Note: Descriptions are shown in the official language in which they were submitted.
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25088-35D
This is a division of my copending Canadian Patent Application
386,631 filed September 24th, 1981.
The present invention relates to a system for the ex~racorporeal
circulation of the blood for a patient undergoing an operation on the lung or
heart to reresh the blood of the patient and always circulate the blood
through the body in place of the lungs and heart of the patient.
Systems for e~tracorporeally circulating the blood comprise a
blood withdrawing line for drawing of the venous blood from the patient, an
artificial lung provided on the line, a reservoir for the withdra~n blood, a
blood supply line for feeding ~he blood from the reservoir to the artery of
the patient, and a blood supply pump provided on the blood supply line and
serving as an artificial heart. With such systems, it is most critical to main-
tai~n the amount of the blood withdrawn from the body of the patient in balance
w~th tlle supply oE the blood to the body to keep the amount o the blood
circulated through the body constant at all times~ In controlling the amount
o blood circulation through the body, bleeding from the site operated on, etc~
must also be considered since bleeding reduces the amoun* of blood in the body~
Conventionally the amount of blood circulation through the body is controlled
by the operator through manual procedures for driving the blood withdrawing
~0 pump and blood supply pump and replenishing ~he blood reservolr with trans-
usion blood~ This mode of control involves many items of manipulation, and
the system must be controlled i~em-wise promptly based on immediate judgment
while watching incessantly changing conditions of the patient, i.e. arterial
and venous blood pressures, measurement of amount of bleeding, amount of blood
in the reservoir and electrocardiogram. Thus the operator must be trained for
controlling the system. Additionally ~he operator suffers from much fatigue
when the operation takesa prolonged period of time.
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SUMMARY OF THE INVENTION
The invention provides a system for controlling a pulsatile pump
serving as an artificial heart provided on an extracorporeal circulation line,
the system comprising means for generating a trigger pulse upon detecting
contraction of the heart of a patient for spontaneous circulation, a circuit
for generating a trigger pulse in accordance with a heart rate set for forced
circulation, means for selecting one of the trigger pulses, and means for
driving the pulsatile pump in response to the selected trigger pulse.
The system for the extracorporeal circulation of the blood as
disclosed herein is adap~ed to automatically control the blood supply to the
body so that the arterial pressure will be maintained suitably in a required
range. The amount of blood to be withdrawn from the body is au*omatically
cc~ntrolled so that the venous pressure of the patient will be maintained at an
appTo~lmately constant level. rrhe system is adapted to control the amount o
bloocl to be supplied to the body of the patient and the amount of blood to be
withdrawn therefrom to keep the amount of circulation of the blood through the
body approximately constant. The system can smoothly effect a change from the
spontaneous circulation of the blood by the cardiac force of the patient to
the forced circulation of the blood by an extracorporeal system or vice versa.
The intercorporeal circulation of the blood is assisted by an
extracorporeal circulation system while the blood is being spontaneously cir-
culated through the body by the cardiac force of the patient so that the
intracorporeal circulation of the blood will not be interrupted even when the
heart stops temporarily.
; The system for the extracorporeal circulation of the blood com-
prises a blood withdrawing line, an artificial lung provided on the line, a
reservoir for the blood withdrawn, a blood supply line for sending out the
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blood from the reservoir, a blood supply pump provided on the blood supply
line and serving as an artificial heart, means for detecting that the venous
pressure has exceeded a predetermined upper limit level, a blood pressure trans-
ducer for measuring the arterial pressure, means for increasing the amount of
blood to be withdrawn when the venous pressure has exceeded the upper limit
level, and means for controlling the blood supply pump in response to an output
from the blood pressure transducer to maintain the arterial pressure in a
predetermined required range.
The venous pressure detecting means comprises a vertical tube
having an upper end opened to the atmosphere and a blood sensor provided at a
position of specified height for the vertical tube for detecting *hat the blood
level has reached the position. This arrangemen~ detects the venous pressure
more acc~rately than a blood pressure transducer used as the venous pressure
d~kec~ n~eans. For the same purpose, two vertical tubes may be used which
aro :in comm~mication with each other at upper portions thereof. When the
blood in one of the vertical tubes rises beyond ~he communicating portion, the
blood 10ws over this portion into the other tube. The overflow is detec~ed by
a sensor. If the vertical tube or sensor is movable upward or downward, the
upper limit level of the venous pressure is variable. The venous pressure to
be detected is preferably the central venous pressure.
