Blood delivery instrument for regulating the amount of blood stored in an accumulator independent of the pumping operation

A blood reservoir includes a blood tank, a blood accumulator connected in fluid communication with an outlet of the tank for receiving blood from the tank, and a pumping device for driving the accumulator to displace blood out of the accumulator. The accumulator typically in the form of a flexible bag is adapted to store blood in an amount proportional to the volume of blood in the tank when the volume of blood in the tank is reduced below a predetermined value. The pumping device is operated for intermittent blood delivery and can regulate the amount of blood displaced out of the accumulator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The blood reservoir and blood delivery apparatus according to the invention 
are described in detail in conjunction with several preferred embodiments 
shown in the drawings. 
Referring to FIGS. 1 through 9, a blood delivery apparatus 1 according to 
the invention includes a blood reservoir 10 and a blood delivery fluid 
feed unit 5. 
The blood reservoir 10 includes a blood tank 2 having blood inlets 21, 22 
and a blood outlet 26, a blood accumulator 3 in communication with the 
blood outlet 26, and a pumping means 4 for the driving accumulator 3 so as 
to deliver blood in the accumulator 3 to a downstream destination. The 
blood accumulator 3 is adapted to store blood in an amount proportional to 
the volume of blood reserved in the tank 2 at least when the volume of 
blood reserved in the tank 2 is below a predetermined value. The pumping 
means 4 is intermittently operated to drive the accumulator 3 so as to 
intermittently deliver blood therefrom. The pumping means 4 is controlled 
by a fluid feeder 5 for delivery. 
As mentioned above, the blood accumulator 3 stores blood in an amount 
proportional to the volume of blood in the tank 2 when the volume of blood 
in the tank 2 is below the predetermined value and the pumping means 4 
acts to intermittently deliver blood from the accumulator 3. As the 
residual blood volume in the tank 2 decreases, blood is accordingly 
delivered in a smaller amount. Even when the residual blood volume in the 
tank 2 is very small, delivery of a minor amount of blood is maintained. 
It is unnecessary to interrupt blood delivery when the residual blood 
volume in the tank 2 decreases, thereby avoiding blood stagnation in an 
extracorporeal blood circulation circuit. 
The blood reservoir 10 includes the blood tank 2 and a blood delivery 
instrument 6 which includes the blood accumulator 3 and the pumping means 
4. 
As shown in FIG. 6, the blood tank 2 includes a tank housing consisting of 
a main body 23a and a cover 23b both made of rigid resin. The cover 23b is 
fitted on the top end of the housing main body 23a so as to cover the 
upper opening of main body 23a as shown in FIGS. 2 and 6. The cover 23b 
has blood flow inlets 21 and 22 and air vents 27 and 28 as shown in FIG. 
4. The blood flow inlet 22 is connected to a cardiotomy line for feeding 
blood from the operation area. The blood flow inlet 21 is connected to a 
drainage line for feeding blood from a drainage cannula inserted into the 
heart ascending/descending veins of the patient. Received in the housing 
main body 23a are a cardiotomy blood filter 25 four filtering the blood 
incoming from inlet 22 and a venous blood filter 24 for filtering the 
blood incoming from the inlet 21. 
The housing main body 23a has a downward projection 23c. The blood outlet 
26 is formed in the bottom of the projection 23c. 
The housing may be formed of any desired resin, for example, polyearbonate, 
acrylic resin, polyethylene terephthalate, polyethylene, polypropylene, 
polystyrene, polyvinyl chloride, acryl-styrene copolymers, and 
acryl-butadiene-styrene copolymers. Polycarbonatc, acryl resin, 
polystyrene, and polyvinyl chloride are especially preferred. 
Defined within the blood tank housing is a blood reserve portion 29 for 
temporarily reserving blood as shown in FIG. 6. The blood reserve portion 
29 may have any desired volume although it generally has a volume of about 
3,000 to 5,000 ml for adults and about 1,000 to 2,500 ml for children. The 
housing is preferably substantially transparent or semi-transparent, so 
that the volume or state of blood reserved may be readily ascertained. The 
downward projection 23c has a reduced horizontal cross-section so that 
when the volume of blood reserved lowers, the volume of blood reserved or 
a change thereof can be correctly and readily read. As shown in FIG. 3, 
the projection 23c is convergent downward, that is, has a cross-sectional 
area decreasing toward the bottom. Scale marks are printed on the outside 
wall of the projection 23c. The blood tank 2 may also be a flexible tank 
formed of flexible resin. In this case, the blood tank is of the closed 
type. 
Attached at the bottom of the blood tank 2 is the blood delivery instrument 
6 which includes a housing 6a joined to the tank housing 23a. The blood 
delivery instrument 6 fuirther includes the blood accumulator 3 and the 
blood delivery pumping means 4 received between the instrument housing 6a 
and the tank housing 23a. Disposed between the blood tank housing 23a and 
the blood accumulator 3 is a backing 32 for retaing the accumulator 3. The 
backing 32 has a side configured in conformity with one side shape of the 
accumulator 3 when the accumulator 3 is full of the maximum amount of 
blood. 
A blood channel section 35 is defined by the blood delivery instrument 6 on 
its lower side and provides fluid communication between the interior 29 of 
the blood tank 2 and the blood accumulator 3. Disposed in proximity to the 
blood flow outlet 26 of the blood tank 2 is a first check valve 33 which 
permits blood passage from the blood tank 2 to the blood channel section 
35 (and hence, the blood accumulator 3), but restricts or prohibits the 
blood passage in the opposite direction. This first check valve 33 
flnctions as a flowpath control member for shutting off communication 
between the blood tank 2 and the accumulator 3 during operation of the 
pumping means 4 as will be described later. The blood delivery instrument 
6 is provided with a blood exit port 7 in communication with the blood 
channel section 35. Disposed in proximity to the blood exit port 7 is a 
second check valve 34 which permits blood passage to a side downstream of 
the blood channel section 35 (and hence, downstream of the blood 
accumulator 3), but restricts or prohibits blood passage in the opposite 
direction. This second check valve 34 functions as a flowpath control 
member for shutting off blood flow from the downstream side into the 
accumulator side (and hence, blood channel side) when the pumping means 4 
is inoperative as will be described later. 
Each check valve 33, 34 has a disc-shaped movable valve body 33a, 34a and a 
cage 33b, 33b adapted to receive the valve body therein and formed with an 
opening for blood passage. The movable valve body 33a, 34a preferably has 
a specific gravity substantially equal to or slightly lighter than the 
specific gravity of blood so that the valve body may be fully responsive. 
For example, the valve body is made of expanded polyethylene and has a 
thickness of about 1 to 10 mm, especially 3 to 8 mm. 
In another embodiment, the check valve takes the form of a movable valve 
body a part of which is fixedly secured to the housing. Preferably the 
movable valve body is slightly lighter than the specific gravity of blood 
and a hardness of about 3 to 7 on Shore A scale. For example, the valve 
body is made of styrene elastomer oil gel or silicone gel and has a 
thickness of about 1 to 5 mm. 
