Method and device for characterising an air sensor in an extracorporeal blood treatment device

Abstract

The present invention relates to a method and a device for characterising an air sensor (250) for use in an extracorporeal blood treatment device (200), said method comprising the following steps: conducting (S100) a mixture of blood and air through the air sensor (250) of the extracorporeal blood treatment device (200) and measuring a measured quantity of air (Am) using the air sensor (250); conducting (S200) the mixture of blood and air into a measuring chamber (132) of a characterisation device (100); irradiating (S300) the mixture of blood and air in the measuring chamber (132) of the characterisation device (100) by means of X-ray radiation; determining (S400) a determined quantity of air (Ad) in the mixture of blood and air on the basis of a result of the irradiation; and characterising (S500) the air quantity (Am) measured using the air sensor (250) by way of the air quantity (Ad) determined in the characterisation device (100) by means of the irradiation.

Description

[0001] Applicant: Fresenius Medical Care Deutschland GmbH

[0002] Our reference number: FMC31150DE

[0003] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0004] Date: January 16, 2025

[0005] Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0006] Technical field

[0007] The present invention relates to a method and a device for characterizing an air sensor in an extracorporeal blood treatment device.

[0008] State of the art

[0009] Extracorporeal blood treatment devices, such as hemodialysis or hemofiltration systems, are frequently used to treat patients with kidney failure or other conditions requiring blood purification. These devices circulate the patient's blood through an external circuit where the actual blood treatment takes place. Other examples of extracorporeal blood treatment devices include apheresis and ECMO systems.

[0010] A critical complication of extracorporeal blood therapy can occur when air is present in, enters, or is introduced into the extracorporeal bloodstream and is then returned to the patient along with the treated blood. Excessive amounts of air returned to the patient can lead to dangerous air embolisms. There are therefore standardized limits for the maximum amount of air that can be introduced into a patient's body.

[0011] To mitigate the risk of introducing excessive amounts of air, extracorporeal blood treatment devices typically feature air sensors that detect the presence of air bubbles in the bloodstream. These sensors are designed to trigger alarms and stop blood flow if an air volume exceeding predefined limits is detected. Ensuring the accuracy and reliability of these air sensors is crucial for patient safety. Applicant: Fresenius Medical Care Deutschland GmbH

[0012] Our reference number: FMC31150DE

[0013] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0014] Date: January 16, 2025

[0015] Current methods for verifying the performance and reliability of such air sensors often rely on visual inspection or manual measurement techniques. These approaches can be time-consuming and subjective, and may not provide a precise quantification of air volumes in the blood.

[0016] Description of the invention

[0017] Based on this, an objective of the present invention is to provide an improved method and an improved device for characterizing air sensors in extracorporeal blood treatment devices.

[0018] This problem is solved by a method for characterizing an air sensor with the features of claim 1. Advantageous further developments are described in the dependent claims, the description, and the figures.

[0019] Accordingly, a method for characterizing an air sensor for use in an extracorporeal blood treatment device is proposed, the method comprising:

[0020] Passing a mixture of blood and air through the air sensor of the extracorporeal blood treatment device and measuring a measured volume of air with the air sensor;

[0021] Guiding the mixture of blood and air into a measuring chamber of a characterization device;

[0022] X-rays are used to pass through the mixture of blood and air in the measuring chamber of the characterization device;

[0023] Determining a measured volume of air in the blood-air mixture based on a radiographic result; and

[0024] Characterizing the amount of air measured by the air sensor by the amount of air determined in the characterization device by means of radiation.

[0025] The proposed method offers the advantage of enabling more accurate and efficient verification of air sensors in extracorporeal blood treatment devices compared to conventional methods. Applicant: Fresenius Medical Care Deutschland GmbH

[0026] Our reference number: FMC31150DE

[0027] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0028] Date: January 16, 2025

[0029] Using the result of the radiographic measurement allows for a precise and rapid determination of the amount of air present in the blood and air mixture in the measuring chamber, thus enabling efficient characterization of the air sensor.

[0030] The term "characterization" here includes, among other things, the two different verification procedures listed below:

[0031] Firstly, the characterization of the air sensor means that it is checked at what volume of air in the blood-air mixture the air sensor of the extracorporeal blood treatment device triggers an alarm. If an alarm is triggered at a standardized maximum permissible volume of air, the characterization is considered positive. In this case, the air sensor is correctly calibrated and the extracorporeal blood treatment device can continue to be operated unchanged.

[0032] If an alarm triggered by the air sensor occurs when the air volume is below the maximum permissible volume specified by the standard, this does not initially pose a safety problem, as the extracorporeal treatment device shuts down even below the specified maximum air volume. However, this can lead to more frequent interruptions and unwanted alarms during operation. Therefore, even if the air sensor is correctly configured from a safety perspective, adjusting the corresponding alarm threshold of the air sensor is necessary in such a case. In principle, the air sensor, and thus the extracorporeal blood treatment device, can continue to be operated.

[0033] However, if the measured air volume, determined by analyzing the results of the radiographic test that triggered the air sensor alarm, exceeds the maximum permissible air volume specified by the standard, then the extracorporeal blood treatment device, and in particular its air sensor, has failed the characterization and must not be operated further. In this case, either the alarm thresholds must be readjusted or the air sensor must be replaced.

[0034] In this context, characterization means that the amount of air measured by the air sensor, which triggers an alarm within the extracorporeal blood treatment device, is checked to ensure that it does not exceed the maximum permissible amount specified by the standard. Applicant: Fresenius Medical Care Deutschland GmbH

[0035] Our reference number: FMC31150DE

[0036] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0037] Date: January 16, 2025

[0038] The air volume is sufficient, or whether an adjustment is necessary. This type of characterization can also be understood as verification of the air sensor.

[0039] Furthermore, characterization in this context means that the value of the air volume measured by the air sensor is compared to the value of the air volume determined based on radiographic measurement. Accordingly, a characteristic curve, against which the air sensor measurements are evaluated, can be created based on the air volume determined by radiographic measurement, and in this way the alarm system of the extracorporeal blood treatment device can be set or adjusted.

[0040] In other words, this aspect of characterization can involve, for example, creating a matrix that includes the air volume measured by the air sensor in the extracorporeal blood treatment device and the air volume determined by the characterization device based on radiographic measurements. From this, a characteristic curve can be generated that aligns the readings from the air sensor with the actual measurements obtained through radiographic measurements. This allows the air sensor in the extracorporeal blood treatment device to be calibrated to the measurements taken with the characterization device.

[0041] The adjustment allows, for example, different sensor types of the air sensor or different devices, such as different models of an extracorporeal blood treatment device, to be brought into synchronization of the measured values ​​measured by the respective air sensors.

[0042] This eliminates the need for individual programming of the air volume-related safety functions for the different devices, because after adjustment the air sensors behave the same or at least similarly, regardless of the device or air sensor.

[0043] The result of the irradiation could be, for example, an X-ray image of the blood-air mixture present in the measuring chamber, which was previously recorded, and / or an X-ray spectrum of the blood-air mixture present in the measuring chamber, which was previously recorded. Other representations of the result of irradiating the measuring chamber are conceivable. Applicant: Fresenius Medical Care Deutschland GmbH

[0044] Our reference number: FMC31150DE

[0045] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0046] Date: January 16, 2025

[0047] Preferably, an X-ray image is taken as a result of the irradiation, and the X-ray image is analyzed by means of image evaluation to determine the measured air volume.

[0048] Image analysis allows for a precise evaluation of the blood-air mixture present in the measuring chamber with regard to the volume of air it contains. This analysis takes into account the possibility of a blood-air foam, which, due to trapped air bubbles, also carries a portion of air. The image analysis can differentiate between the three potential phases of the blood-air mixture present in the measuring chamber: pure blood, pure air, and blood-air foam. This allows for the determination of the relative prevalence of each of these phases within the measuring chamber, and from this—and from the known volume of the measuring chamber—the amount of air present in the chamber can be calculated.

[0049] The image evaluation can include a grayscale analysis, preferably a pixel-accurate grayscale analysis, wherein the grayscale analysis preferably distinguishes between bright areas of the X-ray image that indicate the presence of air and / or gray areas that indicate the presence of blood-air foam and / or dark areas that indicate the presence of blood.

[0050] Using grayscale analysis, it is possible to precisely, verifiably and automatically determine the weightings between blood, air and blood-air foam in the measuring chamber, thus enabling an automated determination of the carried air volume.

