U.S. patent application number 09/524452 was filed with the patent office on 2001-12-06 for deformable flow diverter.
This patent application is currently assigned to SHAW, BRIAN B. Invention is credited to Krivitski, Nikolai M..
Application Number | 20010047829 09/524452 |
Document ID | / |
Family ID | 24089273 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010047829 |
Kind Code |
A1 |
Krivitski, Nikolai M. |
December 6, 2001 |
Deformable flow diverter
Abstract
A diverter for selectively providing fluid communication between
ports to a common chamber is disclosed. The diverter includes a
resilient deformable common chamber having a plurality of ports.
Upon deforming the common chamber along a given line, fluid
communication between selected ports is precluded, which flow
preclusion is used to effectively reverse a flow direction in a
circuit connected to the diverter.
Inventors: |
Krivitski, Nikolai M.;
(Ithaca, NY) |
Correspondence
Address: |
HARTER SECREST & EMERY, LLP
1600 BAUSCH & LOMB PLACE
ROCHESTER
NY
14604-2711
US
|
Assignee: |
SHAW, BRIAN B
|
Family ID: |
24089273 |
Appl. No.: |
09/524452 |
Filed: |
March 10, 2000 |
Current U.S.
Class: |
137/597 ;
604/6.1 |
Current CPC
Class: |
A61M 1/367 20130101;
Y10T 137/87249 20150401 |
Class at
Publication: |
137/597 ;
604/6.1 |
International
Class: |
F16K 011/10 |
Claims
1. A flow diverter, comprising: (a) a resilient deformable chamber
having three ports, the chamber having a pair of opposing interior
surfaces, the interior surfaces having a contour selected to form a
flow barrier between two of the ports upon deformation of the
chamber.
2. The flow diverter of claim 1, wherein the ports are equally
spaced about a periphery of the chamber.
3. The flow diverter of claim 1, further comprising four ports.
4. The flow diverter of claim 1, wherein the surface contour
includes a smooth surface.
5. The flow diverter of claim 1, wherein the surface contour
includes opposing contours sufficient to maintain an engaged
relation independent of a deforming force.
6. A flow diverter, comprising: (a) a resilient generally
deformable chamber having a plurality of spaced ports, the chamber
being sufficiently deformable to contact opposing interior surfaces
to form a fluid barrier between two of the ports.
7. The flow diverter of claim 6, wherein the chamber includes a
pair of generally parallel walls.
8. The flow diverter of claim 6, the interior surfaces are selected
to form a continuous interface upon application of a clamping
force.
9. A flow diverter, comprising: (a) a resilient chamber having at
least three ports, the chamber including opposing interior
surfaces, the chamber being sufficiently deformable to contact the
opposing interior surfaces to substantially preclude fluid flow
between two of the ports.
10. A flow diverter, comprising: (a) a resilient chamber having at
least three ports, the chamber being sufficiently resilient to be
movable between a first deformed position permitting flow between
two ports and a second deformed position precluding flow between
the two ports.
11. A flow diverter, comprising: (a) a resilient chamber having at
least three ports, the chamber being deformable between a relaxed
position permitting fluid flow between two ports and a deformed
position precluding flow between the two ports.
12. A method of reversing a flow, comprising: (a) fluidly
connecting a common chamber to a source inlet, a source outlet, a
device inlet and a device outlet; and (b) selectively deforming the
common chamber to contact opposing interior surfaces of the chamber
to preclude fluid flow between the source inlet and the device
inlet.
13. A method of reversing a flow, comprising: (a) selectively
deforming a common chamber having four ports to contact opposing
interior surfaces of the chamber to preclude fluid flow between two
of the ports.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a flow diverter for
selectively changing a flow direction in a connected line, and
particularly to systems for replacement of kidney function in
patients with end stage renal disease (ESRD), and more particularly
to the treatment of ESRD by means of hemodialysis. In hemodialysis
systems, the current invention provides an apparatus for
selectively controlling the direction of flow in a portion of a
blood circuit of a patient undergoing hemodialysis. Specifically,
in the blood circuit comprising the closed loop through the
patient's vascular system and through the hemodialysis machine,
this invention relates to changing the direction of flow on the
patient side, that is, to and from the patient's vascular system,
without altering flow through the hemodialysis apparatus.
