outlet.
2. (canceled)
3. (canceled)
4. The paracorporeal respiratory assist lung of claim 1, wherein
the fiber bundle is configured with a porosity that allows uniform
liquid flow though the fiber bundle; said porosity is determined by
the diameter of the hollow fiber membrane and by arrangement and
spacing between hollow fiber membranes.
5. (canceled)
6. The paracorporeal respiratory assist lung of claim 1, further
comprising means for varying a velocity of the rotation of the
fiber bundle.
7. The paracorporeal respiratory assist lung of claim 1, further
comprising means for oscillating a direction of the rotation of the
fiber bundle.
8. The paracorporeal respiratory assist lung of claim 1, further
comprising a dual lumen cannula configured for insertion into the
venous circulation of a patient to provide blood flow to the liquid
inlet of the housing and to accept blood flow from the liquid
outlet of the housing.
9-20. (canceled)
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This is a divisional application which is based on U.S. Ser.
No. 11/408,650, filed on Apr. 21, 2006, U.S. Pat. No. 7,927,544
with an issue date of Apr. 19, 2011; which claims priority from
U.S. Provisional Patent Application Ser. No. 60/673,885, filed Apr.
21, 2005 and U.S. Provisional Patent Application Ser. No.
60/688,809, filed Jun. 8, 2005, each of which are incorporated by
reference in their entirety.
BACKGROUND OF THE INVENTION
[0003] The present invention is directed to an improved veno-venous
extracorporeal oxygenator, referred to herein as a "paracorporeal
respiratory assist lung" or the "PRAL device." More specifically,
the paracorporeal respiratory assist lung includes a variable speed
(oscillating) rotating fiber bundle having increased porosity. In
addition, the PRAL device may be configured to rotate a core
wherein the fiber bundle is stationary, and may further be
configured to include a fiber bundle on the rotating core.
[0004] It has been reported that 350,000 Americans die of lung
disease each year, most from Acute Respiratory Distress Syndrome
(ARDS) and Chronic Obstructive Pulmonary Disease (COPD). The most
common treatment is mechanical ventilation, but may further
exacerbate respiratory insufficiency and can cause serious side
effects, such as barotrauma and volutrauma. It has been further
reported that heart-lung machines, which utilize oxygenators, are
employed during surgery throughout the world hundreds of thousands
of times per year. Such oxygenators may be useful in treating COPD
and ARDS. However, inefficient mass transfer (gas exchange) of
oxygen and carbon dioxide is a common problem in oxygenators used
in heart-lung machines.
[0005] The use of membrane oxygenators to oxygenate blood is well
known in the art. One type of conventional membrane oxygenator
employs bundles of hollow fibers retained within a cylindrical
housing wherein oxygen is pumped through the hollow fibers in the
same direction as the blood. The hollow fibers consist of a
microporous membrane which is impermeable to blood and permeable to
gas. Gas exchange takes place when venous blood flows through the
housing and contacts the hollow fibers. Based on the law of
diffusion, the oxygen diffuses across the hollow fiber walls and
enriches venous blood in contact with these hollow fibers. A stated
disadvantage to this type of membrane oxygenator is that a blood
boundary layer is formed around the hollow fibers which retards
oxygenation of blood that does not directly contact the hollow
fibers.
[0006] Another known type of membrane oxygenator includes moving a
portion of the oxygenator to provide increased mixing of blood
flow. In this type of membrane oxygenator, a blood flow path and an
oxygen flow path are positioned between a rotor and a stator and
separated by a membrane and a wafer. When the rotor rotates
relative to the stator, mixing of blood flow occurs resulting in
disruption of the blood boundary layer. Although such an oxygenator
provides a degree of mixing of blood, this mixing may cause
destruction of red blood cells. In one embodiment of such an
oxygenator, a cylindrical, semi-permeable membrane containing
oxygen is rotated in a housing such that blood contacts and flows
over the membrane and oxygen is transferred through the rotating
membrane to the blood. One reported problem with this type of
membrane oxygenator is the poor permeability to oxygen and carbon
dioxide of semi-permeable membranes.
[0007] Yet another known membrane oxygenator includes hollow fiber
membranes that extend substantially longitudinally, first inert
fibers are spaced between them and also extend substantially
longitudinally. Second inert fibers extend generally transverse to
the hollow fibers and generally contiguous therewith, so that an
oxygen-containing gas can pass through the hollow fibers and blood
can be passed over their exterior for gas exchange through the
membrane. The second inert fibers may form a weft and the first
inert fibers are spaced one between each two hollow fibers so that
the warp consists of alternating strands of hollow fiber and first
inert fiber passing over the weft in an oscillating fashion. The
inert fibers are disclosed as biocompatible monofilament polymers
that provide spacing of the hollow fibers to produce even blood
films. However, such an oxygenator is not designed for
extracorporeal applications having relatively low blood flow
rates.
[0008] Accordingly, there is a need for, and what was heretofore
unavailable, an extracorporeal oxygenator having enhanced gas
exchange characteristics resulting from a variable rotating fiber
bundle and/or increased porosity of the fiber bundle that has high
gas exchange efficiency with minimal damage to the blood
components.
