U.S. patent application number 13/325445 was filed with the patent office on 2012-04-19 for chronic access system for extracorporeal treatment of blood including a continuously wearable hemodialyzer.
Invention is credited to Arnold J. Lande.
Application Number | 20120095402 13/325445 |
Document ID | / |
Family ID | 39588936 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120095402 |
Kind Code |
A1 |
Lande; Arnold J. |
April 19, 2012 |
Chronic Access System for Extracorporeal Treatment of Blood
Including a Continuously Wearable Hemodialyzer
Abstract
A patient wearable, continuously operating extracorporeal pump
apparatus which accesses the patient's arterial venous pressure
differential by applying external pressure to a subcutaneous graft
that has been cannualized to modulate blood flow through an
extracorporeal circuit and to drive the pump for delivering a
medicament, such as an anticoagulant, to the site of an intravenous
cannula to prevent clogging thereof and also to move a dialysate
through a circuit, including a dialyzer and a dialysate
rejuvenating cartridge, whereby kidney failure can be treated
without recourse to prior art hemodialysis machines found in most
treatment facilities. With slight modification, the present
invention can be used to remove excess fluids from CHF patients, to
remove toxins from the blood in those suffering from liver failure
and to facilitate administration of insulin to diabetics and/or
glucose to those having hypoglycemia.
Inventors: |
Lande; Arnold J.; (St. Paul,
MN) |
Family ID: |
39588936 |
Appl. No.: |
13/325445 |
Filed: |
December 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12448178 |
Jun 11, 2009 |
8109893 |
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PCT/US07/25864 |
Dec 19, 2007 |
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13325445 |
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60875633 |
Dec 19, 2006 |
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Current U.S.
Class: |
604/151 |
Current CPC
Class: |
A61M 1/3655 20130101;
A61M 2205/123 20130101; A61M 1/1696 20130101; A61M 1/1605 20140204;
A61M 2205/3324 20130101; A61M 2205/126 20130101; A61M 1/3672
20130101; A61M 1/3675 20130101; A61M 2209/088 20130101; A61M
2205/8206 20130101; A61M 2205/3317 20130101; A61M 1/16 20130101;
A61M 1/3661 20140204 |
Class at
Publication: |
604/151 |
International
Class: |
A61M 5/142 20060101
A61M005/142 |
Claims
1-42. (canceled)
43. A medical device for delivering metered quantities of a
medicament into a patient's vascular system comprising: (a) a
reservoir containing a medicament, the reservoir being in fluid
communication with at least one percutaneous cannula via a
compressible tube segment; and (b) an extracorporeal peristaltic
pump having a roller coacting with the compressible tube segment
and adapted to be powered by the patient's arteriovenous pressure
differential for moving the medicament through the at least one
cannula.
44. The medical device of claim 43 wherein the reservoir is in
fluid communication with the cannula via a compressible tube
segment and the pump is a peristaltic pump having a roller coacting
with the compressible tube segment.
45. The medical device of claim 44 wherein said peristaltic pump
comprises: (a) a frame having a central opening; (b) a lever plate
pivotally mounted to the frame and occupying the central opening;
(c) first and second expandable and compressible ventricles each
having an inlet port and an outlet port and adapted to be
selectively filled and emptied of the patient's blood disposed on
opposed sides of the lever plate and arranged such that expanding
the first bladder pivots the lever plate in a direction to compress
the second ventricle and expanding the second bladder pivots the
lever plate in a direction to compress the first ventricle; (d)
means for selectively opening and closing said inlet ports and
outlet ports of the first and second bladders; and (e) means
coupling the pivotally mounted lever plate to the roller for
rotating the roller in one of a clockwise or counter-clockwise
direction.
46. The medical device of claim 45 wherein the first and second
ventricles each have an inlet port and an outlet port and are
adapted to be selectively filled and emptied of the patient's blood
in expanding and compressing the first and second ventricles,
respectively.
47. The medical device of claim 43 wherein the medicament is an
anti-coagulant.
48. The medical device of claim 46 and further including means for
selectively opening and closing said inlet ports and outlet ports
of the first and second bladders.
49. The medical device of claim 48 wherein said means for
selectively opening and closing said inlet ports and said outlet
ports comprises: (a) permanent magnets slidably mounted in the
frame and individually in alignment with the inlet ports and outlet
ports of the first and second ventricles; and (b) electromagnets
disposed relative to the permanent magnets to selectively attract
and repel the permanent magnets.
50. The medical device of claim 45 and further including: (a) a
dialyzer having a plurality of semi-permeable membranous wall
surfaces contained within a liquid impervious housing, said housing
having a pair of inlet ports and a pair of outlet ports; (b) means
for connecting a first of the pair of inlet ports and a first of
the pair of outlet ports into the vascular system of a lower
animal; (c) means for connecting a second of the pair of inlet
ports and a second of the pair of outlet ports in the vascular
system of a human patient; and (d) the first and second inlet ports
and the first and second outlet ports in the housing arranged such
that blood of the lower animal flows on one side of the wall
surfaces and blood of the human patient flows over a second side of
the wall surfaces.
51. The medical device of claim 46 wherein the means for connecting
the first and second inlet ports includes at least one cannula.
52. A method for obtaining access to a patient's arteriovenous
pressure differential comprising the steps of (a) selecting a
venous segment in the patient's forearm and surgically debranching
the selected venous segment and tying off the distal end thereof;
(b) surgically anastomosing the distal end portion of the
debranched vein to a selected artery in the patient's forearm; (c)
inserting a needle cannula percutaneously into the debranched vein
segment; and (d) sequentially applying pressure to the forearm
sufficient to substantially occlude blood flow through the
debranched vein segment and releasing the pressure whereby when the
pressure is being applied, the needle cannula is exposed to
arterial pressure and when released, the cannula is exposed to
venous pressure.
53. A method for obtaining therapeutic anticoagulation of an
extracorporeal circuit comprising the steps of: providing the
medical device of claim 43, where the medicament is an
anti-coagulant; (a) percutaneously inserting the cannula into a
debranched vein segment or a VFG; (b) periodically compressing and
releasing the debranched vein segment or the VFG to expose the
blood exiting and entering said cannula to arterial pressure and
venous pressure; and (c) actuating the pump being activated based
on the difference between the arterial pressure and the venous
pressure of the blood entering and exiting the cannula.
54. The method of claim 53 and further including the steps of: (a)
providing a dialyzer having a plurality of semi-permeable membranes
within an outer housing; (b) connecting the dialyzer to the cannula
such that blood flows through a ventricle to power the pump and
thence over a first surface of the plurality of membranes; (c) the
pump circulating dialysate through the housing and over a second
surface of the membranes in proportion to the flow rate of the
blood through the dialyzer; and (d) providing a dialysate
rejuvenating cartridge using the pump to move dialysate through
said cartridge.
55. The method of claim 54 and further including the step of: (a)
providing a dialysate rejuvenating cartridge using the pump to move
dialysate through said cartridge.
56. The method of claim 55 and further including the step of: (a)
providing an amberoid for blocking dialysate flow through the
cartridge after a predetermined period of use of the dialysate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a Divisional Application of
National phase application Ser. No. 12/448,178, filed Jun. 11,
2009, based upon PCT application serial no. PCT/US07/25864, filed
Dec. 19, 2007, and based upon U.S. Provisional Application Ser. No.
60/875,633, filed Dec. 19, 2006, the contents of each are hereby
being incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to artificial organs and in
particular to a blood access system for the treatment of end stage
kidney failure. The apparatus comprising a preferred embodiment
includes a patient-wearable, extracorporeal system which accesses a
patient's arterial/venous pressure differential and regulates the
extracorporeal arteriovenous blood flow and proportionally with
that blood flow, pumps and regulates dialysate flow in the case of
hemodialysis (HD) for kidney failure. The externally wearable unit
offers portable, continuous, HD for a patient. The HD unit of this
invention also proportionally with the blood and dialysate, pumps
and regulates anti-coagulant and CaMg additions.
[0004] 2. Discussion of the Prior Art
[0005] Patients suffering from chronic end stage renal disease or
acute traumatic kidney failure regularly undergo the process of HD
in which chemical waste and water are removed from the blood using
a system of semi-permeable membranes. Conventional chronic
treatment requires the patient to remain sedentary for three
sessions per week. Each treatment session constitutes approximately
three to six hours at a treatment center or at home and additional
hours for travel and recovery. It is an uncomfortable and tiring
procedure, since patients must remain sedentary and because of the
rapid rate at which their body fluids are adjusted toward normal.
