U.S. patent number 3,877,843 [Application Number 05/361,960] was granted by the patent office on 1975-04-15 for pulsatile pumping system.
This patent grant is currently assigned to Baxter Laboratories, Inc.. Invention is credited to Halbert Fischel.
United States Patent |
3,877,843 |
Fischel |
April 15, 1975 |
Pulsatile pumping system
Abstract
A portable pulsatile pumping system simulates the pumping
mechanism of a human heart in pumping fluid for such applications
as organ perfusion systems. The pumping system includes a regulated
source of pressurized gas, a pulsatile pump having an aorta chamber
providing a sustained minimum diastolic pressure and a ventricle
chamber providing a higher systolic pressure during a selectively
variable part (1 to 99 percent) of each cyclic pumping action, the
periodicity of which may be varied from 5 to 150 cycles per minute.
The gas source is connected to the pump by a first adjustable
pressure regulator to maintain the chosen diastolic pressure in the
aorta chamber. The ventricle chamber is alternately coupled to gas
pressure taken through a second pressure regulator and vented by a
solenoid mechanism operated by a digital electronic timing control
circuit. The digital electronic control system employs digital
counters and selector switches to generate square wave pulses of
varying duration and periodicity in a manner which provides both
conservation of electrical battery energy and high reliability. At
the same time, an optimum pumping system is achieved because the
elasticity of the gas and connecting tubing are employed to smooth
the sharp signal transitions.
Inventors: |
Fischel; Halbert (Sherman Oaks,
CA) |
Assignee: |
Baxter Laboratories, Inc.
(Morton Grove, IL)
|
Family
ID: |
23424111 |
Appl.
No.: |
05/361,960 |
Filed: |
May 21, 1973 |
Current U.S.
Class: |
417/394;
128/DIG.3; 91/39; 600/17; 327/113 |
Current CPC
Class: |
F04B
49/06 (20130101); A01N 1/0289 (20130101); A61M
60/50 (20210101); A01N 1/0247 (20130101); Y10S
128/03 (20130101); A61M 60/562 (20210101); A61M
60/268 (20210101); A61M 60/113 (20210101) |
Current International
Class: |
A01N
1/02 (20060101); A61M 1/10 (20060101); F04B
49/06 (20060101); A61b 019/00 (); F15b 021/02 ();
F04b 043/00 () |
Field of
Search: |
;91/37,39,459 ;195/127
;417/375,394,395,396,397,398,399,400,401,402,403,404
;128/1D,DIG.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Assistant Examiner: Gluck; Richard E.
Attorney, Agent or Firm: Ellis; Garrettson
Claims
What is claimed is:
1. A system for providing a selectively controllable pulsatile flow
of a perfusate to simulate cardiac action comprising: a pulsatile
perfusate pump which comprises flexible chamber means, said means
being collapsible in response to applied fluid pressure, to pump
perfusate in said chamber means through a flow line in pulsatile
manner;
at least one fluid pressure means;
adjustable systolic pressure regulator means coupled to said fluid
pressure means;
first conduit means including control signal responsive valving
means coupling said systolic pressure regulator means to said
ventricle chamber means; and
electronic control means including adjustable means for generating
square wave control signals of adjustable duration and repetition
rate, the square waves having sharp rise and fall times, wherein
said valving means comprises a two output valve having a venting
output and an output communicating with said perfusate pump,
wherein said fluid pressure means comprises a pressure storage
vessel, and wherein said electronic control means comprises counter
means adjustable to provide valving means controlling outputs at
selected counts, said counter means being adapted to count said
square wave control signals.
2. The invention as set forth in claim 1 above, wherein said first
and second conduit means comprise small diameter resilient tubing,
and wherein the applied fluid under pressure is air.
3. A combination electronic pneumatic pump control system for
gently controlling a pulsatile pump maintaining a first output
pressure and producing a periodically occurring systolic output
pressure greater than the first pressure in response to a
periodically occurring fluid drive pressure comprising:
a selectively venting pressure control valve having an input
connectable to a drive fluid pressure source under control of a
transducer;
a conduit connected to the outlet of the pressure control valve to
a fluid operated pulsatile pump for providing operating fluid to
said pump, said conduit restricting the flow of drive fluid
therethrough;
a transducer connected to control said pressure control valve to
selectively connect the outlet to said pressure source in response
to first and second states respectively of an electronic digital
control signal having sharp transitions between states; and
an electronic digital control circuit providing an electronic
digital control signal to the transducer, said control circuit
including a recycling counter, means responsive to the counter for
switching the electronic digital control signal to a first state
when the counter reaches a first selected count, and means for
switching the electronic digital control signal to a second state
when the counter reaches a second selected count, each state being
present during a selected variable proportion of each control
signal.
