Note: Descriptions are shown in the official language in which they were submitted.
CA 02541337 1997-10-03
CIRCULATORY SUPPORT SYSTEM
This application is a divisional of Application Serial No. 2,268,066,
filed October 3, 1997.
BACKGROUND
1. Technical Field
The present disclosure relates generally to circulatory support
systems, and, more particularly, to a circulatory support system to provide
partial or
total bypass of the heart. The present disclosure is further directed to an
axial flow
pump and a portable microprocessor-based controller each being adapted for use
in
the circulatory support system.
2. BackEround of the Related Art
Mechanical blood pumps are commonly utilized to temporarily
support or substitute the pumping function of the heart during heart surgery
or
during periods of heart failure. The most widely applied blood pumps include
roller
pumps and centrifugal pumps. Typically, these pumps are a component of a
cardiopulmonary bypass system (e.g. a heart-lung machine) which includes an
oxygenator, a heat exchanger, blood reservoirs and filters, and tubing which
transports the blood from the patient through the bypass system and back to
the
patient. With these systems, blood is withdrawn from the patient via uptake
cannula
positioned within the vena cavae and atria or ventricles of the heart and
pumped
back into the pulmonary artery and aorta via a return cannula.
Although the aforedescribed cardiopulmonary bypass systems have
been generally effective for their intended purposes, these systems are
subject to
certain disadvantages which detract from their usefulness. In particular,
conventional bypass systems are relatively complicated and expensive to
manufacture, expose the blood to a high surface area of foreign materials
which may
damage the blood, require full anticoagulation and cooling of the heart, and
require
considerable set up time and continual management by a skilled technician.
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These systems also require mechanical oxygenation of the blood which can have
adverse affects on the patient.
U.S. Patent No. 4,610,656 to Mortensen/Mehealus Partnership
discloses a semi-automatic heart-lung substitution system. The Mortensen '656
system includes a roller pump which pumps blood from the patient's right heart
via
a venous cannula to a membrane oxygenator connected at the output of the
roller
pump. From the oxygenator, the blood flows to a compliance reservoir which is
connected to a pulsatile left heart pump. Blood is pumped by the pulsatile
left
heart pump through a filter and bubble trap and then returned to the patient's
arterial system through an arterial cannula. The Mortensen '656 system,
however,
is also a relatively complex device including several pumps and an oxygenator
and,
consequently, requires attendance of skilled technicians for set-up and
operation.
SUMMARY
Accordingly, the present disclosure is directed to a circulatory
support system to support the functioning of the heart. In a preferred
embodiment,
the support system includes an ex_tracorporeal pump member having a pump
housing dimensioned for positioning directly on or adjacent to the chest area
of a
patient and defining inlet and outlet ports, a rotating member rotatably
mounted in
the pump hous'mg to impart mechanical energy to blood entering the inlet port
and
to direct the blood through the outlet port, an inlet cannulated tube
connected to
the inlet port of the pump housing and having an inlet open end portion
dimensioned for insertion within the patient's heart whereby blood is drawn
from
the heart through the inlet cannulated tube and directed into the pump
housing, and
an outlet cannulated tube connected to the outlet port of the pump housing and
having an outlet end portion dimensioned for insertion within a major blood
vessel
associated with the heart whereby blood exiting the outlet port of the pump
housing
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is conveyed through the outlet cannulated tube into the major blood vessel for
transfer by the arterial system of the patient.
The support system is particularly contemplated for left heart bypass
while the right heart functions to direct blood to the lungs. It is envisioned
that
the right heart may be slowed or even stopped while the support system is
utilized
for left heart bypass.
A method for providing at least partial bypass of the heart to
supplement the pumping function of the heart to thereby enable the surgeon to
perform various surgical procedures thereon is also disclosed. The method
includes the steps of providing a circulatory assist system having a portable
extracorporeal axial flow pump with a pump housing and inlet and outlet pons,
a
rotating pumping member disposed in the pump housing and inlet and outlet
cannulated tubes respectively connected to the inlet and outlet ports of the
pump
housing, accessing the patient's left ventricle of the heart with the inlet
cannulated
tube, accessing the aorta with the outlet cannulated tube, actuating the
rotating
pumping member to draw oxygenated blood from the left ventricle of the heart
through the lumen of the inlet cannulated tube and into the inlet port of the
pump
housing whereby the pumping member imparts mechanical energy to the
oxygenated blood passing through the pump housing and directs the oxygenated
blood through the outlet port and through the lumen of the outlet cannulated
tube
to be transferred by the aorta to the systemic arteries, and permitting blood
returning through the systemic veins to the right atrium to be directed
through the
right ventricle to the patient's lungs for oxygenation and subsequent
pulmonary
circulation. The left ventricle may be accessed through the heart wall, mitral
valve
or aortic'valve. In an alternate embodiment, a second circulatory assist
system
may be utilized to facilitate the pumping function of the right side of the
heart.
CA 02541337 1997-10-03
The present disclosure is further directed to a pump to be used in the
circulatory support system. The pump includes a pump housing including an
inlet
end portion defining an inlet port for permitting blood to enter the pump
housing
and an outlet end portion defining an outlet port for permitting blood to exit
the
pump housing. The inlet and outlet end portions preferably each have central
hub
portions with straightener blades extending therefrom for facilitating passage
of
blood through the pump housing. A rotatable member is mounted for rotational
movement to the central hub portions of the pump housing. The rotatable member
includes at least one impeller blade for imparting pump energy to blood
passing
through the pump housing and a magnetically actuated rotor. A motor stator is
disposed in the pump housing and has at least one stator blade extending from
an
inner surface thereof. The one stator blade and the one impeller blade of the
rotatable member are cooperatively configured to exert a substantially axial
flow
pumping energy to blood flowing along the blood path. Preferably, the one
impeller blade and the one stator blade each extend axially and peripherally
within
the pump housing.
The present disclosure is further directed to a control unit to be used
in the circulatory support system. In an exemplary embodiment, the control
unit
includes circuitry for supplying power to the flow pump to cause the pump to
rotate, and circuitry responsive to a pressure sense signal from a pressure
transducer located on the inlet side of the pump (e.g., within the atrium),
for
commanding a reduction in motor speed to a lower speed when the pressure is
determined to be below a predetermined threshold. The control unit preferably
also includes circuitry responsive to a bubble sense signal provided by a
bubble
detector mounted to one of the cannulas, for generating a bubble alarm and for
causing rotation of the pump to cease if the bubble sense signal indicates the
presence of an air bubble. The control unit may further include circuitry
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responsive to the bubble sense signal indicating the presence of an air bubble
for
causing a clamping device mounted to one of the cannulas to clamp down on the
cannula to prevent air from entering the patient's bloodstream.
