Extracorporeal blood treatment device and method for monitoring pressure in extracorporeal blood treatment device

Abstract

An extracorporeal blood treatment device comprises: at least one pressure sensor (24, 25) located at a respective measurement site on an extracorporeal blood circuit (6, 7); an electronic control unit (23) operably connected at least to the pressure sensors (24, 25). The electronic control unit (23) is configured to perform at least the following processes: receiving a signal relating to a measured blood pressure (P1 measurement, P2 measurement) in a measurement site from the pressure sensor (24, 25); the measured blood pressure (P1 measurement, P2 measurement) is corrected by a mathematical correction model to obtain an actual blood pressure (Pinlet, Poutlet) in a reference site other than the measured site. A circuit section and optionally at least one additional device (18, 27, 28) are positioned between the reference point and the measurement point. The mathematical correction model is a model of the pressure drop in the circuit section and optionally in the additional device (18, 27, 28).

Description

[0001] This application is a divisional application of Chinese invention patent application No. 201980067179.3, entitled “Extracorporeal blood treatment device and method for monitoring pressure in an extracorporeal blood treatment device”, filed on October 11, 2019. Technical Field

[0002] The invention relates to an extracorporeal blood treatment apparatus and to a method for monitoring the pressure in an extracorporeal blood treatment apparatus.

[0003] In particular, the invention relates to the correction of measured pressure in order to monitor actual pressure.

[0004] Extracorporeal blood treatment involves: drawing blood from a patient; processing the blood outside the patient; and returning the processed blood to the patient. Extracorporeal blood treatment is generally used to extract undesirable substances or molecules from a patient's blood and to add desirable substances or molecules to the blood. Extracorporeal blood treatment is used for patients who cannot effectively remove substances from their blood, such as when the patient suffers from temporary or permanent renal failure. These and other patients may undergo extracorporeal blood treatment to add or remove substances from their blood, to maintain acid / base balance or to remove excess body fluids, or, for example, to perform an extracorporeal gas exchange process.

[0005] Extracorporeal blood treatment is usually accomplished by extracting blood from a patient, for example in a continuous flow; introducing the blood into a main chamber (also referred to as a blood chamber) of a treatment unit (such as a dialyzer or a blood filter), where the blood is allowed to flow through a semipermeable membrane. Depending on the type of treatment, the semipermeable membrane selectively allows substances in the blood to pass through the membrane from the primary chamber into the secondary chamber, and also selectively allows substances in the secondary chamber to pass through the membrane into the blood in the primary chamber.

[0006] During extracorporeal blood treatment treatments, pressure is monitored to ensure proper functioning of the equipment and / or to allow diagnosis of malfunctions and failures.

[0007] In particular, when operating with a membrane device, the pressure drop (DP) and the transmembrane pressure (TMP) can be monitored for the purpose of diagnosing clogging of the blood processing device (wherein clogging of the device may be caused by accumulation of material in the filter due to overfiltration during long-term operation), coagulation and / or preventing the risk of fiber rupture. Background Art

[0008] These measurements are performed using pressure sensors located in the blood circuit upstream and downstream of the blood treatment device and pressure sensors located in the fluid circuit.

[0009] The sensors in the blood circuit (in the blood extraction line and in the blood return line) may be spaced apart from the blood treatment device. Tube segments between the pressure sensor and the blood treatment device as well as additional accessories in the blood circuit (e.g. blood warming devices) and / or the development of combination therapies integrating several blood treatment devices in series may introduce deviations in the pressure measurement performed by the pressure sensor.

[0010] Therefore, the pressure drop (DP) and transmembrane pressure (TMP) provided by the system through the above-mentioned pressure sensors are not accurate values ​​(they are overestimated or underestimated). Usually, these values ​​are overestimated due to the presence of a neglected pressure drop in series with the blood treatment device and between the upstream pressure sensor and the downstream pressure sensor. When guided by the occurrence of a coagulation / clotting alarm or a TMP too high alarm, this overestimated value can lead to a potential reduction in processing time.

[0011] Document US2013 / 0006128 discloses a monitoring device included in a medical system to implement a method for predicting a rapid symptomatic drop in a subject's blood pressure during a medical treatment such as dialysis. Pulse shape parameters relative to the subject's pulse generator (heart) are recorded by a pressure sensor arranged in an extracorporeal blood flow circuit connected to the subject's cardiovascular system. The pressure sensor is configured to detect pressure changes in the subject's blood vessels. During a measurement cycle, one or more pulse shape parameters are investigated to determine whether they meet a decision criterion. If it is found that the decision criterion indicates an expected rapid symptomatic drop in blood pressure in the subject, an output is generated. The decision criterion may operate on a pulse amplitude measurement calculated for the received pulse shape parameters, or on a statistically discrete measurement calculated based on the pulse amplitude measurement so calculated.

[0012] Document US2017 / 0065760 shows an apparatus for extracorporeal blood treatment, which has a treatment unit, a blood extraction line and a blood return line, an infusion line for a replacement fluid and a fluid evacuation line connected to the treatment unit. A regulating device for the transmembrane pressure is effective on one of these lines, and the control unit is configured to command the regulating device by setting a first increment, determine the value of a control parameter corresponding to the first increment, compare the value of the control parameter with a reference value, and if the value of the control parameter is greater than the reference value, command the regulating device by setting a second increment greater than the first increment. Summary of the invention

[0013] In view of the above, one object according to an embodiment of the present invention is to improve the accuracy of blood treatment in an extracorporeal blood treatment apparatus.

[0014] It is an object of embodiments according to the invention to improve the control of the accuracy and reliability of pressure measurements in an extracorporeal blood treatment apparatus.

[0015] In particular, one object is to provide more accurate pressure drop (DP) and trans-membrane pressure (TMP) information.

[0016] Another object is to provide pressure drop (DP) and trans-membrane pressure (TMP) measurements independent of the presence of additional devices and / or tube sections.

[0017] Another objective is to develop better fault diagnostics (e.g. clotting) based on pressure drop (DP) and trans-membrane pressure (TMP) information. This can reduce costs by avoiding premature TMP or clotting alarms and enabling longer use of disposable devices.

[0018] Another object is to provide said object without affecting the cost of the extracorporeal blood treatment apparatus.

[0019] At least one of the above objects is substantially achieved by correcting the pressure measurements using an estimate of the pressure drop (due to additional devices, such as a blood warming device or a gas exchanger and / or a tube segment) derived from a mathematical model of the pressure drop in the additional device and / or in a circuit segment connecting the device.

[0020] In particular, at least one of the above objects is substantially achieved by an extracorporeal blood treatment apparatus and a method for monitoring the pressure in an extracorporeal blood treatment apparatus according to one or more of the appended claims.

[0021] Several aspects of the present invention are disclosed below.

[0022] According to a first independent aspect, an extracorporeal blood treatment apparatus comprises:

[0023] Blood processing equipment;

[0024] an extracorporeal blood circuit connected to a blood processing device;

[0025] a blood pump, the pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump;

[0026] Optionally, a treatment fluid circuit operatively connected to an extracorporeal blood circuit and / or a blood treatment apparatus;

[0027] a pressure sensor located in a measuring site on the extracorporeal blood circuit;

[0028] an electronic control unit operatively connected to at least the pressure sensor;

[0029] The electronic control unit is configured to perform at least the following processes:

[0030] - receiving a signal from a pressure sensor related to the measured pressure in the measurement site;

[0031] - determining a pressure drop between the measuring site and a reference site other than the measuring site, the reference site being a site on the extracorporeal blood circuit, wherein a circuit segment and optionally at least one additional device are located between the reference site and the measuring site.

