U.S. patent number RE29,346 [Application Number 05/610,043] was granted by the patent office on 1977-08-09 for single needle dialysis.
This patent grant is currently assigned to Vital Assists, Inc.. Invention is credited to Klaus F. Kopp.
United States Patent |
RE29,346 |
Kopp |
August 9, 1977 |
**Please see images for:
( Certificate of Correction ) ** |
Single needle dialysis
Abstract
Method and apparatus for extracorporeally dialyzing the blood of
a patient with only a single venipuncture including withdrawing
blood from the patient through the venipuncture and forcing the
blood along an arterial path to a dialyzer. Blood emerging from the
dialyzer is then conducted along a venous path again to the
venipuncture. The pressure is monitored in the extracorporeal
system to trigger occluding devices which alternately open and
close the arterial and venous paths so that undialyzed blood is
taken from the patient and dialyzed blood is injected into the
patient. The apparatus includes clamps actuated by a pressure
monitor to alternately obstruct the arterial and venous paths. A
blood pump may be controlled to operate as one of the clamps. In an
alternative embodiment, blood is circulated at a comparatively high
flow rate throughout the system. A clamp is provided in one of the
arterial or venous lines, said clamp being controlled by a pressure
monitor. When the clamp is closed, a pressure differential is
developed between the extracorporeal system and the patient so that
a volume of blood is exchanged between the system and the
patient.
Inventors: |
Kopp; Klaus F. (Kirchseeon,
DT) |
Assignee: |
Vital Assists, Inc. (Salt Lake
City, UT)
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Family
ID: |
26847141 |
Appl.
No.: |
05/610,043 |
Filed: |
September 3, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
149905 |
Jun 4, 1971 |
03756234 |
Sep 4, 1973 |
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Current U.S.
Class: |
604/6.05; 210/90;
604/6.1; 604/6.11 |
Current CPC
Class: |
A61M
1/30 (20130101); A61M 1/3639 (20130101); A61M
1/306 (20140204); A61M 1/309 (20140204) |
Current International
Class: |
A61M
1/36 (20060101); A61M 1/30 (20060101); A61M
005/00 (); A61M 001/03 () |
Field of
Search: |
;128/DIG.3,214R,214B,214E,214F,214.2,214.4,213,227
;210/90,321B |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Guarino et al. - Science, vol. 115, Mar. 1952, pp. 285-288. .
Shaldon et al. - Lancet - Oct. 19, 1963, p. 815. .
Twiss - Lancet - Nov. 1964, No. 7369, p. 1106. .
Piazza et al. - Trans. Amer. Soc. Art. Inter. Orgs., vol. X, Apr.
1964, pp. 136-138..
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Primary Examiner: Truluck; Dalton L.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed and desired to be secured by United States Letters
Patent is:
1. A method of dialyzing the blood of a patient with a single
cannula dialysis system having a dialyzer, a blood pump acting
thereon and openable clamp comprising the steps of:
cannulating the patient by placing a single cannula into the
bloodstream of the patient;
providing an extracorporeal bifurcated flow path in communication
with the cannula, the flow path having an arterial branch, a venous
branch and the blood dialyzer interposed therebetween;
continuously pumping the blood in the arterial branch toward the
dialyzer with a pump acting upon the arterial branch;
creating two pressure zones by situating the openable clamp along
the length of the venous branch, the first pressure zone defined by
the portion of the flow path downstream from the pump and upstream
from the clamp so as to include the dialyzer and the second
pressure zone being defined by the portion of the flow path
upstream from the pump and downstream from the clamp so as to
include the patient cannula;
developing increased pressure in the first zone and simultaneously
decreasing pressure in the second zone by closing the clamp and
continuously pumping blood in the arterial line so as to draw blood
from the patient; and thereafter
equalizing the pressure between the zones by opening the clamp
thereby permitting blood to be transferred to the patient.