BRIEF DESCRIPTION OF THE DRAWING
S Preferred embodiments) of the present disclosure are described
herein with reference to the drawings wherein:
FIG. 1 is a side plan view of the circulatory support system of the
present disclosure illustrating the portable pump and the pump inflow and
outflow
sections;
FIG. 2A is a perspective view of the portable pump of the
circulatory support system with inflow and outflow sections;
FIG. 2B is a perspective view of the portable pump;
FIG. 3 is a perspective view with parts separated of the portable
pump;
FIG. 4 is a perspective view of the portable pump with portions cut
away and in cross-section;
FIG. 5 is a cross-sectional view taken along the lines 5-5 of FIG. 2B
illustrating the inlet straightener blades of the pump housing;
FIG. 6 is a perspective view of the impeller and the stator housing
of the portable pump;
FIG. 7 is an axial view of the stator housing illustrating the
arrangement of the stator blades;
FIG. 8 is a cross-sectional view of the stator housing taken along the
lines 8-8'of FIG. 7;
FIG. 9 is a cross-sectional view of the stator housing with mounted
impeller;
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FIG. 9A is a cross-sectional view of an alternate portable pump to
be used with the circulatory support system of FIG. 1;
FIG. 9B is a perspective view of the outer housing components of
the pump of FIG. 9A;
FIG. 10 is a view illustrating the system's control unit and use
thereof in conjunction with supporting the pumping function of the heart of a
patient;
FIG. 10A is an exploded view of a clamp to be used with the
control unit of FIG. 10;
FIG. 11A is an illustration of an exemplary front panel fort control
unit controlling operation of the pump;
FIG 11B is a perspective view of an exemplary control unit showing
the front portion thereof;
FIG. 11C is a perspective view of the exemplary control unit
showing the rear portion thereof;
FIG. 11D is an enlarged illustration of the rear panel shown in FIG.
11 C;
FIG. 12 is a block diagram illustrating the circuit components of the
control unit and of the pump;
FIG. 13 is a block diagram of an exemplary Control CPU used
within the control unit;
FIGS. 14A and 14B are flow diagrams illustrative of a software
routine running within the Control CPU;
FIG. 15 is a view illustrating one method of application of the
circulatory support system where the inlet cannula accesses the left ventricle
of the
heart through the mitral valve and the outlet cannula is disposed in the
aorta;
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FIG. 16 is a view illustrating an alternate method of application of
the circulatory support system where the inlet cannula accesses the left
ventricle of
the heart through the wall of the heart;
FIG. 17 is a view illustrating another method of application of the
circulatory support system where the inlet cannula accesses the Left ventricle
through the juncture of the pulmonary veins and through the mitral valve;
FIG. 18 is a view illustrating the use of a second circulatory support
system for assisting the right side of the heart;
FIGS, 19-20 are views illustrating an alternative percutaneous
method of application where the inlet cannula accesses the left ventricle
through
the aortic valve and the outlet cannula accesses the descending aorta through
the
femoral artery;
FIG. 21 is a view illustrating another method of application of the
circulatory support system where the inlet cannulated tube accesses the left
atrium
of the heart and the outlet cannulated tube is disposed in the aorta;
FIG. 22 is a view illustrating another method of application of the
circulatory support system where the inlet cannulated tube accesses the left
atrium
through the juncture of the pulmonary veins; and
FIG. 23 is a view illustrating the use of a second circulatory support
system for assisting the tight side of the heart.
LJETA~ED DESCRhPTION Or PREFERRED EMT30DIMENTS
Referring now in detail to the drawings where like reference
numerals identify similar or like components throughout the several views,
FIG. 1
illustrates a preferred embodiment of the circulatory support system in
accordance
with the principles of the present disclosure.
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Circulatory support or bypass system 10 is contemplated to
supplement or totally replace the pumping function of the heart during cardiac
surgery and/or during temporary periods of heart failure. The system 10 can
also
be used during medical emergencies such as trauma, heart attack or heart
failure.
Circulatory support system 10 is particularly contemplated for patients in
need of
partial bypass of the left side of the heart while oxygenation of the blood
may be
maintained with the patient's own lungs. Support system 10 is advantageously
arranged to be a portable unit which facilitates handling and reduces cost and
incorporates a portable control unit discussed in greater detail below.
Referring now to FIGS. 1-4, support system 10 includes an axial
flow pump 12 and inlet and outlet sections 14, 16 associated with the axial
flow
pump 12. Inlet and outlet sections 14, 16 will be discussed in greater detail
below.
As best depicted in FIGS. 3-4, axial flow pump 12 includes pump housing 18
composed of housing half sections 18a, 18b secured to each other with the use
of
adhesives, screws or the like. Inlet and outlet connectors 20, 22 are
respectively
mounted within inlet and outlet openings 24, 26 of pump housing I8. As can be
seen, the inlet and outlet openings 24, 26 are in axial alignment although
offset
arrangements are envisioned as well. In a preferred arrangement, cylindrical
mounting portions 20a, 22a of the respective connectors 20, 22 are positioned
within sleeve 62 within the inlet and outlet openings 24, 26 of pump housing
18
and retained therein in a manner discussed in detail below. O-ring seals 28,
30
may be utilized to provide fluid tight seals between connectors 20, 22 and
pump
housing ~ 18. Connectors 20, 22 respectively connect inlet and outlet
eannulated
tubes 66, 68 to flow pump 12.
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In a preferred embodiment, the length of the pump 10 ranges from
about 3.0 inches to about 4.5 inches, more preferably, about 3.76 inches, and
the
diameter ranges from about 0.7 inches to about 2.0 inches, more preferably,
about
1.2 inches. Other dimensions are contemplated which maintain the functionality
and portability of the pump.
With particular reference to FIG. 4, inlet and outlet connectors 20,
22 include central interior hub portions 32, 34 respectively. Hub portion 32
of
inlet connector 20 has inlet straightener blades 36 (e.g., 3) extending from
the
outer surface of the hub 32 to the inner surface of the connector 20 as also
depicted in the cross-sectional view of FIG. 5. Similarly, hub portion 34 of
outlet
connector 22 has outlet straightener blades ~7 extending from, the outer
surface of
the hub 34 to the inner surface of the connector 22. Straightener blades 36
provide an axial flow effect on the blood entering flow pump to facilitate
flow of
the blood through the pump 12 to improve pump efficiency. Similarly,
straightener blades 37 provide an axial flow effect on the blood exiting pump
12 to
facilitate blood flow through outflow cannulated tube 16 and within the
circulating
system of the patient. However, blades 36, 38 are not required and may be
substituted with one or more support struts which. have little or no affect on
the
blood flow and may function to support bearings on which the impeller rotates.
As depicted in FIGS. 1-4, outlet connector 22 has snap ring 40
mounted about its periphery and retained thereon by spring clip 42. Snap ring
40
functions to snap onto housing 18 to retain outlet connector 22 onto the
housing.
Similarly, a snap ring (not shown) may be utilized to retain inlet connector
20 on
housing 18, or, in the alternative, the connectors 20, 22 may be mounted to
the
housing 18 with the use of adhesives or the like.