[0051] The detection of air bubbles and / or a bubble structure in a blood-air foam can also be included in the image analysis.

[0052] It can therefore be achieved that the air volumes present in bubbles are also included in the determination of the amount of air carried.

[0053] When determining the amount of air carried and detected, the amount of air can be deduced from the ratio of detected air and / or detected foam and / or detected blood in the X-ray image, taking into account the volume of the measuring chamber.

[0054] Preferably, X-ray spectroscopy can be performed as a result of the irradiation, whereby the X-ray spectrum is analyzed to determine the measured air volume (Ad). Applicant: Fresenius Medical Care Deutschland GmbH

[0055] Our reference number: FMC31150DE

[0056] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0057] Date: January 16, 2025

[0058] By analyzing the X-ray spectrum, qualitative and quantitative conclusions can be drawn about the composition of the mixture of blood and air present in the measuring chamber, in order to reliably determine the amount of air present in the measuring chamber.

[0059] In order to continue to achieve a reliable determination of the measured air volume, the measuring chamber, in particular the measuring chamber volume of the measuring chamber, can be completely filled with the mixture of blood and air before the irradiation, in particular the taking of the X-ray image, is carried out, preferably with a predetermined settling time being observed between the completion of the complete filling of the measuring chamber and the irradiation.

[0060] By completely filling the measuring chamber with the blood-air mixture, it can be ensured that only a fresh mixture of blood and air, currently dispensed by the extracorporeal blood treatment device, is measured, and that no dead space volume or foreign air volume is present in the measuring chamber that would distort the measurement. The result of the radiographic examination then reflects the actual blood-air mixture being analyzed.

[0061] By adhering to the settling time, air and air bubbles can separate from the blood components, ensuring that the different phases of the blood-air mixture—pure blood, pure air, and a blood-air foam—are present separately and distinguishably in the measuring chamber. This allows for reliable image evaluation, which is particularly important when interpreting X-ray images.

[0062] In order to include a large part of the flow of the blood-air mixture, or preferably the entire flow, output by the extracorporeal blood treatment device in the determination of the amount of air carried, the blood-air mixture can be directed into a collection container in fluid communication with the measuring chamber, the volume of which exceeds the volume of the measuring chamber, and the irradiation, in particular the taking of the X-ray image, is performed only on the volume of the blood-air mixture present in the measuring chamber.

[0063] This allows for efficient irradiation of the measuring chamber and thus, in particular, efficient acquisition of the X-ray image, whereby the larger collection volume of the collection container is connected to the measuring chamber. Applicant: Fresenius Medical Care Deutschland GmbH

[0064] Our reference number: FMC31150DE

[0065] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0066] Date: January 16, 2025

[0067] so that a large part of the flow of the mixture of blood and air, or even the entire flow, can be evaluated.

[0068] To analyze the entire flow output of the extracorporeal blood treatment device, the blood-air mixture can be sequentially directed into more than one collection container. A radiographic examination is then performed sequentially from a measuring chamber in each filled collection container, and in particular, an X-ray image is acquired. This allows different sections of the flow to be analyzed separately. For example, different volumes of air can be injected into a blood stream for characterization purposes and then analyzed separately in the manner described.

[0069] The volume of the respective collection container can be adjusted during the introduction of the mixture of blood and air into the collection container to avoid additional air intake.

[0070] The characterization can include verifying whether the air sensor triggers an alarm in the extracorporeal blood treatment device when the amount of air detected by radiographs exceeds a predetermined level. In other words, the characterization can determine whether an air sensor in the extracorporeal blood treatment device reliably triggers an alarm.

[0071] The characterization can also include a comparison of the air volume measured by the air sensor with the air volume determined by radiographic measurement. In other words, the air sensor in the extracorporeal blood treatment device can also be calibrated using the proposed method to provide a more reliable measurement.

[0072] The problem described above is also solved by a device for characterizing an air sensor with the features of claim 12. Advantageous further developments will become apparent from the dependent claims, the description, and the figures.

[0073] Accordingly, a characterization device for characterizing an air sensor for use in an extracorporeal blood treatment device is proposed, comprising a measuring chamber for receiving a mixture of blood and air from the extracorporeal blood treatment device, an X-ray source arranged and configured to irradiate the mixture of blood and air in the measuring chamber, and a processing unit. Applicant: Fresenius Medical Care Deutschland GmbH

[0074] Our reference number: FMC31150DE

[0075] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0076] Date: January 16, 2025

[0077] which is designed to determine a specific amount of air in the blood-air mixture in the measuring chamber based on the results of the radiographic examination.

[0078] The characterization device proposed here can be used, for example, to carry out the procedure described above.

[0079] The characterization device may further include an X-ray detector configured and arranged to take an X-ray image of the mixture of blood and air in the measuring chamber, and the processing unit may be configured to determine the amount of air detected based on the X-ray image.

[0080] The X-ray source and the X-ray detector can be set up to record the X-ray image only for the volume of the measuring chamber.

[0081] The characterization device may further include an X-ray detector which is set up and arranged to record an X-ray spectrum of the mixture of blood and air in the measuring chamber, wherein the processing unit may be set up to determine the determined amount of air based on the X-ray spectrum.

[0082] The characterization device can include a collection container for introducing the mixture of blood and air, wherein the collection container is in fluid communication with the measuring chamber and the volume of the collection container exceeds the volume of the measuring chamber, wherein preferably the X-ray source and the X-ray detector are configured to record the X-ray image only for the volume of the measuring chamber.

[0083] The collection container may include a movable piston to adjust the volume of the collection container while the mixture of blood and air is being introduced into or removed from the collection container.

[0084] Preferably, and to accommodate a large portion of the flow output by the extracorporeal blood treatment device, at least two separately arranged collection containers and a changer carousel may be provided, wherein the changer carousel may be configured to rotate relative to the collection containers, and wherein the changer carousel, in a measuring position, has a measuring head with the measuring chamber and the X-ray source. Applicant: Fresenius Medical Care Deutschland GmbH

[0085] Our reference number: FMC31150DE

[0086] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0087] Date: January 16, 2025

[0088] The changer carousel can also have a filling head in a filling position for filling the respective collection container with the mixture of blood and air and preferably includes a waiting position and / or an emptying position with an emptying head.

[0089] Instead of a filling head on the changer carousel, the collection containers can also be filled with the mixture of blood and air via a stationary filling ring line, which can be sequentially connected to the collection containers.

[0090] Instead of an emptying head on the changer carousel, the collection containers can also be emptied via a stationary filling ring line, which can be sequentially connected to the collection containers.

[0091] Such a system offers the advantage of automating the characterization process for air sensors in extracorporeal blood treatment devices, reducing manual inaccuracies, and increasing the reliability of the characterization results.

[0092] Furthermore, the automated design of the sample changer carousel significantly reduces the need for manual intervention. This automation not only increases efficiency by enabling longer autonomous testing periods but also minimizes the potential for manual errors in the characterization process. The carousel's multiple positions (filling, waiting, measuring, and emptying) allow for the cyclical and efficient analysis of multiple samples, considerably increasing the throughput of the characterization process.

[0093] The system's ability to analyze X-ray images based on the absorption behavior of the blood-air mixture provides a quantitative and objective measure of the air volume. This approach eliminates the subjectivity associated with visual inspection methods and enables more consistent and reproducible results across different operators and facilities.

[0094] Brief description of the characters

[0095] Preferred further embodiments of the invention are explained in more detail by the following description of the figures, wherein:

[0096] Figure 1 schematically shows a characterization device for an air sensor of an extracorporeal blood treatment device as well as the extracorporeal blood treatment device. Applicant: Fresenius Medical Care Deutschland GmbH

[0097] Our reference number: FMC31150DE

[0098] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0099] Date: January 16, 2025

[0100] wherein the characterization device comprises an X-ray source and an X-ray detector;

[0101] Figure 2 shows a schematic detail view of the characterization device from Figure 1;

[0102] Figure 3 schematically shows a side view of an exemplary measuring head to be used in the characterization device, also schematically showing an X-ray source and an X-ray detector as well as a beam path of the X-ray radiation used;

[0103] Figure 4 is a detailed view of the measuring head from Figure 3;

[0104] Figure 5 is a partial perspective view of a characterization system for the sequential or continuous analysis of mixtures of blood and air with several stationary collection containers and a changer carousel;

[0105] Figure 6 is a schematic view of the output of an image analysis system for analyzing an X-ray image of a mixture of blood and air;

[0106] Figure 7 shows an exemplary detailed view of an X-ray image from the image analysis system of Figure 6;

[0107] Figure 8 shows an exemplary close-up of a grayscale analysis diagram from the image analysis system of Figure 6; and

[0108] Figure 9 is a schematic flowchart of a method for characterizing an air sensor according to aspects of the present disclosure.