4. The pump control system as set forth in claim 3 above, wherein
the conduit includes at least one elastically expansible portion
which absorbs energy as it expands in response to a pressurized
drive fluid therein.
5. The pump control system as set forth in claim 4 above, wherein
the drive fluid is an expandable gas.
6. The pump control system as set forth in claim 5 above, wherein
the drive fluid is compressed air.
7. The pump control system as set forth in claim 3 above, wherein
at least one of said first and second counts is selectively
variable under operator control.
8. The pump control system as set forth in claim 5 above, wherein
the electronic digital control circuit includes an oscillator
generating a clock signal at a selectively variable frequency; a
recycling counter connected to count cycles of the clock signal;
means responsive to the counter for generating first and second
intermediate control signals in response to first and second counts
of the counter respectively, said control signal generating means
including means for selectively varying the count at which at least
the first intermediate control signal is generated; and means
connected to switch the electronic digital control signal to the
first and second states in response to the first and second
intermediate control signals respectively.
9. A system for providing a selectively controllable pulsatile flow
of a perfusate to simulate cardiac action, the flow having
selectable diastolic and systolic intervals and pressures
comprising:
a pulsatile perfusate pump having at least a pair of pump chamber
means responsive to applied fluid pressures;
means providing diastolic and systolic fluid pressures;
conduit means providing substantial impedance to fluid flow and
coupling each of said diastolic and systolic pressure means to a
different chamber of said perfusate pump;
signal responsive valving means coupled into the conduit means
coupling the systolic pressure means to the perfusate pump; and
electronic control signal generating means coupled to said valving
means and including means for generating a systole control signal
of controllable duration and repetition rates, to provide control
signals to said signal responsive valving means, said systole
control signal means comprising an electronic digital control
circuit which includes an oscillator for generating a clock signal
at a selectively variable frequencies; a recycling counter
connected to count cycles of the clock signal; means responsive
through the counter for generating first and second intermediate
control signals in response to the first and second counts of the
counter respectively, said control signal generating means
including means for selectively varying the count in which at least
the first intermediate control signal is generated; and
means for altering the signal responsive valving means in response
to the first and second intermediate control signals
respectively.
10. For use in an organ perfusion system circulating a perfusate
through an organ, a pulsatile pumping system comprising:
a pump connected to receive perfusate in an inlet and deliver
perfusate in an outlet, said pump including first and second
control fluid inlets and providing a first perfusate pressure at
the outlet in response to a high control fluid pressure at the
first control fluid inlet and a second perfusate pressure at the
outlet in response to a low control fluid pressure at a second
control fluid inlet in the absence of the high control fluid
pressure at the first control fluid inlet;
means for connecting the first control fluid inlet to a high
pressure control fluid source in response to a first electrical
signal condition and disconnecting the first control fluid inlet in
response to a second electrical signal condition;
a timing control circuit coupled to said means for connecting for
providing a bistate electrical signal of selectable periodicity
having alternate first and second electrical signal conditions, the
control circuit including means responsive to operator control for
selecting the relative durations of the first and second electrical
signal conditions during each period, in which said timing control
circuit comprises an electronic digital control circuit including a
recycling counter, means responsive to the counter for assuming the
first electrical signal condition when the counter reaches a first
selected count, and means responsive to the counter for assuming
the second electronic signal condition when the counter reaches a
second selected count.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a system providing gentle, pulsatile
pumping for life sustaining fluids, and more particularly to
pulsatile pumping systems for organ perfusion systems whose cyclic
characteristics may be varied within wide ranges.
2. History of the Prior Art
There are many biomedical systems in which it is desirable to pump
life sustaining fluids in a pulsatile manner closely simulating
cardiac action. One such application is in an organ perfusion
system for preserving an organ such as a kidney from the time it is
removed from a donor until it is feasible to transplant it in a
recipient.
An organ perfusion system typically recirculates a perfusate
containing oxygen and nutrients under control of a pump. Perfusate
is drawn from a pool in which the kidney rests, passed through an
oxygenator which adds oxygen and removes carbon dioxide, adjusted
in temperature, typically by cooling to 5.degree.-10.degree. C.,
and returned to the kidney. Incoming perfusate is connected to the
renal artery of the kidney and passes through the kidney to the
pool of perfusate in which the kidney rests, from which pool it is
again recirculated. While the reasons are not fully understood at
present, a pulsatile pumping action is preferred because it appears
to aid the distribution of perfusate through an organ and the
performance of life sustaining functions.