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Referring now to FIGS. 3, 4, and 6-9, pump housing 18 includes
cylindrical stator housing 44 disposed in central portion 46 of the pump
housing
18. Stator housing 44 may include four stator blades 48 attached to its
interior
wall. Stator blades 48 extend axially and also peripherally within the
interior wall
of stator hous'~ng 44 to define the generally serpentine configuration of the
blades
shown. Stator blades 48 provide a general axial flow type effect on the blood
passing through pump housing 18.
An impeller 50 extends through stator housing 44 and is mounted via
rotating shaft 52 to interior hubs 32,34 of inlet and outlet connectors 20,
22,
respectively. It is envisioned that bearings (e.g., sleeve) may be utilized to
mount
shaft 52. The bearings are preferably formed of polyethylene or the like.
Impeller 50 has a plurality (e.g., 5) of impeller blades 54. Impeller blades
54
extend axially and circumferentially about the outer surface of the impeller
SO to
provide an axial-flow pumping energy to blood entering pump housing. The outer
surface of impeller 50 and the inner surface of stator housing 44 define an
annular
gap or blood path 56 through which blood passes through pump housing 18.
Impeller 50 has a built-in 2-pole rotor magnet 58 as best depicted in FIG. 9.
Blood flowing through this gap washes the bearings at the junction between the
rotating and stationary components to cool the bearings and prevent
thrombosis,
thus avoiding having to provide a seal. In a preferred method of manufacture,
impeller 50 is molded about shaft 52.
With reference again to FIGS. 3-4 and 9, the motor includes a motor
stator 60 and rotor magnet 58. Motor stator 60 includes laminations and
windings
disposed between a sleeve 62 coaxiallymounted about stator housing 44, and the
interior vsrall of pump housing 18. Motor stator 60 is electrically connected
to an
external energy source. Stator 60 provides the appropriate electromagnetic
forces
to rotate the rotor magnet 58 and impeller 50. Thus, due to housing 44 and
sleeve
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62, the blood does not come into contact with motor stator 60. Motor stator 60
preferably has an outer diameter of about .70 inches to about 2.0 inches and
preferably about .97 inches, thereby keeping the overall size of pump 10
relatively
small.
Preferably, pump housing 18, stator housing 44 and impeller 50 are
fabricated from a polymeric material and formed by conventional injection
molding
techniques. In a preferred arrangement all blood contacting surfaces are
coated
with an anti-thrombotic agent to prevent thrombosis development.
FIGS. 9A-9I3 illustrate an alternate embodiment of the axial flow
pump of FIG. 1. In accordance with this embodiment, most of the components
including the stator housing 44, impeller S0, etc. are substantially similar
or
identical to the prior embodiment. However, this pump includes an aluminum
cylindrical housing 1$C which replaces pump housing half sections 18a, 18b and
inlet and outlet end bells 20a, 22a which are mounted to respective end
portions of
the pump housing. End bells 20a, 22a support inlet and outlet connectors 20,
22.
This motor also includes sleeve bearings 55 mounted within hub portions 32, 34
of
the connectors 20, 22 to mount shaft 52 for rotational movement. A thrust rod
57
is disposed at least partially within inlet bearing 55 to accommodate thrust
loads
experienced during operation of the pump. Shaft 59 extends the length of
impeller
50 and defines an enlarged tapered section 59a adjacent the outlet end of the
pump.
With reference again to FIG. 1, inlet and outlet sections 14, 16 will
be discussed in detail. Each section 14, 16 includes respective flexible tubes
66,
68 connected to inlet and outlet connectors 20, 22 of axial flow pump 12 by a
friction fit. In one illustrative embodiment, tubes 66, 68 preferably extend
for a
length of about 1-2 feet. Tubes 66, 68 may be spring reinforced to facilitate
manipulation about the operative site. Preferably, at least a portion of
outlet tube
68 is compressible for reasons to be appreciated hereinbelow.
CA 02541337 1997-10-03
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Inlet and outlet callnulas or tubes 70, 72 arc connected to the rcnlotc
ends of flexible tubes 66, 63 through respective connectors 74, 76. Inlet
cannula 70 has a
blunt rounded end 7S for insertion into the patient's heart and a plurality of
inflow ports
80 disposed in the side v~alls adjacent the blunt rounded end 78 to pennit
inflow of blood
from the chamber of the heart. Outlet carulula 72 has an end 82 defining a
bend therein
which facilitates passage through a major vessel, e.g., aorta. End 82 lnay be
straight as
well. End 82 defines an outflow port 84 (shown in phantom) to pcnnrt blood to
exit the
outflow tube 72 under pressure. Inlet and outlet cannulas (tubes) 70, 72 arc
also
preferably 111adC Of a flexible material.
Connector 74 is a straight connector which retains inlet cannula 70
thereon by a friction fit. Connector 76 is a "T" connector having a female
threaded
portion 89 to which is mounted stopcock valve 86. Stopcock valve 86 is a
conventional valve having flow control handle 88 which rotates through manual
manipulation to bleed or remove air from the system on the outlet side or
section
16 of the system 10.
The system 10 further includes pressure sensor plug 90 associated
with inlet section 14. Pressure sensor plug 90 is electrically connected to
cable 92
which extends toward the remote end of inlet cannula 70 to pressure transducer
94
mounted to the outer surface of the inlet cannula 70. Pressure transducer 94
is
utilized to detect pressure within the heart chamber.
The system 10 also includes pump control plug 96 which connects to
the power source for energizing the pump 12.
Conti~ol Unit
Referring now to FIG. 10, a preferred control unit for use with the
circulatory support system 10 will be discussed. Control unit 100 functions in
controlling and monitoring the operation of the assist system and for sounding
CA 02541337 1997-10-03
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audible alarms for various conditions such as the presence of air bubbles in
the
bloodstream, low blood flow rate, and so forth. Control unit 100 is preferably
mobile to facilitate hospital use. The control unit 100 includes a
monitor/control
panel 102 which provides readouts of blood flow rate and pump speed. Panel
102.
includes a large knob 109 to allow an operator to control motor speed and
hence,
blood flow rate. Panel 102 also includes light emitting diodes, each of which
is lit
when an associated alarm condition exists. Control buttons on the front panel
enable the operator to control various functions such as re-starting the
motor. The
control unit also preferably has a rear display panel identical to that of the
front
panel for displaying the same information, so that the system parameter and
alarm
information is visible from the rear as well as from the front of the control
unit.
Blood flow rate is determined with a flowmeter/bubble detect sensor
104 clamped onto inflow tube 66. Sensor 104 shown schematically in FIG. 10
may be embodied as a conventional ultrasound flowmeter and bubble sensor
packaged as a single unit. Preferably, the electronics are shared between the
flow
sensing and bubble detection functions to minimize the electronics and size.
Generally, flow sensing is accomplished conventionally by transmitting and
receiving ultrasound signals diagonally across the cannula in both the
upstream and
downstream directions, and comparing the phase of the upstream and downstream
signals to ascertain the flow rate. The bubble detection is based on a
measurement
of the amplitude of the received ultrasound wave 'relative to the transmitted
wave.
