Device for extracorporeal blood treatment for determining an end point of a priming process

Abstract

The present invention relates to a device for extracorporeal blood treatment, comprising a control unit configured to carry out a method for determining an end point of a priming process, wherein the method comprises at least two phases, wherein in the first phase pressure-independent aspiration of blood is carried out, and upon reaching a switching point, a switchover to a second phase is performed, wherein in the second phase pressure-controlled aspiration of blood is carried out.

Description

[0001] January 7, 2026

[0002] 03503-25 He

[0003] Device for extracorporeal blood treatment to determine an endpoint of a priming process

[0004] The present invention relates to a device for extracorporeal blood treatment for determining an endpoint of a priming process.

[0005] Before a patient undergoes dialysis, the extracorporeal circuit (tubes and dialyzer) must be filled and flushed with a priming fluid before the patient's blood comes into contact with these components. After the patient is connected arterially and venously in preparation for dialysis, priming fluid is usually still present in the blood tubing.

[0006] To remove these, the patient's blood is drawn in (either serially or simultaneously through the venous and arterial branches) and the priming fluid is removed via the dialyzer, after which the system switches to treatment mode.

[0007] It is important to determine the correct endpoint of the priming process, particularly the blood aspiration to displace the priming fluid. Specifically, the point in time at which the blood passes through the dialyzer should be determined, or a point shortly before, if a residual volume of priming fluid is to be transferred to the patient.

[0008] Conventional methods for determining the endpoint of the priming process usually require continuous pressure measurements or are purely volumetric. However, this necessitates considerable effort for continuous pressure measurement, or the exact dimensions of the extracorporeal circuit and thus its intake volume must be known, which limits the flexibility in the use of tubing sets, etc.

[0009] Against this background, the present invention is based on the objective of mitigating or even completely eliminating the disadvantages of the prior art.

[0010] In particular, the present invention is based on the objective of creating a simplified method for accurately determining the endpoint of a priming process.

[0011] This problem is solved by the subject matter of claim 1. Preferred embodiments of the present invention are the subject matter of the dependent claims.

[0012] According to a first aspect, the present invention relates to a device for extracorporeal blood treatment, preferably a dialysis machine, with a control unit designed to perform a method for determining an endpoint of a priming process, wherein the method comprises at least two, preferably separate, phases, wherein in a first phase pressure-independent blood aspiration is performed and, upon reaching a switching point, preferably automatically, a switchover to a second phase is performed, wherein in the second phase pressure-controlled blood aspiration is performed. The blood aspiration in the second phase can be based on a blood-side and / or a hydraulic-side or dialysate-side pressure measurement.

[0013] Such a control system has the advantage that the process is more robust against measurement artifacts due to initial pressure fluctuations, because pressure measurements are not required, especially in the initial phase / first phase.

[0014] Furthermore, the volume of the extracorporeal circuit, particularly the tubing and dialyzer chambers, does not need to be known to accurately perform the procedure. In the first phase, volume-controlled blood aspiration can be performed, in which, for example, a predetermined volume of priming fluid is removed from the extracorporeal circuit of a dialysis machine.

[0015] Alternatively or additionally, by means of a control unit, priming fluid can be removed from the extracorporeal circuit of the dialysis machine until the presence of blood in a certain section of the extracorporeal circuit is detected by means of at least one preferably optical sensor, whereupon the switching point is reached and / or the switchover to the second phase takes place.

[0016] Instead of an optical sensor, another sensor, such as an ultrasonic sensor or conductivity sensor, can also be used.

[0017] For example, at least one first sensor can be arranged to detect the presence of blood in a venous branch and a second sensor can be arranged to detect the presence of blood in an arterial branch of the extracorporeal circulation, with either the detection of the presence of blood by the first sensor and / or the second sensor indicating that the switching point has been reached.

[0018] In this example, in addition to an optical sensor, another type of sensor, such as an ultrasonic sensor or a conductivity sensor, can also be used. Two identical or two different sensors can be used.

[0019] In the first phase, the control unit allows blood to be drawn only to the extent that a predetermined buffer volume or residual volume of priming fluid remains in the extracorporeal circuit. Similarly, in the second phase, the control unit allows blood to be drawn only to the extent that a predetermined buffer volume or residual volume of priming fluid remains in the extracorporeal circuit. This buffer volume or residual volume of priming fluid can then be administered to the patient at the start of treatment.

[0020] Conventional devices for extracorporeal blood treatment usually employ methods to determine the endpoint of a priming process, which rely on continuous pressure measurement.

[0021] In a device according to the invention, only intermittent pressure measurement, and not continuous pressure measurement, can be performed in the second phase. This reduces the effort required for data acquisition.

[0022] In principle, the control unit can be designed to initiate the aspiration of blood through the arterial and / or venous branches of the extracorporeal circuit, preferably to the same extent. The aspiration of blood through the arterial and / or venous branches can occur simultaneously or sequentially.

[0023] The control unit can be designed to monitor a pressure difference between the arterial branch and the venous branch during the aspiration of blood through the arterial branch and the venous branch, in order to detect deviations in the flow rates in the arterial branch and the venous branch.

[0024] For example, the measured pressure difference between the arterial branch and the venous branch can be compared with a limit value or tolerance range, and in case of a deviation, regulation can take place so that the aspiration of blood by the arterial branch and the venous branch of the extracorporeal circulation occurs to as equal an extent as possible.

