U.S. patent number 3,656,873 [Application Number 05/087,487] was granted by the patent office on 1972-04-18 for pulsatile by-pass blood pump.
Invention is credited to Peter Schiff.
United States Patent |
3,656,873 |
Schiff |
April 18, 1972 |
PULSATILE BY-PASS BLOOD PUMP
Abstract
A by-pass pump system especially adapted for use in assisting or
temporarily replacing the circulatory function of the heart in
which a pair of highly elastic collapsible containers are coupled
to one another through a resilient flap valve. Each flexible
chamber is positioned within an associated housing whose interior
pressure is regulated to control the expansion and contraction of
the flexible housings. Blood enters the first of said chambers
causing the chamber to fill when the blood pressure is greater than
the pressure of the surrounding housing. The one-way valve
mechanism enables the blood filling the first flexible chamber to
enter the second flexible chamber when the interior pressure of the
second flexible chamber is lower than that of the first chamber.
Conversely, if the pressure within the interior of the second
resilient chamber is greater than that within the first flexible
container, the one-way valve structure prevents reverse flow.
Pneumatic means is coupled to the housing surrounding the second
flexible container to cause the blood to be pumped through an
outlet opening provided in the second flexible container in order
to enter into the arterial system at a rate substantially equal to
the normal pumping rate of the patient. A second one-way valve
mechanism is provided in the aforesaid outlet opening to prevent
reverse flow. The action of the flexible containers upon the blood
is non-occlusive due to the pneumatic controls utilized, as well as
the nature of the design of the chambers. The one-way valve
mechanisms may alternatively be of a flap valve form or a form in
which the closure portions of the valve are highly elastic to
permit ready flow of the blood in a first direction while
preventing flow in the reverse direction. In one preferred design
the one-way valve structures cooperate with their associated valve
mounts to provide positive reliable operation and simple
straightforward removal and insertion.
Inventors: |
Schiff; Peter (Schwenksville,
PA) |
Family
ID: |
22205482 |
Appl.
No.: |
05/087,487 |
Filed: |
November 6, 1970 |
Current U.S.
Class: |
417/395;
128/DIG.3; 417/540; 623/3.1 |
Current CPC
Class: |
A61M
60/43 (20210101); A61M 60/113 (20210101); A61M
60/892 (20210101); A61M 60/268 (20210101); A61M
60/896 (20210101); A61M 60/894 (20210101); Y10S
128/03 (20130101) |
Current International
Class: |
A61M
1/10 (20060101); F04b 043/06 (); F04b 045/00 ();
A61f 001/00 (); A61b 019/00 () |
Field of
Search: |
;417/474,475,395,540
;3/1R ;128/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Gluck; Richard E.
Claims
The embodiments of the invention in which an exclusive privilege or
property is claimed are defined as follows:
1. Means for converting a low pressure fluid flow to a high
pressure pulsatile flow comprising:
first and second flexible fluid receiving containers adapted to be
readily expanded or compressed, each container having an inlet and
an outlet port;
a first conduit connecting the inlet port of said second container
to the outlet port of said first container;
one-way valve means mounted within said first conduit;
means connecting the inlet port of said first container to receive
a low pressure fluid flow;
second conduit means connected to said second container outlet port
for delivering the output flow of said second container;
first and second chambers respectively enclosing said first and
second flexible containers;
means for maintaining the pressure in said first chamber at a
predetermined constant level;
actuator means for alternately pressurizing and depressing said
second chamber at an adjustable predetermined rate to urge fluid
delivered to said second flexible container from said first
flexible container outwardly through said second conduit in a
pulsatile manner.
2. The device of claim 1 wherein said one-way valve means includes
means adapted to permit fluid flow from said first to said second
flexible container while preventing fluid flow in the reverse
direction.
3. The device of claim 1 further comprising:
second one-way valve means mounted within said second conduit means
for permitting fluid flow from said second flexible container while
preventing fluid flow in the reverse direction.
4. The device of claim 1 wherein said valve means is comprised of a
pair of flap members diagonally aligned within said first conduit
means to form a V-shaped configuration when closed whereby said
flaps are curved near their free ends to cause engagement
therebetween only in the marginal region of said flap free ends in
the presence of reverse fluid flow.