BACKGROUND OF THE INVENTION
[0002] In present day medical practice, hemodialysis is the
standard therapy for treating ESRD. This therapy involves dialyzing
the patient's blood several times a week. During treatment, the
patient's vascular system is connected to a hemodialysis machine
for sessions lasting several hours. This connection forms a blood
circuit whereby blood is drawn from the patient through a needle
connected to a patient access, cycled through a hemodialysis
machine that removes waste products including water, urea, and
other impurities from the blood, and returned to the patient access
via a second blood line and needle.
[0003] The functional interface between the patient and the
extracorporeal circuit is the patient or vascular access, from
which blood is withdrawn and to which the externally treated blood
is returned. To facilitate removal and return of blood, the patient
access may have specialized connections allowing mating of separate
arterial and venous blood lines, or the access may be cannulated
with a hollow needle which is then connected to arterial and venous
blood lines. Vascular access has been called the "Achilles' heel of
dialysis" because of the frequent morbidity associated with
maintenance and utilization of the access. A malfunctioning
vascular access is not trivial, as the access represents a conduit
for the passage of blood to the artificial kidney. Without
treatment via the external kidney, toxin accumulation in the body
is rapid and can be deadly.
[0004] One of the difficulties that can arise in chronic
hemodialysis is maintaining adequate blood flow during treatment
sessions. When flow rates decrease significantly during a session,
the attendant could in many cases restore adequate flow by
switching the blood lines. In current practice, the attendant must
usually turn off the hemodialysis machine. This process lengthens
the dialysis session while the machine is primed and restarted. In
addition, switching the blood lines involves disconnecting the
lines, which can cause bleeding and allow air to enter the lines.
Disconnecting the lines also breaks the microbe barrier, increasing
the possibility of infection.
[0005] Another difficulty that often arises with chronic
hemodialysis is the possibility that the patient will develop a
thrombus or blood clot that partially or wholly occludes a vascular
access created by a fistula or vascular graft. When a fistula or
graft becomes blocked, surgery is frequently needed to restore the
venous access to a useful condition or replace the access site. A
balloon angioplasty may be used to enlarge the lumen of the fistula
or graft and prevent the immediate formation of thrombosis, thereby
extending the life of the access. When a site can no longer be
restored, it must be replaced. Replacing an access is a serious
matter because patients have only a limited number of access sites
for A/V fistulas and PTFE grafts.
[0006] Accordingly, an object of the present invention is to
provide for the easy and convenient selection of which needle or
catheter will be used to draw blood from the access and which will
be used to return blood to the access at any particular time during
hemodialysis treatment sessions, wherein such flow reversal can be
employed in assessing access maintenance. Another object of this
invention is to have a device that is compatible with high rates of
flow in dialysis methods which utilize catheters. Yet another
object of this invention is to accomplish the flow reversal
function while minimizing the amount of turbulence associated with
blood flow through the device. Still another object of the
invention is to provide a device enhances safe use. A further
object of the invention is to minimize stagnant flow regions in the
device. Still another object of this invention is to provide a
device that is easily added to existing hemodialysis set ups and
treatment programs. Still another object of this invention is to
provide a low cost, easily manufactured, sterile disposable device
compatible with the rest of the blood circuit.
SUMMARY OF THE INVENTION
[0007] The present invention provides for the ready and reversible
redirection of flow through a circulating system. The present
invention finds particular application in the field of access
management and particularly to those systems employing dilution
technology.
[0008] Specifically, it has been found that measurements of
vascular access recirculation and vascular access flow during
dialysis are possible with "Ultrasound Dilution." Ultrasound
Dilution uses changes that occur in the velocity of an ultrasound
signal when blood is diluted with saline, instead of the
traditional measurement of differences in temperature or dye
concentration following an indicator infusion. Ultrasound travels
through blood more quickly than it does through saline. Thus, when
a bolus of saline is injected into the bloodstream, it dilutes the
blood and reduces the velocity of the ultrasound signal. This
reduction in the time it takes for the ultrasound signal to pass
between sensors can be measured using ultrasound transit-time
technology. By comparing the curves produced with the venous and
arterial sensors after infusions of saline, it is possible to
calculate recirculation, access flow and cardiac output. The
disclosure of U.S. Pat. No. 5,685,989 naming Nikolai M. Krivitski
and David R. MacGibbon as inventors, issuing Nov. 11, 1997 is
hereby expressly incorporated by reference.
