Apparatus For Peritoneal Dialysis

Abstract

An apparatus for peritoneal dialysis treatment of a patient operating automatically in accordance with a predetermined program comprising a plurality of successive dialysis cycles each consisting of a fill-phase during which fresh dialysis fluid is introduced into the peritoneal cavity of the patient, a dialysis-phase during which the dialysis fluid remains in the peritoneal cavity, and a drain-phase during which the used dialysis fluid is withdrawn from the peritoneal cavity of the patient. The apparatus comprises two identical measuring vessels having lower fluid connections, which through fluid valve means can be connected alternatively to a supply conduit for fresh dialysis fluid, a discharge conduit for used dialysis fluid and a patient conduit connected to the patient being treated, and upper air connections, which can be connected alternatively to the delivery side and the suction side of an air pump. During the fill-phase, when fresh dialysis fluid is introduced into the patient, fresh dialysis fluid is sucked under vacuum into one of the measuring vessels from the supply conduit at the same time as fresh dialysis fluid is discharged under pressure from the other measuring vessel into the patient conduit and this takes place alternatingly for the two measuring vessels. During the drain-phase, when used dialysis fluid is withdrawn from the patient, used dialysis fluid is sucked under vacuum into one of the measuring vessels from the patient conduit at the same time as used dialysis fluid is discharged under pressure from the other measuring vessel into the discharge conduit and this takes place alternatingly for the two measuring vessels.

Description

The present invention is related to an apparatus for peritoneal dialysis.

The purpose of a peritoneal dialysis as of any other dialysis method is to remove from a patient having an insufficient renal function the excess water and the waste products that would normally be removed from the body due to the renal function of the patient. At a peritoneal dialysis this is obtained in that a dialysis fluid, essentially consisting of a solution of various salts, is introduced into the peritoneal cavity of the patient, where it remains for a predetermined time. The peritoneum of the patient functions then as a semipermeable membrane which permits the passage of waste products and also some water to the dialysis fluid. Thereafter the used dialysis fluid, now containing waste products and some excess water from the patient, is drained from the peritoneal cavity. Thus, a complete dialysis cycle comprises a fill-phase during which fresh dialysis fluid is introduced into the peritoneal cavity of the patient, a dialysis-phase during which the dialysis fluid remains in the peritoneal cavity, and a drain-phase during which the used dialysis fluid is drained from the patient. Each such complete dialysis cycle requires a time of about 15 to 75 minutes and the volume of dialysis fluid introduced into the patient during the fill-phase is of the magnitude 0.5 to 2 liters. For a complete dialysis treatment a total volume of dialysis fluid of the magnitude of 60 liters must be supplied to the patient, wherefore it is obvious that a complete dialysis treatment takes a considerable time. Therefore, if peritoneal dialysis treatments are to be used in any considerable extent, an apparatus is necessary by means of which the dialysis treatment can be carried out substantially completely automatically according to a preset program, while full safety for the patient is maintained, so that the dialysis treatment does not require any constant supervision of the patient from the hospital staff. However, several comparatively severe demands are imposed upon such an automatically operating apparatus for peritoneal dialysis. Thus, the dialysis fluid introduced into the patient must be heated to body temperature and de-aired. Further, during each fill-phase an accurately predetermined volume of dialysis fluid must be introduced and during the subsequent drain-phase it must be safeguarded that at least an equally large volume of fluid is drained from the patient before a new fill-phase is started. Furthermore, during the complete dialysis treatment it must be possible to check the fluid balance of the patient, that is the difference between the total volume of fluid that has been introduced into the patient and the total volume of fluid that has been drained from the patient during the completed portion of the dialysis treatment. For a complete dialysis treatment, during which as mentioned above totally about 60 liters of dialysis fluid are introduced into the patient, said difference volume amounts to some liters and it is required that this volume can be determined with an error less than one-tenth of a liter. Consequently, it is appreciated that it must be possible to measure very accurately the fluid volumes introduced into and drained from the patient respectively. Further, it must be safeguarded that no infectious matter can be transferred from one patient to another through the dialysis apparatus. However, it should be possible to safeguard this without any time- and work-consuming cleaning and sterilization steps between different dialysis treatments.

All the requirements discussed above are satisfied in a very efficient way by means of an apparatus for peritoneal dialysis according to the present invention.

The apparatus according to the invention is characterized in that it comprises two identical measuring vessels each provided with a lower fluid connection at its lower end and an upper air connection at its upper end and with a lower fluid level detector adjacent said lower fluid connection and an upper fluid level detector adjacent said upper air connection; an air pump with a delivery side and a suction side; air valve means for connecting alternatingly the delivery side of said air pump to said upper air connection of the one measuring vessel and simultaneously the suction side of said air pump to said upper air connection of the other measuring vessel and vice versa; a patient conduit provided for connection to a patient to be treated; first fluid valve means for connecting said patient conduit to said lower fluid connection of alternatingly the one and the other measuring vessel; a supply conduit for fresh dialysis fluid and a discharge conduit for used dialysis fluid; second fluid valve means for connecting alternatingly said supply conduit and said discharge conduit to said lower fluid connection of alternatingly the one or the other measuring vessel; and programmed control means responsive to said fluid level detectors for controlling said air valve means and said first and second fluid valve means in such a way that