SUMMARY OF THE INVENTION
[0009] The present invention is directed to an improved veno-venous
extracorporeal oxygenator, referred to herein as a "paracorporeal
respiratory assist lung." The veno-venous artificial lung may be
used as replacement therapy for mechanical ventilation for chronic
obstructive pulmonary disease (COPD) patients with high levels of
partial pressure of carbon dioxide (pCO.sub.2) in their blood. The
paracorporeal respiratory assist lung of the present invention
provides active mixing through rotation of a module containing
gas-permeable, hollow fibers (annular fiber bundle) for enhanced
gas exchange at constant flow rates of blood through the device.
Rotation of the fiber bundle is known to increase the gas exchange
efficiency of artificial lungs, for example, a two-hundred percent
increase in carbon dioxide (CO.sub.2) transfer efficiency. It has
been demonstrated that CO.sub.2 removal of 100-120 milliliters per
minute (ml/min) can be achieved with blood flow rates in the range
of 0.5 to 1.0 liters per minute (1/min). The rotating fiber bundle
provides self-pumping of blood through the device with pressure
heads below thirty millimeters of mercury (mmHg). It has been
demonstrated that self-pumping of blood through the device with
pressure heads that can be tailored to the application by altering
the diameter of the annular fiber bundle or the speed of rotation.
Prototypes with fiber bundle diameters up to 4 inches size have
generated pressure heads up to 100-300 mmHg. Accordingly, the
paracorporeal respiratory assist lung acts as an integrated
pump/hollow fiber membrane mass transport device.
[0010] One aspect of the improvements to the paracorporeal
respiratory assist lung according to the present invention includes
an annular cylindrical hollow fiber membrane device that is rotated
at rapidly varying speeds. Fluid is introduced to the center of the
device and is passed radially through the fiber bundle. The bundle
is rotated at rapidly changing velocities with a rotational
actuator (usually a motor). It has been demonstrated that the
present invention enhances mass transfer when the rotational
velocity of the fiber bundle is rapidly varied. For example,
oscillations are introduced in the steady rotation of a hollow
fiber bundle to increase the mass transfer efficiency of the device
while maintaining its pumping capabilities.
[0011] Another aspect of the improvements to the paracorporeal
respiratory assist lung according to the present invention includes
increasing the porosity in the rotating fiber bundle. The increased
porosity provides more fluid to flow through the fiber bundle, thus
increasing the overall mass transfer efficiency of the device. The
extra porosity in the fiber bundle is created by several possible
ways including, but not limited to, using spacers to create void
space between the fiber layers, removing every other fiber in the
mat and using smaller diameter fibers. Additionally, support
threads could be removed from the fiber fabric, and the
paracorporeal respiratory assist lung could be configured such that
the manifolds are relatively closer so as to "puff out" the fiber
bundle.
[0012] A further aspect of the present invention includes a
paracorporeal respiratory assist lung having the following
features: [0013] Paracorporeal veno-venous system with percutaneous
cannula [0014] Inserted in the venous circulation for blood flow
[0015] Self-pumping of blood flow driven by rotating fiber bundle
[0016] Removes CO.sub.2 and supplies O.sub.2 before blood reaches
the lungs [0017] Gas exchange at blood flow rates of less than one
liter per minute [0018] Rotating hollow fiber bundle for enhanced
gas exchange [0019] Rotating annular fiber bundle promotes
increased flow velocity past fiber surfaces [0020] Stationary core
and outer housing generate fluid shear on fiber bundle [0021] Blood
pathway allows rotating bundle to pump fluid [0022] Compact,
efficient hollow fiber module worn externally
[0023] Additional features of the paracorporeal respiratory assist
lung of the present invention include: [0024] Variable rotation
enhances gas exchange [0025] Variable porosity of the fiber bundle
[0026] Blood flows of 500-750 ml/min for respiratory support [0027]
Small dual-lumen cannula (14-16 French) [0028] Active surface area
of the fiber bundle is less than 0.50 square meters (m.sup.2)
[0029] CO.sub.2 removal of 100-120 ml/min at blood flow rate of 0.5
to 1.0 liters per minute [0030] CO.sub.2 removal independent of the
functional capacity of the natural lungs
[0031] One embodiment of the present invention includes a
paracorporeal respiratory assist lung having a housing having a
liquid inlet, a liquid outlet, a gas inlet and a gas outlet. The
PRAL device includes a plurality of tubular gas permeable fiber
membranes configured to form a fiber bundle, the fiber bundle being
disposed within the housing and connected to and in fluid
communication with the gas inlet and the gas outlet, wherein a
first gap is configured between the housing and the fiber bundle.
The device further includes a stationary core being disposed within
the fiber bundle, wherein a second gap is configured between the
core and the fiber bundle. The PRAL device may be configured for
rotating the fiber bundle, wherein the housing, fiber bundle and
core are configured such that liquid entering the liquid inlet
passes through the fiber bundle and into the liquid outlet.
[0032] An alternative embodiment of the paracorporeal respiratory
assist lung of the present invention includes a housing having a
liquid inlet, a liquid outlet, a gas inlet and a gas outlet. The
PRAL device includes a plurality of tubular gas permeable fiber
membranes configured to form a fiber bundle, the fiber bundle being
disposed within the housing and connected to and in fluid
communication with the gas inlet and the gas outlet, wherein a
first gap is configured between the housing and the fiber bundle.