2. A method of dialyzing the blood of a patient with a single
cannula dialysis system having a dialyzer, a blood pump acting
thereon and openable clamp comprising the steps of:
cannulating the patient by placing a single cannula into the
bloodstream of the patient;
providing an extracorporeal bifurcated flow path in communication
with the cannula, the flow path having an arterial branch, a venous
branch and the blood dialyzer interposed therebetween;
continuously pumping the blood in the arterial branch toward the
dialyzer with a pump acting upon the arterial branch;
creating two pressure zones by situating the openable clamp in the
arterial line upstream from the pump, the first pressure zone being
defined by the portion of the flow path downstream from the pump
and upstream from the clamp so as to include both the patient
cannula and the dialyzer and the second pressure zone being defined
by the portion of the flow path upstream from the pump and
downstream from the clamp;
developing increased pressure in the first zone by continuously
pumping the blood while closing the clamp thereby increasing the
pressure in the first zone to inject blood into the patient;
and
equalizing the pressure between the zones by opening the clamp and
permitting blood to be transferred from the patient to the flow
path. .Iadd. 3. A method of dialyzing the blood of a patient with a
single cannulation in a system including a pump and a hemodialyzer
connected together in a series configuration, and a single hollow
cannula having a bifurcated conduit connected thereto to provide an
arterial branch and a venous branch, coupled respectively to
opposed ends of the series connected pump and hemodialyzer, wherein
the interconnected conduit, pump and hemodialyzer define a closed
system connected to the single hollow cannula, comprising the steps
of:
cannulating the blood vessel of a patient with the single cannula
through which blood is withdrawn from and returned to the patient
through said system in alternate phases of successive cycles of
operation;
pumping blood from the patient to the hemodialyzer through the
arterial branch, while preventing the return of blood to the
patient through the venous branch;
sensing pressure in the closed system;
automatically occluding blood flow through the arterial branch to
stop the withdrawal of blood from the patient in response to the
sensing of a predetermined first pressure level in the closed
system, while permitting the return of blood to the patient through
the venous branch; and, alternately,
automatically occluding blood flow through the venous branch to
stop the return flow of blood to the patient in response to the
sensing of a predetermined second pressure level in the closed
system, while permitting blood withdrawal from the patient through
the arterial branch, so that blood is alternately withdrawn and
returned to the patient in alternate phases of each successive
cycle of operation of the system in response to the sensing of the
predetermined first and second pressure levels. .Iaddend. .Iadd. 4.
A method of dialyzing the blood of a patient with a single
cannulation in a system including a pump and a hemodialyzer
connected together in a series configuration, and a single hollow
cannula having a bifurcated conduit connected thereto to provide an
arterial branch and a venous branch, coupled respectively to
opposed ends of the series connected pump and hemodialyzer, wherein
the interconnected conduit, pump and hemodialyzer define a closed
system connected to the single hollow cannula, comprising the steps
of:
cannulating the blood vessel of a patient with the single cannula
through which blood is withdrawn from and returned to the patient
in alternate phases of successive cycles of operation;
pumping blood from the patient to the hemodialyzer through the
arterial branch, while preventing the return of blood to the
patient through the venous branch;
sensing pressure in the closed system downstream of the pump;
automatically occluding blood flow through the arterial branch to
stop the withdrawal of blood from the patient in response to the
sensing of a predetermined first pressure level in the closed
system, while permitting the return of blood to the patient through
the venous branch; and, alternately,
automatically occluding blood flow through the venous branch to
stop the return flow of blood to the patient in response to the
sensing of a predetermined second pressure level in the closed
system, wherein the first pressure level is higher than said second
level, while permitting blood withdrawal from the patient through
the arterial branch, so that blood is alternately withdrawn and
returned to the patient in alternate phases of each successive
cycle of operation of the system in response to the sensing of the
predetermined first and second pressure levels..Iaddend.
Description
BACKGROUND
1. Field of the Invention
The invention relates to extracorporeal hemodialysis and more
particularly to method and apparatus for dialyzing a patient's
blood with a single venipuncture or cannulation.
2. The Prior Art
Historically, kidney diseases have been of critical concern to
human life. Many kinds of kidney diseases interfere with the
function of the kidney such that the kidney ceases to remove waste
and excess water from the blood. When the kidney is sufficiently
impaired that a large portion of the waste products and water are
not removed from the blood, the life of the patient cannot be
preserved unless a way is provided for artifically performing the
function of the impaired kidney. Many new developments have come to
light which perform the function of the impaired kidney
extracorporeally. For example, see copending U.S. patent
application Ser. No. 106,184, filed Jan. 13, 1971. Nevertheless,
even with the existing improvements in extracorporeal kidney
apparatus, the same general procedure is used for dialyzing
patients' blood that was used very early in the treatment of kidney
disease.
For example, the most commonly accepted practice for dialyzing a
patient's blood extracorporeally requires the surgical creation of
a subcutaneous, arterio-venous fistula. Thereafter, the
subcutaneous venous system dilates secondary to the increase of
blood flow derived from the artery to the vein through the fistula.
Sufficient blood flow for dialysis is then obtainable by
venipuncture with large bore needles. Normally, two hollow needles
or cannulas with an internal stylet or trocar are used to perform
two venipunctures on the patient so that two blood-communication
sites exist simultaneously in the patient. Conventionally, blood is
withdrawn from one of the punctured blood vessels, forced through a
hemodialyzer and thereafter forced into the other.