[0032] In a further embodiment according to one of the preceding embodiments, the pressure drop is determined by means of a mathematical correction model of the pressure drop in the circuit section and optionally in the additional device.

[0033] According to a first independent aspect, an extracorporeal blood treatment apparatus comprises:

[0034] Blood processing equipment;

[0035] an extracorporeal blood circuit connected to a blood processing device;

[0036] a blood pump, the pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump;

[0037] Optionally, a treatment fluid circuit operatively connected to an extracorporeal blood circuit and / or a blood treatment apparatus;

[0038] a pressure sensor located in a measuring site on the extracorporeal blood circuit;

[0039] an electronic control unit operatively connected to at least the pressure sensor;

[0040] The electronic control unit is configured to perform at least the following processes:

[0041] - receiving a signal from a pressure sensor related to the measured pressure in the measurement site;

[0042] - Correcting the measured pressure by means of a mathematical correction model to obtain the actual pressure in a reference location other than the measuring location; wherein a circuit segment and optionally at least one additional device are positioned between the reference location and the measuring location; wherein the mathematical correction model is a model of the pressure drop in the circuit segment and optionally in the additional device.

[0043] According to a second independent aspect, a method for monitoring the pressure in an extracorporeal blood treatment apparatus is disclosed.

[0044] Wherein, the extracorporeal blood treatment equipment comprises:

[0045] Blood processing equipment;

[0046] an extracorporeal blood circuit connected to a blood processing device;

[0047] a blood pump, the pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump;

[0048] Optionally, a treatment fluid circuit operatively connected to an extracorporeal blood circuit and / or a blood treatment apparatus;

[0049] at least one pressure sensor located in a corresponding measuring position on the extracorporeal blood circuit;

[0050] Wherein, the method comprises:

[0051] - receiving a signal from a pressure sensor related to the measured blood pressure in the measurement site;

[0052] - Correcting the measured blood pressure by means of a mathematical correction model to obtain the actual blood pressure in a reference site other than the measurement site; wherein a circuit segment and optionally at least one additional device are positioned between the reference site and the measurement site; wherein the mathematical correction model is a model of the pressure drop in the circuit segment and optionally in the additional device.

[0053] In a further embodiment according to one of the preceding embodiments, the reference site is a reference site on the extracorporeal blood circuit.

[0054] In a further embodiment according to one of the preceding embodiments, the reference site is closer to the blood treatment device than the measuring site.

[0055] In a further embodiment according to one of the preceding embodiments, the measuring point is located at a position between the blood pump and the blood treatment device.

[0056] In a further aspect according to one of the preceding aspects, the electronic control unit is configured to calculate the transmembrane pressure of the blood treatment device as a function of the actual blood pressure in the reference site.

[0057] In another embodiment according to one of the aforementioned embodiments, the electronic control unit is configured to calculate the transmembrane pressure of the blood treatment device based on the measured blood pressure in the measuring site and the determined pressure drop between the measuring site and the reference site, in particular the average value of the measured blood pressure in the measuring site and the determined pressure drop.

[0058] In a further embodiment according to one of the preceding embodiments, the device comprises an auxiliary pressure sensor located at an auxiliary measuring site in the extracorporeal blood treatment or in the treatment fluid circuit, wherein the electronic control unit is configured to:

[0059] receiving a signal from an auxiliary pressure sensor related to a measured auxiliary pressure in an auxiliary measurement location;

[0060] Optionally, correcting the measured auxiliary pressure by means of an auxiliary mathematical correction model to obtain an actual auxiliary pressure in an auxiliary reference location other than the auxiliary measurement location; wherein an auxiliary circuit segment and optionally at least one additional device are located between the auxiliary reference location and the auxiliary measurement location; wherein the auxiliary mathematical correction model is a model of the auxiliary pressure drop in the auxiliary circuit segment and optionally in the additional device;

[0061] Optionally, determining an auxiliary pressure drop between the auxiliary measurement location and the auxiliary reference location;

[0062] The transmembrane pressure of the blood treatment device is calculated as follows:

[0063] - Either the actual blood pressure in the reference site; or the measured blood pressure in the measurement site and the measured blood pressure

[0064] a determined pressure drop between the location and a reference location; and

[0065] - either the actual pressure in the auxiliary reference location; or the measured pressure in the auxiliary measuring location and the determined pressure drop between the auxiliary measuring location and the auxiliary reference location; or the measured pressure in the auxiliary measuring location.

[0066] In another embodiment according to the aforementioned embodiment, the extracorporeal blood circuit includes a blood extraction line and a blood return line, the pressure sensor is located on the blood extraction line or on the blood return line, and the auxiliary pressure sensor is located on the other of the blood extraction line and the blood return line.

[0067] In another embodiment according to the aforementioned embodiment, the extracorporeal blood circuit comprises a blood extraction line and a blood return line, the pressure sensor is located on the blood extraction line or on the blood return line, and the auxiliary pressure sensor is located on the treatment fluid circuit, in particular on the waste liquid line of the treatment fluid circuit.

[0068] In another aspect according to one of the preceding aspects, the electronic control unit is configured to process a signal related to the measured blood pressure in the measurement site to obtain an average value of the blood pressure in the measurement site.

[0069] In a further aspect according to one of the preceding aspects, the electronic control unit is connected to the pressure sensor located in the measuring site and to the blood pump and is configured to:

[0070] The blood pump is moved to generate a variable blood flow, the variable blood flow comprising a constant flow component of a desired blood flow value and a variable flow component having a mean value that is substantially zero, the variable blood flow generating a pressure progression (pressure change, pressure series) at least in the measurement site, the pressure progression being time-varying (P(t)) and comprising a pressure change between the mean value (P avg ) is the pressure component ΔP(t) oscillating around;

[0071] Receive a plurality of pressure values ​​(P) from a pressure sensor for a time period (T) j ), the time period includes at least one and in particular a plurality of average values ​​(P avg ) around the pressure oscillation, the pressure value (P j ) at successive moments (time instants, time points) (t j )Measurement.

[0072] For example, for each calculation of the pressure mean, a time period of 3-7 oscillations is used. It should be noted that a time period shorter than one pressure oscillation caused by the blood pump may be used if it is sufficient to determine the mean pressure value.

[0073] In another embodiment according to one of the preceding embodiments, the signal related to the measured pressure in the measuring site comprises (ie is) a pressure progression which is a function of time (P(t)) and which includes a mean value (P avg ) is the pressure component ΔP(t) that oscillates around.

[0074] In another embodiment according to one of the three embodiments described above, the electronic control unit is configured to correct the average value of the measured pressure (P avg ).

[0075] In another embodiment according to one of the four embodiments described above, the electronic control unit is configured to determine an average value (P avg ) pressure drop.

[0076] In a third embodiment according to one of the preceding embodiments, the circuit segment is a tube segment, wherein, optionally, the length of the tube segment is between 200 mm and 1000 mm, wherein, optionally, the circuit segment comprises one or more connectors, such as male / female Luer connectors.

