Fluid warming device for an extracorporeal blood treatment device and method for detecting fluid temperature at the outlet of a fluid warming device for an extracorporeal blood treatment device - Patents.com

Abstract

The fluid warming device for an extracorporeal blood treatment device includes an outlet temperature sensor (31) operatively operating at an outlet (22) of a fluid warming path (23) to detect a measured outlet temperature (To) of a fluid exiting the fluid warming device (18), and an electronic control unit (29) operatively connected to the outlet temperature sensor (31). The electronic control unit (29) is configured to receive a signal from the outlet temperature sensor (31) correlating to the measured outlet temperature (To), correct the measured outlet temperature (To) via a correction model to obtain an actual fluid outlet temperature (Tout), and adjust the heating power (Ph) of a heating element to maintain the actual fluid outlet temperature (Tout) at a set reference temperature value (Tset). The correction model is an empirical model of a measurement error (E) derived from multiple experimental data sets, the measurement error (E) being the difference between the measured outlet temperature (To) and the actual fluid outlet temperature (Tout).

Description

[Technical field]

[0001] The present invention relates to a fluid warming device for an extracorporeal blood treatment device and to an extracorporeal blood treatment device comprising or adapted to be coupled to a fluid warming device.

[0002] The present invention relates to a fluid warming device (blood warming device) that is connected or configured to be connected to the extracorporeal blood circuit of an extracorporeal blood treatment device to heat blood and / or a fluid warming device (process fluid warming device) that is connected or configured to be connected to the process fluid circuit of an extracorporeal blood treatment device to heat process fluid.

[0003] The present invention relates to a method for detecting the temperature of a fluid at the outlet of a fluid warming device.

[0004] In particular, the present invention relates to the correction of temperature measurements provided by contact temperature sensors, such as thermistors or thermocouples, at the outlet of a fluid warming device. [Background technology]

[0005] Extracorporeal blood processing involves removing blood from a patient, processing the blood outside the patient, and returning the processed blood to the patient. Extracorporeal blood processing is typically used to extract undesirable substances or molecules from a patient's blood and add desirable substances or molecules to the blood. Extracorporeal blood processing is used in 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 processing, for example, to add or remove substances from the blood, to maintain acid / base balance, or to remove excess fluid, or to perform an extracorporeal gas exchange process.

[0006] Extracorporeal blood processing is typically accomplished by removing blood from a patient, for example in a continuous flow, and introducing the blood into a primary chamber, also called a blood chamber, of a processing unit (such as a dialyzer or blood filter) that allows the blood to flow through a semipermeable membrane that selectively allows substances in the blood to cross the membrane from the primary chamber to a secondary chamber and also selectively allows substances in the secondary chamber to cross the membrane into the blood in the primary chamber, depending on the type of processing.

[0007] During extracorporeal blood treatment, the patient may lose a significant amount of heat due to fluid exchange by diffusion or convection, and due to heat lost to the atmosphere. Since extracorporeal blood treatment can last from several hours to several days, the patient is at risk of hypothermia if precautions are not taken. This risk exists both in the case of relatively short treatments with large volume exchanges, for example in chronic hemodialysis (HD), and in the case of continuous treatments with small volumes, such as continuous renal replacement therapy (CRRT). Moreover, the risk of hypothermia is even more problematic in the case of treatments applied to low-weight patients, such as children. Blood cooling by fluid exchange (dialysate, infusate, or both) or by water evaporation during the gas exchange process is usually more important than heat loss to the atmosphere in a complete extracorporeal blood circuit.

[0008] To prevent hypothermia during extracorporeal blood processing, blood warmers have been used which act on the blood line and can warm the blood directly, and process fluid warmers which act on the process fluid circuit to heat the process fluid before injection into the blood circuit or processing unit.

[0009] Measurement of blood / fluid temperature at the outlet of a blood / fluid warmer is known and is used to control the blood / fluid warming device to regulate the temperature of the processed blood returning to the patient and to drive the patient's temperature over the long term.

[0010] US Patent 6,535,689 relates to an intravenous fluid warming system with a removable heat exchanger. The system includes a warming unit for warming the fluid and an inlet slot for receiving the heat exchanger embodied as a cassette. The outlet temperature of the warmed fluid at the outlet port is monitored by a temperature sensor located near the fluid outlet port. The fluid outlet port can have an infrared thermometer, an integral heat sensor, or a thermocouple for sensing the fluid temperature.

[0011] A drawback of most of the known solutions relates to the lack of accuracy of the temperature measurement at the outlet of the blood / fluid warmer, especially measurements made via contact temperature sensors such as thermistors and thermocouples.

[0012] These types of temperature sensors are required to be in physical contact with the object being sensed and use conduction to monitor changes in temperature. In blood / fluid warmers, these types of temperature sensors are placed in contact with the bag, cassette, or tube through which the blood / fluid flows. Summary of the Invention

[0013] In view of the above, it is an object of embodiments of the present invention to improve the reliability of a fluid warming device for an extracorporeal blood treatment device, and to improve the reliability of an extracorporeal blood treatment device that uses a fluid warming device.

[0014] An objective of embodiments according to the present invention is to improve control of the temperature of the treated blood returning to the patient and to drive the patient's temperature over the long term.

[0015] In particular, it is an object to provide a fluid warming device which provides improved reliability and accuracy of fluid temperature measurement at the outlet of the fluid warming device.

[0016] A further object is to provide optimized fluid temperature accuracy for a given design of a fluid warming device and / or extracorporeal blood treatment device.

[0017] It is a further object of the present invention to provide a fluid warming device and / or extracorporeal blood treatment device having the above-mentioned improved accuracy, which at the same time is structurally simple, reliable and cost-effective.

[0018] A further object is to provide reliability and accuracy while avoiding the development of complex and tedious insulation of the sensor.

[0019] A further objective is to provide reliability and accuracy without impacting the cost of the device and / or apparatus.

[0020] At least one of the above objectives is substantially achieved by correcting temperature measurements performed by a contact temperature sensor at the outlet of the fluid warming device through an empirical model of measurement error derived from other available parameters.

[0021] In particular, at least one of the above objects is substantially achieved by a fluid warming device and a method for detecting a fluid temperature at an outlet of the fluid warming device according to one or more of the appended claims.

[0022] Aspects of the present invention are disclosed below.

