Device for extracorporeal blood treatment and device for collecting blood clots

Description

[0001] The invention relates to a device for extracorporeal blood treatment comprising a blood treatment unit having at least one compartment. Furthermore, the invention relates to a device for collecting blood clots for a blood line for supplying or removing blood to or from a blood treatment unit of an extracorporeal blood treatment device.

[0002] In chronic blood purification therapy procedures such as hemodialysis, hemofiltration, and hemodiafiltration, blood is pumped through an extracorporeal blood circuit. In hemodialysis, the blood to be treated flows through the blood chamber of a dialyzer divided by a semipermeable membrane into a blood chamber and a dialysis fluid chamber. In a dialysis fluid system, dialysis fluid flows through the dialysis fluid chamber of the dialyzer. The extracorporeal blood circuit has an arterial line leading to the blood chamber and a venous line branching off from the blood chamber. The known blood treatment devices have a blood pump, which is usually located upstream of the dialyzer's blood chamber, to ensure sufficient blood flow in the extracorporeal blood circuit.

[0003] An arteriovenous fistula is often created surgically to access the patient's vascular system. The use of an implant is also possible. The fistula's perfusion is important for its functionality. If the fistula flow falls below a critical level, the risk of fistula thrombosis increases with the possible loss of vascular access, which represents a significant complication in dialysis treatment (W. Bay et al.: Color Doppler flow predicts PTFE graft failure, J. Am. Soc. Nephrol. 5: 407 (1994)). If the fistula flow during dialysis treatment is lower than the extracorporeal blood flow (QB), local fistula recirculation occurs, whereby a fraction of the dialyzed blood returned to the fistula via the venous blood line is returned to the dialyzer via the arterial blood line. Fistula recirculation (RA) causes a significant reduction in dialysis efficiency (F.Gotch: "Models to predict recirculation and its effect on treatment time in single-needle dialysis" First Intl. Symposium on Single-Needle Dialysis, Ed.: S. Rignoir. R. Vanholder and P. Invanovich, Cleveland, ISAO Press, 1984, page 305 ff.).

[0004] Due to their clinical significance, various methods are known for determining blood flow in vascular access (shunt flow) or recirculation. Many methods are based on measuring a physical or chemical parameter of the blood that is altered in the extracorporeal blood circuit. The physical or chemical parameter can be, for example, the temperature, density, or electrolyte composition of the blood. The parameter can be altered in the extracorporeal blood circuit directly or indirectly by a change in a physical or chemical parameter in the dialysis fluid system.

[0005] A method for shunt flow measurement known as thermodilution is described in EDTNA-ERCA Journal 19, 6 (1993). This known method initiates a brief temperature drop in the dialysis fluid system, which is then transferred to the venous branch of the extracorporeal circuit and leads to a detectable temperature jump in the arterial branch of the extracorporeal circuit when recirculation occurs.

[0006] DE 195 28 907 C1 describes a method for determining cardiopulmonary recirculation based on two consecutive measurements of the recirculation fraction, performed before and after reversing blood flow in the extracorporeal circuit. In principle, reversing blood flow can be achieved by swapping the arterial and venous patient connections. However, manually swapping the patient connections is not without its problems from a hygiene and safety perspective. Therefore, numerous devices for blood tubing systems have been developed that automatically reverse the flow direction by cross-connecting the relevant tubing sections of the tubing system. However, the flow direction is maintained in the part of the extracorporeal circuit that includes the dialyzer.Therefore, the protective systems located in this part can be used both before and after the reversal of blood flow.

[0007] A valve device for automatically reversing the flow direction is known, for example, from WO 2014 / 074231 A1.

[0008] DE 195 28 907 C1 proposes, as an alternative to the known valve devices for automatically reversing the flow direction, simply reversing the flow direction of the blood pump in the extracorporeal blood circuit. However, this option has not yet been used in practice, as the operation of an extracorporeal blood treatment device with a dialyzer through which blood flows in different directions is not without its problems from a safety perspective.

[0009] WO 2012 / 022456 A1 discloses a device for detecting or monitoring solids or gas bubbles in a fluid. WO 2012 / 022456 A1 points to the problem of flow reversal caused by changing the flow direction of a blood pump. The solution to this problem is seen in monitoring the blood flow for solids or gas bubbles. If solids or gas bubbles are detected in the blood, protective measures should be provided, such as interrupting the blood flow.

[0010] WO 2010 / 121750 A1 describes a method for removing blood from an extracorporeal blood circuit after completion of blood treatment. WO 2010 / 121750 A1 proposes inserting a clot catcher into the arterial section of the extracorporeal blood circuit.

[0011] A known clot catcher is described, for example, in WO 2010 / 121743 A1.

[0012] The invention is based on the object of enabling a measurement of a hemodynamic parameter without the use of the known valve devices for the automatic reversal of the flow direction, which cause an automatic reversal of the flow direction by a cross-connection of the relevant hose line sections of the hose line system.