If the amplitude of the received signal suddenly drops below a threshold, then
the
presence of an air bubble is indicated. Output signals generated by sensor 104
indicative of the flow rate and of the presence of air bubbles in the system
are
relayed hack to controller 100 via dedicated wires within harness 64.
Operating
voltage to sensor 104 is also provided on the wire harness. A suitable
flowmeter/bubble detect sensor 104 is available commercially from Transonic
CA 02541337 1997-10-03
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Systems Inc., located in Ithica, NY, Model No. H9X197. As an alternative, the
flow sensor and air bubble detectors may be embodied as separate units.
A solenoid triggered cannula clamp 118 shown schematically in hIG.
is mounted on the output tube 68 of outlet section 16. When controller 100
5 determines that the blood stream contains air bubbles, based on the output
signals
provided by sensor 104, it sends an actuating voltage on harness 64 to the
clamp
118 to cause it to clamp down on the output tube 68 to crimp the tube and
prevent
air from entering the bloodstream. One suitable clamp is shown in FIG. 10A.
With reference to this Figure, the clamp (shown in exploded view) includes
hollow
10 cylinder 1000, left clamp 1002 pivotally mounted to the cylinder 1000 about
pivot
pin 1004 and defining clamping surface 1006, and latch pin 1008 which locks
the
left clamp 1002 in the open and closed position by reception within a
corresponding opening (not shown) defined in the cylinder. A pair of finger
grips
1010 and associated finger grip pins 1012 are mounted within respect to left
clamp
1002. Finger grips 1010 and grip pins 1012 are depressed inwardly to release
latch pin 1008 to permit opening of left clamp 1002 to position output tube 68
therein. The clamp further includes right clamp 1014 and retaining bar 1016
having distal bore 1018 to receive pin 1020 of right clamp 1014 to fixedly
connect
the two components. A link mechanism 1022 is mounted toward the proximal end
of retaining bar 1016 and is fixed at its proximal end to retaining bar 1016
via pin
A and at its distal end to stationary support plate 1024 via pin B.
Support plate 1024 is mounted to the proximal end of cylinder 1000
and defines an axial opening to permit reciprocal movement of retaining bar
1016.
A solenoid 1026 is mounted adjacent link mechanism 1022 and includes solenoid
plunger f028 which moves upwardly~upon actuation to engage link mechanism
1022, more particularly, pin C of the link mechanism 1022, to actuate the link
mechanism to drive retaining bar 1016 distally. The clamp further includes a
CA 02541337 1997-10-03
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handle mechanism 1030 which resets the link mechanism 1022 to its rest
position.
In the drawing, link mechanism 1022 is shown in the actuated position. Prior
to
actuation, the link mechanism 1022 is in an overtoggled position (where the
links
of the linkage mechanism are in linear alignment). wlth the plunger 1028
resting on
S pin C. When a bubble is detected, the clamp is actuated which drives
solenoid
plunger 1028 of the solenoid 1026 upwardly, tripping the link mechanism 1022
to
the position shown in FIG. IOA. During movement to this position, link pin A
drives retaining bar 1016 and right clamp 1014 distally to thereby clamp tube
68
between left clamp 1002 and the right clamp 1014. To reset, the handle
~ mechanism 1030 is pulled rearwardly. As the retaining bar 1016 is pulled'to
the
right, the linkage mechanism 1022 will again over toggle ready to be tripped
by
the solenoid plunger. Another clamp suitable for this use is disclosed in U.S.
Patent No. 4,524,802 to Lawrence.
Referrinb again to FIG. 10, also included within wire harness 64 are
wires that are routed to pressure sensor plug 90 (FIG.1) which, in turn, is
connected to wire 92 and pressure sensor 94 disposed at the distal end of
inlet
cannula 70, typically in proximity to the patient's. heart. (The wires and
sensor
plug 90 are not shown in FIG. 10 for ease of illustration). These wires carry
operating voltage to the pressure sensor 94 from control unit 100. The
pressure
sensor 94 provides an output signal representing the pressure sensed (also
referred
to herein interchangeably as "inlet pressure" of the pump 12). This output
signal
is routed to control unit 100 via wire harness "h". If inlet pressure is too
low,
motor speed is reduced to prevent suction occlusion.
With reference now to FIGS. 11 (A-C) and 12, further details of the
components of control unit 100 will be discussed. As shown in FIG. I 1A,
control
panel 102 of the control unit includes LEDs 108a to 108i arranged in a
"traffic
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status board" type layout. Push-button switches 124-134 are located at the
bottom
of the panel. A large dial 109 is manually rotatable to set motor speed.
Readouts
of measured motor speed in revolutions per minute (RPM) and measured blood
flow rate in liters per minute (LPIvi) are digitally displayed directly above
the dial.
FIGS. 11B and 11C show respective front and rear perspective
views of control unit 100. Unlike conventional hospital equipment, control
unit
100 is embodied in the general shape of a long solid rectangle, with an
exemplary
height of about 48-50 inches, preferably, 54.5 inches, a width of about 7-12
inches, preferably, 9.7 inches, a thickness of only 3-7 inches, preferably,
S.5
inches, and with a suitable base support 112, preferably on wheels. Hence,
control
unit 100 is ergonomically designed to occupy a minimal amount of operating
room
space. Also, the height of the display panel 102 relative to the base support
is
high enough to prevent obstruction of the panel by the patient lying on the
adjacent
operating table. Base support 112 has side portions 115 that are approximately
.
flush with the sides 123 of the main rectangular body of the control unit to
conserve space. The front and rear portions of the base support each protrude
about six inches from the main rectangular body. A handle 113 is provided on
the
front portion of the solid rectangular body.
A display panel 103 of preferably the same display format as the
front panel 102 is provided on the rear of control unit 100, so that the alarm
LEDs, motor speed and flow rate are visible from the rear as well as from the
front of control unit 100. As such, visibility of the information by several
personnel is facilitated. The motor speed control dial and push-button
switches
124-134 are omitted from the rear display. Display panel 103 is shown in more
detail in FIG. 11D.
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Refernng to FIG. 12, control unit 100 includes a Control central
processor unit (CPU) core 150 which receives input signals from various
circuit
components within the control unit and within pump 12, and, in response,
provides
appropriate output signals to implement a host of functions. A Display CPU 160
.
S acts as an interface between Control CPU core 150 and each of the push-
button
switches 124-132, LEDs 108(a-i) and the motor speed and flow rate displays. A
Main Motor Controller/Driver 170 provides the drive power to motor 60
responsive to a pulse width modulated (PWM) signal from Control CPU core 150.
A back-up Motor Controller/Driver 180 is provided to control the motor in a
manual mode during emergency situations, for example.
A simplified block diagram of Control CPU core 150 is presented in
FIG. 13. A processor 202 such as Motorola MC 68332 communicates with the
peripheral components such as Display CPU 160 by means of a Universal
Asynchronous Receiver/Transmitter (DART) 204. Processor 202 contains a Time
Processor Unit or PWM converter 212 which is used to generate a PWM signal
for application to motor controller/driver 170 to control motor speed.