[0025] The following are descriptions of variations in the design of the second phase:

[0026] Furthermore, the control unit can be designed to detect an absolute suction pressure in the venous line downstream of the dialyzer in the second phase and compare it with a limit value, whereby if the absolute suction pressure exceeds the limit value, the aspiration of blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

[0027] Alternatively or additionally, the control unit can be designed to detect a change, preferably a decrease, in the suction pressure in the venous line downstream of the dialyzer in the second phase and to compare it with a limit value, wherein, if the decrease in suction pressure exceeds the limit value, the aspiration of blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

[0028] If a change in suction pressure, preferably a decrease, is detected, this offers the advantage of greater independence from environmental parameters such as ambient pressure, temperature, the dialyzer used, hoses, etc.

[0029] In other words, the first aspect of the present invention can be described as follows:

[0030] According to the first aspect of the present invention, during the removal or withdrawal of priming fluid from the extracorporeal circuit by the dialyzer by means of a displacement suction of blood, at least two control methods (also referred to as two “phases”, another conceivable term would be two “steps”) are applied or carried out successively, wherein the second phase comprises a pressure-based control method.

[0031] A two-stage procedure according to the invention offers the following advantages:

[0032] Pressure signal fluctuations in the first phase of withdrawal (i.e., while it is ensured that no blood is present in the dialyzer) do not lead to an unintentional termination of withdrawal.

[0033] The dialysis machine, after the patient is connected, is thus given a stabilization phase after the priming fluid is withdrawn by the dialyzer and blood is drawn in. During this phase, the blood pump and suction pump are running, and blood with a different viscosity and temperature than the priming fluid is being drawn in. In this state, pressure fluctuations do not yet affect the termination of the withdrawal process. Therefore, pressure fluctuations in the initial phase do not lead to a premature termination of blood aspiration.

[0034] Furthermore, the volume of the dialyzer does not need to be known for correct operation. This increases flexibility, as a dialysis device according to the invention is compatible with various dialyzers and tubing sets.

[0035] The removal of the priming fluid by the dialyzer can be achieved using a suction pump, for example, in the form of appropriately configured balance chambers and / or an ultrafiltration pump. On the venous side, this is done, for example, directly by drawing blood with the suction pump; on the arterial side, a blood pump is operated, which draws blood from the artery and pumps it towards the dialyzer.

[0036] The ratio of the flow rates of the suction pump and the blood pump determines how quickly arterial and venous aspiration occurs relative to each other.

[0037] The blood pump can be designed as a roller pump with retractable rollers that are retracted to draw in the blood. If the blood pump is a diaphragm pump, the valves at the inlet and outlet can be set to open for blood intake.

[0038] The control of the second phase, which is used to end the suction process, is pressure-based.

[0039] In this process, the absolute suction pressure in the line downstream of the dialyzer can be incorporated into the control system and compared with a limit value.

[0040] Alternatively or additionally, a drop in suction pressure in the line downstream of the dialyzer can be compared to a limit value, which offers the advantage of greater independence from environmental conditions such as ambient pressure, temperature, dialyzer used, etc.

[0041] The control system for the second phase is preceded by a control system for the first phase, which is used to detect when the switchover to the second phase occurs. This identifies a switching point between the first and second phases.

[0042] The control of the first phase may include at least one of the following steps:

[0043] A predetermined volume of priming fluid can first be withdrawn via the dialyzer. This predetermined volume can be based on a predefined value, e.g., 20 mL, which can be stored in a database for each case or entered manually. Alternatively, a value stored for the selected blood tubing set can be used (e.g., 20 mL for tubing set A and 50 mL for tubing set B), or a value based on a measurement obtained when filling the tubing set with priming fluid (e.g.,

[0044] 20% of the filling volume of priming fluid).

[0045] A sensor system or at least one sensor (e.g., a blood detector using optical density, color, or viscosity detector using ultrasound) may be present, which detects when the blood front has passed a specific point in the tubing set.

[0046] The sensor system can be provided on only one branch, preferably the venous one, or on both branches, whereby either the first detection or the second detection can be used as the switching point for the control change from the first phase to the second phase.

[0047] Within the framework of a dialysis device according to the invention, a more than two-phase, i.e., a multi-phase, control system can also be provided. For example, the control unit can be programmed such that first the blood-side sensors are used, then in the next phase a predetermined volume of priming fluid is withdrawn, and then in the next phase the system can switch to pressure-based control.

[0048] This has the advantage that the volume that can be set as a predetermined volume can be chosen to be absolutely smaller, and a volume that is slightly too large or too small (e.g. 10% over or under) is less significant than if a percentage error is made with a large volume.

[0049] To stop the withdrawal process, the control unit of a dialysis device according to the invention can take various measures:

[0050] The suction pump can be stopped by the control unit and / or the blood pump can be stopped by the control unit and optionally the arterial and / or venous clamp can be closed.

[0051] If a balance chamber system is used as the suction pump, it can be switched from a suction functionality to a balancing functionality by the control unit.

[0052] The blood pump rate can be increased by the control unit (specifically to a prescribed value for a treatment), and optionally, the suction pump rate can be reduced by the control unit to a prescribed value for the treatment. Thus, the ultrafiltration rate initially prescribed for the treatment can be set by the control unit.

[0053] Alternatively or additionally, a dialysate flow can be started by the control unit; preferably, a dialysate flow initially intended for treatment is set by the control unit.

[0054] According to a second aspect, the present invention relates to a dialysis machine with a control unit, wherein the control unit is designed to perform a method for determining an endpoint of a priming process, in which at least one pressure information from a line upstream and / or downstream of the dialyzer is used to detect the presence of blood in the dialyzer or immediately upstream of the dialyzer.

[0055] The control unit can be designed to perform an evaluation of pressure amplitudes on the blood side upstream and / or downstream of the dialyzer. This takes advantage of the fact that the pressure profile measured upstream and downstream of the dialyzer changes when switching from priming fluid to blood. In particular, the amplitudes of the measured pressure pulses change.