Approximately 100 times the usual daily intake of water, in the
form of dialysate, passes by the artificial membranes opposite the
blood during an average session. Consequently, failure of the
dialysate preparation or membrane conduction systems may have
severe consequences.
[0006] The process of HD becomes necessary when disease or trauma
causes the kidneys to fail or become so impaired that they no
longer adequately remove toxins and/or water from the blood. It
involves mechanically and chemically assisted removal of toxins
(largely urea) and water in a manner that restores a balance of
fluids and electrolytes in the blood. The essential components for
this process are a semi-permeable membrane and a dialysate solution
that will absorb the unwanted blood components after they have
passed through the membrane. A way of preventing clotting of blood
in and around the dialyzer unit is required.
[0007] Interest in miniaturizing the equipment used in hemodialysis
has resulted in the availability of small portable (as opposed to
truly ambulatory) dialysis devices. Ash and Kessler in U.S. Pat.
No. 4,071,444 provide an example of a portable dialysis
machine.
[0008] As is pointed out in the Twardowski U.S. Pat. No. 5,336,165
there is a real need for equipment that will make at-home
hemodialysis possible. There are nearly 500,000 patients on
dialysis in the United States at any one time. Most of these
patients must visit kidney dialysis centers three times a week and
spend several hours on each of those days tied to a machine that
includes an extracorporeal circuit for extracting blood, "cleaning"
it, and returning it back into the patient. This not only exposes
the patient or a third-party payer to very significant medical
costs, but also adversely affects quality of life considerations.
In an attempt to address this problem, Twardowski describes an
at-home hemodialysis system that includes a dialyzer membrane and
provision for passage of a dialysis solution along one side of the
membrane and blood with ureinic components along the other
side.
[0009] The Beltz U.S. Pat. No. 5,284,470 describes a portable,
artificial kidney in the form of a self-contained unit whose size
and shape is such that it is lightweight and relatively small so
that it can be worn by the patient who is able to go about routine
daily activities. The Beltz system includes a blood plasma
separator unit, a chemical treatment unit, and a water removal
unit. It also includes a cannula inserted in an arteriovenous shunt
for gaining access to the patient's blood stream. The toxic whole
blood is routed to the artificial kidney and then returned in
detoxified form back to the patient. The artificial kidney includes
a separator packet for extracting a predetermined amount of plasma
from the patient's blood and then a further packet containing a
treatment chemical for cleansing the plasma is included in the flow
path. Means are provided to remove water from the plasma before the
cleansed plasma is returned to the patient's body. Blood flow
through the unit is due primarily to the hydrostatic blood pressure
of the patient, but it is recognized that a lightweight pump and
battery may be needed to generate additional pressure for routing
the cleansed plasma back into the patient.
[0010] A continuous-use ambulatory hemodialysis unit is described
in U.S. Pat. No. 3,864,259 of Newhart. It features a harness that
secures a dialysate reservoir to the patient's hip and a perfusion
unit on the anterior thigh, connected to a femoral shunt. The
perfusion unit has multiple dialysis tubules bathed in dialysate,
enabling the removal of waste products from the blood in the
tubules. The apparatus consists of seven exterior parts: harness,
diaphragm pump, reservoir, perfusion unit, dialysate exchange unit,
and femoral arterial and venous cannulae. The exchanger is smaller
than the perfusion unit at approximately 8.5 cm.times.6 cm and 1 cm
deep. It should be apparent that this apparatus is cumbersome and
uncomfortable.
Objects
[0011] A principal object of the invention is to provide a new and
improved apparatus for extracorporeal treatment of blood, including
hemodialysis and hemofiltration in the form of a wearable unit.
This wearable HD unit is more convenient than standard treatment,
since it performs HD substantially continuously, 24 hours a day, 7
days a week, and largely eliminates the need for time-consuming,
sedentary, hospital or clinic dialysis. The patients are also
spared the alternative of having to endure liters of an
ascites-like peritoneal dialysis solution in their abdominal cavity
and needing to spend several hours each day carrying out the
necessary fluid exchanges for CAPD.
[0012] A further object is to broaden applicability by utilizing a
blood arterio/venous pressure differential powered pump design that
offers mechanical advantage due to the lever arm principle. This
particular pump design has broad application as an extracorporeal
blood treatment system, independent of the hemodialyzer
component.
[0013] Yet another important object of the invention is to provide
an apparatus that nearly continuously accesses A/V pressure
differential by interchangeably applying external pressure over a
subcutaneous plastic fistula graft or an in situ debranched
arteriovenous fistula segment, at two separate sites so as to avoid
tissue necrosis.
[0014] A still further object of the present invention is to
provide a patient-wearable hemodialysis and/or hemofiltration
system which is miniaturized such that it is wearable without
discomfort and conveniently situated on a patient's limb, as on the
wrist and forearm.
SUMMARY OF THE INVENTION
[0015] The present invention comprises a blood dialysis apparatus
for ambulatory patients so that substantially continuous removal of
urea, water, salts and other waste products from the patient's
blood stream is accomplished. Supplementary accelerated
hemofiltration can also be accomplished at night in a recumbent
setting by applying suction around a collection bag. The device
comprises a pair of superposed flexible cuffs adapted to be wrapped
about and secured to a limb of a patient, each cuff comprising
first and second superposed sheets of plastic film selectively
bonded to one another to define a plurality of isolated fluid flow
paths including, but not limited to, a blood circuit, a dialysate
circuit, an anti-coagulant administrative path and a
calcium-magnesium (CaMg) introduction path.
[0016] Enclosed in the cuff is a liquid impervious chamber
containing a plurality of hollow, tubular dialysis/hemofiltration
fibers. The chamber is connected in the blood circuit and the
dialysate circuit such that blood can flow through the lumens of
the tubular dialyzer fibers from an inlet end to an outlet end
thereof while dialysate flows about the exterior of the dialysis
fibers within the chamber. Alternatively, the chamber can be
arranged on that the dialysate flows through the lumens and the
blood over the fiber exteriors. The cuff also temporarily supports
one or more parallel-chambered dialysate toxins adsorbing
cartridges.
[0017] A first cannula is used to access arterial blood that is
coupled through the blood circuit to an inlet end of the tubular
dialyzer fibers and a venous cannula is coupled to the outlet end
of those dialyzer fibers. The anti-coagulant administration path
preferably includes a first compressible reservoir for containing a
quantity of a liquid anti-coagulant drug. Likewise, the CaMg path
includes a flexible compressible chamber for containing a solution
of calcium and magnesium ions.
[0018] A specially designed pump arrangement is provided that is
adapted to be actuated by blood flow through the blood circuit to
force proportionally metered quantities of anti-coagulant drug from
the first compressible reservoir to a location near the inside of
the tip of the arterial cannula and a proportionally metered
quantity of CaMg solution from the second compressible reservoir
into the dialysate inlet to the dialyzer.
[0019] In accordance with the operation, the pump arrangement may
comprise a first roller cage disposed over one of the first and
second disposables and overlying a portion of first anti-coagulant
and first CaMg paths and a second roller cage disposed over a
second of the first and second RF sealed disposables, overlying
portions of the second anticoagulant and the second CaMg paths. The
roller cages are adapted to be rotated by a wedge-shaped lever and
a ratchet pawl that is actuated by the flow of the patient's blood
due to the arterial/venous pressure differential and when
cooperating with the flexible flow paths, acts as a peristaltic
pump for delivery of the anticoagulant and the CaMg solution.
[0020] Basic to the concept is the method for obtaining access to
arterial and venous pressures, chronically, by biweekly inserting
small catheters into plastic fistula grafts or a debranched venous
equivalent, both proximal and distal to reciprocal compression
sites. Also basic to the concept is how control of the rate of
extracorporeal blood flow is exercised, how a dialysate flow rate
proportional and approximately equal to the blood flow is
maintained and how proportional control over the rate of the pump
delivering the anticoagulant and CaMg supplements is maintained.
All of these are accomplished by a swinging lever mechanism whose
displacement is based on controlled blood flow in and out of
expandable ventricles in the disposable cuffs blood circuit. The
lever serves to appropriately limit and define blood flow and to
transfer power from the blood to the dialysate, anticoagulant, and
CaMg delivery functions.
DESCRIPTION OF THE DRAWINGS
[0021] The foregoing features, objects and advantages of the
invention will become apparent to those skilled in the art from the
following detailed description of preferred embodiment, especially
when considered in conjunction with the accompanying drawings in
which like numerals in the several views refer to corresponding
parts.