The means for controlling the blood supply pump preferably com-
~rises an upper limit detecting circuit for detecting that the arterial pres-
sure has exceeded a predetermined upper limit value, a lower limit detecting
circuit for detecting that the arterial pressure has lowered below a predeter-
mined lower limit value, and a control circuit for stopping the blood supply
pump upon detecting the upper limit and for operating the blood supply pump
upon detecting the lower limit. It is preferable to use a pulsatile pump as
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the blood supply pump.
Other features and advantages of this invention will become
apparent from the following description of an embodiment with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF T}IE DRAWINGS
Figure 1 is a diagram of a preferred embodiment of the invention
showing a circuit for extracorporeal blood circulation and including a block
diagram of part of the electric circuit associated wi~h the circuit;
Figure 2 is a block diagram showing the construction of a control
unit in detail;
Figure 3 is a sectional view showing a cannula;
F~igures 4, 5 and 6 show other examples of central venous pressure
n(ljustin~ units;
Figure 7 sho~s another exanlple of blood supply line; and
Figure 8 is a block diagram showing a system for adjusting the
pressure of the le~t atrium.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The system of this invention for extracorporeal blood circulation
includes a blood withdrawing line 1, an overflow line 2, an aspiration line 3
and a blood supply line 4. These lines 1 to 4 are each made of a flexible
tube. The lines 1 to 3 are provided with rotary pumps 11 to 13 respectively.
The rotary pump comprises rollers adapted for a circular motion to draw and
forward the blood through the tube by squeezing the tube, forming a continuous
flow of blood. The line 4 is provided with a pulsatile pump 14 which is
operated by compressed air suppIied thereto intermittently to intermittently
force the blood through the line 4 as a pulsating flow.
The line 1 for withdrawing the venous blood from the body of the
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patient has two cannulas 15 connected to one end thereof. As seen in Figure ~,
the cannula 15 comprises an outer tube 16 having a slightly tapered forward
end, and an ilmer tube 17 having a forward end projecting outward from the for-
ward end of the other tube 16 and a rear end extencling outward from the outer
tube 16. The forward end of the outer tube 16 is formed with a large number
of holes 18. The rear end of the outer tube 16 is connected to the line 1.
The orward ends of the cannulas 15 are inserted into the superior and inferior
venae cavae of the patient individually to draw the venous blood into the line
1 through the holes 18 and the outer tubes 16. The line 1 is provided with
an oxygenerator and a heat exchanger 6. The oxygenerator functions as an
arkificial lung, in which the venous blood withdrawn from the body of the
patient gives off carbon dio~ide and takes up oxygen. The heat exchanger main-
t~lns the blood at the desired temperature and, when needed, lowers the blood
-tomperat~lre. The blood thus refreshed is led into a blood reservoir 7 and
stored therein. Alternatively the heat exchanger may be disposed between the
reservoir 7 and the pump 14 on the blood supply line 4, or on a portion of the
line 4 downstream from the pump 14. A collapsible bag 9 for checking whether
or not the blood is being withdrawn smoothly is provided on ~he blood withdraw-
ing line 1 at a location between the shunt line 5 to be described later and
2n the cannulas 15. ~hen the withdrawn blood is flowing smoothly through the line
1, the bag 9 is filled with the blood and is thereby inflated. If the line 1
is collapsed somewhere between the cannulas lS and the bag 9, or if the blood
is not withdrawn from the body for one reason or another, no blood is supplied
to the bag 9. Since the blood in the line 1 is drawn by the pump 11 which is
in operation at all times, the bag 9 is emptied of the blood and collapses.
A sensor 27 is provided for detecting the state of the bag 9, i.e. whether the
bag 9 is inflated or collapsed. The detecting signal of the sensor 27 is fed
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to a control unit 40. If the bag 9 collapses, an alarm goes on, informing the
operator of the trouble occurring in the blood withdrawing line 1. When neces-
sary, the blood supply pump 14 may be brought out of operation in the event of
the line 1 malfunctioning. In the present embodiment, however, the pump 14
need not be stopped even if the line 1 is blocked since the blood is withdrawn
through the overflow line 2 provided in parallel with the line 1.