to introduce fresh dialysis fluid into the patient fresh dialysis fluid is sucked into one of said measuring vessels from said supply conduit through said second fluid valve means until said upper fluid level detector of said measuring vessel indicates that the vessel is full and at the same time dialysis fluid is discharged under pressure from the other measuring vessel to said patient conduit through said first fluid valve means until said lower fluid level detector of said other vessel indicates that the vessel is empty, whereafter fresh dialysis fluid is sucked into the emptied measuring vessel from said supply conduit through said second fluid valve means and at the same time dialysis fluid is discharged under pressure from the filled measuring vessel to said patient conduit through said first fluid valve means, and so on in alternating sequences,

whereas to drain used dialysis fluid from the patient used dialysis fluid is sucked into one of said measuring vessels from said patient conduit through said first fluid valve means until said upper fluid level detector of said vessel indicates that the vessel is full and at the same time dialysis fluid is discharged under pressure from the other vessel to said discharge conduit through said second fluid valve means until said lower fluid level detector of said other vessel indicates that the vessel is emptied, whereafter used dialysis fluid is sucked into the emptied vessel from said patient conduit through said first fluid valve means and at the same time the dialysis fluid in said filled vessel is discharged under pressure into said discharge conduit through said second fluid valve means and so on in alternating sequences.

As the apparatus according to the invention comprises two identical measuring vessels and the introduction of fresh dialysis fluid into the patient during the fill-phase of a dialysis cycle as well as the draining of the used dialysis fluid from the patient during the drain-phase of the dialysis cycle is carried out in that the dialysis fluid is sucked by means of a vacuum into one of the measuring vessels and subsequently by means of overpressure is discharged again from the measuring vessel and this takes place simultaneously and alternatingly for both measuring vessels, it becomes possible during the fill-phase as well as the drain-phase to determine in a simple and in spite of this accurate manner the volume of fresh dialysis fluid being introduced into the patient and the volume of used dialysis fluid being drained from the patient respectively by quite simply counting the number of measuring vessels filled with fluid that are being supplied to or drained from the patient respectively. As the same measuring vessels and the same "pumping operation" is used both during the fill-phase and the drain-phase and additionally the volume of the measuring vessels can be small as compared with the total volume of fluid being pumped during a complete dialysis treatment, the measuring errors can be kept very small. By using two measuring vessels it is also obtained that the supply of dialysis fluid to the patient during the fill-phase as well as the draining of used dialysis fluid from the patient during the drain-phase is continuous.

The automatization of the operation of the apparatus is also comparatively easy in that each measuring vessel is provided with an upper fluid level detector indicating when the vessel is filled and a lower fluid level detector indicating when the vessel is emptied; the signals from these fluid level detectors being usable as control signals for a preprogrammed logic control unit which controls the fluid valves determining the fluid flow between the measuring vessels, the patient conduit, the supply conduit for fresh dialysis fluid and the discharge conduit for used dialysis fluid as well as the air valves determining the connection of the air pump to the measuring vessels.

As in an apparatus according to the invention the dialysis fluid comes into contact only with the two measuring vessels, the patient conduit, the supply conduit for fresh dialysis fluid, the discharge conduit for the used dialysis fluid and the pipe connections between these fluid conduits and as the fluid valves controlling the fluid flow between the different conduits and the measuring vessels may preferably consist of tube clamps, which from the outside pinch the conduits which consist of resiliently compressible tubes at least opposite said tube clamps, those parts of the apparatus that are brought in contact with the dialysis fluid may without any technical or economical difficulties be constructed and manufactured as a dispensable set for "one-time" use only, which is readily mounted on an apparatus panel provided with the controlled tube clamps and necessary electrical contacts, for instance for the fluid level detectors of the measuring vessels, and which after each dialysis treatment is discarded and replaced with a new set. In this way a full guarantee is obtained against a transfer of infectious matter from one patient to another without any cleaning or sterilization of complicated apparatus components being necessary.

In the following the invention will be further described with reference to the accompanying drawing in which

FIG. 1 is a simplified diagram illustrating an apparatus for peritoneal dialysis according to the invention;

FIG. 2 is a schematic perspective view of the control and instrument panel of the dialysis apparatus with a dispensable one-time-use set mounted thereon; and

FIG. 3 illustrates a modification of the apparatus illustrated in FIG. 1.

In the diagram of FIG. 1 fluid conduits are illustrated with double lines, air conduits with single solid lines, electrical signal conductors with broken lines and electrical power conductors with dash-and-dot lines.

The dialysis apparatus according to the invention illustrated in FIG. 1 comprises two identical measuring vessels M1 and M2. Each vessel is provided with a lower conduit or tube connection 1 and 3 respectively and an upper conduit or tube connection 2 and 4 respectively. Preferably the vessels are shaped to have a relatively small cross-sectional area close to said tube connections. At its lower tube connection 1 each vessel is provided with an annular electric electrode E1 and E3 respectively. In a similar manner an annular electric electrode E2 and E4 respectively is provided at the upper tube connection of each vessel. A third electric electrode E5 and E6 projects from above into each vessel so that the lower tip of this electrode is positioned close to the lower annular electrode E1 or E3 respectively. The electrodes E1, E2 and E5 in the measuring vessel M1 are connected to two detector units D1 and D2, which sense the resistance between the electrodes E1 and E5 and the resistance between the electrodes E2 and E5 respectively. The detector D1 is designed to provide a signal on its output when the resistance between the electrodes E1 and E5 displays a stepwise increase, that is when the electrically conducting dialysis fluid sinks so far in the measuring vessel M1 that the fluid surface reaches the annular electrode E1. The detector D2 is designed to provide a signal on its output when the resistance between the electrodes E2 and E5 displays a stepwise decrease, that is when the dialysis fluid rises so high in the measuring vessel M1 that the fluid surface reaches the annular electrode E2. Thus the fluid level detector D1 indicates when the measuring vessel M1 is empty, whereas the fluid level detector D2 indicates when the measuring vessel M1 is filled. In the same way the electrodes E3, E4 and E6 in the other measuring vessel M2 are connected to two fluid level detectors D3 and D4, of which the detector D3 provides an output signal when the measuring vessel M2 is emptied, whereas the detector D4 provides an output signal when the measuring vessel M2 is filled.

