Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to an ultraf.iltration-
measuring attachment for a dialyzer.
According to the present invent;on there is provided
an attachment for a dialyze-r, said attachment having:
(.a) a body having a ~ore therethrough, said body
having a first standard dialyzate connector for connecting said
attachment to the dialyzate inlet of a dialysis unit and a
second standard dialyzate connector, complementary to said first
standard connector, for connection to a source of dialyzate,
said standard connectors being ;n communication with said bore,
(b) gas injection means ïn communication with said
bore for introducing a gas throug~.said ~ore and into the
dialysis uni.t, said gas injection means being located between
said fi.r~t ~tandard connector and said second standard connector,
(cL valve means which close the latter said
communication and which can ~e opened to allow said gas
introduction.
The attachment can also have a third standard
dialyzate connector ln valved communication with the second
connector.
In the accompanying dEawings,
Figure 1 is a front elevation, partly in section,
of an ultrafiltration-measuring attachment according to one
example of the invention,
Figure 2 is a front elevation, partly in section,
of a dialyzer with which the attachment shown in Figure 1 can
` be employed,
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Figure 3 is a view generally along the line 2-2 in
Figure l,
Figure 4 is a sectional view along ~he line 3-3 in
Figure 2, and
Figure 5 is a front elevation, partly in section, of an
ultrafiltration-measuring attachment according to a further
example of the invention.
Referring to Figure 1, the attachment of said one
example is indicated generally at 270 and includes an air
injector 286 fitted on a valve body 272. The injector 286
has a squeezable bulb 88 which includes an air inlet tube 90
and which is secured by cementing or welding to an air outlet
tube 84 frictionally mounted on a nipple 82 projecting from
the body 272 and communicating with a passageway 278 in the
body 272. Valves 91, 92 in tubes 81 and 90 control the air
injection action, and a filter such as a plug 94 oE foamed
plastic or rubber can be used to make sure solid particles
are kept out of the entering air.
Valves 91, 92 can be of any desired type, but are shown
as balls of relatively inert material such as stainless steel
- snugly held in encircllng seats moulded into thick-walled
portions of tubes 84 and 90. As in conventional laboratory
pipette filling adaptors, by making the tube walls at least
about 3 millimeters thick but still yieldable, the valve
seats will deform when opposed portions of the tube around
them are manually pinched toward each other, and in such
deformation at least one section of the seat will be forced
away from the valve ball. This opens the valve. Releasing
the pinch permits the valve seat to return to ball-gripping
engagement over its entire periphery and this keeps the valve
closed.
~ The valve body 272 carries a standard ~emale ~ ;
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dialyzate connector 274 and two standard male dialyzate
connectors 202, 204. The valve body receives a rotatable
tapered valve plug 206 provided with a handle 208 by which
the valve plug can be rotated around its longitudinal axis.
A generally L-shaped aperture 210 extends transversely
through an intermediate portion of the plug/ and has two
openings 211, 212 respectively that can be brought into
communication with passageway 278 or ports 268 and 258.
Passageway 278 leads to connector 274, while ports 268, 258
separately open into connectors 202 and 204 respectively.
Aperture 210, passageway 278 and ports 268 and 258 are
arranged so that rotation of the valve plug will bring it to
a position as illustrated in Figure 1 in which it establishes
communication between ports 211 and 212 but keeps both ports
out of communication with passageway 278 and closes off that
passageway.
The valve arrangement also enables the valve plug to be
turned to a position 120 degrees clockwise from that
illustrated, in which it establishes communication between
port 268 and passageway 278, but closes port 2S8 from
communication with either one.
Attachment 270 is conveniently used by connecting
connector 274 with the dialyzate receiving connector of a
dialyzer, connecting connector 202 with a dialyzate supply,
and connecting connector 204 to the dialyzate return line.
The dialyzate discharge connector of the dialyzer is also
connected to that return line. Placing the valve in the
illustrated position then establishes a dialyzate by-pass
path, so that it is not necessary to use a dialyzate supply
system that has its own by-pass.