[0023] According to a first independent aspect, a fluid warming device for an extracorporeal blood treatment device comprises: a casing defining a heating zone that contains or is configured to contain a fluid warming pathway having an inlet and an outlet that is connected or connectable to an extracorporeal blood treatment device; a heating element operatively operating within the heating zone to heat the fluid warming pathway; at least one site temperature sensor operatively operating on a site along the fluid warming pathway to detect a measured temperature of fluid within the fluid warming device, optionally the at least one site temperature sensor being an outlet temperature sensor operatively operating at an outlet of the fluid warming pathway to detect a measured outlet temperature of fluid exiting the fluid warming device; an electronic control unit operatively connected to at least the in-situ temperature sensor; The electronic control unit includes: receiving a signal from the site temperature sensor that correlates to the measured site temperature; - correcting the measured site temperature with a correction model to obtain an actual fluid site temperature. The method is configured to perform at least the steps of: The correction model is a mathematical model of a measurement error, the measurement error being the difference between the measured site temperature and the actual fluid site temperature.

[0024] In particular, the correction model is an empirical model of the measurement errors derived from multiple experimental data sets.

[0025] Optionally, said site temperature sensor is an inlet temperature sensor or an outlet temperature sensor, or a temperature sensor located between the inlet and the outlet.

[0026] Optionally, said electronic control unit is configured to adjust the heating power of said heating element to maintain said actual fluid site temperature at a set reference temperature value.

[0027] Optionally, said electronic control unit is configured to adjust the heating power of a heating element to maintain said actual fluid outlet temperature at a set reference temperature value.

[0028] Optionally, said site temperature sensor is other than said outlet temperature sensor, and said electronic control unit further comprises: Deriving an actual fluid outlet temperature from the actual fluid site temperature; adjusting the heating power of the heating element in order to maintain the actual fluid outlet temperature at a set reference temperature value; It is configured to execute the procedure:

[0029] According to a second independent aspect, an extracorporeal blood treatment device includes: A blood processing device; an extracorporeal blood circuit connected to the blood processing device; a blood pump, the pump portion of the extracorporeal blood circuit being configured to be coupled to the blood pump; Optionally, a processing fluid circuit operably connected to said extracorporeal blood circuit and / or said blood processing device; at least one fluid warming device coupled or configured to be coupled to the extracorporeal blood circuit for heating blood and / or to the process fluid circuit for heating process fluid, The fluid warming device is according to the first aspect and / or includes one or more of the following aspects.

[0030] According to a third independent aspect, a method is disclosed for detecting a fluid temperature at a site of a fluid warming device for an extracorporeal blood treatment device, optionally at an outlet of the fluid warming device for the extracorporeal blood treatment device, comprising: The fluid warming device includes: a casing defining a heating zone that contains or is configured to contain a fluid warming pathway having an inlet and an outlet that is connected or connectable to an extracorporeal blood treatment device; a heating element operatively operating within the heating zone to heat the fluid warming pathway; at least one site temperature sensor operatively operating on a site along the fluid warming pathway to detect a measured temperature of fluid within the fluid warming device, optionally the at least one site temperature sensor being an outlet temperature sensor operatively operating at an outlet of the fluid warming pathway to detect a measured outlet temperature of fluid exiting the fluid warming device; The method is optionally performed by a control unit of the fluid warming device; - constructing a correction model function of a measurement error or a correction model as a mathematical model of the measurement error, in particular an empirical model of the measurement error derived from a plurality of experimental data sets, the measurement error being the difference between the measured site temperature and an actual fluid site temperature; - correcting the measured site temperature through the correction model to obtain the actual fluid site temperature; Includes.

[0031] In a fourth aspect according to the first, second or third aspect, the fluid warming device is a blood warming device and is connected or configured to be connected to the extracorporeal blood circuit, optionally to a blood return line of the extracorporeal blood circuit, for heating blood.

[0032] In a fifth aspect according to the first, second or third aspects, the fluid warming device is a process fluid warming device and is coupled or configured to be coupled to the process fluid circuit for heating a process fluid. Optionally, the blood processing device includes a blood chamber and a fluid chamber separated from each other by a semi-permeable membrane. Optionally, the process fluid circuit includes the fluid chamber, a dialysis line connected to the fluid chamber, and optionally a fluid drain line connected to the fluid chamber. Optionally, the process fluid circuit comprises an infusion circuit including one or more infusion lines for a substitution fluid.

[0033] In a sixth aspect according to any of the preceding aspects, the correction model is derived from a regression analysis of the measurement error against a plurality of parameters, in particular collected across the plurality of experimental data sets, the plurality of parameters optionally being collected across the plurality of experimental data sets.

[0034] In a seventh aspect according to the previous aspects, the parameters include the measured site temperature, optionally a measured outlet temperature, and at least one further operating parameter (working parameter) of the fluid warming device.

[0035] In an eighth aspect according to the sixth or seventh aspect, the parameters include the measured site temperature, optionally a measured outlet temperature, and at least one further operating parameter of the extracorporeal blood treatment device.

[0036] In a ninth aspect according to the previous aspects, the at least one further operating parameter is a temperature of a heating element of the fluid warming device.

[0037] In a tenth aspect according to the eighth or ninth aspect above, the at least one further operating parameter is a heating power (heating power, heating output) of the fluid warming device.

[0038] In an eleventh aspect according to any of the eighth to tenth aspects above, the at least one further operating parameter is a measured inlet temperature of the fluid entering the fluid warming device.

[0039] In a twelfth aspect according to any of the eighth to eleventh aspects above, the at least one further operating parameter is at least one measured compensation temperature, optionally the compensation temperature may be a temperature of a part of the fluid warming device and / or an ambient temperature. Optionally, the compensation ambient temperature may result from an operator input or may be measured via another device of the blood processing device or another independent device.

[0040] In a thirteenth aspect according to any of the eighth to twelfth aspects previously described, the at least one further operating parameter is a fluid flow rate.

[0041] In a 14th aspect according to any of the aforementioned 8th to 13th aspects, the at least one further operating parameter is a ratio between the heating power of the fluid warming device and the difference between the measured outlet temperature and the measured inlet temperature.

[0042] Optionally, the at least one further operating parameter is a power supply voltage of the fluid warming device.

[0043] In a fifteenth aspect according to any of the preceding aspects, the plurality of experimental data sets substantially covers an entire intended operating range of the fluid warming device. Optionally, the plurality of experimental data sets are obtained via a plurality of different bags or cassettes, and / or different control units.

[0044] In a sixteenth aspect according to the preceding aspect, the intended total operating range is: an operating range of the actual fluid site temperature; an operating range for said measured site temperature; Fluid flow rate operating range, Operating range of the heating element temperature, Operating range of heating power, Operating range of actual or measured inlet temperature, an operating range of at least one measured compensated temperature; Ambient temperature operating range, Power supply voltage operating range, is defined by at least one of the following: In a seventeenth aspect according to any of the previous aspects, the number of said experimental data sets is greater than 30, optionally greater than 50.