The blood accumulator 3 is in fluid communication with the blood channel 
section 35 via a blood passage port 31 which is located below or at the 
lower end of the accumulator 3 and formed at a position of the same height 
as the lower end of the blood reserve portion 29 (the outlet 26) of the 
blood tank 2 in a vertical direction. The blood tank 2 has the blood 
reserve portion 29 and the outlet 26 located at a lower end portion 
thereof. The accumulator 3 is located upwards than the outlet 26. The 
blood accumulator 3 extends substantially vertically upward and 
substantially parallel to the projection 23c of the blood tank 2 in this 
embodiment. The accumulator 3 is formed as a bag or bladder of flexible 
resin. Under the condition that blood accumulator 3 is set so as to extend 
upward and parallel to the projection 23c of the blood tank 2, if the 
surface of blood in the tank 2 is below the uppermost end of the interior 
of the accumulator 3, an amount of blood proportional to the blood surface 
in the tank 2 flows into the accumulator 3. Inversely, now that the 
maximum containment amount of the blood accumulator 3 remains unchanged, 
if the surface of blood in the tank 2 is above the uppermost end of the 
interior of the accumulator 3, this maximum containment amount of blood 
flows into the accumulator 3. 
Differently stated, the blood accumulator 3 is a pressure sensitive 
container since a pressure proportional to the volume of blood reserved in 
the tank 2 is applied thereto. When the volume of blood in the tank 2 is 
above a predetermined value (or the surface of blood in the tank 2 is 
above the uppermost end of the interior of the accumulator 3 in the 
illustrated embodiment), the maximum containment amount of the accumulator 
3 becomes preferential to the pressure exerted by the volume of blood in 
the tank 2 so that the accumulator 3 contains the maximum containment 
amount of blood. If the volume of blood in the tank 2 is below the 
predetermined value (or the surface of blood in the tank 2 is below the 
uppermost end of the interior of the accumulator 3 in the illustrated 
embodiment), the accumulator 3 exerts a pressure sensitive function to 
contain blood in an amount proportional to the volume of blood in the tank 
2 (or the height of the blood surface in the tank 2). Thus, the 
accumulator 3 has the function of automatically storing blood in an amount 
proportional to the volume of blood in the tank 2 when the volume of blood 
in the tank 2 is below the predetermined value. 
It is preferred that the blood accumulator 3 does not suck in blood by 
itself, in another parlance, does not have a self-shape-recovery ability. 
If the accumulator 3 is formed to a shape defining a certain internal 
cavity, the accumulator 3 will restore the original shape when blood 
stored therein is displaced by pumping member 4 and the compression load 
by the pumping member 4 is released. The restoring force creates a suction 
force to provide suction of blood from the tank side. Then the accumulator 
has a minimum blood containment amount below which the accumulator cannot 
exert the pressure sensitive function mentioned above. The minimum blood 
containment amount associated with the self recovery force should 
preferably be zero although its presence is acceptable if it is negligibly 
small. The preferred form of the blood accumulator is a flexible bag 
prepared by placing a pair of sheets in close plane contact with a tube to 
form the blood passage port 31 interposed at the lower end, and heat 
sealing the sheets along the periphery to define a sealed interior except 
for the tube. This bag has an internal volume of substantially zero as 
formed. Differently stated, it is preferred that when a load is applied to 
the blood accumulator so as to establish a state that the internal volume 
is substantially zero and then released, the blood accumulator maintains 
the substantially zero volume state. The maximum blood containment amount 
(simply maximum amount or maximum displacement) of blood accumulator 3 is 
preferably about 20 to 500 ml, more preferably about 50 to 300 ml, further 
preferably about 80 to 300 ml although the exact amount varies with the 
maximum volume of blood reserved in the blood tank combined therewith. It 
is preferred that the maximum blood containment amount of the accumulator 
3 is greater than the volume of the channel section 35. Consequently, when 
blood is displaced from the accumulator 3, the entire volume of blood 
contained in the channel section 35 is displaced so that the stagnation of 
blood in the channel section 35 may be minimized. 
The blood accumulator 3 in the illustrated embodiment is entirely formed of 
a flexible material and thus entirely deformable so that the accumulator 3 
may be compressed and deformed when the blood delivery pumping means 4 is 
inflated. However, the blood accumulator is not limited to the entirely 
flexible one. It is acceptable that a portion of blood accumulator 3, for 
example, a portion of the blood accumulator 3 which comes in contact with 
the pumping means 4 is a deformable portion formed of a flexible material. 
Blood contained in the accumulator 3 is displaced by the blood delivery 
pumping means 4 into the channel section 35 and then discharged to an 
outside destination through the exit port 7. When the volume of blood 
reserved in the tank 2 is smaller than the predetermined value, blood is 
delivered in an amount proportional to the residual volume of blood in the 
tank 2. As the residual volume of blood in the tank 2 becomes smaller, the 
amount of blood delivered is automatically reduced to a level approximate 
to zero, but not reduced to zero. That is, the blood reservoir 10 of the 
invention always maintains blood delivery though in a very small amount. 
Thus the interruption of blood delivery never occurs, preventing blood 
stagnation on a side of the extracorporeal blood circulation circuit 
downstream of the blood reservoir 10. 
Since the blood accumulator 3 is a flexible bag, it provides a very low 
resistance to blood inflow and sensitivity to pressure variations so that 
blood may be contained in an amount fully proportional to the residual 
volume of blood in the tank 2. Moreover, the accumulator 3 is designed 
such that it contains the predetermined amount of blood in the duration 
when the volume of blood in the tank 2 is above the predetermined level, 
while the amount of blood contained in accumulator 3 varies in proportion 
of the residual volume of blood in the tank 2 in the duration when the 
volume of blood in the tank 2 is below the predetermined level. The 
maximum containment amount is fixed and this maximum containment amount of 
blood is contained when the volume of blood in the tank 2 is above the 
predetermined level. Then the amount of blood delivered by pumping means 4 
in the normal state can be readily controlled in terms of the number of 
compressions or pulsations per unit time of accumulator 3 by pumping means 
4. A substantially constant amount of blood is delivered per pulsation. 
Satisfactory pulsative blood flow can be easily established. 
The blood accumulator is desired to be fully flexible. One index of 
flexibility is compliance. The blood accumulator preferably has a 
compliance of above 2 ml/sec.multidot.mHg, preferably 5 to 30 
ml/sec.multidot.mHg when the surface of blood in the reserve portion of 
the tank 2 is lower than the uppermost end of the interior of the 
accumulator, differently stated, when the accumulator exerts a pressure 
(or blood level) sensitive function. Further preferably the blood 
accumulator reduces its compliance to a lower value when the surface of 
blood in the reserve section of the tank 2 is above than the uppermost end 
of the interior of the accumulator. The resistance of the accumulator to 
blood inflow can be expressed by an inflow rate of blood into the 
accumulator and the accumulator preferably has a blood inflow rate of 20 
to 600 ml/sec. 
Examples of the flexible resin include polyvinyl chloride, vinyl 
chloride-vinyl acetate copolymers, vinyl chloride-ethylene copolymers, 
vinyl chloride-vinylidene chloride copolymers, vinyl chloride-urethane 
copolymers, vinyl chloride-acrylonitrile copolymers, vinyl chloride-methyl 
methacrylate copolymers, and flexible polyvinyl chloride modified products 
comprising the foregoing polymers and plasticizers, and polyurethane. 