[0022] FIG. 1 is a perspective view of the wearable hemodialyzer
constructed in accordance with a preferred embodiment of the
present invention; and
[0023] FIG. 2 is an exploded view of the wearable hemodialyzer of
FIG. 1;
[0024] FIG. 3 is a perspective view of the device of FIG. 1 with
the top end plate and disposable layers removed to reveal internal
working parts thereof;
[0025] FIG. 4 is a perspective view of the non-disposable part of
the device of FIG. 1, but with top end plate and part of the
cartridge assembly removed;
[0026] FIG. 5 is a view of the device taken with the top end plate,
pump frame and cartridge removed to reveal the bottom end plate
configuration;
[0027] FIG. 6 is an enlarged perspective view of the bottom end
plate which is substantially a replication of the top end
plate;
[0028] FIG. 7 is a plan view of the lower disposable blood
contacting layer;
[0029] FIG. 8 is a plan view of the upper disposable blood
contacting layer;
[0030] FIG. 9 is a detailed exploded view of the non-disposable
pump frame subassembly used in the wearable hemodialyzer of the
present invention;
[0031] FIG. 10 is an electrical schematic diagram of a polarity
reversing circuit employed;
[0032] FIG. 11 is a plan view of an alternative lower disposable
blood co-acting layer when implementing an artificial liver;
[0033] FIG. 12 is a plan view of an alternative lower disposable
blood co-acting layer when implementing a device for treating
Congestive Heart Failure (CHF);
[0034] FIG. 13 is a plan view of an alternative lower disposable
blood co-acting layer when implementing an artificial pancreas
diabetes control; and
[0035] FIG. 14 is a volar view of blood vessels in the left forearm
with in situ debranched vein fistula graft.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] Certain terminology will be used in the following
description for convenience in reference only and will not be
limiting. The words "upwardly", "downwardly", "rightwardly" and
"leftwardly" will refer to directions in the drawings to which
reference is made. The words "inwardly" and "outwardly" will refer
to directions toward and away from, respectively, the geometric
center of the device and associated parts thereof. Said terminology
will include the words above specifically mentioned, derivatives
thereof and words of similar import.
[0037] Referring to FIG. 1 and the exploded view of FIG. 2, there
is indicated generally by numeral 10 a preferred embodiment of the
invention, namely, a portable, wearable, hemodialyzer. It is seen
to comprise a layered construction of a rigid non-disposable top
end plate 12, an upper, flexible, blood contacting plastic
disposable member 14, a non-disposable, rigid molded-plastic pump
frame 16, a lower, disposable, plastic, blood-contacting member 18
and a non-disposable bottom end plate 20. The aforementioned
components are adapted to be mounted onto a rigid, non-disposable
base plate member 22 to which a replaceable dialysate-restoring
cartridge members 24 and 26 is also adapted to be removably affixed
in a manner that will be more particularly described herein below.
A battery 28 is also removably clamped to the base plate 22 and is
used to power an electronic timing control circuit (FIG. 10) and
electromagnets 30, 32 that are affixed to the top plate 12 and
electromagnets 34 and 36 that mount to the underside of the lower
bottom end plate 20.
[0038] Concentrating first on the upper disposable, plastic,
blood-contacting member 14 that is more particularly illustrated in
the plan view of FIG. 8, it is seen to comprise first and second
flexible plastic sheets that are RF welded or otherwise bonded
together in a predetermined pattern so as to form a plurality of
sealed, isolated, chambers and ventricles and fluid flow paths
there between. The fluid flow paths include a recirculating blood
circuit including tubular segments A, B and C leading through a
blood ventricle 50 and tubular segment E to a blood input end of a
dialyzer member 38 (FIG. 8). The dialyzer member 38 preferably
consists of a tubular outer casing 40 that is sealed between the
double layers of flexible plastic that are RF sealed to one
another. The soft or hard casing 40 is fluid impermeable and
contains within it a large plurality of hollow tubular dialysis
fibers configured as a bundle. More particularly, the dialyzer 38
may be a miniature version of a commercially-available
conventional, hollow fiber dialyzer and the hollow dialysis fibers
used therein typically have an internal diameter of between 200 and
400 .mu.m, allowing a high number of fibers to be contained within
the tubular casing 40. The casing 40 may have an outside diameter
of about 1/3 inch.
[0039] As is known in the art, the dialysis fibers comprise
semi-permeable membranes, typically composed of cellulose or
polymeric directives. A pair of miniature dialyzers like that
contemplated may, together, provide a generous total exchange
surface of about 1000-1500 square centimeters (0.1-0.15 square
meters). A suitable manifold of known construction is provided so
that arterial blood flowing into the dialyzer 38, via the tubular
branches A, B and C and the blood ventricle 50 in FIG. 8, is made
to flow through the central lumens of the bundled tubular fibers in
a first flow direction, while dialysate solution is made to flow in
a predetermined direction, preferably the counter current
direction, through the dialyzer casing 40 such that the outer
surfaces of the tubular fibers are bathed effectively by the
dialysis fluid.
[0040] Blood exits the dialyzer member 38 via a tubular path
segment D defined between the superposed sheets of plastic
comprising the upper disposable member 14. The manner in which a
patient's blood is accessed will be described in greater detail
herein below.
[0041] With continued reference to FIG. 8, the RF welded, laminated
plastic sheets comprising the disposable member 14 further includes
a dialysate circuit having a flexible compressible and expandable
dialysate ventricle 42 that projects from the undersurface of the
member 14 and is shown in phantom line in FIG. 8. This ventricle is
in fluid communication with a tubular conduit comprising segment E
leading from a dialysate outlet port 44 of the dialyzer and an
inflow path of the dialysate rejuvenating cartridge ending at inlet
port 47 of the cartridge and including auxiliary pumping valves
131, 129 and 127 and the two auxiliary pumping ventricles 117, 115
there between. Tubular segments H and G lead from an outlet port 48
of the dialysate rejuvenating cartridge 24/26 back to inlet port 46
of the dialyzer, completing the dialysate circuit. A recirculation
circuit L may be opened when auxiliary dialysate pumps 117, 115,
131, 129, 127 are employed, to avoid negative pressure.
[0042] Disposed in segment C of the blood path of the upper
disposable member 14 on its undersurface is an expansible blood
ventricle 50 which serves to displace a pump actuating lever 53
(FIGS. 2 and 9) in a manner to be explained in greater detail
below. Also cooperating with the pump actuating lever 53 is the
expansible dialysate bladder 42.
[0043] A reservoir 52 formed by selective welding of the sheets
comprising disposable member 14 is configured to contain a suitable
anti-coagulant, e.g., heparin, possibly guarded in a crushable
ampule, and it is adapted to feed the anti-coagulant via tubing
segment K to the bloodstream just proximate the interior of the tip
of the arterial cannula (not shown) used to access the patient's
circulatory system. As will be explained further herein below, the
anti-coagulant is metered out from the reservoir by a peristaltic
pump driven by the patient's own arterial/venous pressure
differential and serves to prevent clotting of blood within the
cannula needle entry and throughout the device, while avoiding
undesirable systemic delivery of the anti-coagulant.
[0044] A bladder 54 formed in the upper disposable between its
laminated sheets is adapted to contain a calcium magnesium (CaMg)
solution, also possibly guarded in a crushable ampule, that is
added to the cleansed dialysate via tubular segments I and J
leading to the dialyzer dialysate inflow port 46.
[0045] As is explained in fuller detail below, the CaMg aqueous
solution helps rejuvenate the dialysate solution after it passes
through the toxin removing sorbent cartridge 24/26.
[0046] Connected in series with the dialysate ventricle 42 are
passive check valves 56 and 58 which selectively open and close to
permit emptying and filling of the dialysate ventricle as the pump
lever 53 presses upon or retreats from its contact with ventricle
42.
[0047] The lower disposable member 18 shown in FIGS. 1, 2 and 7 is
a substantial duplicate of the upper cuff member 14. It includes a
blood circuit containing a second dialyzer 38' and an expandable
blood ventricle 50', connected by tubing to dialyzer 38' and to a
venous cannula (not shown) connected to tubing segment D'. Lower
disposable member 18 also includes a dialysate circuit, an
anti-coagulant circuit path and a CaMg circuit path arranged to be
functionally but, in the case of the anti-coagulant and CaMg
conduits, not precisely topographically congruent to be
corresponding circuits on the disposable cuff member 14.
