U.S. patent application number 09/079863 was filed with the patent office on 2002-05-16 for integrated blood oxygenator and pump system having active blood oxygenator.
Invention is credited to AFZAL, THOMAS A., WILLIAMS, RONALD G..
Application Number | 20020057989 09/079863 |
Document ID | / |
Family ID | 22153282 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020057989 |
Kind Code |
A1 |
AFZAL, THOMAS A. ; et
al. |
May 16, 2002 |
INTEGRATED BLOOD OXYGENATOR AND PUMP SYSTEM HAVING ACTIVE BLOOD
OXYGENATOR
Abstract
An integrated blood oxygenation and pump system suitable for use
in a sterile field having a low priming volume is provided in which
a blood oxygenator portion of the system includes an active
element, separate from the pump, that disrupts the development of
laminar flow and stagnation zones in the fiber bundle employed for
gas exchange. The integrated system enables the pump and oxygenator
to be used independently of one another or be rapidly reconfigured
to provide both pumping action and blood oxygenation.
Inventors: |
AFZAL, THOMAS A.; (MENLO
PARK, CA) ; WILLIAMS, RONALD G.; (MENLO PARK,
CA) |
Correspondence
Address: |
NICOLA A PISANO
FISH AND NEAVE
1251 AVENUE OF THE AMERICAS
NEW YORK
NY
100201104
|
Family ID: |
22153282 |
Appl. No.: |
09/079863 |
Filed: |
May 15, 1998 |
Current U.S.
Class: |
422/45 ;
604/6.11; 604/6.14 |
Current CPC
Class: |
A61M 1/267 20140204;
A61M 60/113 20210101; A61M 1/262 20140204; A61M 60/40 20210101;
A61M 1/1698 20130101; A61M 1/26 20130101; A61M 60/818 20210101;
A61M 60/205 20210101; A61M 2206/16 20130101 |
Class at
Publication: |
422/45 ;
604/6.14; 604/6.11 |
International
Class: |
A61M 001/14; A61M
001/36; A61M 037/00 |
Claims
What is claimed is:
1. A system for processing blood during a surgical procedure
comprising: a system inlet; a system outlet; a blood pump coupled
to the system inlet, the blood pump circulating blood received at
the system inlet under pressure to the system outlet, the blood
pump having an inlet connected to the system inlet and a pump
outlet through which blood is expelled from the pump; and an
oxygenator interposed between the pump outlet and the system
outlet, the oxygenator including an active element, separate from
the blood pump, that moves within the oxygenator to enhance gas
diffusion in the oxygenator.
2. The system of claim 1 further comprising a blood reservoir
coupled between the system inlet and the inlet of the blood
pump.
3. The system of claim 1 further comprising a heat exchanger
coupled to the system outlet.
4. The system of claim 1 further comprising a valve having a first
position wherein blood passing through the pump outlet is routed
directly to the system outlet and a second position wherein blood
passing through the pump outlet is routed to an inlet of the
oxygenator.
5. The system of claim 1 wherein the active element comprises: a
shaft having first and second lumens; a ring having portions
defining a first passageway and a second passageway; a first
plurality of hollow spokes coupling the first lumen in fluid
communication to the first passageway; a second plurality of hollow
spokes coupling the second lumen in fluid communication to the
second passageway; and a plurality of gas permeable hollow fibers
coupling the first passageway in fluid communication to the second
passageway.
6. The system of claim 1 wherein the oxygenator comprises a plate
including a plurality of gas-permeable hollow fibers and the active
element comprises an impeller disposed adjacent to the plate.
7. The system of claim 1 wherein the active element comprises: a
plate structure having a plurality of gas-permeable hollow fibers;
and means for imparting an oscillatory motion to the plate
structure.
8. The system of claim 1 wherein the active element comprises: a
plate structure having a plurality of gas-permeable hollow fibers;
and means for imparting a vibratory motion to the plate
structure.
9. The system of claim 1 wherein the active element comprises: an
elastomeric diaphragm disposed with the oxygenator; and an acoustic
transducer acoustically coupled to the elastomeric diaphragm.
10. The system of claim 1 wherein the blood pump and oxygenator are
housed within a unit configured to be placed in a sterile field
adjacent to an operating table.
11. The system of claim 10 further comprising: a control console
housing a motor; a cable having a lumen; a drive cable disposed in
the lumen, the drive cable having a proximal end coupled to the
motor and a distal end coupled to the active element of the
oxygenator.
12. The system of claim 10 further comprising: a control console
housing a motor; a cable having a lumen; a drive cable disposed in
the lumen, the drive cable having a proximal end coupled to the
motor and a distal end coupled to the blood pump.
13. The system of claim 12 wherein the control console further
comprises an emergency crank mechanism that enables the blood pump
to be actuated in case of power outage.
14. A system for processing blood during a surgical procedure
comprising: a system inlet; a system outlet; a blood pump coupled
to the system inlet, the blood pump circulating blood received at
the system inlet under pressure to the system outlet, the blood
pump having an inlet connected to the system inlet and a pump
outlet through which blood is expelled from the pump; an oxygenator
interposed between the pump outlet and the system outlet, the
oxygenator having an oxygenator inlet and an oxygenator outlet; and
a valve coupled to the blood pump outlet, the oxygenator inlet, the
oxygenator outlet, and the system outlet, the valve having a first
position wherein blood passing through the pump outlet is routed
directly to the system outlet and a second position wherein blood
passing through the pump outlet is routed to an inlet of the
oxygenator.
15. The system of claim 14 further comprising a blood reservoir
coupled between the system inlet and the inlet of the blood
pump.
16. The system of claim 14 wherein the oxygenator further comprises
an active element, separate from the blood pump, that moves within
the oxygenator to enhance gas diffusion in the oxygenator.
17. The system of claim 16 wherein the active element comprises: a
shaft having first and second lumens; a ring having portions
defining a first passageway and a second passageway; a first
plurality of hollow spokes coupling the first lumen in fluid
communication to the first passageway; a second plurality of hollow
spokes coupling the second lumen in fluid communication to the
second passageway; and a plurality of gas permeable hollow fibers
coupling the first passageway in fluid communication to the second
passageway.
18. The system of claim 16 wherein the oxygenator comprises a plate
including a plurality of gas-permeable hollow fibers and the active
element comprises an impeller disposed adjacent to the plate.
19. The system of claim 16 wherein the active element comprises: a
plate structure having a plurality of gas-permeable hollow fibers;
and means for imparting an oscillatory motion to the plate
structure.
20. The system of claim 16 wherein the active element comprises: a
plate structure having a plurality of gas-permeable hollow fibers;
and means for imparting a vibratory motion to the plate
structure.
