FR2460698A1 - DIALYSIS MACHINE - Google Patents

Abstract

DIALYSIS MACHINE FOR USE WITH A DIALYZER COMPRISING MEANS FOR ESTABLISHING AND SETTING A DESIRED ULTRAFILTRATION SPEED; IT HAS A FLOW SYSTEM COMPRISING VALVES 22, 26 FOR BLOCKING THE VERSET FLOW FROM THE DIALYZER 12, AS WELL AS AN ULTRAFILTRATION BRANCH 48; SAID BRANCH 48 HAS A PISTON PUMP 52 WITH A SINGLE-ACTION FOR SUCTION OF LIQUID FROM THE FLOW SYSTEM AND A MOTOR 54 CONNECTED TO SAID PUMP FOR CONTROLLING THE SAME FROM SOME LIQUID FROM DETERMINED QUANTITIES PRECISION AND WITH A SPEED DETERMINED WITH PRECISION.

Description

Dialysis machine.

The invention relates to dialysis machines with

  artificial kidney, and more particularly a perfected device

  tioned to establish and regulate ultrafiltration speeds.

  The dialysis machines include a dialyzer and a dialysis machine which controls the operation of the dialyzer. The dialyzer is used to treat a patient's blood to remove water and waste. The

  dialyzer has a semipermeable membrane between the circuits

cooked with blood and dialysis solution flowing through

to the dialyzer. The elimination of waste is done by mass transfer through the membrane and the elimination of

  water is made by ultrafiltration through the membrane.

  In some dialysis machines, the dialysis solution is drawn through the dialyzer under pressure

  negative (i.e. below atmospheric pressure

  than). Such a machine is described in US Patent No. 3,878. 095, and a commercially available machine using such a system is manufactured and sold by Baxter Travenol Laboratories under the name "Proportioning Dialyzing Fluid Delivery System" (5M 1352-5M 1355). This machine can

  be considered a single pass or flow system

because the dialysis solution is continuously prepared, passes through the machine and the dialyzer, and then flows

to a drain.

  The removal of water from the blood by the ultra-

  filtration is based on the pressure difference existing on either side of the semipermeable membrane (i.e. the difference between the pressure of the blood circulating with a positive pressure in the dialyzer and that of the solution

of dialysis circulating with a negative pressure in the dialysis-

sister). This pressure difference is commonly called

  pressure at the faces of the membrane, and the amount of water removed

  born of blood is directly linked to it.

It is known that it is desirable to control the rate of ultrafiltration so as to control the amount and the rate of removal of water from the patient's blood. Representative ultrafiltration systems are described in U.S. Patent Nos. 3,844,940; 3,979,284; and

3,990,973.

  There is also an apparatus which is used in circulation systems with negative pressure to establish and regulate the ultrafiltration speeds. In this system an ultrafiltration branch is provided which is connected

to the drainage system near the entrance to the solu-

tion of dialysis in the dialyzer. The ultrafiltra branch

  tion includes a variable speed pump to draw liquid from the dialyzer with a flow rate or speed that corresponds to the ultrafiltration speed, a flow meter that displays the flow speed, and a drain to which

the withdrawn liquid flows out.

  When using this system, the operator adjusts the pump and observes the flow meter until it obtains the

adequate flow velocity corresponding to the velocity of

  desired trafiltration. Then the operator observes or deter-

  mines the pressure at the faces of the membrane for which the desired ultrafiltration speed is obtained, and the system is adjusted to this pressure at the faces of the membrane. In this system, manual adjustments and observations may not

not provide the accuracy required in some cases.

  The invention therefore proposes to provide a

  more precise system for establishing and adjusting the speeds of

trafiltration.

