Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
This invention relates to a blood pump applicable
to an artificial heart and a method of manufacturing the
same.
Recently, the development of an artificial heart ,
has been made aiming at the cardiac assistance which is
expected to function temporarily in place of the natural
heart of a patient at the open-heart surgery. Requirements
for the artificial heart call for as follows:
(1) the shape of the artificial heart should be essentially
compatible with the body;
(2) the blood stream should have the least stagnant flow
and the sufficient attention should be paid to the
thromboregistancy.
(3) the flow-resistance should be small to maintain the
sufficient blood flow by the normal venous pressure;
(4) the volume of the ventricle of the artificial heart
should be pertinent to the patient's body;
(5) the artificial heart should be easily attachable to
and detachable from the patient's body;
(6) the fatigue of the constituent materials of the
artificial heart should be small and the sufficient
durability should be guaranteed;
~7~ the design of the artificial heart should be made
considering the least hemolysis; and
(8~ the excessive negative pressure should be avoided at
the ventricular distole period.
~ mong these requirements, (2) and ~6) are the most
important. ~he antithrombus property is influenced by
hydrogynamic factors such as the design of the blood p~mp
and roughness of the blood-contact-surface, the physical,
chemical and electrical properties of the constituent
materials of the artificial heart, the environmental manu-
facturing conditions, and so on. Especially, the design
of the pump is important. Even a little modification of
the shape critically influences on the blood-flow pattern
in the pump. It may cause troubles in the actual long
operation. The thrombosis is considered to be formed
mainly due to the blood-stream conditions in the pump,
particularly to the stagnation in the blood-stream. The
thrombosis is complicatedly influenced by the velocity of
the blood-stream, the mean residence time of the blood in
the pump, the shear rate of the blood at the contact-surface
of the pump, etc.
For the practical use of the artificial heart,
it is indispensable that the blood flux out of the pump
and the pressure wave form thereof should be enough to
maintain the circulation of the blood so that whole body
of the patient. In other words, to function as the
artificial heart, the blood pressure curves caused by the
blood pump must resemble to those of the natural heart as
closely as possible. Ideally, the former should be the
same as the latter. When the difference of the blood
pressure curve between the pump and the natur~l heart
becomes larger than the critical level, patient's body is
no longer adapted to the circumstances. In this case the
SO ,~
patient's condition becomes bad. The most important thing
to keep in mind is that the patientls conditions, who is
supposed to use the artificial heart, are usually very ~ad.
Therefore, the patient reacts so sensitively to a ~mall
difference from the natural heart, which may often become
fatal.
.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present inven-
tion to provide a blood pump in which the stroke pattern of
the blood beaten out of the pump is scarcely fluctuated but
uniform through the term for using the blood pump as an
artificial heart, for example, or 3-6 months.
It is another object of the present invention to
provide a blood pump which has the good antithrombus property
and performance.
It is a further object of the present invention
to provide a blood pump in which the design of the pump is
essentially compatible with the living body, and that the
pump is easily attachable to and detachable from the patient.
It is a still further object of the present inven-
tion to provide methods of manufacturing blood pumps having
the good antithrombus property and pexformance.
In accordance with an aspect of the present inven-
tion, a blood pump comprises a housing provided with a port
for introducing and discharging fluid, a cover portion for
closing the housing tightly, a sac portion defining a blood
chamber with the relatively flat or oval shape arranged in
the housing, an inlet and outlet conduit portions for the
blood, which are integrally formed on the cover portion
communicating with theblood chamber and~ach provided with a
check valve. The blood chamber is characterizedin that when
the blood chamber is compressed, the initial contact point
from the opposite inner surfaces of the sac is regulated
to locate in the area defined by a circle, the center of
which is on the central axis of the wider side of the sac
and in the height range between 0.2L and 0.45L from the
bottom of the sac and the radius of which is 0.15D, where
L is the whole height of the sac, D is the maximum width of
the sac and the wider side is defined by the side projected
to the vertical plane including the maximum width D of the
sac.
In accordance with another aspect of the present
invention, a blood pump comprises a housing provided with
a port for introducing and discharging fluid, a cover portion
for closing the housing tightly, a sac portion defining a
blood chamber with the relatively flat or oval shape arranged
in the housing, an inlet and outlet conduit portions for
the blood, which are integrally formed on the cover portion
communicating with the blood chamber and each provided with
check valve- The blood chamber and inlet and outlet conduits
are characterizedin that the wholeblood-contact inner surface
thereof is seamless.
In accordance with a further aspect of the present
invention, a method of manufacturing a blood pump comprises
steps of:
(a) preparation of a cover including a pair of conduit
portions, which is made from the plastisol of polyvinyl
chloride;
(b) attaching the cover to a mold for a sac portion in the
fluid-tight manner;
(c) pouring the plastisol of polyvinyl chloride into the
mold through one of the conduit portions of the cover
so that the poured plastisol is enough to contact with
the cover;
(d) heating the mold so that the part of the plastisol
contacting with the mold is gelled;
(e) removing the ungelled plastisol from the mold;
(f) heating the mold so as to completely cure the gelled
plastisol and connect it to the cover seamlessly; and
(g) removing the mold from the obtained sac portion.