5. The device of claim 1 wherein said valve means is comprised of a
plurality of arcuate shaped flap members diagonally aligned within
said first conduit means to form a dome-shaped configuration when
closed, whereby said flaps are provided with V-shaped flanges along
their free ends to cause engagement therebetween only in the
marginal region of said flap flanges in the presence of reverse
fluid flow.
6. The device of claim 1 wherein said flexible conduits are each
formed from a pair of thin sheets of a flexible material whose
marginal engaging portions are joined by a suitable adhesive means
to air-tightly seal said containers as well as defining their
perimeters.
7. Means for converting a low pressure fluid flow to a high
pressure pulsatile flow comprising:
first and second chambers;
a flexible membrane in each of said chambers dividing each chamber
into a fluid and non-fluid receiving compartment;
the fluid receiving compartments each having an inlet and an outlet
port;
a first conduit connecting the inlet port of one of said fluid
receiving compartments to the outlet port of the remaining fluid
receiving compartment;
one-way valve means mounted within said first conduit; input means
connecting the inlet port of said one of said fluid receiving
compartments to receive a low pressure fluid flow;
second conduit means connected to the outlet port of the remaining
one of said fluid receiving compartments for delivering the output
fluid flow of said second container;
means coupled to the non-fluid receiving compartment of said first
chamber for maintaining the pressure therein at a predetermined
constant level;
means coupled to the non-fluid receiving compartment of said second
chamber for alternately pressurizing and depressurizing the
non-fluid receiving compartment of said second chamber at an
adjustable predetermined rate to urge fluid delivered thereto from
the fluid receiving compartment of said first chamber outwardly
through said second conduit in a pulsatile manner.
8. The device of claim 7 wherein said flexible membranes are formed
of a flexible non-stretching material.
9. The device of claim 7 wherein the interior surface of the first
chamber forming a portion of said first fluid receiving compartment
has a substantially tapered configuration;
the flexible membrane of said fluid receiving compartment being
incapable of engaging the entire surface area of said tapered
surface.
10. The device of claim 7 wherein said one-way valve means includes
means adapted to permit fluid flow from said first to said second
chamber fluid receiving compartment flexible container while
preventing fluid flow in the reverse direction.
11. The device of claim 7 further comprising:
second one-way valve means mounted within said second conduit means
for permitting fluid flow from said second chamber fluid receiving
compartment while preventing fluid flow in the reverse
direction.
12. The device of claim 7 wherein said valve means is comprised of
a plurality of arcuate shaped flap members diagonally aligned
within said first conduit means to form a dome-shaped configuration
when closed, whereby said flaps are provided with V-shaped flanges
along their free ends to cause engagement therebetween only in the
marginal region of said flap flanges in the presence of reverse
fluid flow.
13. The device of claim 9 wherein the outlet port of said first
chamber fluid receiving compartment is positioned at the apex of
said tapered interior surface;
said tapered interior surface being provided with an annular shaped
rim projecting from said surface at a location intermediate said
apex and said membrane for cooperating with said member to isolate
the input connecting means from said second conduit means when the
second conduit means exerts a negative pressure upon the first
chamber fluid receiving compartment.
14. The device of claim 1 including means responsive to the nearly
total collapse of said first flexible container for deactivating
said actuator means.
15. The device of claim 7 wherein said means for maintaining the
pressure in the non-fluid receiving compartment of said first
container includes means for regulating the pressure level in said
first container in inverse proportion to the amount of blood in
said first container.
16. The device of claim 15 wherein said regulating means further
comprises an adjustable clamp provided in the inlet part of said
first fluid receiving container.
17. The device of claim 16 further comprising plunger means having
a first end resting upon the membrane of said container and a
second end extending outwardly from the non-fluid receiving
compartment of said first container whereby the length of said
second end extending beyond said first chamber is employed to
determine the adjustment of said adjustable clamp.
18. The device of claim 15 wherein said pressure regulating means
is further comprised of plunger means having a first end resting on
the membrane of said first container and a second end extending
outwardly from said first container;
said plunger means having a first opening at said second end
communicating with a second opening at a point intermediate the
first and second ends thereof whereby said second opening is sealed
by said first container when the level of fluid in said first
container is high and whereby said second opening communicates with
the interior of said first chamber when the fluid level in said
first container is low.
Description
The present invention relates to pumping systems and more
particularly to a novel non-occlusive pumping system for use as a
substitute or assistive non-occlusive blood pumping means.