  The invention relates to a dialysis machine for

  to be used with an artificial kidney dialyzer and intended

  born to establish and control the ultrafiltration speed under

hated, and particularly in negative pressure flow dialysis machines. The machine includes an ultrafiltration branch comprising a very precise single-acting syringe-type pump for withdrawing liquid from the dialyzer in very precise quantities at very high speeds.

precise during ultrafiltration. The pump is driven

  born by any precise motor such as a stepper motor. This system does not require any manual operation or observation, which increases its accuracy. In addition to being useful in dialysis machines with negative pressure circulation, this system can be used with other types of machines such as load treatment machines, reconditioning

  circulation or positive pressure.

The present invention will be better understood on reading

  of the detailed description which follows and the examination of

annexed drawings which represent, by way of non-limiting example

  tif, an embodiment of the invention.

  Figure 1 is a schematic representation of a dialysis system which includes an ultrafiltration branch

  comprising a plunger pump of the syringe type and a -

  stepper motor for determining the ultrafiltration speed; Fig. 2 is a plan view showing the construction details of the piston pump; Figure 3 is an elevational view on an enlarged scale showing an adjustment device with limit switch associated with the pump; and

  Figure 4 is an end view of the pump, shown

  both the reduction gear to control the pump.

Referring now to the drawings, the dialysis system is designated by the reference 10 as a whole. The

system has three main sections, namely the system

  standard flow tem; the pressure adjustment system

  sion to the faces of the membrane; and the ultrafiltration branch.

The flow system comprises a dialyzer 12 of the

negative pressure type which includes a semi-permeable membrane

  ble which separates the blood which circulates through the dialyzer of

  the dialysis solution. Such dialyzers can be of the type

  eg either parallel plates or hollow fibers. Blood enters the dialyser through inlet 12a and out of it through the

  outlet 12b, while the dialysis solution enters through the

entry 12c and exit via exit 12d. In normal operation, the dialyzer can be tilted so that the output 12d

  is located above the entrance 12c in order to favor the eli-

mination of any gas bubbles formed in the dialy-

sister during dialysis.

Upstream of the dialyzer there is a power source

tation 14 for the dialysis solution. This food source

tion can consist either of a tank containing

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  loads of solution previously prepared either in a

  variant, by a known metering device preparing a met

  Fresh diaper continuously. The fresh dialysis solution starts from

the power source 14, flows in a main line

blade 16 passing through a device 18 at constant flow rate and arrives at an inlet pipe 20 connected to the dialyzer 12. An inlet valve 22 is mounted in the inlet pipe upstream of the dialyzer to allow or interrupt the flow towards the dialyzer. The spent dialysis solution leaves the dialyzer via an outlet line 24, a

outlet valve 26 being provided for authorizing or interrupting

pre flow of the dialysis solution from the dialysis

sister. A bypass line 28 has a bypass valve 30 which allows flow to be diverted from the dialyzer. The bypass line 28 is connected between

  the inlet pipe 20 and the outlet pipe 24.

  An adjustable flow control valve 32 is mounted

  downstream of the valves 26 and 30 so as to receive and regulate the flow. A negative pressure, constant speed pump 34 is mounted downstream of the control valve 32 to draw dialysis solution from the power source and through the dialyzer. Alternatively, the control valve 32 and the constant speed pump 34 can be replaced by a variable speed pump to regulate the flow of liquid. The spent dialysis solution is discharged from the dialysis system towards the drain 36. The pressure conditions inside the dialyzer, both on the blood side and on the dialysis solution side, are continuously monitored. A blood pressure transducer 38 monitors the pressure of the incoming blood, and a venous pressure transducer 40 monitors the pressure of the returned blood. Two negative pressure transducers are provided to measure the pressure of the dialysis solution in the dialyzer. The negative pressure transducer 42 located upstream measures the pressure of the dialysis solution at the inlet of the dislyser and downstream of the inlet valve; while the negative pressure transducer 44- located downstream measures the pressure at the outlet of the dialyzer and

upstream of the outlet valve 26.