[0013] This problem is solved by the features of the independent patent claims. The dependent claims relate to preferred embodiments of the invention.

[0014] The device for extracorporeal blood treatment according to the invention comprises: a blood treatment unit having at least one compartment, a first blood line connected to a port of the compartment and having a first patient port, a second blood line connected to a port of the compartment and having a second patient port, a blood pump for pumping blood, a device for measuring a physical or chemical parameter, a control and evaluation unit connected to the blood pump and the device for measuring a physical or chemical parameter, which is configured such that the blood pump is operated in a first operating mode with a normal blood flow, so that blood flows from the first patient port to the blood treatment unit and from the blood treatment unit to the second patient port, the blood pump is operated in a second operating mode with a reversed blood flow,so that blood flows from the second patient connection to the blood treatment unit and from the blood treatment unit to the first patient connection, and the hemodynamic parameter is determined from the measured physical or chemical characteristic, at least in the case of reverse blood flow. To prevent the formation of blood clots in the extracorporeal blood circuit, an anticoagulant substance, usually heparin, is often administered either continuously during dialysis or as an initial bolus. It is usually added upstream of the dialyzer. In addition to the systemic effect of the anticoagulant in the patient, a possible mechanism of action is the deposition of this substance on the surfaces of the extracorporeal system, particularly on the lumen of the dialyzer fibers.

[0015] The dialyzer used in extracorporeal blood treatment presents an insurmountable obstacle to clot formation due to the diameter of the hollow fibers, which are less than 0.2 mm. Therefore, clots forming upstream of the dialyzer cannot reach the area downstream of the dialyzer and thus cannot reach the patient. However, blood clots located downstream of the dialyzer can be infused. This is independent of the direction of blood flow through the dialyzer.

[0016] In known blood treatment devices, clots forming in the blood on the way from the dialyzer to the patient are generally trapped with a clot trapping device located downstream of the dialyzer in the venous blood line of the extracorporeal tubing system, upstream of the venous cannula. This device is also referred to as a clot trap.

[0017] In practice, it has been shown that reversing the flow direction of the blood pump for a measurement to determine a hemodynamic parameter poses a risk of blood clots entering the patient, even though the dialyzer retains blood clots forming upstream of the dialyzer. It has been shown in practice that blood clots accumulate at the dialyzer inlet during operation with "normal" blood flow. When the blood flow is reversed, these blood clots are then flushed toward the patient.

[0018] The device for extracorporeal blood treatment according to the invention therefore provides a device for collecting blood clots at least in the first blood line. During blood treatment with a "normal" blood flow, a second device for capturing blood clots, which can be provided in the second blood line, can retain blood clots forming downstream of the dialyzer. During a "reverse" blood flow, the device for collecting blood clots in the first blood line retains blood clots that may have previously accumulated at the inlet of the blood treatment unit. Consequently, there is no risk of infusion of blood clots when the flow direction of the blood pump is switched from a "normal" blood flow to a "reverse" blood flow for determining the hemodynamic parameter.

[0019] For the invention, it is irrelevant which hemodynamic parameters are determined based on one or more measurements during reversed blood flow and how the hemodynamic parameters are determined. It is also irrelevant whether blood-side or dialysate-side variables are measured. Instead of the physical or chemical property of the blood in the blood line, a parameter in the dialysate that correlates with the physical or chemical parameter in the blood line can also be measured. The invention therefore relates to all methods in which a chemical or physical parameter is measured before and after the reversal of flow direction, or only during reversed blood flow, in order to determine the hemodynamic parameter.

[0020] The disclosure relates, for example, to all methods in which a chemical or physical parameter in the blood in one branch of the extracorporeal blood circuit is changed before and after the reversal of the flow direction and the change in the chemical or physical parameter in the blood attributable to the change in the chemical or physical parameter in this branch is detected in another branch of the extracorporeal blood circuit or in the dialysate.

[0021] To determine the hemodynamic parameter, the course of the observable temporal change in the physical or chemical parameter in the blood-side or dialysate-side line system can be measured. A specific application is the determination of recirculation using known methods that require a reversal of the flow direction. The hemodynamic parameter can be the recirculation in the fistula or the shunt flow.

[0022] The blood treatment unit can be any unit for performing hemodialysis, hemofiltration, hemodiafiltration, apheresis, or similar procedures. In the case of hemodialysis, hemofiltration, or hemodiafiltration, the blood treatment unit (dialyzer) has a first and a second compartment separated by a semipermeable membrane. However, if the blood treatment is not based on diffusive or convective mass transfer, for example, adsorption on functionalized surfaces, a second compartment is not required.

[0023] After the direction of blood flow has been reversed, a clot trapping device in the first blood line can be used to retain blood clots that have formed in the blood upstream of the compartment of the blood treatment unit before the direction of blood flow was reversed.