BACKGROUND
During open-heart surgery or in applications where it is desired to
assist the circulatory function of a failing heart, blood is
removed from the body of a patient at a low pressure level and is
pumped into the arterial system at a higher pressure. Quite often,
portions of the normal circulatory system are by-passed in this
manner to permit surgery to be performed upon the affected parts or
organs such as, for example, the heart itself. Until recently, the
pumping function was achieved primarily through the use of a roller
pump. The characteristic of a roller pump is such as to
progressively compress an elongated length of tubing, which acts as
a conduit for blood flow, through the use of several rollers
rollingly and compressingly engaging the tubing in a successive
fashion so as to force the blood through the tube and thereby
either replace or supplement the natural heart function.
Conventional roller pumps have several disadvantages as compared to
the natural heart. Among these are the fact that the roller pump is
occlusive and thereby compresses and severely damages blood cells
by compressing the cells between the two surfaces of the tubing due
to the compressive action of the rollers upon the tubing.
Furthermore, the roller pump is a positive displacement pump having
no controlled output pressure limits or input suctions limits
situations where the tubing delivering blood to the roller pump may
become blocked for any reason. As a result, the tubing may burst or
develop an excessive vacuum condition causing nitrogen to be
extracted from the blood to an extent where the survival of the
patient becomes endangered. Continuous outflow of blood from a
conventional roller pump is undesirable since such operation fails
to emulate the pulsatile nature of the natural heart.
It is therefore most important to provide a pumping system which
most closely emulates the operation of the natural heart and which
should therefore be characterized by providing: continuous
innerflow of blood to the pump and a high pressure pulsatile
outflow; means for limiting pressure at the outflow to a safe level
even in the presence of obstructions in the outflow; means for
adjustably controlling vacuum and pressure levels at the inflow end
of the pump so as to accommodate the requirements of a particular
application or patient; means for providing non-occlusive pumping
action and a design which enables the system to be rapidly
synchronized to operate in synchronism with the operation of a
normal heart through the use of a design having low mechanical
inertia in order to greatly enhance pump response time.
The present invention is comprised of a pair of highly resilient
containers each mounted within an associated pressure controlled
housing. The flexible containers are joined through a common
connection having a one-way valve mechanism which permits fluid
flow in a first direction while preventing any reverse fluid flow.
The flexible container at the input end of the pump is permitted to
fill at a rate dependent upon the pressure differential existing
across the flexible walls of the container. Transfer of the
incoming flow from the input side container to the output side
container is a function of the pressure gradient across the one-way
valve mechanism.
The output side flexible container is provided with an outlet port
containing a second one-way valve mechanism to permit fluid flow
only in the output direction while preventing any reverse flow.
Pulsatile pumping means are coupled to an inlet port of the housing
containing the flexible container of the output side to deliver any
pulsatile high pressure output flow to the patient's arterial
system. The walls forming each of the flexible containers are quite
thin and highly resilient to provide for quick response to pressure
differentials across the flexible walls and to provide positive
non-occlusive pumping action.
In a preferred embodiment, the one-way valve mechanisms and their
associated valve mounting means are designed so as to enhance the
seating of the valve during normal operation while at the same time
providing for simple rapid removal and/or replacement of the valve
assembly.
It is therefore one object of the present invention to provide a
novel non-occlusive pumping system for use in either assisting or
by-passing normal heart function.
Another object of the present invention is to provide a novel
non-occlusive pumping system comprised of at least two flexible
chambers and pressure operated enclosures therefore which, together
with connecting one-way valve mechanisms cooperate to emulate the
operating characteristics of the natural heart.
Another object of the present invention is to provide a novel
one-way valve design for use in by-pass pumping systems of the
non-occlusive type.
These as well as other objects of the present invention will become
apparent when reading the accompanying description and drawings in
which:
FIG. 1 is a block diagram showing a total by-pass system.
FIG. 2 is a sectional view showing a by-pass pump designed in
accordance with the principles of the present invention.
FIG. 3 is a sectional view showing one of the flap valve mechanisms
of FIG. 2 in greater detail.
FIG. 4 is an exploded perspective view showing one physical form of
the pump of FIG. 2.
FIG. 5 is a sectional elevational view of another preferred
embodiment of the present invention.