[0056] By monitoring the pressure profile on the blood side upstream and / or downstream of the dialyzer, it is possible to detect when the blood displaces the priming fluid in the dialyzer.

[0057] Preferably, if the evaluation by the control unit indicates an increase in the size of the pressure amplitudes upstream of the dialyzer, preferably relative to the pressure amplitudes downstream of the dialyzer, the aspiration of the blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

[0058] The evaluation can include determining a relative size difference of the pressure amplitudes on the blood side upstream and downstream of the dialyzer, preferably expressed in percent or an absolute value.

[0059] For example, the pressure amplitudes on the upstream side may be 10% or 2 mmHg greater than the pressure amplitudes on the downstream side of the dialyzer.

[0060] The relative and / or absolute size difference of the pressure amplitudes can be compared by the control unit with a limit value, and if the limit value is exceeded, the blood aspiration can be stopped and the dialysis machine preferably automatically switched to a treatment mode, since in this case the presence of blood in the dialyzer has been detected.

[0061] Alternatively or additionally, the control unit can be designed to perform an evaluation of the power consumption of the blood pump and / or the transmembrane pressure of the dialyzer membrane, whereby, if the power consumption of the blood pump and / or the measured transmembrane pressure exceeds a limit value, the blood aspiration is initially stopped and the dialysis machine preferably switches automatically to a treatment mode, since in this case the presence of blood in the dialyzer has been detected.

[0062] The control unit can be designed to perform such control that at a time when the dialysis machine preferably switches automatically to a treatment mode, a residual volume of priming fluid remains in the extracorporeal circuit, which is supplied to the patient.

[0063] In other words, the second aspect of the present description can be described as follows:

[0064] After connecting the patient both arterially and venously, the priming fluid is drawn off through the membrane of the dialyzer in both the arterial and venous branches and displaced by the patient's blood.

[0065] The endpoint of this process for removing the priming fluid, and thus the endpoint of the priming process, is detected, among other things, by an evaluation of measured values ​​that also use at least some information about the pressure change on the blood side.

[0066] The term "endpoint" is preferably to be understood as meaning that this pressure-based method of monitoring or filling the tubing system ends; in fact, priming fluid can subsequently continue to be drawn off via the dialyzer membrane, for example, in a volumetrically controlled manner. The driving force for filling the venous and arterial branches is, for example, a negative transmembrane pressure generated by a hydraulic emptying program or, alternatively, by means of the ultrafiltration pump of a dialysis device according to the invention. The flushing volume located in the blood tubing system is removed via the dialyzer membrane.

[0067] A negative transmembrane pressure (TMP) means that the pressure difference between the blood side and the water / dialysate side is less than zero.

[0068] The ratio of flow rates between the arterial and venous branches is preferably regulated by the blood pump. For example, the blood pump reduces the arterial inflow of patient blood during simultaneous tubing system filling through the arterial and venous branches under negative TMP.

[0069] For example, if a negative TMP results in a flow rate of 120 ml / min, the blood pump regulates what portion of that 120 ml / min is delivered arterially. The remainder is delivered venously.

[0070] Suction via the blood pump only occurs with the arterial branch, e.g., during serial filling. In this process, the blood pump pushes the patient's blood into the dialyzer, while the priming fluid is pushed through the dialyzer membrane.

[0071] The flow rates of the blood pump and any other components are preferably selected accordingly, so that the blood filling from the arterial branch and the venous branch occurs to as equal an extent as possible, so that the two blood fronts meet in the dialyzer and the blood-side side is filled homogeneously (with simultaneous filling).

[0072] As the dialyzer gradually fills with blood, the oncotic pressure increases on both the blood and hydraulic sides of the membrane. Similarly, with increasing hemoconcentration, the permeability of the dialyzer membrane to the pressure pulses generated by the blood pump decreases. In this way, the pressure profile changes when the priming fluid in the extracorporeal circuit is displaced by blood, a phenomenon utilized according to the invention.

[0073] The term "pressure pulse" can be understood as follows: A pressure pulse can be the summed superposition of periodic fluctuations of different amplitudes (displacements) in a pressure curve diagram over time. For example, with higher periodic fluctuations, i.e., oscillations of higher frequency, the amplitude decreases. Therefore, the maximum pulse height or amplitude can be considered representative of the amplitude of the oscillation.

[0074] As the hemoconcentration in the dialyzer increases, for example the intensity of the pressure pulses along the dialyzer (measured by a venous sensor of the device) and across the membrane (measured by a hydraulic sensor of the device) decreases.

[0075] Therefore, by analyzing the pressure pulses downstream of the dialyzer and / or via the sensors in the hydraulics of the device, the arterial and venous filling of the dialyzer with blood can be monitored.

[0076] If a pressure sensor is implemented upstream of the dialyzer in the arterial tubing system, it can also be used optionally. This ("post-pump") pressure sensor detects an increase in amplitude during the filling of the dialyzer with blood.

[0077] In other words, the amplitude of the pressure pulses before and after the dialyzer can be measured if the dialysis machine is equipped with appropriate sensors. As the dialyzer fills with blood, the amplitude of the measured pressure pulses increases upstream of the dialyzer because the pressure "rebounds" due to the reduced membrane permeability, thus increasing the amplitude at that point. Simultaneously, the amplitude of the pressure pulses after the dialyzer—primarily on the dialysate / hydraulics side—decreases because less pressure passes through the membrane, resulting in a smaller amplitude.

[0078] This can be measured by the arterial pressure sensor (if present) and / or by one of the hydraulic pressure sensors of a dialysis machine.

[0079] Even downstream of the dialyzer (in the venous branch), the venous pressure sensor can receive an evaluation signal; however, the signal detected in the venous sensor may be less meaningful due to the mixing of the hemoconcentration of the arterially pumped blood with that of the venously pumped blood.