[0045] In an 18th aspect according to any of the preceding aspects, the fluid warming device includes an inlet temperature sensor operatively operating at the inlet of the fluid warming path to detect a measured inlet temperature of the fluid entering the fluid warming device.

[0046] In a nineteenth aspect according to the previous aspect, the electronic control unit is configured to at least execute the procedure of receiving, from the inlet temperature sensor, a signal correlating to the measured inlet temperature.

[0047] In a twentieth aspect according to any of the preceding aspects, the fluid warming device includes at least one heating element temperature sensor coupled to one or more heating elements of the fluid warming device for detecting a measured temperature of the one or more heating elements.

[0048] In a twenty-first aspect according to the previous aspect, the electronic control unit is configured to at least execute the procedure of receiving, from the heating element temperature sensor, a signal correlating to the measured temperature of the heating element.

[0049] In a 22nd aspect according to any of the preceding aspects, the fluid warming device includes at least one compensation temperature sensor positioned between the site temperature sensor and one or more heating elements to detect a measured temperature of a portion of the fluid warming device.

[0050] In a 23rd aspect according to the previous aspect, the electronic control unit is configured to at least perform the procedure of receiving a signal from the compensation temperature sensor that correlates to the measured temperature of the portion of the fluid warming device.

[0051] In a twenty-fourth aspect according to any of the preceding aspects, the electronic control unit is configured to at least execute the steps of receiving a signal correlating to a heating power of the fluid warming device.

[0052] In a twenty-fifth aspect according to any of the preceding aspects, the electronic control unit is configured to at least execute the steps of receiving a signal correlated to a fluid flow rate.

[0053] In a 26th aspect according to at least one of the aforementioned 19th, 21st, 23rd to 25th aspects, the electronic control unit is configured to at least perform a procedure for calculating the actual fluid site temperature from the measured site temperature and from at least one of the measured inlet temperature, the measured temperature of the heating element, the measured temperature of the part of the fluid warming device, the heating power, and the fluid flow rate.

[0054] In a twenty-seventh aspect according to the preceding aspect, the calculation is performed through the correction model.

[0055] In a twenty-eighth aspect according to any of the previous aspects, the site temperature sensors are of the contact type.

[0056] In a twenty-ninth aspect according to the previous aspects, the site temperature sensor is a thermistor or a thermocouple.

[0057] In a thirtieth aspect according to either the twenty-eighth or twenty-ninth aspects above, the contact site temperature sensor is configured to be in contact or to be placed in contact with a site of the fluid heating pathway.

[0058] In a thirty-first aspect according to the previous aspects, the fluid heating pathway comprises a channel and / or a chamber defined by a wall.

[0059] In a thirty-second aspect according to the previous aspects, the wall is of a soft or hard material.

[0060] In a thirty-third aspect according to the thirty-first or thirty-second aspect, the wall material is plastic.

[0061] In a thirty-fourth aspect according to the thirty-first or thirty-second aspect above, the contact site body temperature sensor is configured to be in contact or to be placed in contact with at least one of the walls.

[0062] In a thirty-fifth aspect according to any of the preceding aspects, the fluid warming pathway comprises a bag, optionally a flexible bag, or a cassette, the fluid warming bag or cassette defining the fluid warming pathway and presenting the inlet and the outlet.

[0063] In a thirty-sixth aspect according to any of the preceding aspects, the bag includes two plastic sheets (e.g., polyurethane or polyvinyl chloride) overlapped and welded to define the fluid heating pathway within the bag.

[0064] In a thirty-seventh aspect according to the thirty-fifth or thirty-sixth aspect above, the casing defines a heating sheet configured to house the bag or cassette.

[0065] In a thirty-eighth aspect according to the previous aspects, the heating element includes at least one heating plate, and optionally two opposing heating plates defining the heating sheet, for heating the fluid warming bag or cassette.

[0066] In a 39th aspect according to any of the aforementioned 35th to 38th aspects, the outlet temperature sensor is configured to be mounted within the casing and in contact or positioned to be in contact with the outlet of the fluid warming bag or cassette.

[0067] In a 40th aspect according to any of the aforementioned 35th to 39th aspects, the inlet temperature sensor is configured to be mounted within the casing and to be in contact or positioned to be in contact with the inlet of the fluid warming bag or cassette.

[0068] The term "in contact" according to the specification and claims means that the contact site / outlet / inlet temperature sensor abuts the site / outlet / inlet of the fluid heating pathway or abuts a heat transfer element such as a metal platelet, which abuts the site / outlet / inlet of the fluid heating pathway. In either case, the contact site / outlet / inlet temperature sensor measures its own temperature once it has reached thermal equilibrium with the fluid heating pathway.

[0069] In a forty-first aspect according to the thirty-eighth aspect above, a heater plate temperature sensor, optionally a plurality of heater plate temperature sensors, is coupled to the one or more heater plates.

[0070] In a forty-second aspect according to the preceding aspects, the heating plate temperature sensor is disposed along the fluid heating path.

[0071] In a forty-third aspect according to the twenty-second or twenty-third aspect described above, the at least one compensation temperature sensor comprises a compensation temperature sensor for sensing the temperature of the casing.

[0072] In a 44th aspect according to the aforementioned 22nd or 23rd aspect, the at least one compensation temperature sensor comprises a compensation temperature sensor positioned at or near a printed circuit board assembly operably connected to the outlet temperature sensor.

[0073] In a forty-fifth aspect according to any of the previous aspects, the casing comprises a holder, optionally a plastic holder, for the outlet temperature sensor.

[0074] In a forty-sixth aspect according to the preceding aspect in the case of the twenty-second or twenty-third aspect, the at least one compensation temperature sensor comprises a holder compensation temperature sensor coupled to the holder of the outlet temperature sensor.

[0075] According to a forty-seventh independent aspect, a method of controlling a fluid warming device for an extracorporeal blood treatment device includes the method of detecting a fluid temperature at a site of the fluid warming device of the third aspect, further comprising: - adjusting the heating power of the heating element to maintain the actual fluid site temperature at a set reference temperature value; Includes.

[0076] In a 48th aspect according to any of the previous aspects, the heating zone includes a plurality of subzones configured to be independently heated.

[0077] In a forty-ninth aspect according to the previous aspects, each subzone includes a respective one or more heating elements.

[0078] In a fiftieth aspect according to the previous aspects, the heating zone includes at least a first subzone at the inlet of the fluid warming bag or cassette and a second subzone at the outlet of the fluid warming bag or cassette.

[0079] In a fifty-first aspect according to the previous aspect, when the site temperature is the outlet temperature, the at least one further operating parameter is a heating power of the second sub-zone of the fluid warming device, where in a multi-zone design the power used in the last heating zone allows for better compensation than the total power.