[0109] Detailed description of preferred implementation examples

[0110] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are designated with identical reference numerals, and repeated descriptions of these elements are sometimes omitted to avoid redundancy.

[0111] Figure 1 schematically depicts an extracorporeal blood treatment device 200 at its center. The extracorporeal blood treatment device 200 has an arterial blood line 230 and a venous blood line 240, which are connected to the patient during normal operation. During normal operation, the patient's blood is drawn through the arterial blood line 230. [Applicant: Fresenius Medical Care Deutschland GmbH]

[0112] Our reference number: FMC31150DE

[0113] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0114] Date: January 16, 2025

[0115] The blood is introduced into the extracorporeal blood treatment device 200, where it is treated and then returned to the patient via the venous blood line 240.

[0116] Here, an extracorporeal blood treatment device 200 is schematically shown as a hemodialysis device comprising a hemodialysis filter 210 and indicated dialysate lines 260 for supplying and removing the dialysate for the hemodialysis filter 210.

[0117] Instead of the hemodialysis device schematically indicated here, the extracorporeal blood treatment device 200 can also be configured as a hemofiltration device, an apheresis device, an ECMO, or another known extracorporeal blood treatment device. For the application of the characterization method proposed here, it is only important that blood treated in some way with the extracorporeal blood treatment device is returned to the patient, and that the amount of air transported by the blood and then infused into the patient does not exceed a certain limit.

[0118] The blood is pumped through the extracorporeal blood treatment device 200 by means of a schematically indicated peristaltic pump 220. After treatment in the hemodialysis filter 210, the blood flows through a bubble trap 252 to remove air and to prevent large quantities of air or air boluses from being returned to the patient.

[0119] Downstream of the bladder trap 252, an air sensor 250 is provided, which monitors the blood flow and measures the amount of air Am carried by the blood flow. If the amount of air Am measured by the air sensor 250 exceeds a predetermined limit, the extracorporeal blood treatment device 200 either issues an alarm or puts the extracorporeal blood treatment device 200 into a safe state.

[0120] Standardized limits for the maximum amount of air to be infused into a patient are, for example, 0.03 ml / (min kg) for a continuous air infusion rate. Standardized limits for maximum air boluses are 0.1 ml / kg.

[0121] This results in a limit of 1.2 ml / min for a continuous air infusion rate for an adult, who can be defined, for example, as weighing 40 kg or more. This limit must be detected by the Air Sensor 250. For pediatric applications with a patient weight of, for example, 10 kg, the limit to be detected by the Air Sensor 250 is [Applicant: Fresenius Medical Care Deutschland GmbH]

[0122] Our reference number: FMC31150DE

[0123] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0124] Date: January 16, 2025

[0125] Limit value of 0.3 ml / min. In order to guarantee the safety of the respective patient and to comply with the normative requirements, the air sensor 250 must be able to reliably detect these limit values ​​in order to trigger an alarm if they are exceeded or to put the extracorporeal blood treatment device 200 into a safe state.

[0126] Accordingly, the volume of air that needs to be detected by the air sensor 250 is relatively small. Nevertheless, the safe operation of the extracorporeal blood treatment device 200 must be ensured, even with regard to the maximum volume of air to be infused into the patient's body. Therefore, the air sensor 250 must be set, and this setting must be checked, to ensure the safe operation of the extracorporeal blood treatment device 200 at all times.

[0127] To characterize the flawless function of the air sensor 250 of the extracorporeal blood treatment device 200, the setup of Figure 1 is proposed.

[0128] To enable the characterization of the air sensor 250 outside the regular operation of the extracorporeal blood treatment device 200, a test fluid supply 300 is provided. Blood from a blood supply 320 can be directed to the extracorporeal blood treatment device 200 via a blood supply line 330. The blood in the blood supply 320 is maintained within a predetermined parameter range by a heating and stirring device 322. The blood used for characterization can be, for example, bovine or human blood.

[0129] A defined infusion of air for characterization purposes is achieved via an air injector 310, where the air injector is shown here by way of example in the form of syringes arranged in syringe pumps, which can inject a predetermined volume or flow rate of air at an air injection point 312 into the blood flow contained in the blood supply line 330. Of course, it is also possible to use only a single syringe pump with a single syringe.

[0130] The test fluid supply 300 can be provided as a separate unit. In a preferred embodiment, however, the syringe pump of the air injector 310 can also be provided by a syringe pump already arranged in the extracorporeal blood treatment device 200, for example, a syringe pump intended there as a heparin pump. A syringe pump present in the extracorporeal blood treatment device 200 is then controlled accordingly for the characterization procedure described here. Applicant: Fresenius Medical Care Deutschland GmbH

[0131] Our reference number: FMC31150DE

[0132] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0133] Date: January 16, 2025

[0134] From the test fluid supply 300, a mixture of blood and air is supplied to the extracorporeal blood treatment device 200 via the arterial blood line 230, which is then passed through the extracorporeal blood treatment device 200 and accordingly also through the air sensor 250.

[0135] Theoretically, the air sensor 250 could detect the amount of air in the blood-air mixture that corresponds to the amount of air injected by the air injector 310. In practice, however, it has been found that air partially adheres to the blood lines and / or the hemodialysis filter 210, or even diffuses out through the hemodialysis filter 210. It is also possible that some of the air injected by the air injector 310 is already removed from the bloodstream at the bladder trap 252. Therefore, in practice, the entire amount of air injected by the air injector 310 does not reach the air sensor 250, so that a reliable characterization of the air sensor 250 based solely on the known amount of air injected by the air injector 310 is not possible.

[0136] However, in order to reliably characterize the air sensor 250, the mixture of blood and air that actually flowed through the air sensor 250 must be checked for the amount of air it carries.

[0137] For this purpose, the characterization device 100 and the characterization method described below are proposed, according to which, in this embodiment, an X-ray image 510 (see, for example, Figure 7) of the mixture of blood and air is taken and the amount of air in the mixture of blood and air is determined by means of the X-ray image 510.

[0138] Instead of characterization based on an X-ray image, characterization can also be carried out based on another result of irradiation using X-rays, for example on the basis of an X-ray spectrum of the mixture of blood and air recorded by X-ray spectroscopy.

[0139] The term "characterization" here includes, among other things, the two different verification procedures listed below:

[0140] Firstly, the characterization of the air sensor 250 means that it is checked at what volume of air carried in the mixture of blood and air the air sensor 250 triggers an alarm in the extracorporeal blood treatment device 200. If an alarm is triggered at the normatively specified maximum permissible volume of air, the characterization is then... Applicant: Fresenius Medical Care Deutschland GmbH

[0141] Our reference number: FMC31150DE

[0142] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0143] Date: January 16, 2025

[0144] The decision was positive. The air sensor 250 is therefore correctly adjusted and the extracorporeal blood treatment device 200 can continue to be operated unchanged in this manner.

[0145] If an alarm triggered by the air sensor 250 occurs when the air volume is below the maximum permissible volume specified by the standard, this does not initially pose a safety problem, as the extracorporeal treatment device 200 will shut down even below the maximum air volume. However, this can lead to more frequent interruptions and unwanted alarms during operation. Therefore, even if the air sensor 250 is correctly configured from a safety perspective, adjusting the alarm threshold of the air sensor 250 is necessary in such a case. In principle, the air sensor 250, and consequently the extracorporeal blood treatment device 200, can continue to be operated.

[0146] However, if the measured air volume, determined by analyzing the X-ray image 510 and triggering the alarm by the air sensor 250, exceeds the maximum permissible air volume specified by the standard, then the extracorporeal blood treatment device 200, and in particular its air sensor 250, has failed the characterization and must not be operated further. In this case, either the alarm thresholds must be readjusted or the air sensor 250 must be replaced.

[0147] In this context, characterization means that the amount of air measured by the air sensor 250, which triggers an alarm within the extracorporeal blood treatment device 200, is checked to determine whether it corresponds to the normatively specified maximum permissible amount of air, or whether an adjustment is necessary.