[0009] The determination of access flowing using this technology
requires a reversal between the lines that draw blood and introduce
blood to the access. That is, it is necessary to readily select
which needle or catheter will be used to draw blood from the access
and which will be used to return blood to the access at any
particular time during hemodialysis treatment sessions. By allowing
ready "reversal" of the blood flow, the present invention assists
in access management including the determination of access flow,
recirculation and cardiac output.
[0010] The present invention provides an apparatus for selectively
diverting flow between ports of a common chamber so that flow
through a needle or catheter in the patient access can effectively
be reversed. In addition, the present invention may be manufactured
at a sufficiently reduced cost to promote single use of the device,
thereby reducing the risks associated with on-site sterilization
techniques.
[0011] The present flow diverter includes a resilient deformable
common chamber having a plurality of ports, wherein the chamber
includes opposing interior surfaces that contact upon deformation
of the chamber. Upon a sufficient deformation, the contacting
surfaces form a fluid barrier within the chamber and thereby
determine the permissible flow with respect to the ports.
Preferably, the chamber is sufficiently deformable to contact
opposing interior surfaces in a plurality of configurations to
provide selective fluid communication between the ports.
[0012] In a preferred configuration, the flow diverter of the
present invention can become an integral part of an extracorporeal
circuit, allowing for blood passage to the artificial kidney
(dialyzer) through the use of tubing similar to conventional
arterial and venous blood lines.
[0013] The present invention further contemplates a method of
reversing flow between the lines withdrawing blood and introducing
processed blood to the patient access. The method includes fluidly
connecting a common chamber to a source inlet, a source outlet, a
device inlet and a device outlet; and selectively deforming the
common chamber to contact opposing interior surfaces of the chamber
to preclude fluid flow between the source inlet and the device
inlet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic representation of a normal line
configuration of a dialysis circuit.
[0015] FIG. 2 is a schematic representation of a reversed line
configuration of a dialysis circuit.
[0016] FIG. 3 is a top plan view of the flow diverter.
[0017] FIG. 4 is a top plan view of the flow diverter showing
clamping lines for different flow configurations.
[0018] FIG. 5 is a cut away view showing interior surface
features.
[0019] FIG. 6 is a cross sectional view taken along lines 6-6 of
FIG. 4.
[0020] FIG. 7 is schematic view of the diverter in a first
extracorporeal circuit in a normal flow clamping.
[0021] FIG. 8 is schematic view of the diverter in the first
extracorporeal circuit in a reverse flow clamping.
[0022] FIG. 9 is schematic view of the diverter in a second
extracorporeal circuit in a normal flow clamping.
[0023] FIG. 10 is schematic view of the diverter in the second
extracorporeal circuit in a reverse flow clamping.
[0024] FIG. 11 is schematic view of the diverter in a third
extracorporeal circuit in a normal flow clamping.
[0025] FIG. 12 is schematic view of the diverter in the third
extracorporeal circuit in a reverse flow clamping.
[0026] FIG. 13 is a schematic view showing a baffle for selectively
permitting or precluding flow between adjacent ports.
[0027] FIG. 14 is a schematic view showing an alternative baffle
for selectively permitting or precluding flow between adjacent
ports.
[0028] FIG. 15 is a schematic side elevational view showing the
baffle in a first chamber configuration.
[0029] FIG. 16 is a schematic side elevational view showing the
baffle in a second chamber configuration.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Referring to FIG. 1, a hemodialysis circulating system is
shown. Although the present invention is described in connection
with a hemodialysis circulating system, it is understood the
diverter may be employed in any fluid system.