In accordance with a still furthex aspect of the
present invention, in a method of manufacturing a ~lood pump,
a dipping process is repeated by the predetermined times,
said dipping process comprising steps of dipping a mold for
a sac portion and a pair of conduit portions into the solu-
tion of polyurethane and then air-dried so that a polyurethane
film is formed on the outer surface of the mold.
Various other objects, advantages and features of
the present invention will become readily apparent from the
ensuing detailed description, and the novel features will
be particularly pointed out in the appended claims.
.
50 - --
BRIEF DESCRIPTION OF THE DRAWINGS
_ _
Fig. 1 is an exploded view of an artificial heart
according to the first embodiment of the inventioni
Fig. 2 is a cross-sectional view taken along the
line II-II of Fig. 1;
Fig. 3 is a cross-sectional view similar to Pig. 2
showing a contrac~ion state of the blood chamber;
Figs.4A to 4C are vertical sections of the arti-
ficial heart showing the manner of the contraction of the
blood chamber;
Fig. 5 is another vertical section taken along
the line V-V of Fig. 2;
Fig. 6 is a perspective view of an envelope accord-
ing to the second embodiment of the invention;
Fig. 7 is a cross-sectional view taken along the
line VII-VII of Fig. 6;
Fig. 8 is a vertical section of an artificial heart
according to the third embodiment of the invention;
Fig. 9 is a vertical section similar to Fig. 8
showing a contraction state of the blood chamber;
Fig. 10 is a partially sectional view of a sac
according to the fourth embodiment of the invention;
Fig. 11 is a partially sectional view of a sac
according to the fifth embodiment of the invention;
Fig. 12 is a cross-sectional view of a sac accord-
ing to the sixth embodiment of the invention;
Figs. 13A to 13Fare vertical sections showing steps
of a manufacturing process of a blood chamber;
-- 6 --
Fi~s.14A and 14B arevertical sections showing
steps of another manufacturing process of a blood chamber;
Fig. 15A is an exploded view of a blood vessel
and a brim member;
Fig. 15B is perspective view of the assembled
blood vessel;
Fig. 16 is a wave form chart of the driving
pressure in an artificial heart according to an embodiment
of the invention;
Fig. 17 is a wave form chart of the stroke of the
blood in the axtificial heart of Fig. 16;
Fig. 18 is a wave form chart of the stroke of
the blood in an artificial heart according to a comparison
example; and
Fig. 19 is a wave form chart of the stroke of
the blood in an artificial heart according to another compari-
son example.
DESCRIPTION OF THE PREFERRED_EMBODIMENTS
Referring to the first embodiment of the inven-
tion shown in Figs. 1 to 5, an artificial heart includes
an outer housing 1 made of a synthetic resin. The cross
section of the housing 1 is flat or oval. At the opening 3
of the housing 1, a flange may be formed, if desired. A
cover 4 made of a synthetic resin is attached fluid-tightly
to the openning. The cover 4 is provided with an inlet
conduit 5 and an outlet conduit 6 for the blood, which are
integrally formed with the cover 4 and arranged nearly
5~
paralell with each other. In the conduits 5 and 6, check
valves 7 and 8 are provided. On the inner surface of the
cover 4, an annular projec~iongis integrally formed, to which
a sac 10, which defines a blood chamber 11 of the pump is
attached. In this embodiment,the annular ~rojection 9 is
~luid-tightly connected with the outer opening 12 of the
sac 10. The fluid-tight connection is
usually made by with the adhesion, ultrasonic welding or
the like. Thus, the blood chamber 11 is integrated with
conduits 5 and 6. The sac 10 may be made of an elastomer
such as polyvinyl chloride resin with plasticizer or poly-
urethane and has the flat or oval cross-section as shown in
Fig. 2. The cover 4 is also bonded to the housing 1 with
the adhesion, ultrasonic welding or the like. Alternatively,
the cover 4 can be fixed to the housing 1 with screws. The
cover 4 and sac 10 can be united seamlessly with each other.
Then the cover 4 is attached to the housing 1. The housing
1 has a port 14 at lower portion through which air is
introduced and discharged. In this case, the pump is driven
by air pressure but it may be done with any kind of fluid,
for example, water, oil or carbon dioxide gas.
Next, the operation of the artificial heart accord-
ing to this embodiment will be described.
First, compressed air is introduced into the hous-
ing 1 through the port 14 so that the blood chamber 11 is
contracted by the pressure as shown in Figs. 4A to 4C.
There~y, the blood in the chamber 11 is squeezed out through
the check valve 8 of the outlet conduit 6 while the check
valve 7 of the inlet conduit 5 is closed. Next, the pressure
in the housing 1 is reduced. The sac 10 is expanded to its
original state or more. As the volume of the blood chamber
11 is increased, blood is introduced into the chamber 11
through the opened check valve 7 of the inlet conduit 5
while the check valve 8 of the outlet conduit 6 is closed.