The aforementioned procedure has been found to have serious
disadvantages both to the patient and to the attending physicians
and technicians. The problems are particularly aggravated because
most patients requiring extracorporeal hemodialysis must undergo
treatment as frequently as three to seven times per week. This
means that if every venipuncture were completely successful, a
patient would need to undergo from 6 to 14 venipunctures or
cannulations each week.
It is well-known that the duration and well-function of a fistula
created by venipuncture is inversely related to the number of
venipunctures. Tissue repeatedly subjected to the trauma of
venipuncture is much more susceptible to thrombophlebitis,
paravascular hemorrhage, clotting and infection. In fact, it is
commonly found in patients who have experienced a number of
venipunctures, that the tissues surrounding the most accessible
veins develop large hematomas which obscure the veins making
successful venipuncture extremely difficult because of insufficient
blood flow in the damaged blood vessels.
Also contributing to the problem is the fact that once one
successful venipuncture is made and blood is allowed to flow from
the patient's body toward a hemodialyzer, the blood volume in the
patient's body is reduced making the second venipuncture very
difficult. Historically, it has been found that while most skilled
physicians or technicians are able to perform the first
venipuncture with little difficulty, frequently a plurality of
attempts is necessary before a second venipuncture can be performed
on the same patient.
Additionally, while the pain and discomfort suffered by the patient
is understandable, the multiple attempts at venipuncture often
necessary to place the second needle results in increasing
apprehension, and anxiety on the part of both the patient and the
physician or technician attending the patient further reduces the
likelihood of successful venipuncture.
BRIEF DESCRIPTION AND OBJECTS OF THE INVENTION
The present invention, including novel method and apparatus,
reduces patient trauma and tissue damage by accommodating
extracorporeal hemodialysis with a single venipuncture. Generally,
once the venipuncture has been performed, blood is conducted away
from the venipuncture site through one branch of a bifurcated blood
path. The bifurcation is located next to the needle connector to
keep the resulting deadspace as small as possible. The blood is
forced through the extracorporeal hemodialyzer and thereafter
through the other branch of the bifurcated flow path again to the
venipuncture site. The method using the single venipuncture is made
possible by alternating the blood flow into and out of the patient
at the venipuncture site. A unidirectional pulsatile blood flow
thrugh the dialyzer is established by alternate occlusion of the
branches of the bifurcated blood path. For example, with one branch
occluded, blood is withdrawn from the patient through the other
branch into the hemodialyzer. The other branch is then occluded and
the blood is forced through the one branch again into the
patient.
It is, therefore, a primary object of the present invention to
provide an improved method of extracorporeal hemodialysis using a
single venipuncture for each treatment.
It is another primary object of the present invention to provide
improved apparatus facilitating extracorporeal hemodialysis with a
single venipuncture.
Another valuable object of the present invention is to provide an
improved system for single needle dialysis for providing
unidirectional pulsatile flow from the patient, to an
extracorporeal dialyzer and again to the patient.
One still further and no less important object of the present
invention is to provide a novel method of forcing blood through an
extracorporeal system at an accelerated rate with periodic
exchanges of blood volumes between the patient and the system.
These and other objects and features of the present invention will
become more fully apparent from the following description and
appended claims taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective illustration of a presently
preferred system for dialyzing a patient's blood using a single
venipuncture;
FIG. 2 is a schematic circuit diagram illustrating a presently
preferred pressure monitor circuit;
FIGS. 3 and 3a schematically illustrate internal components of a
presently preferred pressure monitor;
FIGS. 4 and 5 are schematic circuit diagrams respectively
illustrating alternative embodiments which may be used with the
system of FIG. 1 to control the operation of the blood pump;
FIG. 6 is a schematic perspective of another presently preferred
system for dialyzing a patient's blood using a single
venipuncture;
FIG. 7 is a partial cross-section of the flow chamber forming part
of the system of FIG. 6; and
FIGS. 8 and 9 are schematic diagrams of still other presently
preferred method embodiments of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference is now made to the prefered embodiments of the invention
as illustrated in the figures, like parts being designated with
like numerals throughout.