[0031] The circulating system 10 includes a patient circuit 20 and
an extracorporeal system 30. The patient circuit 20 includes the
natural vascular flow paths in the body as well as a patient access
22. The extracorporeal circulation system 30 extends between the
patient access 22 and a dialyzer 60 and includes interconnecting
tubing or lines 50.
[0032] Patient Access
[0033] The patient access 22 may be any of a variety of shunts,
grafts or fistulae. Traditionally, access to the patient's blood
stream has been provided by an arterio/venous ("A/V") fistula or by
a polytetrafluoroethylene ("PTFE") graft. An A/V fistula is a
surgical construct joining an artery to a vein. The shunting of
blood from an artery to a vein increases pressure on the vein,
which pressure enlarges its diameter and thickens its walls. A
fully developed fistula can be punctured with needles to access the
patient's blood system. A PTFE graft is an artificial blood vessel
used to connect the artery to the vein. The material used for the
graft is suitable for puncturing with needles to achieve the
necessary access to the patient's blood system. A third method of
obtaining access for hemodialysis is to use percutaneous catheters
which allow blood to be withdrawn from one lumen and returned by a
second lumen.
[0034] Extracorporeal Circuit
[0035] The extracorporeal circuit 30 extends from the patient
access 22 to the dialyzer 60 and back to the patient access. The
typical extracorporeal circuit 30 includes an arterial line 32
conducting blood from the patient access to the dialyzer 60 and a
venous line 34 conducting blood from the dialyzer to the patient
access 22.
[0036] The extracorporeal circuit 30 may include a pump 33 for
drawing blood from the patient access 22 to the dialyzer 60 and
returning the processed blood to the patient. A roller pump is
often employed as the external pump 33 which is often integrated
into the dialysis machine 60. Alternatively, the pump 33 may be
located in the arterial line 32. The pump 33 provides the negative
pre-pump and positive post-pump pressure needed facilitate flow
through the extracorporeal system 30. Although the present
invention is described in terms of a roller pump, it is understood
the extracorporeal circuit may be used with any of a variety of
pumps.
[0037] The flow of the blood through the extracorporeal circuit 30
between the patient access 22 and the dialyzer 60 may be in either
a normal or a reversed configuration. Referring to FIG. 1, the
normal configuration is shown, wherein the arterial line 32 to the
dialyzer 60 withdraws blood from an upstream location in the
patient access 22. The blood then passes through the dialyzer 60 to
return through the venous line 34 to be introduced into the patient
access 22 at a location downstream from the withdrawal of the
blood.
[0038] Referring to FIG. 2, the lines of the extracorporeal circuit
30 are shown in a reversed configuration. In the reversed
configuration, the arterial line 32 to the dialyzer 60 withdraws
blood from the patient access 22 at a downstream location. The
withdrawn blood is passed through the dialyzer 60 and returned
through the venous line 34 to an upstream location in the access
22. Thus, a portion of the blood that has passed through the
dialyzer 60 and been introduced into the access 22 is subsequently
withdrawn at the downstream location in the access.
[0039] As used herein, reversing the direction of flow in the blood
circuit 30 means drawing blood through the needle which had
previously been used to return blood to the patient and returning
blood through the needle which had previously been used to draw
blood from the patient without changing the direction that blood
circulates through the hemodialysis machine. This change is also
referred to herein as flow reversal or flow reversal in the patient
portion of the blood circuit.
[0040] It has been found advantageous to selectively switch the
blood flow in the extracorporeal circuit 30 between a normal line
configuration and a reversed line configuration during a given
session with a patient. The diverter 80 of the present invention
may be fluidly connected to the extracorporeal circuit 30 and
provide for selective flow paths through the circuit.
[0041] Referring to FIGS. 3-6, the diverter 80 includes a common
chamber 82 having a plurality of ports 100, 200, 300 and 400. The
common chamber 82 is a resilient and deformable member. The common
chamber 82 includes an interior surface 83, wherein portions of the
interior surface are selectively contacted by deformation of the
chamber. These selectively contacting portions are referred to as
opposing. The chamber 82 is sufficiently deformable such that upon
contacting opposing portions of the interior surface 83 a barrier
to fluid flow is created. The common chamber 82 is sufficiently
resilient such that upon release of the deformation force, the
interior surfaces 83 of the common chamber separate as the chamber
resumes its relaxed state and the flow barrier is terminated. The
common chamber 82 has deformation lines along which the chamber may
be deformed to contact the interior surfaces 83 and form the
interior barrier.