[0080] In a fifty-second aspect according to the fifty-first aspect, when the site temperature is the inlet temperature, the at least one further operating parameter is a heating power of the first sub-zone of the fluid warming device. [Brief description of the drawings]

[0081] The following figures relating to aspects of the present invention are provided as non-limiting examples. [Figure 1] FIG. 1 shows a schematic diagram of an extracorporeal blood treatment device including a fluid warming device according to the present invention. [Diagram 2]FIG. 2 shows a schematic perspective view of the fluid warming device of FIG. [Diagram 3] FIG. 3 shows the fluid warming device of FIG. 1 in an open configuration. [Figure 4] FIG. 4 is a disposable fluid warming bag for use with the fluid warming device of FIGS. [Diagram 5] FIG. 5 shows an enlarged cross-sectional view of a portion of the fluid warming device of FIG. [Figure 6] FIG. 6 shows an enlarged cross-sectional view of another portion of the fluid warming device of FIG. [Figure 7] FIG. 7 is a flow chart illustrating the steps for constructing a correction model according to the method of the present invention. [Figure 8] FIG. 8 shows a cumulative plot of the results used to construct the correction model. [Figure 9] FIG. 9 is a flow chart illustrating a method of controlling a fluid warming device in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0082] Referring to the accompanying drawings, FIG. 1 shows a schematic diagram of an extracorporeal blood treatment device 1.

[0083] The device 1 comprises a blood processing device 2, for example a blood filter, a blood diafilter (haemodiafilter), a plasma filter, a dialysis filter, an absorber or any other unit suitable for processing blood taken from a patient P.

[0084] The blood processing device 2 has a first compartment or blood chamber 3 and a second compartment or fluid chamber 4 separated from each other by a semi-permeable membrane 5. A blood withdrawal line 6 is connected to the inlet port 3a of the blood chamber 3 and is configured to remove blood from a vascular access device, for example inserted in a fistula of the patient P, in an operative state of connection to the patient P. A blood return line 7 connected to the outlet port 3b of the blood chamber 3 is configured to receive the treated blood from the processing unit 2 and return the treated blood to a further vascular access, for example also connected to a fistula of the patient P. It is noted that various configurations for the vascular access device may be envisaged, for example a typical access device includes a needle or catheter inserted into a vascular access, which may be a fistula, a graft, or a central vein (e.g. jugular vein) or a peripheral vein (femoral vein), etc. The blood withdrawal line 6 and the blood return line 7 are part of the extracorporeal blood circuit of the device 1.

[0085] The extracorporeal blood circuit 6, 7 and the treatment unit 2 are usually disposable components that are mounted onto the frame of a blood treatment machine (not shown).

[0086] As shown in Fig. 1, the device 1 comprises at least a first actuator, in this example a blood pump 8 which is part of the machine and operates on a blood withdrawal line 6, causing the movement of blood taken from the patient P from a first end of the withdrawal line 6 connected to the patient P to the blood chamber 3. The blood pump 8 is for example a peristaltic pump as shown in Fig. 1, acting on a respective pump portion of the withdrawal line 6.

[0087] It should be noted that for purposes of this specification and the appended claims, the terms "upstream" and "downstream" may be used with reference to the relative positions assumed by components belonging to or operating on the extracorporeal blood circuit. These terms should be understood with reference to the direction of blood flow from a first end of the blood withdrawal line 6 connected to the patient P towards the blood chamber 3, and then from the blood chamber 3 towards a second end of the blood return line 7 connected to the patient P's vascular access.

[0088] The apparatus 1 may further comprise an air capture device 9 operating on the blood return line 7 (the air capture device 9 may be a venous degassing chamber). The air capture device 9 is disposed on-line in the blood return line 7.

[0089] A first portion of the blood return line 7 fluidly connects the outlet port 3b of the blood chamber 3 to the air capture device 9, and a second portion of the blood return line 7 fluidly connects the air capture device 9 to the patient P. Blood coming from the blood chamber 3 of the processing apparatus 2 passes through the air capture device 9 before reaching the patient P.

[0090] The device 1 of Fig. 1 further comprises one fluid discharge line 10 connected to the outlet port 4b of the fluid chamber 4 so as to receive the filtered waste liquid through the semipermeable membrane 5. The fluid discharge line 10 receives such filtered waste liquid coming from the fluid chamber 4 of the treatment device 2, including, for example, spent dialysate and / or fluid ultrafiltered through the membrane 5. The fluid exhaust line 10 leads to a receiving element (not shown) having, for example, a collection bag or a drain pipe for the waste liquid. One or more dialysate pumps (not shown) may operate on the fluid discharge line 10.

[0091] 1, there is also a dialysis line 11 for supplying fresh treatment fluid to the inlet port 4a of the fluid chamber 4. The presence of this dialysis line 11 is not strictly necessary, since in its absence the device 1 can still perform treatments such as ultrafiltration, hemofiltration or plasmafiltration. If the dialysis line 11 is present, a fluid flow blocking device (not shown) can be used to selectively allow or prevent the passage of fluid through the dialysis line 11, depending on whether purification by diffusion effects takes place inside the treatment device 2 or not.

[0092] The dialysis line 11, if present, typically includes a dialysis pump and can receive fresh fluid from a module (not shown), e.g., a bag of dialysis fluid or an on-line preparation portion, and deliver such fluid to the inlet port 4a of the fluid chamber 4.

[0093] The fluid exhaust line 10 , the dialysis line 11 and the fluid chamber 4 are part of a treatment fluid circuit 12 .

[0094] The device 1 as shown in Fig. 1 further comprises an infusion circuit comprising one or more infusion lines for a substitution fluid. According to the embodiment of Fig. 1, a pre-infusion line 13 is connected to the blood withdrawal line 6 between the blood pump 8 and the inlet port 3a of the blood chamber 3. A pre-pump infusion line 14 is connected to the blood withdrawal line 6 upstream of the blood pump 8, between said blood pump 8 and a vascular access device inserted in the stoma of the patient P.

[0095] The post-infusion lines 15, 16 are connected to the blood return line 7 to perform the HF or HDF treatment. Usually, one or two post-infusion lines are used upstream of or connected to the air capture device 9. FIG. 1 shows that the post-infusion lines include a first and a second branch 15, 16. Each of the pre-infusion and / or post-infusion lines 13, 14, 15, 16 is provided with a pump (not shown). The pre-infusion and / or post-infusion lines 13, 14, 15, 16 may be fed directly by fluid coming from a bag or by an infusion fluid prepared online. Each of the pre-infusion and / or post-infusion lines 13, 14, 15, 16 is part of the treatment fluid circuit 12. The specific configuration of the pre-infusion and post-infusion circuits may of course differ from the one shown in FIG. 1.