Because of the difficulty of getting donors and recipients at the
same place at the same time it is desirable that an organ perfusion
system be portable and be able to maintain the organ viable, for at
least several days. At the same time it must provide smooth, gentle
handling of the perfusate under controlled conditions so as not to
shock the life sustaining fluid. An advantageous pulsatile pump
that closely simulates cardiac pumping action when properly
energized is described in U.S. Pat. No. 3,639,084 and incorporates
distensible ventricle and aorta chambers connected in series by
one-way valves. An atrium chamber collects perfusate under gravity
flow and the adjacent ventricle chamber responds to applied
periodic systolic pressures to pump perfusate into the aorta
chamber which is under constant bias to provide a sustained minimum
diastolic pressure. As described in the referenced patent, the
systolic and diastolic pressures may be supplied by a regulated
source of pressurized air and a fluid logic control circuit may
control the periodic repetition of systolic pressure in the
ventricle chamber. However, the fluid timing and logic control
requires large amounts of compressed air, which militates against
portability, and such controls do not adequately permit
adjustability over wide operation ranges.
SUMMARY OF THE INVENTION
A pulsatile pumping system for life sustaining fluids in accordance
with the invention is portable and economical but yet provides the
high reliability, versatility and gentle handling needed for organ
perfusion. A pulsatile pump is driven by a highly portable
pressurized gas source under control of an accurate, low energy
digital electronic circuit. The digital circuit provides accurate
control of the pumping action over a wide range of pumping rates
and pressure proportions while the elasticity of the gas and
connecting tubing smooth sharp transitions resulting from digital
control.
A particular example of the system includes a pump of the
distensible chamber type having ventricle and aorta chambers
responsive to applied fluid pressures, a source of pressurized
fluid providing driving energy for the pump, a diastolic pressure
regulator valve coupling the pressurized fluid to the aorta chamber
to maintain a constant diastolic pressure therein, a systolic
pressure regulator valve coupling the pressurized fluid to the
ventricle chamber to provide alternate atmospheric and systolic
pressures therein under control of an electronic control circuit,
and an electronic digital control circuit connected to control the
systolic pressure regulator valve. The control circuit includes a
transducer which is responsive to square wave signals and a digital
circuit providing square wave signals at a selected variable
frequency with the systolic portion of each cycle having a
selectively variable proportion. The elasticity of the driving
fluid and connecting conduits smooth the sharp actuating signal
transitions provided by the digital electronic control to attain a
gentle but precise pumping action.
The control circuit includes a variable frequency square wave clock
signal generator and two series connected stages of a binary coded
decimal (BCD) counter which recycles after each 100 cycles of the
clock signal. BCD to decimal decoders are connected to provide a
decimal output indicating the state of the units and tens portions
of the counter respectively. A pair of two rotor multiple contact
rotary switches is connected to the decimal outputs of each of the
units and tens decoders so that the rotatable wiper arms are
energized when the counters have counted to the decimal outputs
which are connected to the contacts at which the rotors are set. A
flip flop providing the systolic pressure control signal is
connected to reset when the counters recycle and set when the
advancing count causes the rotors of both the units and tens
switches to become simultaneously activated. As the flip flop sets
and resets it provides a square wave pump control signal
demarcating alternate diastolic and systolic time intervals with
adjustably selectable proportions and the frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the invention may be had from a
consideration of the following detailed description taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of an organ perfusion system
utilizing a pulsatile pumping system in accordance with the
invention;
FIG. 2 is a partly block diagram and partly schematic
representation of a digital electronic control circuit controlling
the operation of the pulsatile pumping system shown in FIG. 1;
FIG. 3 is a schematic diagram representation of a variable
frequency square wave clock signal generator used in the electronic
control circuit shown in FIG. 2; and
FIG. 4 is a schematic diagram representation of a square wave clock
signal frequency indicator used in the electronic control circuit
shown in FIG. 2 .
DETAILED DESCRIPTION
Referring to FIG. 1, there is shown a portable organ perfusion
system 10 for preserving living organs over an extended period of
time. The system 10 includes a container or organ chamber 12, in
which an organ is to be maintained, a perfusate conditioning system
14 and a pulsatile pumping system 16 which controls the
recirculation of life substaining perfusate from a pool in the
container 12, through the conditioning system 14 and through an
organ 18 in the container 12 back to the pool in the container
12.
Perfusate moves under gravity flow from the pool in the container
12 through a conduit 20 and T section 22 to an oxygenator 24 of
conventional construction. The T section 22 contains a thermistor
probe 26 which is in thermal communication with perfusate passing
therethrough and generates an electrical temperature signal
indicative of perfusate temperature on a conductor 28. Perfusate
enters the oxygenator at an inlet 30 and passes through the
oxygenator 24 under gravity flow to an outlet 32. The oxygenator 24
has an oxygen inlet 34 connected by a conduit 36 to a pressure
regulating valve 38 which is in turn connected to a source of
pressurized oxygen 40. The pressure regulator valve 38 maintains
the oxygen pressure within the oxygenator 24 at a proper level for
dissolving a desired amount of oxygen in the perfusate as it passes
through the oxygenator 24. An outlet 42 is connected to a conduit
44 to vent carbon dioxide which is removed from the perfusate as it
passes through the oxygenator. Thus, as perfusate reaches the
outlet 32 it has been resupplied with oxygen and unwanted carbon
dioxide has been removed. An access T coupling 46 is connected by
conduits 48 and 50 between the outlet 32 of the oxygenator 24 and
an inlet 52 of a pulsatile pump 54 within the pumping system
16.
