CA1122815A - Dialysis apparatus and technique - Google Patents

Abstract

ABSTRACT
1. An ultrafiltration-measuring attachment for a dialyzer, said attachment having (a) a standard dialyzate conduit connection containing a length of conduit and connection means by which the attachment and the conduit can be connected directly to the dialyzate inlet of a dialyzer, (b) a gas injector in communication with the conduit for introducing a predetermined volume of gas through the conduit and into the dialyzer, (c) a valve that closes said communication and that can be opened to effect the gas introduction, and (d) a second standard dialyzate conduit connection communicating with the conduit.

Description

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 . . . . . : :

~2Z~3~L5 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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~ZB~5 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 , B~i 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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~2~ 5 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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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An attachment for a dialyzer, said attachment having:
(a) a body having a bore 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 in communcation with said bore, (b) gas injection means in communication with said bore for introducing a gas through said bore and into the dialysis unit, said gas injection means being located between said first standard connector and said second standard connector, (c) valve means which close the latter said communication and which can be opened to allow said gas introduction.

2. An attachment as claimed in claim 1, in which the attachment also contains a third standard dialyzate connector in valved communication with the second connector.

3. A dialyzer having connected thereto an attachment as claimed in claim 1 or 2.