Note: Descriptions are shown in the official language in which they were submitted.
The present invention rela-tes to a system for the
extracorporeal circulation of -the blood for a patient undergoing
an operation on the lung or heart to refresh -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 extracorporeally circula-ting the blood com-
prise a blood withdrawing line for drawing off the venous blood
Erom the patien-t, an artificial lung provided on the line, a
reservoir Eor the withdrawn blood, a blood supply line for feeding
the 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to maintain the amount of the blood withdrawn from the body of the
patient in balance with the supply of the blood to the body to
keep the amount of the blood circulated through the body cons-tant
at all times. In controlling the amount of blood circulation
-through the body, bleeding from the site operated on, etc. must
also be considered since bleeding reduces the amount of blood in
the body. Conven-tionally the amount of blood circula-tion through
.~-.. ~, ~
7 3 ~ 7
the body is controlled by the operator through manual procedures
for driving the blood withdrawing pump and blood supply pump and
replenishing the blood reservoir with transfusion blood. This
mode of control involves many items of manipulation, and the
system must be controlled item-wise promptly based on immediate
judgment while watching incessantly changing conditions of the
patient, i.e. arterial and venous blood pressures, measurement of
amoun-t of bleeding, amount of blood in the reservoir and electro-
cardiogram. Thus the operator must be trained for controlling the
system. Additionally the operator suffers from much fatigue when
the operation takes a prolonged period of time.
SUMMARY OF THE INVENTION
The invention provides a system for circulating the
blood extracorporeally comprising: a blood withdrawing line, a
reservoir for the blood withdrawn, means for detec-ting that the
venous pressure has exceeded a prede-termined upper limit level,
said means comprising first and second vertical tubes communicating
with each other at their upper ends and being vertically adjust-
able, at least one of the vertical tubes having an upper end open
to atmosphere, and a blood sensor positioned to
detect blood flowing over the communicating portion from one of the
vertical tubes to the other; and means for increasing the amount
of blood to be withdrawn when the venous pressure has exceeded the
upper limit level.
The sys-tem for the extracorporeal circulation of the
blood as disclosed herein is adapted 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 automatically controlled so tha-t the
venous pressure of the patient will be maintained at an approxi-
mately constant level. The system is adapted to control the amount
of blood to be supplied to the body of the patient and the amount
of blood to be withdrawn therefrom to keep the amount of circula-
tion of the blood through the body approximately constan-t. The
system can smoothly effect a change from the spontaneous circula-
tion of the blood by the cardiac force of the patient to the
forced circulation of the blood by an extracorporeal system or a
change reverse to the above.
The intracorporeal circulation of the blood is assisted
by an extracorporeal circulation system while the blood is being
spontaneously circulated 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 extra-
7~7
co~oreal circula.tlon oi~ the blood comprises a bloodithdra~ing line 7 an artlficial lun~ provi~ed on the
line, a reservoir for the blood withdra~m, a blood
suPpl,~ 'ine Lor sendin$ out the blood from the reservoir,
a blood sup~ pump ~-rovided on the blood su-opl~T line
and serving as an artificial heart, means for detecting
that the venous pressure has exceeded a predeterilllned
u~?per lil~li-t level, a blood ~reSsure transducer for
measuring the arterial pressure, means for increasing
the amoun-t of blood to be withdrawn when the venous
pressure has exceeded the upper limit level, and means
for controlling the blood su~pl~- ~ump in res~onse to
an output frorrl the blood pressure transducer to main-
tain the arterial pressure in a predetermined
required range.