[0048] As seen in the exploded view of FIG. 2, disposed between the
upper and lower cuff members 14 and 18 is a non-disposable pump
frame member 16, which is preferably injection-molded from a
suitable plastic. It is seen to comprise a generally rectangular
block of a predetermined length, width and depth dimension that
includes a centrally disposed somewhat rectangular opening 62
defined by left and right side members, 64 and 66, and front 68 and
rear 70 end members. Pivotally mounted within the central
rectangular opening 62 is the swingable lever plate pump actuating
lever 53. More particularly, and as can be seen in FIGS. 2 and 9,
the frame member 16 includes left and right rectangular openings 74
and 76 and disposed within those openings are roller pump
assemblies 78 and 80 that are journaled for rotation on shaft 84
which also serves to hingedly connect the swinging lever plate 53
to the opposed side edges 64 and 66 of the frame member 16. The
conventional roller cages 78 and 80 each comprise a toroid of
circular cross-section 81 that is formed from a metal or suitable
plastic and which includes a plurality of regularly spaced axially
extending grooves or slots in which are loosely retained wire-like
rollers, as at 86, that extend across the width dimension of the
roller cage 81. The rollers are driven to roll about high friction
tape coated metal spools 83, but the rollers progress at only 1/2
the speed of the surface of the spools because the rollers rotate
in the opposite direction from the rotation of the spools.
[0049] Secured to a side surface of the spools 83 are annular
ratchet gears 88 and 90. Referring still to FIG. 9, there is shown
mounted on the lever plate 53 and cooperating with the teeth on the
ratchet gear 88 a rotation motivating pawl 95. Likewise, a reverse
rotation-preventing pawl 94 is affixed to the end wall 70 of the
frame 16 and is cantilevered so that its free end engages the
ratchet teeth on the ratchet gear. With the described arrangement,
as the lever plate 53 is made to pivot downward (clockwise) about
the shaft 84, the associated spool 83 (ratchet 88) will be made to
rotate in the same direction.
[0050] As the lever plate is made to pivot in the upward
counterclockwise direction when viewed in FIG. 9, the rotation
motivating pawl 92 will engage the ratchet teeth on the spool
associated with the roller cage assembly 80 to rotate that roller
cage in a counterclockwise direction. Reverse rotation will be
prevented by pawl 97 attached to frame end 70. The rollers 86,
however, will rotate clockwise around their own axes.
[0051] As the rollers 86 rotate about the spools 83, they are
pressed against RF sealed conduits disposed in the roller races 96
and 98 (FIG. 6) formed in the top and bottom plates 12 and 20 to
effectively form peristaltic roller pumps for the anti-coagulant
and CaMg and possibly other solutions. With continued reference to
FIG. 9, first and second bores 100 and 102 are formed through the
thickness dimensions of the frame plate side walls 64 and 66 and
loosely fitted into these bores are conduit occluders 104 and 106
which may comprise cylindrically-shaped permanent magnets. The
occluders are dimensioned to slide freely within their respective
bores 100 and 102 under influence of electromagnets 30 and 34.
Likewise, similar bores 108 and 110 are formed through the
thickness dimensions of the frame pump end walls 68 and, again,
slidable permanent magnet occluders 112 and 114 are insertable
within the respective bores 108 and 110 to be acted upon by
electromagnets 32 and 36 to function as pump bladder compressors
for auxiliary dialysate pump ventricles 115 and 117 in FIG. 8.
[0052] Also formed in the upper and lower surfaces of the side
walls 64 and 66 and front wall 68 and top and bottom end plates 12
and 20 are somewhat circular depressions as at 116-124 in FIG. 6
which are aligned with similar recesses 126-134 on frame member 16
in FIG. 9 and complementary recesses on the underside of top plate
12 when assembled as shown in FIG. 1. These recesses contain
passive check valves (poppet or flap), as at 56 and 58, in FIG. 8
and 56' and 58' in FIG. 7. Poppets 56', 58', 56, 58 are seen in
FIG. 2. Referring again to FIG. 2, the frame member 16 is
sandwiched between the upper and lower disposable cuff members 14
and 18 such that the blood ventricles 50 and 50' are positioned on
opposite sides of the lever plate 53 and displaced a predetermined
distance from the axis of the shaft 84 and of the roller cages 81.
Similarly, the dialysate ventricles 42 and 42' are also on opposite
sides of the lever plate 53. Even though the dialysate conduits are
shown as positioned closer to the fulcrum 84 of lever 53, the
dialysate ventricles might be placed at an equal or greater
distance from the fulcrum than the blood bladders by curving the
conduits or by displacing the centers of the dialysate ventricles,
nearer to the thinner edge of the lever plate. This would make it
even more unlikely for a higher pressure to be generated in the
dialysate circuit compared with that in the driving blood circuit,
further preventing dialysate from entering the bloodstream.
[0053] The tubular passageways leading from the anticoagulant
reservoirs 52 and 52' and the CaMg reservoirs 54 and 54' are
located to cooperate with pump assemblies 78 and 80 so as to
function as peristaltic roller pumps. That is to say, as the roller
pumps 78 and 80 are driven by the pivoting action of the lever
plate 53 in the manner already described, the rollers three
measured proportional quantities of an anti-coagulant and CaMg
solution from their respective reservoirs 52, 52' and 54, 54' and
along conduits leading to the arterial cannula or in to the
cleansed dialysate conduits.
[0054] The permanent magnets occluders 104 and 106 serve as conduit
occluders and function to open and close the lumens of the blood
flow circuit C and C' to allow the arterial/venous pressure
differential to alternatively fill and empty the blood pump
ventricles 50 and 50' under influence of electromagnets 30 and 34
carried by the upper and lower end plates 12 and 20. As will be
later explained, the electromagnets are operated in time phase and
spatial polarity oriented equality, both North poles to the left
and both South poles to the right, or visa versa. That is to say,
when electromagnets 30-34 are pulsed, they function to
cooperatively, directionally, attract and repel the North and South
poles of each permanent magnet 104 and 106 to cooperatively move
the conduit occluder upward or downward. The two conduit occluder
permanent magnets' poles being identically oriented and under the
influence of the opposite ends of the identically oriented
electromagnets, the permanent magnets are moved in opposite
directions in order to position them to block the flow of blood
into the first bladder 50 and out of the second 50'.
[0055] Subsequently, with current reversal, the permanent magnets
occluders 104 and 106 are attracted and repelled in the opposite
directions with regard to near contact with the corresponding
points on the others of the four blood conduits, blocking the flow
of blood out of the first bladder 50 and into the second 50'.
[0056] Small, linear plastic knife edges (not shown) may be affixed
to the RF sealed disposable precisely over the conduits that are
meant to be occluded for blood cycling function. Affixing knife
edges to the disposable is superior to having them be part of the
permanent magnet occluders because positioning is thereby perfect
every time and not dependent on positioning of the whole RF
disposable between the frame 16 and the upper and lower end
plates.
[0057] The wrist and forearm-wearable artificial kidney, as
depicted in FIG. 1, is sufficiently small and light in weight to be
unobtrusively worn 24 hours a day, 168 hours a week. VELCRO
fasteners on the laterally projecting tabs 116 and 118 of the
blood-contacting disposables of FIGS. 7 and 8 help to hold the
device firmly in place on the forearm and wrist of the patient. It
is also contemplated that a custom-molded porous foam "second skin"
may be disposed between the base member 22 and the wearer's forearm
to provide increased comfort and to assure that the graft
compressors fastened to the second skin will remain precisely
positioned over the subcutaneous graft.
[0058] The disposable cuffs 14 and 18 are sealed while there is
some air pressure within or suction without, to assure that the
sealed in ducts conduits tend toward having open circular lumens
and do not collapse and stick together, plastic sheet to plastic
sheet, when not distended by a contained liquid.
[0059] The device of the present invention operates to
meter-modulate blood flow at a certain rate which automatically
coordinates proportionally with the heparin anticoagulant
administration, a heparin administration that is plentiful for
preventing clotting within the device, but insufficient to result
in systemic (total body) anticoagulation. Desirable prophylactic
anticoagulation of the body does result.
[0060] Blood cleansing requirements must be considered as well.
About 20-30 ml/min of blood flow through the device, 168 hours a
week, will serve generously for the dialysis task. Dialysate is not
only being modulated, but also pumped, secondarily, by the blood
pressure differential. In this case, there is a proportional,
approximately equal, countercurrent blood and dialysate flow.
Proportionality also applies to added CaMg, which is required to
reconstitute these two substances that have been completely
stripped from the dialysate during one pass through the adsorbent
cartridge. Since it is all gone, it can be wholly, proportionally,
replaced into the dialysate flow with confidence.