The device is configured with a core being disposed within the
fiber bundle, wherein a second gap is configured between the core
and the fiber bundle. The device may include a mechanism for
rotating the core, wherein the housing, fiber bundle and core are
configured such that liquid entering the liquid inlet passes
through the fiber bundle and into the liquid outlet. The PRAL
device may further be configured for creating turbulent flow within
the second gap and creating a plurality of Taylor vortexes within
the second gap. In addition, the fiber bundle may be configured
with a porosity that allows uniform liquid flow though the fiber
bundle. Further, the PRAL device may be configured such that the
fist gap and the second gap are configured to optimize liquid flow
through the fiber bundle.
[0033] Other features and advantages of the invention will become
apparent from the following detailed description, taken in
conjunction with the accompanying drawings, which illustrate, by
way of example, the features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 depicts placement in vivo of the paracorporeal
respiratory assist lung of the present invention.
[0035] FIGS. 2A-2C depict several views of one embodiment of the
paracorporeal respiratory assist lung of the present invention.
[0036] FIGS. 3A-3D depict several views of an alternative
embodiment of the paracorporeal respiratory assist lung of the
present invention.
[0037] FIGS. 4A and 4B are schematic representations of the
paracorporeal respiratory assist lung of the present invention
showing a rotating bundle.
[0038] FIGS. 5A-5P depict several views of an alternative
embodiment of the paracorporeal respiratory assist lung of the
present invention.
[0039] FIG. 6 depicts an alternative embodiment of the
paracorporeal respiratory assist lung of the present invention.
[0040] FIG. 7 depicts an alternative embodiment of the
paracorporeal respiratory assist lung of the present invention.
[0041] FIGS. 8A-8D depict several views of an alternative
embodiment of the paracorporeal respiratory assist lung of the
present invention.
[0042] FIG. 9 depicts schematic view of an alternative embodiment
of the paracorporeal respiratory assist lung of the present
invention having a magnetic drive mechanism.
[0043] FIGS. 10A and 10B depict an alternative embodiment of the
paracorporeal respiratory assist lung of the present invention.
[0044] FIG. 11 is a cross-sectional view of the paracorporeal
respiratory assist lung of FIG. 10.
[0045] FIGS. 12A and 12B are schematic representations of the
paracorporeal respiratory assist lung of FIG. 11.
[0046] FIG. 13 depicts schematic view of an alternative embodiment
of the paracorporeal respiratory assist lung of the present
invention.
[0047] FIG. 14 is a block diagram of the system of the present
invention.
[0048] FIG. 15 depicts a cross-sectional view of an alternative
embodiment of the paracorporeal respiratory assist lung of the
present invention having a magnetic drive mechanism.
[0049] FIGS. 16A and 16B are cage mechanism in accordance with the
present invention for use with the fiber bundle.
[0050] FIGS. 17A, 17B depict schematic representations of a fiber
mat having spacers for use in the paracorporeal respiratory assist
lung of the present invention.
[0051] FIG. 18 is a block diagram in accordance with the system of
the present invention.
[0052] FIG. 19 is a block diagram in accordance with the system of
the present invention.
[0053] FIG. 20 is a graphical representation of gas exchange rates
achieved with an embodiment of a paracorporeal respiratory assist
lung of the present invention.
[0054] FIG. 21 is a graphical representation of gas exchange rates
achieved with an embodiment of a paracorporeal respiratory assist
lung of the present invention.
[0055] FIG. 22 is a graphical representation of blood flow
(pumping) achieved with an embodiment of a paracorporeal
respiratory assist lung of the present invention.
[0056] FIG. 23 is a graphical representation of a model prediction
based on the porosity of the fiber bundle.
[0057] FIGS. 24 and 25 are graphical representations of carbon
dioxide removal and blood flow (pumping) achieved with varied
porosity of the fiber bundle in the paracorporeal respiratory
assist lung of the present invention.
[0058] FIG. 26 is a graphical representation of the model (FEMLAB)
of blood flow through the fiber bundle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] The present invention is directed to an improved veno-venous
extracorporeal oxygenator, referred to herein as a "paracorporeal
respiratory assist lung" or "PRAL device." The paracorporeal
respiratory assist lung of the present invention includes a
rotating hollow fiber membrane bundle to increase the gas exchange
efficiency of the device by reducing the boundary layer phenomena
caused by blood flowing over the fibers. U.S. Pat. Nos. 5,830, 370
(Maloney et al.); 5,900,142 (Maloney et al.); 6,106,776 (Borovetz
et al.); 6,217,826 (Reeder et al.); 6,348,175 (Borovetz et al.);
6,723,284 (Reeder et al.) and U.S. Publication No. 2004/0219,061
(Reeder et al.) are incorporated herein in their entirety by
reference.