The abo~e operations are repeated alternatel~, thereby the
blood is intermittently beaten out.
In order that the blood pump satisfactoril~ func-
tions as the artificial heart for asisting the natural
heart, the operation pattern according to the expansion
and contraction of the blood chamber 11 at the beat rate of
60-120 min. must be always uniform without any happening
of an unusual pattern through the long operation: at least
one month. That is, during the countless heartbeats, the
mode of action of the sac 10 discharging the blood must be
kept in the same pattern. For this purpose, the most
important point is that the initial picture of the deforma-
tion of the sac 10 must be kept uniform. According to
inventor's finding~the location of the initial contact point
between the opposite inner surfaces of the sac 10 is very
important. The picture of deformation of the sac 10 by the
change of the air pressure is shown in Fi~s. 4B and 4C.
In this embodiment, the cross-section of the sac lO
must be flat or oval shape as shown in Fig. 2. In this connec-
tion, the more detailed analysis will be given with refer-
ence to Fig. 5. The figure shows a vertical section of the
sac 10 which is taken along the longest axis of the cross-
section thereof. Hereinafter, the side of the sac 10
projected to the plane of Fig. 5 is called "the wider side".
1~9~U50
As already mentioned, initial contact point from
both wider side of the sac 10 must be located in an area
indicated by shadow in Fig. 5. This area is defined as
follows. Here, the whole height of the sac 10 is L and the
width of the wider side, that is, the maximum width of the
sac 10 is D. The area is defined by a circle. The
center O of the circle is located on the vertical cen~ral
axis P of the wider side. Here,"vertical" means-the direc-
tion along the conduits 5 and 6. The center point O must
be within the height range between 0.2L and 0.45L, prefer-
ably 0.2L and 0.4L from the bottom of the sac 10. The
radius of the circle is 0.15D, preferably o.lD, more prefer-
ably o~o8D~ The inventor formed that when the initial
contact point of the inner surfaces of the sac 10 is strictly
regulated to locate in the above-mentioned area, the ~ode
of the deformation-picture of the sac 10 can be kept uniform
in the long term. In this case, it is notable that the blood
streams in the chamber are quite uniform and regular, the
circular streams are shown by the arrows in Figure S. This
ideal circular blood stream is produced when the bottom of
the blood chamber is designed so that vertical section there-
of is characterized with semi-circular shape as shown in
Fig. 5. On the contrary,when the initial contact point dis-
locates out of the circle, the fluctuation arises in the
pattern of the action of the sac 10. The unusual mode of
action of the sac causes the unusual discharging pattern of
the blood output from thP pump, which influences on the
patient condition. As a result, fatal bad influenceoften
occurs on the patient to whom the artificial heart is applied.
1~9~51~
, -
According to the present inventor's study, a flat
shape as shown in Fig. 2 is very effective to keep the
initial contact point in the above-mentioned specified area.
The flatness (F) at the cross-section, which is defined
by the rate of the maximum width D of the sac 10 to the
maximum width d perpendi~ular to the former, at the unloaded
condition, should be within the range of 2.0 to 4.0, prefer-
ably 2.1 to 3.5, more preferably 2.2 to 3Ø When the flat-
ness F is within the above range, uniform action of the
deformation of the sac 10 can be obtained.
When the flatness ~ is below 2.0, various distort-
ed deformation of the sac 10 often arises and rom the
practical point of view, such artificial heart can not be
clinically applied. For example, when the blood chamber is
cylindrical (the flatness F is 1), it was experimentally
clear that the mode of the compre~sion o the sac is not
uniform. When the cylindrical sac is compressed by the air
pressure, the portion of th~ sac starting the deformation
is not defined in every beat and the manner of the volume-
change of the blood chamber is variously fluctuated. Fur-
ther, the minimum volume of the blood chamber is varied in
every beat. Therefore, such artificial heart is impossible
to keep uniform blood-output from the pump and the blood
pressure curve thereof. On the other hand, when the flatness
F is above 4.0, the expansion behavior of the sac 10 by the
reduced pressure becomes unstable.
In this embodiment, the initial contact point is
regulated to locate in the predetermined area by the abo~e-
mentioned manner. Thus, the opposite inner surfaces of the
- 11 -
sac 10 contac~ with each other firstly at the regulated
initial contact point from which the contact surface area
between the inner surfaces spreads out. ~y this manner, the
uniform circular blood stream along the side wall of the
pump is always reproduced in the blood chamber 11 so that
the blood may beat out through the valve 8 in the same
behavior at each heart beat. Uniform circular blood ~tream
in each beat thus produced can prevent the b~ood from the
thrombus formation in the chamber 11.