[0096] The blood return line 7 provides, for example, a heating zone located between the first branch 15 and the second branch 16 of the post-infusion line, in which the blood is warmed before entering the blood circulation system of the patient P.

[0097] In the embodiment shown in the accompanying drawings, the heating portion is part of a disposable blood warming bag 17 that is inserted into a blood warming device 18. The blood warming device 18 is connected to or is part of the extracorporeal blood treatment device 1.

[0098] The blood warming bag 17 shown in the accompanying drawings is a substantially flat, flexible bag that is insertable through a slot 19 in a heating sheet 20 provided in a blood warming device 18 (FIGS. 2 and 3).

[0099] The blood warming bag 17 has an inlet 21 and an outlet 22 that are connected to the extracorporeal blood circuit. For example, the blood warming bag 17 includes two plastic sheets (e.g., polyurethane or polyvinyl chloride) that are overlapped and welded to form a bag and to form a fluid warming pathway 23 on the inside of the bag that is defined by the two sheets and a weld line.

[0100] The inlet 21 and outlet 22 are tubing sections disposed at opposite ends of a fluid warming pathway 23. The tubing sections of the inlet 21 and outlet 22 protrude from the sides of the blood warming bag 17 and are substantially parallel to each other.

[0101] Blood warming device 18 includes a casing 24 defining a heating sheet 20 configured to house blood warming bag 17. Casing 24 includes an upper portion 25 and a lower portion 26 that may be linked and moveable between an operational configuration (shown in FIG. 2) and a maintenance configuration (shown in FIG. 3). Upper portion 25 and lower portion 26 in FIGS. 2 and 3 are hinged for movement between the configurations.

[0102] When the casing 24 is in the operative configuration of FIG. 2, the upper and lower portions 25,26 are juxtaposed to define a heating sheet 20 within the casing 24 which opens outwardly through the slot 19.

[0103] When the blood warming bag 17 is inserted into the seat through the slot 19, the inlet 21 and outlet 22 of the blood warming bag 17 are positioned near the slot 19 or protrude from said slot 19, allowing the tubes of the blood collection line 6 and blood return line 7 to be connected to other elements of the extracorporeal blood treatment device 1.

[0104] The upper surface of the lower portion 26 has a hollow portion that defines the lower portion of the heating sheet 20, and is formed to accommodate the blood warming bag 17. The hollow portion is heated by a first heating device (not shown), and has a first heating plate 27 disposed below the first heating plate 27.

[0105] The underside of the upper portion 25 is heated by a second heating device (not shown) and has a second heating plate 28 disposed below said second heating plate 28. The second heating plate 28 defines the upper portion of the heating sheet 20. The first heating plate 27 and the second heating plate 28 are opposed and parallel surfaces that define the heating sheet 20.

[0106] The first and second heating plates 27, 28 define heating elements for the blood warming bag 17. The first and second heating devices may be or may be connected to electrical resistors powered by the power control unit and controlled by the electronic control unit 29 to heat the blood warming pathway 23 in the blood warming bag 17.

[0107] In an embodiment not shown, the heating zone includes multiple sub-zones configured to be heated independently. As an example, each of the first and second heating plates 27, 28 is divided into multiple portions, each of which is heated independently of the other portions.

[0108] Blood warming device 18 includes an inlet temperature sensor 30 and an outlet temperature sensor 31 embedded in a bottom surface 32 of casing 24 near slot 19 (FIG. 3). Inlet temperature sensor 30 is operatively operative at inlet 21 of blood warming pathway 23 to detect a measured inlet temperature of blood entering blood warming device 18. Outlet temperature sensor 31 is operative at outlet 22 of blood warming pathway 23 to detect a measured outlet temperature of blood exiting blood warming device 18.

[0109] The inlet temperature sensor 30 is a temperature sensor integrated circuit (IC) having a contact type temperature sensor, e.g., a thermistor or a thermocouple, housed in a plastic holder 33 (FIG. 5). The plastic holder 33 and the inlet temperature sensor 30 are housed in a sheet formed on the bottom surface 32 of the casing 24. A heat conducting element, such as an aluminum plate 100, is attached to the plastic holder 33. The aluminum plate 100 opens to the bottom surface 32 and is flush with said bottom surface 32. The inlet temperature sensor 30 is disposed inside the plastic holder 33 and abuts against the aluminum plate 100 (FIG. 5).

[0110] When blood warming bag 17 is properly inserted into the sheet, inlet 21 of blood warming bag 17 comes into contact with aluminum plate 100 (FIG. 6). Inlet temperature sensor 30 detects temperature Ti of aluminum plate 100 and inlet 21 through which blood flows.

[0111] The outlet temperature sensor 31 is a temperature sensor integrated circuit (IC) having a contact type temperature sensor, e.g. a thermistor or thermocouple, housed in a plastic holder 34 (FIG. 5). The plastic holder 34 and the outlet temperature sensor 31 are housed in a sheet formed in the bottom surface 32 of the casing 24. The outlet temperature sensors 31 open into the bottom surface 32 and abut against respective aluminum plates 101 that are flush with said bottom surface 32 (FIG. 5).

[0112] When blood warming bag 17 is properly inserted into the sheet, outlet 22 of blood warming bag 17 comes into contact with aluminum plate 101. Outlet temperature sensor 31 detects the temperatures of aluminum plate 101 and outlet 22 through which heated blood flows.

[0113] A holder compensation temperature sensor 35, for example a thermistor, is embedded in the plastic holder 34 of the outlet temperature sensor 31 and measures the temperature Tcomp1 of said plastic holder 34.

[0114] Blood warming device 18 includes an additional compensation temperature sensor 36 , such as a temperature sensor integrated circuit (IC) having a thermistor or thermocouple, disposed within casing 24 for sensing the temperature of casing 24 .

[0115] Alternatively, the ambient temperature Ta may be used as the compensation temperature. The ambient temperature Ta may be measured via a respective sensor in the extracorporeal blood treatment device 1 or via an independent device, and may be manually input into the control unit 29 by the operator.

[0116] A printed circuit board assembly (PCBA) 37 is mounted inside the casing 24 and, together with other printed circuit board assemblies, forms part of the electronic control unit 29 of the blood warming device 18 .

[0117] In the illustrated embodiment, an additional compensation temperature sensor 36, eg, a thermocouple, is positioned at or near the printed circuit board assembly 37 to sense a temperature Tcomp2 of the printed circuit board assembly 37.