The pump 54, which is of the distensible chamber type described in
U.S. Pat. No. 3,639,084, delivers the perfusate at an outlet 56
from which it passes through a conduit 58 to a heat exchanger 60
having perfusate inlet 62 connected to the conduit 58 and a
perfusate outlet 64. The heat exchanger 60 has an inlet 66 and
outlet 68 through which a heat carrying fluid passes to provide
thermal compensation for the perfusate to tend to maintain it at a
selected constant temperature. A temperature control system 70
receives the heat carrying fluid through a conduit 72 which is
connected to the outlet 68 and delivers heat carrying fluid through
a conduit 74 to the inlet 66.
The temperature control system 70 is connected to operate in
response to the temperature control signal on conductor 28 to
maintain the perfusate at a desired temperature. The temperature
control system removes heat from the heat carrying fluid as it is
recirculated through the heat exchanger 60 in a typical situation
where a perfusate temperature of 5.degree.-10.degree. C. is
desired. As the heat carrying fluid is circulated through the heat
exchanger 60 it is in thermal communication with the perfusate,
thereby tending to maintain perfusate leaving the heat exchanger at
outlet 64 at the same temperature as heat carrying fluid entering
the heat exchanger through inlet 66. In other arrangements it may
be desirable to maintain the perfusate at or near normal body
temperature control and in this case it may be necessary for the
temperature control system 70 to add heat to the heat carrying
fluid as it is recirculated through the heat exchanger 60 in order
to maintain the perfusate at the desired temperature.
As perfusate leaves the outlet 64 of heat exchanger 60 it flows
through conduit 76 to access T coupling 78 and then through conduit
80 back to the container 12 where the conduit 80 is connected to an
organ 18 which is being preserved. For instance in the case of a
kidney, the conduit 80 would be connected to the renal artery
thereof. The access T couplings 46 and 78 permit perfusate to be
periodically drawn off by hypodermic needles for laboratory
analysis. Similarly, substances can be added to the perfusate by
injection through the access T couplings 48, 78.
In addition to the pump 54, the pumping system 16 includes a source
of pressurized driving fluid 82 in the form of a high pressure air
bottle which is easily and efficiently coupled to the pump 54, a
pressure regulating and conduit system connecting the driving fluid
with the pump 54, a solenoid transducer 84 controlling a systolic
pressure valve in the pressure regulating and conduit system and a
digital electronic control system 86 providing a periodic square
wave pulse control signal for actuating solenoid 84. The source of
pressurized fluid may alternatively be provided by a battery driven
electric motor driving a compressor. The pulse control signal has a
selectively variable frequency with systolic and diastolic time
intervals of adjustably selectable duration within each cycle. The
pump 54 is designed to provide a gentle pulsatile pumping action
closely resembling the pumping action of a human heart which
alternates a relatively low diastolic pressure with a relatively
high systolic pressure during each pumping cycle. The pump 54
contains three chambers which are connected in series through
one-way valves 88 and 94 which permit perfusate to flow only in a
forward direction through the pump 54. An atrium chamber 92
collects perfusate as it passes under gravity flow through the
inlet 52. A ventricle chamber is divided by a flexible membrane 96
into two portions. An interior or perfusate portion 98 of the
ventricle chamber is interior to the membrane 96 and receives
perfusate through one-way valve 88 from the atrium 92 under gravity
flow when the external or driving fluid portion 100 of the
ventricle is at atmospheric pressure. The external portion 100 of
the ventricle chamber is connected to the pressure regulating
system through a small flexible, elastically expansible energy
absorbing conduit 102 of a resilient material such as silicone
rubber having an inside diameter of about 1/4 inch.
The pressure regulating system includes a high pressure regulating
valve 110 having an inlet orifice 112 connected to the high
pressure source 82 and an outlet orifice 114. The pressure
regulating valve 110 maintains a constant pressure of about 20 psi
at the outlet 114. A Y connection 116 has an inlet connected to the
regulated pressure outlet 114 and separate outlets 120, 122. A
fourway diastolic pressure regulator valve 124 has an inlet orifice
126 connected to outlet 120, an outlet orifice 128 and a vent
orifice 130. The diastolic pressure regulator valve 124 provides a
selectable constant output pressure of 0-500 millimeters of mercury
at the outlet 128. This diastolic pressure is set at a desired
level by varying the position of a control knob 132 which is
typically set to provide a diastolic pressure of about 80
millimeters of mercury. The valve 124 can either supply the outlet
128 with driving fluid from source 82 or vent driving fluid from
the outlet 128 to the atmosphere through vent 130 as necessary to
maintain the diastolic pressure constant.