The dialysis apparatus comprises additionally a supply conduit L1 for fresh dialysis fluid from a source of dialysis fluid not shown in the drawing, a discharge conduit L2 for used dialysis fluid that has been drained from the patient and a patient conduit L3 provided to be connected to the patient to be treated, for instance by means of a catheter inserted into the peritoneal cavity of the patient. The lower connections 1 and 3 of the measuring vessels M1 and M2 respectively are through branch conduits L4 and L5 respectively connected to the patient conduit L3 and through additional branch conduits L6 and L7 respectively to a conduit junction L8, to which also the supply conduit L1 and the discharge conduit L2 are connected. The two branch conduits L4 and L5 from the patient conduit L3 are provided with a stop valve V6 and V5 respectively illustrated only schematically in the drawing but consisting of electrically controlled tube clamps which can clamp their associated conduits from the outside and interrupt the fluid flow through the conduits, which consist of resiliently compressible tubes or hoses at least opposite these tube clamps. In the same way the branch conduits L6 and L7 are provided with stop valves V4 and V3 respectively consisting of electrically controlled tube clamps. Also the supply conduit L1 and the discharge conduit L2 are provided with such electrically controlled tube clamps V1 and V2 respectively.

For the heating of the fresh dialysis fluid supplied through the conduit L1 to a predetermined desired temperature a heating device is provided, which includes a metal pipe 6, as for instance of stainless steel, forming a portion of the supply conduit L1. The heating device includes also a controlled electric current source 7 having a power output which can be connected to opposite ends of the metal pipe 6 by means of electrical terminals 8 and 9. Thus, the fresh dialysis fluid flowing through the metal pipe 6 is heated by the electric current from the current source 7 passing through the metal pipe 6. The temperature of the dialysis fluid is measured at the downstream end of the metal tube 6 by means of a suitable temperature transducer 10, for instance consisting of thermocouple, which measures the temperature of the metal tube 6 and which is connected to the controlled current source 7 so as to control the output power of the current source, whereby the fresh dialysis fluid supplied to the apparatus is maintained on a predetermined desired temperature.

The upper connections 2 and 4 of the measuring vessels M1 and M2 respectively are through moisture traps 11 and 12 respectively and germ filters 13 and 14 respectively connected to two electrically operated valves V7 and V8 respectively. The valve V7 is connected through a pipe 15 to the delivery side of an air pump 16, whereas the valve V8 is connected through a pipe 17 to the suction side of the pump 16. An expansion tank 18 and a variable relief valve 19 are connected to the pressure pipe 15. In a similar manner an expansion tank 20 is connected to the vacuum pipe 17. A variable vacuum regulator 21 and a pressure gauge 22 are also connected to the vacuum pipe 17 through an electrically operated valve V9. The vacuum pipe 17 communicates also with the ambient atmosphere through a throttle passage 36 which is adjusted to determine the maximum vacuum in the pipe 17.

All the fluid valves V1 to V6 as well as all the air valves V7, V8 and V9 are controlled from a programmed control unit S. For the sake of simplicity the control signal connections between the various valves and the control signal outputs 23 of the control unit are not shown in the drawing. The control unit S can be constructed with the use of conventional components and conventional technique, wherefore it is not illustrated in detail in the drawing.

The control unit S is primarily responsive to and controlled by the output signals from the fluid level detectors D1, D2, D3 and D4. Additionally the control unit S receives control signals from a counter R1 and two variable timers T1 and T2. The counter R1 is a reversible counter which can count in both directions and is provided with a first input 24 for drive pulses when counting in the one direction and a second input 25 for drive pulses when counting in the opposite direction. As described in the foregoing, the upper fluid level detector D2 of the measuring vessel M1 provides an output signal each time the measuring vessel M1 has been filled with dialysis fluid. In the same way the upper fluid level detector D4 for the other measuring vessel M2 provides an output signal each time this measuring vessel M2 has been filled with dialysis fluid. The output signals from these two fluid level detectors D2 and D4 can be supplied through a switch S1 alternatively to the first input 24 or the second input 25 of the counter R1. The switch S1 is operated by the control unit S so as to be in the position illustrated in the drawing during the fill-phase of a dialysis cycle, that is when fresh dialysis fluid is pumped into the patient, whereas it is in the opposite position during the drain-phase of the dialysis cycle, that is when the used dialysis fluid is drained from the patient. Consequently, it is appreciated that during the fill-phase of a dialysis cycle the counter R1 will count in its one direction the number of measuring vessels being filled with fresh dialysis fluid to be pumped into the patient, whereas during the drain-phase of the dialysis cycle the counter counts in its opposite direction the number of measuring vessels being filled with used dialysis fluid drained from the patient. The counter R1 is provided with a manually presetable output 26 on which an output signal is provided when the counter R1 during the fill-phase of a dialysis cycle reaches the count, i.e. has counted the number of filled measuring vessels, corresponding to the presetting of the output 26. This output signal from the counter output 26 activates the control unit S to interrupt the fill-phase of the dialysis cycle, that is the supply of fresh dialysis fluid to the patient. The counter R1 is also provided with an output 27 from its O-stage, on which output a signal is provided when the counter R1 during the drain-phase of a dialysis cycle has counted the same number of filled measuring vessels as during the preceding fill-phase of the same dialysis cycle. The control unit S is designed not to be able to interrupt the drain-phase of the dialysis cycle, that is the draining of used dialysis fluid from the patient, until it has received a signal from the output 27 of the counter R1. In this way it is safeguarded that at least an equal number of measuring vessels with used dialysis fluid is drained from the patient during the drain-phase as the number of measuring vessels with fresh dialysis fluid that has been pumped into the patient during the preceding fill-phase.