[0024] Furthermore, practice has shown that the first clot trapping device in the first blood line leads to an increase in flow resistance during "normal" blood flow. This is disadvantageous in that the first clot trapping device is actually not necessary for "normal" blood flow, as the blood clots are already effectively retained by the blood treatment unit.

[0025] One embodiment therefore provides a flow-direction-dependent device for capturing blood clots. In the preferred embodiment, at least one of the two blood clot capture devices is flow-direction-dependent. In particular, the first blood clot capture device, provided upstream of the dialyzer during "normal" blood flow, is only fully effective when the flow direction is reversed. Otherwise, the blood flow through the blood clot capture device is at least not significantly impaired. Therefore, not only is an increase in blood flow resistance avoided, but the risk of blood damage or the creation of stagnation sites, which in turn can lead to the formation of blood clots, is also reduced.

[0026] In the device for extracorporeal blood treatment according to the invention, the device for collecting blood clots comprises a housing body with a first connection and a second connection, and a sieve body arranged in the blood flow path between the two connections for catching the blood clots. The sieve body can be designed in various ways, as long as blood clots are effectively retained. Such filter sieves are state of the art. The device for collecting blood clots is designed such that a flow path bypassing the sieve body is formed in the housing body when blood cannot be collected in the "normal"

[0027] Instead of flowing in at the first port and out at the second port in the same direction, the device flows in at the second port and out at the first port in the "reverse" direction. Since at least a portion of the blood flow bypasses the mesh, flow resistance is reduced. However, if blood flows in at the first port and out at the second port in the "normal" flow direction, a flow path bypassing the mesh does not form in the housing body. In this flow direction, the device can effectively retain blood clots.

[0028] A further embodiment provides that the sieve body is designed as a valve body, and a valve seat for the sieve body is formed in the housing body. The sieve body is movably arranged in the housing body such that it rests on the valve seat when blood flows in the "normal" flow direction at the first port and flows out at the second port, and is lifted off the valve seat when blood flows in at the second port and flows out at the first port, so that a flow path bypassing the sieve body is formed in the housing body. The movement of the valve body can occur solely through the back pressure when the blood flows toward the valve body.

[0029] The sieve body can only sit on the valve seat in one flow direction by a special shape of the housing and / or by limiting the area in which the sieve body can move in the housing.

[0030] In one embodiment, the sieve body is movably arranged in the blood flow path between the first and second ports, wherein the movement of the sieve body in the housing body is limited to a range between a first and a second end position. The limitation of the movement range of the sieve body in the blood flow path between the first and second ports can be achieved with at least one elongated, flexible fixing element, one end of which is connected to the sieve body and the other end of which is connected to the housing body. In a preferred embodiment, several elongated, flexible fixing elements are provided, which are arranged around the circumference of the sieve body.This allows the sieve body to be sufficiently fixed centrally in the middle of the housing body from all sides, whereby the blood can flow unhindered between the fixing elements through the housing body when the sieve body is not sitting on the valve seat.

[0031] Another embodiment provides that the housing body has a circular cross-section, and the sieve body has a holding part with a circular cross-section into which a sieve is inserted. The sieve can be designed as a flat, disc-shaped body or in the shape of a thimble. The thimble-shaped design of the sieve has the advantage of a larger surface area. This prevents the sieve from becoming clogged as quickly.

[0032] The first and second connectors of the blood clot collection device can, for example, be designed as a connector part of a Luer or Luer / Lock connector, in order to connect the device to the corresponding tubing sections of the blood tubing system or the patient connections (puncture cannulas). In this case, the blood clot collection device can be provided together with the blood tubing system or without the blood tubing system. The blood clot collection device can be part of the tubing of the blood tubing system or the puncture cannula. For example, the connectors can be glued or welded to the tubing or the cannula.

[0033] In one embodiment, a first device for collecting blood clots is provided in the first blood line and a second device for collecting blood clots is provided in the second blood line.

[0034] When the section of the first blood line connected to the first patient connection is connected to the second connection of the housing body of the first clot collection device, and the section of the first blood line connected to the connection of the blood treatment unit is connected to the first connection of the housing body of the first clot collection device, the blood can flow past the filter screen in the "normal" flow direction through the first clot collection device. In the "reverse" flow direction, however, the first device retains blood clots.

[0035] When the portion of the second blood line connected to the blood treatment unit is connected to the first port of the housing body of the second clot collection device, and the portion of the second blood line connected to the second patient port is connected to the second port of the housing body of the second clot collection device, the second device retains blood clots in the "normal" flow direction. In the "reverse" flow direction, however, the second device does not retain blood clots.