The System of FIG. 1
Referring now to FIG. 1, a blood vessel 22 is illustrated as having
been penetrated by a hollow cannula 24. Preferably, the penetration
has been performed according to any suitable technique such as
venipuncture. The cannula 24 may be of any suitable type and may be
made of radiopaque Teflon. One suitable cannula has been found to
be the Angiocath intravenous placement unit manufactured by Deseret
Pharmaceutical Company, Inc. Sandy, Utah. A 14-gauge catheter
having a length of between one and two inches has been found to be
most effective. Nevertheless, it is also presently preferred to use
a hollow needle or any other suitable hollow instrument which can
be effectively placed within a vein. In this specification, cannula
means any hollow tubing which can be placed in a patient's blood
vessel.
In the illustrated embodiment, the cannula 24 has an
outwardly-tapered female or luer fitting 26 which is securely
joined to a bifurcated coupling 28. Coupling 28 has an arterial
branch 30 and a venous branch 32, arterial branch 30 being
press-fit into a rubber or plastic tube 34. Tube 34 will
hereinafter be referred to as the arterial line 34.
Arterial line 34 is situated over the face 36 of a blood pump
generally designated 38. Blood pump 38 is conventional and normally
includes a rotatable shaft 40 upon which is mounted a transverse
bar 42. The bar 42 has, at its respective ends 44 and 46 rotatable
cylinders 48 and 50.
Approximately one-half of the circular path traversed by the
cylinders 48 and 50 is bordered by a semi-circular track 52. The
arterial line 34 is caused to follow the inside surface 54 of the
track 52. Thus, as the cylinders 48 and 50 traverse their circular
path about the axis of shaft 40, the arterial line 34 will be
squeezed between the respective cylinders and the track 52.
Conventionally, the bar 42 rotates clockwise around the shaft 40 so
that the squeezed portion of the arterial line 34 is developed
between the cylinder and the track 52 at the leading end 56 of the
track and progresses over the entire inside surface 54 of the track
to the trailing end 58 thereof. As the squeezed portion of the
arterial line 34 progresses over the inside surface of the track
52, blood in the arterial line 34 is forced to the dialyzer
generally designated 60. It can be appreciated that when the
cylinder 48 reaches the trailing end 58 of the track 52, the
cylinder 50 will engage the arterial line 34 at the leading end 56
so that a constant forward pressure is exerted on the blood to move
from the blood vessel 22 to the dialyzer 60 as long as the pump is
in operation.
Any suitable conventional dialyzer can be used with the present
system. An example of one suitable dialyzer which could be used in
the Coil EX-01 manufactured by Extracorporeal, Inc. Another
suitable dialyzer is described in pending designated S. Pat.
application Ser. No. 106,184, filed Jan. 13, 1971. Blood emerges
from the dialyzer 60 in the venous line 62 which is press-fit onto
the branch 32 of the coupling 28. Preferably, a bubble trap 64 is
interposed in the venous line 62 to prevent bubbles from passing
through the cannula 24 into the blood vessel 22. The bubble trap 64
may be any suitable conventional bubble trap such as that used with
blood infusion apparatus.
A pressure conductor 66 is connected into the bubble trap 64 above
the surface level 68 of the blood. Thus, pressure within the bubble
trap 64 and venous line 62 is transmitted through the conductor 66
to a pressure monitor generally designated 70. Similarly, a
pressure conductor 72 is connected into the arterial line 34 so as
to transmit pressure from the arterial line 34 to the pressure
monitor 70. It is presently preferred that an accumulator 74 be
interposed in the conductor 72 so as to provide an air pillow
between the blood in arterial line 34 and the pressure monitor 70.
The pressure monitor 70 is connected by electrical conductors 76
and 78 to the blood pump 38 and an electrically-operated clamp 80,
respectively.
The Pressure Monitor
In order to make single venipuncture hemodialysis possible, the
pressure monitor 70 has multiple set points. Furthermore, although
a single pressure monitor is illustrated in FIG. 1, it may be
desirable to have a plurality of pressure monitors to insure safety
in the system. A variety of suitable conventional pressure monitors
are commercially available, one suitable monitor being manufactured
by Cambridge Instrument Corporation of Great Britain. Most
conventional pressure monitors are operated with pressure
diaphragms or the like. However, the illustrated pressure monitor
70 uses a mercury manometer system. For ease of illustration, only
pressure monitor 70 will be described.
The pressure monitor 70 has a calibrated bezel 82 with indicia
thereon representing, for example, millimeters of mercury. An
indicator 84 is controlled by venous line pressure in conductor 66
so that when the venous line pressure in conductor 66 rises, the
indicator 84 rises to indicate the pressure in millimeters of
mercury (mm Hg). Similarly, when the pressure in conductor 66
drops, the indicator 84 drops to represent the decreasing pressure
in millimeters of mercury. Another indicator 86 is controlled by
the pressure in line 72 to indicate the pressure in the arterial
line in millimeters of mercury.