The length or duration of the fill-phase is consequently determined by the presetting of the counter R1, that is by the number of measuring vessels with dialysis fluid one wishes to pump into the patient during each dialysis cycle. The length or duration of the dialysis-phase subsequent to the fill-phase is determined by the setting of the timer T1, whereas the length of the drain-phase is determined by the setting of the timer T2. However, as mentioned above, the drain-phase cannot be interrupted until a signal is provided on the output 27 of the counter R1 even if the time preset in the timer T2 should run out before said signal has been provided. For determining the length of the dialysis-phase and the drain-phase respectively the control unit S may for instance include a pulse counter provided to count a predetermined number of pulses during the dialysis-phase and a predetermined number of pulses during the drain-phase, in which case the two presetable timers T1 and T2 consist of pulse generators with variable pulse frequency, the output pulses of which are used for driving the pulse counter in the control unit S during the dialysis-phase and the drain-phase respectively. An indicating instrument I1 is connected to the control unit S for indicating the stage of the program, that is the dialysis cycle, in which the apparatus is currently operating.

The output signals from the fluid level detectors D2 and D4 counting the number of filled measuring vessels during the fill-phase and the drain-phase can also be connected through a switch S2 alternatively to the one input 28 and the second input 29 respectively of a reversible counter R2. The switch S2 is operated by the control unit S so as to be in the position shown in the drawing during the fill-phase of a dialysis cycle and in its opposite position during the drain-phase. Consequently, the count in this counter R2 will continuously correspond to the difference between the total number of measuring vessels filled with fresh dialysis fluid that has been supplied to the patient and the total number of measuring vessels filled with used dialysis fluid that has been drained from the patient during the completed portion of a dialysis treatment. Thus, the count in the counter R2 represents the instantaneous fluid balance of the patient. The count in the counter R2 can be transferred through a gate G to a store ST. The gate G is controlled by the control unit S so as to open after the drain-phase of each dialysis cycle before the fill-phase of the next dialysis cycle. Consequently, the count stored in the store S2 represents the accumulated fluid balance of the patient before the beginning of the current dialysis cycle. An indicating instrument I2 is connected to the store ST for indicating this accumulated fluid balance. By means of a manually operated switch S3 the instrument I2 may be temporarily connected to the output of the counter R2 for indicating the instantaneous fluid balance of the patient during the current dialysis cycle.

FIG. 1 shows the apparatus during a fill-phase, that is when fresh dialysis fluid is pumped into the patient, when fresh dialysis fluid is being sucked into the measuring vessel M1 from the supply conduit L1 at the same time as fresh dialysis fluid is being discharged under pressure from the other measuring vessel M2 through the patient conduit L3 to the patient.