[0036] Particularly if the flow reversal occurs late in the blood treatment process, there is a risk that a relatively large amount of blood clots may have accumulated upstream of the blood treatment unit, which could clog the first device for capturing blood clots after a flow reversal. A further embodiment therefore provides a first pressure sensor for measuring the pressure in the first blood line, which is connected to the control and evaluation unit, so that the control and evaluation unit receives the measured values ​​from the first pressure sensor. The control and evaluation unit is configured such that the pressure measured by the first pressure sensor in the second operating mode is compared with a predetermined limit value. If the pressure measured by the first pressure sensor exceeds the predetermined limit value, a signal indicating clogging of the device is generated, which can trigger a further event.The limit value can be an absolute limit value stored in a memory of the control and evaluation unit or a blood flow-dependent limit value calculated by the control and evaluation unit taking into account the specified blood flow rate.

[0037] In a further embodiment, the control and evaluation unit is configured such that the blood pump switches from "reverse" blood flow to "normal" blood flow when the signal is generated. If a filter blockage is detected, the control and evaluation unit can also prevent the flow reversal for the remainder of the blood treatment. Furthermore, a user control can be designed such that the flow reversal block can be released by confirming that any clots have since dissolved due to the administration of anticoagulants. An alarm unit and / or display unit can also be connected to the control and evaluation unit so that the alarm unit and / or display unit receives the signal.

[0038] An alternative embodiment provides that a first pressure sensor for measuring the pressure in the first blood line and a second pressure sensor for measuring the pressure in the second blood line are connected to the control and evaluation unit, so that the control and evaluation unit receives the measured values ​​from the first and second pressure sensors. In this embodiment, the control and evaluation unit is configured such that the pressure measured by the first pressure sensor in the second operating mode is compared with the pressure measured by the second pressure sensor in the first operating mode. If the pressure measured by the first pressure sensor exceeds the pressure measured by the second pressure sensor by a predetermined amount or factor, a signal indicating a blockage is generated.The pressure is preferably measured with the first and second pressure sensors at the same blood flow rate so that the blood flow cannot influence the monitoring of the blood clot trapping device.

[0039] In the following, various embodiments of the invention are explained in more detail with reference to the drawings.

[0040] They show: Fig. 1An embodiment of the device according to the invention in a highly simplified schematic representation, Fig. 2Aa first embodiment of a device for catching blood clots in the flow direction, Fig. 2Ba first embodiment of a device for catching blood clots against the flow direction, Fig. 2Cthe sieve body of the device for catching blood clots in plan view, Fig. 3Aa second embodiment of a device for catching blood clots in the flow direction and Fig. 3Ba second embodiment of a device for catching blood clots against the flow direction.

[0041] Fig. 1 shows, in a highly simplified schematic representation, the components of the blood treatment device essential to the invention, which in the present embodiment is a hemodialysis device. The blood treatment device has a blood treatment unit 1, which can be a dialyzer divided by a semipermeable membrane 2 into a first compartment 3 (blood chamber) and a second compartment 4 (dialysate chamber). The extracorporeal blood circuit I comprises a first blood line 5, which is connected to a first connection of the first compartment 3, the first compartment 3, and a second blood line 7, which is connected to a second connection of the first compartment 3. The first and second blood lines 5, 7 are hose lines of a disposable blood tubing system.A first patient connection 8 (puncture cannula) is located at the end of the first blood line 5, and a second patient connection 9 (puncture cannula) is located at the end of the second blood line 7. The blood is pumped by a blood pump 10, which is provided in the first blood line 5.

[0042] To perform the blood treatment, the first puncture cannula 8 is connected to an upstream part 11A of the vascular access 11, while the second puncture cannula 9 is connected to a downstream part 11B of the vascular access 11, so that the patient's blood flows through the first blood line 5, the first compartment 3 of the blood treatment unit 3, and the second blood line 7. This case is referred to as "normal" blood flow. The blood pump 10 then pumps in the "normal" direction. The upstream part 11A of the vascular access 11 thus represents the arterial part of the fistula, the first blood line 5 represents the arterial blood line, the second blood line 7 represents the venous blood line, and the downstream part 11B of the fistula represents the venous part of the fistula.

[0043] To measure the hemodynamic parameter, a reversal of the flow direction is required, so that the blood flows from the downstream part 11B of the vascular access 11 through the second blood line 7, the first compartment 3 of the blood treatment unit 1, and the first blood line 5 to the upstream part 11A of the vascular access 11. This case is referred to as "reverse" blood flow. The blood pump 10 then pumps in the "reverse" flow direction.

[0044] The blood treatment device has a central control and evaluation unit 12 for controlling all components of the device. The control and evaluation unit 12 can, for example, comprise a general processor, a digital signal processor (DSP) for continuously processing digital signals, a microprocessor, an application-specific integrated circuit (ASIC), an integrated circuit consisting of logic elements (FPGA), or other integrated circuits (IC) or hardware components to execute the individual method steps for controlling the blood treatment device. A data processing program (software) can run on the hardware components to carry out the method steps. A plurality or combination of the various components is also possible.