Manually adjustable set points are determined by the position of
markers 88, 90 and 92. For example, markers 88 and 90 respectively
set the upper and lower limits of blood pressure in the venous line
62 as will be subsequently more fully described. Similarly, marker
92 will set the lower limit of the pressure in the arterial line
34. Preferably, the pressure range accommodated by the monitor 70
for measuring the pressure in venous line 62 is on the order of
about zero to 300 mm Hg. The pressure range accommodated by the
monitor 70 for indicating the pressure in arterial line 34 is
preferably in a range on the order of about -150 to +200 mm Hg. Set
point accuracy of the markers 88 have been found most desirably to
be within .+-.5 mm Hg.
Although a variety of pressure measuring systems could be used, it
has been found that a mercury column manometer is both accurate and
dependable for use in the pressure monitor 70. The mercury column
manometer has the advantages of giving a continuous visual pressure
indication and is also a familiar instrument to medical personnel.
One presently preferred embodiment of the pressure monitor 70 is
illustrated in FIG. 3. With reference to FIG. 3, the pressure
conductor 66 is connected in pressure-tight relation to a hollow
fitting 190 on a mercury reservoir 192. The reservoir 192 is
integrally joined to an open column or tube 194 having a generally
U-shaped intermediate segment 196 disposed beneath the reservoir
192. As can be appreciated by referring to FIG. 3, the upper level
197 of the mercury 198 will seek the level of the reservoir. Thus,
the line 197, when even with the reservoir level, may be
interpreted as the zero pressure point for the FIG. 3 embodiment.
Preferably, the tube 194 is calibrated so that 300 mm Hg pressure
is required to move the line 197 to the point 300.
A cylindrical rod 202 is provided adjacent the column 194, the rod
202 being formed of light illuminable plastic. An incandescent lamp
or other suitable light source 204 is placed adjacent one end of
the rod 202 and, when the light source 204 is illuminated, the
entire rod 202 will become illuminated.
A plurality of photoelectric cells 94, 206 and 208 are disposed on
the other side of the column 14 diametrally opposite the rod 202.
The photocells 94, 206 and 208 are preferably shielded by structure
(not shown) which prevents light from the rod 202 from reaching the
photocell except through the column 194. The photocells may be
mounted on a vertical rack 209 and are preferably vertically
adjustable along the rack 209 by any suitable conventional
adjusting structure (not shown).
In the operation of the apparatus of FIG. 3, as the mercury 198
advances in the column 194, the mercury will obstruct the light
path between the rod 202 and the photocells 94, 206 and 208. More
specifically, for example, when the mercury advances to the mark
200, the photocell 94 will be de-energized because light from the
rod 202 will be obstructed by the mercury. Similarly, when the
mercury advances below the position of the photocell 94, the
photocell will be energized.
While the range of the column 194 in FIG. 3 is, for example,
between 0 and 300 mm Hg, any suitable pressure reading is possible
as is made clear from the schematic representation of FIG. 3a. In
FIG. 3a, the U-shaped portion 210 is substantially elongated over
the U-shaped portion 196 (FIG. 3), so that the zero point 212,
where the mercury comes to rest with the level of mercury in the
reservoir 192, is intermediate the length of mercury column 214.
Thus, for example, the mercury level 212 may fluctuate between
readings of approximately minus 150 mm Hg such as at point 216 to
approximately 200 mm Hg at point 218.
The mercury column manometer, when used in conjunction with the
photocell circuit illustrated in FIG. 2, provides for highly
accurate set point determination. Referring more specifically to
FIG. 2, photocell 94 is connected to a variable resistor 96 which
is a threshold control to determine the sensitivity of the
photocell 94. When photocell 94 is energized by the light source
202 (FIG. 3), the resulting signal will be amplified by stepped
transistors 98 and 100 so as to energize relay drive 102. Relay
driver 102 controls the operational state of relay 104 which, in
turn, controls the function of solenoid clamp 80 (FIG. 1). When the
pressure in venous line 62 is below the set point 88, the photocell
94 will be exposed to the light source thereby energizing relay
driver 102 and switching the relay 104 to an "on" position to
actuate the solenoid clamp 80 (FIG. 1). The clamp 80 then closes
and occludes the venous line 62. With the venous line 62 occluded,
the pressure in the line 62 will rise until the indicator 84
reaches the set point determined by marker 88. At that moment, the
mercury 198 in column 194 (FIG. 3) will have risen sufficiently to
obstruct the light from the light source 202 to the photocell 94
thereby turning the photocell 94 off. The relay driver 102 is then
no longer energized and relay 104 is switched to the "off" position
thereby opening the solenoid clamp 80. A conventional time delay
circuit may be used to prevent for a predetermined time period
re-actuation of relay 104 when the mercury drops to expose
photocell 94 to the light source 202.