When the apparatus is started for the fill-phase of the first dialysis cycle of a dialysis treatment, both measuring vessels M1 and M2 as well as all conduits L1 to L8 are empty. The valves V7, V8 and V9 are in the positions illustrated in FIG. 1 so that a vacuum exists in the measuring vessel M1, whereas an overpressure exists in the measuring vessel M2. The overpressure in the pressure pipe 15 is determined by the relief valve 19, whereas the vacuum in the vacuum pipe 17 is as low as the pump 16 can make it. The tube clamps V2, V3, V5 and V6 are closed, whereas the tube clamps V1 and V4 are open, whereby the supply conduit L1 for fresh dialysis fluid communicates with the lower connection 1 of the measuring vessel M1. Consequently, fresh dialysis fluid is sucked from the supply conduit L1 into the measuring vessel M1 by the vacuum in this measuring vessel. When the fluid surface in the measuring vessel M1 reaches the upper electrode E2, the upper fluid level detector D2 provides a signal as described in the foregoing indicating that the measuring vessel M1 is filled. This output signal is supplied to both counters R1 and R2, which consequently count one filled measuring vessel, and also to the control unit S, which closes the tube clamp V4 so that the communication between the filled measuring vessel M1 and the supply conduit L1 is interrupted, opens the tube clamp V6 so that the filled measuring vessel M1 is instead connected to the patient conduit L3, and opens the tube clamp V3 so that the other measuring vessel M2 is connected to the supply conduit L1. At the same time the air valves V7 and V8 are switched to their opposite positions so that the measuring vessel M2 is put under vacuum, whereas the measuring vessel M1 is put under overpressure. Therefore, fresh dialysis fluid from the supply conduit L1 will now be sucked into the empty measuring vessel M2, whereas the dialysis fluid in the previously filled measuring vessel M1 is discharged into the patient conduit L3 to the patient. The overpressure in the pressure pipe 15 and the vacuum in the vacuum pipe 17 are such that the filling of the measuring vessel M2 requires less time than the discharging of the measuring vessel M1. When the measuring vessel M2 is filled with fresh dialysis fluid up to its upper electrode E4, the upper fluid level detector D4 provides an output signal, whereby the counters R1 and R2 count one more filled measuring vessel at the same time as the control unit S is caused to close the tube clamp V3 so that the connection between the supply conduit L1 and the now filled measuring vessel M2 is interrupted. When somewhat later the measuring vessel M1 has been emptied to such an extent that the fluid level in the vessel has reached the lower electrode E1, the lower fluid level detector D1 provides a signal to the control unit S indicating that the measuring vessel M1 is emptied. The control unit S closes then the tube clamp V6 so that the connection between the measuring vessel M1 and the patient conduit L3 is interrupted, opens the tube clamp V5 so that instead the filled measuring vessel M2 is connected to the patient conduit L3, and opens the tube clamp V4 so that the emptied measuring vessel M1 is connected to the supply conduit L1. Simultaneously the two valves V7 and V8 are returned to the positions shown in the drawing so that the measuring vessel M1 is once more put under vacuum, whereas the measuring vessel M2 is put under overpressure. Thus, the dialysis fluid in the filled measuring vessel M2 will be discharged under pressure into the patient conduit L3, whereas fresh dialysis fluid from the supply conduit L1 is sucked into the empty measuring vessel M1. This alternating sequence with fresh dialysis fluid from the conduit L1 being sucked into one of the measuring vessels while at the same time dialysis fluid is discharged under pressure from the other measuring vessel through the patient conduit L3 to the patient continues until the counter R1 reaches the preset count of the output 26, which corresponds to the number of measuring vessels with fresh dialysis fluid one wishes to introduce into the patient during each fill-phase. The output signal provided on the output 26 of the counter R1 causes the control unit S to operate the valves V1 to V8 in such a way that the dialysis fluid in the filled measuring vessel is discharged under pressure through the patient conduit L3 without any fresh dialysis fluid from the supply conduit L1 being simultaneously sucked into the other measuring vessel. Consequently, the fill-phase ends with both measuring vessels M1 and M2 emptied and with the fluid levels located at the lower electrodes E1 and E3 respectively in both vessels. At the end of the fill-phase all tube clamps V1 to V6 are closed, whereas the valves V7 and V8 remain in their last positions. It is appreciated that at the end of the first fill-phase of the dialysis treatment also the counter R2 contains a count corresponding to the number of measuring vessels with fresh dialysis fluid that has been introduced into the patient during this fill-phase.

The length or duration of the dialysis-phase following the fill-phase is, as described in the foregoing, determined by the setting of the timer T1. When the preset time for the dialysis-phase runs out, the control unit S is activated to initiate the drain-phase, that is the withdrawal of the used dialysis fluid from the patient.

As obvious from the foregoing, the drain-phase starts with both measuring vessels M1 and M2 empty. If it is assumed that at the beginning of the drain-phase the two air valves V7 and V8 are in the positions shown in the drawing so that there is vacuum in the measuring vessel M1 and overpressure in the measuring vessel M2, the control unit S initiates the drain-phase by opening the tube clamp V6 so that the measuring vessel M1 is connected to the patient conduit L3. The other tube clamps remain closed. At the beginning of the drain-phase the valve V9 is also switched to its open position so that the vacuum regulator 21 is connected to the vacuum pipe 17. In this way the vacuum in the vacuum pipe 17 will be maintained on the value determined by the preset vacuum regulator 21. This vacuum is indicated by the pressure gauge 22. Thus, used dialysis fluid will be sucked out from the patient under the action of a predetermined variable vacuum. With the different valves in these new positions used dialysis fluid is sucked out from the patient through the patient conduit L3 into the measuring vessel M1, until this is filled and the fluid level detector D2 provides a signal. This output signal is transferred on the one hand through the switch S1, which is now in its opposite position, to the input 25 of the counter R1 and on the other hand through the switch S2, which is also in its opposite position, to the input 29 of the counter R2. Consequently, both counters R1 and R2 are now counting in their opposite direction, that is reduce their counts. The output signal from the fluid level detector D2 influences also the control unit S, whereby this closes the tube clamp V6 so that the connection between the measuring vessel M1 and the patient conduit L3 is interrupted, opens the tube clamps V4 and V2 so that the filled measuring vessel M1 is connected to the discharge conduit L2, and opens the tube clamp V5 so that the empty measuring vessel M2 is connected to the patient conduit L3. At the same time the two air valves V7 and V8 are switched to their opposite positions so that the measuring vessel M2 is put under vacuum and the measuring vessel M1 is put under overpressure. Consequently, used dialysis fluid is now sucked out from the patient through the patient conduit L3 into the measuring vessel M2, whereas the used dialysis fluid in the filled measuring vessel M1 is discharged under pressure from the vessel through the discharge conduit L2. The vacuum in the vacuum pipe 17 and the overpressure in the pressure pipe 15 are such that the discharging of dialysis fluid from the measuring vessel M1 requires less time than the filling of the measuring vessel M2 with used dialysis fluid. When the measuring vessel M1 is emptied down to its lower electrode E1, the fluid level detector D1 provides a signal to the control unit S, which closes the tube clamp V4 so that the connection between the vessel M1 and the discharge conduit L2 is interrupted. When somewhat later the vessel M1 is filled up to the upper electrode E4, the fluid level detector D4 provides a signal on the one hand to the two counters R1 and R2, which counts one more vessel of used dialysis fluid drained from the patient, and on the other hand to the control unit S, which then closes the tube clamp V5, opens the tube clamps V3 and V6 and returns the air valves V7 and V8 to their original positions, whereby the measuring vessel M1 is once more put under vacuum and the vessel M2 once more under overpressure. Consequently, used dialysis fluid is once more sucked from the patient through the patient conduit L3 into the empty vessel M1, whereas the used dialysis fluid in the filled vessel M2 is discharged under pressure into the discharge conduit L2. This alternating sequence with used dialysis fluid being sucked out from the patient through the patient conduit L3 into one of the measuring vessels and at the same time used dialysis fluid being discharged under pressure from the other measuring vessel through the discharge conduit L2 continues, until the time for the drain-phase as determined by the timer T2 runs out. However, as mentioned in the foregoing, the drain-phase cannot be interrupted until the control unit S has received signal from the output 27 of the counter R1, which signal indicates that during the drain-phase an equal number of measuring vessels filled with used dialysis fluid has been withdrawn from the patient as has been introduced into the patient during the preceding fill-phase. If the time determined by the timer T2 runs out before signal is provided on the output 27 of the counter R2, the drain-phase continues until said signal is provided. This means that the preset duration of the drain-phase is too short and preferably some sort of alarm should be generated so that a longer duration of the drain-phase can be set by means of the timer T2. In this connection it should be remembered that normally a somewhat larger fluid volume shall be withdrawn during the drain-phase than the fluid volume that has been introduced into the patient during the preceding fill-phase, as the object of the dialysis treatment is inter alia to remove excess water from the patient. If a larger number of measuring vessels filled with dialysis fluid is withdrawn from the patient during the drain-phase than was introduced into the patient during the preceding fill-phase, this difference will be indicated by the count in the counter R2 at the end of the drain-phase. At the end of the drain-phase the control unit S opens the gate G so that the count in the counter R2 is transferred to the store ST.