[0148] Furthermore, characterization in this context means that a comparison is made between the value of the air volume Am measured by the air sensor 250 and the value of the air volume Ad determined on the basis of the X-ray image 510. Accordingly, a characteristic curve, against which measurements of the air sensor 250 are evaluated, can be created based on the air volume Ad determined by means of the X-ray image 510, and in this way the alarm system of the extracorporeal blood treatment device 200 can be set or adjusted.

[0149] In other words, a matrix can be established for this aspect of the characterization, which combines the air volume Am measured by the air sensor 250 and the air volume Ad determined by the characterization device 100 based on the X-ray image 510. Applicant: Fresenius Medical Care Deutschland GmbH

[0150] Our reference number: FMC31150DE

[0151] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0152] Date: January 16, 2025

[0153] This includes a characteristic curve that aligns the measured values ​​output by the air sensor 250 with the actual measured values ​​determined based on the X-ray image 510.

[0154] This application of setting up a matrix or developing a characteristic curve for an air sensor 250, especially for adapting to specified limit values, requires a larger number of measurements, so the proposed characterization device 100 can contribute to determining characteristic curves more accurately and accelerating the determination of such characteristic curves due to its automation possibilities, reduced determination time and more accurate determination of the determined air quantity.

[0155] Before the respective measurements are carried out, the extracorporeal blood treatment device 200 is set up in the same way as it would later be used in regular operation for the treatment of a patient. In particular, for example, when a hemodialysis device is to be installed, a complete dialysis tubing system including the dialysis filter is inserted into the extracorporeal blood treatment device 200 and pre-filled (primed) as it would be for the treatment of a patient.

[0156] Accordingly, the extracorporeal blood treatment device 200 then includes a tubing system configured to receive a mixture of blood and air, the tubing system being properly inserted into the extracorporeal blood treatment device 200 such that the mixture of blood and air guided in the tubing system can be monitored for air content by the air detector 250.

[0157] To simulate and verify the activation of the alarm thresholds by the air sensor 250, the amount of infused air is gradually increased using the air injector 310. Accordingly, the test fluid supply 300 is initially started with low airflows, and then the airflow introduced into the bloodstream at the air injection point 312 is gradually increased using the air injector 310. If the amount of air flowing through the air sensor 250 is still below the maximum permissible airflow specified by the standard, no alarm should be triggered. However, if the amount of air passing the air sensor 250 exceeds the maximum permissible airflow specified by the standard, an alarm must be triggered by the air sensor 250.

[0158] The air sensor 250, used in the extracorporeal blood treatment device 200, can be a commonly used device in extracorporeal blood treatment devices 200. Applicant: Fresenius Medical Care Deutschland GmbH

[0159] Our reference number: FMC31150DE

[0160] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0161] Date: January 16, 2025

[0162] An air sensor 250 could be used. For example, an air sensor 250 could be used here, which uses ultrasound to detect air bubbles. Other known air sensors 250 are also conceivable.

[0163] The type of air sensor 250 used in the extracorporeal blood treatment device 200 is irrelevant. Rather, it must be verified whether the air sensor 250, regardless of its type, detects the specified alarm thresholds for the specified maximum permissible amount of air that can be introduced into a patient, such that an alarm is triggered when the maximum permissible amount of air is exceeded, or the extracorporeal blood treatment device 200 is switched to a safe state.

[0164] A safe condition, as used here, means, for example, that a venous clamp and / or an arterial clamp (not shown in the figures for clarity) is / are closed and the peristaltic pump 220 is stopped. This ensures that no further blood flow, which may contain an excessive amount of air, is infused into the patient.

[0165] However, it may also be sufficient to simply issue an alarm so that a treating person can then check the extracorporeal blood treatment device 200 accordingly or adjust it so that the air volume is again below the specified limits.

[0166] The proposed method, in which the amount of air present in the mixture of blood and air is determined by taking an X-ray image 510, can meet the safety requirements described above.

[0167] In particular, it is possible to characterize the air sensor 250 from the extracorporeal blood treatment device 200 in such a way that, in the presence of a critical alarm condition, it can be determined whether an alarm triggered by the air sensor 250 was appropriate.

[0168] For this purpose, the mixture of blood and air is introduced into a measuring chamber 132 of the characterization device 100, and then an X-ray image 510 of the mixture of blood and air present in the measuring chamber 132 is taken.

[0169] The amount of air present in the mixture of blood and air in measuring chamber 132 at the time the X-ray image 510 was taken is then determined from this X-ray image 510. Applicant: Fresenius Medical Care Deutschland GmbH

[0170] Our reference number: FMC31150DE

[0171] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0172] Date: January 16, 2025

[0173] The X-ray image 510 is acquired using an X-ray source 150 and an X-ray detector 152, which are arranged and configured to illuminate the mixture of blood and air present in the measuring chamber 132. In other words, the X-ray source 150 is aligned to illuminate the measuring chamber 132.

[0174] The X-ray beam path 154 is particularly preferably aligned such that the measuring chamber 132 is completely illuminated and therefore the entire volume of the measuring chamber 132 is irradiated by the X-ray beam, so that an image of the contents of the measuring chamber is captured on the X-ray detector 152. Thus, the X-ray image 510 shows the entire measuring chamber 132 and therefore also the entire volume of the blood-air mixture recorded in the measuring chamber 132.

[0175] To meet the normative requirements described above or those specified by the manufacturer of the extracorporeal blood treatment device 200, while simultaneously achieving an efficient design of the characterization device 100, the measuring chamber 132 can be designed with a relatively small measuring volume. The measuring volume of the measuring chamber 132 can, for example, be between 1 cm³ 3 and 2 cm 3 lie, preferably at 1.5 cm 3 . In this way, the X-ray source 150 and the X-ray detector 152 can also be made small, which results in a reduction of the spatial extent, the costs to be incurred and the radiation exposure.

[0176] The evaluation of the X-ray image 510 recorded on the X-ray detector 152 is carried out by means of a processing unit 156, which is only schematically indicated in the figures. In the processing unit 156, an image evaluation of the X-ray image 510 can be performed, whereby the amount of air present in the mixture of blood and air in the measuring chamber 132 is determined based on the image evaluation of the X-ray image 510.

[0177] The image evaluation can, for example, include a grayscale analysis of the X-ray image 510, whereby this grayscale analysis is preferably a pixel-accurate grayscale analysis. In the grayscale analysis, a distinction can be made, for example, between light areas 512, which indicate the presence of air, gray areas 514, which indicate the presence of blood-air foam, and dark areas 516, which indicate the presence of blood.

[0178] An exemplary X-ray image 510 is shown for illustration, for example, in Figure 7, in which the different areas mentioned, namely a bright area 512, a gray area, are shown. Applicant: Fresenius Medical Care Deutschland GmbH

[0179] Our reference number: FMC31150DE

[0180] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0181] Date: January 16, 2025

[0182] Area 514 and a dark area 516, each indicating different phases of the mixture of blood and air, are shown.

[0183] Image analysis makes it possible to detect air bubbles or bubble structures in blood-air foam and to include them in the image analysis in such a way that the air volumes present in the bubbles are taken into account when determining the amount of air.

[0184] In the embodiment of the characterization device 100 shown in Figures 1 and 2, a collection container 110 is also provided, which offers a collection volume 114 into which the mixture of blood and air from the extracorporeal blood treatment device 200 can be introduced. Preferably, the collection container 110 has a movable piston 112 that limits the collection volume 114.

[0185] The piston 112 can be controlled in such a way that the mixture of blood and air flows into the collection volume 114 without further contact with air. In other words, the piston 112 can move in such a way that the collection volume 114 always corresponds to the volume of the mixture of blood and air contained within it, and thus no additional dead space or air space exists in the collection volume 114.

[0186] The total collection volume 114 preferably corresponds to the delivery volume of the peristaltic pump 220 of the extracorporeal blood treatment device 200 over a predetermined period, for example, over 60 seconds. In other words, the collection container 110 completely receives the entire flow of the blood-air mixture that flows from the extracorporeal blood treatment device 200 during the predetermined period.

[0187] The piston 112 in the collection container 110 can be designed to keep the mixture of blood and air received in the collection volume 114 under slight pressure, so that the mixture of blood and air in the collection volume 114 is pressed against a top of the collection volume 114 and fills the entire collection volume 114.