A separate solenoid circuit which may be substantially identical to
that shown in FIG. 2 may be provided for each of the set points
determined by markers 90 and 92. Additionally, if desired, a third
set point (not shown in FIG. 1) may be provided to correspond to
photocell 208 (FIG. 3) so as to act as a "safety low" set point
which is normally slightly lower than the set point indicated by
marker 90. Thus, in the event a membrane or coil in the dialyzer 60
ruptures, an instantaneous drop in pressure to the "safety low" set
point will actuate the solenoid 80 to an open position and the pump
38 to stop to protect the patient.
In the system illustrated in FIG. 1, the pressure monitor 70 also
controls the operation of the blood pump 38. Referring specially to
FIG. 4, the relay 104, controlled by the photocell circuit
illustrated in FIG. 2, is energized so that the relay driver 102
disconnects solenoid line 78 from the circuit. The solenoid 80
responds by clamping the venous line 62 closed. Simultaneously, the
motor 38 is energized to draw blood from the venipuncture in blood
vessel 22 and drive it toward the dialyzer 60. When the pressure
reises, as above described, the relay 104 will reverse to open the
clamp 80 and stop the pump 38. Pump 38 thus functions as a second
clamp.
It has been found that the blood pump 38 does not instantaneously
stop when it is disconnected from the circuit by the pressure
monitor 70 because of the moment of inertia of the blood pump
motor. Accordingly, in the illustrated embodiment of FIG. 4, the
armature 110 of the motor 38 is connected through a resistor 112 to
the relay 104. The size of the resistance is selected so as to
convert essentially all of the kinetic energy of the motor into
heat for dissipation through the resistor 112 when relay 104 turns
the motor off.
While the embodiment illustrated in FIG. 4 has been found to
operate satisfactorily, the start-stop frequency of the motor has
been found to be as much as 30 to 60 times a minute. Because the
armature current passing through the relay is quite high, the relay
104 has been found to wear out quite rapidly. In order to extend
the operating life of the relay, the embodiment of FIG. 5 was
developed. The circuit embodiment of FIG. 5 differs from the
embodiment of FIG. 4 principally in that transistors 114 and 116
are used to switch the motor 38 off and on, respectively. The
transistors reduce the actual amount of current passing through the
relay 104 so as to preserve the life of the relay.
The Method of the FIG. 1 Embodiment
Having described the apparatus of FIG. 1, the method of dialyzing a
patient's blood with a single venipuncture will now be
described.
Initially, the set points on the pressure monitor 70 are adjusted
by moving the markers 88, 90 and 92 to represent the desired venous
high and low pressures and the desired arterial low pressure,
respectively. The arterial and venous lines are primed by filling
the lines with isotonic saline. When a single venipuncture or
cannulation has been performed, the arterial and venous lines 34
and 62 are filled with blood.
The blood pump 38 is energized so as to force blood through the
arterial line toward the dialyzer 60. As has been previously
described, when the blood pump 38 is in operation, the solenoid
clamp 80 is closed thereby occluding the flow of blood through the
venous line 62. Thus, continued rotation of the pump 38 develops an
increasing pressure in the venous line 62 above the clamp 80. The
increased pressure is communicated through the conductor 66 to the
pressure monitor 70. As the indicator 84 progressively advances up
the pressure scale on bezel 82, it will be brought into coincidence
with marker 88. Advancement of the indicator 84 is concurrent with
the elevational rise of the mercury 198 in the mercury column 194
(FIG. 3). When the mercury 198 effectively eliminates light from
the source 202 to the photocell 94, the relay driver 102 (FIG. 2)
will be de-energized simultaneously opening the solenoid switch 80
and turning the motor 38 off through the circuit illustrated in
FIGS. 4 or 5.
When the pump 38 is off, the engaging one of the cylinders 48 or 50
will serve as a clamp to occlude the arterial line 34 and prevent
inflow of blood through the cannula 24 and coupling 28. While the
pump 38 is stopped, the increased pressure in the venous line 62 is
reduced by pushing the blood in venous line 62 through the coupling
28 and catheter 24 again into the blood vessel 22 of the patient.
As the pressure in venous line 62 is reduced, the indicator 84 will
gradually drop. The time delay in the circuit of FIG. 2 prevents
the relay 104 from switching until the selected time interval has
been covered.