[0061] Potassium is also stripped from the dialysate by the
adsorbent cartridge 24/26 but it usually exists in excess, or at
least in abundance, in uremic and other severely challenged
patients. So, depending on lab findings, K.sup.+ may be
aggressively removed by adding no potassium in to the dialysate, it
might be drawn down slowly by including a normal small amount of K+
in the dialysate or it might actually be replaced if too much has
been removed. It is anticipated that the very safe second option
will be utilized most often in chronic, non-traumatic patients who
will thus remain within normal limits without much manipulation. In
the system we are describing, there is of course no exogenous
dialysate replacement and cartridges with different K+ scrubbing
capabilities will be utilized per the physician's prescription.
[0062] The inflow and outflow of dialysate from its pump ventricles
can be directed either by one-way passive check valves that are
located in the dialysate circuits at a physical position wherein
the check valves will reside in the depressions 126-134 (FIG. 9) on
the upper and lower surfaces of the frame member 16, or
alternatively, active magnetic valves, as described for the blood
circuits, may be so located. The check valve locations on the upper
disposable cuff member 14 and associated with the dialysate circuit
are identified by numerals 56, 58, 127, 129 and 131 that determine
the allowed direction of flow of liquid through the respective
circuits. Passive check valves may consist of thin washers with
either poppets or flaps situated to permit flow in only the desired
direction. The washers are RF sealed and compressed within the
disposable and the conduit grooves are inscribed in the hardware to
allow the fluid to approach the hole in the washer only on one side
and to depart the hole only on the other.
[0063] The direction of flow of the DC current supplied by battery
28, hence the polarity of the horizontal electromagnets 30 and 34
should be reversed about every 5-15 seconds. Preferably located
near the apex (tip) or side of the lever plate 53 is a small
permanent magnet 133 (FIG. 9) which cooperates with a Hall sensor
(or a bi-directional, current reversing reed switch mounted in the
front member 68 or side member of the pump frame plate 16. As the
magnet 133 sweeps past the Hall sensor, it causes the Hall sensor
to reverse the direction of the next upcoming electrical trigger
signal to an electronic circuit of FIG. 10, which functions to
drive the electromagnets 30-34 at predetermined time intervals.
[0064] Referring to FIG. 10, the electronic circuit is powered by a
battery 28 and may preferably comprise a Type 556 dual-timer
integrated circuit chip that when triggered by an input signal on
pin 6 thereof causes an output signal at pin 5 that will energize
the electromagnets at a predetermined time, e.g., every 5-15
seconds. Later on, after the lever plate 53 carrying the magnet 133
has swept past the Hall sensor and reversed the circuitry, a
trigger input will be applied to pin 8 of the Type 556 IC chip, now
causing an output current at pin 9 to flow through the
electromagnets 30 and 34 to energize them for a predetermined brief
period of time established by the RC timing elements employed. As
already mentioned, the permanent magnets 104 and 106 are attracted
in opposite directions spatially against electromagnets 30 or 34,
depending upon the relations between the alternating poles of the
electromagnets and the permanent poles of the permanent magnets. As
will be seen subsequently, electromagnets 32 and 36 are programmed
identically, but timed differently to perform two stage, rapid
pulse auxiliary pumping of the dialysate through the cartridge
24/26 utilizing permanent magnets 112, 114 in cylindrical bores
108, 110 to alternately compress ventricles sealed between valves
127, 129, 131 and 12T, 129' and 131' in the RF sealed disposables
of FIGS. 7 and 8.
[0065] In preparing a patient for use of the wearable hemodialyzer
of the present invention, a conventional, plastic tube
arteriovenous fistula graft can be surgically implanted in the
patient's forearm or, alternatively, and perhaps preferably, an in
situ debranched vein fistula graft may be surgically created by
anastomosing an artery to the debranched vein as seen in FIG. 4.
Retaining its natural (vaso vasorum) blood supply, lymph drainage
and nervous and elastic surround, the vein fistula graft is
expected to remain especially resilient, particularly to the small
cannulae required for the target 20-30 ml/min flow. In creating the
in situ fistula graft, vein branchings can be ligated or stapled
via minimal skin incisions, while the fistula anastomosis is being
performed or subsequently in an already established fistula. Swift
arterial run-offis thereby established in a single subcutaneous
vein, much like correcting for downstream vein complex
malfunctioning in conventional AV fistulae. When periodically
compressed, the vein fistula graft repeatedly harbors arterial
pressure on one side of the compression and venous pressure on the
other. The sites of compression are preferably alternated acutely
and shifted chronically in order to prevent surrounding tissue
necrosis and intimal abrasion. In FIG. 14, numeral 135 identifies
the radial artery and 137, the intermediate antebrachial vein that
are anastomosed at 139.
[0066] When the fistula graft is compressed at a predetermined
location thereon, the portion of the graft proximal of the
compression site will be at arterial pressure and the portion of
the graft distal of the compression site will be at venous
pressure. When the compression is released, the whole fistula graft
will be at approximately venous pressure.
[0067] As best seen in FIG. 1, the tubing segments A and A' from
the upper and lower disposables 14 and 18 join together and are
adapted to connect to a commercially-available double lumen needle
cannula, such as available from CR Bard Corporation. The needle
cannula connected to tubular segments A and A' will be inserted
into the fistula graft at a location between the arterial
anastomosis and the point where compression is applied to
temporarily occlude the fistula graft. In a similar fashion,
tubular segments D and D' on the upper and lower RF welded
disposables 14 and 20 are brought together and terminate with a
needle cannula that is adapted to be inserted percutaneously into
the fistula graft at a location downstream of the compression
point. Tubular segments K and K' that lead from the anticoagulant
reservoirs 52 and 52' are joined and brought in through a hub on
the arterial cannula such that the anti-coagulant will be slowly
injected directly inside the tip of the inflow arterial cannula,
via its second small lumen. The anticoagulant administration is
proportional and appropriate for the quantity of blood flowing
through the device, anticoagulating that peripheral blood flow
therapeutically, while the patient is no more than prophylactically
anticoagulated to a low, safe level.
[0068] The disposable, blood-contacting RF welded members 14 and 18
are preferably designed to be replaced at 31/2 day intervals to
inhibit infection and, more importantly, to replenish the supply of
anticoagulant and calcium magnesium solution. Removal of the
cannulae at 31/2 day intervals should allow the in situ graft
tissues to heal rapidly and without complication.
[0069] The tabs 116 and 118 of the disposables are adapted to be
wrapped around the forearm and adhered to each other with Velcro
fasteners thereon, thereby accommodating considerable variations in
patients' anatomy. Offsets in mounted height between the two
disposables assure that the dialyzers, anticoagulant and calcium
magnesium reservoirs and other components will not directly overly
each other, rather will nestle side-by-side, resulting in the least
obtrusive space occupied around the forearm.
[0070] As shown in FIGS. 3 and 4, which illustrate the preferred
embodiment when viewed from the patient's perspective on his/her
left forearm and wrist 23, the urease and adsorbent cartridge 24/26
is adapted to slide onto the base member 22 in guide slots 25. The
cartridges include quick-release clips 27 on opposed sides with
integral hinges 29 to hold them in place. The several sized
cartridges may be replaced every two or four hours during daytime
while a larger capacity cartridge (pictured) lasting, say, eight
hours may be used for nighttime application. The smaller-sized
cartridges are less intrusive as far as a subject's wrist motion is
concerned.
[0071] As can be seen in FIG. 2, the cartridge segments 24 and 26
include a central vertical divider 25 and a central horizontal
divider 27 that divide the cartridge into two upper channels and
two lower channels, the two upper channels and two lower channels
being continuous, respectively, through upper and lower holes in
the central vertical divider that are in line/with holes 125 in the
opposed sides of the cartridge. Each of the compartments is loaded
with layered urease, zirconium phosphate, hydrous zirconium oxide
and activated carbon or their functional equivalent. Dialysate
exiting the dialyzer 38 at port 44 travels through conduit segment
E through the check valves 56, 68, 131, 129 and 127 to enter the
upper left quadrant of the cartridge 24/26 at port 47 and returning
via the upper right quadrant to enter the port 48 of the upper
disposable where it then travels through conduit segment H and to
the dialysate inlet port 46 of the cartridge 38. In a similar
fashion, dialysate traversing the lower disposable member 18 flows
through the lower left quadrant of the cartridge 24/26 and back
through the lower right quadrant of the cartridge from the outlet
ports 47' and inlet port 48' of the disposable. Any concern over
how to prevent the cartridges from being inadvertently used beyond
their specified time limits and eventually spilling ammonia can be
resolved in a number of ways. For example, specific interlocks
might initiate a timer which would alert the patient with an
audible or vibratory signal. Alternatively an ameroid, which is a
plastic material that swells over time in an aqueous medium, could
be included in the flow path of each cartridge in the form of a
small sphere that would occlude the duct from within around the
time that the cartridge would be expected to become exhausted.