A systolic pressure regulator 136 similar to diastolic pressure
regulator 124 has an inlet 137 connected to the outlet 122 of Y
connector 116, an outlet 138, and a vent 139. A four-way valve 140
has an inlet orifice 141 coupled to outlet 138, an outlet orifice
142, an atmospheric vent orifice 143 and is mechanically coupled to
solenoid 84 to connect the outlet 142 to atmospheric pressure
through vent 143 when solenoid 84 is inactive and to provide a
desired systolic pressure at outlet 142 when solenoid 84 is
activated. A desired systolic pressure between 0 and 500
millimeters of mercury may be selected by rotating a control knob
144 on control valve 136 to a desired position. The control knob
144 is typically set to provide a systolic pressure of 240
millimeters of mercury. The conduit 102 is connected to the
regulating system at the outlet 142 of solenoid actuated valve
140.
An optional aorta chamber 148 of pump 54 provides a low diastolic
pressure which may be greater than atmospheric pressure and has a
construction very similar to that of the ventricle chamber. The
aorta chamber 148 has a flexible membrane or diaphragm 150 which
divides an interior portion of the chamber 152 from an exterior
portion 154. The exterior portion 154 is connected by a conduit 156
to the outlet 128 of diastolic pressure regulator valve 124 which
causes the predetermined diastolic pressure to be constantly
maintained in the external portion 154 of aorta chamber 148.
During a diastolic portion of a pumping cycle, the solenoid 84 is
inactive and the external portion 100 of ventricle chamber is
vented to atmospheric pressure. This allows membrane 96 to expand
as perfusate flows by reason of a gravity head through one-way
valves 88 from the atrium 92 into the interior portion 98 of
ventricle chamber. Then, as solenoid 84 receives an activating
signal from control circuits 86, systolic control valve 140 is
driven to a systolic pressure condition to provide the systolic
pressure through outlet 142 and conduit 102 to the exterior 100 of
ventricle chamber. This relatively high systolic pressure drives
perfusate from the interior portion 98 of ventricle chamber through
one-way valve 94 to the aorta chamber 148 which is somewhat smaller
than ventricle chamber. As perfusate is forced through one-way
valve 94 during this systolic portion of the cycle, the flexible
membrane 96 collapses, the interior portion 98 decreases in volume,
and the exterior portion 100 increases in volume. At the beginning
of a systole portion of a pumping cycle, the pump 54 continues to
provide perfusate at the diastole pressure. However, the aorta
membrane 150 rapidly expands to maximum capacity, permitting the
systolic pressure to then be passed through the aorta chamber to
the kidney 18. The cycle is then repeated as the solenoid 84 is
deactivated, causing systolic control valve 140 to again vent the
exterior portion 100 of ventricle chamber to the atmosphere.
After the systolic portion of a pumping cycle is terminated by
control circuit 86 the membrane 150 begins to collapse under the
constant pressure in the external portion 154 of the aorta chamber
148 to force perfusate out through the outlet 56 at the constant,
sustained, minimum diastolic pressure. Before the membrane 150 is
completely collapsed a new systolic portion of a pumping cycle must
be commenced to force more fluid into the aorta chamber. In this
way the pulsatile pump 54 provides alternating diastolic and
systolic pressures at the outlet 56 with a pumping characteristic
very closely following that of a human heart.
The small internal diameter of conduit 102 and the elastic energy
absorbing properties of the driving fluid and conduit 102 combine
to provide an energy absorbing fluid impedance which acts as a
hydraulic filter to smooth sharp pressure transitions in the
ventricle chamber. Some life sustaining fluids such as whole blood
are easily damaged by shock and must therefore be treated extremely
smoothly and gently. This hydraulic impedance or filtering
characteristic permits the hydraulic control system to be
controlled by a square wave pulse signal having sharp transitions
(for example 5 millisecond rise -- 30 millisecond decay) without
damaging the life sustaining fluid. By the time the digital pulse
control signals reach the external portion 100 of the ventricle
chamber sharp transitions have been filtered out. Thus, the
pulsatile pump 54 is able to handle a life sustaining fluid gently
and without shock, whether it be whole blood, perfusate or some
other fluid, even though control is provided by a digital
electronic signal having sharp transitions.
A second organ perfusion system represented by a hollow rectangle
162 and labeled Perfusion System No. 2 is connected to receive
perfusate at an inlet 164 through a conduit 166 from the pool in
container 12 and provide perfusate through outlet 168 and conduit
170 to a conduit 172 which connects to a second organ to be
preserved within the container 12. Organ Perfusion System No. 2
shares the container 12 and certain components in the control
circuit 82 with Perfusion System No. 1 and may be assumed to be
substantially identical to Perfusion System No. 1 even though it is
not described in detail.