Thermoplastic polyurethanes are especially preferred. The thermoplastic 
polyurethanes may be either thermoplastic polyether polyurethanes or 
thermoplastic polyester poly-urethanes, with the thermoplastic polyether 
polyurethanes being preferred. Especially preferred are thermoplastic 
polyether polyurethanes comprising soft and hard segments. The soft 
segment is preferably formed from polytetra-methylenle ether glycol 
polyethylene glycol and poly-propylene glycol as a main component. The 
hard segment is preferably formed from 1,4-butane diol as a main 
component. The disocyanate includes 4,4-diphenylmethane diisocyanate, 
tolylene diisocyanate, and 1,6-hexamethylene diisocyanate. Most preferred 
polyurethane material is a thermoplastic segmented polyurethane which is 
formed using polytetra-methylene ether glycol as a main component of the 
soft segment, 1,4-butane diol as a main component of the hard segment, and 
4,4-diphenylmethane diisocyanate as the diisocyanate. This polyurethane is 
commercially available under the trade name of Pelecene 2363 from Dow 
Chemical Co. 
The surface of the accumulator which will be wetted with blood is 
preferably antithrombic. The antithrombic surface may be formed by 
applying and fixing an antithrombin to the surface. Exemplary 
antithrombins are heparin, urokinase, HEMA-St-HEMA copolymers, and 
poly-HEMA. 
Preferably, the antithrombic surface is formed by treating a substrate with 
ozone to form functional group-bearing oxides on the substrate surface and 
applying heparin to the surface so that an amino group of heparin forms a 
covalent bond with the functional group directly or through a coupling 
agent. This method permits heparin to be fixed on the blood wetting 
surface without the use of a solvent, minimizing a change of physical 
properties (e.g., flexibility, elasticity and strength) of the substrate 
presenting the blood wetting surface. 
Through ozone treatment, oxides are formed on the substrate surface and 
high reactive functional groups such as aldehyde, ketone, and epoxy groups 
are generated in the oxides. Amino groups of heparin can directly bond 
with these functional groups. For the reason of steric hindrance or other, 
introducing a spacer or coupling agent into these functional groups prior 
to fixation of heparin is easy and useful from the standpoint that the 
suffice allows heparin to develop its activity. The coupling agents may be 
used alone or in admixture of two or more. Compounds having at least two 
aldehyde or epoxy groups are preferred. 
Where two or more coupling agents are used, the preferred sequence is by 
first bonding a coupling agent (spacer coupling agent) in the form of a 
compound having at least two amino groups with the functional groups 
previously introduced in the substrate, to thereby introduce amino acid 
into the substrate, and thereafter bonding heparin to the substrate with 
the aid of a coupling agent (heparin-fixing coupling agent) in the form of 
a compound having at least two aldehyde or epoxy groups. In bonding 
heparin, the coupling agent is preferably admitted into the reaction 
system at the same time as or subsequent to heparin admission. 
Especially when an amino group is introduced using a spacer coupling agent, 
it displays substantially the same reactivity as the amino group of 
heparin in the reaction system so that subsequent fixation of heparin to 
the substrate by the heparin-fixing coupling agent may take place more 
effectively. 
Where the functional group of a coupling agent to directly bond with 
heparin or the functional group introduced into the substrate is an 
aldehyde group, it is preferable to use heparin in which some N-suliate 
groups are desulfurized into primary amino groups. 
The spacer coupling agent is one that forms a bond (covalent bond) with the 
functional group introduced on the substrate by ozone treatment and has at 
least two primary amino groups. Examples of the spacer coupling agent 
having at least two amino groups include polyethylene imine (PEI), 
polyethylene glycol diamine, ethylene diamine, and tetramethylene diamine 
Aldehyde and epoxy compounds are preferable as the coupling agent used for 
fixing heparin to the substrate. Exemplary of the aldehyde compound are 
glutaraldehyde, glyoxal, and succindialdehyde. Exemplary of the epoxy 
compound are polyethylene glycol diglycidyl ether, 1,4-butane diol 
diglycidyl ether, sorbitol diglycidyl ether, and glycerol diglycidyl 
ether. Illustrative examples are Denacol EX-421, 521, 611, 612, 614, and 
614B where the epoxy compound is sorbitol diglycidyl ether; Denacol EX-313 
where the diepoxy compound is glycerol diglycidyl ether; Denacol EX-810, 
811, 851, 821, 830, 832, 841, and 861 where the diepoxy compound is 
polyethylene glycol diglycidyl ether, all commercially available from 
Nagase Chemicals K. K. Denacol EX-313, 421, 512, 521, 810, 811, 821, and 
851 are preferred when the difference of epoxy reactivity is considered. 
In the above-mentioned heparin fixation, coupling-off of heparin is 
minimized since the bond between polyethylene imine fixed to the substrate 
and glutaraldehyde and the bond between glutaraldehyde and heparin are 
both covalent bonds. 
Disposed between the accumulator 3 and a vertically extending side wall of 
the housing 6a of the blood delivery instrument 6 is the blood delivery 
pumping means 4. The pumping means 4 is preferably a flexible bag formed 
of a flexible resin as used in the accumulator and defining a fluid flow 
space 4a therein. The pumping means 4 is in fluid communication with a 
fluid flow port 41 in the housing side wall 6a of the blood delivery 
instrument 6. On use, the port 41 is connected to fluid feed unit 5 for 
feeding fluid for blood delivery as shown in FIG. 1. A compressor built in 
the fluid feeder unit 5 operates to feed or discharge an operative liquid 
or gas to or from the pumping bag 4 for expansion or contraction. Upon 
contraction, the pumping bag 4 does not contact the accumulator bag 3 as 
shown in FIG. 6. Upon expansion, the pumping bag 4 inflates as shown in 
FIG. 9 to compress the accumulator bag 3 against the backing 32 for 
displacing blood out of the accumulator bag 3. The containment for 
receiving the accumulator bag 3 (defined between the blood tank housing 
23a and the blood delivery instrument housing 6a may be sealed 
substantially gas-tight. In this case, the containment is under positive 
pressure upon inflation of the pumping bag 4, but upon contraction of the 
pumping bag 4, the containment is kept under negative pressure which 
facilitates initial inlow of blood into the accumulator bag 3. Since the 
blood delivery pumping means 4 is in the form of a flexible bag which is 
inflated or contracted by feeding fluid into and out of the bag in the 
illustrated embodiment, it causes little damage to the accumulator 3 when 
compressing accumulator 3. Since the accumulator 3 has a deformable 
portion formed of flexible material and upon blood delivery, the pumping 
means 4 acts to deform that deformable portion to displace blood out of 
the accumulator 3, blood can be intermittently discharged from the 
accumulator 3 in an amount proportional to the volume of blood reserved in 
the blood tank 2. 
The blood delivery pumping means 4 can regulate the amount of blood 
displaced out of the accumulator 3 by adjusting the amount or pressure of 
operative fluid introduced in the pumping means 4. The amount of blood to 
be displaced can be readily changed by setting a fixed number of driving 
actions of the pumping means 4 per unit time and adjusting the amount or 
pressure of operative fluid introduced in the pumping means 4. When the 
pumping means 4 is designed so as to displace blood out of the accumulator 
3 while leaving some amount of blood therein, no excessive stresses are 
applied to the accumulator 3 and the sheets forning the accumulator 3 are 
not closely joined, preventing any obstruction against blood inflow into 
the accumulator 3 which would otherwise be caused by close junction. 