The attachment 270 is conveniently employed with the
dialyzer which is shown at 10 in Figures 2 to 4 and which
includes a plastic casing 12 made, for example, of
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polystyrene and having enlarged header end portions 14, 16
encircled by flanges 18l 20 respectively. Ultrasonically
welded to each flange is a plastic cap 22, 24 that covers the
casing ends and has a central nipple 26, 28 for introducing
the liquid to be dialy~ed at one end and removing it at the
other. The caps can be made of the same plastic as the
casing.
The interior of the casing contains partitioning that
subdivides it into a plurality of chambers and passageways
extending longitudinally through it, as more clearly seen in
Figure 4. Thus partitioning 30 subdivides the interior of
the casing into three large-bore chambers 31, 33 and 35 as
well as two smallbore passageways 32, 34. The chamber and
passageways extend the length of the casing and are only
interconnected near the casing ends. Near the upper end a
port 41 in the partitioning 30 establishes communication
between the upper portions of chamber 31 and passageway 32.
A similar port (not shown) in the lower portion of the
partitioning establishes communication between the lower
portions of passageway 32 and chamber 33, a third port 43 in
the upper portion of the partitioning establishes
communication between the upper portions of chamber 33 and
passageway 34, and a fourth port ~also not shown) at the
lower portion of the partitioning establishes communication
between the lower portions of passageway 32 and chamber 35.
A dialyzate inlet connector 51 is moulded integrally
with the enlarged lower end portion 14 of the casing and
opens into the lower portion of chamber 31, while a dialyzer
outlet connector 52 correspondingly provided in the upper
enlarged casing end portion 16 opens into the upper portion
of chamber 35 to complete the dialyzate flow path.
A bundle of hollow dialysis fibres 48 is inserted in
each chamber 31, 33, 35, the ibres extending the length
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of the casing. At or near each casing end the fibres are
potted in an end wall 54 of a sealing resin that can project
somewhat from the casing end as illustrated in Figures 2 and
3. End caps can be sealed against these end walls by gaskets
such as O-rings 56 shown in Figure 2 as fitted between short
flanges 58 projecting from the body 60 of each end cap.
Potting resin 54 which can be a polyurethane, leaves the
hollow interiors of the fibres 48 open so that the liquid to
be dialyzed flows through these fibres, preferably
countercurrent to the flow of the dialyzate in chambers 31,
33 and 35. Thus blood or other liquid to be dialyzed can be
introduced through upper nipple 28 and withdrawn from lower
nipple 26, while dialyzate is introduced into connector 51
and withdrawn through connector 52. The dialyzate flows
upwardly through chamber 31 around and between the individual
fibres in that chamber, then down through passageway 32,
after which it flows upwardly through chamber 33 around and
between the individual fibres in that chamber, then down
through passageway 32, after which it flows upwardly through
chamber 33 around and between the individual fibres there,
then descends through passageway 34 for a final pass upwardly
through chamber 35 around and between the individual fibres
there. From the upper portion of chamber 35 the dialyzate
flows out of the dialyzer 10 through the outlet connector
52.
The casing 12 is made of transparent plastic like
polystyrene so that the contents of passageways 32, 34 as
well as their side walls are clearly seen from outside the
casing. Chambers 31, 33, and 35 are also seen from outside
` the casing, but these chambers are essentially filled with
the hollow dialysis fibres 48, and when a dark liquid like
blood is being dialyzed there isn't much detail that can be ~-
made out visually other than the presence or absence of gas
bubbles in front of the fibres.
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In one embodiment of khe present invention the lengths
of chambers 31, 33 and 35 between the enlarged casing ends
14, 16 are cylindrical with diameters o~ about 2 1/3
centimetres so that each chamber can be packed with something
over 3,000 hollow fibres to provide a total membrane dialysis
surface of about 1 square meter per dialyzer or about 1/3
square meter per chamber. The passageways 32, 34 in this
embodiment are cylindrical with diameters of about 3/4 to
about 4/5 centimeters. So dimensioned the dialyzate flow
rates of 300 or 500 millilitres per minute will be rapid
enough to flush out of the dialyzer essentially all gas
bubbles that may appear in the dialyzate as the dialyzate
passes through it.