21. The system of claim 16 wherein the active element comprises: an
elastomeric diaphragm disposed with the oxygenator; and an acoustic
transducer acoustically coupled to the elastomeric diaphragm.
22. The system of claim 14 wherein the blood pump and oxygenator
are housed within a unit configured to be placed in a sterile field
adjacent to an operating table.
23. The system of claim 22 further comprising: a control console
housing a motor; and a cable having a lumen; a drive cable disposed
in the lumen, the drive cable having a proximal end coupled to the
motor and a distal end coupled to the blood pump.
24. The system of claim 23 wherein the control console further
comprises an emergency crank mechanism that enables the blood pump
to be actuated in case of power outage.
25. A system for processing blood during a surgical procedure
comprising: a system inlet; a system outlet; a blood pump adapted
to be coupled to the system inlet to circulate blood received at
the system inlet under pressure to the system outlet, the blood
pump having an inlet adapted to be connected to the system inlet
and a pump outlet through which blood is expelled from the pump;
and an oxygenator having an oxygenator inlet adapted to be
selectively coupled to the system inlet or the pump outlet, the
oxygenator including an active element, separate from the blood
pump, that circulates blood received at the oxygenator inlet under
pressure to the system outlet, the active element moving within the
oxygenator to enhance gas diffusion in the oxygenator.
26. The system of claim 25 further comprising a blood reservoir
coupled between the system inlet and the inlet of the blood
pump.
27. The system of claim 25 further comprising a heat exchanger
coupled to the system outlet.
28. The system of claim 25 further comprising a valve having a
first position wherein blood passing through the pump outlet is
routed directly to the system outlet and a second position wherein
blood passing through the pump outlet is routed to the oxygenator
inlet.
29. The system of claim 25 wherein the active element comprises: a
shaft having first and second lumens; a ring having portions
defining a first passageway and a second passageway; a first
plurality of hollow spokes coupling the first lumen in fluid
communication to the first passageway; a second plurality of hollow
spokes coupling the second lumen in fluid communication to the
second passageway; and a plurality of gas permeable hollow fibers
coupling the first passageway in fluid communication to the second
passageway.
30. The system of claim 25 wherein the oxygenator comprises a plate
including a plurality of gas-permeable hollow fibers and the active
element comprises an impeller disposed adjacent to the plate.
31. The system of claim 25 wherein the active element comprises: a
plate structure having a plurality of gas-permeable hollow fibers;
and means for imparting an oscillatory motion to the plate
structure.
32. The system of claim 25 wherein the active element comprises: a
plate structure having a plurality of gas-permeable hollow fibers;
and means for imparting a vibratory motion to the plate
structure.
33. The system of claim 25 wherein the active element comprises: an
elastomeric diaphragm disposed with the oxygenator; and an acoustic
transducer acoustically coupled to the elastomeric diaphragm.
34. The system of claim 25 wherein the blood pump and oxygenator
are housed within a unit configured to be placed in a sterile field
adjacent to an operating table.
35. The system of claim 34 further comprising: a control console
housing a motor; a cable having a lumen; a drive cable disposed in
the lumen, the drive cable having a proximal end coupled to the
motor and a distal end coupled to the active element of the
oxygenator.
36. The system of claim 34 further comprising: a control console
housing a motor; a cable having a lumen; a drive cable disposed in
the lumen, the drive cable having a proximal end coupled to the
motor and a distal end coupled to the blood pump.
37. The system of claim 36 wherein the control console further
comprises an emergency crank mechanism that enables the blood pump
to be actuated in case of power outage.
38. The system of claim 1 wherein the oxygenator has a volume less
than 0.5 liters.
39. A method of processing blood through a system during a surgical
procedure comprising: receiving blood through a system inlet;
supplying blood to a blood pump for circulating blood received at
the system inlet under pressure to a system outlet, wherein the
blood pump has a pump inlet connected to the system inlet for
receiving blood and a pump outlet for expelling blood; supplying
blood expelled from the pump outlet of the blood pump to an
oxygenator containing a plurality of gas permeable fibers and an
active element; and actuating the active element to mix the blood
supplied to the oxygenator to enhance oxygenation; and supplying
oxygenated blood from the oxygenator to a system outlet.
40. A method of processing blood through a system during a surgical
procedure comprising: providing a system having a blood oxygenator,
blood pump and valve, the blood pump having a blood pump outlet and
the oxygenator having an oxygenator inlet and an oxygenator outlet;
during a first portion of the surgical procedure, configuring the
valve to direct blood expelled from the blood pump outlet to a
system outlet; and during a second portion of the surgical
procedure, reconfiguring the valve to direct blood expelled from
the blood pump outlet to the oxygenator inlet, and from the
oxygenator outlet to the system outlet.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to extracorporeal systems for
oxygenating and pumping blood during cardiac surgery. More
specifically, the present invention relates to an integrated
oxygenator and pump system wherein the oxygenator includes an
active element that enhances gas diffusion, the system being
sufficiently compact for use in a sterile field.
BACKGROUND OF THE INVENTION
[0002] Each year hundreds of thousands of people are afflicted with
vascular diseases, such as arteriosclerosis, that result in cardiac
ischemia. For more than thirty years, such disease, especially of
the coronary arteries, has been treated using open surgical
procedures, such as coronary artery bypass grafting. During such
bypass grafting procedures, a sternotomy is performed to gain
access to the pericardial sac, the patient is put on
cardiopulmonary bypass, and the heart is stopped using a
cardioplegia solution.
[0003] More recently, techniques are being developed, for example,
by Heartport, Inc., Redwood City, Calif., that permit cardiac
bypass grafting using an endoscopic approach, in which small access
openings are created between the ribs and the bypass graft or heart
valve repair procedure is performed guided by an image displayed on
a video monitor. In the "keyhole" techniques developed by
Heartport, the patient's heart is stopped and the patient is placed
on cardiopulmonary bypass. Still other techniques being developed,
for example, by Cardiac Thoracic Systems, Inc., of Menlo Park,
Calif., enable such bypass graft procedures to be performed on a
beating heart.
[0004] As a consequence of this trend towards minimally invasive
cardiac surgical techniques, the need to maintain adequate space
within the sterile field surrounding the small access sites has
become critical. Whereas in open surgical techniques the sternotomy
exposed a relatively large surgical site that the surgeon viewed
directly, minimally invasive techniques require the placement of
endoscopes, video monitors, and various positioning systems for the
instruments that crowd the sterile field and can limit the
surgeon's ability to maneuver. In recognition of the increasingly
crowded environment in which a surgeon employing minimally invasive
techniques must work, a need to miniaturize the equipment employed
in "keyhole" cardiac surgical procedures has been recognized.