Thereafter, the solenoid clamp 80 is energized by action of the
time delay relay to the illustrated occluded position and the pump
38 is again energized to draw blood from the blood vessel 22
through the cannula 24. In the event the arterial line 34 becomes
obstructed such as with a clot or the like, the arterial line
pressure in conductor 72 will drop the indicator 86 to the minimum
set point at marker 92. When the indicator 86 reaches this low
point, the pump 38 will be turned off in order to protect the
patient. In the event a coil or membrane in the dialyzer 60 is
ruptured, the emergency set point (determined by photocell 208
shown in FIG. 3) will be triggered to shut off both the blood pump
and the solenoid 80.
The activation or deactivation of the solenoid, double solenoid or
blood pump can either be achieved by letting the pressure travel
inbetween two set points or by oscillating around one set point.
The latter method (which is preferred) necessitates a time delaying
device which prolongs one phase of the cycle. This phase can be
chosen either to be a phase of prolonged occlusion or prolonged
opening of the solenoid. Regarding the different possibilities
described, this will result in prolongation of phases with rising
or falling pressures.
In general, in case of coil rupture, the blood pump should stop and
the venous solenoid should open (in order to return as much blood
to the patient as can be recovered).
The Embodiment of FIGS. 6 and 7
FIG. 6 illustrates another presently preferred dialyzing system
utilizing a single venipuncture. The FIG. 6 embodiment differs from
the FIG. 1 embodiment primarily in that the pump 38 is continuously
operating and the single solenoid clamp 80 has been replaced by a
double solenoid clamp 150. The solenoid clamp 150 has parallel
channels 152 and 154 through which the venous and arterial lines 62
and 34, respectively, pass. The solenoid has a detent 156 in each
of the channels 152 and 154, the detent 156 being selectively
actuated alternately into channel 152 or 154. Control of the detent
is provided through electrical conductors 160 and 162 connecting
the solenoid clamp 150 to the pressure monitor 70.
Additionally, the system of FIG. 6 has an arterial flow chamber
generally designated 164 and more clearly illustrated in FIG. 7.
The flow chamber 164 is preferably formed of a rigid cylindrical
member 166 which may be formed of plastic and is desirably
transparent. The member 166 is fitted with an air-tight cap 168
into which one end of the arterial line 34 is mounted. The member
166 has a downwardly tapered portion and terminates in a male
coupling 170. Another portion of the arterial line 34 is press-fit
onto the male coupling 170. The cap 168 also serves as a mounting
site for pressure-conducting tube 74 and a blood level adjuster
generally designated 172. The blood level adjuster may comprise a
conventional hypodermic syringe connected to the cap 168 by a
plastic tube 174. Where desired, the tube 174 may be clamped to
maintain pressure communication through conductor 72.
The Method of FIGS. 6 and 7
The arterial and venous lines 34 and 62 are primed with isotonic
saline as described in connection with FIG. 1 above. The pump 38
operates continuously. Assuming that the venous line 62 is occluded
by solenoid 150, blood is withdrawn from the patient's blood vessel
22 through the cannula 24 and arterial line 34 into the arterial
flow chamber 164. The blood is then pumped out of the arterial flow
chamber to the dialyzer 60. Continued pumping by the pump 38 causes
the pressure in the venous line 62 to increase because of the
occlusion in the channel 152. As the pressure rises, the indicator
84 will rise to the set point determined by marker 88. When the set
point is reached, solenoid 150 will be actuated to open the venous
line 62 and to occlude, simultaneously, the arterial line 34. The
high pressure in the venous line 62 will then cause the blood
therein to flow through the adapter 28, cannula 24 and into the
blood vessel 22.
Referring again to FIG. 7, the continued operation of the blood
pump 38 causes blood to flow out of the arterial flow chamber
thereby decreasing the pressure in the member 166, the decreased
pressure being communicated through line 72 to the pressure monitor
70. When the time which has been preset by the time delay relay has
elapsed, the pressure monitor 70 will again actuate the solenoid
clamp 150 to close the venous line 62 and open the arterial line
34. Blood will again be drawn from the patient through the arterial
line 34 to replenish the reservoir in the arterial flow chamber 164
and also to conduct the blood through the dialyzer 60 as the cycle
is again commenced.
From the foregoing, it can be appreciated that effective dialysis
of a patient's blood can be obtained with a single venipuncture.
Moreover, it has been found that the small amounts of blood which
are recycled through the system at the adapter 28 do not
unfavorably influence the efficiency. A surprising amount of the
blood is withdrawn from the patient and again injected into the
patient with each cycle in the system. Moreover, it has been found
that a patient's dialysis time using the single venipuncture method
is only slightly increased if at all, in most cases, over the prior
art double venipuncture method.