The drain-phase is always terminated with one of the two measuring vessels completely emptied down to its lower electrode El or E3 respectively. It can occur, however, that at the end of the drain-phase the other measuring vessel is only partially filled with used dialysis fluid withdrawn from the patient, as there is no more dialysis fluid in the patient to be withdrawn. This measuring vessel only partially filled with used dialysis fluid drained from the patient is not counted and is not discharged through the discharge conduit L2 but will instead at the beginning of the next fill-phase be pumped back into the patient through the patient conduit L3, also in this case without being counted. In this way it is obtained that at the end of the complete dialysis treatment the total error in the measured difference volume between the total volume of dialysis fluid pumped into the patient and the total volume of dialysis fluid withdrawn from the patient can at a maximum correspond to a portion of the volume of one measuring vessel.

The controlled electric current source 7 in the heating device for the heating of the fresh dialysis fluid being supplied through the supply conduit L1 is preferably controlled from the control unit S so as to supply a heating current to the pipe S only when the tube clamp V1 and one of the tube clamps V3 and V4 are open, that is only when dialysis fluid flows through the supply conduit L1. In this way overheating of the dialysis fluid is prevented. The temperature variations of the supplied dialysis fluid caused by the mode of operation of the heating device are equalized in that the dialysis fluid is mixed in the measuring vessel before it is supplied to the patient. As the dialysis fluid supplied through the conduit L1 is sucked into the measuring vessel under the action of a vacuum, an efficient de-airing of the fluid is also obtained.

As obvious from the foregoing, only the two measuring vessels M1 and M2 and the fluid conduits L1 to L8 together with the heating pipe 6 will come into contact with the dialysis fluid. As these components of the dialysis apparatus are very simple and inexpensive, they may preferably be designed as a dispensable set intended for "one-time" use only, which set is discarded after each completed dialysis treatment and replaced with a new set for the next dialysis treatment. In this way it is safeguarded against any infectious matter being transferred from one patient to another patient via the dialysis apparatus.

A dialysis apparatus according to the invention with the features described above may for instance be constructed as schematically illustrated in FIG. 2. This apparatus consists of a casing 30 enclosing the major portion of the electrical and mechanical components of the dialysis apparatus and having its topside designed as a control panel 31. Thus, this panel includes for instance the pressure gauge 22 indicating the draining vacuum during the drain-phase, the instrument I2 indicating the fluid balance of the patient and the instrument I1 indicating the stage of the current dialysis cycle in which the apparatus is operating. The panel 31 is also provided with a setting knob K1 for the vacuum regulator 21 determining the draining vacuum used during the drain-phase, a knob K2 for the setting of the counter R1, that is for presetting the volume of fresh dialysis fluid that is introduced into the patient during each fill-phase, a knob K3 for the setting of the timer T1, that is the duration of the dialysis-phase, and a knob K4 for the presetting of the timer T2, that is the minimum duration of the drain-phase. The control panel 31 includes also a number of pushbuttons B for various control functions as for instance start, stop etc. One of these pushbuttons operates the switch S3 mentioned in the foregoing, by means of which the instrument I2 may be temporarily connected to the counter R2.