The venous pressure detecting means comprises
a vertical tube having an u~er end opened to the
atmosphere and a blood sensor provided at a positi.on of
specified heigh-t for the vertical tube for detecting
that the blood level has reached tne position. ~his
arrangement detects the venous pressure more accurately
than a blood pressure transducer used as the venous
pressure detecting means. ~or the same purpose, t~o
vertlcal tubes ma,~ be used which are in communication
wi-th each other at upper portions thereofO ''i,hen the
. ~ ~
'7'~'7
blood in one o~ the vertical tubes rises beyond the
communicatin~ -oortion, the blood flows over this portion
into -the o~er tube. 'Ihe overflow is detected by a
sensor. If the vertical tube or sensor is movable
upward or do-~nward, the upper limi~ level oc` the venous
pressure is variableO ~he venous pressure to be
etected is preferably the central venous pressure.
The means for controlli:ng t~e blood su.pply
pump preferably comprlses an upper limit detecting
clrcult for detectln~ that the arterlal pressure has
exceeded a predetermined upper li.nit value, a lower
limit detecting circuit for detec-ting th~t the arterial
pressure has lowered belovr a predetermined lower
limit value, and a control circuit for stopping the
blood supply pump upon detectlng t'^e upper limit and for
operatin~ -the blood supply pump upon detectin~ -the
lower limit. It is preferable to use a pulsatile pump
as the blood supply pump.
Other features and advantages of thls lnvention
will become apparent from the followlng descrlptlon of
an embodlment ':;lth reference to the accompan~Tlng
~rawings.
BRI~ DES~RIPTION O~''l'H~ DRA'IINGS
~i,3. 1 ls a diagram of a preferred embodiment
o:c` the inventlon showlng a clrcult for e~tracorporeal
7~;~7
blood circulation and including a blocl~ diagram of
~art OI the electric circuit associated with the circuit;
~ig. 2 is a block diagram showing the construc-
tion of a control unit in detail;
ig. 3 is a sectional view showing a cannula;
Eigs. 4, 5 and 6 show other examples of
central venous pressure adjusting units;
Fig. 7 shows another example of blood supply
line; and
~ig. 8 is a block diagram showing a system for
adjusting tke pressure of the left atrium.
DES~RIPTION 0~ Th~ PR~l~'ERL~ED h~iBOD~'~'!ENT
The system of this invention for extracorporea
blood circulation includes a blood withdrawin~ line 1,
an overflow line 2, an asplration 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 supplied thereto intermittently to
intermittently force the blood throu~h the line 4 as a
pulsating flow.
-.
77~i~
~ he line 1 for withdra~i1ing the venous blood
fro~ tl~e body of the patient has two cannulas 15 connectea
to one end t'~ereof. As seen in -~iig. 3, the cannula 15
comprlses an outer tube 16 having a slightly ta-pered
I or~rard end, and an inner tube 17 having a forward end
projecting outward from the forward end of the outer tube
16 and a rear end extending out~ard from -the outer tube
1~. The forward end oi^ the outer tube 16 i5 formea with
a large n~er OI holes 18. The rear end of the outer
tube 16 is connected to the line 1. The forward 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
f~L~c-tions as an artificial lung, in which the venous
blood withdrawn from the body of the patient gives off
; carbon dioxide and takes up oxygen. The heat exchanger
maintains the blood at the desired temperature and9 when
needed, lowers the blood temperature. The blood thus
refreshed is led in-to a blood r~servoir 7 and s-tored
-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 por-tion of the line 4
downstream from the pump 14. A collapsible bag 9 for
'7~
checking whether or not the blooa is being withdrawn
smoothly is provided on the blood withdrawing line 1
at a location between the shunt line 5 to be de~cribed
later ana the cannulas 15. ;~hen the withdrawn blood is
f`lowing smoothly through the line 1, the bag 9 is filled
ith the blood and is thereby inflated. If thè line 1
is collapsed somewhere between the cannulas 15 and the
'oag 9, or if the blood is no-t 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 bv 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 detect-
ing signal of the sensor 27 is fed to a con-trol uni-t 40.