FIGS. 6a and 6b are sectional and top plan views respectively,
showing one of the valves of FIG. 5 in greater detail.
FIG. 7 is a sectional view showing the details of the liners used
in FIGS. 2 and 5.
FIGS. 8 and 9 are sectional views of further embodiments of FIG.
5.
FIG. 1 illustrates a total by-pass system incorporating a blood
pump. As shown therein, blood is taken from the venous system of a
patient 1 and passes through an oxygenator 8 provided to oxygenate
the blood as a substitute for function normally performed by the
patient's lungs due to the fact that the lungs in both the right
and left side of the heart have been by-passed. The oxygenator
removes carbon dioxide and replenishes the blood with oxygen. A
pulsatile blood pump 11 receives blood from oxygenator 8 and
increases blood pressure from a pressure level equivalent to
several millimeters of mercury which is a level normally found in
the venous system of a patient, to a mean pressure of 100
millimeters of mercury which is a pressure normally found in the
arterial system of a human. The output blood flow is then passed
through a heat exchanger unit 4 provided to lower the patient's
blood temperature level for surgery and also adjustable to increase
blood temperature upon the termination of surgery. Unit 4 also
serves to add heat dissipated by the blood due to the long
extracorporeal path which the blood follows in moving through the
total by-pass system. The low temperature during surgery reduces
the oxygen consumption of the patient and therefore permits the
patient to safely survice a substantially long time interval during
which the mechanical by-pass system provides its supportive
functions. The blood, after passing through heat exchanger 4, is
returned to the arterial system of the patient.
Desirable by-pass pump characteristics, which can clearly be seen
to closely emulate the properties of a natural heart can be
summarized as follows:
1. The pump should provide a continuous venous inflow and a high
pressure pulsatile arterial outflow.
2. The pump should provide safe limiting pressures at the outflow
end even in the presence of obstructions which may occur at the
outflow.
3. The pump should provide a means for readily adjusting and
controlling vacuum and pressure levels at the inflow side to enable
the pump to function at a variety of filing modes to suit the
requirements of various oxygenators and by-pass systems. Examples
are gravity filling, filling at a controlled vacuum, and filling at
a controlled inlet pressure as is required by some membrane
oxygenators of recent design.
4. The pump should provide non-occlusive blood flow since any
contact between two occlusive surfaces may cause excessive blood
cell damage due to abrasion and/or due to the non-compatible nature
of present synthetic materials with blood.
5. The pump must exhibit a low blood damage or hemolysis factor
which may be accomplished through a design incorporating low blood
turbulance, selection of proper materials and a non-occlusive
construction.
6. The driving mechanism must be capable of being synchronized to
the operation of the natural heart with sufficient rapidity to
provide proper phase relationships to the heart which requires a
design of low mechanical inertia and small delay so as to prevent
pump response from being either too slow or too late. This design
characteristic generally restricts the pump driving means to
hydraulic or pneumatic operation as opposed to mechanically driven
devices.
The design objectives may be accomplished by the pulsatile by-pass
pump shown in schematic fashion in the cross-sectional view of FIG.
2.
The pump assembly of FIG. 2 is comprised of an "atrium" chamber 17
and a "ventricle" chamber 30 which are similar in design and
function to corresponding portions of a natural heart. The venous
return line 14 which may be coupled to the patient through any
suitable manner (or through any oxygenator 8, as shown in FIG. 1)
is coupled into the interior of atrium 17 through an inlet port
17a. Incoming blood passes through atrium 17 and a common conduit
22 containing one-way flap valve 21 so as to enter ventricle 30
through its inlet port 30a. The blood leaves the ventricle 30
through outlet port 30b and conduit 28 which contains one-way flap
valve 26. Ventricular conduit 28 may be connected to the arterial
system of the patient (or heat exchanger unit 4, as shown in FIG.
1).
The valve mechanisms 20 and 26 are so arranged to respectively
permit free flow in the directions from inlet conduit 14 to outlet
conduit 28 while preventing reverse flow therethrough.
Atrium 17 and ventricle 30 are preferably comprised of a pair of
substantially flat sheets of a material which is elastic and
compatible with the blood so as not to have any effect upon the
characteristics or composition of the blood as a result of the
physical contact therebetween. The highly resilient elastic sheets
are preferably cemented to one another along their marginal
surfaces so as to air-tightly join the sheets to one another and
thereby define the atrium and ventrical enclosures 17 and 30,
respectively, as well as the associated connections
therebetween.