The electronic digital control circuit 86 includes a variable
frequency square wave generator 200 which generates a digital
square wave clock signal at a frequency selected by an operator, a
frequency indicator circuit 202 which indicates to an operator the
frequency of the square wave clock signal, a proportioning control
circuit 204, a gated flip flop 206, a power amplifier 208 and a
solenoid coil 210 which controls the activation of solenoid 84
(FIG. 1).
The proportion control circuit 204 includes a century counter
having a BCD units counter 212, a BCD tens counter 214 connected to
count cycles of the counter 212, a BCD to decimal converter 216
responsive to the outputs from the unit counter 212 and a BCD to
decimal converter 218 responsive to outputs from the BCD tens
counter 214. The BCD counters 212, 214 may be implemented with MC
7490P integrated circuits manufactured by Motorola and the BCD to
decimal converters 216, 218 may be implemented with MC 7442P
integrated circuits, also manufactured by Motorola. The decoded
decimal units and decimal tens outputs of the century counter
indicate the successive counts of the century counter as it counts
clock pulses from 0 to 99 and then recycles back to 0 at count 100.
For instance when the counter reaches the count of 55 the number 5
outputs of both the units converter 216 and tens converter 218 will
have a high voltage thereat and each of the other decoded decimal
outputs will have a low or ground potential thereat. The counter
212 and converter 216 together with the counter 214 and converter
218 form first and second decade counting systems providing
discrete decimal outputs indicative of instantaneous counts
therein.
Four switches are provided to permit operator control of the
proportion of each pumping cycle during which systolic pressure is
desired, two for system No. 1 and two for system No. 2. Each switch
contains two completely insulated portions designated part A and
part B having mechanically coupled rotors which are simultaneously
and synchronously positioned by a single control knob. Switch U1 is
a ten position rotary switch in which an A portion has the fixed
contacts thereof connected to the ten decimal outputs of the units
converter 216 in sequence. Similarly, switch T1 is a 11 position
rotary switch having ten of its 11 contacts connected to the ten
decimal outputs of tens converter 218 in sequence. The eleventh
contact is not connected. The two switches U2 and T2 of the second
perfusion system are connected in similar manner with the ten A
contacts of switch U2 connected to the ten decimal outputs of units
converter 216 and ten of the eleven A contacts of switch T2
connected to the ten decimal outputs of tens converter 218 with the
eleventh A contact left open. The BCD units counter 212 receives
the variable frequency clock signal as an input on conductor 220
and BCD tens counter 214 receives its counting input from decimal
output zero from units converter 216 on conductor 222. The
integrated circuits 212, 214, 216 and 218 may otherwise be
connected, biased and compensated in a conventional manner. An
isolator 224 which may be implemented with an MC 836P integrated
circuit manufactured by Motorola is connected to receive inputs
from the decimal zero output of tens converter 218, the decimal
zero output of units converter 216, the rotary wiper contact 226 of
switch T1A, the rotary wiper contact 227 of switch U1A, the rotary
wiper contact 228 of switch T2A and the rotary wiper contact 229 of
switch U2A and provide outputs designated OT, OU, T1AR, U1AR, T2,
AR, and U2AR respectively in response thereto.
These six signals are used by systolic pulse generating circuits
for both systems No. 1 and No. 2 to generate the systolic pulse
signals which actually control the activation of solenoid coil 110.
Since this portion of the system is identical for both system No. 1
and system No. 2, the systolic pulse generating circuits for system
No. 2 is indicated merely by a hollow rectangle 132 and it will be
understood that the same description applies as given hereafter for
system No. 1.
As illustrated with respect to system No. 1, the wiper arm signals
TLAR and ULAR for the digit and for the decimal and unit switches
respectively are received by an AND gate 234 controlling the J
input to a JK flip flop 236 within an integrated circuit gated flip
flop 216. The TLAR and ULAR signals operate in combination with the
clock signal to activate AND gate 234 at the selected variable
count, causing AND gate 234 to generate an intermediate control
signal which activates the J input to flip flop 236. An AND gate
238 generates an intermediate control signal which activates the K
input to flip flop 236 in response to the OT, OU and clock signals
which occur as the century counter resets. The AND gates 234 and
238 are connected to be enabled by the clock signal from the square
wave generator 200. An inverting preset input to flip flop 236 is
connected through a 10 K resistor 240 to a 5 volt source. It is
also connected to the number 10 contact of the B portion of switch
TL. The number 10 contact of the A portion of switch TL is not
implemented. A movable rotor 244 of switch TLB is connected to
ground. An inverting clear input to flip flop 236 is connected
through a 10 K resistor 242 to a 5 volt source and to the number 0
contact of the B portion of the switch UL. The wiper arm 245 of
switch ULB is connected to the number 0 fixed contact of switch
TLB. Thus, whenever both of the system No. 1 proportioning system
switches are set to zero, flip flop 236 is constrained to the clear
state. Similarly, whenever switch TLB is set to the number 10
position, flip flop 236 is constrained to remain in the one or true
state. The Q output of flip flop 236 provides the square wave
systolic pulse control signal on conductor 250 which drives the
coil 210 through power switching amplifier 208.