If the bag 9 collapses, an alarm goes on, informing the
operator of the trouble occurring in -the blood with-
dra~!ing line 1. When necessary 9 the blood supply pump
14 may be brought out of operation in the event of the
line 1 malfunctionin~. In the present embodiment,
however, the pump 14 need not be sto~ped 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
5 connected by a shunt line 5 to a portion of the line 1
7~
ups-Gr2am from the pump 11. The line 5 has an electro-
magne~ic valve 32. The valve 32 and the electromagnetic
valve 33 to be clescribed later are each a pinch valve.
i~hen Ihe valve 32 is open, the blood in the reservoir 7
is aspirated b~r the p~ 11 through the line 5 and
returned to the reservoir 7 by ~ay OI the oxygenerator
ana heat e~changer 6. Since a major portion of the
blood arawn and for~Narded b~T the pump 11 is supplied
via the line 5, the amount of venous blood withdrawn
from the body is small when the valve 32 is open. When
the valve 32 is closed, no blood is su-oplied through
the line 5, with the result that the suction by the
pump 11 acts entirely on the cannula 15 to withdraw an
increased amount of venous blood from the patient.
The overflow line 2 is provided with a uni-t 20
for adjusting the central venous pressure (hereinafter
referred to as "~VP"), v~hich is the mean pressure of
the superior vena cava pressure and the inferior vena
cava pressure and is given by -the inner tubes 17 of the
pair of cannulas 15. The CVP aajusting unit 20
com~rises 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 i-ts lower end to the inner tubes 17 OI
the -two cannulas 15, while the lower end of the other
5'~
ld
vextical tube 22 is in co:nmunication ~!ith the inlet
of the p~p 12. T'~le u~per enG OI the ver-tical tube
21 communicates throu~l a horizontal tube ~ith an upper
~ortion of the vertical tube 22, ~.hich ha~ an u?per
end extending u~ ard beyond the communicating portion
and opened to the atmosphere. A sensor 24 for detec-ting
an overflo~ of blood is disposed at a loca-tion sligh-tly
below the communicating portion of the vertical tube 22.
Each of the sensor 24, the above-mentioned sensor 27,
and the sensors 25, 26 to be described later is a photo-
electric detector, for which infra.rec. rays are
preferably used as the beam to be projected. Other
sensors, s-uch 2S those utilizing ultrasonic waves or
capacitance, are of cou-rse usable.
~ince the forward ends of the inner tubes 17
of the cannulas 15 are inserted into the superior and
inferor venae cavae individually as already stated,
portions of the venous blood flow into the inner tubes
17 individually from the -two venae cavae and join togeth-
er, whereby the blood pressures of the two veins are
averaged. The venous blood rises through the ver-tical
tube 21 in accordace with the mean blood pressure, i.e.
the CVP. The level of the blood in the ver-tica.l tube 21
represents the CVP. The up~er limit level of CVP is
determined by the height of the upper end of the vertical
11
tube 21 from the heart OI the patient. 'ilhen -the ~JP i5
higher than the up,er limit level, the blood v,i-thin the
vertical tube 21 overflo~Js the tube 21 into the vertical
tube 22, so that this is detected by the sensor 24. The
overflo~;r of bloocl is aspira~ed by the pump 12 and led
in-to the reservoir 7. The unper li,mi-t level of CVP can
be set to a desired value by adjustin~ the level of the
support member 23.
The as~iration 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 rese-rvoir in ~ig. 1, may be fed to
the oxygenerator and heat-exchanger 6 and then for~/arded
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 ~f~hich is inserted into the
ascendin~ aorta of the patient. ~he refreshed blood
stored in -the reservoir 7 is passed through the line 4
into the aorta by the pulsatile p~p la which is an
arti~icial heart. The blood through the line 4 is
pulsatile and therefore resembles the arterial blood
forced out from the heart to produce a physiologically
favorable influence on the patient. A reservoir 8 :-
12
aisposed above the blood reservoir 7 for storing theblood to be transI`used has a bottom portion connected
to an u-oper portion of the reservoir 7 by a tube 37.