[0005] While improvements have been achieved with respect to many
instruments employed in the surgical field, space-saving
improvements to previously known cardiopulmonary systems have not
kept pace. Such systems generally employ a series of discrete
components, including a blood filter, blood reservoir, an
oxygenator, a heat exchanger, a blood pump, and one or more control
systems for controlling the various components. These components
are typically coupled to one another in fluid communication using
surgical grade tubing, and generally all of the components are
maintained outside the sterile field. Such cardiopulmonary systems
are generally coupled to the patient using central cannulation
sites, e.g., via the vena cava or right atrium and the aorta, using
lengthy tubes that extend through the sterile field and may further
restrict the surgeon's ability to maneuver.
[0006] A further drawback of previously known cardiopulmonary
systems is that in those systems the tubes connecting the patient
to the device may constitute a relatively large volume.
Consequently, such systems must be primed either with transfused
blood products or saline, thus potentially compromising the
patient's immune system, diluting the patient's blood, or both. In
addition, such previously known systems comprise large non-native
surface areas and increase the risk of further jeopardizing the
patient's immune system.
[0007] In recognition of some of these disadvantages of previously
known cardiopulmonary systems, attempts have been made to
miniaturize and integrate some of the components of cardiopulmonary
systems. U.S. Pat. No. 5,270,005 to Raible describes an
extracorporeal blood oxygenation system having an integrated blood
reservoir, oxygenator, heat exchanger, pump and pump motor that is
controlled by cable connected to a control console. In the
embodiments described in that patent, venous blood passes into a
reservoir, and then through a filter, a pump, and a static array of
hollow fibers for oxygen/carbon dioxide exchange before being
returned to the patient. U.S. Pat. No. 5,266,265 to Raible
describes a similar system.
[0008] While the foregoing patents provide integrated blood
oxygenation systems having relatively compact size and reduced
priming volume, those systems rely upon relatively short flow paths
through the oxygenator to provide adequate oxygenation of the
blood. As is well recognized in the prior art, however, oxygenators
having short flow paths may provide inadequate gas exchange, due to
the development of laminar flow zones adjacent to the exterior of
the gas exchange elements.
[0009] Whereas laminar flow zones develop in most previously known
oxygenators, the large size of the gas permeable fiber bundles used
in those devices generally enable adequate mass transfer for oxygen
and carbon dioxide. The compact size and static nature of the
oxygenators describe in the foregoing Raible patents, however, may
lead to the development of laminar flow zones and stagnation zones
that impede adequate oxygen and carbon dioxide exchange. One
solution to lengthen the flow path for an integrated system is
described in U.S. Pat. No. 5,411,706 to Hubbard et al. The system
described in that patent recirculates blood through the fiber
bundle at a higher flow rate than the rate at which blood is
delivered to the patient.
[0010] Apart from the recirculation technique employed in the
Hubbard et al. patent, other methods are known for interrupting the
development of laminar flow zones. U.S. Pat. No. 3,674,440 to
Kitrilakis and U.S. Pat. No. 3,841,837 to Kitrilakis et al., which
are incorporated herein by reference, describe oxygenators in which
an active element stirs the blood within the oxygenator, thereby
disrupting the development of laminar flow zones and enhancing mass
transfer. Despite favorable test data indicating that such "active"
systems do not enhance shearing damage to the blood cells, as
reported, for example, in an article entitled "A Rotating Disk
Oxygenator," Artificial Lungs For Acute Respiratory Failure,
Academic Press, pp. 211-222 (W. Zapol ed. 1976), that technology
has nevertheless been largely abandoned.
[0011] In view of the foregoing, it would be desirable to provide a
compact extracorporeal blood oxygenation system that provides
compact size, low priming volume, low surface area, and the ability
to adequately oxygenate blood using an active element that disrupts
the formation of laminar flow zones and stagnation zones with the
fiber bundles of the oxygenator.
[0012] In also would be desirable to provide an integrated
extracorporeal blood oxygenator and pumping system having a low
priming volume and low internal surface area, thereby reducing
blood contact with non-native surfaces, potential damage to blood
components, and the risk of infection.
[0013] In addition, occasions arise during bypass surgery where it
may be desirable to alternate between providing oxygenated blood
and blood pumping. For example, in the beating-heart minimally
invasive surgical methods developed by Cardio Thoracic Systems, the
patient may not be placed immediately on cardiopulmonary bypass.
Nevertheless, it may be desirable to use a pump to reduce the load
on the heart. At a later stage of the surgery, it may be desirable
to rapidly switch from a pump-assisted, beating heart method of
surgery to a method involving stopping the patient's heart and
placing the patient on full cardiopulmonary bypass.
[0014] In would therefore be desirable to provide an integrated
extracorporeal blood oxygenator and pumping system wherein the
surgeon may select pump operation either with or without inclusion
of the blood oxygenator in the fluid circuit.
[0015] In addition, it is common practice to maintain a
cardiopulmonary unit on standby in an operating room during use of
beating heart cardiac bypass grafting procedures, and more
complicated angioplasty procedures, to enable rapid conversion to
open surgical techniques should complications develop during a
procedure.
[0016] It further would be desirable to provide an integrated blood
oxygenation and pump system having the capability to provide
pump-only capacity, but which enables the patient to be placed on
full cardiopulmonary support almost immediately.
[0017] It still further would be desirable to provide an integrated
extracorporeal blood oxygenator and pumping system having a low
priming volume, making the system suitable for emergency back-up
operation.
SUMMARY OF THE INVENTION
[0018] In view of the foregoing, it is an object of the present
invention to provide a compact, integrated extracorporeal blood
oxygenation and pump system that provides small size, low priming
volume and the ability to adequately oxygenate blood using an
active element that disrupts the formation of laminar flow zones
and stagnation zones with the fiber bundles of the oxygenator.
[0019] It is another object of the present invention to provide an
integrated extracorporeal blood oxygenator and pumping system
having a low priming volume and low internal surface area, thereby
reducing blood contact with non-native surfaces, potential damage
to blood components, and the risk of infection.
[0020] It is yet another object of this invention to provide an
integrated extracorporeal blood oxygenator and pump system wherein
the surgeon may select pump operation either with or without
inclusion of the blood oxygenator in the fluid circuit.
[0021] It is a further object of the present invention to provide
an integrated blood oxygenation and pump system having the
capability to provide pump-only capacity, but permits the surgeon
to rapidly place a patient on full cardiopulmonary support should
complications arise using a beating-heart cardiac bypass
technique.