[0080] As a further indicator, or alternatively to analyzing pressure pulses, the electrical power consumption of the blood pump (i.e., the motor power) can increase if the flow resistance along the fibers increases due to the increasing hemoconcentration in the dialyzer, thus reducing membrane permeability. Therefore, the power consumption of the blood pump can also be monitored to detect the displacement of the priming fluid in the dialyzer by blood.

[0081] This is especially true when filling is done serially and the blood pump is the driving force for the priming volume delivered across the dialyzer membrane. With simultaneous arterial and venous filling, the negative TMP (pressure drop on the blood side compared to the water side) provides the driving force, and the blood pump merely reduces the flow rate of the arterial branch.

[0082] In a dialysis device according to the invention, the control unit can monitor the transmembrane pressure or the change in transmembrane pressure, which increases due to the oncotic pressure on the blood side as the dialyzer is filled with blood. This evaluation is preferably performed using four pressure sensors of the dialysis device, or only three pressure sensors if the arterial pressure sensor is not present. If not the entire priming volume is to be discarded, but rather some is to be administered to the patient, the venous blood is only drawn up to the drip chamber, at which point the volume discard via the dialyzer stops and the withdrawal process is terminated. The remaining priming solution is then administered venously to the patient via the blood pump.

[0083] In this example, the drip chamber is an example of a chamber separate from the dialyzer.

[0084] The aspiration test according to the third aspect of the invention can additionally be performed arterially and / or venously.

[0085] Instead of the suction pressure, which on the hydraulic side represents the filling of the blood-side dialyzer, according to the second aspect of the invention, the process of aspirating blood to displace the priming fluid from the dialyzer can be separated into the following two parts with separate representations on the blood side:

[0086] First, a quasi-static phase can occur, in which the control unit activates the blood pump to deliver blood to the dialyzer via the arterial line:

[0087] In this process, the pressure upstream of the (blood-side) dialyzer increases as the membrane permeability decreases. This can be detected by a pre-filter pressure sensor in the dialysis machine (which is not always present), or additionally or alternatively, the control unit can measure the motor current or the power consumption of the blood pump. Alternatively, the venous pressure (via the venous pressure sensor) can be measured, which will increase when the blood-side of the dialyzer is filled with blood and the venous line is closed. However, this requires a quasi-serial (venous-arterial) filling process. Alternatively or additionally, in the quasi-static section, a negative transmembrane pressure can drive blood into the dialyzer via the venous line: The hydraulic-side pressure (also called transmembrane pressure, depending on the sensor used) decreases as the membrane permeability decreases.The pressure on the blood side remains largely unchanged, while the hydraulic pressure decreases with increasing hemoconcentration in the dialyzer. Venous pressure (detected by the venous pressure sensor) is suitable for monitoring this filling process; however, its accuracy is affected at the beginning of retrograde filling via the venous line by the needle size and the viscosity of the blood. In this case, too, the filling process is quasi-serial, since the arterial branch must preferably be closed during filling via the venous branch to avoid artifacts.

[0088] Another way to detect the progressive filling of the extracorporeal circuit with blood is an optical detector in the venous drip chamber, the color change of which provides a reliable indication of the retrograde filling process.

[0089] A dynamic phase can then take place. In this section of the filling process, for example, pressure pulses generated by the rotating blood pump travel downstream and upstream along the blood tubing system, resulting in "pressure dynamics".

[0090] The amplitude of the pressure pulses can be recorded at the corresponding sensors (e.g. sensors for measuring arterial pressure, venous pressure, post-pump pressure).

[0091] Several methods for filling the extracorporeal circuit with blood through appropriate control of the control unit are conceivable. Each of these exhibits a characteristic pressure profile, which can be detected by sensors on the dialysis machine:

[0092] For example, simultaneous filling via the venous and arterial branches can be achieved with negative hydraulic pressure or TMP as the driving force. If the hemoconcentration in the dialyzer increases, the amplitude of the pressure pulses at the post-pump sensor also increases, the amplitude of the pressure pulses at the venous sensor decreases, the amplitude of the pressure pulses at the arterial sensor remains unchanged, and the amplitude of the pressure pulses at the hydraulic-side pressure sensor decreases.

[0093] Filling can also be performed via the arterial branch (venous clamp closed) using negative hydraulic pressure or TMP as the driving force.

[0094] When the hemoconcentration in the dialyzer increases, the amplitude of the pressure pulses at the post-pump sensor also increases, the amplitude of the pressure pulses at the venous sensor decreases, the amplitude of the pressure pulses at the arterial sensor remains unchanged, and the amplitude of the pressure pulses at the hydraulic-side pressure sensor decreases.

[0095] Filling can also be achieved via the arterial branch (venous clamp closed) using the blood pump as the driving force.

[0096] When the hemoconcentration in the dialyzer increases, the amplitude of the pressure pulses at the post-pump sensor also increases, the amplitude of the pressure pulses at the venous sensor decreases, the amplitude of the pressure pulses at the arterial sensor remains unchanged, and the amplitude of the pressure pulses at the hydraulic-side pressure sensor decreases, and the electrical power consumption of the blood pump increases.

[0097] Filling can also be performed via the venous branch (artificial clamp closed) using negative hydraulic pressure or TMP as the driving force.

[0098] In this case, the blood pump is not operating, therefore no pressure pulses are generated by the blood pump. In this case, the ultrafiltration pump (UF pump) is considered: As the hemoconcentration in the dialyzer increases, the amplitude of the UF pump pressure pulses decreases at the post-pump sensor, the amplitude of the UF pump pressure pulses decreases at the venous sensor, and the amplitude of the UF pump pressure pulses increases at the hydraulic-side pressure sensor. The monitoring parameters of the quasi-static and dynamic components can also be combined by the control unit; for example, an amplitude can be divided by a quasi-static value.