[0077] In a 4th embodiment according to one of the preceding embodiments, the at least one additional device is a blood warming device, or a gas exchanger, or a blood perfusion device, or another additional blood treatment device; wherein, optionally, the blood warming device comprises a blood warming bag or box or the blood warming device is configured to be connected to the blood warming bag or box, and the blood warming bag or box defines a blood path.

[0078] In a 5th aspect according to one of the preceding aspects, the apparatus comprises an additional device or is configured to be connected to the additional device.

[0079] In a sixth aspect according to one of the aforementioned aspects, the extracorporeal blood circuit includes a blood extraction line and a blood return line, and the pressure sensor is located on the blood extraction line and / or the blood return line.

[0080] In a 7th embodiment according to the aforementioned embodiment, the blood processing device has a blood inlet port connected to a blood extraction line and a blood outlet port connected to a blood return line, and optionally, the pressure sensor is spaced apart from the blood inlet port and / or from the blood outlet port, optionally at a distance between 200 mm and 1000 mm.

[0081] In an eighth aspect according to the preceding aspects, the blood processing apparatus includes a blood chamber and a fluid chamber, the blood chamber and the fluid chamber being separated from each other by a semipermeable membrane, wherein the blood chamber has a blood inlet port and a blood outlet port.

[0082] In a ninth aspect according to any one of the aforementioned aspects 6, 7, or 8, the pressure sensor comprises a first pressure sensor, and the first pressure sensor is located on the blood extraction pipeline upstream of the blood processing device.

[0083] In a tenth aspect according to the preceding aspect, the pressure sensor comprises a second pressure sensor, and the second pressure sensor is located on the blood return line downstream of the blood processing device.

[0084] In the 11th embodiment according to the aforementioned embodiment 9 or 10, the method includes or the electronic control unit is configured to perform at least the following process:

[0085] - receiving a signal from a first pressure sensor related to a first measured blood pressure upstream of the blood treatment device;

[0086] - Correcting the first measured blood pressure by a first mathematical correction model to obtain a first actual blood pressure (P) at the blood inlet port of the blood treatment device 入口 ).

[0087] In the 11A embodiment according to the above embodiment 9 or 10, the method includes or the electronic control unit is configured to perform at least the following process:

[0088] - receiving a signal from a first pressure sensor related to a first measured blood pressure upstream of the blood treatment device;

[0089] - determining a first pressure drop between a measuring site of the first pressure sensor and a reference site outside the measuring site, in particular the reference site being closer to the blood treatment unit than the measuring site, a first actual blood pressure (P 入口 ) is a function of the first measured blood pressure and the first pressure drop, and can be obtained through a first mathematical correction model.

[0090] In a 12th aspect according to any one of the aforementioned aspects 10 or 11 (when according to aspect 10), the method includes or the electronic control unit is configured to perform at least the following process:

[0091] - receiving a signal from a second pressure sensor related to a second measured blood pressure downstream of the blood treatment device;

[0092] - Correcting the second measured blood pressure by a second mathematical correction model to obtain a second actual blood pressure (P 出口 ).

[0093] In the 12A embodiment according to any one of the above embodiments 10 or 11 (when according to embodiment 10), the method includes or the electronic control unit is configured to perform at least the following process:

[0094] - receiving a signal from a second pressure sensor related to a second measured blood pressure downstream of the blood treatment device;

[0095] - determining a second pressure drop between a measuring site of the second pressure sensor and a reference site other than the measuring site, in particular the reference site being closer to the blood treatment unit than the measuring site, a second actual blood pressure (P 出口 ) is a function of the second measured blood pressure and the second pressure drop, and can be obtained by a second mathematical correction model.

[0096] In the 13th scheme according to the aforementioned scheme 12 (when according to scheme 11), the method includes or the electronic control unit is configured to perform at least the following processes: calculating the actual pressure drop of the blood treatment device as the difference between the first actual blood pressure and the second actual blood pressure; and optionally, triggering an alarm if the actual pressure drop is outside the pressure drop safety range.

[0097] In a 14th embodiment according to Embodiment 8 or any one of Embodiments 9 to 13 (when according to Embodiment 8), the fluid chamber has at least one fluid outlet port, and the processing fluid circuit includes a waste liquid pipeline connected to the fluid outlet port of the fluid chamber to receive the waste fluid after filtering through the semipermeable membrane.

[0098] In a 15th aspect according to aspect 8 or according to any one of aspects 9 to 14 (when according to aspect 8), the fluid chamber has at least one fluid inlet port, and the treatment fluid circuit includes a dialysis line connected to the fluid inlet port of the fluid chamber.

[0099] In the 16th embodiment according to the aforementioned embodiment 14 or according to embodiment 15 (when according to embodiment 14), the device includes at least one waste liquid pressure sensor, the waste liquid pressure sensor is placed on the waste liquid pipeline, and the method includes or the electronic control unit is configured to perform at least the following processes: receiving from the waste liquid pressure sensor a signal related to the pressure of the filtered waste fluid (P 废液 ) related signals.

[0100] In the 17th embodiment according to the aforementioned embodiment 16, the method includes or the electronic control unit is configured to perform at least the following processes: calculating the actual path transmembrane pressure of the blood processing device as the difference between the first actual blood pressure and the pressure of the filtered waste fluid; and optionally, triggering an alarm if the actual transmembrane pressure falls outside the path transmembrane pressure safety range.

[0101] In an 18th aspect according to aspect 16 (when according to aspect 15), the electronic control unit is configured to perform at least the following process: 入口 +P 出口 ) / 2)–P 废液 , to calculate the actual transmembrane pressure of the blood treatment device; and optionally, if the actual transmembrane pressure falls outside the actual transmembrane pressure safety range, an alarm is triggered.

[0102] In a 19th aspect according to any one of the preceding aspects, the degassing chamber is placed on the blood return line and / or in the blood extraction line.

[0103] In a 20th aspect according to the preceding aspect, the pressure sensor (optionally the second pressure sensor or the first pressure sensor) is positioned in the degassing chamber.

[0104] In a 21st aspect according to the preceding aspects, the reference site is at a blood outlet port of the blood processing device.

[0105] In a 22nd aspect according to aspect 20 or 21, the at least one additional device is placed on the blood return line between the blood treatment device and the degassing chamber. Optionally, the at least one additional device is placed on the blood extraction line between the degassing chamber and the blood treatment device.

[0106] In a 23rd aspect according to any one of the preceding aspects, the mathematical correction model is built from physical equations.

[0107] In a 24th aspect according to any of the preceding aspects, the mathematical correction model is a function of the geometry of the loop segment, optionally a function of the size and loss coefficient.

[0108] In a 25th aspect according to any of the preceding aspects, the mathematical correction model is a function of the geometry of the additional device, optionally a function of the size and loss coefficient.

[0109] In a 26th aspect according to any one of the preceding aspects, the mathematical correction model is a function of blood movement or dynamic viscosity associated with the circuit segment or additional device.

[0110] In a 27th aspect according to any of the preceding aspects, the mathematical correction model is a function of the blood flow rate in the circuit segment or in the additional device.

[0111] In a 28th embodiment according to any one of the preceding embodiments, the mathematical correction model is a function of blood hematocrit.