In another embodiment, a pumping bag or member can be omitted and pumping 
means of a different structure is constructed as shown in FIG. 10. In this 
embodiment, the containment 47 defined between the blood tank housing 23a 
and the blood delivery instrument housing 6a for receiving the accumulator 
3 is sealed substantially gas-tight. The communication port 41 is 
connected to a pressurizing means in the form of a blood delivery fluid 
feed unit. A compressor built in the fluid feed unit 5 operates to feed or 
discharge an operative liquid or gas to or from the containment 47 so that 
the accumulator 3 itself repeats expansion or restoring contraction 
In the illustrated embodiments, the blood reservoir including the pumping 
means 4 is disposable as a whole. The invention is not limited to these 
embodiments. As shown in FIG. 11, the blood delivery pumping means 4 is 
removable from the blood reservoir since the pumping means 4 does not 
contact blood. The blood reservoir 10 of this embodiment does not have the 
pumping means 4 and the port 41 as integral components and instead, has an 
attachment therefor. More particularly, a blood delivery drive assembly 
including a plate member 45 provided with the port 41 and the pumping 
means 4 is separately furnished. The plate member 45 is attached to an 
opening 6b in the instrument housing 6a. The plate member 45 is provided 
with the engagements 43 and the instrument housing 6a is provided with the 
engagements 42. Through these engagements, the plate member 45 (or the 
blood delivery drive assembly) is tightly attached to the reservoir 10 so 
that the assembly may not be readily removed. 
As seen from FIG. 5, the blood reservoir 10 of the illustrated embodiment 
has two sets of the accumulators 3 and the pumping means 4. The blood 
channel 35 is also partitioned into two blood channels 35a and 35b which 
are not in fluid communication with each other as shown in FIGS. 7 and 8. 
When two or more sets of the accumulators 3 and the pumping means 4 are 
provided, the volume of each the accumulator 3 and the pumping means 4 is 
reduced so that the response of blood inflow and outflow is improved. If 
expansion timing is shifted between two pumping means 4, there can be 
formed a better blood flow. Despite shifted expansion timing between two 
pumping means 4, it never happens that blood flows from one accumulator to 
the other accumulator since two blood channels 35a and 35b are not in 
fluid communication with each other and each accumulator has an 
independent blood channel. The invention is not limited to the illustrated 
embodiment. The accumulator 3 and the pumping means 4 may be provided one 
set or three or more sets. Although the bag adapted to undergo repetitive 
inflation and contraction under the action of operative fluid is used as 
the pumping means 4 in the illustrated embodiment, the invention is not 
limited thereto. For example, a mechanism including a pressure plate 87 in 
contact with one side of a blood accumulator wherein the pressure plate is 
mechanically driven against the blood accumulator may be used as in the 
blood delivery apparatus shown in FIG. 13 to be described later. 
In the illustrated embodiment of the blood reservoir 10 comprising two sets 
of accumulators 3 and pumping means 4 and a blood delivery fluid feed unit 
having a control ability to independently drive the pumping means 4, the 
form of blood flow to be delivered can be selected between a pulsative 
flow and a constant flow by taking into account the state of the patient 
and the artificial lung associated with the circulation line. Additionally 
the mode of blood flow to be delivered can be changed during operation. In 
the illustrated embodiment comprising two sets of accumulators 3 and 
pumping means 4, a substantially constant blood flow is obtained as a 
whole when the phases of blood flows delivered from the respective 
channels are shifted approximately 180 degrees, differently stated, when 
the phases of fluid flows discharged into or out of the pumping means 4 
for blood delivery are shifted approximately 180 degrees Inversely, a 
pulsative blood flow is obtained when the phases of blood flows delivered 
from the respective channels are the same or .+-.30 degrees, differently 
stated, when the phases of fluid flows discharged into or out of the 
pumping means 4 for blood delivery are the same or .+-.30 degrees. Where 
three or more sets of accumulators 3 and pumping means 4 are provided, a 
substantially constant blood flow is obtained when the phases of blood 
flows delivered from the respective channels are shifted an angle of 
360.degree. divided by the number of sets. 
FIG. 12 illustrates a blood delivery instrument 70 according to the 
invention. 
This blood delivery instrument 70 is used in an extracorporeal blood 
circulation circuit having a blood tank. The blood delivery instrument 70 
includes a blood accumulator 3 in communication with a blood outlet of the 
tank and a pumping means 4 for driving accumulator 3 to deliver blood from 
the accumulator 3 outward. As in the first-mentioned embodiment, the blood 
accumulator 3 serves to temporarily store blood in an amount proportional 
to the volume of blood reserved in the tank 2 when the volume of blood in 
the tank 2 is below a predetermined value. The pumping means 4 serves to 
intermittently drive the accumulator 3 so as to displace blood therefrom. 
The blood delivery instrument 70 includes an accommodating housing 71 
having the accumulator 3 and the pumping means 4 received therein and a 
channel housing 73 disposed below the housing 71 and defining a blood 
channel 35 therein. The channel housing 73 has at one end a blood inlet 
port 76 connected to the outlet of the blood tank and at another end a 
blood outlet port 77. The accommodating housing 71 has a bottom configured 
to attach the channel housing 73 thereto and defines an interior space 
where the accumulator 3 and the pumping means 4 are received. The 
accumulator 3 and pumping means 4 may be the same as in the 
first-mentioned embodiment. 
The blood accumulator 3 is in fluid communication with the blood channel 35 
defined in the housing 73 through a blood passage port 31. Disposed in 
proximity to the inlet port 76 of housing 73 is a first check valve 33 
which permits blood flow from the blood tank side to the blood channel 35 
side (and hence, to the accumulator 3), but restricts reverse blood flow. 
Disposed in proximity to the outlet port 77 of the housing 73 is a second 
check valve 34. The check valves illustrated in the figure are ball 
valves. The interior of the pumping means 4 is in fluid communication with 
a port 41 for passing a blood delivery operative fluid. 
In this embodiment, pumping means 4 is configured to the contact 
accumulator 3 at opposite surfaces. More particularly, pumping bag 4 is 
folded and the accumulator bag 3 is interposed between the folded 
sections. Alternatively, the pumping bag 4 is formed in doughnut shape and 
the accumulator bag 3 is disposed at the center. The pumping bag 4 in 
contact with substantially the entire surface of the accumulator bag 3 
ensures effective displacement of blood from the accumulator bag 3. 
Next, the blood delivery fluid feed unit 5 shown in FIG. I is described. 
The blood delivery fluid feed unit 5 is connected to the blood reservoir 10 
through a tube 57 connected to the passage port 41 in communication with 
the pumping means 4. The fluid feed unit 5 has a fluid pump built therein 
for discharging a liquid (e.g., water and physiological saline) or gas 
(e.g., air) into and out of the pumping means 4 to intermittently repeat 
inflow and outflow of the fluid. The fluid feed unit 5 has a front panel 
including a switch section 52 having an input switch for setting a blood 
flow rate per unit time (e.g., a blood flow rate per minute) and/or an 
input switch for setting the number of pulsations per unit time (e.g., 
number of pulsations per minute). A display section 54 is to display the 
input blood flow rate and number of pulsations. The fluid feed unit 5 has 
built therein a computer which when a blood flow rate is input, computes 
the number of pulsations per unit time by considering the maximum capacity 
of the accumulator 3 (the amount of blood contained in the accumulator 
when the residual volume of blood in the blood tank is above a 
predetermined value) and delivers the computed result to the display 
section. Since the blood reservoir of the illustrated embodiment has two 
sets of accumulators and pumping means, the number of pulsations per unit 
time for each accumulator is one-half of the computed number of 
pulsations. Inversely, when a number of pulsations per unit time (e.g., a 
number of pulsations per minute) is input, a blood flow rate per unit time 
is computed by considering the maximum capacity of accumulator 3 and 
displayed at the display section. 