[0099] Alternatively or additionally, several pressure measurements can be combined, e.g. the amplitude of the pressure pulses at the venous sensor divided by the amplitude of the pressure pulses at the post-pump sensor.

[0100] According to a third aspect, the present invention relates to a dialysis machine with a control unit, wherein the control unit is designed to automatically perform an aspiration test to verify a correct execution of an arterial and / or venous needle connection, preferably before a method for removing priming fluid from the extracorporeal circulation by aspirating blood is performed.

[0101] In the aspiration test, a predetermined volume of blood can be drawn into a chamber separate from the dialyzer, for example a drip chamber, whereby a pressure and / or a pressure change, in particular a pressure drop, in an arterial and / or venous line carrying the aspirated blood is monitored by means of at least one sensor and at least one pressure reading of the sensor is compared with a limit value and / or a target range.

[0102] The control unit may be designed to automatically initiate a process for displacing priming fluid from the extracorporeal circuit when correct execution of the arterial and / or venous needle connection has been detected based on the measured pressure and / or pressure drop.

[0103] For example, the control unit can initiate a process for drawing in blood according to one of the preceding aspects of the present invention.

[0104] In other words, the third aspect of the present description can be described as follows: Traditionally, when inserting the needles to connect the patient to the arterial and venous lines, nursing staff or the patient checks whether the needles have been inserted correctly. This test is called an aspiration test. It involves checking whether blood can be drawn, for example, using a syringe attached to the tubing end of the needle unit. The nursing staff should be relieved of this task.

[0105] According to the third aspect of the invention, an aspiration test can thus be performed automatically by the dialysis machine or its control unit.

[0106] The following procedure can be performed by the control unit to detect a correctly placed arterial needle connection: The blood pump is started (the suction pump is preferably stationary) at a low speed for a small volume, so that blood is aspirated when a correct connection is established. This is monitored by the arterial pressure sensor of the dialysis machine.

[0107] If the needle is inserted into the tissue and not correctly into the vessel, a sharp drop in the pressure signal is observed. If the needle is correctly inserted into the vessel, a moderate pressure drop is observed. If the needle is not connected at all, air is drawn in, and practically no or only a very slight pressure drop is observed. The control unit analyzes the pressure sensor readings and thus differentiates between these scenarios.

[0108] The fluid volume transported by the blood pump is preferably transferred into the venous (drip) chamber, i.e., not drawn off via the dialyzer membrane, meaning that this step is not part of the removal of the priming fluid.

[0109] Alternatively or additionally, the correctly placed venous needle connection can be detected: The suction pump is started at a low speed for a small volume, drawing blood if a correct venous connection exists. This is monitored using the venous pressure sensor.

[0110] If the needle is in the tissue and not in the vessel, a sharp drop in the pressure signal is observed. If the needle is correctly inserted in the vessel, a moderate pressure drop is observed. If the needle is not connected at all, air is drawn in, and practically no or only a very slight pressure drop is observed. The control unit analyzes the pressure sensor readings and thus performs a case differentiation.

[0111] In this case, the volume of fluid displaced by the blood is drawn off via the dialyzer membrane, which is why this step can be considered part of the removal of the priming fluid.

[0112] Following the successful automatic aspiration test (arterial and / or venous connection correct), a dialysis device according to the invention preferably automatically begins a method for replacing the priming fluid with blood in the extracorporeal circuit according to the first and / or second aspect of the present invention.

[0113] The pressure change observed during an aspiration test depends, for example, on the compliance of the tubing system between the needle tip and the blood pump. Compliance can vary depending on factors such as the length of the tubing, its diameter, and the tubing material. This compliance value can be stored in a database, which the control unit then accesses.

[0114] It can therefore be implemented that the limit values, against which, for example, the pressure drop is compared, are set depending on the hose assembly. This can be done, for example, by entering the hose assembly and having either the compliance or the limit values ​​defined for it. If the compliance is defined, the corresponding limit values ​​can be defined, for example, using a stored table or a system of equations. Alternatively, the compliance or a parameter correlated with the compliance can be determined in advance by the control unit during priming, particularly during the filling process.

[0115] To determine compliance, a relevant volume can be enclosed, and then the pressure in this area is increased or decreased, and compliance is determined from the pressure change (e.g., closing the arterial clamp and pumping fluid into or out of the volume with the blood pump, or connecting the arterial tubing end to the venous tubing end and closing the venous clamp, pumping fluid into or out of the volume with the blood pump, and measuring the pressure change with the arterial pressure sensor).

[0116] In order to have sufficient free volume in the drip chamber for the aspiration test, the fill level in the venous chamber can be lowered by the control unit in a preliminary filling step of the extracorporeal blood tubing set.

[0117] The above explanations individual aspects of the present invention. It is understood that the respective aspects, or even individual features thereof, can be combined with one another or claimed in isolation. In principle, the features of the first, second, or third aspect can each be claimed separately.

[0118] The present invention further comprises a method for determining an endpoint of a priming process using a dialysis machine as described above, wherein the method is preferably carried out before the start of treatment and / or during an interruption of the patient's treatment. The method, and in particular the control of the sensors and / or pumps, is preferably carried out within the framework of the method according to the invention as already described above with regard to the dialysis machines according to the invention.

[0119] One aspect of the invention thus relates to a method for determining an endpoint of a priming process of a device for extracorporeal blood treatment, wherein the method comprises at least two, preferably separate and / or serially successive, phases, wherein in the first phase a pressure-independent aspiration of blood is carried out and upon reaching a switching point, a switch is made to a second phase in which a pressure-controlled aspiration of blood is carried out.