[0060] The paracorporeal respiratory assist lung of the present
invention has been developed for patients suffering from acute lung
failures and acute exacerbations of chronic lung diseases. The
design concept builds upon the clinical success of previous
oxygenators that remove blood from the femoral artery of the
patient, removes carbon dioxide (CO.sub.2) via a commercially
available membrane oxygenator and utilizes the natural
arterio-venous pressure gradient to direct the blood to the femoral
vein. The present invention uses an annular rotating hollow fiber
membrane bundle to increase gas exchange and enable the device to
pump blood. The increased gas exchange enables a lower surface area
than current commercially available membrane lungs, and the pumping
capacity of the rotating bundle enables blood flow through a
percutaneous dual lumen cannula inserted exclusively on the venous
circulation.
[0061] The main limitation to gas transfer in blood oxygenators is
the diffusional boundary layer created by fluid flow along the
surfaces of the fiber membranes. Effective movement of the fibers
relative to the fluid (blood) can help reduce this boundary layer.
In the invention described here, the hollow fibers of the
oxygenator are configured into an annular bundle that is rotated
about a central axis. The placement of the hollow fibers in an
annulus distinguishes this rotating oxygenator from known spinning
disk rotating oxygenators. In such an annular configuration, the
spinning of the fiber bundle provides a more uniform linear
velocity to the fibers because all the fibers are at comparable
distance from the axis of rotation. Accordingly, the paracorporeal
respiratory assist lung of the present invention can achieve a
given level of gas exchange at lower rotational speed than in
spinning disk type oxygenators.
[0062] The paracorporeal respiratory assist lung of the present
invention includes an outer housing that incases the fiber annulus,
a motor connected to a shaft that spins the fiber annulus, and
seals and bearings that separate the fluid and gas pathways. The
proximal and distal manifolds may be configured with mechanisms,
such as vanes, to aid in the mixing of fresh blood into the
spinning fiber bundle. The fluid (blood/water) flows through a
center pathway within the rotating shaft of the device that
supports the fibers. With the rotation of this fluid pathway/fiber
assembly, the fluid velocities that pass through the fibers and
exchange gas can be regulated by controlling the rotational rate of
the fiber bundle. With the fiber annulus of this device configured
to a set distance from the center of rotation, more consistent
velocities past the fibers are achieved, uniformly utilizing all
the fibers, unlike a disc type oxygenator that generates various
velocities along their surfaces.
[0063] The paracorporeal respiratory assist lung of the present
invention has distinct advantages over current rotational
technologies:
[0064] rotating annular fiber bundle instead of a stationary fiber
bundle;
[0065] rotating fiber bundle in annular shape instead of disk
(velocity does not go to zero near the axis of rotation);
[0066] rotation can be steady/unsteady (time varying increases mass
transfer and pumping at the mean steady value);
[0067] annulus can be fabricated over a range of porosities (higher
porosity leads to higher gas exchange without a significant effect
on pumping);
[0068] the annulus can be a thin bundle which leads to more shear
penetration from the stationary walls surrounding the bundle;
[0069] hemolysis is not due to the rotating fibers themselves (the
device is configured using a porous stainless steel cage for
support during rotation);
[0070] various technologies have been developed to vary the fiber
bundle porosity;
[0071] rotation of the fiber bundle appears to make the flow paths
more uniform so that gas exchange is not affected by the design or
location of the inflow/outflow ports;
[0072] pumping allows veno-venous percutaneous operation; and
[0073] levels of CO.sub.2 removal due to rotation of the fiber
bundle may enable respiratory dialysis or low-flow CO.sub.2
removal.
[0074] As shown in FIG. 1, a paracorporeal respiratory assist lung
(PRAL device) is configured with a motor drive 28 for positioning
outside of the body of a patient 25. The PRAL device includes a
blood flow catheter 21 that may be inserted into the femoral vein
27 of the patient. Alternatively, the PRAL blood catheter may be
inserted through the jugular vein 29 of the patient. The proximal
end 45 of the PRAL blood catheter 21 may be inserted through a cut
down 23 or percutaneous access in the leg of the patient for
placement into the femoral vein. The catheter is guided through the
patient's vasculature to a position proximate the patient's heart
such that the distal end 45 is close to the heart, for example in
or near the vena cava. The PRAL blood catheter may be configured
with a dual lumen having one side 47 for a blood inlet and a second
side 46 for a blood outlet. It may be advantageous to notch the
catheter distal end such that the blood outlet end 46 extends
distal of the blood inlet opening 47.
[0075] Referring now to FIGS. 2A, 2B and 2C, one embodiment of the
paracorporeal respiratory assist lung 20 of the present invention
includes an outer housing 22 surrounding a stationary core 24. A
rotating fiber bundle 26 is contained within the outer housing and
around the stationary core. A motor drive mechanism 28 is operably
connected to the main housing of the paracorporeal respiratory
assist lung. The stationary core includes a main body 30 having a
blood inlet port 32 that allows blood to diffuse from the
stationary core through a fiber mat 40 of the rotating fiber
bundle. The outer housing is further configured with a blood outlet
port 34 that, along with the blood inlet, may be connected to a
cannula (not shown) configured to be inserted into the patient
vasculature (FIG. 1). The outer housing is further configured with
a gas inlet nozzle 36 and a gas outlet nozzle 38 that are in fluid
communication with the fiber mat of the rotating fiber bundle. The
fiber mat is fixedly connected to a support mechanism 42 that is
connected to a drive shaft 44 that is operably connected to the
motor drive mechanism. The support mechanism for the fiber mat may
be configured as a wire or mesh cage (FIGS. 16A, 16B) or other
suitable embodiments to enhance blood flow through the fiber bundle
while minimizing any damage to the blood components, e.g., limiting
hemolysis.