[0118] The blood warming device 18 includes a plurality of heating plate temperature sensors 38 coupled to the first and second heating plates 27, 28 for detecting the measured temperatures of the heating plates 27, 28. In the illustrated embodiment, each of the first and second heating plates 27, 28 is provided with three heating plate temperature sensors 38 that are positioned along the fluid warming pathway 23 when the blood warming bag 17 is contained within the heating sheet 20.

[0119] The temperature sensors (inlet temperature sensor 30 , outlet temperature sensor 31 , compensation temperature sensor 35 , further compensation temperature sensor 36 , heating plate temperature sensor 38 ) are operatively connected to the printed circuit board assembly 37 and the electronic control unit 29 .

[0120] The electronic control unit 29 may be part of the blood warming device 18, may be connected to the electronic control unit of the device 1, or may be the electronic control unit of the device 1 itself.

[0121] The electronic control unit 29 may comprise a digital processor (CPU) and memory (or memories), analog circuitry, or a combination thereof, as well as input / output interfaces. Said control unit 29 may be a control unit configured to control the device 1 during the patient's blood treatment via software stored in the control unit 29. In the embodiment of Fig. 1, the electronic control unit 29 is connected to at least the blood pump 8 and to a power control unit (not shown) of the blood warming device 18.

[0122] The electronic control unit 29 is configured to control the actual fluid temperature Tout of the treated blood leaving the blood warming device 18 and returning to the patient P via a thermal controller algorithm. For this purpose, the electronic control unit 29 receives the measured outlet temperature Tout from the outlet temperature sensor 31, performs a correction of said measured outlet temperature Tout according to the steps disclosed below (to improve the accuracy of the measurement and obtain a value very close to the actual blood outlet temperature Tout) and adjusts the heating power Ph of the power controller to keep the actual outlet temperature Tout at a set reference temperature value Tset (set point). The electronic control unit 29 uses a closed loop control to maintain the desired temperature at its outlet.

[0123] To correct the measured outlet temperature To, a correction mathematical model or algorithm is pre-developed and stored in the memory of the electronic control unit 29 or connected to the electronic control unit 29. The correction mathematical model or algorithm can be embedded in the thermal controller algorithm.

[0124] The correction model is an empirical model of the measurement error E derived from multiple experimental data sets collected during development testing. The measurement error E is the difference between the measured outlet temperature To and the actual outlet temperature Tout.

[0125] The empirical correction model is constructed by performing a number of test treatments k. An experimental data set is collected for each test treatment k. Each experimental data set includes a number of measured parameters, including the measured outlet temperature To k and at least one further operating parameter of the blood warming device 18 and / or the extracorporeal blood treatment device 1 for that test treatment k.

[0126] The parameters measured for each test treatment k are: To k the measured outlet temperature (via outlet temperature sensor 31); Ti kthe measured inlet temperature (via inlet temperature sensor 32); T-plate k the measured heater plate temperature (via heater plate temperature sensor 38); Ph k heating power of the fluid warming device (via a signal from the power control unit); Tcomp1 k a measured compensation temperature (via compensation temperature sensor 35); Tcomp2 k a measured further compensation temperature (via a further compensation temperature sensor 36); Q k blood flow rate (via a signal from the blood pump 8 or from a system that controls the blood flow); Tout k Measured actual fluid outlet temperature (measured during the test process via an independent highly accurate sensor); Tin k Measured actual fluid inlet temperature (measured during the test process via an independent highly accurate non-contact sensor); Ta k Ambient temperature; Pw k The power supply voltage for the fluid warming device.

[0127] The blood flow rate Q can be replaced by the ratio Ph / (To-Ti) of the heating power Ph to the difference between the measured outlet temperature To and the measured inlet temperature Ti. In fact, the heating power transferred to the blood can be expressed as Ph=ρ×Cp×Q×(Tout-Tin), where Tin is the actual fluid inlet temperature. This relationship shows that Ph / (To-Ti) should be proportional to the actual fluid flow rate.

[0128] The measured compensation temperature and the measured further compensation temperatures Tcomp1, Tcomp2 may be used in combination with or instead of the measured heater plate temperature Tplate.

[0129] The correction model is based on the measurement error E k A model can be derived from a regression analysis of the aforementioned parameters collected over multiple experimental data sets versus the above-mentioned parameters. The model is reliable because the collection of experimental data sets is large, covers the entire intended operating range of the blood warming device 18, and is constructed using several fluid warming devices 18 and several warming bags / cassettes 17.

[0130] The number of experimental data sets k may be 30 or more. The complete intended operating range may be defined by the ranges of the above-mentioned parameters (ΔTo, ΔTi, ΔTplate, ΔPh, ΔTcomp1, ΔTcomp2, ΔQ, ΔTout, ΔTa, ΔPw). Several general regression models may be used according to the operating range of the blood warming device 18.

[0131] The empirical model may include linear and quadratic terms for each of the parameters and / or cross terms and / or other combinations of terms.

[0132] Once the empirical correction model is prepared and stored in the memory of the electronic control unit 29, the electronic control unit 29 is configured to perform the following steps during an extracorporeal blood treatment session performed on the patient P via the device 1: receive a signal from the outlet temperature sensor 31 that correlates to the measured outlet temperature To, and correct the measured outlet temperature To via the correction model to obtain an actual fluid outlet temperature Tout.

[0133] In addition to the measured outlet temperature To, the electronic control unit 29 receives as input at least one of the following measured parameters: To measured outlet temperature (via outlet temperature sensor 31); Ti measured inlet temperature (via inlet temperature sensor 32); Tplate the measured heater plate temperature (via heater plate temperature sensor 38); Ph Fluid warming device heating power (via a signal from the power control unit); Tcomp1 measured compensation temperature (via compensation temperature sensor 35); Tcomp2 the measured further compensation temperature (via the further compensation temperature sensor 36); Q blood flow rate (transmitted via a signal from the blood pump 8 or from a system controlling the blood flow); Ta is the ambient temperature; Pw Power supply voltage.

[0134] Therefore, the actual fluid outlet temperature Tout is calculated from the measured outlet temperature and at least one of To, Ti, Tplate, Ph, Tcomp1, Tcomp2, Q, Ta, and Pw via a correction model / algorithm acting as a transfer function.

[0135] Empirical Modeling Example An empirical model / algorithm was developed based on empirical data collected during development testing. The test setup consisted of a simulated patient (warm water reservoir), an extracorporeal CRRT device, and a blood warming device. The outlet of the blood warming device was equipped with independent temperature sensors at the inlet and outlet to read the actual fluid temperature at those points.

[0136] The outlet measurement error E was defined as the measured outlet temperature To minus the actual fluid temperature at the outlet Tout. In the form of a formula: E=To-Tout.

[0137] Three metrics were used to compare with the outlet error E. Each metric was the difference between a particular secondary sensor and the measured outlet temperature.