[0188] To determine the amount of air in the mixture of air and blood based on the X-ray image 510, a measuring head 130 is provided on the collection container 110, wherein the measuring head 130 proposed here comprises the measuring chamber 132. A possible embodiment of the measuring head 130 is described in more detail below with reference to Figures 3 and 4. The measuring chamber 132 is arranged at the highest point of the measuring head 130, so that air and air bubbles can rise into the measuring chamber 132. Applicant: Fresenius Medical Care Deutschland GmbH

[0189] Our reference number: FMC31150DE

[0190] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0191] Date: January 16, 2025

[0192] Due to the slight preload of the piston 112 in its installed position against gravity, in this case upwards, both the measuring head 130 and the measuring chamber 132 are always completely filled with the mixture of blood and air. Furthermore, this ensures a constant back pressure for the dialysis machine during measurement.

[0193] The above definition of the term also applies to the following components of the present application.

[0194] Preferably, the mixture of blood and air is introduced into the collection volume 114 of the collection container 110 via a blood exchange line 140, which is in fluid communication with the venous blood line 240 of the extracorporeal blood treatment device 200. The mixture of blood and air preferably first flows through the measuring chamber 132 and is then filled into the volume provided by the measuring head 130 and the collection volume 114 of the collection container 110. This ensures that the measuring chamber 132 is always completely filled with the mixture of blood and air.

[0195] Using the proposed characterization device 100, the flow of the blood-air mixture, which is delivered by the extracorporeal blood treatment device 200 via the venous blood line 240 and which has actually passed through the air sensor 250, can be introduced into the measuring chamber 132. The entire flow delivered via the venous blood line 240 over a predetermined period passes through the measuring chamber 132 and is collected in the collection volume 114. For example, the flow generated over one minute can be recorded here.

[0196] If the collection container 110 or its collection volume 114 is completely filled with the mixture of blood and air after the specified period, resulting, for example, in a peristaltic pump 220 flow rate of 600 ml / min and a duration of one minute, in a total volume of 600 ml in the collection container 110, a settling phase can occur before the actual acquisition of the X-ray image 510.

[0197] For example, the mixture of blood and air can be allowed to settle for a predetermined settling time t, for example, for a settling time t of one minute up to five minutes. During the settling time t, air bubbles present in or forming within the mixture of blood and air can rise upwards towards the measuring chamber 132.

[0198] Furthermore, the air carried in the mixture can also rise upwards. Applicant: Fresenius Medical Care Deutschland GmbH

[0199] Our reference number: FMC31150DE

[0200] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0201] Date: January 16, 2025

[0202] Since the measuring chamber 132 is located at the top of the collection container 110 or the collection volume 114 and the measuring head 130, the volume of air present in the mixture of blood and air rises and collects in the measuring chamber 132. When the X-ray image 510 of the measuring chamber 132 is then taken after the settling time t has elapsed, it can be determined, based on the X-ray image 510, in which areas of the measuring chamber 132 air is present, in which areas of the measuring chamber 132 a blood-air foam is present, and in which areas of the measuring chamber 132 pure blood is present.

[0203] Since the volume of measuring chamber 132 is known, the amount of air present in measuring chamber 132 can be determined based on the ratio of the detected areas containing air, the areas containing blood, and the areas containing blood-air foam. This is because, after the settling time t, a significant portion of the air will be located in measuring chamber 132, allowing the amount of air to be determined based on the evaluation of the X-ray image 510.

[0204] When evaluating the X-ray image 510 to determine the amount of air present in the measuring chamber 132 and drawing the corresponding conclusions about its significance for the blood-air mixture that has flowed through the measuring chamber 132, it can be taken into account that the rising of air and air bubbles in the collection container 110 requires a certain settling time t. In order to measure the total amount of air present in the blood-air mixture in the collection container 110, it is necessary to wait a sufficient amount of time until all the air from the blood-air mixture has risen into the measuring chamber 132.

[0205] If this time is to be shortened, a corresponding correction factor, which is determined empirically and / or experimentally, can be used to calculate the amount of air that has not yet risen in the collection container 110 from the amount of air present in the measuring chamber 132 after a certain time. In other words, a shortened settling time t can also be provided for using a correction factor if the proportion of air or air bubbles that typically rises into the measuring chamber 132 after the shortened settling time t is known.

[0206] For example, it may have been empirically and / or experimentally determined that after a settling time of 90 seconds, 92 percent of the air and air bubbles have typically already risen into the measuring chamber 132. Accordingly, this correction factor can then be used to calculate the image size of an X-ray image 510 taken after a settling time of 90 seconds. (Applicant: Fresenius Medical Care Deutschland GmbH)

[0207] Our reference number: FMC31150DE

[0208] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0209] Date: January 16, 2025

[0210] The air volume determined from the X-ray image 510 can be extrapolated to the actual air volume using the correction factor.

[0211] The varying blood flow rates of the peristaltic pump 220 can lead to different bubble sizes within the blood-air mixture when it is introduced into a collection container 110 or a collection volume 114. The smaller the bubbles within the blood-air mixture, the longer the settling time t typically required for air bubbles and air to rise into the measuring chamber 132. Accordingly, the correction factor can also depend on the flow rate of the peristaltic pump 220.

[0212] For example, in the example above, after a settling time of 90 seconds at a pumping rate of 600 ml / min, 92 percent of the air volume present in the blood-air mixture in the collection container 110 may have already risen into the measuring chamber 132. At a pumping rate of only 200 ml / min, however, the size of the air bubbles may be correspondingly larger, so that after a settling time of 90 seconds, 94 percent of the air volume may already have risen into the measuring chamber 132. Accordingly, a correction factor used to achieve a shorter settling time t before taking the X-ray image 510 can also be adjusted to the respective pumping rate.

[0213] Preferably, the collection volume 114 is filled from the top in order to layer the fresh mixture of blood and air, which still contains the highest proportion of air, at the top of the collection volume 114. This ensures that the rising of the air can be accelerated.

[0214] Preferred dimensions for the collection container 110 include, for example, a cylindrical shape with a maximum height of 50 cm to 100 cm and a diameter of more than 10 cm. This ensures the most efficient possible ascent of air within the collection container 110, while simultaneously providing sufficiently large volumes for the respective collection volume 114 to capture the entire flow of the blood-air mixture over a specified period, for example, one minute.

[0215] Figure 3 shows a section of an exemplary characterization device 100, mainly showing the measuring head 130, which comprises the measuring chamber 132. Applicant: Fresenius Medical Care Deutschland GmbH

[0216] Our reference number: FMC31150DE

[0217] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0218] Date: January 16, 2025

[0219] Measuring chamber 132 is shaped accordingly to achieve complete illumination by the X-ray beam generated by the X-ray source 150.

[0220] Here, the path of the X-ray beam emanating from the X-ray source 150 is shown schematically with reference numeral 154. The beam path 154 is divergent. Accordingly, due to the divergent X-ray beam emitted from the X-ray source 150, the shape of the measuring chamber 132 is also divergent. In the illustrated embodiment, the measuring chamber 132 is essentially conical so that it can be completely illuminated by the beam path 154 of the divergent X-ray beam and no shadowing occurs. In the sectional view shown, the measuring chamber 132 is trapezoidal.

[0221] The X-ray beam passing through the measuring chamber 132 then hits the X-ray detector 152, which then detects a digital X-ray image 510 with high resolution.

[0222] In other words, a complete evaluation of the volume of measuring chamber 132 can be performed on this basis. All areas of measuring chamber 132 can also be fully evaluated via image analysis of the X-ray image 510. Using the proposed image analysis, the presence of air in measuring chamber 132 can be determined with greater accuracy, as all three different phases in which the mixture of blood and air can exist can be taken into account.

[0223] The measuring head 130 can be mounted on a collection container 110 (not shown here), as can be seen particularly well in Figure 4. For this purpose, a recessed section with a reduced diameter is provided, which can be inserted into the collection container 110 and then sealed to the collection container 110 by means of a seal 138.

[0224] In order to enable complete filling of the measuring chamber 132 with the mixture of blood and air, the measuring chamber 132 has a vent channel 136, which in the embodiment shown in Figure 3 is designed to rise.

[0225] This ensures that no foreign air, foam, or blood volume is present in the measuring chamber 132 when it is filled with the blood-air mixture via the blood exchange line 140. Any residual air or blood that may be present in the measuring chamber 132 can be vented through the vent channel 136. Applicant: Fresenius Medical Care Deutschland GmbH

[0226] Our reference number: FMC31150DE

[0227] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0228] Date: January 16, 2025

[0229] or residual foam is displaced. This is essentially a rinsing process carried out via the vent channel 136. This ensures that the measuring chamber 132 is completely filled with the mixture of blood and air to be examined and that no residual air or blood volumes are present that could distort the measurement.