In this embodiment, the blood contact surfaces,
for example, the inner surface of the sac 10, and conduits
5 and 6 may be made of elastomers like polyvinyl chloride
containing plasticizer or polyurethane. Instances of the
plasticizer may be dioctyl phthalate (DOP), dibutyl phthalate
~DBP), butyl benzyl phthalate (BBP), dioctyl adipate (DOP),
butyl phthalyl butylglycolate (BPBG), methyl acetyl ricino-
late (MAR), acetyl tributyl citrate (ATBC) and the other
known plasticizers for polyvinyl chloride. Amount of plasti-
cizer, the ranges from 40 to 100% by weight, more preferably
50-80% by weight based on the polyvinyl chloride. In addi-
tion, the suitable stabilizer, for example, nontoxic calcium-
zinc organic compound may be added to the polyvinyl chloride.
The degree of polymerization of polyvinyl chloride is prefer-
ably 500 to 2000.
Polyurethane to be used in this embodiment is
devided into two categories, one being polyether-polyurethan
(polyurethane of polyether origin), another being polyester-
polyurethane (polyurethane of polyester origin), both of
which can be used. However the polyether-polyurethane is
- 12 -
preferably used because of the better elastic property and
better fatigue resistancy~
Polyurethane can be obtained by the reaction
between diisocyanate and polyol. Diisocyanate used in
this embodiment are tolylene diisocyanate (TDI), 4,4' -
diphenylmethane diisocyanate (MDI), 1,6 - hexamethylene
diisocyanate (HDI~, 1,5 - naphthalene diisocyanate (NDI),
3,3' - dimethoxy - 4,4' - biphenyl diisocyanate (TODI),
phenylene diisocyanate (PDI), 4,4' - biphenyl diisocyanate,
etc.
The polyol used in polyester-polyurethane are
adipate groups with hydroxyl groups at the both ends, for
example, poly-(ethylene adipate), poly-(propylene adipate),
poly-(1,4 - butylene adipate), poly-(1,5 - pentylene adipate),
poly-(1,3 - butylene adipate), poly-(ethylene succinate)I
poly-(~,3 - butylene succinate), etc. The polyester-polyure-
thane forms harder elastomer having the high modulus and good
tear strength. Therefore, it is suitable for the cover 4 and
conduits 5 and 6.
The sac 10 requires high elasticity, good elastic
reco~ery and fatigue resistancy. Therefore, polyether-poly-
urethane is preferable for the sac.
Examples of polyether used for the polyurethane
are tetramethylene glycol, polyethylene glycol, polypropylene
glycol, pentamethylene glycol, diglyme, etc.
Polyether-polyurethane can be made as follows.
The a~o~e-mentioned glycol group is reacted with diisocyanate
to obtain the prepolymer having hydroxyl groups at the both
- 13 -
ends, then the prepolymer is reacted with compounds ha~ing
diisocyanate groups at the both ends. Alternatively, the
above-mentioned glycol group is reacted with diisocyanate
to obtain the prepolymer having diisocyanate groups at the
both ends, then the prepolymer is subjected to react with
diamine or diol as chain extender. Further, so~called
segmented-polyurethane which is composed of soft segments
and hard segments may be used. Soft segments (which is defined
by the lower secondary transition temperature) are usually
polyether chain with hydroxyl groups at the both ends, and
hard segments are the part of molecule with benzene ring and/or
symmetrical structure in the chain.
Polyurethane may be underwent cross-linking in
order to increase the mechanical strength thereof. Instances
of the cross-linking agent are N,N,N',N'-tetrakis (2 -
hydroxy propylethylene di~nine), 4,4' - methylene - bis
(2 - chloroaniline), 4,4' - diaminodiphenylmethane, 3,3' -
dichloro - 4,4' - diaminodiphenylmethane benzidine, 3,3' -
dimethyl benzidine, 3,3' - dimethoxy benzidine, 3,3' -
dichlorobenzidine, p-phenylene diamine, etc. The cross-
linking can be effected by the heat treatment after addition
of the above-mentioned cross-linking agents. The amount of
the cross-linking agents is preferably 0.01-5 wt. %, more
preferably 0.1 - 3 wt. ~ based on the polyurethane. Besides,
the temperature of the heat treatment is preferably 60 to
150C, more preferably 80 to 120 C, still more preferably
80 to 110C
When the sac 10 is made of soft polyvinyl chloride
which means polyurethane with plasticizer, the thickness of
- 14 -
o
the sac is preferably 0.5 to 2.0 mm, more preferably 0.6 to
1.5 mm, still more preferably 0.8 to 1~2 mm in consideration
of the restitution and fatigue-resistance, properties.
When the sac 10 is made of polyurethane, the thickness
thereof is preferably 0.3 to 1~5 mm, more preferably 0.4 to
1.2 mm, still more preferably 0.8 to 1.0 mm. When the
thickness is greater than the above-mentioned range, it is
difficult to obtain the preferred movement of the sac 10 for
beating out the blood, because thicker wall causes the
delayed timing of the movement of the sac, thus, fails to
react smoothly with the changes of the pressure in the hous-
ing 1. Besides, the required time for the deformation of
the sac 10 elongates. On the other hand, when the thickness
of the sac 10 is smaller than the above-mentioned range,
the control of the action of the sac 10 becomes difficult,
because the sac 10 becomes too sensitive to the change of
the pressure.