[0022] It is a still further object of the invention to provide an
integrated extracorporeal blood oxygenator and pumping system
having a low priming volume, making the system suitable for
emergency backup operation.
[0023] These and other objects of the invention are accomplished by
providing an integrated blood oxygenation and pump system, suitable
for use within a sterile field, having a low priming volume. In
accordance with the principles of the present invention, the blood
oxygenator includes an active element, separate from the pump, that
disrupts the development of laminar flow zones and stagnation zones
in the fiber bundle employed for gas exchange.
[0024] In a preferred embodiment, the integrated blood oxygenation
and pump system includes a first compartment housing a pump coupled
in fluid communication to a second compartment housing an active
blood oxygenator. The active blood oxygenator includes an active
element, separate from the pump, that enhances mixing within the
blood oxygenator to reduce the development of laminar flow zones
and provide adequate oxygenation of the blood, without the need for
recirculation. The pump may have any one of a number of suitable
configurations, and may be axial, centrifugal, roller-type or
bladder-type.
[0025] In addition, the integrated system may include a valve that
permits the pump to be used independently of the oxygenator, or be
rapidly switched to provide both pumping action and blood
oxygenation. The active oxygenator of the present invention may
also be used independently of the blood pump for situations where a
low flow rate is acceptable, such as in pediatric cardiac
surgery.
[0026] In one embodiment, the active element comprises a rotating
disk comprising hollow fibers that carry oxygen to, and carbon
dioxide from, blood contacting the fibers. In alternative
embodiments, the fibers are fixed within the blood oxygenator
compartment, and the active element comprises an impeller that
sweeps over the surfaces of the fibers to mix the blood or a
movable diaphragm that agitates the blood within the oxygenator. In
a yet further embodiment, the hollow fibers of the oxygenator are
mounted on a disk that is agitated with an oscillatory or vibratory
motion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Further features of the invention, its nature and various
advantages will be more apparent from the accompanying drawings and
the following detailed description of the preferred embodiments, in
which:
[0028] FIG. 1 is a perspective view of an illustrative integrated
blood oxygenator and pump system constructed in accordance present
invention in use in during cardiac surgery; 5 FIG. 2 is a
perspective view of the integrated system of FIG. 1;
[0029] FIGS. 3A and 3B are, respectively, plan and front sectional
views of the system of FIG. 1;
[0030] FIGS. 4A, 4B and 4C are, respectively, an exploded
perspective view and a cross-sectional view of a first embodiment
of a blood oxygenator constructed in accordance with the principles
of the present invention, and FIG. 4C is a detailed view showing
attachment of the gas permeable fibers in FIG. 4A;
[0031] FIGS. 5A and 5B are, respectively, an exploded perspective
view and a cross-sectional view of a second embodiment of a blood
oxygenator of the present invention;
[0032] FIGS. 6A and 6B are, respectively, an exploded perspective
view and a cross-sectional view of a third embodiment of a blood
oxygenator of the present invention;
[0033] FIGS. 7A and 7B are, respectively, an exploded perspective
view and a cross-sectional view of a fourth embodiment of a blood
oxygenator of the present invention;
[0034] FIGS. 8A-8C are cross-sectional views of illustrative pump
mechanisms suitable for use in the integrated system of the present
invention;
[0035] FIG. 9A is an exploded perspective view of a valve suitable
for use in the integrated system of the present invention, while
FIGS. 9B and 9C illustrate the flow paths established when the
valve of FIG. 9A is in the pump-only and pump and oxygenator
positions, respectively; and
[0036] FIG. 10 is a plan view of a control console constructed in
accordance with the principles of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The present invention provides an integrated blood
oxygenation and pump system suitable for use with minimally
invasive cardiac surgery techniques wherein the blood oxygenator
includes an active element, separate from the pump, that enhances
gas diffusion. In accordance with the principles of the present
invention, the integrated system may be placed in or near the
sterile field, and has a low priming volume, e.g., 500 cc or
less.
[0038] The blood oxygenator and pump of the present invention
preferably are coupled to a control console, which may be located
outside the sterile field, by a cable. The integrated system may
include a valve that permits the system to be readily converted
from pump-only use to combined pump and blood oxygenator use. The
system may therefore be advantageously used in multi-step cardiac
procedures to reduce the total time a patient is placed on full
cardiopulmonary bypass, or the unit may be used as an emergency
back-up system.
[0039] The integrated system may further include inlet and outlet
ports that permit the oxygenator to be used in a stand alone mode
for pediatric applications. The system of the present invention
overcomes many of the disadvantages of previously known
cardiopulmonary systems, and provides the surgeon with flexibility
to meet the demands of minimally invasive cardiac surgery
techniques.
[0040] Referring now to FIG. 1, an illustrative integrated blood
oxygenation and pump system constructed in accordance with the
principles of the present invention is described. System 20
includes a oxygenator and pump unit 21 mounted on stand or pole 22,
and which is sufficiently compact to be positioned adjacent to
operating table 15 supporting patient P without limiting the
surgeon's ability to maneuver within the sterile field. While unit
21 is shown disposed near an edge of table 15 for illustration
purposes, it is to be understood that unit 21 preferably is located
in the sterile field, near the patient's head. Oxygenator and pump
unit 21 is coupled to control console 23 disposed on cart 24 via
cable 25, and controls operation of unit 21 in accordance with
user-selected values input at control console 23, as described
hereinbelow.
[0041] Cable 25, which is preferably a flat ribbon-type cable,
includes multiple lumens through which: (1) oxygen is communicated
to, and carbon dioxide is withdrawn from, the blood oxygenator of
unit 21; (2) electrical or mechanical power is transmitted to unit
21 to power the pump and active element of the oxygenator; and (3)
electrical leads couple blood gas parameter, temperature, flow and
pressure sensors in unit 21 to control console 23. Outlet line 26
leads from a venous cannulation site to the inlet of unit 21, while
return line 27 leads from the outlet of unit 21 to an arterial
cannulation site. Heat exchanger 28, which may be constructed in
accordance with known techniques, may be coupled in return line 27
to warm or cool the blood returned to the patient from unit 21.
[0042] With respect to FIG. 2, unit 21 includes housing 30 having
connector 31 for accepting cable 25. Blood reservoir 32 has inlet
port 33 coupling unit 21 in fluid communication with outlet tubing
26, outlet port 34 coupled in fluid communication with return line
27, and selector knob 35 which is set to select either the pump
alone or pump and blood oxygenator. Blood reservoir 32 may include
either a hard shell, formed, for example, from polycarbonate, or a
soft polyethylene bag, and preferably holds 250 ml or less of
fluid.