[0076] Referring now to FIGS. 3A, 3B, 3C and 3D, the paracorporeal
respiratory assist lung 50 of the present invention includes a
central outer housing 52 having a blood outlet port 64. A first end
portion 54 of the outer housing includes a blood inlet port 62 and
a gas inlet nozzle 66. A second end portion 58 of the outer housing
includes a gas outlet nozzle 68. The first and second ends of the
housing may be configured with threads or other mechanism to secure
the ends of the housing to the central portion. A rotating fiber
bundle mechanism 56 is configured to be disposed within the housing
and includes a support mechanism (not shown) for retaining the
fiber bundle while allowing blood to flow from the housing inlet
through the fibers. The fiber bundle may be formed from an annular
fiber mat 60 that is in fluid communication with the gas inlet and
the gas outlet. The rotating fiber bundle mechanism further
includes a drive shaft 74 that may be mechanically connected to a
motor mechanism (not shown). The rotating fiber bundle mechanism
may be further configured with a potting 72 to hold the ends of the
fibers of the fiber mat.
[0077] Referring now to FIGS. 4A and 4B, the paracorporeal
respiratory assist lung 80 used for testing purposes generally is
configured with an outer housing 82 that surrounds a rotating fiber
bundle 86 having a stationary core 84 disposed with the fiber
bundle and the housing. Blood 100 enters the device through an
inlet port 92 of the stationary core. Oxygen laden sweep gas 96
enters the rotating fiber core so that oxygen and carbon dioxide
are exchanged to and from the blood along the fiber bundle. The
rotating fiber bundle is configured with a drive shaft 104 for
rotating the fiber bundle relative to the stationary core and outer
housing. Referring to FIGS. 20, 21 and 22, typical experimental
conditions using the paracorporeal respiratory assist lung of the
present invention that achieved (a) increased CO.sub.2 removal per
area by 133%; (b) increased O.sub.2 removal per area by 157%; and
(c) generated 1 1/min flow against fifty mmHg at 1500 rpm include:
(i) test fluid of water or slaughterhouse bovine blood; (ii) fluid
flow rate at 750 ml/min; (iii) sweep gas flow rate at 6.5 1/min;
(iv) loop temperature at 37.degree. C.; (v) inlet pCO.sub.2 at 45
+/-5 mmHg; (vi) inlet O.sub.2 saturation at 65%; (vii) blood
hematocrit at 35%; and (viii) blood hemoglobin concentration at
12.1 milligrams per deciliter (mg/dl).
[0078] A hollow fiber membrane bundle that has an annular
cylindrical geometry can function as a pump when the bundle is
rotated. Fluid in the bundle, however, becomes significantly
entrained in the fiber rotational motion (the relative velocity
between the fibers and the fluid goes to zero), and hence the
rotation does not increase mass transfer efficiency for fiber
bundles more than a few layers thick. A hollow fiber membrane
bundle can be oscillated to reduce the entrainment of fluid because
oscillation hinders the fluid velocity from reaching the fiber
velocity. One aspect of the present invention is to introduce
oscillations in the steady rotation of a hollow fiber bundle to
increase the mass transfer efficiency of the device while
maintaining its pumping capabilities.
[0079] As shown in FIGS. 18 and 19, the paracorporeal respiratory
assist lung of the present invention acts as an integrated
pump/hollow fiber membrane mass transport device, and shows mass
transfer enhancement when the rotational velocity of the fiber
bundle is rapidly varied. To enhance performance of the gas
exchange achieved by the paracorporeal respiratory assist lung,
various modes of spinning the fiber bundle may be employed, e.g.,
steady rotation, unsteady rotation, purely oscillatory rotation and
other forms of time-dependent rotation. As will be appreciated by
those of ordinary skill in the art, known and to-be-developed
gas-permeable fibers may be used with the present invention, for
example, hollow micro-porous polypropylene fibers and gas-permeable
fibers currently used in blood oxygenators. The gas-permeable
fibers may include a coating of a gas-permeable polymer and may be
bonded with a non-thrombogenic component.
[0080] The rotation actuator device may include a motor that is
coupled to the fiber bundle. Oxygen is passed through the hollow
fibers, and fluid (e.g., water or blood) may be introduced to the
fiber bundle through an internal diffuser. Seals and bearings
separate the gas and fluid pathways and allow the fiber bundle to
be rotated with an external motor. A brushless DC servomotor may
control the motion of the hollow fiber membrane bundle. The user of
the paracorporeal respiratory assist lung may set the frequency and
amplitude of oscillation with a computer connected to a controller.
The controller signals a drive to perform the input motion while
getting feedback from the motor and making adjustments to the
velocity.