[0112] In a 29th embodiment according to any of the preceding embodiments, the mathematical correction model is a function of the optionally measured or estimated blood temperature.

[0113] In a 30th embodiment according to any of the preceding embodiments, the mathematical calibration model is a function of blood protein concentration, optionally albumin or total protein.

[0114] In a 31st embodiment according to the preceding embodiment (when according to embodiment 26), the motion or dynamic blood viscosity is estimated and optimized by blood temperature and / or blood protein concentration.

[0115] In a 32nd embodiment according to any one of the preceding embodiments, the mathematical correction model is a function of blood density.

[0116] In a 33rd embodiment according to the preceding embodiments, the blood density is estimated based on the blood hematocrit and water density and optionally the blood protein concentration.

[0117] In the 34th embodiment according to any one of the aforementioned embodiments 1 to 22, the mathematical correction model is an experimental model of measurement error derived from multiple experimental data sets, and the measurement error is the difference between the measured blood pressure in the measurement site and the actual blood pressure in the reference site.

[0118] In a 35th embodiment according to the preceding embodiment, the mathematical correction model is derived from a regression analysis of measurement errors collected through the plurality of experimental data sets versus one or more parameters collected through the plurality of experimental data sets.

[0119] In a 36th embodiment according to the preceding embodiment, the parameters include the measured blood pressure and at least one other operating parameter of the extracorporeal blood treatment apparatus and / or an additional device.

[0120] In a 37th embodiment according to the preceding embodiment, the at least one other operating parameter includes blood flow rate.

[0121] In a 38th aspect according to any one of the preceding aspects, the blood treatment device is a blood filter or a hemodialysis filter or a plasma filter or a dialysis filter or an absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] The following drawings are provided in connection with aspects of the present invention by way of non-limiting examples:

[0123] Figure 1 An extracorporeal blood treatment apparatus according to the invention is shown;

[0124] Figure 2 Shows Figure 1 Blood warming device for extracorporeal blood treatment equipment;

[0125] Figure 3 Shows an insertable Figure 2 A blood warming bag in a blood warming device;

[0126] Figure 4 A schematic diagram showing a part of an extracorporeal blood treatment apparatus according to the invention;

[0127] Figure 5 is a flow chart showing the steps of a method according to the present invention. DETAILED DESCRIPTION

[0128] With reference to the accompanying drawings, Figure 1 A schematic diagram of an extracorporeal blood treatment apparatus 1 is shown.

[0129] The apparatus 1 comprises a blood treatment device 2 , such as a blood filter, a hemodiafiltration filter, a plasmafilter, a diafiltration filter, an absorber or another unit suitable for treating blood collected from a patient P.

[0130] The blood treatment device 2 has a first compartment or blood chamber 3 and a second compartment or fluid chamber 4, which are separated from each other by a semipermeable membrane 5. A blood extraction line 6 is connected to an inlet port 3a of the blood chamber 3 and is configured to, in an operating state connected to a patient P, extract blood from a vascular access device, for example inserted in a fistula of the patient P. A blood return line 7 connected to an outlet port 3b of the blood chamber 3 is configured to receive processed blood from the treatment unit 2 and return the processed blood to another vascular access, for example also connected to a fistula of the patient P. It should be noted that various configurations of vascular access devices can be envisaged: for example, a typical access device includes a needle or a catheter inserted into a vascular access, which can be a fistula, a graft or a central vein (e.g., a jugular vein) or a peripheral vein (femoral vein) or the like.

[0131] The blood withdrawal line 6 and the blood return line 7 are part of the extracorporeal blood circuit of the apparatus 1. The extracorporeal blood circuit 6, 7 and the treatment unit 2 are usually disposable components which are loaded onto a frame of a blood treatment machine not shown.

[0132] like Figure 1 As shown, the device 1 comprises at least one first actuator, in this example a blood pump 8, which is part of the machine and operates at the blood extraction line 6 to cause blood extracted from the patient P to move from a first end of the extraction line 6 connected to the patient P to the blood chamber 3. Figure 1 As shown, the blood pump 8 is, for example, a peristaltic pump which acts on a corresponding pump section of the extraction line 6 .

[0133] It should be noted that for the purposes of the present description and the appended claims, the terms "upstream" and "downstream" may be used with reference to the relative positions occupied by components belonging to or operating on the extracorporeal blood circuit. These terms are to be understood with reference to the direction of blood flow from a first end of the blood extraction circuit 6 connected to the patient P toward the blood chamber 3, and then from the blood chamber 3 toward a second end of the blood return circuit 7 connected to the vascular access of the patient P.

[0134] The device 1 may also comprise an air capture device operating on the blood return line 7. The air capture device may be a venous degassing chamber 9. The degassing chamber 9 is placed in-line in the blood return line 7.

[0135] A first section of the blood return line 7 fluidly connects the outlet port 3b of the blood chamber 3 with the degassing chamber 9, and a second section of the blood return line 7 fluidly connects the degassing chamber 9 with the patient P. Blood from the blood chamber 3 of the processing device 2 enters and leaves the degassing chamber 9 before reaching the patient P.

[0136] An air capture device may also be present on the blood extraction line. The air capture device ensures that the blood is substantially free of air / bubbles before entering the blood treatment device 2.

[0137] Figure 1 The device 1 also includes a waste liquid pipeline 10, which is connected to the fluid outlet port 4b of the fluid chamber 4 to receive the waste fluid after filtering through the semipermeable membrane 5. The waste liquid pipeline 10 receives such filtered waste fluid from the fluid chamber 4 of the treatment device 2, for example, the filtered waste fluid includes spent dialysis fluid and / or liquid ultrafiltered through the membrane 5. The waste liquid pipeline 10 leads to a receiving element (not shown), which has, for example, a collection bag or a discharge tube for the waste fluid. One or more dialysate pumps (not shown) can be operated on the waste liquid pipeline 10.

[0138] exist Figure 1 In the example of the treatment device 2, there is also a dialysis line 11 for supplying fresh treatment fluid into the fluid inlet port 4a of the fluid chamber 4. The presence of this dialysis line 11 is not strictly necessary, because the device 1 is still able to perform treatments such as ultrafiltration, hemofiltration or plasmafiltration in the absence of the dialysis line 11. In the presence of the dialysis line 11, a fluid shut-off device (not shown) can be used to selectively allow or inhibit fluid from passing through the dialysis line 11, depending on whether purification by diffusion is to be performed in the treatment device 2.