Conductor 250 is connected through a 3.3 K resistor 252 to the base
of an npn transistor 254. The collector of transistor 254 is
connected through a 220 ohm resistor 256 to a +5 volt source and
the emitter of transistor 254 is connected through a 1 K resistor
258 to ground and also to the base input of an npn transistor 260.
The emitter of transistor 260 is connected to ground and the
collector is connected both to the anode of a diode 262 and to a
negative terminal of solenoid coil 210 in solenoid 84. The solenoid
coil 210 and diode 262 are connected in parallel with the positive
terminal of coil 210 being connected to a +12 volt source and the
cathode of diode 262 connected to the same +12 volt source.
The power switching amplifier 208 responds to a systolic pulse
control signal on conductor 250 by activating the coil 210 when the
control signal is high or true and inactivating the coil 210 when
the control signal is at ground potential or false. Whenever the
systolic pulse control signal is true, transistor 254 is turned on
permitting current to flow through the collector and emitter
thereof to in turn cause transistor 260 to be turned on. As
transistor 260 is turned on activating current is permitted to flow
from the +12 volt source through coil 210 to the collector of
transistor 260 and then out through the emitter of transistor 260
to ground. This activation of coil 210 causes solenoid 84 to switch
four-way pressure regulator valve 136 to the systolic pressure
state wherein systolic pressure is applied to external cavity 100.
As the systolic pulse control signal returns to ground potential,
transistors 254 and 260 are switched off and the continued flow of
current through the coil 210 is blocked. As coil 210 is deactivated
solenoid 84 causes pressure regulator valve 136 to return to a
state wherein atmospheric pressure is communicated to external
chamber portion 100. Energy which may be stored by solenoid coil
210 at the time transistor 260 is switched off may be dissipated
through diode 262.
The variable frequency square wave generator 200 is illustrated in
greater detail in FIG. 3. The generator 200 includes a type 2N2840
variable frequency oscillator 260 having a B2 terminal connected
through a 1 K resistor 262 to a +5 volt source and a BL terminal
connected through a 68 ohm resistor 264 to ground. The control
terminal E of oscillator 260 is connected through a 15 .mu. farad
capacitor 266 to ground and also through a frequency control
circuit 268 to the +5 volt source. The frequency control circuit
268 includes a 20 K potentiometer 270 having one terminal and the
wiper contact connected to the +5 volt source and the other
terminal connected to a 16.5 K resistor 272. The other terminal of
resistor 272 is connected to one terminal of an 8.2 megohm resistor
274 and one terminal of a 1 megohm potentiometer 276 having a
logarithmically varying resistance. The opposite terminal of
resistor 274, the wiper arm of potentiometer 276, and the opposite
terminal of potentiometer 276 are connected to the gate or control
input E to oscillator 260. The output from the oscillator 260 is
taken from a BL terminal which is connected through a 1 K resistor
280 to the base of an npn amplifying transistor 282. Transistor 282
has its emitter connected to ground and its collector connected
through a 3.3 K resistor 284 to a +5 volt potential. The collector
of transistor 282 is connected to the base of a second amplifying
transistor 286 having its emitter connected to ground and its
collector connected through a 1 K resistor 288 to the +5 volt
potential. The square wave clock signal is provided on conductor
220 which is connected to the collector of amplifying transistor
286.
The variable square wave generator 200 provides a square wave clock
signal at a frequency variable between 8.33 and 250 hertz in
accordance with the setting of potentiometer 276. This frequency
range corresponds to a frequency range of 500 to 15,000 cycles per
minute which is divided by 100 by the century counter 204 to
provide a frequency range of 5 to 150 pulses per minute for the
systolic pulse control signal on conductor 250.