[0045] The control and evaluation unit 12 is configured such that the individual components of the blood treatment device are controlled for carrying out the blood treatment and the measurements for determining a hemodynamic parameter of the blood treatment are carried out.

[0046] The blood treatment device has a first pressure sensor 13A for measuring the pressure in the first blood line 5 between the blood pump 10 and the first patient connection 8 and a second pressure sensor 13B for measuring the pressure in the second blood line 7 between the first compartment 3 and the second patient connection 9.

[0047] The measurements for determining a hemodynamic parameter of the blood treatment can be performed in the extracorporeal blood circuit I. A first measuring device 14A is provided for measuring a physical or chemical property of the blood in the first blood line, and a second measuring device 14B is provided for measuring a physical or chemical property of the blood in the second blood line. The pressure sensors 13A, 13B and the devices 14A, 14B for measuring a physical or chemical property of the blood are connected to the control and evaluation unit 12 via data lines (not shown).A first clot trapping device 15A is provided in the first blood line 5 between the first patient connection 8 and the first device 14A for measuring a physical or chemical property, and a second clot trapping device 15B is provided in the second blood line 7 between the second device 14B for measuring a physical or chemical property and the second patient connection 9. The clot trapping devices 15A, 15B are described with reference to FIG. Figuren 3A, 3B and 4A and 4B are described in more detail below. The blood clot traps 15A, 15B can also be provided in other sections of the first and second blood lines 5, 7. Furthermore, the blood treatment device has further monitoring and safety devices 16A, 16B, only schematically shown, which are functional in both the "normal" and "reverse" flow directions. These monitoring and safety devices include 16A, 16B, an air separation chamber, an air detector, and a shut-off device in the first and second blood lines. The air separation chambers can have inlet and outlet lines arranged below the liquid level. Ultrasonic sensors can be used to detect air.

[0048] The dialysis fluid system II comprises a device 17 for processing dialysis fluid at a predetermined temperature. The fresh dialysis fluid flows via a dialysis fluid supply line 18 into the second compartment 4, and the used dialysis fluid flows from the second compartment 4 of the blood treatment unit 1 via a dialysis fluid discharge line 19 to the device 17 for processing dialysis fluid. The device 17 for processing dialysis fluid is connected to the control and evaluation unit 12 via a data line (not shown), so that the control and evaluation unit 12 can control the temperature and composition of the dialysis fluid.

[0049] Measurements for determining a hemodynamic parameter of blood treatment can be performed in the dialysis fluid system II instead of the extracorporeal blood circuit I. These procedures are state-of-the-art. For example, fistula flow can be determined by measuring clearance during normal and reversed blood flow.

[0050] In the case of hemofiltration, a device for processing dialysis fluid and a dialysis fluid supply line leading to the second compartment of the blood treatment unit are not required. Ultrafiltrate can be withdrawn from the second compartment of the blood treatment unit via the dialysis fluid discharge line. For blood treatment in which diffusive or convective exchange does not occur, a second compartment and a dialysis fluid supply and discharge line are also not required. The only decisive factor for the invention is that the determination of the hemodynamic parameter requires a flow reversal. It is not critical for the invention whether a physical or chemical parameter is changed for the determination of the hemodynamic parameter in the blood. The measurements of the physical or chemical parameter can be performed on the blood side or the dialysate side.

[0051] In the present embodiment, the device 17 for processing dialysis fluid also functions as a device for changing a physical or chemical property of the blood. For this purpose, the device 17 for processing dialysis fluid briefly changes the temperature or composition of the dialysis fluid in the dialysis fluid system II, which results in a change in a physical or chemical parameter in the extracorporeal blood circuit I. The change in the physical or chemical property in the blood, for example the temperature of the blood (temperature turbobolus), is measured with the first or second measuring device 14A, 14B in the first and second blood lines 5, 7. Alternatively, for example,The hemodynamic parameter, in particular the shunt flow, can be determined from the conductivity curve of the dialysis fluid, which can be measured using conductivity cells (not shown) in the dialysis fluid supply line 18 and the dialysis fluid discharge line 19. Alternatively, the change in the physical or chemical properties of the blood can also be achieved by external elements such as Peltier elements attached to the blood tubing system or the infusion of a physiological solution via an addition point located in the first or second blood line.

[0052] The direction of rotation and flow rate of the blood pump 10 can be controlled by the control and evaluation unit 12. For this purpose, the pressure values ​​of the pressure sensors 13A, 13B can be used to determine and correct the effective blood flow in a known manner based on the pump's rotational speed and the negative pressure on the respective suction side.