The control panel 31 supports also the dispensable "one-time-use" set consisting of the two measuring vessels M1 and M2, the supply conduit L1 with its heating pipe 6, the discharge conduit L2, the patient conduit L3 and the branch conduits L4 to L8. For this purpose the control panel is provided with a holder 32 for the branch conduits L4 to L8. This holder cooperates also with pivotable hook-shaped arms or levers mounted on the control panel 31 and forming the tube clamps V1 to V6. For the heating pipe 6 two contact clamps are provided, which on the one hand support and fix the pipe and on the other hand form the electrical terminals 8 and 9 for the heating current source. The thermocouple 10 controlling this current source consists of two pins between which the pipe 6 has a tight fit and one of which consists of the same material as the pipe 6, whereas the other pin consists of another material which together with the material in the pipe 6 forms a thermocouple. For supporting the two measuring vessels M1 and M2 two support brackets 34 and 35 are provided on a column 33. These two brackets 34 and 35 can be opened and closed around the upper tube connections 2 and 4 and the lower tube connections 1 and 3 respectively of the measuring vessels. These support brackets 34 and 35 are also provided with necessary electrical terminals for the electrodes E1 to E6 of the measuring vessels so that these electrodes are automatically connected to the fluid level detectors D1 to D4 when the brackets 35 and 34 are closed. The column 33 supports also the moisture traps 11 and 12 and the germ filters 13 and 14. As can be seen from the drawing, the moisture trap 11 and the germ filter 13 for the measuring vessel M1 on the one hand and the moisture trap 12 and the germ filter 14 for the measuring vessel M2 on the other hand are combined to two assemblies, which can easily be removed and replaced with new sterilized assemblies before a new dialysis treatment.

In the embodiment of the invention described above there exists a certain danger that air might be forced into the peritoneal cavity of the patient. This may occur, if during a fill-phase the lower fluid level detector in the measuring vessel, which is currently under overpressure and from which dialysis fluid is being forced into the patient, fails to give indication when the measuring vessel is emptied. In this case also the dialysis fluid in the patient conduit will be forced into the patient and when also the patient conduit is emptied air will be forced into the patient. However, this can be prevented by means of a comparatively simple modification of the dialysis apparatus according to the invention described in the foregoing.

FIG. 3 illustrates schematically this modification, which concerns the connection between the two measuring vessels M1 and M2 on the one hand and the pressure pipe 15 and the vacuum pipe 17 on the other hand. With this modification only a predetermined limited air volume can be pumped into the measuring vessel which is currently under overpressure and this air volume is determined to be only slightly larger than the volume of the measuring vessel. The modification comprises an additional air valve V10 which is operated by the control unit S in the same manner as the valves V7 and V8 so as to change its state simultaneously with these valves. Further, the pressure pipe 15 is connected to the two valves V7 and V10 through a tank 37, the interior of which is divided by means of two bellows 38 and 39 into three separate chambers 37a, 37b and 37c. The two bellows 38 and 39 are resilient so that each bellow tends to assume its most expanded state when the same pressure exists on both sides of the bellow.

In the operating position of the valves V7, V8 and V10 illustrated in FIG. 3 the measuring vessel M1 is connected to the vacuum pipe 17 through the valve V8. The other measuring vessel M2 is connected to the chamber 37a in the tank 37 through the valve V7. The middle chamber 37b in the tank 37 is as always connected directly to the pressure pipe 15. Also the third chamber 37c is connected to the pressure pipe 15 through the valve V10 and the middle chamber 37b in the tank 37. Thus, in this state air is sucked out from the measuring vessel M1, whereas air is forced under pressure into the measuring vessel M2 from the chamber 37a, as the bellow 38 is compressed by the pressure in the chamber 37b. The bellow 39 expands to its most expanded state so that the chamber 37c expands, as the same air pressure exists in both chambers 37b and 37c on both sides of the bellow 39. It is appreciated that the largest air volume that can be forced into the measuring vessel M2 corresponds to the initial maximum volume of the chamber 37a. The flow of air under pressure into the measuring vessel M2 will consequently be automatically interrupted even if the lower fluid level detector in this measuring vessel should fail to provide an output signal.

In the opposite operating state of the valves V7, V8 and V10 the measuring vessel M2 is connected to the vacuum pipe 17 through the valve V8, whereas the measuring vessel M1 is connected to the chamber 37c in the tank 37 through the valve V10. The chamber 37a is connected to the pressure pipe 17 through the valve V7 and the middle chamber 37b in the tank 37. In this state consequently the bellow 39 and thus also the chamber 37c are being compressed, whereas the bellow 38 and thus also the chamber 37a are expanded to the maximum volume.

Claims

What we claim is:

1. An apparatus for peritoneal dialysis comprising two identical measuring vessels (M1,M2) each vessel being provided with a lower fluid connection (1,3) at its lower end and an upper air connection (2,4) at its upper end each vessel further having a lower fluid level detector (E1,D1,E3,D3) adjacent said lower fluid connection and an upper fluid level detector (E2,D2,E4,D4) adjacent said upper air connection; an air pump (16) having a delivery side and a suction side; air valve means (V7,V8) alternatingly connecting the delivery side (15) of said air pump to said upper air connection of one of said measuring vessels and at the same time the suction side (17) of said air pump to said upper air connection of the other measuring vessel or vice versa respectively; a patient conduit (L3) provided for connection to a patient to be treated; first fluid valve means (V5,V6) for connecting said patient conduit to said lower fluid connection (1,3) of alternatingly the one or the other measuring vessel respectively; a supply conduit (L1) for fresh dialysis fluid and a discharge conduit (L2) for used dialysis fluid; second fluid valve means (V1,V2,V3,V4) for connecting alternatingly said supply conduit or said discharge conduit to said lower fluid connection (1,3) of alternatingly the one or the other measuring vessel respectively; and a programmed control unit (S) responsive to said fluid level detectors (D1 to D4) for operating said air valve means and said first and second fluid valve means in such a manner that to introduce fresh dialysis fluid to the patient being treated, fresh dialysis fluid is sucked into one of said measuring vessels from said supply conduit through said second fluid valve means until said upper fluid level detector of said measuring vessel indicates that the vessel is filled and at the same time dialysis fluid is discharged under pressure from the other measuring vessel to said patient conduit through said first fluid valve means until said lower fluid level detector of said other vessel indicates that said other vessel is emptied, whereafter fresh dialysis fluid is sucked into said emptied measuring vessel from said supply conduit through said second fluid valve means and at the same time dialysis fluid is discharged under pressure from the filled measuring vessel to said patient conduit through said first fluid valve means, and so on in alternating sequences, whereas to withdraw used dialysis fluid from the patient being treated used dialysis fluid is sucked into one of said measuring vessels from said patient conduit through said first fluid valve means until said upper fluid level detector of said vessel indicates that said vessel is filled and at the same time dialysis fluid is discharged under pressure from the other measuring vessel to said discharge conduit through said second fluid valve means until said lower fluid level detector of said other vessel indicates that said other vessel is emptied, whereafter used dialysis fluid is sucked into the emptied measuring vessel from said patient conduit through said first fluid valve means and at the same time dialysis fluid is discharged under pressure from the filled measuring vessel to said discharge conduit through said second fluid valve means, and so on in alternating sequences.