For the valves 7 and 8, the commercial valves
may be used. Such valves are the ball type, disk type,
leaflet type, etc. Particularly, the Bjork-Shilley valve
which is a disk valve of the hinge type is preferably used.
In the artificial heart according to this embodi-
ment, the surface which contacts with the blood may be
coated with the material showing the good antithrombus
property to improve the blood compatibility. For example,
the surface treatment are made with an anti-coagulant material
for blood such as dimethyl siloxane, and/or polyurethane,
the block-copolymer of polyurethane and polydimethyl siloxane,
in which polyether-polyurethane is preferable and a blend
- 15 -
- ~iL9~L~SO
of polyurethane and polydimethyl siloxane, if desired, cross-
linked polydimethyl siloxane, or interpenetrating copolymer
of polyurethane and polydimethyl siloxane, and so on. It is
found effective that at least the sac 10 is made of polyvinyl
chloride substrate including the plasticizer and the unti-
coagulant material layer of 1~300 ~ thickness, which contacts
with the blood, is formed on the surface of the substrate.
Figs. 6 to 12 show various modified embodiments
of the ir.vention. In these embodiments, the construction
of each artificial heart but the parts specified hereinafter
is the same as that of the above-mentioned embodiment.
Figs. 6 and 7 show the second embodiment, of the
invention. In this embodiment, each of the opposite wider
sides of the flat shaped sac 20 are gradually curved inside
at the unloaded condition. In this case, the ridge of the
curved portion coincides with the vertically central axis
of the wider side. This construction effects to regulate
the initial contact point above defined on the vertically
central axis of the wider side and within the regulated range
proposed in this invention. In this embodiment, each of the
wider sides may be curved also in the vertical direction in
Fig. 6 so that the peak of the curved portion locates in the
area defined by the invention. Also, only the neighbourhood
of the initial contact point to be regulated may be dented
from both wider sides so that the peak thereof may firstly
contact with each other.
Figs. 8 and 9 show the third embodiment of the
invention. In this embodiment, the bottom of the sac 30 of
the relatively flat shape has the nearly V-shaped vertical
- ~L9il~5~)
r
section taken along the plane perpendicular to the wider
side. This construction, effects to regulate the initial
contact point from both opposite wider sides in the area
defined by the invention. Preferably the opposite wider
sides can closely contact with each other around the bottom
portion. Accordingly, the better compression pattern of
the blood chamber 11 can be obtained, namely the side
portions of each wider wall are smoothly compressed. The
compression begins around the bottom portion of the chamber
11, and then the contact-area is gradually and uniformly
out-spreads to the upper part with concomitant compression
of the sides. The V-shaped vertical section (we call "ridge
bottom" hereafter) is formed at around the bottom of the
chamber. The ridge bottom is preferably formed at the
parts lower than those having O.9D. The dihedral angle ~
defined by the opposite wider sides is 30 to 120, preferably
40 to 100 more preferably 50 to 70, still more preferably
around 60. When the dihedral angle is below 30 , the
bottom portion of the sac 30 becomes too flat. On the other
hand, when the dihedral angle is above 120 , the bottom
portion of the sac 30 is hard to be compressed. In this
embodiment, athinner bottom ridge of the sac 30 effects to,
facilitate the deformation of the sac 30. Thus the thinner
bottom ridge is preferable.
Fig. 10 shows the fourth embodiment of the inven-
tion. In each wider side of a sac 40 of the relatively
flat shape according to this embodiment, a thinner portion
41 is formed, the thickness of which is smaller than the
mean thickness of the sac 40. The thinner portion 41 is
11S~1~5~
centerred by the initial contact point to be regulated in
accordance with the invention and has a predetermined area.
Because the thinner portion 41 is more deformable by the
external pressure than the other portion, the opposite
wider sides of the sac ~O can contact with each other
initially at the thinner portion 41. In this case, the
thinner portion 41 may be made by reducing the wa.l thick-
ness from the outer and/or inner surfaces of the wall of
the sac 40. The thickness of the thinner portion 41 is
3 to 50~ less than the mean thickness of the sac 40 and
preferably 3 to 50% less, more preferably 5 to 30% less.
The area of the thinner portion 41 is preferably deined by
a circle, the center of which is the predetermined initial
contact pOillt and the diameter of which is nearly 2/3D -
1/2D (D is the largest width of the envelope 40). The
thinner predetermined portion is not always shaped circular,
but it may be rectangular, square or the other polygons with
round corners. Besides, the thickness of the thinner por-
tion 41 may be gradually changed so that the thickness at
the predetermined initial contact point may be the smallest.
Fig. 11 shows the fi~th embodiment of the inven-
tion. In this embodiment, the thickness of the bottom
portion and/or the both side portions of the wider sid~s
of the sac 50 is ~hinner than that of the other portions.