Alternatively, a digital to analog (D/A) converter may be coupled to processor
202
and would provide an analog output voltage to control motor speed responsive
to a
digital word from processor 202. Control CPU core 150 and Driver CPU 160 are
in constant communication via UART 204. (Display CPU 160 utilizes a similar
UART therewithin). Each time Control CPU core 150 sends a "display" message,
the Display CPU responds with a °key" message to indicate the status of
the key
presses. Typically this "key" message will indicate that no keys have been
pressed
and imply that the previous message was received. All messages may contain a
checksum such that exclusive-OR of all the bytes results in 0x00. The Control
CPU core and Display CPU may communicate using standard communications
protocols, e.g., at 9600 baud, with even parity, seven data bits, one stop bit
and
CA 02541337 1997-10-03
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without handshaking lines. Control CPU 150 also includes SRAM 208, e.g., 256
Kbit or higher, which may be used to store measured data as well as for
storing
parameters during computations performed by processor 202. Processor 202 also
retrieves various parameter information such as threshold data stored in
optional .
EPROM 210 (e.g. 64. Kbit x 16) or within flash memory 206.
In operation, referring again to FIG. 12, depression of AC power
switch 137 switches AC line voltage to main power supply I72 as well as to
back-
up power supply 174, each of which rectify the AC to provide DC output
voltages
(e.g. 8-15V DC) for powering the various circuit components of the system.
Main
power supply 172 also supplies voltage to a battery charger circuit 171 which
charges battery 176. A switch 179 detects voltage output from main power
supply
172 and, if it is within a predetermined voltage range, switches this voltage
to
output line 187. If switch 179 detects that the voltage output from power
supply
172 is out of range, it switches voltage from battery 176 to output line 187.
In
either case, the voltage output on line 187 is provided to a push-button
controlled
relay 134. Likewise, switch 181 detects voltage from back-up power supply 174,
and if this voltage is within the predetermined range, it switches the voltage
to its
output line 183. Otherwise, switch 181 switches the battery voltage from
battery
176 to its output line 183. Switches 179 and 181 are preferably diode
switches.
When relay 134 is activated, the DC voltages on lines 183 and 187
are switched to respective output lines 203 and 207. The voltage on these
lines are
provided as main power to CPU core 150 and CPU 160 and other circuit
components of control unit 100. Each circuit component receiving main power
will
utilize the operating voltage from either line 207 or 203.
' Isolation power supply 190 includes a DC to DC converter to
convert the voltage on line 207 (if present) to a higher voltage (e.g., 24V
DC) to
provide isolated power. The purpose of the isolated power is to diminish the
CA 02541337 1997-10-03
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possibility of electric shock to the patient undergoing treatment. As such,
the
isolated power is supplied to the circuit components which are directly
coupled. to
sensors which may contact the patient or the patient's blood. Hence, isolated
power is supplied to Motor Contro11er1Driver 170, pressure transducer 94, flow
,
rate/bubble sensor 104, cannula clamp 118, and optional motor speed sensor 61.
The main power at the output of switch 134 is supplied to the remaining
circuit
components of the control unit.
When relay 134 is activated, output voltage on line 203 is also
provided to back-up isolation power supply 182, which provides back-up
isolation
power to back-up Motor Controller/Driver 180 and to the engage back up switch
132.
A mufti-channel AID converter 111 (e.g., eight channels) is coupled
to the battery 176 and to output lines 203 and 207, and converts
the,respective
voltages at those points to digital output signals which are supplied to CPU
core
150. From the digital signal associated with the battery, CPU core 150
determines
whether the battery voltage is below a predetermined threshold. If so, it
commands Display CPU 160 to light the "Low Battery" LED on the display. CPU
core 150 also determines from the digital outputs whether the battery is in
use. If
it is, CPU core 150 provides a corresponding alarm command to CPU 160, which
then causes the "Battery in Use" LED 108i to light.
AID Converter 111 is also coupled .to motor speed dial 109 and
provides CPU core 150 with a digital output indicative of the dial position.
In
response, CPU core 150 outputs a PV~M signal S~ (produced by the PWM
converter therein) to Motor ControllerlDriver 170 through opto-coupler array
I75.
This optd-coupler array is used for isolation purposes to prevent voltages
from
within CPU core 150 from accidentally causing electric shock to the patient.
Other isolation techniques such as transformer-coupled isolation may
alternatively
CA 02541337 1997-10-03
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be used. Motor Controller/Driver 170 includes processing and drive circuitry
to
vary the drive voltage provided to motor 60 on leads 64a responsive to the PWM
of signal S~, in order to control motor speed and starting or stopping of the
motor.
If the "engage back-up" switch 132 is depressed, then Back-up
Motor ControllerlDriver 180 is utilized to drive the motor 60. The Back-up
Controller/Driver 180 does not receive motor control signals from CPU core
150,
but rather, it is directly coupled to the motor speed dial 109 and controls
motor
speed in accordance with the dial position. Switch 132 switches the voltage
output
from the appropriate Controller/Driver 170 or 180 to motor 60 via lines 64a.
Thus, the "engage back-up" switch 132 is utilized when the operator desires to
override the automatic control by the CPU core such that the motor speed is
controlled manually. This manual operating mode is useful in emergency
situations when the control unit cannot properly control blood flow under CPU
core control.
A feedback EMF signal from the motor coils is provided back to
both Controller/Driver 170 on line 64b and to Controller/Driver 180. The
processor within Controller/Driver 170 or 180 determines the actual motor
speed
based on the feedback EMF signal, compares the actual speed with the desired
speed according to signal S~ (or according to the dial 109 position directly
when
the back-up ControllerlDriver 180 is in operation), and adjusts the drive
voltage
provided on lines 64a to.obtain the desired speed within a predetermined
tolerance.
The actual measured. motor speed is continually or periodically communicated
by
Controller/Driver 170 to the Control CPU core 150 as signal SF. Control CPU
core 150 in turn transmits the motor speed information to Display CPU 160.to
display the same on control panel 102.
CA 02541337 1997-10-03
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Both Controller/Drivers 170, 180 include a current limiting circuit
which limits current drawn by motor 60 to a predetermined maximum. If the
maximum current is reached, this is indicative of the motor 60 or pump 12
malfunctioning. When maximum current is reached, Motor Controller/Driver 170'
forwards a signal S; back to the Control CPU core I50 indicative of this
condition.
CPU core 150 responds by sending a message to Display CPU 160 to light the
"pump" LED 108d and sound an audible alarm. However, this condition does not
stop the motor. (The Back-up Controller/Driver 180 may also be designed to
communicate this information back to CPU core 150).
~ Suitable controller chips which may be utilized within
Controller/Drivers 170 and 180 to perform many of the above-described
functions
are commercially available from several manufacturers. Examples include U.S.
Philips Corporation, located in Sunnyvale, CA (part No. Philips TDA-5140) or
from Micro Linear Corporation, San Jose, CA (part No. Micro Linear 4425).
Both of these controller chips operate as sensorless controllers which monitor
the
feed-back EMF from the motor coils to determine and control the motor speed.