To operate the dialyzer 10, the connector 51 is
connected to the chamber 274 of the attachment 270 while the
connectors 202 and 204 of the attachment are connected
respectively to dialyzate supply and a dialyzate return line.
In addition, the dialyzer 10 is connected to dialyzate return
line at 52, and to a source of blood or other liquid to be
dialyzed at 28 as well as to a return for such liquid at 26~
For measuring the rate of ultrafiltration, the valve 206
is used to admit dialyzate to the dialyzer so that its
dialysis chambers and passageways are filled with dialyzate.
Thereafter a volume of air is introduced into chamber 31 by
operation of the air injector 270~ Such operation is easily
effected by pinching tube 84 at valve 91 and squeezing bulb
88. The bulb can be dimensioned so that one squee7e will
inject a suitable quantity of air into bore 78 and from there
by way of connector 51 into chamber 31. Valve 91 can then be
released to cause it to close, and it is sometimes helpful to
tilt the apparatus to help move the large air bubble into
chamber 31. After valve 91 is closed, valve 92 can be opened
momentarily to permit the bulb to expand and suck in a
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fresh supply of air through filter 94. This places the
apparatus in condition for the next injection of air.
The connection between connector 76 and the dialyzate
source is preferably closed when the air injection is taking
place. This will assure that the injected air is not carried
by incoming dialyzate too far through dialyzer 10 to permit
the desired measurement of ultrafiltration rate. In
addition, the valve 206 is turned to its by-pass position
after air injection in that introduction of dialyzate into
the dialyzer is shut off when the ultrafiltration is being
measured.
- Immediately after the injected air reaches chamber 31 it
rises to the top of that chamber. If the dialyzer is
maintained generally upright the air will not only reach the
top of chamber 31 but it will also move into the upper
portion of passageway 32 and part way down that passageway
until the height occupied by the air is about the same in
that passageway as in that chamber. This leaves the liquid
level in passageway 32 relatively low so that the volume of
ultrafiltration that can be measured by downward movement of
that water level is limited.
If the volume of air injected is kept small so as to
provide a high liquid level in passageway 32, then the liquid
level in chamber 31 is also relatively high and liquid from
that chamber will spill over into the passageway after a very
limited amount of ultrafiltration. Such spill-over makes it
impossible to subsequently measure ultrafiltration by liquid
level changes.
To avoid such limitation the dialyzer can be tilted
when the introduced air has risen. The degree of tilt is
such that it causes liquid to flow from near the tilted
upper end of chamber 31 into the tilted upper end of pas-
sageway 32. In this way the liquid levels can be adjusted so
that after restoring the dialyzer to its upright position,
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they are generally in positions such as shown at 37, 38 in
Figure 3.
So long as the blood or other liquid being dialyzed
flows through the hollow fibres, ultrafiltration takes place
causing water to move from the liquid being dialyzed through
the walls of the fibres. As a result there will be a gradual
increase in volume of the dialyzate around the fibres in
chamber 31 and the air bubble will move down into passageway
32. In Figure 3 the dialyzate level 37 in passageway 32 is
starting its slow traverse through that passageway. That
traverse is easily measured with an ordinary watch or clock
which have a seconds hand. A stop-watch can be used but is
not necessary inasmuch as the measurement times can be 30
seconds or longer and split-second timing does not add much
to the measurement accuracy.
The traverse of level 37 can be measured from the time
it leaves the level of the floor 41 of header 16, to the time
it reaches the top 43 of header 14. It is preferred however
to apply a scale alongside passageway 32, as by means of a
label 69 cemented onto the outside of the dialyzer casing.
Inasmuch as a label is generally used to carry instructions
as to the connections made to the dialyzer, the
ultrafiltration-measuring scale can be conveniently added to
such a label. The presence of a scale also enables the
making of two or more successive measurements during a single
traverse of the gas bubble through passageway 32.