2. An apparatus as claimed in claim 1, comprising a first reversible counter (R2) responsive to said fluid level detectors (D2,D4) for counting in its one direction, when fresh dialysis fluid is being introduced to the patient, the number of measuring vessels filled with fresh dialysis fluid being discharged under pressure into said patient conduit and for counting in its opposite direction, when used dialysis fluid is being withdrawn from the patient, the number of measuring vessels filled with used dialysis fluid being sucked out from said patient conduit.

3. An apparatus as claimed in claim 2, comprising storing means (ST) and gating means (G) controlled by said control unit (S) for transferring the count in said first counter (R2) to said storing means after used dialysis fluid has been withdrawn from the patient and before fresh dialysis fluid is once more introduced into the patient.

4. An apparatus as claimed in claim 3, comprising display means (I2) for displaying the count stored in said storing means (ST).

5. An apparatus as claimed in claim 2, comprising display means for displaying the instantaneous count in said first counter (R2).

6. An apparatus as claimed in claim 1, comprising a second counter (R1) being presetable to a predetermined variable count and responsive to said fluid level detectors (D2,D4) when fresh dialysis fluid is being introduced into the patient to count the number of measuring vessels filled with dialysis fluid being introduced into the patient and connected to said control unit (S) to cause said control unit to interrupt the introduction of fresh dialysis fluid into the patient when it reaches said predetermined count.

7. An apparatus as claimed in claim 6, wherein said second counter (R1) is responsive to said fluid level detectors (D2,D4) also when used dialysis fluid is being withdrawn from the patient to count the number of measuring vessels filled with used dialysis fluid being withdrawn from the patient and is provided to prevent said control unit (S) from interrupting the withdrawal of used dialysis fluid from the patient before it has counted a number of measuring vessels equal to said predetermined count.

8. An apparatus as claimed in claim 2, wherein said control unit (S) is provided to interrupt the introduction of fresh dialysis fluid to the patient at a stage when both measuring vessels (M1,M2) are empty.

9. An apparatus as claimed in claim 1, comprising first presetable timing means (T1) connected to said control unit (S) for determining a time interval between an introduction of fresh dialysis fluid into the patient and a subsequent draining of said dialysis fluid from the patient.

10. An apparatus as claimed in claim 1, comprising second presetable timing means (T2) connected to said control unit (S) for determining a minimum duration of the draining of used dialysis fluid from the patient.

11. An apparatus as claimed in claim 1, wherein said upper air connections (2,4) of said measuring vessels (M1,M2) are connected to said air valve means (V7,V8) through moisture traps (11,12) and germ filters (13,14).

12. An apparatus as claimed in claim 1, comprising a heating device for heating fresh dialysis fluid flowing through said supply conduit (L1) to a predetermined temperature, said heating device including a metal pipe (6) forming a portion of said supply conduit, a controlled electric current source (7) having its output terminals connected to opposite ends of said metal pipe, and a temperature transducer (10) for measuring the temperature of said metal pipe at a point adjacent the downstream end of the pipe and for controlling the output current of said current source.

13. An apparatus as claimed in claim 1, wherein said two measuring vessels (M1,M2), said patient conduit (L3), said supply conduit (L1), said discharge conduit (L2) and any connecting conduits (L4 to L8) between said conduits and said measuring vessels form a dispensable assembly intended only for one-time use, said dispensable assembly being removably mounted in a predetermined position on an apparatus panel (31) provided with a number of tube clamps operated by said control unit (S) for clamping said conduits mounted on said apparatus panels so as to form said first and second fluid valve means, said conduits consisting of flexibly compressible tubes at least opposite to said tube clamps.

14. An apparatus as claimed in claim 13, wherein said lower fluid connections (1,3) of said two measuring vessels (M1,M2) are connected to said patient conduit (L3) through a first branch conduit (L4,L5) each, said first branch conduits including each one stop valve (V6,V5) forming said first fluid valve means, and are connected to a junction (L8) through a second branch conduit (L6, L7) each, said second branch conduits including each one stop valve (V4,V3), and said supply conduit (L1) and said discharge conduit (L2) are connected through each one stop valve (V1,V2) to said junction (L8), said last mentioned stop valves together with said stop valves in said second branch conduits forming said second fluid valve means.