[0043] Vacuum-assist line 33a preferably is coupled to a source of
suction (not shown), and enhances flow of venous blood through
outlet line and into reservoir 32 of unit 21. Alternatively, unit
21 may be mounted on stand or pole 22 at a height below the surface
of table 15, to enhance drainage of venous blood to reservoir 32.
Outlet port 34 preferably includes arterial filter 36 that serves
as a bubble trap, and comprises a 20 or 40 micron filter medium
enclosed within a polycarbonate housing.
[0044] As described hereinbelow, because the active element of the
blood oxygenator may be sufficient to induce a small positive flow,
e.g., on the order of 2.0 liter/min or less, separate oxygenator
inlet and outlet ports 29a and 29b may be provided to permit
operation of the blood oxygenator portion of unit 21 in standalone
mode, such as in pediatric applications. These ports may include
plugs that are left intact if the pump portion of the unit is to be
used, or the plugs may be removed to provide oxygenator-only
operation of the system.
[0045] Referring now to FIGS. 3A and 3B, housing 30 contains pump
37 and blood oxygenator 38 coupled to biocompatible tubing 39 and
valve 40. Tubing 39 may comprise polyvinyl chloride tubing or pipe,
while valve 40 preferably is molded, machined or cast from
polycarbonate or other plastic. Pump 37 has its inlet coupled to
blood reservoir 32, and its outlet coupled to valve 40. Pump 37
generally should be capable of providing a maximum outlet flow rate
in a range of 7 to 8 liter/min. Blood oxygenator 38 has its inlet
and outlet coupled to valve 40. Depending upon the position of
selector knob 35, valve 40 couples the outlet of pump 37 to outlet
port 34 via arterial filter 36, or first passes the blood expelled
from pump 37 through oxygenator 38, and then to outlet port 34 via
arterial filter 36, as described hereinbelow.
[0046] Pump 37 and the active element of blood oxygenator 38,
described in detail hereinafter, are driven by gears 41 and 42
mounted on shafts 43a and 43b, respectively. Shafts 43a and 43b are
in turn mounted in housing 30 in bearings 44, and have ends 45a and
45b, respectively, configured to be coupled via connector 31 to
drive cables 46a and 46b disposed in cable 25. Gears 41 and 42
preferably engage gear trains 47 and 48 coupled to the active
element and pump, respectively, to drive those components at
appropriate speeds. Drive cables 46a and 46b extend through cable
25 to control console 23, where they engage electric motors.
Connector 31 also couples oxygen supply line 49a from control
console 23 to oxygenator 38, vent line 49b from oxygenator 38 to
control console 23, and various electrical leads to sensors
disposed in unit 21, such as oxygen saturation sensor 49c.
[0047] Referring now to FIGS. 4A to 4C, oxygenator 50 constructed
in accordance with the present invention is described. Oxygenator
50, which may be 10-20 cm in diameter, includes oxygenator assembly
51 disposed with a compartment comprising cylindrical sidewall 52,
upper plate 53 and lower plate 54. Components 52-54 are assembled
using conventional techniques, such as with a suitable
biocompatible adhesive.
[0048] Oxygenator assembly 51 comprises shaft 55 coupled to
pluralities of hollow spokes 57 and 58, support ring 59, and
multiplicity of hollow gas-permeable fibers 60 disposed chord-like
across the entire area of ring 59 (for clarity, only a few of
fibers 60 are shown in FIG. 4A). Shaft 55 is disposed in
fluid-tight bearings 56, so that the upper and lower ends of shaft
55 extend through upper and lower plates 53 and 54, respectively.
Gear 47a is affixed to shaft 55, and rotates shaft 55 at a speed
proportional to rotation of shaft 43a.
[0049] The ends of fibers 60 are affixed in segmented passages 61
and 62 formed in the edge of ring 59. Passages 61 and 62 may be
formed, for example, as segmented grooves in the exterior lateral
face of ring 62, and then sealed by potting material 49a that
fastens the ends of the multiplicity of hollow fibers 60 in
position. Alternatively, a knitted hollow fiber mat may be used in
place of hollow fibers 60, or a gas-permeable plate membrane
material, such as described in the above-incorporated Kitrilakis
patents, may be employed. One or more oxygenator assemblies 51 may
be employed in oxygenator 50.
[0050] As best shown in FIG. 4B, shaft 55 includes lumens 63 and 64
that extend inwards from the upper and lower ends of the shaft and
terminate at plug 65. Spokes 57 are disposed in communication with
lumen 63 of shaft 55, and carry oxygen to the inlets of hollow
fibers 60 via passage segments 61 in ring 59. Spokes 58 are
disposed in communication with lumen 64 of shaft 55, and carry
carbon dioxide from hollow fibers 60 to lumen 64 via passage
segments 62 in ring 59. Accordingly, oxygen flows into lumen 63 via
inlet port 66 and passes through spokes 57 to passage segments 61.
Passage segments in turn serve as manifolds that distribute the
oxygen to hollow fibers 60.
[0051] As oxygen diffuses through hollow fibers 60, carbon dioxide
released by the blood passes into the hollow fibers, and together
with the depleted oxygen stream, passes to passage segments 62. The
gases collected in passage segments 62 are then drawn through
spokes 58 and lumen 64, and passes through outlet port 67. These
gases then pass to control console 23 via cable 25, and are
exhausted to the atmosphere. While one
[0052] In operation, venous blood enters oxygenator 50 via inlet
port 68, or tubing connected to inlet port 29a, if provided. In
accordance with the principles of the present invention, oxygenator
assembly 51 forms an active element that is rotated by gear 47a to
enhance diffusion of oxygen into, and carbon dioxide from, blood
contained in oxygenator 50. As oxygenator assembly 51 is rotated,
e.g., at speeds in a range of 50 to 5000 RPM, a relatively
turbulent flow is maintained outside hollow fibers 60, thereby
disrupting the establishment of laminar flow zones and stagnation
zones. Oxygenated blood is exits from oxygenator 50 via outlet port
69 (or tubing connected to outlet port 29b, if provided). From
outlet port 69, the oxygenated blood passes to valve 40, then
through arterial filter 36 and outlet port 34 to return line
27.
[0053] Referring now to FIGS. 5A and 5B, an alternative embodiment
of an oxygenator constructed in accordance with the principles of
the present invention is described. Oxygenator 70, which may be
10-20 cm in diameter, includes oxygenator assemblies 71 disposed
within a compartment comprising cylindrical sidewall 72, upper
plate 73 and lower plate 74. Components 72-74 are assembled using
conventional techniques, such as with a suitable biocompatible
adhesive.