The tube 37 has an electromagnetic valve 33. The sensor
25 detects that only a small amount of blood remains
in the reservoir 7, while the sensor 26 detects that
t~e reser~rolr 7 is filled with the blood to i-ts upper
limit level. ~iYhen the small amount of blood remaining
in the reservoir 7 is detected b~ the sensor 25, the
electromagnetic valve 33 is opened to supply the blood
from the re~ervoir 8. When the sensor 26 detects that
the reservoir 7 has been filled with the blood to its
upper li~it 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 line 3. Ringer's solution and other
solutions or 2.rugs needed for the patient under opera-
tion are admixed wi-th the blood in the reservoir 7.
Preferably an artificial kidney (not shown) is provided
for filtering off such components from the blood in the
reservoir 7 when the blood is diluted with these solu-
tions -to an excessive volume.
The compressed air for ~riving the pulsatile
pump 14 is supplied from an air source through a line 34,
7~5
].3
which is ~ro~ided v~!ith ~ -pressure re~ulator 36, -tank
35 a.nd electroma~netic va.lve 31. As will be s-ta-ted
later, -the valve 31 is controlled to open and close
in.ermittently.
The control unit ~0 controls the electromagne-tic
valves 31, 32 and 33. The u~i~ 40 receives detecting
signals from the sensors 24, 25, 26 and 27, output si~nals
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" respectivel.y)
of the patient, output signals from an electrocardio-
~raph 43 for preparing an electrocardiogram for the
patient, and output pulses from a heat rate generator
44. The blood pressure tranoducers 41 and 42 measure
the blood pressures of the vena c va and the aorta
res.pectively. ~'Ihen desired, the blood pressures of the
superior and inferor venae cavae ma~- be measu-red
individually, and the mean value of the measurements may
be used as the VP (i.e. CVP).
~ig. 2 shows the construction of the control
unit 40 in detail. The si~nals of the transducer 42
representin the AP and those of the electrocardiograph
43 are sent to a monito-r 45 equipped with a cathode-ray
tube (CRT), on which the waveform of AP and the electro-
cardio~ram are displayed. While the heart of the patient
'5 7
14
is in operation, the blood is circulated through the
body by the force of cardiac contraction. This mode of
blood c rculation is termed "spontaneous circulation."
On the other hand, the intracorporeal circulation of the
blood by the e~tracorporeal system of this invention,
rarticularly by the pulsatile ump 14, is termed "forced
circulation." The forced circulation can be effected by
the pump 14 also during -the spontaneous circulation
because there is the need to assist in the bloo~ circula-
tion by the pump 14 when the spontaneous circulation isto be changed over to the forced circulation and vice
versa, whereb~- the change-over can be accomplished
smoothly. ~he AP signal from the blood pressure trans-
ducer 42 and the output signal from the electrocardio-
graph 43 are used as triggers for starting -the pump 14
during the spontaneous circulation. A trigger
generating circuit 46 produces a trigger pulse when the
AP signal waveform has reached a pea~. A trigger
generating circuit 47 produces a trigger pulse upon the
rise of R wave in the electrocardiogram. ''lith reference
to the AP waveform and electrocardiogram on the monitor
45, the operator can select one of the two trig~er
pulses by 2 selecting switch 48. ~he selected trigger
pulse is sent to an AND circuit 54 and to a timer 51.
For the forced circulation, the heart rate
7'~5~
enerator 44 produces t-rigger pulses of ~requency
set b~ its setting device 44a. The heart rate can be
set as desired by the setting device 44a. The trigger
pulse from the gener2tor 44 is fed to an AND circuit 55.
.~ switch 49 is used for setting the forced circulatlon.
When the forced circula-tion is set by the switch 49,
a high (H) level signal is given to an OR clrcuit 52.