The blood reservoir 10 has a level sensor 51 which is electrically 
connected to fluid feed unit 5, especially a lamp 56 through a control 
circuit. The level sensor 51 is attached to the blood tank 2 at a position 
corresponding to or slightly above the top end of the interior of the 
accumulator 3. When the level sensor 51 detects that the surface of blood 
is below the sensor 51, the lamp 56 flickers to indicate a blood delivery 
amount control mode. At the same time, any flow rate indication on the 
display section 55 disappears. 
It is understood that blood delivery fluid feed unit 5 is applicable to all 
the illustrated embodiments. 
The blood delivery fluid feed unit is not limited to the above-mentioned 
one. Another exemplar blood delivery fluid feed unit is shown in FIG. 32. 
This unit includes a display section 161 for displaying the flow rate 
detected by a flow rate sensor located downstream of the blood reservoir, 
a knob 162 for setting the pressure of blood delivery operative fluid, a 
display section 163 for displaying the pressure of blood delivery 
operative fluid, and a mode switch 164 for selecting a blood flow mode 
between a constant flow and a pulsative flow. While the number of 
pulsations of pumping blood delivery operative fluid per unit time is 
fixed, a knob is manually operated to adjust the pressure of blood 
delivery operative fluid for thereby adjusting the flow rate of blood. 
That is, this blood delivery fluid feed unit is to adjust the flow rate of 
blood by adjusting the force of the pumping means compressing the 
accumulator for thereby adjusting the amount of blood displaced from the 
accumulator (the amount of blood discharged from the blood contained in 
the accumulator). 
FIG. 13 shows a blood delivery apparatus according to another embodiment of 
the invention. 
This blood delivery apparatus 80 includes a blood delivery means 81 and a 
compression means 90. The blood delivery means 81 includes a blood channel 
having at one end a blood inlet port 76 connected to a blood outlet of a 
blood tank 2 and at another end a blood outlet port 77. The blood delivery 
means 81 further includes an accumulator 83 in fluid communication with 
the blood channel. The accumulator 83 is constructed as a vertically 
contractible bellows. The accumulator 83 in the form of a bellows is 
adapted to contain blood in an amount proportional to the volume of blood 
reserved in the blood tank when the volume of blood reserved in the blood 
tank is below the predetermined value. That is, when the volume of blood 
reserved in the blood tank is below the predetermined value, the top end 
of the accumulator bellows 83 lowers in accordance with the surface of 
blood in the blood tank. 
The accumulator bellows 83 has a flat top end on which a pressure plate 87 
is rested T he pressure plate 87 is fixedly secured to a piston rod 89b of 
a cylinder 89a to construct a blood delivery pumping means. The cylinder 
89a is coupled to a hydraulic or pneumatic pressure generator 92 through a 
conduit 91 so that piston rod 89b is vertically moved by the operation of 
the generator 92. When the piston rod 89b is moved down, the pressure 
plate 87 urges the accumulator 83 downward. The accumulator bellows 83 is 
squeezed between the pressure plate 87 and a support plate 88 to reduce 
its interior volume to displace the blood therefrom to the channel and 
then to an artificial lung 93. Disposed in proximity to the inlet port 76 
is a first check valve 33 which permits blood flow from the blood tank 
side to the blood channel side (and hence, to the accumulator 83), but 
restricts reverse blood flow. Disposed in proximity to the outlet port 77 
is a second check valve 34. The check valves illustrated in the figure are 
ball valves. 
FIG. 14 shows a blood delivery apparatus according to a still further 
embodiment of the invention. The basic construction of this blood delivery 
apparatus 100 is the same as the foregoing apparatus 80. The difference 
resides in the use of flowpath control means instead of the check valves. 
This blood delivery apparatus 100 includes a blood delivery means 81 and a 
compression means. The blood delivery means 81 includes a blood channel 
having at one end a blood inlet port connected to a blood outlet of a 
blood tank 2 and at another end a blood outlet port. The blood delivery 
means 81 further includes a accumulator 83 in fluid communication with the 
blood channel The accumulator 83 is constructed as a vertically 
contractible bellows. The accumulator 83 in the form of a bellows is 
adapted to contain blood in an amount proportional to the volume of blood 
reserved in the blood tank when the volume of blood reserved in the blood 
tank is below the predetermined value. The accumulator bellows 83 has a 
flat top end on which a pressure plate is rested. The pressure plate is 
fixedly secured to a piston rod 89b of a cylinder 89a to construct a blood 
delivery pumping means. The cylinder 89a is coupled to a hydraulic 
pressure generator 92 through a conduit so that the piston rod 89b is 
vertically moved by the operation of the generator 92. When the piston rod 
89b is moved down, the pressure plate urges the accumulator bellows 83 
downward. The accumulator bellows 83 is squeezed between the pressure 
plate and a support plate 88 to reduce its interior volume to displace the 
blood therefrom to the channel and then to an artificial lung 93. 
Disposed in proximity to the inlet port is a first flowpath control means 
96 in the form of a clamp with an electromagnetic valve, for example. 
Disposed in proximity to the outlet port is a second flowpath control 
means 97. These flowpath control means 96 and 97 and the hydraulic 
pressure generator 92 are connected to a controller 95. The controller 95 
controls so as to render first flowpath control means 96 operative to shut 
off the flowpath to establish blockage between the accumulator 83 and the 
blood tank 2 when the piston rod is on a downward stroke (the pressure 
plate is moved down). When the piston rod is on an upward stroke (the 
pressure plate is moved up), the controller 95 controls the second 
flowpath control means 97 operative to shut off the flowpath to prevent 
blood entry into the accumulator 83 from a downstream side. 
FIG. 16 shows a blood delivery apparatus according to a still further 
embodiment of the invention. 
The basic construction is the same as the apparatus shown in FIG. 11. The 
blood delivery pumping means is removably attached to the blood reservoir 
since the pumping means does not contact blood. The blood reservoir 10 of 
this embodiment does not have a pumping means as an integral component and 
instead, has an attachment therefor. More particularly, a blood delivery 
drive assembly including a plate member 45 and a pumping means is 
separately furnished The plate member 45 is attached to an opening 6b in 
the channel section housing 6a. The plate member 45 is provided with the 
engagements 43 and the channel section housing 6a is provided with the 
engagements 42. Through these engagements, the plate member 45 (or the 
blood delivery drive assembly) is tightly attached to the reservoir 10 so 
that the assembly may not be readily removed. The blood delivery drive 
assembly includes the pumping means in the form of a curved press plate 46 
which is secured to one end of a drive shaft 46a extending through the 
plate member 45. The drive shaft 46a at another end is provided with a 
piston rod connector 46b through which the drive shaft 46a is removably 
connected to a piston rod 89b of a cylinder 89a. When the piston rod 89b 
is moved to the left in FIG. 16, the pressure plate urges and collapses 
the accumulator bag 3 to reduce its internal volume to displace blood 
therefrom. The thus displaced blood flows to an artificial lung side. The 
cylinder 89a is coupled to a hydraulic pressure generator (not shown) for 
driving the piston rod. 
Referring to FIGS. 17 to 23, there is illustrated a blood reservoir 130 
according to a further embodiment of the invention. FIG. 17 is a front 
elevational view of the blood reservoir, FIG. 18 is a left side view of 
the reservoir, FIG. 19 is a top view of the reservoir, FIG. 20 is a XX--XX 
cross section of FIG. 17, FIG. 21 is a XXI--XXI cross section of FIG. 18, 
FIG. 22 is a partial cross-sectional view of FIG. 17, and FIG. 23 is a 
schematic view for explaining the operation of the blood reservoir of FIG. 