A bottom portion of the blood reservoir 7 is connected by a shunt
line 5 to a portion of the line 1 upstream from the pump 11. The line 5 has an
electromagnetic valve 32. The valve 32 and the electromagnetic valve 33 to be
lQ described later are each a pinch valve. When the valve 32 is open, the blood
in the reservoir 7 is aspirated by the pump 11 through the line 5 and returned
to the reservoir 7 by way of the oxygenerator and heat exchanger 6. Since
a major portion oE the blood drawn and forwarded by the pump 11 is supplied
via the line 5, the amount of venous blood withdrawn Erom the body is small
when the valve 32 is open. ~hen the valve 32 is closed, no blood is supplied
through the line 5, with the result that the suction by the pump 11 acts en-
tirely on the cannula 15 to withdraw an increased amount of venous blood from
the patient.
The over1Ow line 2 is provided with a unit 20 for adjusting the
central venous pressure ~hereinafter Teferred to as "CVP"), which is the mean
pressure of the superior vena cava pressure and the inferior vena cava pressure
and is given by the inner tubes 17 o the pair of cannulas 15. The CVP adjust-
ing unit 20 comprises a support member 23 the position of which is vertically
adjustable, and two vertical tubes 21 and 22 mounted on the support member 23.
The vertical tube 21 is connected at its lower end to the inner tubes 17 of
the two cannulas 15, while the lower end of the other vertical tube 22 is in
communication with the inlet of the pump 12. The upper end of the vertical tube
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21 communicates through a horizontal tube with an upper portion o~ the vertical
tube 22, which has an upper end extending upward beyond the communicating
portion and opened to the atmosphere. A sensor 24 for detecting an overflow
of blood is disposed at a location slightly below ~he communicating portion of
thP vertical tube 22. Each of the sensor 24, the above-mentioned sensor 27,
and the sensors 25, 26 to be described later is a photoelectric detector, for
which infrared rays are preferably used as the beam to be projected. Other
sensors, such as those u~ilizing ultrasonic waves or capacitance, are of course
usable.
Since the forward ends of the inner tubes 17 of the cannulas 15
are inserted intothe superior and inferor venae cavae individually as already
statedl portions of the venous blood flow into the inner tubes 17 individually
from the two venae cavae and join together, whereby the blood pressures of the
t~o veins are aver~ged. The venous blood rises through the vertical tube 21
in accordance ~ith the Inean blood pressure, i.e. the CVP. The level oE the
blood in the vertical tube 21 represents the CVP. The upper limit level of CVP
is determined by the height of the upper end oE the vertical tube 21 from the
heart of the patient. When the CVP is higher than the upper limit level, the
blood within the vertical tube 21 overflows the tube 21 into the vertical tube
22, so that this is detected by the sensor 2~. The over10w oE blood is
aspirated by the pump 12 and led into the reservoir 7. The upper limit level
o CVP can be set to a desired value by adjusting the level of the support
member 23.
The aspiration line 3 is provided for aspirating the blood released
from the site of the patient operated on. The blood is sent to the reservoir
7 by the pump 13. The blood through the lines 2 and 3, although led directly
into the reservoir in Figure 1, may be fed to the oxygenerator and heat
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exchanger 6 and then forwarcled to the reservoir 7 when so required.