[0138] In the form of an expression: DTcomp1=To-Tcomp1 DTcomp2=To-Tcomp2 DTplate=To-Tplate where Tcomp1, Tcomp2 and Tplate are the measured temperatures at the outlet temperature sensor 31, the further compensation temperature sensor 36 and the heater plate temperature sensor 38 of the first heater plate 27 closest to the outlet temperature sensor 31, respectively.

[0139] To see if there was a correlation between the outlet error and any of these metrics, data was collected from a number of test treatments. The treatments were performed using a warm water bath connected to a filter set in a blood treatment device 1 fitted with a blood warming device 18. To calculate each metric once per measurement, the metrics were averaged over the period when the blood warming device 18 was in steady state. In other words, each treatment had an average steady state outlet error DTcomp1, DTcomp2 and DTplate. A flow chart for DTplate is shown in FIG. 7 and a cumulative plot of the results for DTplate is shown in FIG.

[0140] This plot shows a strong linear correlation between the exit error and the DTplate. From this correlation, a correction equation can be derived: E = -a × DTplate-b To-Tout=-a×(To-Tplate)-b Tout = a × (To-Tplate) + b-To where Tout is the estimated fluid temperature at the outlet.

[0141] Closed Loop Compensation Example This equation has been implemented in electronic control unit 29 with constants a and b shown in the last block of Figure 7. This implementation is shown in block diagram form in Figure 9, where the exit correction is part of a feedback loop within electronic control unit 29.

[0142] The warming device 18 according to the invention disclosed herein may also be designed or configured to be coupled to a process fluid circuit to heat the process fluid.

[0143] Instead of or in combination with a blood warming device, one or more process fluid warming devices 18 may be connected to one or more of the pre-infusion and / or post-infusion lines 13, 14, 15, 16 or the dialysis line 11.

[0144] In these embodiments, the blood is warmed by the treatment fluid.

[0145] The correction model described above may be applied to one or more temperature sensors other than the outlet temperature sensor, for example, at a general site of the flow path within the fluid warming device 18. The correction model may be applied to the measured inlet temperature to calculate an actual fluid inlet temperature Tin, which may be used, for example, to perform internal consistency checks, faults, diagnostics, etc. of the fluid warming device.

[0146] While the present 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 to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. 1. A fluid warming device for an extracorporeal blood treatment device, comprising: a casing (24) defining a heating zone and a heating sheet (20) configured to house a fluid warming bag or cassette (17) defining a fluid warming pathway (23) having an inlet (21) and an outlet (22) connected or connectable to an extracorporeal blood treatment device (1); a heating element operatively operating within said heating zone for heating said fluid warming pathway (23), said heating element comprising two opposing heating plates (27, 28) defining said heating sheet (20) for heating said fluid warming bag or cassette (17); and said fluid warming device (18) comprising a plurality of heating element temperature sensors (38) coupled to said two opposing heating plates (27, 28) and disposed along said fluid warming pathway (23) for detecting measured temperatures of said two opposing heating plates (27, 28); at least one outlet temperature sensor (31) operatively operative at the outlet (22) of the fluid warming path (23) to communicate a measured outlet temperature (T) of fluid exiting the fluid warming device (18); an electronic control unit (29) operatively connected to at least said outlet temperature sensor (31); The electronic control unit (29) - receiving from said outlet temperature sensor (31) a signal correlating to said measured outlet temperature (To); - correcting the measured outlet temperature (T) through a correction model to obtain the actual fluid outlet temperature (T); - Adjusting the heating power (Ph) of the heating element in order to keep the actual fluid outlet temperature (Tout) at a set reference temperature (Tset) configured to perform at least the steps: A fluid warming device, wherein the correction model is a mathematical model of a measurement error, the measurement error (E) being the difference between the measured outlet temperature (To) and the actual fluid outlet temperature (Tout).

2. The fluid warming device of claim 1 , wherein the mathematical model of the measurement error is an empirical model of the measurement error (E) derived from multiple experimental data sets.

3. 2. The fluid warming device of claim 1, wherein the correction model is derived from a regression analysis of the measurement error (E) collected across multiple experimental data sets against multiple parameters collected across multiple experimental data sets, the multiple parameters including the measured outlet temperature (To) and at least one further operating parameter of the fluid warming device (18) and / or the extracorporeal blood treatment device (1).

4. 4. The fluid warming device of claim 3, wherein the at least one further operating parameter is selected from the group consisting of: a temperature (Tplate) of a heating element of the fluid warming device, a heating power (Ph) of the fluid warming device, a measured inlet temperature (Ti) of the fluid entering the fluid warming device, a measured compensation temperature (Tcomp1, Tcomp2), an ambient temperature (Ta), a power supply (Pw), a fluid flow rate (Q), and a ratio (P / (To-Ti)) of the heating power (Ph) of the fluid warming device to the difference between the measured outlet temperature (To) and the measured inlet temperature (Ti).

5. the plurality of experimental data sets substantially covering the entire intended operating range of the fluid warming device (18); The intended total operating range is: Actual fluid site temperature operating range, the operating range of the measured fluid site temperature; Fluid flow rate operating range, Operating range of the heating element temperature, Operating range of heating power, Operating range of actual or measured inlet temperature, an operating range of at least one measured compensated temperature; Ambient temperature operating range, Power supply voltage operating range, 5. The fluid warming device according to claim 2, wherein the fluid warming device is defined by at least one of the following:

6. 1. A fluid warming device for an extracorporeal blood treatment device, comprising: a casing (24) defining a heating zone that houses or is configured to house a fluid warming pathway (23) having an inlet (21) and an outlet (22) that is connected or connectable to an extracorporeal blood treatment device (1); a heating element operatively operating within said heating zone to heat said fluid warming pathway (23); at least one outlet temperature sensor (31) operatively operative at the outlet (22) of the fluid warming path (23) to communicate a measured outlet temperature (T) of fluid exiting the fluid warming device (18); an electronic control unit (29) operatively connected to at least said outlet temperature sensor (31); The electronic control unit (29) - receiving from said outlet temperature sensor (31) a signal correlating to said measured outlet temperature (To); - correcting the measured outlet temperature (T) through a correction model to obtain the actual fluid outlet temperature (T); - Adjusting the heating power (Ph) of the heating element in order to keep the actual fluid outlet temperature (Tout) at a set reference temperature (Tset) configured to perform at least the steps: the correction model is a mathematical model of a measurement error, the measurement error (E) being the difference between the measured outlet temperature (T) and the actual fluid outlet temperature (T); The fluid warming device (18) comprises: an inlet temperature sensor (30) operatively operating at the inlet (21) of the fluid warming pathway (23) to detect the measured inlet temperature (Ti) of the fluid entering the fluid warming device (18); at least one heating element temperature sensor (38) coupled to one of the heating elements of the fluid warming device (18) for detecting a measured temperature (Tplate) of the heating element; a compensation temperature sensor (35, 36) disposed between the outlet temperature sensor (31) and the one of the heating elements, for detecting a measured temperature of a portion of the fluid warming device (18); The procedure includes: - receiving a signal from said inlet temperature sensor (31) that correlates to said measured inlet temperature (Ti); - receiving a signal from the heating element temperature sensor (38) that correlates to the measured temperature of the heating element (Tplate); - receiving a signal from the compensation temperature sensor (35, 36) that correlates to the measured temperature (Tcomp1, Tcomp2) of the part of the fluid warming device (18); - receiving a signal correlating to the heating power (Ph) of said fluid warming device (18); - receiving a signal correlating to a fluid flow rate (Q); - calculating the actual fluid outlet temperature (Tout) from the measured outlet temperature (T) and one or more of the measured inlet temperature (Ti), the measured temperature of the heating element (Tplate), the measured temperature of the part of the fluid warming device (18), the heating power (Ph), the fluid flow rate (Q) through the correction model; The fluid warming device further comprising:

7. 1. A fluid warming device for an extracorporeal blood treatment device, comprising: a casing (24) defining a heating zone that houses or is configured to house a fluid warming pathway (23) having an inlet (21) and an outlet (22) that is connected or connectable to an extracorporeal blood treatment device (1); a heating element operatively operating within said heating zone to heat said fluid warming pathway (23); at least one outlet temperature sensor (31) operatively operative at the outlet (22) of the fluid warming path (23) to communicate a measured outlet temperature (T) of fluid exiting the fluid warming device (18); at least one heating element temperature sensor (38) coupled to said one of said heating elements of said fluid warming device (18) for detecting a measured temperature of said one of said heating elements; an electronic control unit (29) operatively connected to at least said outlet temperature sensor (31); The electronic control unit (29) - receiving from said outlet temperature sensor (31) a signal correlating to said measured outlet temperature (To); - receiving a signal from the heating element temperature sensor (38) that correlates to the measured outlet temperature of the heating element; - correcting the measured outlet temperature (T) through a correction model to obtain the actual fluid outlet temperature (T); - Adjusting the heating power (Ph) of the heating element in order to keep the actual fluid outlet temperature (Tout) at a set reference temperature (Tset) configured to perform at least the steps: The electronic control unit (29) calculates a correction formula: [0010] and configured to obtain the actual fluid outlet temperature (Tout) at Tout is the actual fluid outlet temperature; T is the measured outlet temperature; Tplate is the measured temperature of the heating element; A fluid warming device, where a and b are constants.

8. 8. A fluid warming device according to claim 1, wherein the fluid warming device is a blood warming device connected to a blood return line of an extracorporeal blood circuit for heating blood.

9. 9. The fluid heating device according to claim 1, wherein the casing is provided with a holder for the outlet temperature sensor, which is a contact type that is arranged in contact with the outlet (22) of the fluid heating path (23), the holder (34) and the outlet temperature sensor (31) are housed in a sheet formed on the bottom surface (32) of the casing (24), the outlet temperature sensor (31) abuts with each heat conduction element that opens into the bottom surface (32) and is flush with the bottom surface (32), and detects the temperature of each heat conduction element and the outlet (22) through which the heated fluid flows.

10. the casing (24) defines a heating sheet (20) configured to house a fluid warming bag or cassette (17) defining the fluid warming pathway (23) and having the inlet (21) and the outlet (22); the heating element comprises two opposing heating plates (27, 28) defining the heating sheet (20) for heating the fluid warming bag or cassette (17); The fluid warming device (18) of claim 6 or 7, further comprising a plurality of heating element temperature sensors (38) coupled to the two opposing heating plates (27, 28) and arranged along the fluid heating path (23) for detecting measured temperatures of the two opposing heating plates (27, 28).

11. The fluid warming device of claim 10, wherein the outlet temperature sensor (31) is mounted within the casing (24) so ​​as to be positioned in contact with the outlet (22) of the fluid warming bag or cassette (17), an inlet temperature sensor (30) is mounted within the casing (24) so ​​as to be positioned in contact with the inlet (21) of the fluid warming bag or cassette (17), and a compensation temperature sensor (35) is connected to a holder (34) of the outlet temperature sensor (31).

12. 1. A fluid warming device for an extracorporeal blood treatment device, comprising: a casing (24) defining a heating zone that houses or is configured to house a fluid warming pathway (23) having an inlet (21) and an outlet (22) that is connected or connectable to an extracorporeal blood treatment device (1); a heating element operatively operating within said heating zone to heat said fluid warming pathway (23); at least one site temperature sensor operatively operating at a site along the fluid warming pathway (23) to detect a measured temperature of fluid within the fluid warming device (18), the site temperature sensor being not at the outlet of the fluid warming pathway (23); an electronic control unit (29) operatively connected to at least said site temperature sensors; The electronic control unit (29) receiving a signal from the site temperature sensor that correlates to the measured site temperature; - correcting the measured site temperature through a correction model to obtain the actual fluid site temperature; configured to perform at least the steps: - deriving an actual fluid outlet temperature from said actual fluid site temperature; - adjusting the heating power of the heating element in order to keep the actual fluid outlet temperature at a set reference temperature value; The method is further configured to perform the steps of: A fluid warming device, wherein the compensation model is a mathematical model of a measurement error, the measurement error being a difference between the measured site temperature and the actual fluid site temperature.

13. The fluid warming device of claim 12, wherein the site temperature sensor is an inlet temperature sensor (30) or a temperature sensor located between the inlet and the outlet.

14. 1. An extracorporeal blood treatment device comprising: A blood processing device (2); an extracorporeal blood circuit (6, 7) connected to said blood treatment device (2); a blood pump (8), the pump portion of the extracorporeal blood circuit (6, 7) being adapted to be connected to the blood pump (8); a processing fluid circuit (12) operably connected to said extracorporeal blood circuit (6, 7) and / or said blood processing device (2); at least one fluid warming device (18) connected or adapted to be connected to the extracorporeal blood circuit (6, 7) for heating blood and / or to the process fluid circuit (12) for heating a process fluid, The extracorporeal blood treatment device, wherein the fluid warming device (18) is as claimed in any one of claims 1 to 13.

15. 15. The extracorporeal blood treatment device according to claim 14, wherein the fluid warming device (18) is a blood warming device that is connected or configured to be connected to a blood return line (7) of the extracorporeal blood circuit (6, 7).

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