17. 
The basic construction of the blood reservoir of this embodiment is the 
same as the reservoir of FIGS. 1 to 9. The difference is the shape and 
arrangement of a accumulator and blood delivery pumping means and the 
shape of valves. 
As in the first-mentioned embodiment, a blood reservoir 130 includes a 
blood tank 2 and a blood delivery instrument 6 which includes a blood 
accumulator 3 and a pumping means 4. 
The blood tank 2 includes a tank housing consisting of a main body 23a and 
a cover 23b both made of rigid resin. The cover 23b is fitted on the top 
end of housing main body 23a so as to cover the upper opening of the main 
body 23a as shown in FIGS. 17 and 18. The cover 23b has blood flow inlets 
21 and 22 and air vents 27 and 28 as shown in FIG. 19. The blood flow 
inlet 22 is connected to a cardiotomy line for conveying blood from the 
operation area. The blood flow inlet 21 is connected to a drainage line 
for conveying blood from a drainage cannula inserted into the heart 
ascending/descending veins of the patient. Received in the housing main 
body 23a are a cardiotomy blood filter 25 for filtering the blood incoming 
from the inlet 22 and a venous blood filter 24 for filtering the blood 
incoming from the inlet 21. 
The housing main body 23a has a downward projection 23c and a blood outlet 
26 (shown in FIG. 21) formed in the bottom of the projection 23c. Defined 
within the blood tank housing is a blood reserve portion 29 for 
temporarily reserving blood. 
Attached at the bottom of the blood tank 2 is blood delivery instrument 6 
which includes a pair of retainer plates 66a and 66b fixedly secured to 
the tank housing 23a. The blood delivery instrument 6 further includes the 
blood accumulator 3 and the blood delivery pumping means 4 received 
between retainer plates 66a and 66b. 
A blood channel section 35 is defined by blood delivery instrument 6 near 
its bottom and provides fluid communication between the blood reserve 
portion or the interior 29 of the blood tank 2 and the blood accumulator 
3. Disposed in proximity to blood flow outlet 26 of blood tank 2 is a 
first check valve 33 which permits blood passage from the tank 2 to the 
channel section 35 (and hence, the accumulator 3), but restrains blood 
passage in the opposite direction. This first check valve 33 functions as 
a flowpath control member for shutting off communication between the tank 
2 and the accumulator 3 during operation of the pumping means 4. The blood 
deliver instrument 6 is provided with a blood exit port 7 in communication 
with the blood channel 35. Disposed in proximity to blood exit port 7 is a 
second check valve 34 which permits blood passage from the channel 35 (and 
hence, accumulator 3) to a downstream side, but restrains blood passage in 
the opposite direction. This second check valve 34 functions as a flowpath 
control member for shutting off blood flow from the downstream side into 
the accumulator side (and hence, blood channel side) when pumping means 4 
is inoperative. 
Each check valve 33, 34 has a disc-shaped movable valve body 33a, 34a a 
part of which is secured to the housing. Preferably the movable valve body 
is slightly lighter than the specific gravity of blood and a hardness of 
about 3 to 7 on Shore A scale. For example, the valve body is made of 
styrene elastomer oil gel or silicone gel and has a thickness of about 1 
to 5 mm. 
The blood accumulator 3 is in fluid communication with the blood channel 
section 35 via a blood passage port 31 which is located below or at the 
lower end of the accumulator 3 and formed at a position of the same height 
as the lower end of the blood reserve portion 29 of the blood tank 2 in a 
vertical direction. The blood accumulator 3 includes a tubular portion 
which extends a certain distance vertically upward and parallel to the 
projection 23c of the blood tank 2 and bends in a horizontal direction and 
a bag or bladder portion which is connected to the tubular portion and 
extends horizontally. The bag portion of the blood accumulator 3 is formed 
as a bag of flexible resin. When blood flows into the bag portion, it 
inflates in a height direction of the blood tank 2. If the surface of 
blood in the blood tank 2 is below the uppermost end of the interior of 
the blood accumulator 3, an amount proportional to the blood surface in 
the tank 2 of blood flows into the blood accumulator 3. Inversely, since 
the maximum containment amount of the blood accumulator 3 remains 
unchanged, even if the surface of blood in the blood tank 2 is above the 
uppermost end of the interior of the blood accumulator 3, this maximum 
containment amount of blood flows into the blood accumulator 3. 
Since the uppermost end of the interior of the blood accumulator 3 shown in 
FIG. 17 is positioned at a lower level than the embodiment shown in FIG. 
2, the range (blood surface height range) where the blood accumulator 3 is 
pressure sensitive (blood surface sensitive) is narrower. In the range 
where blood accumulator 3 is pressure sensitive, if the volume of blood in 
the tank 2 is above a predetermined value (that is, the surface of blood 
in the tank 2 is above the uppermost end of the interior of the 
accumulator 3 in the illustrated embodiment), the maximum containment 
amount of the accumulator 3 becomes preferential to the pressure exerted 
by the volume of blood in the tank 2 so that the accumulator 3 contains 
the maximum containment amount of blood. If the volume of blood in the 
tank 2 is below the predetermined value (that is, the surface of blood in 
the tank 2 is below the uppermost end of the interior of the accumulator 3 
in the illustrated embodiment), the accumulator 3 exerts a pressure 
sensitive function to contain blood in an amount proportional to the 
volume of blood in the tank 2 (or the height of the blood surface in the 
tank 2). Thus, the accumulator 3 has the function of automatically 
containing blood in an amount proportional to the volume of blood in the 
tank 2 when the volume of blood in the tank 2 is below the predetermined 
value. 
For the accumulator 3 and the pumping means 4, those described in the 
first-mentioned embodiment are useful It is understood that in accordance 
with the configuration of the accumulator 3, the pumping means 4 is also 
configured so as to extend horizontally with respect to the blood tank 2. 
When an operative fluid is admitted into the pumping means 4, it is 
inflated to compress accumulator 3 in cooperation with the pair of 
retainer plates 66a, 66b, thereby displacing blood from the accumulator 3. 
As seen from FIG. 18, the blood reservoir of this embodiment also has two 
Frets of accumulators 3 and pumping means 4. The blood channel 35 is also 
partitioned into two blood channels 35a and 35b which are not in fluid 
communication with each other, as shown in FIG. 20. Unlike the embodiment 
shown in FIG. 8, two blood channels 35a and 35b are provided with blood 
outflow ports 7a and 7b, respectively, as shown in FIG. 18. 
FIG. 24 shows a blood reservoir having a heat exchanger and an artificial 
lung integrated therewith The basic construction of this blood reservoir 
is the same as in FIGS. 17 to 23 except that the blood channel section is 
vertically elongated and the blood outflow port is horizontally oriented 
so that a heat exchanger 67 and an artificial lung 68 may be mounted. The 
description of the basic construction is omitted and only the arrangement 
of the heat exchanger 67 and the artificial lung 68 is described 
The artificial lung 68 used herein is a heat exchanger built-in hollow 
membrane fiber type artificial lung as shown in FIG. 24. The heat 
exchanger 67 is located upstream and artificial lung 68 is located 
downstream. 