The blood supply line 4 has one end connected to a bottom portion
of the reservoir 7 and the other end connected to a cannula which is inserted
into the ascending aorta o~ the patient. The refreshed blood stored in the
reservoir 7 is passed through the line ~ into the aorta by the pulsatile pump
14 which is an artlficial heart~ The blood through the line 4 is pulsatile
and therei`ore resembles ~he arterial blood forced out from the heart to produce
a physiolog}cally favorable influence on the patient. A reservoir 8 disposed
above the blood reservoir 7 for storing the blood to be transfused has a bottom
portion connected to an upper portion of the reservoir 7 by a tube 37. The
tube 37 has an electromagne~ic valve 33. The sensor 25 detects that only a
small amount of blood remains in the reservoir 7, while the sensor 26 detects
that the reservoir 7 is f.illed with ~he blood ~o its upper limit level. When
tho small amount o:E blood remai.ning in ~he r~servoir 7 is detected by the
sQnsor 25, ~he electronlagnetic valve 33 is opened to supply the blood from the
reservoir 8. When the sensor 26 detects that the reservoir 7 has been filled
with the blood to its upper limit level, the valve 33 is closed to discontinue
the supply of blood. The blood in the reservoir 8 may be supplied to the
reservoir 7 by way of the oxygenerator and heat exchanger 6. The reservoir 8
may be connected to the aspiration l~ne 3. Ringerls solution and other
solutions or drugs needed for the patient under operation are admixed with the
blood in the reservoir 7. Preferably an artificial kidney ~not shown) is pro-
vided for filtering off such components from the blood in the reservoir 7 when
the blood is diluted with these solutions to an excessive volume.
The compressed air for driving the pulsatile pump 1~ is supplied
from an air source through a line 34, which is provided with a pressure regulator
36, tank 35 and electromagnetic valve 31. As will be stated later, the valve
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31 is controlled to open and close intermittently.
The control unit 40 controls the electromagnetic valves 31, 32
and 33. The unit 40 receives detecting signals from the sensors 24, 25, 26 and
27, output signals from blood pressure transducers 41 and 42 for detecting the
venous blood pressure and the arterial blood pressure ~hereinafter referred to
as "VP" and "AP" respectively) of the patient, output signals from an electro-
cardiograph 43 for preparing an electrocardiogram for the patient, and output
pulses from a heat rate generator 44. The blood pressure transducers 41 and
42 measure the blood pressures of the vena cava and the aorta respectively.
~hen desired, the blood pressures of the superior and inferor venae cavae may
be measured individually, and the mean value of the measurements may be used
as the VP (i.e. CVP).
Figure 2 shows the construction of the control unit 40 in detail.
The signals of the transducer 42 representing the AP and those of the electro-
cardiograph 43 are sent to a monitor 45 equipped with a cathode-ray tube ~GRT),
on which the waveform of AP and the electrocardiogram are displayed. While
the heart of the patient is in operation, the blood is circulated through the
body by the force of cardiac contraction. This mode of blood circulation is
termed "spontaneous circulation." On the other hand, the intracorporeal cir-
culation of the blood by the extracorporeal sys*em of thisinvention, parti-
cularly by the pulsatile pump 14, is termed "forced circulation." The forced
circulation can be effected by the pump 14 also during the spontaneous circula-
tion because there is the need to assist in the blood circulation by the pump
14 when the spontaneous circulation is to be changed over to the forced
circulation and vice versa, whereby the change-over can be accomplished smooth-
ly. The AP signal from the blood pressure transducer 42 and the output signal
from the electrocardiograph 43 are used as triggers for starting the pump 14
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during the spontaneous circulation. A trigger generating circuit 46 produces
a trigger pulse when the AP signal waveform has reached a peak. A trigger
generating circuit 47 produces a ~rigger pulse upon the rise of R wave in the
electrocardiogram. With reference to the AP waveform and electrocardiogram on
the monitor 45, the operator can select one of the two trigger pulses by a
selecting switch 48. The selected trigger pulse is sent to an AND circuit 54
and to a timer 51.
Por the forced circulation, the heart rate generator 44 produces
trigger pulses o frequency set by its setting device 4~a. The heart rate can
lQ be set as desired by the setting device 4~a. The trigger pulse from the
generator 44 is fed to an AND circuit 55. A switch 49 is used for setting the
forced circulation. When the forced circulation is set by the switch 49, a
hlgll ~ level slgnal is given to an OR circuit 52.
It ls llkely that the heart of the patlent wlll stop temporarlly
w:ithout undergolng periodlc contraction when spontaneous circulatlon is changed
to forced circulation and vice versa. If the heart fails to Eunction for
spontaneous circulation, the blood will not circulate through the body, so that
the circulation mode must be changed over to forced circulation temporarily.
The timer 51 is reset by the trigger pulse of the generating circuit 46 or 47.