Ventricle 30 is positioned within a rigid chamber 13 having an
opening 31 for connection to pneumatic actuator 27. The application
of a slight vacuum into the interior of chamber 13 to pneumatic
actuator 27 serves to separate the two cooperating portions of
sheets 24 and 25 which form ventricle 30, to provide a suction
within the interior of the ventricle. As a result, blood is drawn
from atrium 17 through one-way valve 21 into ventricle 30. One-way
valve 26 is closed as a result of the suction developed within
ventricle 30 and the high pressure level in conduit 28 on the
output side of the system. The pneumatic actuator is then operated
to periodically pressurize the interior of chamber 13 causing the
flexible membrane portion of sheets 24 and 25 to transmit this
pressure condition to the blood contained within ventricle 30. Due
to the action of one-way valves 21 and 26, the blood is constrained
to flow through outlet port 30b and one-way valve 26 as soon as the
pressure within ventricle 30 is greater than the pressure within
the outlet end of conduit 28. Valve 21 is closed during this phase
since the pressure at its left-hand side is less than the pressure
at its right-hand side. In this manner, ventricle 30 is operated to
repetitively fill and empty to simulate a pumping pulsatile
operation.
Atrium 17 performs the dual functions of acting as a buffer between
the pulsatile operation of ventricle 30 and the continuous venous
return flow condition at inlet conduit 14 as well as controlling
the vacuum of pressure within conduit 14 to adjustably selected
values. Since the portions of elastic sheets 24 and 25 perform a
limp bladder, the atrium operates as a reservoir which stores the
blood draining into it through the venous return line 14. Upon
demand of ventricle 30, blood is drained from atrium 17 through the
connecting conduit 22 and one-way valve 21 into ventricle 30. The
suction or negative pressure condition within ventricle 30 during
its filling stage is transferred to atrium 17 when the atrium is
drained of blood and is no longer capable of supplying adequate
blood as a result of insufficient blow flow entering atrium 17.
This suction within atrium 17 causes the opposing sheet portions
forming atrium 17 to collapse upon one another and thereby
effectively isolate the filling phase suction imparted upon atrium
17 by ventricle 30 from reaching input line 14. As more blood
becomes available and enters input line 14, its slightly positive
pressure causes a separation of the membrane portions forming
atrium 17 to reinitiate blood flow from atrium 17 into ventricle
30.
Isolation of the pulsatile suction or negative pressure developed
by ventricle 30 due to collapse of atrium 17 in the presence of
insufficient blood flow occurs as a result of the pressure
differential across the interior and exterior surfaces of the
portions of sheets 24 and 25 forming atrium 17. By placing atrium
17 within closed chamber 12, the pressure or suction within the
interior of chamber 12 may be controlled through the connection of
the pressure of vacuum generating source 19 to opening 18. Thus,
expansion or contraction of the atrium 17 may occur at pressures
other than atmospheric, if desired. Since atrium 17 is a flexible
and elastic structure, any pressures or suction across its walls
will be directly transferred to the enclosed fluid and to input
line 14 at any time during which the atrium is not at its
completely full or completely empty state. Therefore, the pressure
or suction within closed chamber 12 is normally selected to be that
level which appears to be at the input venous return line 14 during
normal operation and this input pressure or suction can be
effectively controlled to accommodate the particular by-pass or
partial support function for which it is provided.
FIG. 3 shows a detailed sectional view of a suitable valve design
which may be employed in the system of FIG. 2. As shown in FIG. 3,
fluid flow through conduit 22 is from left to right relative to
FIG. 3, with the left-hand end of conduit 22 being connected to
atrium 17 and the right-hand or downstream end thereof being
connected to ventricle 30. Fluid flow through the valve structure
occurs whenever the pressure on its left-hand side is greater than
the pressure on its right-hand side and further wherein the
pressure differential is of a sufficient magnitude to overcome the
restriction imposed by the two valve flap portions 34 and 36. The
flaps 34 and 36 are each formed of an elastic material capable of
resuming its normal configuration (shown in solid line fashion in
FIG. 3) until the appropriate pressure differential exists across
the valve structure whereby the valve flaps 34 and 36 are forced
apart to permit flow from left to right. When the pressure
differential is reversed, flaps 34 and 36 are forced into
engagement with one another so as to isolate the left and
right-hand portions of conduit 22.