  The transducers 42 and 44 were placed as close as possible to the dialyzer so as to obtain maximum precision for the pressure determinations. In addition, the negative pressure transducers 42 and 44 are arranged at the inlet and outlet of the dialyzer so as to operate both during the ultrafiltration mode and in the normal mode. The pressure adjustment system on the faces of the membrane includes a pressure adjustment device 46

  on the faces of the membrane which receives the cha output signal

  none of the pressure transducers 38, 40, 42 and 44. A desired pressure can be adjusted at the faces of the membrane on the adjustment device which then adjusts the actual pressure at

faces of the membrane on the desired value.

  The average blood pressure inside the dialyzer is determined by averaging the output values of the blood pressure transducer 38 and the blood pressure transducer.

  venous tension 40. The average negative pressure in the dia-

lyser is determined by averaging the output values of the upstream and downstream negative pressure transducers 42 and 44. These average pressures are added algebraically to

  determine the pressure at the faces of the membrane.

The adjustable flow control valve 32 is also

connected to the pressure adjustment device 46 at the

  faces of the membrane. The setting of the actual pressure at the fa-

these of the membrane is done via the valve 32 so as to maintain a predetermined pressure value

  at the faces of the membrane. The adjustment is carried out by the dispo-

  setting sitive which compares (1) the real pressure to the faces of the membrane, given approximately by the average blood pressure and the average negative pressure, with (2) the

predetermined pressure at the faces of the membrane which is deter-

mined during the ultrafiltration mode and which is applied to the adjustment device, and which (3) opens or closes the valve 32 to minimize the differences that may exist between the actual and predetermined pressures. The specific structure of

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  such adjustment devices is known and their operation

can be either manual or automatic.

  The ultrafiltration branch 48 comprises lines a, 50b, the piston pump 52, the stepping motor 54, and the indicator 56. The lines 50a and 50b are connected to the piston pump 52 and to the inlet line 20 of the dialysis solution in an intermediate position between the inlet valve 22 and the inlet 12c of the dialyzer. The negative pressure transducer 42 is preferably disposed between the point

  junction and input of the dialyzer.

  The piston pump 52, the stepping motor 54 and the

  indicator 56 are mounted on a support plate 58 and are

  shown in more detail in Figures 2, 3 and 4.

The piston pump 52 is constituted by a device of the single-acting syringe type which comprises a cylinder 60 of

  very precise finish and which has a cap at one end

  end cap 62 and a retractable piston device 64.

  The piston device 64 comprises the piston 66 and a rod

  threaded piston 68. The inside of the cylinder has a sec-

  very precise and uniform transverse tion, and the piston supports sealing points allowing it to slide tightly on the interior surface. The cylinder, the end cap and the piston define a chamber whose

  the volume can be determined and changed very precisely.

  The maximum volume of the piston chamber is approximately 200 ml, which corresponds to sufficient capacity to establish the

  desired ultrafiltration speed.

The lines 50a and 50b are connected to the end cap so as to allow the liquid to penetrate and

to pass through the piston pump 52.

Referring to FIG. 3, an arm 70 is mounted on the end of the piston rod 68, on the side opposite the piston,

and is arranged so as to come into contact with a switch

  limit switch 72 mounted on the support plate. The limit switch is used to stop the withdrawal movement of the piston device when the piston reaches a predetermined point (usually the end of movement or

piston stroke).

  Stepper motor 54 is connected to the piston rod

via a gear train 74. The gear train

grenages also couples the motor 54 to a potentiometer or

indicator 56 which indicates whether the engine is running or not.

  The motor 54 is usually called a stepping motor. In this type of motor, the armature rotates by a determined angle or increment upon reception of a pulse. In other words, for each pulse applied to the motor, the armature rotates

  an increment. The precise setting of the number of pulses applied

engine frequency and frequency of application allows precise adjustment of engine operation. Since the engine operation is precisely controlled, the piston withdrawal speed and the change in volume of the piston pump chamber are precisely controlled. The motor used is manufactured by Rapidsyn, Dana Industrial, 11901 Burke St., Santa Fe Springs, Cal. 90670; it is defined as a low angle continuous stepping motor, series 23, and is identified by model number 23 H-503; about it we

  will refer to U.S. Patent No. 3,519,859.