The heat exchanger 67 includes a housing provided with two blood inlet 
ports 67a (only one shown) connected to two blood outlet ports of the 
blood reservoir and blood outlet ports 67b as well as an inlet port 67c 
and an outlet port (not shown) for a heating medium. A multiplicity of 
heat exchanging tubes 67d are received in the housing and at opposite ends 
tightly secured to the housing through partitions (not shown). In this 
heat exchanger, blood passes through the tubes and the heating medium 
passes outside the tubes. The tubes may be made of metals having high heat 
conductivity, for example, stainless steel, aluminum and copper or resins. 
The tubes preferably have an inner diameter of 0.1 to 10 mm, more 
preferably 0.5 to 5 mm. Usually about 100 to 2,000 tubes are assembled as 
a bundle which is received within the housing. 
The heat exchanger used herein is not limited to the illustrated type 
wherein blood passes inside the heat exchange tubes (internal blood 
perfusion type). A heat exchanger of the type wherein blood passes outside 
the heat exchange tubes (external blood perfusion type) is also useful. 
The artificial lung 68 includes a housing having a blood inlet port 68a and 
a blood outlet port 68b. A bundle consisting of a multiplicity of gas 
exchanging hollow membrane fibers 68c is received in the housing. The 
hollow membrane fibers 68c at opposite ends are tightly secured to the 
housing through partitions (not shown). The housing is provided with a 
first header opposed to one partition and having a gas inlet port 68d and 
a second header opposed to the other partition and having a gas outlet 
port (not shown). The hollow membrane fibers have microscopic pores in the 
membrane wall through which oxygen is added to blood and carbon dioxide is 
removed from blood. The hollow membrane fibers used herein generally have 
a gage of 5 to 80 .mu.m, preferably 10 to 60 .mu.m, a porosity of 20 to 
80%, preferably 30 to 60%, a pore size of 0.01 to 5 .mu.m, preferably 0.01 
to 1 .mu.m, and an inner diameter of 100 to 1,000 .mu.m, preferably 100 to 
300 .mu.m. 
Hydrophobic polymers are often used to form the hollow membrane fibers. 
Exemplary hydrophobic polymers include polypropylene, polyethylene, 
polytetrafluoroethytene, polysulfone, polyacrylonitrile and cellulose 
acetate. Preferred among others are polyolefin resins, especially 
polypropylene. More specifically, hollow membrane fibers of polypropylene 
in which micropores are formed by a drawing or solid-liquid phase 
separation method are desirable. Usually 10,000 to 80,000 hollow membrane 
fibers are distributed over the transverse cross section of the housing. 
In this artificial lung, blood passes outside the hollow membrane fibers 
while gas passed through the hollow membrane fibers. An artificial lung of 
the type wherein blood passes through the hollow membrane fibers (internal 
blood perfusion type) is also acceptable. When the blood delivery 
instrument mentioned above produces a pulsative flow of blood, the use of 
an artificial lung of the hollow membrane fiber type is preferred because 
it little absorbs the pulsative flow. The use of an artificial lung 
comprising porous flat membranes is less desirable because the flat 
membranes are deformed to a large extent to dampen the pulsation. 
The order of a heat exchange and an artificial lung may be reversed if 
desired. 
FIGS. 25 to 27 shows a blood reservoir 140 according to a still further 
embodiment of the invention. FIG. 25 is a front elevation of the blood 
reservoir; FIG. 26 is a side view of the reservoir; and FIG. 27 is a 
partial cross-sectional view of the reservoir of FIG. 25. Since the basic 
construction of this blood reservoir is the same as in FIGS. 17 to 23 
except for the blood delivery mechanism, the description of common 
components is omitted herein. 
The blood reservoir 140 of this embodiment includes a blood accumulator 
side housing 143 of a substantially fixed volume in communication with a 
blood channel section 35 and a blood accumulator side movable membrane 141 
of flexible material disposed below the housing for constructing a blood 
accumulator 3. Also included are a pumping side housing 145 of a 
substantially fixed maximum volume in communication with a fluid port 41 
and a blood delivery pumping side movable membrane 142 of flexible 
material disposed above the housing for constructing a blood delivery 
pumping means 4. The blood accumulator side housing 143 and the pumping 
side housing 145 are combined and fixedly secured such that the movable 
membranes associated therewith may face in contact (substantially plane 
contact), thereby constructing a blood delivery instrument 6. Since the 
movable membrane 141 on the blood accumulator side and the movable 
membrane 142 on the pumping means side are separate, the movable membrane 
on the blood accumulator side is not sucked when a negative pressure is 
created in the interior of the pumping means upon exhaustion of operative 
fluid. This prevents the accumulator itself from carrying out blood 
suction and thus eliminates any influence on the pressure sensitivity of 
the accumulator. The movable membrane on the accumulator side is one free 
of self-shape-recovery ability. 
FIGS. 28 to 31 shows a blood reservoir 150 according to a still further 
embodiment of the invention. FIG. 28 is a front elevation of the blood 
reservoir; FIG. 29 is a side view of the reservoir; FIG. 30 is a partial 
cross-sectional view of the reservoir; and FIG. 31 is a schematic view for 
explaining the operation of the blood reservoir of FIG. 28. Since the 
basic construction of this blood reservoir is the same as in FIGS. 17 to 
23 except for a blood delivery mechanism, the description of common 
components is omitted herein. 
The blood reservoir 150 of this embodiment includes a blood accumulator 
side housing 151 in communication with a blood channel section 35 by a 
hole 153 and having a limited maximum volume and a bag-shaped flexible 
member 152 received in the housing 151 and in communication with the 
exterior for constructing a blood accumulator 3. Received within the 
flexible bag is a blood delivery pumping means 4. The blood delivery 
pumping means 4 used herein is preferably a flexible bag formed of 
flexible resin as used in the previously mentioned blood accumulator 
member and defining a space 4a therein. That is, the blood delivery 
instrument of this blood reservoir 150 has a dual bag structure. The space 
4a defined in the blood delivery pumping means 4 is in fluid communication 
with a fluid passage port 41 disposed at a lower end thereof. On use, the 
port 41 is connected to a blood delivery fluid feed unit and a compressor 
built in the fluid feed unit operates to discharge a fluid (either liquid 
or gas) into and out of the interior space of the pumping bag 4 whereby 
pumping bag 4 undergoes repetitive inflation and contraction. Upon 
contraction, the pumping bag 4 is in contact with the accumulator bag 3, 
but does not force accumulator bag 3 as shown in FIG. 30. Upon inflation, 
pumping bag 4 inflates to exert an outward pressure against the flexible 
bag of the accumulator as shown in FIG. 31, reducing the volume of the 
accumulating bag to displace blood out of the accumulating bag. 
Since the deformable portion (flexible bag) of the accumulating member and 
the deformable portion (flexible bag) of the pumping means are separate in 
this blood delivery instrument too, the movable membrane on the blood 
accumulator side is not sucked when a negative pressure is created in the 
interior of the pumping means upon exhaustion of operative fluid This 
prevents the blood accumulator itself from carrying out blood suction and 
thus eliminates any influence on the pressure sensitivity of the blood 
accumulator. The movable membrane on the blood accumulator side is one 
free of self-shape-recovery ability. 
Next, the blood delivery apparatus shown in FIG. 15 is described. 
The blood delivery apparatus 120 includes a sensor 121 attached to blood 
tank 2, a blood feed pump 122 connected to the outlet of the tank 2, a 
motor 123 associated with pump 122 for operating it, and a controller 124 
electrically connected to the sensor 121 and the motor 123. The controller 
124 has a blood delivery rate regulating function of delivering blood in 
an amount proportional to the volume of blood reserved in the blood tank 2 
when the volume of blood reserved in the blood tank 2 is below a 
predetermined value. 