One important characteristic of the valve design shown in FIG. 3 is
that the valve design does not obstruct the central flow pattern of
blood flowing therethrough so as to minimize turbulance and
pressure loss across the valve. Furthermore, the surfaces that come
into engagement upon valve closure is limited to the marginal tip
portions of flaps 34 and 36. Due to their flexible nature, the
flaps tend to distribute the reverse fluid pressure evenly along
the contact surface so as to significantly reduce the surface
contact therebetween and thereby minimize resultant damage to blood
cells passing therethrough. This structure compares favorably with
valve designs in which one or both surfaces thereof are comprised
of valve seats formed of a rigid inelastic material.
FIG. 4 shows an exploded perspective view which illustrates the
physical form of the pump assembly. A pair of complementary
transparent (preferably plastic) covers 40 and 44 for each design
to receive the liner assembly 42 comprised of a pair of liner
sheets previously joined together by any suitable manner to form
the resultant assembly 42. The liner assembly is preferably formed
from two elastic membranes which are configured so as to define
atrium 17, conduit 22 (which contains valve 21), ventricle 30 and
conduit or chamber 32 (containing valve assembly 26). The covers 40
and 44 are each provided with complementary shaped cavities for
receiving each of the components of the pump assembly, which
recesses and/or cavities have been designated by like primed
numerals. The cover halves 40 and 44, when joined together further
define the closed chambers 12 and 13 shown in schematic fashion in
FIG. 2. Although FIG. 4 shows the connecting conduits 18 and 31 as
being provided in cover member 44, it should be understood that any
other arrangement may be utilized. Cover member 44 is provided with
a plurality of spaced threaded fasteners 47 adapted to align with
associated openings 48 provided in cover member 40. At least the
extreme end portions of threaded members 47 are arranged to extend
beyond the upper edge of cover member 40 so as to threadedly engage
suitable tapped members such as, for example, thumb screws (not
shown for purposes of simplicity). In a like manner, the membrane
assembly 42 is provided with a similar arrangement of openings 49
for receiving the threaded fastening members 47. The pump, when
fully assembled is further provided with a support stand 46
suitably joined to cover member 44 so as to hold the assembly at a
predetermined inclined angle. This arrangement causes gravity to
aid in the collection of blood in both the atrium and ventricle
compartments 17 and 30 to thereby expedite blood flow. Liner
structure 42 may be utilized as a disposable item and thereby is
readily replaceable.
As an obvious alternative, in the arrangement shown in FIG. 4, the
assembly 42 may be a single sheet which cooperates with cover
member 40 to form the atrium 17, ventricle 30 and associated
connecting conduits whereby the recesses provided in cover member
44 may be utilized to serve as the enclosed chambers 12 and 13. In
such a case, suitable sealing means may be provided in the
immediate region of the inlet and outlet openings of each of the
flexible chambers to isolate the differing pressure conditions
between the chambers.
The sheets forming atrium 17 may come into contact during those
times in which the chamber is empty and the pressure surrounding
the chamber is greater than the internal pressure. Since the
pressure within closed chamber 12 is static, abrasive damage to the
blood is minimum even under those condition. However, the pulsatile
actuating forces imparted to ventricle 30 may result in occlusive
pumping, which is undesirable. This shortcoming may be remedied by
providing photocell means and cooperating detector means each
arranged above and below the cooperating sheets to detect the
absence of fluid within the chambers and thereby automatically
terminate operation of the pneumatic actuator 27 to prevent the
exertion of occlusive pressure upon the blood when the chamber is
nearly empty. In the case where only a single flexible sheet is
utilized to form the above mentioned chambers, only a single light
source and photocell detector combination need be provided to
control the deenergization of the actuator 27.
FIG. 5 shows another alternative embodiment of the present
invention which provides superior non-occlusive operation as
compared with the embodiments of FIG. 4 and which is comprised of
atrium chamber 62, a ventricle chamber 63, an inflow or venous
return 50 and an outflow connection 65.