  In this particular motor, the armature moves in increments or 1.80 steps, so that 200 steps correspond to a full revolution of the armature. A pulse moves the motor armature by one step or 1.80. The gear train 74 establishes the relationship between the speed of rotation of the motor and

the rate of withdrawal of the fluid. In this system, the applica-

  tion of 10 pulses per second to the motor corresponds to an increase in the volume of the chamber of 1 ml / min, which in turn corresponds to a flow speed or liquid flow

or ultrafiltration speed of 1 ml / min (20 pulses / s cor-

correspond to 2 ml / min).

  Means for producing impulses and applications

  engine quer are known in the art, and include a

  keyboard input system 76 and an encoder and image generator

  pulses 78. In such a system the desired flow is entered

  the corresponding number of pulses is pro-

  duit and applied to the stepping motor 54. If for example we

  between 2 ml / min on the keyboard 76, 20 pulses / s are applied

engine 54.

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It will be noted that, if necessary, the gear train can be modified so as to obtain a relation

different between the engine pitch and the liquid withdrawal.

  Since the armature of the motor moves by in-

creations or not instead of moving continuously it

  it may be desirable to provide a steering wheel or other device

depreciation.

  Note that the step motor can be replaced

created by other drive devices or motors insofar as they can be controlled with precision so as to allow precise adjustment of the withdrawal speed of the piston.

  The main advantage of the system which has just been de-

  crit is that we know the trans-

cylinder and that the speed of movement or withdrawal of the piston can be precisely adjusted. Consequently, this makes it possible to very precisely regulate the flow rate of liquid sucked into the piston pump. This system therefore eliminates

some potential errors for setting and determining

tion of the ultrafiltration speed.

In normal operation, sometimes called

dialysis, blood flows through the dialyzer and pump 34 to

  negative ion, draws dialysis solution from the power source 14, via the constant flow device 18, the inlet line 20 and the dialyzer 12. From the dialyzer, the solution spent dialysis passes through line 24, valve 32, pump 34 and arrives at the drain. The negative pressure in the dialyzer is set in

adjusting the control valve 18 to obtain the sub-value

  hated. During normal operation, valves 22 and 26 are opened to allow the flow of fluid

  to and from the dialyzer. However, in some con-

predetermined editions, the valves 22 and 26 are closed so as to block the flow to and from the dialyzer,

  which isolates the dialyzer from the flow system and

bypass valve 30 is simultaneously open to allow direct flow between the power source

14 and the pump 34.

When it is desired to determine or adjust the ultrafiltration speed, the machine is no longer in the dialysis mode but in the ultrafiltration mode. In the mode

ultrafiltration valves 22 and 26 are closed in a

  re to isolate the dialyzer, and the bypass valve 30 is

  opened. Blood continues to circulate on the side of the pre-dialyzer.

  seen for this purpose. The ultrafiltration branch 48 is activated and the motor 54 is controlled with a speed or frequency of

  rotation which corresponds to the desired ultrafiltration speed

tee.

In this operating mode, when the piston

  retracts, it draws liquid from the drainage system

  which causes liquid to pass through the mem-

  semi-permeable brane, from the blood side to the solution side

tion of dialysis. This flow speed corresponds to the ultrafiltration speed. The only liquid in circulation in

the ultrafiltration branch is water passing through the mem-

brane and passing blood through the dialysis solution. When-

  that the desired ultrafiltration speed is reached, the pressure at the faces of the membrane stabilizes. At the moment,

  the average negative pressures indicated by the transducers

  negative pressure teurs 42 and 44 are noted and added

  algebraically at the average blood pressure determined from

  firing of the signals supplied by the transducers 38 and 40. This

value is determined and automatically applied to the device

  adjustment tif 46 and represents the pressure at the faces of the

membrane that provides the desired ultrafiltration speed.