[0139] If present, the dialysis line 11 is typically equipped with a dialysis pump and is capable of receiving fresh fluid from a module (not shown), such as a bag of dialysis fluid or an online preparation section, and sending such fluid to the fluid inlet port 4a of the fluid chamber 4. The waste line 10, the dialysis line 11 and the fluid chamber 4 are part of a treatment fluid circuit 12. Figure 1 The device 1 shown also comprises an infusion circuit comprising one or more infusion lines for the replacement fluid. Figure 1 In the embodiment of the present invention, the front infusion line 13 is connected to the blood extraction line 6 between the blood pump 8 and the inlet port 3a of the blood chamber 3. The front pump infusion line 14 is connected to the blood extraction line 6 between the blood pump 8 and the vascular access device inserted in the fistula on the patient P upstream of the blood pump 8. The rear infusion lines 15, 16 are connected to the blood return line 7 for performing HF or HDF treatment. Typically, one or two rear infusion lines are used to connect upstream of the air capture device 9 or to the air capture device. Figure 1The rear infusion line is shown to include a first branch 15 and a second branch 16. Each of the front and / or rear infusion lines 13, 14, 15, 16 is provided with a corresponding pump (not shown). The front and / or rear infusion lines 13, 14, 15, 16 can be supplied with fluid from a bag or directly with an infusion fluid prepared online. Each of the front and / or rear infusion lines 13, 14, 15, 16 is part of the processing fluid circuit 12. The specific configuration of the front and rear infusion circuits can of course vary with the present invention. Figure 1 The blood return line 7 has a heating zone, for example placed between the first branch 15 and the second branch 16 of the post-infusion line. In said heating zone, the blood is warmed before flowing into the blood circulation system of the patient P.

[0140] In the embodiment shown in the drawings, the heating portion is a part of a disposable blood warming bag 17, which is inserted into a blood warming device 18 ( Figure 2 and Figure 3 The blood warming device 18 is connected to the extracorporeal blood treatment apparatus 1 or is a part of the extracorporeal blood treatment apparatus.

[0141] The blood warming bag 17 can be set in the blood warming device 18 ( Figure 2 and Figure 3 ) is a basically flat and soft bag inserted into the narrow slot 19 in the heating seat.

[0142] The blood warming bag 17 has an outlet 21 connected to the extracorporeal blood circuit and an inlet 20. For example, the blood warming bag 17 includes two plastic sheets (e.g., polyurethane or polyvinyl chloride) that are stacked and welded to form a bag, and a blood warming path 22 defined by the two sheets and the weld line is formed in the bag.

[0143] The device 1 further comprises an electronic control unit 23. The electronic control unit 23 may comprise a digital processor (CPU) and a memory (or multiple memories), an analog circuit or a combination thereof, and an input / output interface. The control unit 23 is configured to control the device 1 during the patient blood treatment by means of software stored in the control unit 23. Figure 1 In the embodiment of FIG. 1 , the electronic control unit 23 is connected at least to the blood pump 8 and to a power control unit (not shown) of the blood warming device 18 .

[0144] The first pressure sensor 24 is located on the blood extraction line 6 upstream of the blood treatment device 2 and downstream of the blood pump 8. The first pressure sensor 24 may be close to the blood inlet port 3a (the length of the tube between the first pressure sensor 24 and the blood inlet port may be only a few centimeters), or may be spaced apart from the blood inlet port (the tube section between the first pressure sensor 24 and the blood inlet port may be several decimeters, for example 200 mm).

[0145] The second pressure sensor 25 is located on the blood return line 6 downstream of the blood treatment device 2. Figure 1 In the embodiment of the present invention, the second blood pressure sensor 25 is placed in the degassing chamber 9. The degassing chamber 9 may include a housing that defines a blood volume, and the second pressure sensor 25 is placed on the upper portion of the degassing chamber 9, above the blood, to sense the pressure of a gas (e.g., air) filling the space above the free blood surface. The second pressure sensor 25 is spaced apart from the blood outlet port 3b (e.g., 1000 mm tube section), and further, a disposable blood warming bag 17 having a blood warming path 22 is placed between the blood outlet port 3b and the second pressure sensor 25.

[0146] If an air capture device / degassing chamber is also placed on the blood extraction line 6, the first blood pressure sensor 24 can be placed in the degassing chamber.

[0147] The tubing sections and possible connectors (eg male / female Luer connectors) create a pressure drop in the blood flowing through. The blood warming device 18 with the blood warming bag 17 is an additional device that allows blood to flow through and creates an additional pressure drop in the blood.

[0148] A waste pressure sensor 26 is also placed on the waste line 10 to sense the pressure of the waste fluid. In addition to or in place of the waste pressure sensor 26, a dialysis pressure sensor 26a may be located on the dialysis line 11.

[0149] In other embodiments, similar to Figure 4 In the embodiment schematically shown in FIG. 1 , another additional device 27 for generating a pressure drop can be placed on the blood extraction line 6, between the first pressure sensor 24 and the blood inlet port 3 a. Another additional device 28 for generating a corresponding pressure drop can also be placed on the blood return line 7, between the blood warming device 18 and the second pressure sensor 25.

[0150] The first pressure sensor 24 , the second pressure sensor 25 and the waste liquid pressure sensor 26 are operatively connected to the electronic control unit 23 to send signals related to the sensed pressures to the electronic control unit 23 .

[0151] At least during the treatment, the control unit moves the blood pump to generate a variable blood flow comprising a constant flow component equal to the desired blood flow value and a variable flow component having a mean value substantially equal to zero. This is due in particular to the fact that the blood pump is essentially a peristaltic pump and therefore generates a non-constant blood flow in the circuit, since it is associated with the continuous squeezing action of the pump segments by a roller / rollers associated with the pump rotor.

[0152] In other words, the hydraulic head of the treated fluid is given by the constriction extending along the tube. In one example, the pump consists of a rotor on which are applied two (or more) rollers which rotate to "squeeze" the tube and cause the fluid to advance. Alternatively, a linear peristaltic pump (e.g. a "finger" pump) or other actuators capable of producing a pulsatile movement in the blood, i.e. a non-constant flow, but oscillating around a mean flow value, may be used.

[0153] Alternatively, in order to use other types of pumps that do not have inherently generated pressure variations, the control unit can control the pump to generate pulsatile movements in the blood. Thus, the variable blood flow generates a pressure trend in the blood circuit, which is a time-varying P(t) that includes a mean value P avg The pressure component ΔP(t) of the nearby oscillations.

[0154] The control unit is programmed to receive a plurality of pressure values ​​P for a time period T (typically coinciding with a processing period) from the pressure sensors located at their respective locations. j . Measured pressure data P j The minimum time period used is T min Including at least one (especially more than one) in the average value P avg pressure oscillations around; in particular, as described below, a time period of 3-7 oscillations is used for each calculation of the average pressure value used in the TMP calculation.

[0155] Obviously, at discrete and continuous moments t j Medium measured pressure value P j Depending on the type of pressure sensor used and possibly other parameters of the device operation, the sampling timing may be constant.

[0156] According to the device and method of the present invention, the electronic control unit 23 is configured to receive corresponding signals related to the measured pressures in the corresponding parts from the first pressure sensor 24, from the second pressure sensor 25 and from the waste fluid pressure sensor 26 to correct at least one measured pressure and calculate the pressure difference, which is used to monitor the blood treatment process performed by the device 1.

[0157] In order to correct the measured blood pressure, one or more correction mathematical models or algorithms are developed in advance and stored in the memory of the electronic control unit 23 or connected to the electronic control unit 23. The mathematical correction model is a model of the pressure drop in the circuit section and in the additional device. Through the mathematical correction model, the actual pressure in the reference site other than the measurement site is obtained.

[0158] Reference Figure 1 In the embodiment, the electronic control unit 23 receives a first measured blood pressure (P1) upstream of the blood treatment device 2 from the first pressure sensor 24. 测量值 )-related signal, and correct the first measured blood pressure (P1) by the first mathematical correction model 测量值 ) to obtain the first actual blood pressure (P 入口 ).