As an alternative, a controller used in conjunction with a motor speed sensor
61,
e.g. a Hall effect sensor, could be employed. In this embodiment, feed-back
EMF
would not be used. Sensor 61 is positioned adjacent motor 60 and provides a
signal SM indicative of the sensed- motor speed on line 64c. This signal is
routed
to Motor Controller/Drive I70 (or 180) which derives the measured motor speed
from the signal and their adjusts the voltage drive or pulse width modulation
(PVVM) signal to the motor accordingly to adjust motor speed. Signal SM is
also
provided to Control CPU 150 through opto-coupler 191 to enable the
instantaneous
motor speed to be displayed on the display panel as in the case above.
CA 02541337 1997-10-03
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Attention is now turned to flow rate/bubble sensor 104. As
discussed above, this sensor provides measurement of blood flow rate and
moiutors
for bubbles in the blood, preferably using ultrasound. The existence of any
bubbles greater than a predetermined size can cause a serious medical
condition
~ since air is being pumped into the bloodstream. ~Ience it is desirable for
the,
operator/surgeon to be immediately apprised of a bubble condition whereupon it
can be effectively remedied as soon as possible. In accordance with the
present
disclosure, if a bubble condition is sensed, the pump is immediately caused to
shut
down to allow the surgeon to instantly remedy the~bubble condition such as by
sucking out the bubble with a syringe. Following motor shut-down due to a
bubble condition, the motor does not start again automatically, but must be
manually restarted by depressing the restart pump button 130. In addition,
immediately upon the detection of a bubble condition, control unit 100 sends a
command to a clamp control circuit 222, which responds by providing an
actuation
voltage to the cannula clamp 118. The actuation voltage causes clamp 118 to
clamp down on the output tube 68, thereby crimping the cannula or tube and
preventing air bubbles from entering the patient's bloodstream.
In operation, operating voltage is supplied to flowlbubble sensor 104
on line 64f. Sensor 104 outputs a flow rate signal S,~ and a bubble sense
signal SH
on lines 64e corresponding to the associated conditions within inlet cannula
14.
The sensor output signals are supglied to Flow Rate/Bubble Detect Circuit 140,
e.g., a circuit board product available from Transonic Systems Inc., model
T109
circuit board. Circuit 140 communicates the sensor output signals Sa and S~ to
Control CPU 150 in a suitable format, and also provides control signals to
sensor
104 to control its operation.
CA 02541337 1997-10-03
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If signal Se indicates the presence of a bubble condition, Control
CPU 150 immediately changes the voltage level of motor control signal S~ (or
transmits another signal) to command a shut-down of motor 60, whereby Motor
Controller/Driver 170 causes motor 60 to cease rotation. Contemporaneously, .
Control CPU 150 sends a command signal to clamp control circuit 222 to
initiate
clamping by clamp 118 by providing a momentary actuation voltage thereto: An
alarm signal is sent to Display CPU 160 which causes the "Bubble" LED 108b and
the "re-start pump" LED 136 to light or blink. In addition, CPU 150 activates
audible alarm circuit 184 by outputting a tone signal ST and a volume signal
SV,
The tone signal enables circuit 184 to produce audible output through speaker
164.
The volume signal causes the audible output to be camped up to avoid startling
the
surgeonslnurses. (It is noted here that the audible alarm circuit 184 is
automatically activated by CPU 150 whenever any of the other alarm LEDs 108a -
108i are lit. The "silence alarm" button 128 enables an operator to silence
the
audible alarm each time it occurs for any of the alarm conditions).
When the motor is shut down in correspondence with the bubble
alarm, the operator may attempt to remove the bubbles from the cannula such as
by sucking them out with a syringe. Thereafter, to restart the pump, the
operator
manually resets the cannula clamp, and depresses the Restart pump button 130,
which causes the bubble alarm to be extinguished and the motor to be re-
started to
a speed in accordance with the manual dial 109.
In an alternative embodiment, the cannula clamp 118 and the
associated clamp control circuit 222 are eliminated. In this case, a bubble
alarm
condition will still stop the motor as described above to permit the bubble
condition to be remedied such as with a syringe. The motor will then be re-
started
only after the Re-start pump button 130 is manually activated.
CA 02541337 1997-10-03
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The flow rate signal SFR outputted by sensor 104 is routed to CPU
150 in suitable format by detect circuit 140. CPU 150 routes the flow rate
information to Display CPU 160 which causes it to be displayed on the panel
102.
Control CPU 150 performs a software routine wherein the flow rate is compared
to a threshold value "L1" stored in memory within the CPU. Tf the flow rate
drops
below "L1" for a predefined time period, e.g., below 2 LPM for more than one
second, CPU 150 communicates a message to CPU 160 to light the "Low Flow"
alarm LED 108e and sound an audible alarm.
Optionally, control unit 100 also monitors for flow blockage and
generates a flow blockage alarm via a dedicated LED (not shown) and audio
alarm
if blockage is detected. In this case, CPU 150 stores flow rate data
continuously
and evaluates whether the flow rate has dropped unexpectedly in the absence of
the
speed, dial 109 being moved (after the flow rate having been above a
predetermined
threshold such as one LPM). If the flow rate drops by a predetermined amount
or
percent, e.g., by more than 30% in less than two seconds, then the flow
blockage
alarm is activated. The flow blockage alarm is extinguished when the flow rate
rises above a threshold, e.g.; above one LPM.
Control unit 100 also communicates with pressure transducer 94 to
ascertain the measured pressure in the transducer's location, e.g., in
proximity to
or' within the atrium, or alternatively, within the inlet cannula in a
position closer
to pump _ 12. Pressure transducer 94 may be a conventional miniaturized
transducer available commercially, e.g., from Ohmida Medical Devices, located
in
Madison, WI. Alternatively, transducer 94 is embodied within a housing clamped
to the outer surface of the inlet cannula, e.g., in proximity to the pump.
Pressure
transducer 94 receives operating voltage via leads 64d (which run within the
outer
sheathing of inlet cannula 14) and outputs a signal SP indicative of the
pressure
back to the control unit on another one of leads 64d. This signal is digitized
and
CA 02541337 1997-10-03
-25-
received by opto-coupler 197 and routed through interface circuit 193 to CPU
150
in suitable format. CPU 150 includes a software routine that stores measured
pressure data and determines whether the instantaneous pressure has dropped
below a predetermined threshold "P1", e.g., to less than 2mm of mercury. If
so, a
message is outputted to CPU 160 to light the Low Inlet Pressure LED 108f.
Contemporaneously, CPU 150 sends a command to Motor ControllerlDriver 170
to automatically reduce the motor speed at a predetermined rate of reduction,
in an
attempt to automatically bring the pressure back. Motor speed continues to
drop
until the pressure rises above P1 (or above a higher threshold) for more than
a
predetermined time period, e.g., for more than 1.2 seconds. When this
condition
is satisfied, motor speed is then ramped up to a speed in accordance with the
speed
dial 109. (As an alternative, the motor speed is reduced to a predetermined
speed,
or by a predetermined amount, and is maintained at that lower speed until the
pressure rises above a threshold, which is followed by motor speed ramp-up).