  When the machine is returned to dialysis mode, the valves 22 and 26 are open, the bypass valve 30 is closed, and the motor 54 pushes the piston 66 in the opposite direction, which returns all the solution drawn into the system without loss or need for drainage, and the

pump 34 draws the dialysis solution through the system.

In dialysis mode, the system for adjusting the

  pressure at the faces of the membrane compares the value of the pressure

  sion at the terminals of the membrane which has been introduced and the actual pressure conditions as recorded by the pressure transducers 38, 40, 42 and 44, and controls the

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valve 32 to regulate the negative pressure in a manual manner

hold the actual pressure at the faces of the membrane at a value

  approximately equal to the value entered.

  The operator of the dialysis machine can decide at different times of the dialysis treatment that due to a change in the conditions in the dialyzer, the condition of the patient, etc., it is necessary to re-adjust the speed d 'ultrafiltration. To set the speed again

ultrafiltration, the system is returned to ultrafilter mode

tration in which the flow to the dialyzer is blocked by closing the valves 22 and 26, and the ultrafiltration branch and the pump 48 are activated. The procedure which has just been described is repeated to establish an ultrafiltration speed and to determine a desired pressure at the faces of the membrane. Automatic operation is planned

to perform certain functions that the operator can perform

kill manually.

  Of course, the invention is in no way limited to the embodiment of the example described and shown, it is capable of numerous variants accessible to humans

  of art, depending on the applications envisaged and without deviating

  ter for this the scope of the invention.

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Claims (8)

  1. Dialysis machine intended to be used with an artificial kidney dialyzer and intended to establish a desired ultrafiltration speed, machine comprising a flow system for entering a fresh dialysis solution into a dialyzer and discharging the solution spent dialysis of said dialyzer; a valve system mounted in said flow system for stopping flow to and from of said dialyzer; and an ultrafiltration branch connected to- said flow system between said valve system and said dialyzer, characterized in that said branch / comprises a piston pump / single acting to draw liquid from the flow system and a motor / connected to said pump for control it so as to draw liquid from said system in precisely determined quantities and with a precisely determined speed.   2. Machine according to claim 1, characterized in   that said motor is a stepping motor. 3. Machine according to claim 1, characterized in that said pump comprises: (a) means defining a chamber comprising a cylinder whose inner surface is precisely defined; (b) a piston intended to slide in leaktight manner on said interior surface; (c) a rod   piston connected to said piston to move it inside   laughing of said cylinder; and (d) that the motor is coupled to the- said piston rod to control its movement.   4. Machine according to claim 3, characterized in that a gear train is provided for coupling the motor to the piston rod. 5. Machine according to claim 1, characterized in   what a functioning indicator potentiometer is plied to the engine.   6. Machine according to claim 2, characterized in that each incremental movement of the armature of the motor corresponds to a determined change in the volume of the chamber   due to displacement of the piston. 7. Machine according to claim 6, characterized in that the speed of the incremental movement of the armature of the motor can be controlled with precision so as to adjust   precisely the rate of withdrawal of the fluid.   8. Method for determining the rate of ultrafiltration in a dialyzer of the negative pressure type which comprises a semi-permeable membrane, the dialysis solution circulating in said dialyzer on one side of the membrane with a negative pressure and the blood circulating from the other side of the membrane, and inlet and outlet pipes to circulate the   blood and dialysis solution to and from said dialysis seur, characterized in that it consists: (a) in circulating the blood and the dialysis solution through said dialyzer; (b) blocking the flow of the dialysis solution to and from said dialyzer; (c) then withdrawing liquid from the dialyzer in determined incremental quantities, with a predetermined flow rate; (d) determining the pressure on either side of the membrane which corresponds to this flow;   (E) to allow the flow of the solution of dia- again lysis through the dialyzer; and (f) then set the pressure real sion on the faces of the membrane during operation normal so as to obtain approximately the pre-   pressure determined at the faces of the membrane.