[0159] The first correction model takes into account the pressure drop ΔPtL1 caused by the tube section of length L1 (eg, 200 mm) between the first pressure sensor 24 and the blood inlet port 3 a .

[0160] i)P 入口 =P1 测量值 -ΔPtL1

[0161] A first mathematical correction model of the pressure drop ΔPtL1 caused by the pipe section can be established from the following physical equation:

[0162] ii)ΔPtL1=f1(Qb,H,ξ1,ρ,η1)

[0163] in:

[0164] Qb is the blood flow rate;

[0165] H is blood hematocrit;

[0166] P is blood density;

[0167] ξ1 is the loss coefficient of the tube;

[0168] η1 is the kinematic viscosity in the tube.

[0169] Equation ii) also takes into account the geometry of the tubing and connectors (eg male / female Luer connectors).The blood density can be estimated from the blood hematocrit and the water density ρw.

[0170] The electronic control unit 23 receives a second measured blood pressure (P2 ) downstream of the blood treatment device 2 from the second pressure sensor 25. 测量值 ) and correct the second measured blood pressure (P2 测量值) to obtain the second actual blood pressure (P 出口 ).

[0171] The second correction model takes into account the pressure drop ΔPtL2 caused by the tube section with a length of L2 (e.g., 250 mm) between the blood outlet port 3b and the blood warming device 18, the pressure drop ΔPw caused by the blood warming path 22 of the blood warming bag 17, and the pressure drop ΔPtL3 caused by the tube section with a length of L3 (e.g., 250 mm) between the blood warming device 18 and the second pressure sensor 25.

[0172] iii) P 出口 =P2 测量值 +ΔPtL2+ΔPw+ΔPtL3

[0173] The physical equations of ΔPtL2 and ΔPtL3 are similar to ii).

[0174] iv)ΔPtL2=f2(Q,H,ξ2,ρ,η2)

[0175] ξ2 is the loss coefficient of the tube

[0176] η2 is the kinematic viscosity in the tube.

[0177] v)ΔPtL3=f3(Q,H,ξ3,ρ,η3)

[0178] ξ3 is the loss coefficient of the tube;

[0179] η3 is the kinematic viscosity in the tube.

[0180] The physical equation resulting from the blood warming bag is:

[0181] vi) ΔPw=f4(Q,H,ξ4,ρ,η4)

[0182] in:

[0183] Qb is the blood flow rate;

[0184] H is the blood hematocrit;

[0185] P is blood density;

[0186] ξ4 is the loss coefficient of the bag;

[0187] η4 is the kinematic viscosity in the bag.

[0188] Equation vi) also takes into account the geometry of the bag and the connector. The blood density can be estimated from the blood hematocrit and the water density ρw.

[0189] The kinematic viscosity description of blood includes the variables of shear rate, hematocrit and protein content of the blood. For the tube segment and bag, this gives:

[0190] vii)η1=f5(μpl,k1,ρ,H)

[0191] viii)η2=f6(μpl,k2,ρ,H)

[0192] in

[0193] μpl is the dynamic plasma viscosity, which can be defined based on the protein content Cp (eg albumin or total protein). Cp can also be estimated based on the hematocrit H.

[0194] k1, k2 are the shear-dependent intrinsic viscosities in the tube and bag, which can be defined as a function of the hematocrit H. To optimize the kinematic viscosity description, the blood temperature can also be included.

[0195] Therefore, in order to establish the physical equations for the calibration model (estimating the blood pressure drop in the different device / circuit segments), the required data may be:

[0196] H hematocrit value;

[0197] Qb blood flow rate;

[0198] ρw water density;

[0199] Cp protein content;

[0200] The geometry of the device / loop section (length, diameter, loss factor, etc.).

[0201] Depending on the infusion in the front and / or rear infusion lines 13 , 14 , 15 , 16 and / or the ultrafiltration in the blood treatment device 2 , the blood flow Qb, the hematocrit H, the temperature and the total protein concentration Cp can vary in individual sections of the blood circuit.

[0202] Alternatively, a more experimental approach can be used to establish a correction model. The mathematical correction model is an experimental model of the measurement error E derived from multiple experimental data sets (e.g., collected during development testing). The measurement error E can be the difference between the measured blood pressure in the measurement site and the actual blood pressure in the reference site.

[0203] An experimental mathematical calibration model is established by performing a plurality of test treatments. An experimental data set is collected for each test treatment. Each experimental data set includes one or more measured parameters.

[0204] A mathematical correction model can be derived from a regression analysis of the measurement error E collected through the plurality of experimental data sets relative to the parameters collected through the plurality of experimental data sets. The model will be as reliable as the large collection of experimental data sets. The regression model can be simplified to be linear with respect to the blood flow velocity Qb.

[0205] The electronic control unit 23 also receives a signal related to the measured pressure P3m of the waste fluid from the waste pressure sensor 26. The waste pressure sensor 26 is close to the fluid outlet port 4b, and the measured pressure P3m of the waste fluid can be regarded as the actual pressure (P 废液 ).

[0206] The electronic control unit 23 is programmed to convert the actual pressure drop (DP 实际 ) is calculated as the first actual blood pressure (P 入口 ) and the second actual blood pressure (P 出口 )

[0207] viii)DP 实际 =P 入口 -P 出口

[0208] If no correction of the measured pressure is performed, the measured pressure drop (DP measurement value) of the blood treatment device 2 will be:

[0209] ix) Dp measurement value = Dp 实际 +(ΔPtL1+ΔPtL2+ΔPw+ΔPtL3)

[0210] The actual pressure drop (Dp) relative to the blood treatment device 2 实际 ), the measured pressure drop (DP measurement value) of the blood treatment device 2 will be overestimated. 实际 ) can be, for example, between 50 mmHg and 200 mmHg.

[0211] The electronic control unit 23 is programmed to calculate the actual transmembrane pressure (TMP) of the blood treatment device 2 by the following formula: 实际 ):

[0212] x)TMP 实际 =((P 入口 +P 出口 ) / 2)–P 废液

[0213] If no correction of the measured pressure is performed, the measured transmembrane pressure (TMP measurement) will be:

[0214] xi) TMP measurement value = TMP 实际+((ΔPtL1–(ΔPtL2+ΔPw+ΔPtL3)) / 2)

[0215] Depending on the values ​​of ΔPtL1 and (ΔPtL2+ΔPw+ΔPtL3), relative to the actual transmembrane pressure (TMP 实际 ), the measured transmembrane pressure (TMP measurement value) will be overestimated or underestimated. 实际 ) can be, for example, between + / - 10 mmHg and + / - 50 mmHg.

[0216] If plasma exchange is performed, the electronic control unit 23 is programmed to calculate the actual passage transmembrane pressure (TMPa) of the blood treatment device 2 (plasma filter). 实际 ).

[0217] xii) TMPa 实际 =P 入口 –P 废液

[0218] If no correction of the measured pressure is performed, the measured path transmembrane pressure (TMPa measurement) will be:

[0219] xiii) TMPa measurement value = TMPa 实际 +ΔPtL1

[0220] Relative to the actual transmembrane pressure (TMPa 实际 ), the measured transmembrane pressure of the measured pathway (TMPa measurement value) will be overestimated. 实际 ) can be, for example, between 20 mmHg and 50 mmHg.