It is likely that the heart of the patient
will stop temporarily without u~dergoin~ periodic
contraction when spontaneous circulation is changed to
forced circulation and vice versa. If the heart fails
to function for spontaneous circulation, the blood will
not circulate through the body, so that the circulation
mode must be changed over to forced circula-tion tempo-
rarily. The timer 51 is reset by the trigger pulse ofthe 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
circui-t 52. li~lhen 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 deli~ered
tothe AND circuit 55. Accordingly the trigger pulse
from the heart rate generator 44 passes through the
77~'i'
A~ ci-rcuit 55 and then th-rough an OR circuit 56 and ls
fed to a delay circuit 57. The r.1 level signal from
the OR clrcuit 52 is inverted by a ~OT circuit 53 to
a low (~) level signal, which is given to the A~D
5 circuit 54. Accordin~ly the AND circuit 54 inhibits
passage of the trigger p-ulse from the sv~itch 48. If
forced ci-~culation is not set, a~d the heart is repeat-
ing contraction with a period of ~7iu~in 2 seconcls, the
output of the OR circuit 52 is at Ilevel, 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 tl1e OR clrcuit 56.
The AND circuit 55 prevents passage of the tri~ger
15 pulse from the generator 44.
The delay circuit 57 delays the trigger pulse
fed thereto for a predetermined period of time. This
is of importance durin~ 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 two blood supplies
must be in synchronism. It is preferable that the
pump 14 supply the blood with a time delay after the
arterial blood is supplied by the heart. This is
25 termed "counter pulsation." The delay circuit 57
77~7
17
determines this delay time, rlhich is preferably so
determined as to be dependent on the period of systole
of the heart. ~he delay -time is obtained, for example~
by multiplying the previous pe-riod OI systole measured
or the mean value of preceding periods of systole by
a sui-table percentage. ~he measurement of the period
and the calculation of the dela-y~ time can o~ course be
performed automatically by a control circuit (not sho~m).
The percenta.ge is variable as desired.
The ~ridth of the delayed trigger pulse is
shaped to resemble the systole time of the heart by a
pulse width setting circuit 58. ~he control pulse
delivered from the circuit 58 is sent throu~h A~D
circuits 59 and 60 to the electromagnetic valve 31 to
open the valve. The valve 31, when opened, permi-ts
supply of compressed air to the pump 14 to contract
the pump 14 and supply the blood. Accordin~ly the ~idth
of the output pulse of the circuit 58 determines the
contraction time of the pump 14. Prefarably the
contraction time corres~onds to the s~-stole time of the
heart. ~he pulse wid-th is calculated 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 circuit 58 are determined preferably
ill accordance with the heart rate set by the ~enerator ~4.
The AP is used also for controlllng the start and
discontinuance of the operation of the pulsatile pump 14. The AP
signal from the blood pressure transducer 42 is applied to a peak
hold circuit 61 and a mean value calculating circuit 62. While
the heart ~f the patient is in operation and also while the pump
14 is in operation, the arterial blood is pulsating. Accordingly
the AP signal has a pulsatile waveform. The peak value of the
pulsatile AP signal, corresponding to the systolic pressure, is
held by and sent out from 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) for the systolic pressure is set on the upper limit
detecting circuit 63. When the systolic pressure input signal is
in excess of the upper limit value, the circuit 63 emits an H level
signal. A lower limit value (e.g. lO0 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 limit
~ -18-
~L~7~757
detectin~ circuit 63 is sent throu~h an OR circuit 67
to the se-t input terminal of a flip-flop 69. The detect~
ing si~nal ~rom the lower llmit detectinr~ circuit 64 is
sent through an OR circuit 68 to the reset input
terminal of the flip-flop 69. The flip flop 69 is
initially reset. 'i~hen the flip-flop 69 is reset, the
inverted output thereof is at H level, and at this time,
the cont-rol pulse of -the circuit 58 is sent throu~h the
~D ci-cuit 59 to the valve 31. When the flip-flop 69
is set, the inverted output the-reof is at ~ level, so
that the passa~e of the control pul~e is prevented.
Consequently the pump 14 is brour~ht out of operation
,rhen the hi~hest AP value exceeds t~le upper limit value,
~lhereas the pump 14 is initiated into operation when
the value drop~ below the lower limit value. The high-
es-t AP value is alwa~-s maintained a-t a level between
the upper limit value and the lo-ver limit value.