The frequency indicator circuit 202 is illustrated in greater
detail in FIG. 4. The frequency indicator 202 includes a one shot
300 which receives the clock signal from square wave generator 200
on conductor 220 and generates a positive output for a selected
time interval in response to each positive going transition of the
clock input. The one shot 300 may be a type MC 8601P integrated
circuit manufactured by Motorola and has a 44.2 K resistor 302 and
a 0.22 .mu. farad capacitor 304 connected in a conventional manner
to control the time interval of the output. The output is taken
from the key terminal and connected through a 2.21 K resistor 306
and a 2 K trim pot 308 to a positive terminal of a milliameter 310
which has its negative terminal connected to ground. A 90 .mu.
farad filter capacitor 312 is connected in shunt across the
terminals of milliameter 310 to smooth changes in voltage across
the terminals of the meter 310. The resistor 306 and potentiometer
308 operate in conjunction with a fixed voltage at the Q output of
one shot 300 to provide in effect a constant current source which
provides meter 310 with a fixed amount of charge for each fixed
firing interval of one shot 300. The total charge per unit of time
reaching milliameter 310 is thus directly proportional to the
frequency at which the one shot is fired under control of clock
signal on conductor 220. This charge must pass through milliameter
310 in the form of a current which drives the pointer to a
rotational position directly proportional to the frequency of the
clock signal. Milliameter 310 may be calibrated to indicate the
frequency of the systolic pulse control signal directly.
The electronic digital control circuit 86 provides precise, highly
reliable, low cost control of the pulsatile pumping system with the
consumption of very little electrical power. A highly portable,
conventional 12 volt battery (not shown) easily provides the
required source of electrical energy. A conventional voltage
regulator such as a LM309K manufactured by National Semiconductor
may be connected to the 12 volt battery to provide the +5 voltage
source required at many points in the control circuit 86. While an
easily portable battery provides the electrical power, an easily
portable bottle of pressurized air may be used to provide the
pneumatic power. Since the pressurized air driving fluid is used
only to drive the pulsatile pump 54, much less driving fluid is
consumed by the perfusion system 10 than would be required if the
driving fluid were also used to energize a pneumatic timing control
system. Since a 25-pound bottle of pressurized air will operate the
perfusion system 10 for 8-12 hours, the complete perfusion system
including energy sources is relatively light in weight and highly
portable. This arrangement makes optimum use of both electrical and
pneumatic elements and energy sources to provide an economical,
highly reliable, portable perfusion system 10 which can be used to
preserve an organ for several days while transporting it from one
place to another.
The electrical control system permits the systolic portion of each
cycle of the pulsatile pump 54 to be varied under automatic control
between 1 and 99 percent, fixed at 0 percent, fixed at 100 percent
or completely controlled by hand. For instance, by setting the
units and tens control switches to number 55, diastolic pressure
will be provided during the first 55 percent of each pumping cycle
and systolic pressure will be provided during the last 45 percent
of each pumping cycle. As the century counter recycles the 0
outputs of both the units and tens BCD to decimal converters 216,
218 will go true causing the OT and OU signals to go true to
activate the K input to flip flop 236. The K input causes flip flop
236 to reset and produce a ground potential output signal which
turns off power amplifier 208 to deactivate solenoid coil 210 and
connect the exterior portion 100 of ventricle chamber 94 to
atmospheric pressure. As soon as the century counter reaches the
count of 55 the "5" outputs of the units and tens BCD to decimal
converters 216, 218 go true causing the TLAR and ULAR signals to go
true, thereby activating the J input to flip flop 236. As the J
input is activated flip flop 236 switches to the true state to
provide a high voltage systolic signal which turns on power
switching amplifier 208 to activate the coil 210 in solenoid 84 and
connect the external portion 100 of ventricle chamber to the
selected systolic pressure. This systolic pressure is maintained
throughout the last 45 counts of the pumping cycle until the
century counter 204 recycles to again switch the systolic pulse
control signal to the low state. By setting the proportion switches
TL and UL at any desired count between 99 and 1 the systolic or
high pressure portion of each pumping cycle can be varied from 1 to
99 percent.
When both the units and tens proportioning switches are set to the
zero position, the B portion of the switch causes flip flop 236 to
be constrained to the zero state and the exterior portion 100 of
ventricle chamber is continuously vented to atmospheric pressure.
Similarly, when the tens switch is set to the number 10 position
the preset input of flip flop 236 is continuously activated causing
the flip flop to provide a continuous systole signal as a pulse
control signal to cause a systole pressure to be continuously
provided to the exterior portion 100 of ventricle chamber. Since
pulsatile pump 54 requires alternating systolic and atmospheric
pressures in the ventricle chamber to maintain pumping action, no
fluid will be pumped so long as the proportion switches are set to
provide continuous systolic or diastolic pressures at the ventricle
chamber. However, by setting the tens unit switch in the zero
position and manually alternating the ten switch between the zero
and ten position, both the frequency of the pumping cycle and the
relative proportions of systolic and diastolic pressure can be
controlled manually over any desired range.
Although there has been described above a particular arrangement of
a pulsatile pumping system in accordance with the invention, it
will be appreciated that the scope of the invention is not limited
thereto. Accordingly, any modification, variation or equivalent
arrangement within the scope of the appended claims should be
considered to be within the scope of the invention.
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