[0054] Oxygenator assemblies 71 are disposed within compartment 75
in spaced relation to impeller 77 mounted on shaft 78. Impeller 77
is disposed in fluid-tight bearing 79, so that lower end of shaft
78 extends through lower plate 74. Gear 47a is affixed to shaft 78,
and rotates impeller 77 at a speed proportional to rotation of
shaft 43a. As shown in FIG. 5B, each of oxygenator assemblies 71
comprises support ring 80 having a multiplicity of hollow fibers 81
with their ends affixed in passages 82 and 83. Passages 82 and 83
are nearly semi-circular, and serve as manifolds for carrying
oxygen to, and carrying carbon dioxide away from, hollow fibers 81.
Oxygen is introduced into passage 82 via inlet port 84, and carbon
dioxide and the depleted oxygen stream are exhausted through outlet
port 85.
[0055] In the illustrative embodiment of FIGS. 5A and 5B, two
oxygenator assemblies 71 are shown. One of skill in the art of
oxygenator design will recognize that fewer or more oxygenator
assemblies 71 may be employed, depending, e.g., upon the diameter
of the oxygenator. In addition, a knitted hollow fiber mat may be
used in place of hollow fibers 81, or a gas-permeable plate
membrane material, such as described in the above-incorporated
Kitrilakis patents, may be substituted for oxygenator assemblies
71.
[0056] Impeller 77 includes a plurality of straight or curved vanes
86, and is mounted in compartment 75 so that it sweeps over the
surfaces of oxygenator assemblies 71 without touching the hollow
fibers. Vanes 86 of impeller 77 direct blood in compartment 75 to
flow over and between hollow fibers 81, thereby enhancing mixing
and gas diffusion. Impeller 77 also may serve a pumping function,
by reducing the pressure drop experienced by the blood as it passes
through oxygenator 70. By reducing the pressure drop created by
oxygenator 38, impeller 77 may obviate the need for pump 37 to be a
high performance-type pump capable of outputting a high pressure
head. Accordingly, by using the active element of the oxygenator to
provide some pumping action in tandem with pump 37, a less
expensive, lower-performance pump may be employed.
[0057] In addition, impeller 77 may be sufficient to create a
positive low flow through oxygenator 70 when used in a stand-alone
mode of operation without pump 37. It is expected, for example,
that impeller could provide an output flow rate of up to 2.0
liter/min, thus making the oxygenator portion of unit 21 suitable
for use, in stand-alone operation, in pediatric applications.
Moreover, the ability of oxygenator 70 to provide a low flow rate
without the use of a separate pump permits the priming volume of
the system to be in a range of 300 ml or less, thus reducing the
risk of complications arising from over-dilution in pediatric
applications.
[0058] In operation, venous blood enters compartment 75 via inlet
port 87 and flows over oxygenator assemblies 71. Impeller 77 forms
an active element that is rotated by gear 47a to enhance diffusion
of oxygen into, and carbon dioxide from, blood contained in
compartment 75. Impeller 77 rotates, e.g., at speeds in a range of
50 to 5000 RPM, to induce turbulent mixing within compartment 75,
and to disrupt the establishment of laminar flow zones and
stagnation zones within compartment 75. Oxygenated blood exits from
compartment 75 via outlet port 88 and passes to valve 40, then
through arterial filter 36 and outlet port 34 to return line
27.
[0059] Referring now to FIGS. 6A and 6B, a yet further embodiment
of the oxygenator constructed in accordance with the present
invention is described. Oxygenator 90 includes baffle 95 and
oxygenator assembly 97 enclosed within compartment 91 comprising
cylindrical sidewall 92, upper plate 93 and lower plate assembly
94. Components 92-94 are assembled using conventional techniques,
such as with a suitable biocompatible adhesive. Baffle 95, which
may comprise a perforated polycarbonate sheet, is disposed in
compartment 91 below inlet port 96 in upper plate 93 to distribute
blood flowing into compartment 91 and enhance mixing.
[0060] Oxygenator assembly 97 is disposed within compartment 91
beneath baffle 95, and is arranged for vibratory and/or oscillatory
motion on shaft 98. Shaft 98, which may be stainless steel, is
mounted in fluid-tight bearings (not shown), so that the ends of
shaft 98 extend through sidewall 92 of the compartment. Gear 47a is
affixed to shaft 98, and imparts an angular oscillatory motion,
vibrational motion, or both, to oxygenator assembly 97 at a speed
proportional to rotation of shaft 43a.
[0061] Oxygenator assembly 97 comprises support ring 100 having a
multiplicity of hollow fibers 101 with their ends affixed in
passages 102 and 103. Passages 102 and 103 are nearly
semi-circular, and serve as manifolds for carrying oxygen to, and
carrying carbon dioxide away from, hollow fibers 101. Oxygen is
introduced into passage 102 via inlet port 104 of shaft 98, and
carbon dioxide and the depleted oxygen stream are exhausted through
outlet port 105 of shaft 98. Alternatively, a knitted hollow fiber
mat may be used in place of hollow fibers 101, or a gas-permeable
plate membrane material, such as described in the
above-incorporated Kitrilakis patents, may be substituted for
oxygenator assembly 97. One or more oxygenator assemblies may be
included in oxygenator 90.
[0062] In one embodiment, gear 47a is affixed to shaft 98 by
gearing that first drives oxygenator assembly through several
degrees in a first angular direction, and then reverses the
rotation and drives the oxygenator assembly an equal distance in
the reverse direction. Alternatively, a vibratory transducer may be
coupled to shaft 98 to induce vibrational motion of oxygenator
assembly 97, for example, by mounting a vibration-inducing motor
directly in housing 30. Alternatively, the output of gear 47a may
be used to drive, for example, an eccentric cam to induce vibratory
motion.
[0063] In operation, venous blood enters compartment 91 via inlet
port 96, passes through baffle 95, and flows over oxygenator
assembly 97. Oxygenator assembly 97 and shaft 98 form an active
element that is oscillated or vibrated, or both, by gear 47a to
enhance diffusion of oxygen into, and carbon dioxide from, blood
contained in compartment 91. Oscillation and/or vibration of
oxygenator assembly 97 therefore induces turbulent mixing within
compartment 91, and disrupts the establishment of laminar flow
zones and stagnation zones within the compartment. Oxygenated blood
exits from compartment 91 via outlet port 99 and passes to valve
40, then through arterial filter 36 and outlet port 34 to return
line 27, as described hereinabove.
[0064] With respect to FIGS. 7A and 7B, a still further embodiment
of the oxygenator constructed in accordance with the present
invention is described. Oxygenator 110 includes oxygenator assembly
122 enclosed within compartment 111 defined by cylindrical sidewall
112, upper plate 113 and lower diaphragm assembly 114. Sidewall 112
includes blood inlet and outlet ports 115a and 115b, respectively.