While the pump 14 is heid out of operation,
no peak appears in the AP si~nal. ~Ihen 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 peak appears in the AP sir~nal. The
mean value calculatin~ circuit 62 is provided to meet
such a situation. The peak hold circuit 61 has the
function of producin~ a no-peak si~nal when no pulse
_ 1 9
~'7~ 5'7
appears in the AP signal for a specified periocl of
til~e. The llo-pea.k signal i9 applied to the calculatln
circuit 62, whereupon the circuit 62 functions to
calculate and deliver the mean value of the ~P si~nal
everJ specified periocl of time. The mean value signal
is sent to upper and lower limit detectin~ circuits 65
and 66, on which upper and lower limit values are set
respectively. `~ihen the mean value signal e~ceeds the
upper limit value and when the si~nal drops below the
lower limit value, the circuits 65 and 66 each
produce an H level detectin_ signal, which is fed to
the flip-flop 69 in the same manner as above.
The detecting signal (H level) from the sensor
24 of the ~VP adjusting unit 20 has its ~aveform shaped
by a waveform shapin~ circuit 73 and then applied to
the set input terminal of a flip-flop 74. The ~P
si~nal from the blood pressure transducer 41 is fed to
a mean value calculating circuit 71, in which the mean
value thereof is calculated every specified 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 YP value drops below the lower limit value, the
circuit 72 emits an H level detecting signal, which is
given to the reset inpu-t terminal of the flip-flop 74.
~t~ 5~f
21
The flip-llop 74 is initiall~ reset. ~3/hile the flip-
lop 74 is reset, the inver-ted output si~nal thereof
is at H level. The ~ level signal opens the electro-
ma~netic valve 32. blhen the flip-flop 74 is set by
an overflow de-tecting signal fro~the sensor 24, the
flip-flop delivers an inverted output at I level to
close the valve 32. ~onsequently the pump 11 withdraws
an increased amount of blood as already described.
Thus, if the C~P exceeds the upper limit level (e.g.
10 to 20 mm Hg),for example, due to the con~estion of
blood in the body, the valve 32 closes, whereas if the
mean VP value drops below the lo-ier limit value (e.g.
several mm ~g), the valve 32 opens. The ~VP is there-
fore maintained at an approximately constant level at
all times.
The blood pressure transducer 41 and the
ci-rcuits 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 7 the electroma~netic valve
32 is held open at all times and is closed only while
the sensor is detecting an overflow, ~hereby the CVP
can be kept appro~ima-tely constant if the upper limit
for the CVP is set at a suitable level.
The detectin~ signals from the sensors 25 and
26 are fed to a valve control circuit 81. When the
~ ~7~
22
sensor 25 ~etects 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 the
sensor 26 gives an u~e-r limit level detec-ting si~nal.
~he ~ level signal is sent through a NOT circuit 82 to
-the A~1D circuit 60. Accordingly when the blood
remaining in the rese-rvoir is found to be in a small
a~ount, tne control pulse from the circuit 58 does not
pass- the AND circuit 60 9 and the motor 14 comes to a
stop. This prevents air from flo~ring 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 pu~p 14 need not alwa~s be stopped even if the
sensor 25 emits a detecting signal.
Figs. 4, 5 and 6 show other examples o~ CVP
adjusting units. With reference to Fig. 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 limi-t 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 com~unicating portion of the vertical tube 21.
~i~. 5 shows pairs of vertical tubes 21A, 22A;
~7t7~,t;,
23
21~, 22~; and 21C, 22C. The vertical tubes 21A to 21C
have communica-ting portions at different levels. The
other vert~ca,l tubes 22A to 22C are provided with
sensors 24A to 24~ for detectin~ an overflow of the
blood, res;oectively. A plurality of ~VP measurin~,
levels can be set on this CVP ad~us-ting unit. l~`/hen the
detecting signals from the sensors 24A -to 24~ are used
for controllin~ the openin~ de~ree of the valve 32, the
C~P is controllable in a finer more accurate manner.