The sensor 121 is attached to an end of a tube 126 connected to the bottom 
of the tank 2 so that the sensor is in fluid communication with the tank. 
A pressure transducer is preferred as the sensor used herein. It is also 
acceptable to use a load cell to directly measure the weight of the blood 
bank. 
The blood feed pump 122 may he a constant pressure pump, roller pump or 
peristaltic pump, with the constant pressure pump being preferred. In the 
illustrated embodiment, a constant pressure pump is used as the blood feed 
pump. The constant pressure pump includes a centrifugal pump, turbine pump 
and screw pump. 
The sensor 121 detects the pressure at the bottom of the tank 2 and 
delivers detection signals at suitable time intervals (for example, of 
about 10 seconds) to the controller 124. It is understood that the 
pressure at the bottom of the tank 2 is in proportion to the volume of 
blood reserved in the tank 2. The controller 124 includes a switch panel 
128 which includes a flow rate input switch and a switch for inputting a 
residual blood volume for switching to a flow rate regulating mode. The 
controller 124 has a residual blood volume computing function of 
converting a signal from the sensor 121 into a value X corresponding to 
the residual volume of blood in the blood tank 2. The controller 124 also 
has a function of comparing a residual blood volume value A (liter) input 
from the residual blood volume input switch with the actual residual blood 
volume value X (liter). It maintains the normal blood delivery mode if A 
X, but switches into a blood delivery rate regulating mode to the control 
feed pump 122 in that mode if A&gt;X. That is, the flow rate of blood to be 
delivered is regulated after the actual volume X of blood in the blood 
tank 2 is below the preset residual blood volume value A Specifically, 
provided that the flow rate input switch inputs a flow rate of B 
liter/min., the control is made so as to provide a flow rate of blood 
delivered Y=B/A.times.X. The invention is not limited to this method of 
controlling the blood flow rate in a linear proportional manner. For 
example, control is made such that the blood flow rate changes in a 
curvilinear proportion as given by Y=B/A.sup.2 .times.X.sup.2. If A&lt;X is 
resumed, transition from the blood delivery rate regulating mode to the 
normal blood delivery mode occurs to resume blood delivery in the preset 
flow rate C. 
There has been described a blood reservoir comprising a blood tank, a blood 
accumulator connected in fluid communication with an outlet of the tank 
for receiving blood from the tank, and a pumping means for driving the 
accumulator to displace blood out of the accumulator for blood delivery 
purpose. The accumulator is adapted to store blood in an amount 
proportional to the volume of blood in the tank when the volume of blood 
in the tank is reduced below a predetermined value. The pumping means 
operates to intermittently displace blood out of the accumulator. The 
pumping means is able to regulate the amount of blood displaced out of the 
accumulator. Therefore, when the volume of blood in the tank is reduced 
below the predetermined value by an octopus which the blood inflow volume 
to the tank decreases, the blood is delivered in an amount proportional to 
the residual blood volume in the tank. In other words, it becomes that the 
blood delivery volume from the tank is substantially same the blood inflow 
volume to the tank after the volume of blood in the tank is reduced below 
the predetermined value. 
As the residual blood volume is reduced, the amount of blood delivered is 
reduced and approaches to zero, but does not equal zero. Blood delivery is 
maintained even in a very small amount. Since no interruption of blood 
delivery occurs, no blood stagnation occurs in the extracorporeal blood 
circulation circuit on a side downstream of the blood reservoir. 
Also there has been described a blood reservoir comprising a blood tank, a 
blood accumulator connected in fluid communication with an outlet of the 
tank for receiving blood from the tank, a first check valve disposed 
between the tank and the accumulator for restraining blood passage to the 
tank side, a second check valve disposed downstream of the accumulator for 
restraining blood passage from a side downstream of the accumulator, and a 
pumping means for driving the accumulator for delivering blood out of the 
accumulator. The accumulator is adapted to store blood in an amount 
proportional to the volume of blood in the tank when the volume of blood 
in the tank is reduced below a predetermined value. Since two check valves 
are included, a satisfactory blood flow can be formed so that the 
accumulator may exert its function more effectively. 
Also there has been described a blood delivery instrument for use in an 
extracorporeal circulation circuit including a blood tank, comprising a 
coupling connected to the tank, a blood accumulator connected to the 
coupling for receiving blood from the tank, and a pumping means for 
driving the accumulator to deliver blood from the accumulator to a 
destination. The accumulator is adapted to store blood in an amount 
proportional to the volume of blood in the tank when the volume of blood 
in the tank is reduced below a predetermined value. The pumping means 
operates to intermittently displace blood out of the accumulator 
Therefore, when the volume of blood in the tank is reduced below the 
predetermined value by an octopus which the blood inflow volume to the 
tank decreases, the blood is delivered in an amount proportional to the 
residual blood volume in the tank. In other words, it becomes that the 
blood delivery volume from the tank is substantially same the blood inflow 
volume to the tank after the volume of blood in the tank is reduced below 
the predetermined value. 
As the residual blood volume is reduced, the amount of blood delivered is 
reduced and approaches to zero, but does not equal zero. Blood delivery is 
maintained even in a very small amount. Since no interruption of blood 
delivery occurs, no blood stagnation occurs in the extracorporeal blood 
circulation circuit on a side downstream of the blood delivery instrument. 
Also there has been described a blood delivery instrument for use in an 
extracorporeal circulation circuit including a blood tank, comprising a 
coupling connected to the tank, a blood accumulator connected to the 
coupling for receiving blood from the tank, a first check valve disposed 
in proximity to the coupling for restraining blood passage from the 
accumulator to the tank side, a second check valve disposed downstream of 
the accumulator for restraining blood passage from a side downstream of 
the accumulator, and a pumping means for driving the accumulator to 
deliver blood from the accumulator to a destination. The accumulator is 
adapted to store blood in an amount proportional to the volume of blood in 
the tank when the volume of blood in the tank is reduced below a 
predetermined value since two check valves are included, a satisfactory 
blood flow can be formed so that the accumulator may exert its function 
more effectively. 
Also there has been described a blood delivery apparatus for use in an 
extracorporeal circulation circuit including a blood tank, comprising a 
blood delivery amount regulating means for regulating the amount of blood 
delivered so as to be in proportion to the volume of blood in the tank 
when the volume of blood in the tank is reduced below a predetermined 
value. Therefore, when the volume of blood in the tank is reduced below 
the predetermined value by an octopus which the blood inflow volume to the 
tank decreases, the blood is delivered in an amount proportional to the 
residual blood volume in the tank. In other words, it becomes that the 
blood delivery volume from the tank is substantially same the blood inflow 
volume to the tank after the volume of blood in the tank is reduced below 
the predetermined value. As the residual blood volume is reduced, the 
amount of blood delivered is reduced and approaches to zero, but does not 
equal zero. Blood delivery is maintained even in a very small amount. 
Since no interruption of blood delivery occurs, no blood stagnation occurs 
in the extracorporeal blood circulation circuit on a side downstream of 
the blood delivery apparatus. 
Although some preferred embodiments have been described, many modifications 
and variations may be made thereto in the light of the above teachings. It 
is therefore to be understood that within the scope of the appended 
claims, the invention may be practiced otherwise than as specifically 
described.