Diaphragm assembly 114 comprises elastomeric diaphragm 116, such as
silicone, mounted in support ring 117, and having acoustic
transducer 118 mounted in acoustic communication with diaphragm
116. Diaphragm assembly 119, also comprising elastomeric diaphragm
120 mounted in support ring 121, is mounted to sidewall 112
spaced-apart from upper plate 113.
[0065] Oxygenator assembly 122 is disposed within compartment 111
beneath between diaphragm assemblies 114 and 119, and comprises
support ring 123 having a multiplicity of hollow fibers 124 with
their ends affixed in passages 125 and 126. Passages 125 and 126
are nearly semi-circular, and serve as manifolds for carrying
oxygen to, and carrying carbon dioxide away from, hollow fibers
124. Oxygen is introduced into passage 125 via inlet port 127, and
carbon dioxide and the depleted oxygen stream are exhausted through
passage 126 and outlet port 128. Alternatively, a knitted hollow
fiber mat may be used in place of hollow fibers 124, or a
gas-permeable plate membrane material, such as described in the
above-incorporated Kitrilakis patents, may be substituted for
oxygenator assembly 122. One or more oxygenator assemblies 122 may
be enclosed within oxygenator 110.
[0066] Acoustic transducer 118 is coupled to control console 23 via
electrical leads 129, and imparts a vibration to diaphragms 116 and
120 that agitate the column of blood enclosed within compartment
111, thereby disrupting the establishment of laminar flow or
stagnation zones within oxygenator 110.
[0067] In operation, venous blood enters compartment 111 via inlet
port 115a, passes over oxygenator assembly 122, and exits via
outlet port 115b. Diaphragm assemblies 114 and 119 form an active
element that vibrates or agitates the blood to enhance diffusion of
oxygen into, and carbon dioxide from, blood contained in
compartment 111. Specifically, acoustic transducer 118 outputs a
pulsed acoustic signal that causes diaphragms 116 and 120 to
vibrate, thereby causing the column of blood contained within
compartment 111 to shift upwards and downwards, as illustrated by
the arrows in FIG. 7B. This movement is expected to induce
turbulent mixing within compartment 111, and to disrupt the
establishment of laminar flow zones and stagnation zones within the
compartment. Oxygenated blood exits from compartment 111 via outlet
port 115b and passes to valve 40, then through arterial filter 36
and outlet port 34 to return line 27, as described hereinabove.
[0068] Referring now to FIGS. 8A to 8C, illustrative embodiments of
pumps suitable for use in the integrated system of the present
invention are described. Pumps suitable for use in the integrated
system of the present invention preferably should provide maximum
flow rates in the range of 7 to 8 liter/min. In FIG. 7A, pump 130
is an axial-type pump, and comprises cylinder 131 having endplates
132 and 133. Shaft 134 has spiral vane 135 extending along its
length. Shaft 134 is engaged with thrust bearing 136 affixed to
endplate 132, and extends through endplate 133 through fluid-tight
bearing 137. Gearing arrangement 138, which may comprise suitably
dimensioned spline gears, couple shaft 134 to gear train 48 (see
FIGS. 3). Pump 130 has inlet port 139a disposed near endplate 133
and outlet port 139b disposed in endplate 132.
[0069] Spiral vane 135 extends from shaft 134 so that its outermost
edge is disposed close to the interior surface of cylinder 131. In
addition, vane 135 may include an elastomeric edge that sweeps
along the interior of cylinder 131 as shaft 134 is rotated by
gearing 138. Pump 130 therefore is a positive-displacement type
pump, with each revolution of shaft 134 causing vane 135 to urge a
predetermined volume of blood along a portion of cylinder 131
between inlet port 139a and outlet port 139b. Accordingly, the flow
rate of pump 130 is proportional to the speed at which shaft 134 is
rotated.
[0070] With respect to FIG. 7B, centrifugal pump 140 suitable for
use in integrated blood oxygenator and pump unit 21 of the present
invention is described. Pump 140 includes chamber 141, for example,
molded from a high strength plastic, in which impeller 142 is
disposed on shaft 143. Impeller 142 comprises a plurality of curved
vanes that urge blood introduced into the center of the pump
through inlet port 144 to flow outward, and exit the pump through
outlet port 145. Shaft 143 passes through a fluid-tight bearing 146
and includes gearing (not shown) that couples the shaft to gear
train 48 and shaft 43a of unit 21.
[0071] In FIG. 7C, another positive-displacement pump suitable for
use in the present invention is described. Pump 150 comprises
cylinder 151 forming chamber 152. Bellow-type piston 153 is
disposed chamber 152 and is coupled to source of high pressure
through port 154 and a vacuum source through port 155. Cylinder 151
includes inlet port 156 disposed at end 157 and outlet port 158
disposed in end 159. In operation, blood accumulates in cylinder
151 with bellows 153 in its contracted state, which is caused by
selectively coupling bellows to the vacuum port through port 155.
Once chamber 152 is filled, bellows 153 is uncoupled from the
vacuum source, and high pressure gas is injected into the bellows
through port 154. This in turn causes the bellows to expand, urging
blood through outlet port 158. Alternatively, a piston driven by a
rack-and pinion type gearing arrangement could be substituted for
bellows-type piston 153.
[0072] As will of course be understood by one of skill in the art
of pump designs, the foregoing pump embodiments are intended to be
illustrative only, and other types of pump mechanisms may be
readily employed in the present invention. For example,
bladder-type and roller-type pumps also may be advantageously
employed with the present invention. In addition, magnetic coupling
may be employed for driving the shafts and impellers of the
embodiments of FIGS. 8A and 8B, as described, for example, in U.S.
Pat. No. 4,944,748 to Bramm et al. and U.S. Pat. No. 5,399,074 to
Nose et al., which are incorporated herein by reference.
[0073] Referring now to FIGS. 9A through 9C, a valve suitable for
use in the present invention is described. Valve 160 comprises
valve body 161 disposed in housing 162. Body 161 comprises a high
strength plastic, such as polycarbonate, having a plurality of
channels molded or machined therein to define flow paths. Housing,
which also may be formed of polycarbonate, includes inlet 163 from
pump 37, outlets 164 and 165 coupled to outlet line 166, outlet 167
to blood oxygenator 38, and inlet 168 from blood oxygenator 38.
Outlet line 166 is coupled to arterial filter 36 and outlet port
34.