Therefore, by the thinner bottom poxtion, the initial contact
point is more effectively regulated to locate in the area
defined by the invention. Besides the deformation at the
both side portions of the wider side becomes easier by the
smaller thickness. This means the uniform compression
0
can spread almost whole part of the sac which eliminates any
stagnant part of the blood in the pump. This greatly effects
to prevent the thrombos formation. The blood coagulation
in the bottom and the both sides of the blood chamber observed
so far isthlscompletely eliminated by this invention. The
compression pattern of the blood chamber 11 are so smooth
in this embodiment. The thickness of such thinner portion
is 5 to 80% less, preferably 10 to 70% less, more preferably
10 to 50% less than the mean thi~kness of the envelope 50.
The thinner bottom portion is formed up to the height of
1/2L (L is the whole height of the sac 5~). The thinner
bottom portion can be limited in the ridge of the bottom.
Concerning the thinner side portions, the thickness can be
reduced eLther continuously or partially. Each thinner
side portion is preferably formed along the vertically
central axis of the narrow side of the sac 50 (which is
the side, perpendicular to the wider side). In this case,
the thinner portion may be formed at least on the central
vertical axis of the narrow side.
Fig. 12 shows the sixth embodiment of the inven-
tion. In this embodiment, both narrow side of a sac 60 has
the nearly V-shaped cross~section. This V-shaped side-wall
may be formed around the bottom portion, and may be up to
the 1/3 or half height of the sac. The V-shaped side wall -
may also be formed on the whole height of the narrow side
wall of the sac. By this construction, the both side por-
tions of each wider side are smoothly compressed, thus blood-
stagnancy at the side of the blood chamber can be effectively
eliminated. By using this construction of the chamber the
- 19 ~
~9~
compressed portion are grad~ally and uniformly spread out
from the~ottom to ~heupperpart ideally. Thus, theuniform
compressi~n pattern of theblood chamber 11can e ~ways obtained.
The dihedral angle 9 defined by the opposite wider sides
is 30 to 120, preferably 45 to 100, more preferably around
60 When the dihedral angle is below 30, the sac 60
becomes too flat. On the other hand, when the dihedral
angle is above 120, the both side portions of the sac 60
becomes difficult to be compressed. In this embodiment,
it is more effective that the both side portions of the
sac 60, namely the neighbourhood of the central axis
of each narrow side is relatively thinned so as to facilitate
the deformation.
In the above-mentioned all embodiments, it is
effective that the whole inner blood-contact surface is
made seamless. The reason is that, if there is uneven por-
tions on the inner surface of the artificial heartl for
example, the seam between the sac 10 and conduits 5 and 6,
the bloodstream is disturbed at the uneven portion. As a
result, the thrombus is quickly formed therefrom. This
kind of trouble can be eliminated by the seamless inner
surface of the artificial heart.
~ ext, manufacturing processes of the artificial
heart having the seamless inner surface will be described.
Referring to Figs. 13A-13F, a cover 74 with a
pair of conduit portions 75 and 76 is manufactured from the
plastisol of polyvinyl chloride by the dipping process as
described hereinafter. At this time, an annular projection
for receiving the check valve may be formed in each of the
- 20 -
0
conduit portions 75 and 76. Alternati~ely, a pair of
conduit elements each including the valve may be connected
to the cover. The cover 74 is provided with an annular
projection 79 and the latter is inserted fluid-tightly
into a metal mold 100 as shown in Fig. 13A. Then, the
plastisol of polyvinyl chloride (for example, Type-131A,
Nippon Zeon Co. Ltd.) is poured into the mold 100 to ~he
predetermined level as shown in Fig. 13B. Then, the mold
100 is dipped into the heating bath. The heating tempera-
ture is in the range of 70 to 150C, preferably 80 to 110C.
When the polymer used in the plastisol is not a homopolymer
of vinyl chloride but the copolymer having the lower soften-
ing temperature such as vinyl chloride-vinyl acetate copoly-
mer and vinyl chloride vinyl ether copolymer, the heating
temperature may be relatively low. The treatment time in
the heating bath is preferably a few minutes to 30 min.
When the heating is insufficient or the treatment time is
too short, the thickness of the gelled layer obtained is
too small. On the contrary, when the temperature is too
high or the treatment time is too long, the thickness of
gelled layer becomes too large.
In this treatment, the part of the plastisol
oontacting with the mold 100 is gelled by the heat and
adheres to the inner surface of the mold 100 to form a
gelled layer 70' of the predetermined thickness as shown
in Fig. 13C. At this time, there is the plastisol inside
of the annular projection 79 which is formed integrally with
cover 74, this plastisol is not gelled because of the heat
insulation effect of the annular projection 79. Therefore,
~; ~
this part of the plastisol flows down by the gravity during
the procedure of discharging the paste as shown in Fig. 13D.