[0230] The vent channel 136 is closed after the measuring chamber 132 has been completely filled with the fresh mixture of blood and air, for example, by means of a valve (not shown) connected to the vent channel 136. The valve can be located directly on the measuring chamber 132, so that after the measuring chamber 132 has been completely filled or after it has been flushed with the fresh mixture of blood and air for the actual measurement, the vent channel 136 has no further influence. In other words, the volume of the measuring chamber 136 is defined and closed off by the valve.

[0231] As can be seen particularly well in Figure 4, the measuring head 130 has a sliding surface 134 on its inner side, which is designed to guide rising air bubbles and air that rise within the collection volume 114 in the collection container 110 upwards towards the measuring chamber 132. The appropriately shaped sliding surfaces 134 prevent the formation of dead spaces in which air bubbles could accumulate and thus not find their way into the measuring chamber 132.

[0232] The provided sliding surfaces 134 ensure that the air bubbles separating from the blood-air mixture in the collection volume 114 can settle upwards into the measuring chamber 136, and then into the measuring chamber 132. Furthermore, rising blood-air foam can also be directed into the measuring chamber 132 in this way.

[0233] Figure 6 schematically shows the output of an image analysis 500, as it might be displayed on a screen. The output of the image analysis 500 schematically shows an exemplary X-ray image 510 and, similarly schematically, the diagram of a grayscale analysis 550.

[0234] X-ray image 510 corresponds to the image produced when the X-ray beam passes through the conically shaped measuring chamber 132 and is projected onto the X-ray detector 152. It should be noted that the X-ray image completely irradiates the volume of the measuring chamber 132. Due to the different absorption properties of air and blood, the different areas will show varying degrees of blackening. Applicant: Fresenius Medical Care Deutschland GmbH

[0235] Our reference number: FMC31150DE

[0236] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0237] Date: January 16, 2025

[0238] The X-ray image 510 can be used to determine whether an area of ​​the X-ray image 510 shows blood, air, or whether a blood-air foam is more likely to be seen.

[0239] X-ray image 510 is shown schematically again in an enlarged view in Figure 7. At least the three areas mentioned are clearly visible in the schematically shown exemplary X-ray image 510, each of which can be clearly distinguished from the others by a distinct boundary.

[0240] In the schematic representation of Figure 7, a light area 512, which corresponds to the presence of air in the measuring chamber 132, a dark area 516, which corresponds to the presence of blood in the measuring chamber 132, and a grey area 514, which corresponds to the presence of a blood-air foam in the measuring chamber 132, can be distinguished from one another.

[0241] By analyzing the data from these areas, it is possible, for example, to determine the weighting of the volumes of blood and air in measuring chamber 132. Since the volume of measuring chamber 132 is known, the weighting can then be used to directly calculate the amount of air trapped in the chamber.

[0242] The image analysis can be carried out in a simple form by evaluating the respective displayed areas of the three regions, which are then compared to each other in order to determine the corresponding weighting.

[0243] In an alternative evaluation, the weighting is carried out via a grey value analysis.

[0244] Figure 8 schematically shows a diagram of a grayscale analysis 550 of the X-ray image 510. The x-axis of the diagram represents the respective grayscale values ​​of the pixels, with the light areas on the left and the dark areas on the right. The y-axis represents the number of pixels or their frequency for each grayscale value.

[0245] Using grayscale analysis 550, a pixel-precise evaluation can therefore be carried out here, whereby each pixel of the X-ray image 510 is considered and classified according to its respective grayscale value. Applicant: Fresenius Medical Care Deutschland GmbH

[0246] Our reference number: FMC31150DE

[0247] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0248] Date: January 16, 2025

[0249] Accordingly, a light value peak 552 can be seen at the left end of the diagram, corresponding to the presence of air in measuring chamber 132. At the right end of the diagram, a dark value peak 556 can be seen, corresponding to the presence of blood in measuring chamber 132. Between the light value peak 552 and the dark value peak 556, a gray value peak 554 can be seen, corresponding to the presence of a blood-air foam in the measuring chamber.

[0250] The pixel counts of the light value peak 552, the gray value peak 554 and the dark value peak 556 can be related to each other and in this way, as well as with knowledge of the measuring chamber volume of the measuring chamber 132, the amount of air present in the measuring chamber 132 can be determined.

[0251] When evaluating the bright area 512, the gray area 514, and the dark area 516 of the X-ray image 510, these areas can be distinguished from one another, for example, by predefined gray value limits. An image evaluation of the X-ray image 510 along the vertical axis can then provide information about the proportion of blood in the measuring chamber 132, the proportion of air, and the proportion of blood-air foam.

[0252] In one method of evaluating the X-ray image 510, the ratio of blood to air can be determined based on the blackening of the image. The blacker the X-ray image 510, the higher the proportion of blood in the measuring chamber 132. Conversely, if the X-ray image 510, which is captured by the X-ray detector 152, is completely blackened, or has its darkest color determined empirically, then the measuring chamber 132 is completely filled with blood. If, on the other hand, the X-ray image 510 is virtually white, or has its lightest color determined empirically, then the X-ray radiation has passed through the measuring chamber 132 without further absorption, and it can be concluded that the measuring chamber 132 was filled exclusively with air.

[0253] Other gray values, lying between the gray value for a measuring chamber 132 filled exclusively with air and the gray value for a measuring chamber 132 completely filled with blood, indicate that a mixture of blood and air is present in the measuring chamber 132. Depending on the respective gray value, the ratio between air and blood in the measuring chamber 132 can then be determined. With known measuring chamber geometry and, in particular, known measuring chamber volume, the amount of air in the measuring chamber 132 can then be directly inferred. Applicant: Fresenius Medical Care Deutschland GmbH

[0254] Our reference number: FMC31150DE

[0255] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0256] Date: January 16, 2025

[0257] In the grayscale analyses described above, increased accuracy can be achieved by using appropriate correction factors that take into account the hematocrit content of the blood used, because the X-ray absorption of the blood varies with the hematocrit content.

[0258] Figure 5 shows a characterization system in which several collection containers 110 are provided, which in the illustrated embodiment are each arranged in a stationary manner.

[0259] The stationary collection containers 110 are each addressed sequentially by the positions and corresponding function heads of a changer carousel 402 described below.

[0260] In the illustrated embodiment, the changer carousel 402 has an emptying position 410, which includes an emptying head that allows a collection container 110 connected to the emptying head to be emptied. For this purpose, a blood exchange line 140 (schematically indicated) is provided, through which the collection container 110, and in particular its collection volume 114, connected to the corresponding emptying head, can be emptied. For this purpose, the piston 112 of the collection container 110 can be actuated, for example, so that all the blood or the mixture of blood and air collected in the collection container 110 is forced out of the collection container 110 via the blood exchange line 140.

[0261] The changer carousel 402 further comprises a measuring position 420 with a measuring head 130, which corresponds to the measuring head 130 including the measuring chamber 132, the X-ray source 150, the X-ray detector 152 and the corresponding evaluation device 156, which has already been described in detail with reference to Figures 1 to 4. Accordingly, at this measuring position 420, when connected to a collection container 110, the amount of air present in the respective collection container 110 or the measuring chamber 132 can be determined.

[0262] Furthermore, the changer carousel 402 includes a waiting position 430 in which the collection container 110 is merely closed and a settling of the mixture of blood and air is achieved over a predetermined settling time t in order to allow air and air bubbles to rise.

[0263] Also present in the changer carousel 402 is a filling position 440 with a filling head which includes a blood exchange line 140, via which the respective connected applicant: Fresenius Medical Care Deutschland GmbH

[0264] Our reference number: FMC31150DE

[0265] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0266] Date: January 16, 2025

[0267] Collection container 110 and in particular the collection volume 114 can be filled with the mixture of blood and air, which is supplied, for example, via the venous blood line 240 from the extracorporeal blood treatment device 200.

[0268] When the changer carousel 402 rotates in the direction of rotation 404, the stationary collection containers 110 can be sequentially filled one after the other at the filling position 440 with the mixture of blood and air using the filling head.

[0269] Then, after a further rotation of the changer carousel 402, this now filled collection container 110 is addressed from the waiting position 430, so that over a predetermined settling time t, a settling of the mixture of blood and air in the collection container 110 can be achieved and air and air bubbles can rise.