[0072] A thin elastic bladder-like container (not shown) can be
stretched over the cartridge to encompass the outlet ports 125 to
both contain necessary dialysate to fill the circuit and to permit
excess dialysate to collect around the cartridge until it can be
emptied in an appropriate facility. It is also contemplated that a
bedside suction pump and limited sized collection bag in a vacuum
chamber can be utilized to assist the removal of a predetermined,
limited, volume of excess fluid while the patient is asleep.
[0073] The top end plate 12 and the bottom end plate 20 each have a
pattern of grooves formed inward that when placed in registration
with the frame member 16 create channels for receiving segments of
the fluid carrying conduits on the upper and lower RF sealed
disposables 14 and 18 without distorting, i.e., closing the fluid
flow paths. FIG. 6 clearly shows the groove pattern on the upper
surface of the bottom end plate 20 and this pattern is replicated
on the lower surface of the top end plate 12.
[0074] The lower RF sealed blood contacting disposable 18 differs
from the upper one 14 in only two small ways. The lower disposable
18 has its parallel anticoagulant and CaMg ducts located more to
the left while the corresponding ducts on the upper disposable 14
are more to the right when viewed in FIGS. 7 and 8. This difference
is to accommodate their being acted upon by the left-hand roller
pump 78 in the case of the lower disposable 18 and by the
right-hand roller pump 80 in the case of the upper disposable 14.
In this fashion, anticoagulant from the reservoirs 52 and 52' is
propelled toward the tip of the arterial cannula and CaMg from the
reservoirs 54 and 54' toward the dialysate inflows of the dialyzers
38 and 38'. Another slight difference results from the two
disposables occupying mirror image locations in the composite
device. The blood and major dialysate ventricles 50, 50' and 42, 42
protrude toward the center and into the opening 62 of the frame
member 16. In that they protrude from opposite directions, they
interact with the lever 53 that lies between them. The opposite
side of each major ventricle is supported by the flat surfaces of
the top and bottom end plates 12 and 20 preventing bulging of the
ventricles in a direction other than toward the center of the
device.
Operation
[0075] Having described the mechanical construction of the
continuously wearable hemodialyzer comprising a preferred
embodiment, consideration will next be given to its mode of
operation. In this regard, let it be assumed that a cycle has just
been completed in which arterial engorgement of the ventricle 50 on
the upper disposable 14 has driven the lever 53 to its lowermost
disposition within the frame 16. The electronic control circuit of
FIG. 10 outputs a pulse to activate a means, such as a motor-driven
pair of spaced-apart cams mounted on the opposite (volar) side of
the forearm on which the hemodialyzer 10 is mounted. The cam is
positioned so as to compress the fistula graft to thereby establish
an arterial/venous pressure differential in the graft. Rather than
a motor driven cam for applying compression to the fistula graft at
locations 17 and 19 in FIG. 14, a pair of solenoids or plungers
driven by a CO.sub.2 cartridge might also be used.
[0076] At this time, the permanent magnet 104 (FIG. 9) is being
attracted to the lower electromagnet 34 while the permanent magnet
106 is being repelled by it. The movement of the permanent magnet
104 against a knife edge on conduit segment C' on the lower
disposable 18 results in a filling of the lower blood ventricle
50'. At the same time, the permanent magnet 106 is being attracted
by the electromagnet 30 against the inflow C of the upper blood
ventricle 50 while the outflow therefrom has become unoccluded.
[0077] As a result, the lever plate 53 is driven upward as the
blood ventricle 50' is being filled with blood under arterial
pressure. The movement of the lever plate against the upper blood
ventricle 50 directs its blood through the upper dialyzer 38 and
back into the downstream segment of the fistula graft which is at a
venous pressure. At the same time, the contents of the upper
dialysate ventricle 42 is squeezed out to flow through the one-way
valves 58, 131, 129 and 127 and into the upper left quadrant of
cartridge 24/26.
[0078] As the lever plate 53 rises, it drives one of the roller
pumps 80 to cause anti-coagulant to be injected into the tip of the
arterial catheter and CaMg solution into the inflow of the dialyzer
38, respectively.
[0079] Also, as the lever plate 53 is driven upward, the Hall
sensor in the frame 16 senses the passage of a small permanent
magnet mounted to the lever plate causing a reversal in the
polarity of the electromagnets preliminary to a subsequent pass of
the lever plate 53 in a downward direction.
[0080] A DC electrical impulse from the control circuit of FIG. 10,
at the same or multiple interval, results in the application of
pressure to the fistula graft at a location offset from the
previous point of compression. With the subcutaneous fistula graft
again compressed, arterial/venous pressure differential is again
created in the graft. The reversal of polarity of the permanent
magnets results in a blocking of the outflow from the blood
ventricle 50 of the upper disposable member of FIG. 8 while the
inflow to the blood ventricle 50' on the lower disposable member of
FIG. 7 becomes occluded. Thus, as the upper blood ventricle 50 is
filling due to arterial pressure, it drives the lever plate 53
downward to squeeze blood from the ventricle 50' of the lower
disposable 18 and back into the venous segment of the subcutaneous
graft and to empty the dialysate solution from bladder 42' through
the lower quadrants of the cartridge 24/26.
[0081] The downward movement of the lever plate 53 results in
rotation of the opposite roller pump 78, causing anticoagulant to
be injected into the tip of the arterial catheter and CaMg into the
inflow of the lower dialyzer.
[0082] The downward movement of the lever plate is again sensed by
the Hall sensor of the control circuit of FIG. 10 to reverse the
polarity of the electromagnets and the cycle again repeats with the
lever plate 53 again being driven in an upward direction.
[0083] It can be seen that the apparatus of the present invention
disclosed in FIGS. 1-10 hereof and its mode of operation provide
modulated active arterial-venous primary blood flow and secondary
dialysate, anticoagulant and CaMg pumping utilizing the patient's
own arterial/venous blood pressure differential to achieve
continuous dialysis treatment in patients having failed kidney
function. Dangerous mechanical pumps are avoided. Regional
anticoagulation of the relatively small amount of blood flowing
through the extracorporeal circuit inhibits clotting therein, but
does not significantly depress systemic hemostasis, and avoids the
need for dangerous anticoagulant reversing agents.
Alternative Embodiments
[0084] While the kidney dialysis design described above features
both upper and lower RF sealed disposables as well as
electromagnets arrayed both above and below, some advantage might
be gained from eliminating the lower disposable and the lower
electromagnets. Coil or other spring return would be substituted
and as a result, not only would a considerable component-expense be
eliminated, there would also be the opportunity to slim the profile
of the system on the arm.
[0085] With only minor revisions to the disposable, flexible
plastic, blood-contacting members illustrated in FIGS. 7 and 8, the
device of the present invention may be adapted to function as an
artificial liver until a suitable transplant becomes available, or,
indeed, if none ever is found.
[0086] Referring to FIG. 11, it shows the configuration of the
upper and lower disposables that are substituted for those of FIGS.
7 and 8 in implementing an artificial liver. Like the artificial
kidney previously described, the upper and lower disposables differ
in the location of the tubing segments A and A' with the tubing
segment on the upper disposable A located so as to be operated upon
by the caged roller assembly 80 of FIG. 9 and the tubing segment of
the lower disposable A' operated upon by the cage roller assembly
78 in FIG. 9. Unlike the artificial kidney, where A and A' join
together to inject anticoagulant almost continuously into the
patient's arterial cannula which is located at the top of the
kidney drawing of FIG. 7, in the liver embodiment of FIG. 11,
tubing segment A is shown being directed at the canine arterial
cannula and tubing segment A is directed at the patient's arterial
cannula.
[0087] Also unlike and in reverse from the kidney, the patient's
arterial blood pressure containing ventricles 226, 226' and
associated electromagnets and permanent magnet occluders are
located closer to the fulcrum 84 of the swinging lever 53 than are
the dog's ventricles 208, 208' and their passive check valves. This
constitutes one of several strategies employed to assure that the
dog's blood can never achieve a higher pressure than the patient's
blood. One would wish to assure that there can never be
contamination of the patient with dog's blood, even in case of a
broken fiber. One would thereby avoid any likelihood of a patient
vs. dog's blood allergic reaction. Other features employed in the
artificial liver embodiment toward the same purpose of assuring
that dog's blood is unlikely to ever contaminate patient's blood
include: utilizing only veno venous cannulation of the dog's
fistula graft without compression-arterialization. While the dog's
blood ventricles 208, 208' are now located further from the fulcrum
84, they are capable of pumping their circuits, the dog's
ventricles filling pressure being supplied by attaching the
artificial liver apparatus onto the dog's harness where the dog's
venous pressure (and gravity) can distend those relaxed
ventricles.