Valve assembly 55 serves to connect atrium chamber 62, ventricle
chamber 63, while valve assembly 66 controls the outflow from
ventricle 63. The ventricle chamber 63 is defined by flexible
membrane 57 and the interior contour of housing 54. Membrane 57
also serves as the barrier member for separating the ventricle
chamber 63 from the chamber 61 which is defined by membrane 57 and
the interior contour of housing member 52. Connection 31 serves as
a means for coupling the pulsatile pneumatic actuator to hollow
chamber 61 and thereby exert pulsatile pressure upon the ventricle
chamber 63.
In like fashion, membrane 59 serves as the means for isolating
atrium chamber 62 from hollow chamber 60 which is defined by the
interior contour of housing member 56 and membrane 59. Connection
18 serves as the means for connecting an adjustable pressure of
vacuum source to chamber 60. Housing members 52, 54 and 56 may be
machined molded or otherwise formed preferably from a transparent
material. Membranes 57 and 59 are preferably formed of a flexible
non-stretching material such as polyurethane or dacron reinforced
silicon rubber. Liners of this design, while thin and quite
flexible, do not stretch. Housing portion 54 is constructed so that
atrium chamber 62 and ventricle chamber 63 each have a slightly
larger radius than the curved liners when they are in their fully
expanded state so as to provide non-occlusive pumping action.
Liners 57 and 59 also provide the seals between chambers 60-62 and
61-63 eliminating the need for additional gaskets which would
otherwise be required for sealing against the possibility of air or
fluid leaks. The three housing sections and membranes are
preferably held together by threaded members and cooperating thumb
screws (not shown) which may be substantially similar in nature to
those shown in FIG. 4. The design of the housing sections make the
liners and valves readily accessible for cleaning, removal and/or
displacement. Liners and valve assemblies are preferably of the
disposable type.
Atrium chamber 62 provides continuous venous return flow despite
the pulsatile operation of ventricle chamber 63, as well as
regulating venous return vacuum or pressures at desired levels. The
latter function is obtained by sealing input line 50 from ventricle
63 as atrium 62 is emptied. This is carried out by liner 59 which
when moved to its uppermost position cooperates with the circular
shaped protruding rim 64 to provide a temporary and yet effective
seal therebetween so as to isolate the low pressure state of
ventricle chamber 63 from the higher pressure state of the venous
return flow line 50. When sufficient blood flow is again made
available in excess of the pressures in chamber 60, the antrium
chamber is again free to be filled and the temporary seal formed
between liner 59 and rim 64 is removed.
The valve design of the pump assembly of FIG. 5 is rather unique
and is shown in detail in FIGS. 6a and 6b. The valve is formed of a
flexible resilient material such as, for example, silicone rubber.
The valve is provided with an annular seating rim 85 which is
partially fitted within a retaining flange 90, cut or otherwise
formed in the appropriate housing portion 54 of the pump body. The
lower seating surface 89 provided in housing portion 54 is
diagonally aligned relative to the direction of flow so that the
force exerted by reverse flow urges the valve more firmly into the
mounting recess in such a manner that the diagonally aligned
surface portion 89 causes the downward force exerted upon the valve
assembly to urge the seating flange of the valve assembly outwardly
and upwardly against the undercut portion 90 of the recess. In
other words, the angle of the seating surface 89 prevents the valve
body from being displaced or otherwise moved from its normal
position when high reverse pressures are exerted upon the valve.
During normal fluid flow, the three flaps of the valve whose mating
edges are defined by slits 87a, 87b and 87c are easily urged apart
to permit fluid flow in the normal normal (upward, in the case of
FIG. 5) direction. The slightly outward force component present
during the opening of the valve flaps serves to urge the annular
flange 85 outward and retain the valve firmly seated within its
associated recess so as to prevent high flow rates from urging the
valve assembly from its seated position.
The flaps are each provided with substantially V-shaped lips 84
which mate with adjoining lips to provide good sealing in the case
of reverse fluid flow (i.e., in the downward direction relative to
FIG. 5). The advantages of the valve assembly shown and described
hereinabove are such that no obstruction in the central flow
pattern occurs, the valve surfaces are formed of a plastic material
to minimize blood damages and to be highly compatible with the
blood, as well as providing for simple and rapid removal and/or
insertion of the valves without the need for any special tools. In
the case of ventricle outflow valve 66, the seating flange provides
the additional function of sealing against the possibility of
leakage between housing portion 54 and outflow conduit 65. Fitting
65 may be attached to the pump body portion 54 by any suitable
fastening means (not shown) for purposes of simplicity.