[0120] The aspiration of blood in the second phase can be performed based on a blood-side pressure measurement.

[0121] Alternatively or additionally, the aspiration of blood in the second phase can be carried out based on a hydraulic pressure measurement.

[0122] A method according to the invention is preferably carried out by means of a control unit described above in the context of a device according to the invention.

[0123] It should be noted here that the terms "ein" and "eine" do not necessarily refer to exactly one of the elements, although this is a possible interpretation, but can also denote a plurality of elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely, the singular also includes several of the elements in question.

[0124] Furthermore, all features of the invention described herein can be combined with one another or claimed separately; the disclosure is therefore not limited to explicitly named combinations of features. Further details and advantages of the invention are explained in more detail with reference to the exemplary embodiments shown in the drawing.

[0125] This shows:

[0126] Fig. 1 shows an exemplary control of the first phase, which can be implemented by a control unit of a dialysis machine according to the first aspect of the present invention.

[0127] Fig. 2 shows an exemplary control of the second phase, which can be implemented by a control unit of a dialysis machine according to the first aspect of the present invention.

[0128] Fig. 3 illustrates an example of the construction of a dialysis device according to the invention, and

[0129] Fig. 4 illustrates an analysis of the pressure pulse amplitudes which can be performed by a control unit of a dialysis machine according to the second aspect of the present invention.

[0130] Fig. 1 shows an exemplary control of the first phase, which can be implemented by a control unit of a dialysis machine according to the first aspect of the present invention.

[0131] In this first phase, the control unit performs a volume-controlled aspiration of blood into the extracorporeal circulation.

[0132] The filling volume of priming fluid (consisting of blood tubing volume + dialyzer) is either determined during preparation or read in by disposable identification (e.g.: by means of QR code recording of blood tubing system + dialyzer and determination of the stored volumes of the consumables used).

[0133] The filling volume of an extracorporeal circuit can be determined during the initial filling with priming fluid: With sensor 1, preferably a pressure sensor, in the arterial line and sensor 2, preferably a pressure sensor, which monitors the pressure in the venous line and / or the venous chamber, it is recorded after which pumping volume of the blood pump BP the conversion of air to the priming fluid (online fluid or NaCI solution) takes place.

[0134] From this, the volume of the filled section between the two sensors 1 and 2 can be calculated by the control unit.

[0135] In addition, a fixed offset or residual volume for the volume of the arterial and venous patient lines can preferably be taken into account (see Voffset = approx.

[0136] 2 x 20ml). The volume offset is very similar for different tubing sets, at least in adult blood tubing systems.

[0137] As shown in Fig. 1, a process is then carried out to aspirate blood in order to displace the priming fluid from the extracorporeal circulation. The duration of the aspiration process is volume-controlled.

[0138] The tubing set is initially filled with priming fluid and the level in the venous chamber K line is preferably as high or as air-free as possible.

[0139] After the patient has been connected via both arterial and venous lines, blood is preferably drawn simultaneously and in parallel, i.e., synchronously, from the venous and arterial lines to ensure even filling of the blood side of the dialyzer from both sides of the connected blood tubing system. This is illustrated by the arrows in Fig. 1.

[0140] The aspiration flow is set or controlled, for example, by the control unit via a balance chamber program, whereby preferably half of the set aspiration flow is delivered by the blood pump BP in the arterial line. The remaining aspiration flow (also 50%) is then delivered from the venous line. The distribution of the aspiration flow can be monitored by the control unit by tracking the pressure difference ΔPdiff = Pven - Part. This determines the difference between the pressure readings of the arterial and venous pressure sensors 1 and 2. The pressure difference should not exceed a certain limit, otherwise the aspiration from the lines will be uneven.

[0141] Uneven suction leads to uneven filling of the dialyzer D, and as a result, too much saline solution remains in the arterial or venous compartment.

[0142] The aspiration of blood during phase 1 shown in Fig. 1 is stopped as soon as the predetermined volume (preferably less a safety volume offset, e.g., Vs = 20 - 40 ml) of priming fluid has been successfully drawn off across the dialyzer membrane.

[0143] The offset ensures that excessively high hemoconcentration cannot accumulate in the dialyzer (thickening of the blood is avoided). The offset thus refers, for example, to a residual volume of priming fluid that is not removed.

[0144] After the endpoint of the first phase has been detected, the system switches, preferably automatically, to the second phase, since the endpoint of the first phase preferably forms the switching point to the second phase.

[0145] Fig. 2 shows an exemplary control of the second phase, which can be implemented by a control unit of a dialysis machine according to the first aspect of the present invention.

[0146] The control of the second phase involves pressure-controlled aspiration of blood to replace the priming fluid in the extracorporeal tubing set with blood. This takes into account pressure readings from arterial sensor 1, and / or venous sensor 2, and / or sensor 3 (also referred to as the "prefilter" sensor) located between the blood pump BP and the dialyzer D.

[0147] In the second phase, blood continues to be drawn simultaneously and in parallel from both the venous and arterial branches.

[0148] The hydraulic suction flow is then reduced (e.g., to 100 m³ / min), whereby the blood pump BP again draws 50% of the hydraulic suction flow from the arterial line. Thus, the remaining flow (50%) is also drawn from the venous branch.

[0149] The suction volume or suction duration (i.e., the volume of blood drawn or the duration of the suction process) is controlled by the control unit based on pressure monitoring of at least one of the sensors 1 to 3.