Thereby the surface of the gelled layer 70' is integrated
so that the even and seamless inner surface of the blood
chamber 71 is obtained. Subsequent the heat curing results
in the even and seamless inner surface in the result as
shown in Figs. 13E and 13F. The heating temperature in
this step is preferably 160 to 240 C, more preferably 190
to 210C. When the heating temperature is below 160C, the
curing is insufficient. When the temperature is above 240C,
polymer may decompose or discolour. Then, after being
cooled, the mold 100 is removed as shown in Fig. 13F. By
this procedure, seamless blood-pump can be produced.
The above-mentioned process can be applied to the
aquatic plastisol and, of course, may be applied to the
organosol in which the organic solvent is used as a disper-
sion medium.
Next, referring to Figs. 14A and 14B, another
process will be described. In this process, a cover 84 is
made of epoxy resin and provided with no annular projection.
~he cover 84 is attached fluid-fight to a metal mold 110
for the slush molding in the similar manner to the above-
mentioned process as shown in Fig. 14A. Then, the plastisol
of polyvinyl chloride is poured into the mold 110 to the
level which is a little higher than the lower end surface
of the cover 84 as shown in Fig. 14B. The subsequent
operations may be th~ same as shown in the above-mentioned
process shown in Fig. 13. In this case, the part of the
plastisol inside of the cover 84 is not gelled because of
- ~2
- - -
the heat insulation of the cover ~4 and so flows down along
the surface of the gelled layer 80' in the step of discharg-
ing the plastisol so that the inner surface may be smooth
integrated seamless.
By the above-mentioned two processes, the blood
pump mainly made from soft polyvinyl chloride for the use
of the artificial heart can be formed in one body, which
has the seamless inner surface.
In this embodiment, when the cover is formed
from the plastisol of polyvinyl chloride, relatively low
content of the plastici~er may be preferable. Example of
suitable plastisol component are the one comprising 100
parts of polyvinyl chloride, 40 to 60 parts of dioctyl
phthalate as the plasticizer and 3 parts of a calcium-zinc
organic composite. On the other hand, the blood chamber
must have more flexible nature and better elasticity
because the chamber must deform repeatedly accompanied
the change of the external air pressure in every beat.
The plastisol suitable for the sac preferably comprises
100 parts of polyvinyl chloride and 70 to 90 parts of
dioctyl phthalate.
Next, it will be described that a process to
manufacture the blood pump of polyurethane having the
seamless inner surface.
~ irst, a mold is made from paraffin or wax into
the predetermined shape including the sac and a pair of
conduits. The mold i~ dipped into the solution in which
polyether-~olyurethane is dissolved in dimethylformamide
at the concentration of 6-20%, preferably 8 to 15~, and
- 23 -
o
then air-dried (This operation is called "dipping process"
hereafter). The solution maybe made of the one of the group
consisting of dimethyl acetoamide, dimethyl-formamide,
tetrahydrofuran, and dioxane. This operation is repeated,
for example, about 30 times. In the operation, the poly-
urethane film formed on the mold may be subjected to extrac-
tion with water in a proper time for the complete removal
of the solvent. In this manner, the polyurethane film of
suitable thickness on the mold can be obtained seamlessly.
After the predetermined film thickness of the sac is
obtained, the inlet and outlet conduits portions may be
further subjected to the dipping processes predetermined
times so that the thickness of the conduits can be larger
than that of the sac. For the dipping of the conduit
portions, the solution of polyester-polyurethane, which has
the relatively large stiffness, may be used so as to obtain
the harder conduits. Then,the mold on which the polyurethane
film is formed is heated to the temperature higher than
the melting point of paraffin or wax. The melted liquid
paraffin or wax is removed from the molded polyurethane
member. Polyurethaneblood-chamber with two conduits thus
formed is washed with the suitable solvent. As shown in
Fig. 15, a vessel thus formed comprises a pair of thicker
inlet and outlet conduit 95 and 96 portions and a thinner
sac portion 90 and has seamless inner surface.
Then a brim member 94 is attached to the conduit
portions by insertion through holes of the brim member and
connected each other fluid tightly for example, by adhesion
as shown in Fig. 15. Alternatively, the brim member may be
- 2~ -
~ 9 ~
r
connected to the vessel during the dipping process in such
a way that the brim member is fixed at the predetermined
position. Then, the sac portion of the vessel is placed
into a housing and the brim portion is bonded to the housing.
Thus, a blood pump of polyurethane which has the seamless
inner surface can be obtained.
Besides, in the above-mentioned process, a
separable metal mold having the vertical separation line
may be used in place of the mold of paraffin or wax.
Next, experimental results will be described.