If the timer 51 is not reset again upon lapse of a predetermined period of time,
e.g. 2 seconds, after resetting, the timer produces an H level signal, which
is fed to the OR circuit 52. When forced circulation is set by the switch 49,
or when the heart of the patient does not repeat contraction even upon the lapse
of 2 seconds, the OR circuit 52 produces an H level signal, which is delivered
to the AND circuit 55. Accordingly the trigger pulse from the heart rate
generator 44 passes through the AND circuit 55 and then through an OR circuit
56 and is fed to a delay circuit 57. The H level signal from the OR circuit
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52 is inverted by a NOT circuit 53 to a low ~L) level signal, which is given
to the AND circuit 54. Accordingly the AND circuit 54 inhibits passage of the
trigger pulse from the switch 48. If forced circulation is not set, and the
heart is repeating contraction with a period of within 2 seconds, the output
of the OR circuit 52 is at ~ level, and the output of the NOT circuit 53 is
at H level. In this case, the trigger pulse from the generating circuit 46 or
47 passes through the AND circuit 54 and is fed to the delay circuit 57 through
the OR circuit 56. The AND circuit 55 prevents passage of the trigger pulse
from the generator 4~.
The delay circuit 57 delays the trigger pulse fed thereto for
a predetermined period of time. This is of importance during spontaneous
circulation. In the case of spontaneous circulation, the pump 14 for supplying
the blood assists the heart of the patient in supplying the blood, so that the
~w~ l~loocl supplies must be in synchron.ism. It is preferable that the pump l~
~llpply thc blood with a time delay after the arterial blood is supplied by the
heart. This is termed "counter pulsation." The delay circuit 57 determines
this delay time, which is preferably so determined as to be dependent on the
period of systole of the heart. The delay time is obtained, for example, by
multiplying the previous period of systole measured or the mean value of
preceding periods of systole by a suitable percentage. The measurement of the
period and the calculation of the delay time can of course be performed auto-
matically by a control circuit (not shown). The percentage is variable as
desired.
The width of the delayed trigger pulse is shaped to resemble
the systole time of the heart by a pulse width setting circuit 58. The control
pulse delivered from the circuit 58 is sent through AND circuits 59 and 60
to the electromagnetic valve 31 to open the valve. The valve 31, when opened,
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permits supply of compressed air to the pump 14 to contract the pump 14 and
supply the blood. According~y the width of the output pulse of the circuit 58
determines the contraction time of the pump 14. Preferably the contraction
time corresponds to the systole time of the heart. The pulse width is calculat-
ed also based on the period of systole of the heart. In the case of forced
circulation, the delay time of the circuit 57 and the pulse width of the cir~
cuit 58 are determined preferably in accordance with the heart rate set by
the generator 44.
The AP is used also for controlling the start and discontinuance
of the operation of the pulsatile pump 14. The AP signal from the blood pres-
sure transducer 42 is applied to a peak hold circuit 61 and a mean value
calculating circuit 62. While the heart of the patie~t is in operation and
also while the pump 14 is in operation, the arterial blood is pulsating.
Ascordingly the AP signal has a pulsatile waveform. The peak value of the
ulsatile AP signal, corresponding to the systolic pressure, is held by and ssnt
out ~rom the hold circuit 61. The systolic pressure signal is fed to an upper
limit detecting circuit 63 and a lower limit detecting circuit 64. An upper
limit value ~e.g. 150 mm Hg) or the systolic pressure is set on the upper
limit detecting circuit 63. When the systolic pressure input signal is in ex-
cess of the upper limit value, the circuit 63 emits an H level signal. A
lower limit value (e.g. 100 mm Hg) or the highest blood pressure is set on the
lower limit detecting circuit 64. If the systolic pressure input signal
is below the lower limit value, the circuit 64 delivers an H level signal. The
upper limit value and the lower limit value are variable.
The detecting signal from the upper limitdetecting circuit 63
is sent through an OR circuit 67 to the set input terminal of a flip-flop 69.
The detecting signal from the lower limit detecting circuit 64 is sent through
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an OR circuit 68 to the reset input terminal of the flip-flop 69. The flip-
flop 69 is initially reset. When the flip-flop 69 is resetJ the inverted out-
put thcreof is at H level, and at this time, the control pulse of the circuit
58 is sent ~hlough the AND circuit 59 to the valve 31. When the flip-flop 69
is set, the inverted output thereof is at L level, so that the passage of the
control pulse is prevented. Consequently the pump 14 is brought out of opera-
tion when the highest AP value exceeds the upper limit value, whereas the pump
14 is initiated into operation when the value drops below the lower limit value.