[0081] In a further embodiment of the present invention, the
paracorporeal respiratory assist lung is configured to increase the
porosity in the rotating fiber bundle. The increased porosity
provides more fluid to flow through the fiber bundle, thus
increasing the overall mass transfer efficiency of the device. The
extra porosity in the fiber bundle is created by several possible
ways including, but not limited to, using spacers to create void
space between the fiber layers, removing every other fiber in the
mat and using smaller diameter fibers. Additionally, support
threads could be removed from the fiber fabric, and the
paracorporeal respiratory assist lung could be configured such that
the manifolds are relatively closer so as to "puff out" the fiber
bundle.
[0082] As shown in FIGS. 17A and 17B, spacers can be created by
placing thin strips of felt that are soaked in polyurethane or
other suitable material across a fiber mat. In accordance with the
present invention, as the fiber mat is rolled up, the felt is
rolled with it, which then hardens as the adhesive dries. The dried
felt then creates the extra space between the fibers. However, the
fiber surface area where the felt is touching is not included in
the operable surface area of the paracorporeal respiratory assist
lung. Alternatively, by removing every other fiber in the fiber
mat, the fiber mat is left with many open spaces having only wefts
and no fibers. The same overall surface area and number of fibers
may be the same, but the fibers are much more spaced out, thus
creating a "puffy bundle." Further, gas-permeable fibers having a
reduced outer diameter can also be used to create higher porosity
devices. The higher porosity of the fiber bundle results from a
reduced fiber density, i.e., the fiber density in a mat of smaller
outer diameter fibers is less than fiber mats having larger outer
diameter fibers. There is much more open space where only wefts
exist, similar to configurations of the fiber bundle where every
other fiber is removed.
[0083] The paracorporeal respiratory assist lung of the present
invention achieves significant CO.sub.2 removal (100-120 ml/min) at
relatively low veno-venous blood flow rates (500-1000 ml/min)
without the need for a separate pump. FIGS. 23-25 demonstrate the
effect of fiber bundle porosity on the gas exchange and pumping
performance of the paracorporeal respiratory assist lung. Two
prototype paracorporeal respiratory assist lung devices were
fabricated with bundle porosities of 0.43 and 0.83, but otherwise
similar with membrane areas of 0.42 square meters (m.sup.2) and
0.50 m.sup.2 respectively. The devices were tested for gas exchange
in a flow loop using water as the test fluid at three 1/min. The
paracorporeal respiratory assist lung prototype with the higher
bundle porosity achieved CO.sub.2 removal at 1500 rpm of 173
ml/min/m.sup.2 compared to 190 ml/min/m.sup.2 for the prototype
with the lower bundle porosity. In bovine blood, the paracorporeal
respiratory assist lung with the higher bundle porosity at 1500 rpm
achieved a CO.sub.2 removal rate of 182 ml/min/m.sup.2 at a blood
flow rate of only 750 ml/min. In a separate pump test in water, the
fiber bundle with higher porosity generated 67 mmHg compared to
only 52 mmHg for the fiber bundle with the lower porosity at 0.75
1/min flow at 1500 RPM with water as the test fluid. The fiber
bundle with increased porosity is within ten percent of a gas
exchange target, and the pumping ability is consistent with
generating 750 ml/min blood flow through percutaneous cannula less
than 20 Fr.
[0084] Referring now to FIGS. 5A through 5P, one embodiment of the
PRAL device includes an outer housing 520 having an upper portion
524 and a lower portion 522. The upper portion of the PRAL device
500 includes a blood inlet 530 and a gas outlet 545. The lower
portion of the housing includes a gas inlet 540 and a blood outlet
port 535. This embodiment of the PRAL device includes a rotating
fiber bundle having an external drive connection 525. As shown in
FIG. 5D, the drive mechanism 525 is connected to an internal
coupling 527 that can exit to the fiber bundle 550. The PRAL device
includes a stationary core 560 that is configured with a lumen or
blood conduit having an outside end 532 and an inside end 534. The
inside end of the blood conduit is attached to an impeller device
570 which may include a plurality of arcuate arms 572 that assist
in directing blood flow through the fiber bundle 550. The PRAL
device is configured with an annular space 590 between the rotating
fiber bundle 550 and the outer housing 520. Blood flow commencing
at the entrance 530 and traveling from the impeller 570 through the
fiber bundle 550 and gap 590 exits through the port 535. Sweep gas,
such as oxygenated air, enters the PRAL device through entry port
540 travels through the fiber bundle 550 wherein carbon dioxide and
oxygen are exchanged with the blood and the carbon dioxide laden
gas exits through the port 545 in the upper portion 524 of the PRAL
device. The upper portion of the PRAL device is further configured
with a retaining device 565 that secures the core 560 and blood
conduit 530 within the housing 520.
[0085] Referring now to FIG. 6, an alternative embodiment of the
PRAL device 600 includes an outer casing 620 having a blood and
fluid inlet 630 and fluid outlet 635 passes through the inlet
through a conduit 632 that bifurcates into a first conduit 634 and
a second conduit 636 that direct blood through the fiber bundle
650. The fiber bundle is connected to a drive mechanism 625 that is
connected to a motor drive 628. A plurality of sealing mechanisms
690 are included to separate the rotating fiber bundle and blood
flow from the gas pathway. Gas enters the system through inlet 640
that is connected to the fiber bundle and exits through the gas
outlet port 645 in fluid communication with the fiber bundle
650.