[0088] The dog has been provided a compressible, but in this case
non-compressed, arterial venous fistula graft in a pedicle of skin
around the back of the neck that is adapted to be accessed by
needle cannulae (not shown) coupled to the tubing segment 202' so
that blood can be made to flow through a future antigen filter 204'
and the tubing segment B' formed between the RF welded layers
comprising the disposable 200' The tubing segment B' is shown as
leading to a first passive check valve 206', a dog's blood
inflatable ventricle 208' and a second passive check valve 210''
connected by tubing segment C' to an inlet of an exchanger 212'
similar in construction to the dialyzer 38 of the kidney embodiment
in that it contains a large plurality of tubules comprising
semi-permeable membranes. Appropriate manifolds are provided on
that the dog's blood entering the exchanger 212' from the tubing
segment C' is made to flow through the plurality of lumens of the
tubules before exiting the exchanger via tubing segment D'' that
leads to a needle cannula (not shown) in the fistula graft
preferably located in the dog's neck.
[0089] Plastic tubing 214' connects to a needle-cannula (not shown)
insertable into an arterial venous fistula graft in the patient's
arm and connects to a tubing segment E' formed in the disposable
200'. Connected in series with tubing segment E' are one-way valves
216', 218' and 220' which, together with compressible bladders 222'
and 224', form an auxiliary pump for possibly moving patient's
arterial blood through a tubing segment F' to a patient's blood
ventricle 226', still another way to assure that the patient's
blood will be at a higher pressure than the animal's. The
inflatable, compressible ventricle 226' is then connected via
tubing segment G' formed in the disposable 200' leading to the
patient's blood inlet 213' of the membrane exchanger 212'. The
patient's blood flows over the outer surface of the tubules through
which the dog's blood is made to pass.
[0090] The patient's blood exits the exchanger 212' by way of a
tubing segment H' that is traceable back to an external plastic
tube 228' leading to a needle cannula insertable into the fistula
graft, downstream from the patient's fistula graft compressors, at
a point exposed to venous pressure.
[0091] Formed between the layers comprising the laminated structure
of the disposable 200' is a reservoir 230' that contains an
anticoagulant, such as heparin, possibly preserved in a crushable
ampule. The pumping action afforded by inflation and deflation of
the ventricles 226, 226' acting on the lever plate 53 and the
roller pumps (FIG. 9) measures out metered quantities of heparin,
via tubing segments A and A' (A segment being on the upper
disposable and segment A' being on the lower disposable), A' leads
from the lower disposable to the cannula placed in the dog's
fistula graft. Flexible tube A leads back from the upper disposable
and joins the needle cannula insertable in the arterial portion of
the patient's fistula graft.
[0092] Recalling from the description of the artificial kidney
embodiment how the non-disposable pump structure cooperates with
the upper and lower disposable members through appropriate
energization of the electromagnets. The human blood inflow occluder
(not shown) related to patient's ventricle 226 on the upper liver
disposable is made to open while the (identical) human blood inflow
occluder on the lower disposable becomes closed. Simultaneously,
the human blood outflow occluder (not shown) on the upper
disposable becomes closed while the (identical) human blood outflow
occluder on the lower disposable becomes open. The upper human
blood ventricle 226, therefore, begins to fill and to displace the
lever plate 53 downward to press against the corresponding human
blood ventricle 226', emptying both it and the lower dog's blood
ventricle 208' via passive in and out check valves 206' and 210'.
The dog's blood is emptied through the fibers of dialyzer 212' via
tubing segment D'.
[0093] As the lever plate 53 is driven downward, it presses on the
patient's blood ventricle 226' forcing the patient's blood through
the tubing segment G', and, after bathing the outside of the fibers
in the dialyzer 212', out through the tubing segment H'. Slightly
less efficient cocurrent flow is accepted in this case (instead of
counter current flow as in the kidney embodiment) as a necessary
part of the transcendent strategy to, as much as possible, maintain
a higher pressure on the patient's side compared with the dog's
side. Toxins present in the patient's blood pass in through the
membrane walls of the hollow fibers contained within the exchanger
212' to the dog's blood and are ultimately removed therefrom by the
dog's functioning liver.
[0094] Similar to the case of the kidney embodiment, movement of
the pump's lever plate down drives the roller pump assembly 78 in a
direction to move anticoagulant from the reservoir 230' to the
dog's cannula via tubing segment A'. Lever plate movement upward
drives anticoagulant by means of roller pump assembly 80 from
reservoir 230 of the upper disposable on through tubing segment A
and into the patient's arterial cannula.
[0095] As has already been explained in connection with the
artificial kidney embodiment, as the lever plate 53 is driven in
one direction or the other by the filling of the human blood
ventricles on the upper or lower disposables, a Hall sensor affixed
to the frame senses the passage of a permanent magnet affixed to
the lever plate and sends a signal to the electronic circuitry of
FIG. 10 to cause a reversal in the potential polarity of the
electromagnets, resulting in a shift in the filling of the human
blood ventricles from the lower to the upper disposable or from the
upper to the lower disposable after the next pulse of direct
current.
[0096] FIG. 12 illustrates how the layout of the upper and lower
disposable, blood-contacting members can be changed from that shown
in FIGS. 7 and 8 where the apparatus of the present invention is to
be used in treating congestive heart failure (CHF). CHF implies a
weakening of the heart, resulting in "congestion" or backing up of
blood waiting to be pumped through the lungs and around the body.
Weakening of the heart might be caused by a number of immediate and
remote causes. It affects nearly 5 million patients in the U.S.
alone. The result in each case is that the venous pool enlarges and
tissues become "water-logged". For example, ankles swell and lungs
exchange gases poorly--the classical "Dropsy". A number of medical
treatments have been attempted, mostly aimed at either
strengthening the heart's pumping or otherwise stimulating the
kidneys to more effectively remove water from the circulation.
[0097] Often when medical or surgical efforts fail, patients die
miserably of suffocation. A variety of ancillary pathologies might
intervene, e.g., pneumonia. Therefore, cardiologists stealing from
the nephrologists' playbook have begun intermittently
"hemodiafiltering" or "hemofiltering" patients of watery solvent.
This is preformed by means of either conventional hemodialysis
machines or with what are, to most intents and purposes, dialysis
machines retaining most of the capabilities but lacking the
capacity to carry out solute exchange. The emphasis, rather, is on
squeezing fluid out of blood through a semi-permeable membrane
acting as a sieve. Cardiologists typically carry out such
hemofiltrations at intervals suited to the individual, and they
typically may remove several liters of fluid from the bloodstream
and eventually from the tissues within a few hours time. This is a
strenuous procedure for both patients and staff and predicatively
yields limited and temporary benefits.
[0098] It would, therefore, be desirable for such hemofiltration to
be carried out slowly and continuously and with much greater
effect. Nearly identical apparatus as depicted in FIGS. 1-10 may,
therefore, be utilized for continuous 24/7 ambulatory
hemofiltration and with an even larger element of suction being
utilized during recumbent night time periods to draw liquid out of
the blood during sleeping hours. Referring to FIG. 12, there is
shown one of the two blood-contacting, flexible plastic disposables
indicated generally by numeral 300'. It has a reservoir 302' for
containing a volume of an anticoagulant, perhaps in a crushable
ampule for storage, that is connected by way of a tubular channel
A' to a cannula 304 adapted to be inserted into a subcutaneous
arterial venous fistula graft or, as in the case of the other
previously described embodiments, into an In Situ Debranched Vein
Fistula Graft (VFG) upstream of a graft compression site. A second
cannula 306 is connected to a tubular passage B' formed between the
two layers of laminated plastic comprising the disposable 300'.
Arterial blood is made to flow through a dialyzing cartridge 308'
supported on the disposable 300' so as to flow through the large
plurality of tubules contained within the dialyzer 308'.
[0099] As with the earlier described embodiments, under control of
magnetically-actuated occluders, blood is made to fill and empty
from an expandable ventricle 314'. Excess water in the blood passes
through the walls of the semi-permeable membranes comprising the
tubules within the cartridge 308' and are allowed to flow through
tubing segment C' to a common collection bag 316.
[0100] As the reader will understand from the previously described
embodiments, permanent magnet occluders attracted and repelled by
electromagnets selectively occlude and unocclude the ducts leading
to and from the two blood ventricles 314 and 314' on the
corresponding upper and lower disposables. Physically, the lower
and upper disposables differ only in the location of the tubular
segments identified as D' and D where segment D' is on the lower
disposable and segment D is on the upper disposable.