It is noted that control unit 100 may include means to manually
calibrate or "zero" the pressure measurement. That is, when CPU 150 detects
that
the "Set Zero Pressure" push-button 124 on the panel is depressed, it reads
the
instantaneous value of pressure as outputted by transducer 94 and stores that
value
as the offset to be used whenever the pressure transducer is read. The
pressure
transducer is preferably zeroed in this manner. by the operator each time the
control unit is turned on and prior to the cannulas 14, 16 being attached to
the
patient.
Control unit 100 preferably includes a test mode to verify proper
operation of the motor. The test mode is activated by depression of "Test"
push=
button 1'26 on the panel, whereupon CPU 150 will send a command to Motor
ControllerlDriver I70 to force motor 60 to run for, e.g. 10-15 seconds at
varying
speeds. In the test mode, the motor will run regardless of any alarm
conditions.
CA 02541337 1997-10-03
-26-
The alarm LEDs will still light, but the alarms will not be audible or prevent
the
motor from running during the test mode.
In addition, a Power On Self test feature is provided whereby the
control unit undergoes a self-test under the control of CPU 150 whenever power
is
initially fumed on. If the CPU detects any error within itself or any of its
peripherals, CPU 150 will not allow the unit to run. The self test preferably
includes a RAM test to determine if the RAM is accessible and a ROM test to
ascertain that the check sum of the code has not changed. A test for invalid
readings from any sensor is also included, as well as a
connectivitylcontinuity test
and a display test. If there are any errors, the LED on the front panel
corresponding to the faulty circuit component will be lit and all dashes
displayed
on the flow rate and motor speed displays. If there are no ermrs, none of the
LEDs will be lit and all zeroes are preferably displayed on the flow rate and
motor
speed displays.
During system operation, checks are continually performed on
various components to verify proper continuity and operation, and an alarm is
generated if a fault is detected. For instance, the "flow sensor" LED 108c on
the
front panel is lit and an audible alarm is sounded if the flow sensor 104 is
determined to be electrically disconnected from control unit 100, or if the
bubble
amplitude readings are below a predetermined threshold, indicating improper
mounting or contact between the flow sensor and the tubing. The clamp control
circuit 222 continually samples the continuity of the cannula clamp 118, and
reports faults to the CPU 150. The "clamp" LED 108a is lit and an alarm
sounded if continuity is deemed inadequate. The "electronics" LED 1088 is lit
and
a buzzer activated if the control CPU 150 is not receiving adequate messages
from
the display CPU 160, or if any power supply voltages are out of specification.
The control unit 100 also includes a connector (not .shown) within the unit
housing
CA 02541337 1997-10-03
-27-
to enable connection to a personal computer (PC) to aid in the testing of the
control unit. Communication with the PC may be transferred at, e.g., 9600 baud
with no parity, eight data bits, one stop bit anf without handshaking lines.
Referring now to FIGS. 14A and 14k3, a simplified flow diagram
illustrating operation of a software routine running on Control CPU core 150
is
presented. Upon manual activation of the power switches (step 302) the Control
CPU 150 performs the above-described self test (step 307). If any errors are
detected in step 308 the motor is disabled (step 309), the LED 108 on the
panel
associated with the faulty component will be lit (step 310) and the unit will
be non-
functional until the problem is corrected. Also, the motor speed and flow rate
displays will show all dashes (step 311). If no errors are detected, the CPU
core
then determines in step 312 if the battery is in use or the battery is low,
based on
the digital outputs from A/D converter I11. If either condition is present,
the
corresponding LED is activated in step 313 by means of a command sent to
Display CPU 160.
Next, CPU 150 determines the speed dial position in step 314 based
on the output of converter 111, and forwards control signal S~ to Motor
Controller/Driver 170 to run the motor at the desired speed. With the motor
running, bubble sense signal Sg, flow rate signal SPR, pressure sense signal
SP,
motor speed sense signal SM (or SP) and current limit signal Si are
transmitted to
CPU 150 by the respective circuit components aS discussed above (step 316).
These signals may be received by the DART within CPU 150 and stored in the
SRAM and/or flash memory. The motor speed and flow rate are determined based
on SM (or Sp) and Sue, respectively, and commands are sent to the Display CPU
to
display the same on the display panel. The Control CPU then evaluates the
bubble
signal Se (step 318). If a bubble is determined to be present, the motor is
shut
down and the bubble alarm activated (step 320). At this point the CPU core
CA 02541337 1997-10-03
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detects whether or not the Re-start button has been pressed in step 322. When
it is
depressed, the bubble alarm is de-activated (step 323) and the software flow .
returns to step 314 where the motor is started again.
If in step 318 there is no bubble detected greater than a
predetermined size, the next step is to ascertain whether the blood flow rate
is less
than the threshold level L1 (step 324). If so, the low flow rate alarm is
activated
in step 326. The alarm remains activated unless the flow rate rises above a
threshold L2, e.g., 10% higher than LI (steps 327, 329). The low flow rate
condition does not stop the motor.
Next, in step 340 (FIG. 14B) the CPU core evaluates whether the
inlet pressure has dropped below the threshold P1 (in mm Hg). If it has, the
low
inlet pressure alarm is activated (step 342) and the motor speed is
automatically
reduced in step 344. The motor speed reduction is carried out at a
predetermined
rate of reduction. If the inlet pressure is still below PI in step 345, then
the flow
returns to step 344 where the motor speed is reduced further. The motor speed
is
incrementally camped down in this manner until the inlet pressure rises above
P 1.
When it does rise above P1, the motor speed is maintained at the latest
reduced
speed in step 346. Then, in step 347, if the inlet pressure is above P1 for a
specified time interval, e.g. for 1.2 seconds, the motor speed is camped up in
step
349: Otherwise, the flow returns to step 345. Once the motor speed is tamped
up
in step 349 to a speed in accordance 'with the motor speed dial 109, the
pressure
alarm is de-activated in step 350 and the flow returns to step 370.
The next step (step 370) is to determine if the motor current is at the
limit, based on the signal Si pmvided by the Motor Contmller/Driver 170 or
180.
If the limit is reached, the Pump alarm is turned on in step 375, otherwise,
it is
commanded off in step 380. The software flow then returns to step 312 where
the
diagnostic routine is repeated.