[0150] Figure 2 shows the corresponding pressure sensors 1 and 3 in the arterial line upstream and downstream of the blood pump, and the pressure sensor 2 in the venous line. Preferably, the control unit detects at least one of the following pressure differentials:

[0151] - 1. Pressure difference delta p1 = Pven — S07:

[0152] Monitoring of the suction flow in the venous line by calculating the pressure difference between the pressure in the venous line (P ven ) measured by sensor 2 and the suction pressure at the suction pump P measured by sensor S07.

[0153] - 2. Pressure difference delta p2 = P pre - S07:

[0154] Monitoring of the aspiration flow in the arterial line by calculating the pressure difference between the pressure in the arterial line downstream of the blood pump and upstream of the dialyzer, measured by sensor 3 (P pre This refers to a pressure measurement at the "prefilter pressure sensor") and the intake pressure at the intake pump P measured by sensor S07.- 2a. Pressure difference delta p2' = (Part - S07):

[0155] Alternatively or additionally, monitoring of the suction flow in the arterial line can also be carried out by calculating the pressure difference between the pressure (Part) in the arterial line upstream of the blood pump measured by sensor 1 and the suction pressure at the suction pump P measured by sensor S07.

[0156] The distribution of the intake flow between the venous and arterial branches can, in principle, be monitored by the control unit via the evaluation of the aforementioned pressure differences.

[0157] The pressure differential should not exceed a certain limit, otherwise uneven suction will occur from one of the lines. Uneven suction leads to uneven filling of the dialyzer.

[0158] The second phase of the intake process is terminated by the control unit, for example, if the pressure difference delta p1 = Pven - S07 exceeds a certain limit.

[0159] After filling the dialyzer, the blood flow in the extracorporeal circuit can be slowly increased and the treatment can be started by the user or automatically.

[0160] Unless this has already been explained within the context of the functions and options according to the invention, it is hereby pointed out once again that the control system of the dialysis machine according to the invention is designed and, in particular, programmed in such a way as to provide these functions and options and to implement their execution.

[0161] Fig. 3 illustrates an exemplary setup of a dialysis device according to the invention, which is explained with reference to a control method according to the first aspect of the invention. The removal of priming fluid through the dialyzer membrane in the dialysis device according to Fig. 3 can be carried out by means of a suction pump.

[0162] The suction pump can be in the form of appropriately connected balance chambers 15 or in the form of the ultrafiltration pump 24, with which, for example, the priming liquid is drawn off.

[0163] On the venous side, blood is preferably drawn in directly, while on the arterial side, for example, the blood pump BP is operated, which draws in the blood arterially and pumps it towards dialyzer D. The relative rates of the suction pump and the blood pump BP determine how quickly the arterial and venous blood are drawn in relative to each other.

[0164] A second-phase control method, used, for example, to stop blood suction, is pressure-based and / or pressure differential-based. At least one of the following parameters can be incorporated into the control:

[0165] - The absolute suction pressure 32 / S07 (the pressure measured at point 32 by sensor S07) in line 16A downstream of the dialyzer. This is compared with a limit value.

[0166] - A drop in suction pressure 32 / S07 is compared with a limit value.

[0167] A first-phase control method, used to detect when to switch to the second-phase control method, is volume-controlled. At least one of the following parameters can be incorporated into the control:

[0168] In the example shown in Fig. 3, a sensor located on the blood side (e.g., a blood detector using optical density or color, or a viscosity detector using ultrasound) detects when the blood front has passed a specific point in the tubing. In this example, the sensor (ABD in Fig. 3) is located in both the venous and arterial branches.

[0169] Several measures can be taken to stop the withdrawal process. The suction pump can be stopped by the control unit, and optionally the blood pump BP can also be stopped, and optionally the arterial and / or venous clamps 8 and 12 can be closed.

[0170] If the balance chamber system 15 is used as the suction pump, it can be switched from aspiration to balance functionality. The blood pump rate can be increased (in particular to a prescribed value for a treatment) and optionally the rate of pump 24 can be reduced to a prescribed value for the treatment, i.e., for example, the ultrafiltration rate initially intended for the treatment can be set.

[0171] Fig. 4 illustrates an analysis of the pressure pulse amplitudes which can be performed by a control unit of a dialysis machine according to the second aspect of the present invention.

[0172] The dialysis machine shown schematically in Fig. 4 has a total of four pressure sensors, two of which are located on the blood side in the arterial line (sensor 1) and venous line (sensor 2), and two of which are located on the hydraulic side in the inlet to the dialyzer (sensor 5) and in the outlet of the dialyzer (sensor 4).

[0173] The exchange of priming fluid by blood in the dialyzer can be detected using the measured values ​​of sensors 1, 2 and 4, 5 or even just one sensor or a subgroup thereof.

[0174] As the hemoconcentration in the dialyzer increases, the intensity of the pressure pulses along the dialyzer (detected by the venous sensor 2) and across the membrane (detected by at least one of the hydraulic sensors 4 and 5) decreases. Therefore, the arterial and venous filling of the dialyzer can be monitored by analyzing the pressure pulses downstream and / or upstream of the dialyzer and / or via sensors 4 and 5 in the hydraulic system.

[0175] If a pressure sensor 1 is implemented upstream of the dialyzer in the arterial tubing system, it can also be used optionally. This pressure sensor 1 (also referred to as a post-pump sensor) expects an increase in amplitude during the filling of the dialyzer with blood, as shown by way of example in Fig. 3.

[0176] In other words, the amplitude of the pressure pulses before and after the dialyzer can be measured if appropriate sensors are available.

[0177] As the dialyzer fills with blood, the amplitude increases upstream of the dialyzer. Simultaneously, the amplitude decreases downstream of the dialyzer—that is, preferably on the dialysate side—because less pressure passes through the membrane, thus reducing the amplitude. This is illustrated in Fig. 3 by the exemplary pressure curve shown below sensor 2.