[0270] After a further rotation of the changer carousel 402, the collection container 110 under consideration is then connected to the measuring head at the measuring position 420, so that the mixture of blood and air can enter the measuring chamber 132 and then an X-ray image 510 of the filled measuring chamber 132 can be taken. In this way, the amount of air present in the measuring chamber 132 can be determined and thus the amount of air for the collection container 110 under consideration can be determined.

[0271] After a further rotation of the changer carousel 402, the collection container 110 is then connected to the emptying position 410 and the emptying head, and the mixture of blood and air present in the collection container 110 is emptied again from the collection container 110 via the blood exchange line 140.

[0272] In this way, an air sensor can be sequentially characterized in an automatic procedure, whereby the entire blood flow which is output from the extracorporeal blood treatment device 200 via the arterial blood line 240 is sequentially recorded in the collection containers 110.

[0273] Instead of the filling head described on the changer carousel, the collection containers can also be filled with the mixture of blood and air via a stationary filling ring line, which can be sequentially connected to the collection containers.

[0274] Instead of the described emptying head on the changer carousel, the collection containers can also be emptied via a stationary filling ring main that can be sequentially connected to the collection containers. Applicant: Fresenius Medical Care Deutschland GmbH

[0275] Our reference number: FMC31150DE

[0276] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0277] Date: January 16, 2025

[0278] This means that the changer carousel 402 can only include the measuring position 420 with the measuring head 130, which is then sequentially connected to the collection containers 110 by the rotation of the changer carousel 402. The remaining functions of filling, stabilizing, and emptying the collection containers 110 can be performed stationary and separately from the changer carousel 402.

[0279] In a sequential process, a settling time t is also traversed, and then an X-ray image 510 of the measuring chamber 132 is taken at the respective collection container 110 in order to determine the amount of air taken in this collection container 110.

[0280] This allows, on the one hand, that a large quantity of blood and air mixture can be analyzed via automated detection, and on the other hand, continuous operation of the extracorporeal blood treatment device 200 can be enabled, whereby the entire volume flowing through the extracorporeal blood treatment device 200 is collected and analyzed accordingly.

[0281] This allows for both automation of the measurement process and a more accurate characterization of the air sensor, as the entire flow of the blood and air mixture is captured and analyzed.

[0282] Furthermore, automating the measurement process can reduce the overall time required for characterization, which is also achieved simply by using the X-ray image, as a quick result can be obtained in a very short time through the acquisition of the X-ray image and the subsequent evaluation using grayscale analysis.

[0283] In a preferred further embodiment, the different collection containers 110, each addressed by the changer carousel 402, can also be completely identical in that each of the collection containers 110 also has a measuring head 130 with a measuring chamber 132. After the corresponding collection container 110 has been filled, the air volume to be determined can then rise into the respective measuring chamber 132. In this case, the changer carousel 402 is then designed such that only the X-ray source 150 and the X-ray detector 152 are carried at the measuring position 420, but not a separate measuring chamber. At the corresponding measuring position 420, the X-ray detector 152 and the X-ray source 150 are then attached to the collection container 110. Applicant: Fresenius Medical Care Deutschland GmbH

[0284] Our reference number: FMC31150DE

[0285] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0286] Date: January 16, 2025

[0287] The intended measuring chamber 132 is positioned so that the X-ray image 510 can be easily taken.

[0288] In a preferred further embodiment, the mixture of blood and air, after passing through the air sensor 250 of the extracorporeal blood treatment device 200, is introduced into the measuring chamber 132 of the characterization device 100, and the measurement and acquisition of the X-ray image 510 then take place either continuously or sequentially at short intervals. In other words, a continuous measurement of the flow rate of the mixture of blood and air through the measuring chamber 132 can be achieved.

[0289] During continuous measurement in the flow of the blood-air mixture through measuring chamber 132, foaming and separation of air and blood do not typically occur. Accordingly, only different shades of gray can be distinguished on the X-ray image 510, which, as described above, indicate the blood-to-air ratio at the time the X-ray image 510 was taken. The hematocrit level can also be taken into account in this proposed continuous measurement using a correction factor.

[0290] To determine the total volume of air infused during continuous measurement, the instantaneous flow rate must also be known. This is typically known via the peristaltic pump 220, another pumping device, or a flow meter in the extracorporeal blood treatment device 200. Accordingly, the volumes of air recorded via the X-ray image 510 at a specific time can then be extrapolated to the relevant time period, summed, or integrated.

[0291] It must be taken into account in the procedures carried out here for characterizing the air sensor 250 that there is also a time delay between the passage of a certain volume of liquid through the air sensor 250 and the subsequent entry of this volume of liquid into the measuring chamber 132.

[0292] In other words, the air sensor 250 and the measuring chamber 132 are spaced apart, with the measuring chamber 132 located downstream of the air sensor 250. The resulting time delay must be taken into account when characterizing the air sensor 250 and its behavior. Applicant: Fresenius Medical Care Deutschland GmbH

[0293] Our reference number: FMC31150DE

[0294] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0295] Date: January 16, 2025

[0296] For example, the volume of liquid between the air sensor 250 and the measuring chamber 132, which determines the time delay, could be 100 ml. With a pump rate of the peristaltic pump 220 of, for example, 200 ml / min, a volume of liquid that has flowed through the air sensor 250 will then only reach the measuring chamber 132 30 seconds later. This time delay must be taken into account.

[0297] For characterization measurements to verify the correct setting of the alarm thresholds of the air sensor 250, or for measurements to record a characteristic curve matrix, it can therefore be useful to operate with a fixed airflow through the corresponding air injector 310 for a specified period until a quasi-steady state is established in the system. For example, when using a collection container 110, a steady state can be established, which is then maintained until the intended collection volume 114 of the collection container 110 is completely filled. Only when the collection volume 114 is completely filled is a new airflow initiated at the air injector 310.

[0298] Furthermore, in a configuration of the measuring head 130 not shown here, an air collection volume can be provided above the actual measuring chamber 132. The measuring chamber 132 is then located at the lower end of this air collection volume. Only when this air collection volume, which lies above the measuring chamber 132, is completely filled with air can the presence of air be detected in the measuring chamber 132. As long as the air collection volume above the measuring chamber 132 is not yet completely filled with air, the measuring chamber 132 contains only blood or a blood-air foam. In this way, even with larger collection volumes 114, an air volume exceeding a certain value can be reliably determined using a relatively small measuring chamber 132. In other words, a quantity of air exceeding the air collection volume above the measuring chamber 132 can be determined in this way.

[0299] In another embodiment, not shown in the figures, an X-ray image of the entire collection volume 114 can also be taken. For this purpose, an X-ray source is provided that can penetrate the entire collection volume 114, and an X-ray detector is provided that can then record the entire beam path passing through the collection volume 114. Using such an X-ray image, the proportion of air, blood, and blood-air foam in the collection volume 114 can then also be determined. In other words, the collection volume 114 is analyzed. Applicant: Fresenius Medical Care Deutschland GmbH

[0300] Our reference number: FMC31150DE

[0301] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0302] Date: January 16, 2025

[0303] then essentially to the measuring chamber. However, such training can be complex to implement due to the necessary dimensions of the X-ray source and detector, as well as the resulting radiation exposure.

[0304] Figure 9 schematically shows a flowchart of the procedure for characterizing an air sensor.

[0305] In a first step, S100 passes a mixture of blood and air through an air sensor of an extracorporeal blood treatment device, and the amount of air present in the mixture of blood and air is measured using the air sensor of the extracorporeal blood treatment device.

[0306] In a second step, S200 directs the mixture of blood and air, which has previously passed through the air sensor of the extracorporeal blood treatment device, into a measuring chamber of a characterization device.

[0307] In a third step S300, the mixture of blood and air present in the measuring chamber of the characterization device is then irradiated using X-rays.

[0308] In a fourth step, S400 uses a result from the radiographic examination, such as an X-ray image, to determine the amount of air present in the mixture of blood and air in the measuring chamber.

[0309] In a fifth step, S500, the amount of air measured by the air sensor is then verified by the amount of air determined by means of the radiation measurement.

[0310] Where applicable, all individual features shown in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention.