[0101] When the lower and upper disposables are positioned as shown
in the exploded view of FIG. 2, one of the cage roller assemblies
78 or 80 will cooperate with segment D' and the other with the
segment D. The blood expandable ventricle 314', when filling,
serves to displace the lever plate 53 so as to press against the
corresponding ventricle on the upper disposable member causing it
to empty while, at the same time, rotating one of the roller pump
assemblies in a direction to pump anti-coagulant, possibly
contained for storage in a sealed in crushable ampule, from the
reservoir 302'. When the associated electromagnets reverse
polarity, the blood expandable bladder on the upper disposable
begins to fill, moving the lever plate 53 downward to compress and
empty the ventricle 314' and, at the same time, peristalticly
pumping anticoagulant from the reservoir on the upper disposable
corresponding to reservoir 302' on the lower disposable through
tubing segments D and A to exit the cannula 304 and preventing
blood coagulation within the cannula.
[0102] The cyclic filling and emptying of the ventricle 314' on the
lower disposable and the corresponding one on the upper disposable
314 causes the lever plate 53 to oscillate back and forth and
thereby rotate the cage wheel assemblies to pump anti-coagulant in
very small quantities during each stroke. The blood flowing through
the filter 308' and the corresponding one 308 on the upper
disposable extracts excess water from the blood, emptying it into
the collection vessel 316 where it can be periodically emptied by
suction or otherwise.
[0103] A third alternative embodiment illustrates the manner in
which the present invention can be adapted to administration of
insulin to a patient suffering from insulin dependent diabetes.
Insulin dependent diabetes is related to decreased production of
insulin by the Islets of Langerhans cells of the pancreas.
Diabetes, in both its Type I and Type II manifestations, has long
been treated with insulin or insulin-like substances. Diabetes is
notorious because of the dangers of unregulated blood sugar causing
immediate death or harm to a wide variety of vital body
systems--peripheral vascular, eyes, kidneys, etc.
[0104] To directly diagnose and treat blood, rather than
subcutaneous tissue, temporary needles-catheters may have to be
inserted into a vein, with ongoing threats of infection and
thrombosis, especially in infection prone diabetics. Thrombosis
might occur in the veins or it might clog the needles being
utilized for sampling. Frequent or continuous sampling, as would be
required for instant feedback control, would require return of
blood samples to the circulation and the blood could not be
permitted to clot in the external system. Total therapeutic level
anticoagulation would be required in the extracorporeal circuit. At
least prophylactic anticoagulation might also be desirable in the
patient, which, as has been described herein, is routinely
implemented by the apparatus of the present invention. A truly
intravascular glucose sensor on the end of a needle cannula would
thus seem desirable, but could pose its own problems interacting
with the blood. Such miniaturization would produce its own
difficulties. Furthermore, without a fistula or fistula graft of
some kind, the limited number of prominent naturally available
veins would be unlikely to weather a lifetime of needle
perforations and continuously indwelling catheters.
[0105] The present invention offers a practical alternative. It
utilizes a new blood access system to resolve the conundrum without
enduring the special problems of a totally implantable meter/pump
feedback system. It provides the same advantages by means of the In
Situ Debranched Vein Fistula Graft VFG and slight modifications of
the standard wrist and forearm worn device described herein. As
already explained, the VFG permits ready access to the arterial
venous pressure differential simply by alternately compressing it
from without at two adjacent sites, resulting in arterial pressure
upstream and venous pressure downstream from the point of
transcutaneous compression. The device not only mediates the
compressions, it also utilizes the arterial venous pressure
differential obtained in order to modulate blood flow through the
device and dispense anticoagulant into the entire extracorporeal
circuit. Modulation of blood flow is to a low but adequate level
for the task, e.g., 20-30 ml/min. in the case of the artificial
kidney, and probably even less in the case of diabetes care where
full therapeutic levels of anticoagulation can be achieved in the
extracorporeal circuit without beginning to threaten the whole
patient with more than prophylactic levels of anticoagulation.
[0106] As those skilled in the art can appreciate from a reading of
the present specification, the VFG holds considerable advantage
over alternative blood access arrangements. It does not require
repeated cannulizations of centrally leading arteries and/or veins
where even a single untoward event might impair an important
segment of the vascular system and even threaten the life of the
patient. Plastic AV fistula grafts are notorious for infection,
calcification, distal anastomosis narrowing and thrombosis. Direct
fistulae do not offer arterial venous pressure differential and,
interestingly, when plagued with various and multiple downstream
venous thromboses, are routinely converted to a single vessel "VFG"
through multiple ligations of vein branches. The VFG has no
downstream anastomosis. Remaining in situ, it retains its own
vasavasorum and lymphatic and nerve connections, making it more
resistant to infection and capable of rapid healing from day one,
especially from penetrations by the small needles-cannulae required
for these very low blood flows.
[0107] The blood is easily diverted from the arterialized segment
of the VFG upstream from the compression location and
anticoagulated to therapeutic levels from the very tip of the
cannula through a second lumen extruded in the cannula or a hollow
fiber laid within the blood lumen. The arterial blood then flows
directly to the modulating ventricle which regulates the
extracorporeal flow to the desired rate, utilizing reciprocating
volumetric means. Thereafter, the blood is returned by the venous
cannula to the downstream segment of the VFG. The reciprocations of
the swinging lever plate also drive the miniature roller
peristaltic pumps and the anticoagulant along with it. Arterial
blood glucose can be continuously monitored upstream in the device
and, through an electronic feedback control loop, appropriate
rapid-acting (regular) insulin can be added downstream in the case
of hyperglycemia, with perhaps a requirement for more than one
reading and some "gradularity" built in to prevent over-reaction
and swings of the glucose level up and down. Glucose might
alternatively be administered, to rapidly, but not too rapidly,
correct for hypoglycemia. The objective of this alternative
embodiment of the invention is to conveniently place a lock on the
blood glucose level for the balance of a patient's lifetime, in
order to avoid the possibly immediate lethal effects of
hypoglycemia as well as the chronically disastrous debilitating
effects of hyperglycemia. It is expected to be especially
applicable to the large proportion of diabetic patients already on
dialysis, whose renal failure derives directly from their diabetes.
Two therapies can easily be combined into one by including an
external glucose meter, electronic feedback loop and external
insulin pump directly onto the Wrist and Forearm Wearable
Artificial Kidney previously described.
[0108] In FIG. 13 there is shown the configuration of a lower
disposable 400 in solid line and the change to the lower disposable
to create the upper disposable in phantom line. The two are to be
used with the non-disposable pump structure shown in FIG. 9 for use
in addressing diabetes. Supported on the forearm worn assembly is a
blood glucose sensor 402', an insulin pump 404' and a glucose pump
406'. The glucose sensor 402' is exposed to the patient's blood in
that the percutaneous cannula 408 is adapted to pierce the
arterialized side of the VFG created in the diabetic patient's arm.
It is further contemplated that the output signal from the glucose
sensor 402' would be utilized by an insulin pump 404' which, in
turn, will inject insulin into the blood flowing through the tube
segment B' in an amount based on the glucose sensor output.
Likewise, the glucose pump 406' might be used to increase the level
of glucose in those patients threatened by hypoglycemia. Blood is
returned to the patient downstream from the compressions through A'
and venous cannula 410.
[0109] As in the earlier described embodiments, flow of blood into
and from the expansible ventricle 408' on the lower disposable 400'
and the corresponding expansible ventricle located on the upper
disposable member (not shown but substantially identical to
disposable member 400') is by way of magnetically actuated
occluders as more particularly described in connection with the
artificial kidney embodiment of FIGS. 1-10. As in the previous
embodiments, the filling of the ventricle 408' with the patient's
arterial blood pivots the lever plate 53 upward against the
corresponding blood filled ventricle 408 on the upper disposable
which is thus emptied. As the lever plate is driven upward, it
operates to rotate the roller pump assembly pressing on the tubular
segment B where segment B is on the upper disposable and segment B'
is on the lower disposable. The rolling movement of the roller
cages on the segments B' and B function as peristaltic pumps to
move an anti-coagulant to the arterial cannula 408 to maintain it
and the entire device free of clotting blood.
[0110] This invention has been described herein in considerable
detail in order to comply with the patent statutes and to provide
those skilled in the art with the information needed to apply the
novel principles and to construct and use such specialized
components as are required. However, it is to be understood that
the invention can be carried out by specifically different
equipment and devices, and that various modifications, both as to
the equipment and operating procedures, can be accomplished without
departing from the scope of the invention itself. For example, the
invention is readily adaptable to a wide variety of excorporeal
blood treatments.
* * * * *