[0074] Valve body 161 includes passageways 169 and 170 and shaft
171. When valve body 161 is disposed within housing 162, the
exterior of body 161 establishes a smooth sliding contact with the
interior of housing 162. Cover plate 172 is fastened to housing 162
by a suitable adhesive, and includes aperture 173 through which
shaft 171 projects. When valve 160 is affixed within housing 30 of
integrated blood oxygenator and pump unit 21, shaft 171 projects
through the front surface of housing 30 to accept selector knob
35.
[0075] With respect to FIG. 9B, when selector knob 35 is positioned
to select pump-only operation of unit 21, valve body 161 is
oriented in housing 162 so that blood entering through inlet 163
passes directly through passageway 169 and outlet 164 into outlet
line 166. In addition, this orientation of valve body 161
effectively blocks outlet 165 from communicating with outlet line
166, thereby preventing reverse flow into the oxygenator portion of
the unit.
[0076] With respect to FIG. 9C, when selector knob 35 is rotated to
the oxygenator position, e.g., about 90 degrees, passageway 169 is
re-oriented so that one end is aligned with inlet 163 and the other
end of the passageway is aligned with outlet 167 to the blood
oxygenator. In addition, passageway 170 is moved so that one end is
in alignment with inlet 168 from the blood oxygenator and the other
end of the passageway is aligned with outlet 165 to outlet line
166. In this position, valve body 161 effectively blocks outlet 164
from communicating with outlet line 166.
[0077] Accordingly, when selector knob is moved to the oxygenator
position, blood entering the valve through inlet 163 is directed to
the blood oxygenator 38 through passageway 167, and oxygenated
blood exiting the oxygenator via inlet 168 is directed to outlet
line 166 via passageway 170. If, on the other hand, it is desired
to employ system 20 in a pediatric cardiac application without
using pump 37, outlet line 26 and return line 27 may be directly
coupled to inlet and outlet ports 29a and 29b of unit 21, to
provide blood oxygenation and low flow rate. In this latter case,
selector knob 35 is left in the pump-only position, thereby
isolating inlet port 167 and outlet port 168 from valve 160.
[0078] In view of the foregoing, it will be understood that
integrated blood oxygenator and pump unit 21 may be advantageously
used to reduce the pumping load of a beating heart during a first
portion of a minimally invasive procedure, in which the pump is
operated in pump-only mode, followed by placing the patient on full
cardiopulmonary bypass for a portion of the surgical procedure
requiring that the heart be stopped. The system therefore reduces
the total time a patient is put on cardiopulmonary bypass, and thus
reduces the potential for myocardial infarction. In addition, unit
21 may advantageously used to provide back-up or emergency
cardiopulmonary bypass capability during beating-heart cardiac
procedures, and when complications arise during high-risk
atherectomy or angioplasty. The system may alternatively be used in
oxygenator-only mode where a low flow rate is desirable. The system
of the present invention therefore provides a degree of flexibility
heretofore unavailable.
[0079] With respect to FIG. 10, control console 23 constructed in
accordance with the present invention is described. Control console
23 includes housing 180 having video screen 181, control panel 182,
adjustment knobs 183, connector 184 for coupling to an oxygen tank,
and connector 185 that accepts cable 25. Control console 180 houses
electronics board 186 including microprocessor 187, variable speed
motors 188a and 188b, emergency crank mechanism 189 and back-up
battery 190. Housing 180 also includes piping 184a coupling
connector 184 to a lumen of cable 25, and wiring 191 coupling
electronics board 186 to oxygen saturation, oxygen pressure, carbon
dioxide concentration, pressure, flow rate and pH sensors disposed
in unit 21.
[0080] Microprocessor 187 is programmed to control operation of
variable speed motors 188a and 188b responsive to flow rate values
input using control panel 182, to monitor blood gas parameter
sensors, such as oxygen saturation, carbon dioxide, temperature,
flow, and pressure sensors located in integrated blood oxygenation
and pump unit 21, and to display graphs of the measured values on
video screen 181. The blood gas parameter sensors, monitoring
electronics, and display algorithms employed in control console 23
are per se known.
[0081] Microprocessor 187, which may be a 486 or Pentium.RTM.-class
chip, may also be programmed to display, for example, blood pH and
oxygen and carbon dioxide partial pressures, and blood temperature.
Electronics board 186 may also include magnetic disk storage (not
shown) to enable microprocessor 187 to periodically store samples
of the desired values in a file for later review. Back-up battery
190 provides continued operation of electronics board 186 and
microprocessor 187 in the event of a power outage.
[0082] Motors 188a and 188b are mounted within control console
housing 180 and are coupled to drive cables 46a and 46b in cable 25
through transmission 192. Drive cables 46a and 46b are disposed in
lumens of cable 25 (see FIG. 2) and transmit rotational motion
imparted by motors 188a and 188b, respectively, to shafts 43a and
43b of unit 21, thereby driving the active element of the blood
oxygenator 38 and pump 37.
[0083] Each of motors 188a and 188b is coupled to transmission 192
via shaft 193. The proximal end of shaft 193 includes motor spline
assembly 194 that releasably engages the output shaft of the motor,
while the distal end of shaft 193 slidably engages drive shaft 195
coupled to transmission 192 using output spline assembly 196.
Emergency manual crank mechanism 189 includes shaft 197 mounted for
reciprocation in bearings 198. Gear 199 is fixed to shaft 197,
while spring 200 biases shaft 197 in direction A. Gears 201 and
thrustplates 202 are mounted on each of shafts 193, and biased in
direction A by spring 203. Hand crank 204 is mounted on end 205 of
shaft 197 to periodically actuate pump 37 and blood oxygenator 38
in the event of a power outage.
[0084] Emergency crank mechanism 189 operates as follows: hand
crank 204 is first placed on end 205 of shaft 197, and shaft 197 is
pushed inward against the bias of spring 200. The resulting motion
of shaft 197 causes gear 199 to engage gear 201 and thrustplate 202
on each of shafts 193. This motion in turn causes shafts 193 to
move in direction B against the bias of springs 203, and also
disconnects motor spline assemblies 194 from the output shafts of
motors 188a and 188b. Hand crank 204 may then be turned, with the
resulting rotational motion being transmitted from hand crank 204
to drive cables 46a and 46b through gears 199 and 201 and shafts
195 and transmission 192. When pressure on hand crank 204 in
direction B is removed, springs 200 and 203 again urge shafts 197
and 193 in direction A, thus causing motor spline assemblies 194 to
again couple the output shafts of motors 188a and 188b to shafts
193.
[0085] While preferred illustrative embodiments of the invention
are described above, it will be apparent to one skilled in the art
that various changes and modifications may be made therein without
departing from the invention and it is intended in the appended
claims to cover all such changes and modifications which fall
within the true spirit and scope of the invention.
* * * * *