With the arrangement of Fig. 5, the vertical tubes 22A,
22~ are provided with electroma~netic valves 38A, 38~,
respectively. These valves 38A, 38~ are open usually
and are closed when the corresponding sensors 24A, 24
have detected an overflow of blood. The valves are
opened again when the ~VP lowers to eliminate the over-
flow.
The overflow line 2 shown in ~ig. 6 is provided
only wi-th a vertical tube 21 the upper end of which is
open to the atmosphere. The line 2 has an electro-
magnetic valve 39 positioned closer to the pump 12. Thevertical tube 21 is fi~ed in place, while a sensor 24
is movable upward or downward along the tube 21 as
suppor-ted onthe tube. The valve 39 is closed usually
but is opened when the sensor 24 detects the blood
reachin~ the level of the sensor. Thus the blood is
~ ~ ~7'75~
24
aspirated throu~h the line 2 as is the case with an
overflow. ~he u~per limit level for the CVP is settable
as desired by varyin the level of the sensor 24.
Fi~. 7 shovJs another example of blood supply
line. ~etween a blood reservoir 7 and a pump 14, the
blood su~-ply line 4 is provided with a rotary pump 91
and an electromagnetic valve 93 positioned downstream
from the pu~p 91. In parallel with the rotary pump 91.
a return line is connected to tne line 4, with another
electromagnetic valve 92 provided on the return line.
For forced circulation, the p~p9 91, 14 operate, and
the valve 92 is closed with the valve 93 opened, whereby
the blood in the reservoir 7 is aspirated by the p~p
91 and intermittently forced out by the pump 14. If
the hi~hest AP value exceeds an upper li~it value, the
valve 92 is opened and the valve 93 is closed, so that
the blood circulates throu~h the return line and the
pump 91 without flovrin~ into the pump 14. At this
time, the pu~p 14 may be in or out of operation~
When the hi~hest 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 "~AP") can
~'7~ 5
be measured. Accordin21y the blood circulation can be
so controlled that -the left side s~y-stem of the heart
and the risht side s~-stem of the heart wlll function
in sood balance. The ~AP reflects the function of the
left heart system, vrhile the ~VP reflects the function
ol the right heart system. The range of desire~ values
of ~AP (e.g. 8 to 15 mm Hg) is p-recLetermined, and the
CVP is so adjusted that the IAP ~lill be maintained in
this range at all times.
With reference to Fig. 8, the TAp is detected
by a pressure transducer 101. The means IAP value is
ca~culated at a specified time interval by a mean value
calculating circuit 102. The u~per limit value (e.g.
15 mm ~g) of the desired range of ~AP values is set on
an upper limit detecting circuit 103. Vlhen the output
from the circuit 102 e~ceeds the upper limit value, tL~le
circuit 103 emits an up~er limit detecting signal. The
lower limit value (e.g. 8 mm Hg) of the desired ~AP
range is se-t on a lower limit detecting circuit 104.
When -the ~AP drops belo~v the lovler limit value, the
circuit 104 emits a lower limit detectin~ signal. ~evel
control means 105 raises or lowers the upper limit level
of CVP in the CVP adjusting unit 20. With the unit 20
shown in ~i~. 1, the vertical tubes 21, 22 and the
support member 23 are raised or lowered. With the
~77~'~
26
arran~ement sho-im in PiT. 6, the blood sensor 24 is
raised or lowered. When the detected IAP value is
above the upper limit settin~, the upper limit level
for CVP is slowly lowered until the LqP lowers below
the u~per limit value. Conversely if the detected ~AP
value is below the lower limit, the upper limit level
for the CVP is slowly raised. The rise of the CVP u~er
limit level is stopped when the IAP exceeds the lower
limit value. In this wa~-, the IAP is maintained in
the desired ran~e at all times.