[0042] As shown in FIGS. 5 and 6, the common chamber 82 generally
has a bottom wall 84 and a top wall 86 joined about a periphery 88.
While a side wall may be employed intermediate the top wall 86 and
the bottom wall 88 at the periphery, a preferred configuration is
formed with the top wall and side wall joined at a common
periphery. It is anticipated the top wall 86 and the bottom wall 88
are slightly curvilinear to define a generally pillow shaped cross
sectional profile. The common chamber 82 is formed of a
sufficiently resilient material that as opposing portions of the
top wall 86 and the bottom wall 88 are urged together the walls
slightly stretch to form a line of contact, which forms a fluid
barrier. That is, the material of the common chamber 82 is
sufficiently compliant that folds are not formed as the opposing
surfaces are urged together.
[0043] Further, the common chamber 82 is selected such that upon
applying a line of constriction, or bias, the opposing interior
surfaces 83 contact along a line extending from one edge of the
chamber to a spaced edge of the chamber, while still forming an
open passage spaced from the contacting interior surfaces. That is,
the contacting portions of the interior surfaces 83 form a
continuous barrier that precludes fluid flow between two of the
ports.
[0044] The interior surface 83 of the common chamber 82 may include
features for assisting formation of the barrier upon contact of the
opposing portions. For example, one of the top wall 86 and the
bottom wall 88 may include a ridge 90 or ribs which contact the
opposing wall upon deforming the chamber 82. It is also
contemplated one wall may include a ridge and the remaining wall
includes a groove or trough 91 sized to receive the ridge 90. While
the present configuration is constructed such that common chamber
82 returns to the relaxed state upon removing the deformation
force, it is contemplated the interior surfaces 83 could be
configured to releasably engage and remain engaged after removal of
the deformation force. That is, the interior surfaces 83 may
function similar to a resealable container such as a ZIP LOCK.TM.
bag. The engaged walls of the common chamber 82 could be released
by flexing the chamber along a particular axis, thereby permitting
fluid flow between the previously blocked ports.
[0045] As shown in FIG. 5, the diverter 80 may be constructed of a
material to provide a top wall 86 and a bottom wall 88 having
sufficient thinness that a profile of the interior surface 83 is
complementary to a profile of an exterior surface. Conversely, as
shown in FIG. 6, the top wall 86 and the bottom wall 88 may have a
sufficient thickness that the interior and exterior profiles are
not coincident.
[0046] Referring to FIGS. 4-6, the exterior of the common chamber
82 may also include features to assist in contacting the necessary
interior surfaces. In one configuration, the exterior surface may
include grooves or recesses 87 along the deformation lines. These
exterior surface features 87 assist the operator in locating the
clamping lines.
[0047] The particular interior surface features may be selected in
cooperation with the number of ports and the anticipated flow
diversions to be accomplished by the diverter 80. In a first
configuration, the common chamber 82 has a generally rectangular
and preferred square periphery. The diverter 82 includes four ports
100, 200, 300 and 400, wherein the ports are generally located at
the comers of the rectangular profile. Each port is in fluid
communication with the common chamber and hence with each remaining
port. Although the ports 100, 200, 300 and 400 are shown as
equi-spaced it is understood the ports may be asymmetrically spaced
about the common chamber. In addition the ports 100, 200, 300 and
400 may be color coded to assist in set up and use of the extra
corporeal circuit 30.
[0048] Referring to FIGS. 13-16, the chamber 82 may include a
movable baffle 96. In this configuration, the common chamber 82 has
a square periphery and the baffle 96 is rotatable about an axis
passing through a center of the chamber 82. The baffle 96 has a
length and height sufficient to substantially preclude fluid flow
between the baffle and the adjacent top wall 86 and bottom wall 88.