[0053] The temporal progression of the physical or chemical properties of the withdrawn blood and the returned blood is measured using the measuring devices 14A, 14B provided on the blood tubing system and transmitted to the control and evaluation unit 12. The measuring devices 14A, 14B can be, for example, temperature sensors, optical or spectroscopic sensors, or density sensors, such as ultrasonic sensors. Conductivity measuring cells can also be used to determine quantities that correlate with the relevant physical or chemical properties of the blood. Instead of the blood-side physical or chemical parameters, dialysate-side physical or chemical parameters that correlate with the blood-side physical or chemical parameters can also be measured.For this purpose, measuring sensors for measuring the parameters in the dialysis fluid system II, for example in one or both dialysis fluid lines 18 and 19, can be provided.

[0054] In the present embodiment, the flow in the vascular access (shunt flow) is determined as a hemodynamic parameter. The shunt flow can be determined using the method described in detail in DE 195 28 907 A1.

[0055] The shunt flow measurement process is controlled by the control and evaluation unit 12. Initially, the blood pump 10 is operated in the "normal" flow direction. The temperature or composition of the dialysis fluid is briefly changed at "normal" blood flow. The temperature bolus or conductivity jump is transferred to the extracorporeal blood circuit I as a result of the heat exchange at the dialyzer. The measuring devices 14A, 14B in the first and second blood lines 5, 7 record the changes in the physical or chemical parameters in the first and second blood lines. The measured values ​​are stored in a memory unit 12A of the control and evaluation unit 12. The blood pump 10 is then operated in the "reverse" flow direction.The temperature or composition of the dialysis fluid is briefly changed during "reverse" blood flow, and the temperature or composition of the dialysis fluid in the first and second blood lines is measured. The measured values ​​are again stored in the memory unit 12A of the control and evaluation unit 12. The control and evaluation unit 12 then calculates the shunt flow based on the measured values ​​of the measuring devices using a suitable sequence control and corresponding evaluation methods and displays the result on a display unit 20 or outputs the result via another form of communication, for example, via a network. Any error messages or instructions can also be transmitted to the user on the display unit 20.Instead of a display unit, an alarm unit can also be provided, which provides an acoustic, visual, or tactile alarm, for example, in the event of a filter blockage. The evaluation method for calculating the shunt flow from the measured values ​​is described in DE 195 28 907 A1, to which express reference is made.

[0056] During the reversal of flow direction, the control and evaluation unit 12 ensures that the protective devices 16A, 16B provided for dialysis treatments are adapted to the reversal of the blood flow direction. This includes, in particular, the arterial and venous pressure monitoring, whose functions are reversed during the flow reversal. While there is a negative pressure on the suction side of the blood pump ("arterial"), the pressure on the return side ("venous") is positive. At the same time, the venous pressure serves to detect any needle disconnections. The control and evaluation unit is therefore configured such that the specified arterial and venous pressure limit windows are reversed during a flow reversal.With the algorithms for detecting a needle disconnection, which are based on dynamic signal analysis and / or monitor for the absolute undershoot of a lower pressure threshold on the return side, the readings from the arterial sensor are now evaluated during normal operation instead of the readings from the venous sensor. In addition, after flow reversal, monitoring for air infusion is performed on the arterial side, which is used in normal operation.

[0057] In the present embodiment, the measurement is initially performed at a "normal" blood flow. However, it is also possible to initially perform the measurement with a "reverse" blood flow.

[0058] The structure of the devices provided in the first and second blood lines for catching blood clots is described in detail below.

[0059] The Figuren 2A and 2Bshow a simplified schematic representation of a section through a first embodiment of the blood clot catcher 15A or 15B, which is only effective in one flow direction. In the opposite flow direction, the blood clot catcher is not effective, so that the flow resistance is lower. The flow direction is shown in the Figuren 2A and 2B marked with an arrow.

[0060] The blood clot catcher comprises a preferably rotationally symmetrical housing body 21 having a first connection 22 and a second connection 23. The connections can be Luer or Luer / Lock connections, or connecting pieces that are welded or glued to the tubing sections 24, 25 of the blood tubing system. Located within the housing body 21 is a flat, circular sieve body 26, which has an annular retaining part 27 into which a circular sieve 28 is inserted ( Fig. 2C ). The mesh size of the sieve 28 is dimensioned such that blood clots are retained. The annular holding part 27 has a smaller outer diameter than the inner diameter of the housing body 21, so that the holding part 27 or the sieve body 26 can be laterally flowed around by blood. The sieve body 26 is arranged movably in the flow path of the blood centrally in the housing body 21. For this purpose, the holding part 27 is suspended in the housing body 21 on flexible fixing elements 29, in particular threads, which are arranged distributed around the circumference. One end of the threads 29 are connected to the holding part 27 and the other ends of the threads are fastened to the wall of the housing body 21. The length of the threads 29 is dimensioned such that the sieve body 26 can be positioned between the Fig. 2A shown first position and the one in Fig. 2B shown second position can move freely in the center of the housing body 21.