The highest AP value is always maintained at a level between the upper limit
value and the lower limit value.
While the pump 14 is held out of operation, no peak appears in
the AP signal. When the blood supply pump is not a pulsatile pump but a rotary
pump, the blood is continuously forced into the artery of the patient~ so that
no p~ak appoars in th~ AP signal. The mean value calculating circuit 62 is
provid~d to meot such a situation. The peak hold circuit 61 has the function
oE producing a no-pea~ signal when no pulse appears in the AP signal for a
specified period of time. The no-peak signal is applied to the calculating
circuit 62, whereupon the circuit 62 functions to calculate and deliver the mean
value of the AP signal every specified period of time. The mean value signal
is sent to upper and lower limit detecting circuits 65 and 66, on which upper
and lower limit values are set respectively. When the mean value signal exceeds
the upper limit value and when the signal drops below the lower limit value,
the circuits 65 and 66 each produce an H level detecting signal~ which is fed
to the flip-flop 69 in the same manner as above.
The detecting signal ~H level3 from the sensor 24 of the CVP
adjusting unit 20 has its waveform shaped by a waveform shaping circuit 73 and
then applied to the set input terminal of a flip-flop 74. The VP signal from
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the blood pressure transducer 41 is fed to a mean value calculating circuit 71,
in which the mean value thereof is calculated every speciied time interval.
The mean value signal is delivered to a lower limit detecting circuit 72, on
which a lower limit value for the venous blood pressure is set. When the mean
VP value drops below the lower limit value, the circuit 72 emits an H level
detecting signal, which is given to the reset inpu~ terminal of the flip-flop
74. The flip-flop 74 is initially reset. While the flip-flop 74 is reset7
the inverted output signal thereof is at H level~ The H level signal opens
the electromagnetic valve 32. When the flip-flop 74 is set by an overflow
detecting signal from the sensor 24, the flip-flop delivers an inverted output
at L level to close the valve 32. Conse~uently the pump 11 withdraws an in-
creasod amount oE blood as already described. Thus, if the CVP exceeds the
llpper lim:~t level ~e.~. 10 to 2~ Inm llg), Eor example, due to the con~ostlon o~
bloo~ the bocly~ the valve 32 closes, whereas if the mean VP value drops below
the lower limit value (e.g. several mm Hg), the valve 32 opens. The CVP is
therefore maintained at an approximately constant level at all times.
The blood pressure transducer 41 and the circuits 71 and 72 are
not always necessary; the valve 32 may be controlled only with the detecting
signal of the sensor 24. In this case, the electromagnetic valve 32 is held
open at all times and is closed only while the sensor is detecting an overflow,
whereby the CVP can be kept approximately constant i the upper limi~ for the
CVP is set at a suitable level.
The detecting signals from the sensors 25 and 26 are fed to a
valve control circuit 81. When the sensor 25 detects that the blood in the
reservoir has reduced to below a specified level, the circuit 81 emits an H
level signal to open the valve 33 until ~he sensor 26 gives an upper limit level
detecting signal. The H level signal is sent through a NOT circuit 82 to the
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AND circuit 60. Accordingly when the blood remaining in the reservoir is found
to be in a small amount, the control pulse from the circuit 58 does not pass
the AND circuit 60, and the motor 14 comes to a stop. This prevents air from
flowing into the artery of the patient. However, if the level to be detected
by the sensor 25 is set at a relatively high level, the pump 14 need not al-
ways be stopped even if the sensor 25 emits a detecting signal.
Figures 4, 5 and 6 show other examples of CVP adjusting units.
With reference to Figure 4, a vertical tube 21 has an extension 21a extending
vertically beyond the portion thereof communicating with a vertical tube 22.