The Embodiments of FIGS. 8 and 9
The embodiments of FIGS. 8 and 9 maximize the tendency of the blood
to "short-circuit" at the bifurcated coupling 28. In this
embodiment, a substantial portion of the blood is intentionally
recirculated a plurality of times through the arterial line 34, the
dialyzer 60 and the venous line 62. A suitable blood pump 220
continually operates at a comparatively high rate of speed so that
the blood is forced through the dialyzer, venous and arterial lines
at the rate of approximately 300 to 400 milliliters per minute. As
can be appreciated, this flow rate is approximately twice as great
as the flow rate from the patient through a dialyzer in the systems
of FIGS. 1 and 6.
In order to dialyze the patient's blood, only a single clamp 222 is
necessary. In FIG. 8, clamp 222 is located in the venous line 62
below the bubble trap 64. Alternatively, as shown in FIG. 9, the
clamp 222 may be disposed in the arterial line 34 beneath the
arterial flow chamber 164.
In the method embodiment of FIG. 8, the system is primed with
saline as above described and blood is gradually drawn into the
arterial line 34 as will now be more particularly described. When
the clamp 222 is in the closed or occluding position, the pump 220
will continue to draw blood from the patient and force the blood in
the arterial line 34 through the dialyzer 60. Thus, a pressure will
develop in the venous line 62, said pressure being conducted
through line 66 and monitored by the pressure monitor 70. When the
pressure reaches a predetermined high set point, the clamps 222
will be activated to the open position. At that moment, the
pressure in the venous line will be greater than the pressure in
the arterial line and in the patient's blood stream. The pressure
is equalized by displacing one volume of dialyzed blood into the
patient and another volume of dialyzed blood again into the
arterial line 34.
After a particular predetermined time period has elapsed or, as
soon as the pressure in line 66 has dropped to a predetermined
level, the clamp 222 will again occlude the venous line 62 to
develop pressure above the clamp 222. It is observed that as soon
as the clamp 222 is closed, a vacuum is developed in the arterial
line 34 below the pump 220. This vacuum is filled by drawing blood
from the patient into the arterial line 34. When the pressure in
line 66 reaches the predetermined set point in the monitor 70, the
clamp 222 is again opened and the blood under pressure in the
venous line 62 will be forced toward the bifurcated coupling 28.
Because the line 34 has been filled with blood while the clamp 222
was closed, a substantial portion of the blood under pressure in
the venous line 62 will be forced through the coupling 28 into the
patient.
An alternative to the described method embodiment is illustrated in
FIG. 9. In FIG. 9, the clamp 222 is located in the arterial branch
34 beneath the flow chamber 164. The pump 222 is in continual
operation at a comparatively high flow rate, similar to that
described above so that a flow rate of approximately 300 to 400
millimeters per minute exists in the system. When the clamp is
closed, blood will be forced by the pump 220 through the dialyzer
60 and venous line 62 so that the blood is forced into the patient
through the bifurcated coupling 28. Continued pumping with the
clamp 222 closed causes the pressure in the chamber 164 to be
reduced, said pressure reduction being reflected through conductor
74 and monitored in the pressure monitor 70. When the pressure in
monitor 70 reaches predetermined low set point, clamp 222 will open
thereby allowing the pump 220 to draw blood from the patient
through the bifurcated coupling 28 and the venous line 62. The
volume of blood required to equalize the pressure is greater than
can be supplied from venous line 62 so that a substantial volume of
blood is drawn from the patient.
The embodiments of FIGS. 8 and 9 have been found to provide some
unusually valuable advantages over other types of dialysis systems.
For example, the very high flow rate causes much turbulence in the
dialyzer which breaks up the boundary layers normally existing in
the dialyzer thereby substantially increasing diffusion across the
membrane. Moreover, inasmuch as flow through the dialyzer is
normally laminar, the turbulence developed by the high flow rate
causes the erythrocytes to have a brushing effect against one
another and against the membrane to further increase the rate of
dialysis.
Inasmuch as a substantial portion of the blood in the system is
circulated through the dialyzer a plurality of times before being
reinjected into the patient, the blood normally in the
extracorporeal system has an unusually low concentration of waste
substances. Thus, when blood is drawn from the patient into the
system, there is blood-to-blood diffusion as the infusing blood is
mixed with the recirculating blood in the system. It has been found
that the method set forth in FIGS. 8 and 9 achieves a surprisingly
high dialysis efficiency.
The invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive and the scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
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