Inasmuch as the ultrafiltration rat~ essentially depends
on the difference between the pressures on the inside and
outside of the hollow fibres, those pressures should be
adjusted to the values at which the ultrafiltration rate is
to be measured, and should not be changed during~ the
measurement. The presence of a gas bubble in chamber 31 and
the traverse of part of the bubble into passageway 32 will
not significantly affect either of the critical pressures.
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After the ultra~iltration rate has been measured,
dialysis can be restarted by merely rotating the valve 206
back to the dialysis position where it supplies dialyzate to
the dialyzer.
Blood is generally under a superatmospheric pressure of
a hundred or so tor when it is being dialyzed, although that
pressure can range from a low of about 30 tor to a high of
about 160 tor or even higher. The dialyzate is generally
under a subatmospheric pressure of about minus 50 to about
minus 100 tor but can range from almost zero to an extreme of
about minus 350 tor. While it is not essential to have the
dialyzate at subatmospheric pressure, the use of subatmos-
pheric pressure speeds up ultrafiltration. As a matter of
precaution the dialyzate pressure is substantially below the
pressure at which the blood is supplied, to keep dialyzate
from entering the blood stream in the event there is a leak
in the dialyzer. To maintain subatmospheric pressure in the
dialyzate the dialyzer's outlet ~2 is preferably maintained
in connection with the dialyzate supply system that develops
such negative pressure.
As an alternative to the example described above, the
ultrafiltration-measurlng attachment can be provided with an
air injector in the form of a simple vent which can be opened
to the atmosphere. Inasmuch as the dialyzate line is kept at
subatmospheric pressure whenever dialyzate is supplied, it is
only necessary to open the line to the atmosphere and thus
bleed a little air into the supplied dialyzate, when the
ultrafiltration rate is to be measured.
Figure 3 shows a vent-type construction in an
attachment 370. This attachment has a valve body carrying
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a standard dialyzate connector 374 that opens into a
passageway 378 leading to the rotatable plug of a plug valve
307. Also communicating with plug 306 is a port 368 that
leads to a standard connector 302 for a dialyzate supply.
Valve plug 306 has a first aperture 310 extending from a
side of the plug to its deep end, and a second aperture 313
in the shape of a transverse L positioned to establish
communication between port 368 and passageway 378 when the
plug is turned to the appropriate position. When so turned
aperture 310 does not open to either port 368 or passageway
378, but when the plug is turned 90 degrees counter-clockwise
looking at it from its handle end, it is in the position
shown in the drawing and aperture 310 then opens onto pas-
sageway 378. In this position port 368 is not in communica-
tion with passageway 378.
The deep end of aperture 310 can merely be exposed to
the atmosphere, preferably through a filter, but as
illustrated valve body 372 also carries a syringe barrel 320
and piston 322. Barrel 320 opens onto the deep end of the
valve plug, and piston can be preset to a position in the
barrel that provides a predetermined volume of air in the
barrel. This is readily accomplished as by inserting the
piston in the barrel, rotating the valve plug to a position
that opens the barrel to an air discharge port, pushing the
piston to the predetermined level, and then turning the valve
plug to close off the air discharge port. Such air discharge
port can be in the valve body 372 directly opposite port 368,
for example.
When attachment 370 is in use and the valve plug is
turned to the illustrated position after the piston 322 is
placed in its predetermined position, the fIow of dialyzate
to the dlalyz~c is cut ~, e and the air in barrel 320 is
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sucked into the dialyzate in the dialyzer. This carries
piston 322 into the barrel as far as it will go, at which
point the piston effectively seals off aperture 310. The
ultrafiltration rate can then be measured and when desired
dialysis is initiated or resumed by rotating valve plug 306
to the position at which it permits dialyæate flow through
the dialyzer.
It is also practical to provide the valve body with an
additional port leading to a connection for re~urning
dialyzate to the return line of a dialyzate supply system.
Such an additional port can for instance be directly opposite
passageway 378 so that when the valve plug is in the position
illustrated it establishes a dialyzate by-pass path.
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