In the experiment, a blood p~mp according to the
second embodiment of the invention as shown in Figs. 6 and
7 was employed. The flatness F was 2.3, and the whole
height L was 63 mm and the maximum width D was 63 mm. In
the cross section of the sac 20 shown in Fig. 7, the maximum
width d perpendicular to the maximum width D was 26 mm and
the minimum distance d' between the opposite dented portions
of the wider sides was 24 mm. The sac 20 of polyurethane
was arranged in a housing made from polycarbonate and Bjork-
Shilley valves were employed as the check valves. The
volume of the blood for filling up the blood chamber 11
was 75 ml. The negative pressure for driving the pump was
40 mmHg, the beat rate was 90/min. the pressure at the inlet
of the pump was 200 mmHg and the pressure at the outlet was
104 mmHg. The stroke of the blood beaten out from the pump
and the waves of the stroke volume were measured with an
electromagnetic flowmeter (made by Nihon Xohden Kogyo Co.
Ltd., 14 mm~) which was attached to the outlet of the pump.
Simultaneously, the driving pressure in the housing and
- 25
35~3
the wave form were measured with a pie~oelectric gauge. The
above-mentioned pressures at the inlet and outlet of the
purnp were measured with water column and mercury manometers.
Examples of the wave forms of the driving pressure and
stroke of the blood are shown in Figs. 16 and 17, respective-
ly. In the experiment of the simulative operation for a
month, these wave forms were completely stable and uniform
through the above-mentioned term.
For comparison, similar experiments were carried
out, in which a blood pump having the s~ne ~olume of the
blood chamber but a cylindrical sac (comparison exarnple A)
and a blood pump having a flat sac of the flatness F=1.88
(comparison example B) were employed. The blood chamber of
example B nas the maximum width D of 62 mm, and the whole
height L of 33 mm and the volume of the blood for filling
up the blood chamber was 80 ml. For the comparison example
A, the wave form of the driving pressure was the same as
that shown in Fig. 16 but the wave form of the stroke of
the blood was multifariously changed. Some typical instances
thereof are shown in Fig. 18. In other words, when the
blood chamber of cylindrical shape was used, the stroke
pattern of the blood beaten out of the purnp was considerably
fluctuated. In the cornparison example B, the stroke pattern
of the blood was not so unstable like the comparison example
A, because the sac has flat shape to some extent. But the
b100d stroke pattern was sometimes fluctuated (as shown in
Fiy. 18). In the mock driving test, the initial contact
point between the opposite wider sides of the sac of the
comparison example B sometimes dislocated out of the area
defined by the invention. From this fact, it became apparent
that there is a mutual relation between the initial contact
point of the sac and the fluctuation of the stroke pattern
of the blood.
Next, the relation of the flatness F and the
location of the initial contact point in view of the frequ-
ency of the fluctuation of the stroke pattern was examined
by a series of the simulative experiments (the beat xate
was 90/min.) for 23 days. The experimental results are
given in the following table.
- 27 -
~9~5CI
.. o o
N O O
, N
N O O
. ~
O 'ua~ ~ 3
N O O ~
11~
G) ~u~ o
O .~1 3 .3 ~4
N ~ _ CJl/~) h ~
~a ^ a) u
* ~ ~ O o
~ ~ U~ O
. ~ ~
t) ~ o ~ ,C
. 3~ ~ . ~0 h.a ~ ~
V ~ 41
. ~ ~ O
. O S U~
. ~ ~ ~ ~ 3 r~ ~
. ~ o a~ o r1 ~C
. ~ ~ rl h
i o~ U~
. a~ G~ 1 a) o
. ~ N U~ E~ O
* ~ h Cl. h ~:
~a u ,,
. Q~ O rl ~J
,_1 ~ ~ 3
. ~1 C: O O
: ~ ~ ~ ~ .~
o s ~: s ~a 3
I_ ~ U ~ ~ U
. N rd ~r~ r-J ~r-l U) U~
s
~a ~ s ~
~a ,~ 3 0
. Ln ~ N (11 U a) U~ U
oJ ~ ~a
E~ Ul h u~ C:
a
S ~ r~ S ~ E~
I . . ~ I~ E~
. ~ I~ ~D
.' +~ a)
~ s
s ,~ ~
U ~ ~ R
~ o ~ ~a
aJ h ~ O C~
s ~ .c : _~
~ U ~ ~
~: ~
. 4~a) ~ ~-,~ aJ--
o~ ~-- o o~a
~n ~ ~ ~ o
. u~ h ~ U
U h
o~ ~ a
~~d ~ u~
,~~ .a ~ o
~ ~ ~ ~ U ~ ,~
I- . . .
.
¦ As apparent from the results, when the flatness
of the sac is more than 2.0, the initial contact point
scarcely dislocates out of the area defined in the i~ven~
tion. The frequency of the fluctuation of the stroke
pattern is very few in comparison with that in which the
flatness F is below 2Ø It is also shown that when the
I . wider sides of the sac is curved inside or the thickness
¦ of the sac wall at the neighbourhood portion of the initial
~ contact point is smaller, the dislocation of the initial
! contact point from the predermind area becomes smaller.
,' : In these cases the frequency of the fluctuation of the
~: stroke pattern is fairly reduced in comparison with that
for the blood chamber having the same flatness but having
no curved or thinner sac wall.
- 29 -