[0221] The actual pressure drop (DP 实际 ) and actual transmembrane pressure (TMP 实际 and TMPa 实际 ) for the purpose of diagnosing the risk of blockage (overfiltration), coagulation and / or preventing fibers in a blood treatment device.

[0222] For example, the electronic control unit 23 is configured to trigger an alarm if the actual pressure drop and / or the transmembrane pressure and / or the passage transmembrane pressure fall outside the corresponding safety range.

[0223] Figure 1 The example shown shows the pressure drop due to the tube section and due to the blood warming bag 17 of the blood warming device 1. In any case, the pressure drop may be caused by other devices on the extracorporeal blood circuit 6, 7, such as a gas exchanger, a blood perfusion device or others.

[0224] While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims

1. An extracorporeal blood treatment device, comprising: Blood processing device (2); an extracorporeal blood circuit connected to the blood treatment device (2), the extracorporeal blood circuit comprising: a blood extraction line (6) connected to a blood inlet port (3a) of the blood treatment device (2), and a blood return line (7) connected to a blood outlet port (3b) of the blood treatment device (2); a blood pump (8), the pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump (8); a first pressure sensor (24) located on the blood extraction pipeline (6) upstream of the blood treatment device (2); a second pressure sensor (25) located on the blood return line (7) downstream of the blood treatment device (2); an electronic control unit (23) operatively connected to at least the first pressure sensor (24); Wherein, the electronic control unit (23) is configured to perform at least the following processes: - receiving a first measured blood pressure P1 from the first pressure sensor (24) at the first measuring site 测量值 Related signals; - Correcting the first measured blood pressure P1 by a first mathematical correction model 测量值 , to obtain a first actual blood pressure P at a first reference site located at the blood inlet port (3a) of the blood treatment device (2) 入口 , the first reference site is different from the first measurement site, wherein a loop section is located between the first reference site and the first measurement site; wherein the first mathematical correction model is a model of the pressure drop in the loop section.

2. The device according to claim 1, wherein the electronic control unit (23) is operatively connected to the second pressure sensor (25) and is configured to perform at least the following processes: - receiving a second measured blood pressure P2 downstream of the blood treatment device (2) from the second pressure sensor (25) located at the second measurement site 测量值 Related signals; - Correcting the second measured blood pressure P2 by a second mathematical correction model 测量值 , to obtain the second actual blood pressure P at the second reference site 出口 , the second reference site is located at the blood outlet port (3b) of the blood treatment device (2) instead of the second measurement site, wherein a second circuit section is positioned between the second reference site and the second measurement site; wherein the second mathematical correction model is a model of the pressure drop in the second circuit section.

3. The device according to claim 2, wherein: The electronic control unit (23) is configured to perform at least the following processes: converting the actual pressure drop DP of the blood treatment device (2) into 实际 The first actual blood pressure P is calculated as 入口 The second actual blood pressure P 出口 The difference between.

4. The apparatus according to claim 1, further comprising a treatment fluid circuit (12) operatively connected to the extracorporeal blood circuit and / or the blood treatment device (2).

5. The device according to claim 4, wherein: The blood treatment apparatus (2) comprises a blood chamber (3) and a fluid chamber (4), wherein the blood chamber (3) and the fluid chamber (4) are separated from each other by a semipermeable membrane (5); wherein the blood chamber (3) has a blood inlet port (3a) and a blood outlet port (3b); wherein the fluid chamber (4) has at least a fluid outlet port (4b); wherein the treatment fluid circuit (12) comprises a waste fluid line (10), wherein the waste fluid line (10) is connected to the fluid outlet port (4b) of the fluid chamber (4) to receive the waste fluid after filtering through the semipermeable membrane (5); wherein the device (1) comprises a waste fluid pressure sensor (26), wherein the waste fluid pressure sensor (26) is placed on the waste fluid line (10); wherein the electronic control unit (23) is configured to perform at least the following processes: - receiving the pressure P of the filtered waste fluid from the waste fluid pressure sensor (26) 废液 Related signals.

6. The device according to claim 5, wherein: The electronic control unit (23) is configured to execute at least the following processes: converting the actual transmembrane pressure TMPa of the blood treatment device (2) into 实际 The first actual blood pressure P is calculated as 入口 The filtered waste fluid pressure P 废液 The difference between.

7. The device according to claim 5, wherein: The electronic control unit (23) is configured to perform at least the following processes: 实际 =((P 入口 +P 出口 ) / 2)-P 废液 Calculate the actual transmembrane pressure TMP of the blood treatment device (2) 实际 .

8. Apparatus according to any one of claims 1 to 7, wherein at least one additional device is positioned between the first reference site and the first measurement site.

9. The device according to claim 8, wherein: The at least one additional device is a blood warming device (18) and / or a gas exchanger and / or an additional blood treatment device.

10. The apparatus according to claim 8, comprising a degassing chamber (9) placed on the blood return line (7), and the second pressure sensor (25) is positioned in the degassing chamber (9); wherein the at least one additional device is placed on the blood return line (7) between the blood treatment device (2) and the degassing chamber (9).

11. The device according to any one of claims 1 to 7, wherein: The first reference site is closer to the blood processing device than the first measurement site.

12. The device according to any one of claims 1 to 7, wherein: The first measuring location is located between the blood pump and the blood treatment device.

13. The apparatus according to any one of claims 1 to 7, wherein: The electronic control unit is configured to calculate a transmembrane pressure of the blood treatment device based on a first actual blood pressure in the first reference site.

14. The apparatus according to any one of claims 1 to 7, wherein: The electronic control unit is configured to calculate a transmembrane pressure of the blood treatment device based on a first measured blood pressure in the first measurement site and a determined pressure drop between the first measurement site and the first reference site.

15. The apparatus according to claim 4, wherein: The device comprises an auxiliary pressure sensor located at an auxiliary measurement location in a process fluid circuit, wherein the electronic control unit is configured to: receiving a signal from the auxiliary pressure sensor related to the measured auxiliary pressure in the auxiliary measurement location; correcting the measured auxiliary pressure by means of an auxiliary mathematical correction model to obtain an actual auxiliary pressure in an auxiliary reference location different from the auxiliary measurement location; wherein an auxiliary circuit section is located between the auxiliary reference location and the auxiliary measurement location; wherein the auxiliary mathematical correction model is a model of the auxiliary pressure drop in the auxiliary circuit section; Determining an auxiliary pressure drop between the auxiliary measurement location and the auxiliary reference location; The transmembrane pressure of the blood treatment device is calculated according to: - either a first actual blood pressure in the first reference site; or a first measured blood pressure in the first measurement site and a determined pressure drop between the first measurement site and the first reference site; as well as - either the auxiliary actual pressure in the auxiliary reference location; or the measured pressure in the auxiliary measuring location and the determined pressure drop between the auxiliary measuring location and the auxiliary reference location; or the measured pressure in the auxiliary measuring location.

16. The apparatus of claim 15, wherein at least one additional device is positioned between the auxiliary reference site and the auxiliary measurement site.

17. The apparatus according to claim 15, wherein: The auxiliary pressure sensor is located on the waste line of the process fluid circuit.

18. The apparatus according to any one of claims 1 to 7, wherein: The electronic control unit is configured to process a signal related to a first measured blood pressure at the first measurement site to obtain an average value of the blood pressure in the first measurement site.