[0311] The present invention relates to a method and an apparatus. The method comprises: guiding (S100) a mixture of blood and air through the air sensor (250) of the extracorporeal blood treatment device (200) and measuring a measured volume of air (Am) with the air sensor (250); guiding (S200) the mixture of blood and air into a measuring chamber (132) of an Applicant: Fresenius Medical Care Deutschland GmbH

[0312] Our reference number: FMC31150DE

[0313] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0314] Date: January 16, 2025

[0315] Characterization device (100); X-ray irradiation (S300) of the mixture of blood and air in the measuring chamber (132) of the characterization device (100) using X-rays; determination (S400) of a determined quantity of air (Ad) in the mixture of blood and air based on a result of the irradiation; and characterization (S500) of the quantity of air (Am) measured by the air sensor (250) by the quantity of air (Ad) determined in the characterization device (100) by means of the irradiation. Applicant: Fresenius Medical Care Deutschland GmbH

[0316] Our reference number: FMC31150DE

[0317] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0318] Date: January 16, 2025

[0319] List of reference signs

[0320] 100 characterization device

[0321] 110 collection containers

[0322] 112 pistons

[0323] 114 collection volume

[0324] 130 measuring head

[0325] 132 Measuring chamber

[0326] 134 Sliding surface

[0327] 136 Ventilation duct

[0328] 138 Seal

[0329] 140 Blood exchange line

[0330] 150 X-ray source

[0331] 152 X-ray detector

[0332] 154 Path of the X-ray beam

[0333] 200 extracorporeal blood treatment devices

[0334] 210 hemodialysis filters

[0335] 220 peristaltic pump

[0336] 230 venous blood vessel

[0337] 240 arterial blood vessel

[0338] 250 air sensor

[0339] 252 bladder trap

[0340] 260 dialysate lines

[0341] 300 test fluid supply

[0342] 310 Air injector

[0343] 312 Air injection point

[0344] 320 Blood Supply Applicant: Fresenius Medical Care Deutschland GmbH

[0345] Our reference number: FMC31150DE

[0346] Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device

[0347] Date: January 16, 2025

[0348] 322 Heating and stirring device

[0349] 330 Blood supply line

[0350] 400 Characterization System

[0351] 402 Changer Carousel

[0352] 404 Direction of rotation

[0353] 410 Emptying position

[0354] 420 measuring position

[0355] 430 Waiting position

[0356] 440 Filling position

[0357] 500th output of the image analysis

[0358] 510 X-ray image

[0359] 512 bright area

[0360] 514 grey area

[0361] 516 dark area

[0362] 550 Grey value analysis

[0363] 552 Brightness Peak

[0364] 554 Grey value peak

[0365] 556 Dark value peak

Claims

Applicant: Fresenius Medical Care Deutschland GmbH Our reference number: FMC31150DE Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device Date: January 16, 2025 Claims 1. Method for characterizing an air sensor (250) for use in an extracorporeal blood treatment device (200), the method comprising: o Guiding (S100) a mixture of blood and air through the air sensor (250) of the extracorporeal blood treatment device (200) and measuring a measured amount of air (Am) with the air sensor (250); o Conveying (S200) the mixture of blood and air into a measuring chamber (132) of a characterization device (100); o X-ray irradiation (S300) of the mixture of blood and air in the measuring chamber (132) of the characterization device (100); o Determining (S400) a determined volume of air (Ad) in the mixture of blood and air based on a result of radiographic examination; and o Characterizing (S500) the amount of air (Am) measured by the air sensor (250) by the amount of air (Ad) determined in the characterization device (100) by means of irradiation.

2. Method according to claim 1, wherein an X-ray image (510) is taken as a result of the irradiation and the X-ray image (510) is analyzed by means of an image evaluation to determine the determined air quantity (Ad).

3. Method according to claim 2, wherein the image evaluation of the X-ray image (510) comprises a gray value analysis, preferably a pixel-accurate gray value analysis, wherein the gray value analysis preferably distinguishes between bright areas (512) indicating the presence of air, and / or gray areas (514) indicating the presence of blood-air foam, and / or dark areas (516) indicating the presence of blood.

4. Method according to claim 2 or 3, wherein the detection of air bubbles and / or a bubble structure in a blood-air foam is included in the image evaluation.

5. Method according to one of claims 2 to 4, wherein the X-ray image (510) consists of a ratio of detected air and / or detected foam and / or detected blood. Applicant: Fresenius Medical Care Deutschland GmbH Our reference number: FMC31150DE Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device Date: January 16, 2025 Taking into account the volume of the measuring chamber (132), the determined air quantity (Ad) is determined.

6. Method according to one of the preceding claims, wherein an X-ray spectroscopy is carried out as a result of the irradiation and the X-ray spectrum is analyzed to determine the determined air quantity (Ad).

7. Method according to one of the preceding claims, wherein the measuring chamber (132), in particular the measuring chamber volume of the measuring chamber (132), is completely filled with the mixture of blood and air before the irradiation is carried out, in particular the X-ray image (510) is taken, wherein preferably a predetermined settling time (t) is observed between the completion of the complete filling of the measuring chamber (132) and the irradiation.

8. Method according to one of the preceding claims, wherein the mixture of blood and air is directed into a collection container (110) in fluid communication with the measuring chamber (132), the volume of which exceeds the volume of the measuring chamber (132), and the irradiation, in particular the acquisition of the X-ray image (510), is carried out only for the measuring chamber (132).

9. Method according to one of the preceding claims, wherein the mixture of blood and air is sequentially fed into more than one collection container (110) and a sequential radiographic examination is performed by a measuring chamber (132) of each filled collection container (110) and in particular an X-ray image (510) is taken.

10. Method according to claim 8 or 9, wherein the volume of the respective collection container (110) is adjusted during the introduction of the mixture of blood and air into the collection container (110) in order to avoid additional air ingress.

11. Method according to one of the preceding claims, wherein the characterization comprises checking whether the air sensor (250) triggers an alarm in the extracorporeal blood treatment device (200) when the determined air quantity (Ad) exceeds a predetermined air quantity, or applicant: Fresenius Medical Care Deutschland GmbH Our reference number: FMC31150DE Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device Date: January 16, 2025 wherein the characterization includes a comparison of the air quantity (Am) measured by the air sensor (250) with the determined air quantity (Ad).

12. Characterization device (100) for characterizing an air sensor (250) for use in an extracorporeal blood treatment device (200), comprising: o a measuring chamber (132) for receiving a mixture of blood and air from the extracorporeal blood treatment device (200); o an X-ray source (150) arranged and configured to irradiate the mixture of blood and air in the measuring chamber (132) with X-rays; and o a processing unit (156) configured to determine a determined quantity (Ad) of the mixture of blood and air in the measuring chamber (132) based on the result of the irradiation.

13. Characterization device (100) according to claim 12, further comprising an X-ray detector (152) which is configured and arranged to take an X-ray image (510) of the mixture of blood and air in the measuring chamber (132), wherein the processing unit (156) is configured to determine the determined air quantity (Ad) based on the X-ray image (510).

14. Characterization device according to claim 13, wherein the X-ray source (150) and the X-ray detector (152) are configured to record the X-ray image (510) only for the volume of the measuring chamber (132).

15. Characterization device according to one of claims 12 to 14, comprising an X-ray detector (152) which is configured and arranged to record an X-ray spectrum of the mixture of blood and air in the measuring chamber (132), wherein the processing unit (156) is configured to determine the determined amount of air (Ad) based on the X-ray spectrum.

16. Characterization device according to any one of claims 12 to 15, comprising a collection container (110) for introducing the mixture of blood and air, wherein the collection container is in fluid communication with the measuring chamber (132) and the volume of the collection container (110) exceeds the volume of the measuring chamber (132). Applicant: Fresenius Medical Care Deutschland GmbH Our reference number: FMC31150DE Title: Method and apparatus for characterizing an air sensor in an extracorporeal blood treatment device Date: January 16, 2025 17. Characterization device (100) according to claim 16, wherein the collection container (110) comprises a movable piston (112) to adjust the volume of the collection container (110) while the mixture of blood and air is directed into or removed from the collection container (110).

18. Characterization device (100) according to one of claims 12 to 17, comprising at least two separately arranged collection containers (110) and a changer carousel (402) configured to rotate relative to the collection containers (110), wherein the changer carousel (402) in a measuring position (420) has a measuring head with the measuring chamber (132), the X-ray source (150) and preferably the X-ray detector (152).

19. Characterization device (100) according to claim 18, wherein the changer carousel (402) has a filling head in a filling position (440) for filling the respective collection container (110) with the mixture of blood and air, and preferably comprises a waiting position (430) and / or an emptying position (410) with an emptying head.

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