CA 02541337 1997-10-03
-29-
Preferred Arrangements for Connecting the Sunnnrt System
Preferred arrangements for connecting the support system 10 will,
now be discussed. With reference again to FIG. 10, support system 10 is
illustrated for use with an open (full medial) sternotomy which involves the
splitting of the sternum bone to gain access to the heart. As discussed above,
support system 10 is contemplated for use in assisting the left side of the
heart
while the blood flows through .the right side to deliver blood to the lungs
for
oxygenation. As depicted, flow pump 12 of support system 10 is sufficiently
small
to be placed directly on the upper chest of the patient away from the sternal
area
and may be secured to the chest with conventional medical tape or secured'to
the
drape with conventional surgical clips. Inflow and outflow sections 14, 16 are
then appropriately positioned adjacent the chest cavity to access the heart
and/or
major blood vessels. With reference now to FIG. 15, one arrangement for
connecting the system is described. Inlet cannula 70 of inlet section 14 is
introduced through the heart wall and passed through the mitral valve "MV"
with
the inflow ports 80 positioned in the left ventricle "LV" as shown. Outlet
cannula
72 is inserted through the aorta wall with the use of end portion 82 with the
outflow port 84 positioned in a downstream position within the aorta "A". Upon
operation of the system 10, blood is withdrawn from the left ventricle "LV"
through inflow ports 80 of inflow cannula 70 and directed to the pump 12. Pump
12 imparts mechanical pumping energy to the blood and directs the blood under
pressure through outflow cannula ?2 and into the aorta "A", thus assisting the
functioning of the left side of the heart. The blood is circulated throughout
the
body via the body's circulatory system and through the right side of the heart
to
the patiedt's lungs for oxygenation. During operation, monitoring, checking
and
controlling the system 10 is performed with control unit 100 to calculate flow
rate,
pressure within the heart, air bubble detection, etc... as discussed
hereinabove.
CA 02541337 1997-10-03
-30-
FIG. 16 illustrates an alternate method whereby the inflow cannula
70 accesses the "LV" through an incision formed in the wall of the heart.
FIG. 17 illustrates another alternate method of application of
circulatory support system 10. In accordance with this method of application,
inflow cannula 70 is introduced into the left ventricle "LV" through the
region
adjacent the juncture of the pulmonary veins "PV" (left or right) and passed
through the mitral valve "MV" with the inflow ports 80 of the tube 70 located
within the left ventricle "LV".
FIG. 18 illustrates an alternate method of application where two
support systems are used for total heart bypass. The support system utilized
for
bypass of the left side of the heart is identical to that described in
connection with
FIG. 15. The support system utilized for right heart bypass has its inflow
cannula
70 inserted through the heart wall with the inflow ports 80 positioned in the
right
ventricle "RV". The outflow cannula 72 is positioned in the pulmonary aorta .
"PA" in downstream orientation as shown. In this application, the lungs are
still
utilized to oxygenate the blood.
FIGS. 19-20 illustrate yet another method of application of the
circulatory support system. In accordance with this percutaneous approach,
inflow
cannula 70 is percutaneously inserted through subclavian artery to the aorta
"A"
and advanced through the aortic valve "AV" with the inflow ports 80 of the
tube
14 positioned within the left ventricle "LV". Inflow cannula 70 has expandable
membrane 98 (e.g., a balloon) positioned about its periphery to occlude the
aorta
"A". A second catheter 99 (as shown) may be coaxially mounted about the
cannula 70 to provide the inflation fluids to expand membrane 98 as is
conventional in the art. The second catheter may include a connector 99a,
e.g., a
Luer connector, for providing the inflation fluids to be passed to membrane
98. It
is also envisioned that inflow catheter 14 may have a separate lumen extending
CA 02541337 1997-10-03
-31-
therethrough and terminating in a port 99b and port 99c to permit the
introduction
of cardioplegia solution within the heart to temporarily discontinue the
pumping
function of the heart, and/or for venting the-left ventricle. Outflow cannula
70 is
inserted, preferably, percutaneously within the femoral artery and advanced
into
the descending aorta "a".
In application, flexible membrane 98 is expanded to isolate the left
side of the heart. The support system 10 is actuated to draw blood from the
left
ventricle "LV" through inflow ports 80 and into inflow cannula 70. The blood
is
directed through inflow cannula 70 and is subjected to the pumping energy of
portable pump 12. The blood is returned through tube 68 and outflow cannula 72
and into the descending aozta "a". During use, cardioplegia fluid or venting
capabilities may be introduced via inflow catheter tube 14 and port 99b to be
deposited from port 99c as described above.
With reference now to FIG. 21, another arrangement for connecting
the system is described. Inlet cannulated tube 14 is introduced through the
heart
wall with the inflow ports 80 positioned in the left atrium "LA" as shown.
Outlet
cannula 72 is inserted through the aorta wall with the use of end portion 82
with
the outflow port 84 positioned in a downstream position within the aorta "A" .
Upon operation of the system 10, blood is withdrawn from the left atrium "LA"
through inflow ports 80 of inflow cannula 70 and directed to the pump 12. Pump
12 imparts mechanical pumping energy to the blood and directs the blood under
pressure through outflow cannula 72 and into the aorta "A", thus assisting the
functioning of the left side of the heart. The blood is circulated throughout
the
body via the body's circulatory system through the right side of the heart to
the
patient's lungs for oxygenation.
CA 02541337 1997-10-03
-32-
FIG. 22 illustrates another alternate method of application of
circulatory support system 10. In accordance with this method of application,
inflow cannula 70 is introduced into the left atrium "LA" through the region
of the
juncture of the pulmonary veins "PV" with the inflow pons 80 of the cannula 70
.
located within the left atrium "LA". _
FIG. 23 illustrates an alternate method of application where two
support systems are used for total heart bypass. The support system utilized
for
bypass of the left side of the heart is identical to that described in
connection with
FIG. 21. The support system utilized for right heart bypass has its inflow
cannula
70 inserted through the heart wall with the inflow ports 80 positioned in the
right
atrium "RA". The outflow cannula 72 is positioned in the pulmonary aorta "PA"
in downstream orientation as shown. In this application, the lungs are still
utilized
to oxygenate the blood. Alternatively, right bypass can be effectuated by
accessing
the right ventricle with inflow cannula 70 or left bypass can be effectuated
by
accessing the left ventricle with any of the arrangements described above.
Thus, the circulatory support system 10 of the present disclosure
provides for temporary short term heart support (either partial, e.g., left
heart
assist, or full support) of a patient. Set-up and management of the system
requires
relatively minimal effort. The entire system 10, i.e., the pump 12 including
the
motor 60 and associated tubing, can be manufactured cost effectively to be
disposable. The features of the control unit, including the bubble detection,
flow
rate detection, automatic motor shutdown and clamping of the outlet cannula in
case of detected bubble, various visible and audible alarms, and so forth; are
particularly tailored to address the needs of an axial flow pump system. The
control uhit is also ergonomically designed to occupy a small amount of
operating
room space and to facilitate use in the operating room.
CA 02541337 1997-10-03
-33-
While the above description contains many specifics, these specifics
should not be construed as limitations on the scope of the disclosure, but
merely as
exemplifications of preferred embodiments thereof. For example, one or two of
the aforedescribed pumps can be placed in other locations of the body, via
other
access areas, in addition to those desczibed above. Also, the pumps) can be
utilized during the "window° approach to bypass surgery as well as
during .
minimally invasive bypass surgery. Those skilled in the art will envision many
other possible variations that are within.the scope and spirit of the
disclosure as
defined by the claims appended hereto.