19. The apparatus according to any one of claims 1 to 7, wherein: The electronic control unit is connected to the first pressure sensor in the first measurement site and to the blood pump and is configured to: - moving the blood pump to generate a variable blood flow, the variable blood flow comprising a constant flow component of a desired blood flow value and a variable flow component having a mean value that is substantially zero, the variable blood flow generating a pressure development in at least the first measurement site, the pressure development being variable over time, comprising a pressure component oscillating about the mean value; A plurality of pressure values ​​for a time period are received from the pressure sensor, the time period comprising a plurality of pressure oscillations about the mean value, the pressure values ​​being measured at consecutive moments in time.

20. The apparatus according to any one of claims 1 to 7, wherein: The signal related to the first measured pressure in the first measurement site comprises a pressure development which can vary over time including a pressure component which oscillates around a mean value.

21. The apparatus of claim 19, wherein: The electronic control unit is configured to correct the average value of the measured pressures by means of the first mathematical correction model.

22. The apparatus of claim 19, wherein: The electronic control unit is configured to determine a pressure drop of an average of the measured pressures between the first measurement location and the first reference location.

23. The apparatus according to any one of claims 1 to 7, wherein: The first mathematical correction model is a function of the blood flow rate in the circuit segment.

24. An extracorporeal blood treatment apparatus comprising: Blood processing device (2); An extracorporeal blood circuit connected to the blood treatment device (2), the extracorporeal blood circuit comprising: a blood extraction line (6) connected to a blood inlet port (3a) of the blood treatment device (2); and a blood return line (7) connected to a blood outlet port (3b) of the blood treatment device (2); a blood pump (8), the pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump (8); a treatment fluid circuit (12) operatively connected to the extracorporeal blood circuit and / or the blood treatment device (2); a first pressure sensor (24) located at a first measuring position on the blood extraction line (6) upstream of the blood treatment device (2); a second pressure sensor (25) located at a second measuring position on the blood return line (7) downstream of the blood treatment device (2); an auxiliary pressure sensor located at an auxiliary measurement location in the process fluid loop; an electronic control unit (23) operatively connected to at least the auxiliary pressure sensor; Wherein, the electronic control unit (23) is configured to perform at least the following processes: - receiving a signal from the auxiliary pressure sensor related to the measured auxiliary pressure in the auxiliary measurement location; -Correcting the measured auxiliary pressure by an auxiliary mathematical correction model to obtain an actual auxiliary pressure in an auxiliary reference position different from the auxiliary measurement position, wherein the auxiliary reference position is located in the processing fluid circuit; wherein an auxiliary circuit section is positioned between the auxiliary reference position and the auxiliary measurement position; wherein the auxiliary mathematical correction model is a model of the auxiliary pressure drop in the auxiliary circuit section.

25. The apparatus of claim 24, wherein the electronic control unit is configured to: One or both of the following: ■ Receive from the first pressure sensor (24) the first measured blood pressure P1 at the first measuring site 测量值 Related signals; ■ Correct the first measured blood pressure P1 by using the first mathematical correction model 测量值 , to obtain a first actual blood pressure P at a reference site located at the blood inlet port (3a) of the blood treatment device (2) 入口 , the first reference location is different from the first measurement location, wherein a circuit segment is located between the first reference location and the first measurement location; wherein the first mathematical correction model is a model of the pressure drop in the circuit segment; and / or ■ receiving a second measured blood pressure P2 downstream of the blood treatment device (2) from the second pressure sensor (25) located at the second measurement site 测量值 Related signals; ■ Correct the second measured blood pressure P2 by using the second mathematical correction model 测量值 , to obtain the second actual blood pressure P at the second reference site 出口 , the second reference site is located at the blood outlet port (3b) of the blood treatment device (2) instead of the second measurement site, wherein a second circuit section is located between the second reference site and the second measurement site; wherein the second mathematical correction model is a model of the pressure drop in the second circuit section; as well as ○ determining an auxiliary pressure drop between the auxiliary measurement location and the auxiliary reference location; o The transmembrane pressure of the blood treatment device is calculated based on one or both of the following: - a first actual blood pressure in said first reference site, and: ○The actual auxiliary pressure, or o the first measured blood pressure in the auxiliary reference site, and a determined pressure drop between the auxiliary measurement site and the auxiliary reference site; or - a second actual blood pressure in said second reference site, and: o The first measured blood pressure in the auxiliary measurement site, and the determined pressure drop between the auxiliary measurement site and the auxiliary reference site.

26. A method for monitoring the pressure in an extracorporeal blood treatment apparatus, wherein: The extracorporeal blood treatment device comprises: Blood processing device (2); An extracorporeal blood circuit connected to the blood treatment device (2), the extracorporeal blood circuit comprising: a blood extraction line (6) connected to a blood inlet port (3a) of the blood treatment device (2); and a blood return line (7) connected to a blood outlet port (3b) of the blood treatment device (2); a blood pump (8), the pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump (8); a first pressure sensor (24) located on the blood extraction pipeline (6) upstream of the blood treatment device (2); a second pressure sensor (25) located on the blood return line (7) downstream of the blood treatment device (2); The method comprises: - receiving from the first pressure sensor (24) a first measured blood pressure P1 in the first measurement site 测量值 Related signals; - Correcting the first measured blood pressure P1 by a first mathematical correction model 测量值 , to obtain a first actual blood pressure P in a first reference site different from the first measurement site 入口 , the first reference site is at the blood inlet port (3a) of the blood treatment device (2); wherein a circuit segment is positioned between the first reference site and the first measurement site; wherein the first mathematical correction model is a model of the pressure drop in the circuit segment.

27. The method of claim 26, wherein the method comprises: - receiving a second measured blood pressure P2 downstream of the blood treatment device (2) from the second pressure sensor (25) located at the second measurement site 测量值 Related signals; - Correcting the second measured blood pressure P2 by a second mathematical correction model 测量值 , to obtain the second actual blood pressure P at the second reference site 出口 , the second reference site is at the blood outlet port (3b) of the blood treatment device (2) rather than at the second measurement site, wherein a second circuit section is positioned between the second reference site and the second measurement site; wherein the second mathematical correction model is a model of the pressure drop in the second circuit section.

28. The method according to claim 27, wherein: The first mathematical correction model is built from physical equations and is a function of the geometry of the loop segment.

29. The method according to claim 27, wherein: The first mathematical correction model is a function of blood kinematic viscosity or blood dynamic viscosity.

30. The method according to any one of claims 27 to 29, wherein: The first mathematical correction model is a function of blood flow rate and blood hematocrit, and is a function of blood temperature and / or blood protein concentration.

31. The method according to any one of claims 27 to 29, wherein: The first mathematical correction model is an experimental model of a measurement error derived from a plurality of experimental data sets, the measurement error being a difference between a measured blood pressure in the first measurement site and a first actual blood pressure in the first reference site.

32. The method according to any one of claims 27 to 29, wherein: The first mathematical correction model is derived from a regression analysis of the measurement errors collected through the multiple experimental data sets relative to one or more parameters collected through the multiple experimental data sets, wherein the parameters include a first measured blood pressure and at least one other operating parameter of the extracorporeal blood treatment device (1); wherein the at least one other operating parameter includes a blood flow rate.

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