The baffle 96 may be operably located along line N-N, thus
providing for fluid communication between ports 100 and 300, and
between ports 200 and 400. The baffle 96 can then be rotated to lie
along line R-R, thereby fluidly connecting ports 100 and 400, and
200 and 300 to provide for reversed flow. The baffle 96 and the
chamber 82 may be configured to have the baffle slightly stress or
deform the chamber as the baffle assumes the operable positions, as
shown in FIGS. 13 and 14.
[0049] As shown in FIGS. 7-12, the diverter 80 is operably located
in the extracorporeal circuit 30. Specifically, an upstream needle
14 is located in the patient access 22 and is connected to port 300
of the common chamber through an upstream (with respect to access
flow direction) line 52. Port 100 of the common chamber 82 is
connected to the input of the dialyzer 60 through a dialyzer
arterial line 54. Typically, the dialyzer arterial line 54 includes
the pump 33. Blood passes through the dialyzer 60 to exit via a
dialyzer venous line 56 which connects to the common chamber 82 at
port 200. The common chamber 82 is then connected by port 400 to a
downstream (with respect to access flow direction) needle 16 in the
patient access via a downstream line 58. Although needles are
described as providing penetration of the patient access, it is
understood that any of a variety of devices can be used and the
invention is not limited to a particular type of access. Further,
in this configuration, flow through the dialyzer arterial line 54
is always in the same direction and flow through the dialyzer
venous line 56 also remains in a constant direction.
[0050] To establish a normal direction flow through the
extracorporeal circuit 30, the common chamber 82 is deformed to
contact opposing interior surfaces 83 along line N-N of FIGS. 7, 9
and 11. Deformation of the common chamber 82 can be accomplished
through a variety of clamping and pinching devices including but
not limited to a hemostat or special device that acts like
hemostat. Clamping along line N-N contacts opposing portions of the
interior surface 83 and places ports 100 and 300 in fluid
communication while ports 200 and 400 are fluidly connected to each
other. There is no flow path between ports 100 or 300 to ports 200
or 400. Thus, blood flows from the patient access 22 into the
upstream needle 14 and through the upstream line 52 through port
300 and into half of the common chamber 82. Flow to ports 200 or
400 is precluded by the contacting interior opposing surfaces 83 of
the common chamber 82. Blood then flows from the half of the common
chamber 82 through port 100 to the dialyzer arterial line 54 and
into the dialyzer 60. The blood passes from the dialyzer 60 through
the dialyzer venous line 56 to port 200 of the common chamber 82.
As the blood cannot pass to ports 100 or 300, the blood flows out
of the common chamber 82 through port 400 to the downstream line
58. Blood passes through the downstream line 58 to enter the
patient access 22 through the downstream needle 16.
[0051] The blood flow in the two lines that are connected to the
needles will be changed according to the position of the clamping
system that divides the common chamber 82 into two parts.
Specifically, to reverse the blood flow with respect to the
upstream needle 14 and the downstream needle 16, the clamp is
removed from along lines N-N to then clamp along lines R-R, as
shown in FIGS. 8, 10 and 12. Upon clamping along lines R-R, ports
100 and 400 are in fluid communication and ports 200 and 300 are in
a separate fluid communication.
[0052] In this clamping configuration, blood is draw from the
patient access 22 through the downstream needle 16 to pass through
the downstream line 58, through port 400 and into a divided half of
the common chamber 82. The blood flows through port 100 and into
the dialyzer arterial line 54 to enter the dialyzer 60. The blood
exits the dialyzer 60 and passes through the dialyzer venous line
56 to enter a divided half of the common chamber 82 through port
200. The blood passes from the divided half of the common chamber
82 through port 300 into the upstream line 52 to pass through the
upstream needle 14 and enter the patient access 22.
[0053] Thus, by selectively clamping the common chamber 82 along
the clamping lines N-N or R-R, blood may selectively removed from
an upstream location in the patient access 22 to be returned at a
downstream location in the patient access, or removed from a
downstream location in the patient access to be returned to the
patient access at an upstream location, respectively.