[0061] On the side facing the second connection 23, a valve seat 30 is formed in the housing body 21, on which the holding part 27 of the sieve body 26 rests in a sealing manner in the second position ( Fig. 2A ). On the side facing the first connection 22, a valve seat is not formed in the housing body 21, so that the sieve body 26 can be laterally flowed around by blood ( Fig. 2B ). On the side of the valve seat 30, the housing body 21 has a funnel shape and on the opposite side a dome shape.

[0062] When blood flows into the housing body 21 at the first port 22, the strainer body 26 moves into the second position due to the dynamic pressure, so that the strainer body 26 rests on the valve seat 30 and blood clots are retained. However, when blood flows into the housing body 21 at the second port 23, the strainer body 26 moves into the first position due to the dynamic pressure, so that the blood flows around the strainer body. This creates a flow path bypassing the strainer body, thus reducing flow resistance.

[0063] The first blood clot catcher 15A is arranged in the first blood line 5 such that the section of the first blood line 5 connected to the first patient connection 8 is connected to the second connection 23 of the housing body 21 and the section of the first blood line 5 connected to the connection of the blood treatment unit 1 is connected to the first connection 22 of the housing body 21, so that the blood can flow past the filter screen 28 through the first blood clot catcher 15A in the "normal" flow direction, but blood clots are retained in the "reverse" flow direction.

[0064] The second blood clot catcher 15B is arranged in the second blood line 7 such that the section of the second blood line 7 connected to the second patient connection 9 is connected to the second connection 23 of the housing body 21 and the section of the second blood line 7 connected to the connection of the blood treatment unit 1 is connected to the first connection 22 of the housing body 21, so that in the "normal" flow direction, blood clots are retained by the second blood clot catcher 15B, but in the "reverse" flow direction, the blood can flow past the filter screen 28.

[0065] The Figuren 3A und 3Bshow a simplified schematic representation of a section through a second embodiment of the blood clot catcher, which differs from the first embodiment in the design of the housing body 21 and the sieve body 26. The corresponding parts are provided with the same reference numerals. In the second embodiment, the preferably rotationally symmetrical housing body 21 of the blood clot catcher has an elongated shape, with the housing body being conical on the side facing the first connection 22 and egg-shaped on the side facing the second connection 23. The sieve 28 of the sieve body 26 is designed in the shape of a thimble in the second embodiment, so that the sieve surface is enlarged.

[0066] The design of the housing body 21 and the sieve body 26 of the blood clot catcher 15A, 15B is not limited to the shapes described above. The housing body and sieve body can also have any other shape, as long as a flow path is created in the opposite flow direction, bypassing the sieve body.

Claims

1. Apparatus for extracorporeal blood treatment, comprising a blood treatment unit (1) that comprises at least one compartment (3), a first blood line (5) that is connected to a connection of the compartment (3) and comprises a first patient connection (8), a second blood line (7) that is connected to a connection of the compartment (3) and comprises a second patient connection (9), a blood pump for conveying blood, a device (14A, 14B) for measuring a physical or chemical characteristic variable, a control and evaluation unit (12) that is connected to the blood pump (10) and to the device (14A, 14B) for measuring a physical or chemical characteristic variable, and is designed such that the blood pump (10) can be operated in a first operating mode having a normal blood flow, such that blood flows from the first patient connection (8) to the blood treatment unit (1) and from the blood treatment unit to the second patient connection (9), the blood pump (10) can be operated in a second operating mode having a reversed blood flow, such that blood flows from the second patient connection (9) to the blood treatment unit (1) and from the blood treatment unit to the first patient connection (8), and the haemodynamic parameter is determined from the measured physical or chemical characteristic variable during normal and reversed blood flow, characterised in that an apparatus (15A) for collecting blood clots is provided at least in the first blood line (5), the apparatus (15A) for collecting blood clots comprising a housing body (21) having a first connection (22) and a second connection (23), and a screen body (26) for catching the blood clots that is arranged between the two connections in the flow path of the blood, the apparatus for collecting blood clots being designed such that a flow path bypassing the screen body (26) forms in the housing body (21) when blood flows in at the second connection and out at the first connection, and a flow path bypassing the screen body does not form when blood flows in at the first connection and out at the second connection.

2. Apparatus for extracorporeal blood treatment according to claim 1, characterised in that the screen body (26) is designed as a valve body and a valve seat (30) for the screen body is formed in the housing body (21), the screen body (26) being movably arranged in the housing body (21) such that the screen body rests on the valve seat when blood flows in at the first connection (22) and out at the second connection (23), and is lifted off the valve seat when blood flows in at the second connection (23) and out at the first connection (22), such that a flow path bypassing the screen body forms in the housing body.