The extension 21a communicates at its upper end with the tube 22. When the
CVP increases abruptly beyond its upper limit level, the pressure in excess of
the upper limit level can be measured by the extension 21a. A sensor 24 may
be disposed in the vicinity of the communicating portion of the vertical tube
Figure S shows pairs of vertical tubes 21A, 22A; 21B, 22B; and
21C, 22C. The vertical tubes 21A to 21C have communicating portions at differ~
ent levels. The other vertical tubes 22A to 22C are provided with sensors 24A
to 24C for detecting an overflow of the blood, respectively. A plurality of
CVP measuring levels can be set on this CVP adjusting unit. When the detecting
signals from the sensors 24A to 24C are used for controlling the opening degree
o~ the valve 32, the CVP is controllable in a finer more accurate manner.
With the arrangement of Figure 5, the vertical tubes 22A, 22B are provided with
electromagnetic valves 38A, 38B, respectively. These valves 38A, 38B are
open usually and are closed when the corresponding sensors 24A, 24B have detect-ed an overflow of blood. The valves are opened again when the CVP lowers to
eliminate the overflow.
The overflow line 2 shown in Figure 6 is provided only with a
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vertlcal tube 21 the upper end of which is open to the atmosphere. The line 2
has an electromagnetic valve 39 positioned closer to the pump 12. The vertical
tube 2l is fixed in place, while a sensor 24 is movable upward or downward
along the tube 21 as supported on the tube. The valve 39 is closed usually
but is opened when the sensor 24 detects the blood reaching the level of the
sensor. Thus the blood is aspirated through the line 2 as is the case with an
overflow. The upper limit level for the CVP is settable as desired by varying
the level of the sensor 24.
Pigure 7 shows another example of blood supply line. Between a
blood reservoir 7 and a pump 14, the blood supply line ~ is provided with a
rotary pump 91 and an electromagnetic valve 93 positioned downstream from the
pump 91. In parallel with the rotary pump 91, a return line is connected to
~he line 4, with another electromagnetic valve 92 provided on the return line.
~o~ ~rcod circulation, the pumps 91, 14 operate, and the valve 92 is closed
~;ith ~lle valve 93 opened, whereby the blood in the reservoir 7 is aspirated by
tlle pump 91 and intermittently forced out by the pump 14. lf the highest AP
value exceeds an upper limit value, the valve 92 is opened and the valve 93 is
closed, so that the blood circulates through the return line and the pump 91
without flowing into the pump 14. At this time, the pump 14 may be in or out
of operation. When the highest AP value drops below a lower limit value, the
valve 92 is closed again and the valve 93 is opened.
While the heart of the patient is in operation to circulate the
blood spontaneously, the pressure of the left atrium ~hereinafter referred to
as "LAP`') can be measured. Accordingly the blood circulation can be so con-
trolled that the left side system of the heart and the right side system of the
heart will function in good balance. The LAP reflects the function of the
left heart system, while the CVP reflects the function o the right heart system.
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91~i7;2
The range of desired values of LAP ~e.g. 8 to 15 mm Hg) is predeterminedg and
the CVP is so adjusted that the LAP will be maintained in this range at all
times.
With reference to Figure 8, the LAP is detected by a pressure
transducer 101. The means LAP value is calculated at a specified time interval
by a mean value calculating circuit 102. The upper limit value ~e~g. 15 mm Hg)
of the desired range of LAP values is set on an upper limit detecting circuit
103. When the output from the circuit 102 exceeds the upper limit value, the
circuit 103 emits an upper limit detecting signal. The lower limit value (e.g.
8 mm Hg) of the desired LAP range is set on a lower limit detecting circuit 104.
When the LAP drops below the lower limit value~ the circuit 104 emits a lower
limit detecting signal. Level control means 105 raises or lowers the upper
limit level of CVP in the CVP adjusting unit 20. With the unit 20 shown in
Figure 1, the vertical tu~es 21, 22 and the support member 23 are raised or
lo~crcd~ With the arrangement shown in Figure 6, the blood sensor 24 is raised
or lowerecl. When the detected LAP value is above the upper limit setting1 the
upper limit level for CVP is slowly lowered until the LAP lowers below the
upper limit value. Conversely if the detected LAP value is below the lower
limit~ the upper limit level for the CVP is slowly raised~ The rise of the GVP
upper limit level is stopped when the LAP exceeds the lower limit value. In
this way, the LAP is maintained in the desired range at all times.
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