[0086] Referring now to FIG. 7, an alternative embodiment of the
PRAL device 700 includes an outer casing 720 having a blood and
fluid inlet 730 and fluid outlet 735 passes through the inlet
through a conduit 732 that directs blood through the fiber bundle
750. The fiber bundle is connected to a drive mechanism 725 that is
connected to a motor drive 728. A plurality of sealing mechanisms
790 are included to separate the rotating fiber bundle and blood
flow from the gas pathway. Gas enters the system through inlet 740
that is connected to the fiber bundle and exits through the gas
outlet port 745 in fluid communication with the fiber bundle 750.
This particular embodiment further includes a stationary core 760
positioned inside of the rotating fiber bundle 750.
[0087] Referring now to FIG. 8 is an alternative embodiment of the
PRAL device 800 in accordance with the present invention. The PRAL
device includes an outer shell 820 having a lower portion 822 and
an upper portion 824 secured to the main body 820. The upper
portion of the device includes a blood inlet 830 connected to a
conduit 832 having a distal end 834 for providing blood flow
through a central core 860 and an impeller 870. The blood flow
passes through a rotating fiber bundle 850 that is connected to a
drive mechanism 825. Gas enters from the lower portion 822 of the
housing through an inlet gas port 540 that is in fluid
communication with the fiber gas bundle 850 and an exit gas port
845. A small annular gap 890 resides between the rotating fiber
bundle 850 and the outer housing 820 of the device 800. Various
seals and other mechanisms are used to isolate the gas flow from
the blood flow. Similarly, screws and other mechanisms are used to
secure the portions of the housing. In addition various seals and
bearings are used to allow the drive mechanism and rotating core to
freely move within the housing.
[0088] Referring now to FIG. 9, an alternative embodiment of the
PRAL device 900 in accordance with the present invention includes
magnetic couplings for rotating a central core. The PRAL device
includes a housing 920 having a lower portion 922 and an upper
portion 924. The upper portion includes a blood inlet conduit 930
that is connected to a blood distribution impeller 970 embodied
within the rotating core 960. The lower portion of the body 922
includes seals and bearings 980 and a pin or other mechanism 982
for the rotating core to rest within the housing. This embodiment
of the PRAL device includes a stationary fiber bundle 950 having a
gas inlet 940 and a gas outlet 945. Blood flows from the inlet 930
through an internal gap 922 past the bundles 950 through a
recirculation gap 990 and out the blood exit port 935. The internal
and recirculation gaps between the rotating core and the outer
housing allow for a recirculation or eddy effect shown by arrows
996. The rotating core is magnetically coupled to an external
device via magnets 984 and 986 secured to the rotating core.
[0089] Referring now to FIGS. 10A and 10B, an alternative
embodiment of the PRAL device 1000 may be further configured with a
rotating core mechanism. The PRAL device includes an outer body
1020 having a lower portion 1022 and an upper portion 1024. A motor
drive mechanism 1025 is configured within the lower portion. A gas
inlet port 1040 is also configured in the lower portion of the
housing. A stationary fiber bundle 1050 is positioned within the
main body 1020 of the housing that is configured to accept a
rotating cord 1060. Various seals and securing devices 1062, 1064,
1066 and 1068 are shown in FIG. 10B.
[0090] Referring now to FIG. 11, the PRAL device 1100 is also
configured with a rotating core mechanism and stationary fiber
bundle. The device is configured with an outer housing 1120 having
a lower portion 1122 and an upper portion 1124 that are secured
together forming a single unit. The lower portion of the housing
includes a motor drive mechanism 1125 operably secured to a
rotating core 1160. Blood enters from a top portion of the unit
through a blood entry port 1130 and travels to an impeller 1170.
Blood flows from the impeller through an internal gap 1192 past the
stationary fiber bundle 1150 through an outer recirculation gap
1190 and through an exit blood port (not shown). Gas enters the
fiber bundle through an entry port 1140 and exits after passing
through the fiber bundle through an exit port 1145 configured at
the top of the PRAL device. The gas entry port is located in the
lower portion 1122 of the PRAL housing 1120. A stabilizing portion
1180 secured to the lower portion of the housing includes bearings
and seals configured to accept the rotating drive mechanism 1125.
Other various seals and bearings may be employed to separate gas
and blood flow and to prevent leakage of the fluids.
[0091] Referring now to FIG. 12A and 12B, top and bottom views in
partial cutaway are shown regarding the PRAL device of FIGS. 10 and
11. As shown in FIG. 12A, blood flow is directed into impeller 1170
having a plurality of arcuate flow directing arms 1172. The blood
flow continues from the impeller to an internal gap 1192 disposed
between the rotating core 1160 and stationary fiber bundle 1150.
The blood flow travels through the stationary fiber bundle to an
outer recirculation gap 1192 and out through the blood exit port
1135.