3. Apparatus for extracorporeal blood treatment according to claim 2, characterised in that the screen body (26) is movably arranged between the first and second connection (22, 23) in the flow path of the blood, the movement of the screen body (26) in the housing body (21) being restricted to a range between a first and a second end position, the screen body (26) being fixed to the housing body (21) between the first and second connection (22, 23) in the flow path of the blood by means of elongate, flexible fixing elements (29), one end of each of which elements being connected to the screen body and the other end of each of which elements being connected to the housing body, the fixing elements (29) being arranged around the periphery of said screen body.

4. Apparatus for extracorporeal blood treatment according to any of claims 1 to 3, characterised in that the portion of the first blood line (5) connected to the first patient connection (8) is connected to the second connection (23) of the housing body (21) of the apparatus (15A) for collecting blood clots, and the portion of the first blood line (5) connected to the connection of the blood treatment unit (1) is connected to the first connection (22) of the housing body (21) of the first apparatus (15A) for collecting blood clots.

5. Apparatus for extracorporeal blood treatment according to any of claims 1 to 4, characterised in that an apparatus (15B) for collecting blood clots is provided in the second blood line (5), the portion of the second blood line (7) connected to the blood treatment unit (1) being connected to the first connection (22) of the housing body (21) of the second apparatus (15B) for collecting blood clots, and the portion of the second blood line (7) connected to the second patient connection (9) being connected to the second connection (23) of the housing body (21) of the second apparatus (15B) for collecting blood clots.

6. Apparatus for extracorporeal blood treatment according to any of claims 1 to 5, characterised in that a first pressure sensor (13A) for measuring the pressure in the first blood line (5) is connected to the control and evaluation unit (12) such that the control and evaluation unit (12) receives the measured values from the first pressure sensor (13A), and the control and evaluation unit (12) is designed such that the pressure measured by the first pressure sensor (13A) in the second operating mode is compared with a predetermined threshold value, a signal being generated when the pressure measured by the first pressure sensor exceeds the predetermined threshold value.

7. Apparatus for extracorporeal blood treatment according to any of claims 1 to 5, characterised in that a first pressure sensor (13A) for measuring the pressure in the first blood line (5) and a second pressure sensor (13B) for measuring the pressure in the second blood line (7) are connected to the control and evaluation unit (12) such that the control and evaluation unit (12) receives the measured values from the first and second pressure sensor (13A, 13B), and the control and evaluation unit (12) is designed such that the pressure measured by the first pressure sensor (13A) in the second operating mode is compared with the pressure measured by the second pressure sensor (13B) in the first operating mode, a signal being generated when the pressure measured by the first pressure sensor (13A) exceeds the pressure measured by the second pressure sensor (13B) by a predetermined amount or factor.

8. Apparatus for extracorporeal blood treatment according to either claim 6 or claim 7, characterised in that the control and evaluation unit (12) is designed such that the blood pump (10) is switched from the reversed blood flow to the normal blood flow when the signal is generated.

9. Apparatus for collecting blood clots in a blood line for supplying or removing blood in a blood treatment unit of an extracorporeal blood treatment apparatus, characterised in that the apparatus (15A, 15B) comprises a housing body (21) having a first connection (22) and a second connection (23), and a screen body (26) for catching the blood clots that is arranged between the two connections in the flow path of the blood, the apparatus (15A, 15B) for collecting blood clots being designed such that a flow path bypassing the screen body (26) forms in the housing body (21) when blood flows in at the second connection (23) and out at the first connection (22), and a flow path bypassing the screen body (26) does not form when blood flows in at the first connection (22) and out at the second connection (23).

10. Apparatus according to claim 9, characterised in that the screen body (26) is designed as a valve body and a valve seat (30) for the screen body is formed in the housing body (21), the screen body (26) being movably arranged in the housing body (21) such that the screen body (26) rests on the valve seat (30) when blood flows in at the first connection (22) and out at the second connection (23), and is lifted off the valve seat (30) when blood flows in at the second connection (23) and out at the first connection (22), such that a flow path bypassing the screen body forms in the housing body.

11. Apparatus according to claim 10, characterised in that the screen body is movably arranged between the first and second connection (22, 23) in the flow path of the blood, the movement of the screen body (26) in the housing body (21) being restricted to a range between a first and a second end position.

12. Apparatus according to claim 11, characterised in that the screen body is fixed to the housing body (21) between the first and second connection (22, 23) in the flow path of the blood by means of elongate, flexible fixing elements (29), one end of each of which elements is connected to the screen body (26) and the other end of each of which elements is connected to the housing body (21), the fixing elements (29) being arranged around the periphery of said screen body.

13. Apparatus according to claim 12, characterised in that the housing body (21) has a circular cross section and the screen body (26) comprises a retaining part (27) having a circular cross section, in which part a screen (28) is inserted.

14. Apparatus for extracorporeal blood treatment according to claim 8, characterised in that the retaining part is designed having the screen (28) as a planar body or in the shape of a thimble.

15. Apparatus according to any of claims 1 to 8, characterised in that the haemodynamic parameter is the shunt flow.