It is important to provide liners in the embodiments of FIGS. 2, 4
and 5 that, while flexible, do not stretch and thereby make the
pump occlusive and which furthermore provide adequate protection
against breakage. In order to incorporate these characteristics
into the pump, I have devised a dual liner. For example,
considering each liner half 24 and 25 of the embodiment of FIG. 2,
or either of the liners 57 and 59 in FIG. 5, these liners are
preferably designed in accordance with the principles shown in FIG.
7 wherein a pair of plastic liners 71 and 72, preferably formed of
polyurethane, are bonded together along their marginal edges by
means of silicone rubber as shown at 73 and 74. In the case of the
embodiment shown in FIG. 5, for example, the silicone rubber is
further employed to bond the liners 59 and 57 to the housing
portions and these sections of silicone rubber are shown as 75,75
and 76,76, respectively. Bonding in this manner facilitates
handling and assembly of the liners and further provides a good
seal between the air and blood cavities provided within the pump
assembly of FIG. 5.
A small amount of water in the form of droplets 77 is provided and
these water droplets are sealed between the liners 71 and 72 to aid
in lubrication of the liners as well as preventing undue wearing of
the liners due to abrasive contact therebetween which would
otherwise occur in the absence of the water droplets. The droplets
77 further enhance the flexibility of the liners 71 and 72 since a
portion of the water droplets are absorbed by the material. Two
thin liners respond more rapidly than one heavy liner in that the
stresses in the liner material are reduced, resulting in a greatly
improved flex life.
Another modification in the embodiment of FIG. 5 concerns the
operation of the atrium 62. Continuous venous return flow is an
important factor. Continuity of flow can occur only if the atrium
chamber is partially filled, so that the venous return blood can
flow into the atrium at all times instead of only part of the time
and in a pulsatile fashion. To obtain the desired operation, an
adjustable clamp 57 is placed in line 50. By adjusting threaded
member 57a, return flow may be accordingly regulated.
As an alternative method, the air pressure in the atrium may be
increased to reduce the venous flow. In order to simplify the
adjustment of the adjustable clamp, a small plunger is positioned
in the air chamber 60 which cooperates with the atrium 62, whereby
the plunger moves either up or down as shown by arrow 95 to
indicate when the atrium is full and more atrium pressure is
therefore necessary or to indicate when the clamp must be further
closed. To facilitate observation of the plunger, the apparatus
shown in FIG. 8 may be set upside down relative to the orientation
of FIG. 5 so that the atrium chamber is positioned above the
ventricle chamber. The operation of the pump, however, remains the
same. As shown in FIG. 8, the housing portion 56 is provided with a
narrow opening 56a for reciprocally mounting plunger 96 which is
provided with a widened portion 96a resting upon liner 59. Scale
graduations 56b may be provided along the length of the plunger 96
to indicate the blood level within the atrium. The reservoir of
blood within atrium 62 enables a constant atrium pressure to be
maintained despite volume changes within the atrium.
A still further modification of the embodiment of FIG. 8 is shown
in FIG. 9, wherein the plunger 96', shown therein, is provided with
a relief valve opening 96b which communicates with an opening 96c
at the opposite end thereof. Whenever the atrium is filled with
blood, plunger 96' is pushed upwardly whereby opening 96c is sealed
by a surrounding sleeve 98 positioned within opening 56a. This
causes pressure to build up in the chamber due to the provision of
a small capacity air pressure pump 99 coupled to conduit 18. As the
atrium chamber empties, plunger 96' moves vertically downward so as
to unseal opening 96d, providing a relief passage through to
opening 96c, enabling the pressure to be vented from chamber 60
into the atmosphere whereby operation of plunger 96' automatically
regulates the venous return blood flow.
It can be seen from the foregoing description that the present
invention provides a novel by-pass pumping system for use as an
assistive blood pump or as a temporary substitute for the natural
heart and whose design is such as to closely emulate the normal
heart functions and characteristics to provide highly reliable and
effective operation in such applications.
Although there has been described a preferred embodiment of this
novel invention, many variations and modifications will now be
apparent to those skilled in the art. Therefore, this invention is
to be limited, not by the specific disclosure herein, but only by
the appending claims.
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