[0054] In an alternative configuration, the common chamber 82 may
include the baffle rotatably connected to at least one of the top
wall 86 and the bottom wall 88 as shown in FIGS. 13-16. The
applications of the flow diverter are wide spread. For example, at
a time when vascular access hemodynamics were less well understood,
flow within the access had been identified as a parameter
associated with vascular access dysfunction, however, the early
method of measuring flow was expensive and was not easily
performed. With the advent of the indicator-dilution method for
measuring access flow, research activities surrounding flow within
the access as a predictor of access dysfunction intensified. The
resultant explosion of research has resulted in a wealth of data
supporting the ultrasound-dilution method as a reliable technique,
and has established a strong relationship between low or rapidly
declining access flow and the onset of serious stenosis and access
dysfunction.
[0055] It has been found in this dilution technology, that reversal
of blood flow in certain sections of the extracorporeal circuit are
advantageous. The ultrasound dilution measurements requires line
reversal, a process by which the arterial and venous blood lines
are disconnected from their respective needles and cross connected,
temporarily, in order to create conditions within the access which
make the measurement possible. Despite the non-invasive and
innocuous nature of the measurement device and indicator, the
reversal of lines proves a stumbling block in the mass distribution
and implementation of these valuable measurements. It is the line
reversal process that most people regard as the methods' only
fallacy, not only for the possibility of contamination of the
circuit by microbes or air bubbles, but also because of the
additional time required to complete this process. In an effort to
solve these problems and extend usage of the ultrasound-dilution
technique access flow measurements in strategies aimed at reducing
vascular access morbidity, the present invention provides a simple
means of reversing the arterial and venous blood lines for vascular
access blood flow measurement.
[0056] The subject invention avoids disconnecting the blood lines,
thus reducing the possibility for contamination of the
extracorporeal circuit. The invention also minimizes the chance for
thrombus formation within the diverter itself by eliminating areas
of stagnant blood flow.
[0057] Reversal of blood lines is also useful in dialysis
catheters. Frequently, dialysis center personnel will manually
reverse the blood lines in order to achieve greater flow to the
dialyzer while reducing negative pressure in the arterial line
which may cause blood cell damage. Additionally, this strategy may
be employed in order to reduce or eliminate recirculation in a
catheter. The subject invention offers a rapid means of reversing
blood lines to achieve optimal treatment in catheters.
[0058] The invention thus provides a means of reversing the
direction of flow in the extracorporeal portion 30 of the blood
circuit. This reversal can be accomplished easily without
disconnecting the lines during treatment and without shutting off
and restarting the dialysis machine 60. Flow through the dialysis
machine 60 continues uninterrupted during switching. Further, this
invention can be fabricated to comprise a low cost sterile
disposable unit that, in its preferred embodiment, includes a
single deformable resilient component. The present invention also
enables the user to choose an inlet/outlet configuration that
minimizes the pressure differential, thereby maximizing flow
through the dialysis machine.
[0059] Minimizing the amount of turbulence associated with blood
flow through the device is accomplished by ensuring that channels
are aligned, without sharp bends or turns, and sized to be
compatible with the inner cross section of the blood lines. The
device 80 reduces opportunities for clotting and/or stagnation of
blood flow because it contains no sharp turns or changes in
diameter in the fluid fittings, thereby promoting laminar flow.
[0060] The present invention also promotes safety in use in a
number of ways. First, the design configuration is very simple and
suitable for mass production as a sterile disposable, thereby
minimizing the possibility of infection from using the device.
Second, it is not complicated to operate. Third, the invention
allows flow to be reversed manually without requiring the
application of undue force or mechanical assistance. Fourth, the
invention maintains the sterile conditions in the entire blood
circuit during the flow reversal operation. The invention does not
allow air to enter the blood circuit or blood to be lost during
flow reversal.
[0061] Although the present invention has been described in terms
of particular embodiments, it is not limited to these embodiments.
Alternative embodiments, configurations or modifications which will
be encompassed by the invention may be made by those skilled in the
art, particular in light of the foregoing teachings. Alternative
embodiments, configurations, modifications or equivalents may be
included in the spirit and scope of the invention, as defined by
the appended claims.
* * * * *