[0178] The increase in amplitude size upstream of the dialyzer can be measured by the arterial pressure sensor 1 (if present) and / or by one of the hydraulic pressure sensors 4 and 5.

[0179] The venous pressure sensor 2 can also receive an evaluation signal downstream (in the venous branch).

Claims

January 7, 2026 03503-25 He Device for extracorporeal blood treatment to determine an endpoint of a priming process Claims 1. Device for extracorporeal blood treatment, comprising a control unit designed to perform a method for determining an endpoint of a priming process, wherein the method comprises at least two phases, wherein in the first phase a pressure-independent aspiration of blood is performed and upon reaching a switching point a switch is made to a second phase, wherein in the second phase a pressure-controlled aspiration of blood is performed.

2. Device according to claim 1, wherein the control unit is designed to perform the aspiration of blood in the second phase based on a blood-side pressure measurement.

3. Device according to claim 1 or 2, wherein the control unit is designed to perform the aspiration of blood in the second phase based on a hydraulic pressure measurement.

4. Device according to any one of the preceding claims, wherein in the first phase a volume-controlled aspiration of blood is performed, in which a predetermined volume of priming fluid is removed from an extracorporeal circuit of a dialysis machine and / or priming fluid is removed from an extracorporeal circuit of a dialysis machine until the presence of blood in a specific section of the extracorporeal circuit is detected by means of at least one preferably optical sensor, whereupon a switching point is reached.

5. Device according to one of the preceding claims, wherein at least a first sensor is arranged for detecting the presence of blood in the venous branch or a second sensor is arranged for detecting the presence of blood in the arterial branch of the extracorporeal circulation, wherein either the detection of the presence of blood by the first sensor and / or the second sensor indicates that the switching point has been reached.

6. Device according to one of the preceding claims, wherein in the first phase blood is drawn in only to the extent that a predetermined buffer volume of priming fluid remains in the extracorporeal circuit.

7. Device according to one of the preceding claims, wherein in the second phase an intermittent pressure measurement and not a continuous pressure measurement is performed.

8. Device according to one of the preceding claims, wherein the control unit is designed to cause the aspiration of blood through the arterial branch and / or the venous branch of the extracorporeal circulation preferably simultaneously or serially to the same extent.

9. Device according to claim 8, wherein the control unit is designed to monitor a pressure difference between the arterial branch and the venous branch during the aspiration of blood through the arterial branch and the venous branch in order to detect deviations in the flow rates in the arterial branch and the venous branch.

10. Device according to one of the preceding claims, wherein the control unit is designed to detect an absolute suction pressure in the venous line downstream of the dialyzer during the second phase and to compare it with a limit value, wherein, if the absolute suction pressure exceeds the limit value, the aspiration of the blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

11. Device according to one of the preceding claims, wherein the control unit is designed to detect a change, preferably a decrease, in the suction pressure in the venous line downstream of the dialyzer during the second phase and to compare it with a limit value, wherein, if the decrease in suction pressure exceeds the limit value, the aspiration of blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

12. Device according to one of the preceding claims, wherein the control unit is designed to perform an evaluation of the pressure amplitudes on the blood side upstream and / or downstream of the dialyzer during the second phase, wherein, if the evaluation indicates an increase in the magnitude of the pressure amplitudes upstream of the dialyzer, preferably relative to the pressure amplitudes downstream of the dialyzer, the aspiration of the blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

13. Device according to claim 12, wherein the evaluation comprises a determination of a relative size difference of the pressure amplitudes on the blood side upstream and downstream of the dialyzer, which is preferably expressed in percent or an absolute value, wherein the relative size difference of the pressure amplitudes is preferably compared with a limit value and if the limit value is exceeded, the aspiration of the blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

14. Device according to one of the preceding claims, wherein the control unit is designed to perform an evaluation of the power consumption of the blood pump and / or a transmembrane pressure of the dialyzer membrane during the second phase, wherein, if the power consumption of the blood pump and / or the measured transmembrane pressure exceeds a limit value, the aspiration of blood is initially stopped and the dialysis machine preferably switches to a treatment mode.

15. Device according to any one of claims 10 to 14, wherein the control unit is designed to perform such control that at the time when the dialysis machine switches to a treatment mode, a residual volume of priming fluid remains in the extracorporeal circuit.

16. Device according to one of the preceding claims, wherein the control unit is designed to automatically perform an aspiration test to verify a correct execution of an arterial and / or venous needle connection, preferably before a method for removing priming fluid from the extracorporeal circuit by aspirating blood is performed.

17. Device according to claim 16, wherein in the aspiration test a predetermined volume of blood is aspirated into a chamber separate from the dialyzer, wherein a pressure, in particular a pressure drop, in an arterial or venous line carrying the aspirated blood is monitored by means of at least one sensor and at least one pressure measurement is compared with a limit value and / or a target range.

18. Device according to claim 17, wherein the control unit is configured to automatically initiate a process for displacing priming fluid from the extracorporeal circuit when a correct execution of the arterial and / or venous needle connection has been detected based on the measured pressure and / or pressure drop.

19. Method for determining an endpoint of a priming process of an extracorporeal blood treatment device, wherein the method comprises at least two separate phases, wherein in the first phase a pressure-independent aspiration of blood is performed and upon reaching a switching point, a switch is made to a second phase, wherein in the second phase a pressure-controlled aspiration of blood is performed.

20. Method according to claim 19, wherein in the second phase the aspiration of blood is carried out based on a blood-side pressure measurement.

21. Method according to claim 19 or 20, wherein in the second phase the aspiration of blood is carried out based on a hydraulic pressure measurement.

22. Method according to any one of claims 19 to 21, wherein the method is carried out by means of a control unit of a device according to any one of claims 1 to 18.

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