[0092] FIG. 26 is a FEMLAB CFD (computational fluid dynamics)
simulation of blood flow occurring in one embodiment of the PRAL
device of the present invention. Shown is the longitudinal
cross-section of the FEMLAB model for the case of a PRAL device
with a rotating fiber bundle 2650 positioned between a stationary
inner housing 2600 and a stationary outer housing 2700. A first
outer gap 2690 is formed between the outer housing 2700 and the
fiber bundle 2650, and a second inner gap 2692 is formed between
the inner housing 2600 and the fiber bundle 2650. Rotation of the
annular fiber bundle 2650 creates Taylor vortices 2635 in the outer
gap 2690 between the rotating fiber bundle 2650 and the stationary
outer housing 2700. The vortices 2635 create pressure variations
2630 in the outer gap 2690. The pressure variations disturb the
blood flow pattern 2620 within the fiber bundle 2650, augmenting
relative velocity between the rotating fibers and the blood,
thereby improving gas exchange. In this and other embodiments of
the PRAL device, the size of the outer gap 2690 between the annular
fiber bundle 2650 (rotating or stationary) and the outer housing
2700 has a preferred size range. The gap size should be just large
enough that the pressure drop encountered by blood traversing the
outer gap 2690 to the device outlet be configured so as to not
prevent the establishment of a relatively uniform distribution of
radial blood flow through the annular fiber bundle 2650. This gap
size will be conditional on the permeability (porosity) and
thickness of the fiber bundle.
[0093] Referring now to FIG. 13, an alternative embodiment of the
PRAL device of the present invention includes a bundle of fibers
configured with the rotating core in addition to a stationary fiber
bundle. The PRAL device includes a housing 1320 having a lower
portion 1322 and an upper portion 1324. The upper portion includes
a blood inlet conduit 1330 that is connected to a blood
distribution impeller 1370 embodied within the rotating core 1360.
The lower portion of the body 1322 includes seals and bearings 1380
and a pin or other mechanism 1382 for the rotating core to rest
within the housing. This embodiment of the PRAL device includes a
stationary fiber bundle 1350 having a gas inlet 1340 and a gas
outlet 1345. Blood flows from the inlet 1330 through an internal
gap 1322 past the bundles 1350 through a recirculation gap 1390 and
out the blood exit port 1335. The internal and recirculation gaps
between the rotating core and the outer housing allow for a
recirculation or eddy effect. The rotating core is magnetically
coupled to an external device via magnets 1384 and 1386 secured to
the rotating core. Additional conduit 1385 is included for
providing gas flow into and out of the rotating fiber bundle
1355.
[0094] Referring now to FIG. 14, a block diagram is shown depicting
the PRAL device 1400 configured with control in electronics
computer system 1410 having a user interface 1420 with battery pack
and charger 1430 and AC-DC power supply 1435. The system may be
further configured with Ethernet or other external communication
devices 1425, 1427. Blood enters the PRAL device through inlet line
1430 and exits to the patient through outlet port 1435 having
safety mechanisms such as flow and bubble detectors. An air inlet
1440 is supplied and may be connected to a wall oxygen supply unit
1442 or oxygen tank 1444 for supplementing gas to the device. A
humidifier and/or heater 1475 may be interposed between the air
inlet and the PRAL device 1400. The sweep gas exhaust line 1445 may
include a water trap 1446 and carbon dioxide and oxygen analyzers
1448. Other valves and venting mechanisms may be included for
safety devices. For example, a vacuum pump 1490 may be interposed
between the PRAL device 1400 and the exit ports 1495 to create a
safety mechanism so that the system has a negative pressure so as
to not create bubbles within the patient's vasculature.
[0095] FIG. 15 depicts an alternative embodiment of the PRAL device
of the present invention. The PRAL device 1500 is also configured
with a rotating core mechanism and stationary fiber bundle. The
device is configured with an outer housing 1520 having a lower
portion 1522 and an upper portion 1524 that are secured together
forming a single unit. The lower portion of the housing includes a
drive mechanism 1580, 1582 operably secured to a rotating core
1560. Blood enters from a top portion of the unit through a blood
entry port 1530 and travels to an impeller 1570 having a plurality
of arms 1572. Blood flows from the impeller through an internal gap
1592 past the stationary fiber bundle 1550 through an outer
recirculation gap 1590 and through an exit blood port (not shown).
Gas enters the fiber bundle through an entry port (not shown) and
exits after passing through the fiber bundle through an exit port
(not shown) configured at the top of the PRAL device. The gas entry
port is located in the lower portion 1122 of the PRAL housing 1120.
The device includes magnets 1584 and 1586 for coupling to an
external drive mechanism. Other various seals and bearings may be
employed to separate gas and blood flow and to prevent leakage of
the fluids. The magnets and housing may be configured to allow the
rotating core to levitate above the bottom portion of the housing,
thereby reducing friction in the device. Other various seals and
bearings may be employed to separate gas and blood flow and to
prevent leakage of the fluids.
[0096] While particular forms of the invention have been
illustrated and described, it will also be apparent to those
skilled in the art that various modifications can be made without
departing from the inventive concept. References to use of the
invention with a membrane electrode assembly and fuel cell are by
way of example only, and the described embodiments are to be
considered in all respects only as illustrative and not
restrictive. The present invention may be embodied in other
specific forms without departing from its spirit or essential
characteristics. Accordingly, it is not intended that the invention
be limited except by the appended claims.
* * * * *