FIELD OF THE INVENTION

The present invention relates to a device for blood filtering, in particular to a filtering device allowing a quick and simple filtration process for the separation of blood cells.

BACKGROUND OF THE INVENTION

Blood filtering is required for the separation of the specific components of the human blood. In particular, the separation is required as particular analysis may be carried out on particular components of the human blood only, wherein other blood com- ponents may disturb the analysis. The human blood has different components, for example erythrocytes, i.e. red blood cells, which may have a size of about 7-8 μιτι, leucocytes, i.e. white blood cells, which may have a size of about 8 to 20 μιτι, and thrombocytes, i.e. platelets, which may have a size of about 1 .5 to 3 μιτι, as well as the blood plasma. The erythrocytes, the leucocytes, and the thrombocytes represent more than 40 vol.-% of the whole blood. In order to separate the different components of the human blood, a centrifugation process is established. However, a centrifugation process requires a considerable amount of time and a considerable complexity of an apparatus. For particular purposes, it may be required to obtain a separation of the blood components in a short time and with a minimum complexity of apparatus. Further, it may be required to provide an apparatus which is easy to handle, in particular for urgent or emergency medical applications.

A subsequent whole blood separation into plasma/serum can be advantageous for Point-of-Care testing devices, which are used to provide a quick blood analysis at/near the patient to get a quick blood analysis result outside of a clinical laboratory to make immediate decisions about patient care. Typically Point-of-Care testing is performed by non-laboratory personnel. A quick foregoing plasma filtration process facilitates the quick blood analysis and enables new operating conditions for Point-of- Care devices, since most of them work with whole blood or with the aforementioned micro devices which lead to a very small yield of plasma/serum volume. The whole SUMMARY OF THE INVENTION

The present invention provides a blood filtering device allowing a quick separation of blood components and an easy handling of the filtering device according to the subject-matter of the independent claims. Further embodiments are incorporated in the dependent claims.

According to an exemplary embodiment of the invention, there is provided a blood filtering device comprising a tubular housing, and a filtration section, wherein the tubular housing has a tubular extension and defines a tubular housing volume, wherein the filtration section comprises a raw side and a clean side being separated by a filter medium, wherein the filtration section being movable along the tubular extension within the tubular housing volume, wherein the filtration section is movably sealed over the tubular housing and separates the tubular housing volume into a variable first tubular housing volume and a variable second tubular housing volume, wherein the filtration section comprises a first communication between the raw side and the first tubular housing volume and a second communication between the raw side and the second tubular housing volume, so that upon movement of the filtration section, blood in the first tubular housing volume flows through the first communication to the raw side, wherein a blood plasma/serum may transit the filter medium and the residual blood flows through the second communication into the variable second tubular housing volume.

Thus, a blood filtering device may be provided, which is easy to handle and compact in volume. In particular, it is possible to simplify the complete process of gaining blood from a patient and to conduct the filtering process, as the above described blood filtering device allows the combination of blood treatment processes. In particular, the device allows to conduct the filtering process by moving the filtration section with respect to the housing, so that when the first tubular housing volume increases, at the same time, the second tubular housing volume decreases, and vice versa. The described blood filtering module allows to gain the blood from the patient, and to conduct the filtering process by the same module, so that a contamination and mistakes with respect to the identification of the blood, especially associated with decanting steps, may be avoided. In particular, it is not necessary to decant the blood after gaining and before filtering, as the filtering module or blood filtering device itself serves for the gaining procedure. In addition, the blood filtering device only requires a minimum number of components, and directly provides the serum or plasma gained by the filtration process.

According to an exemplary embodiment, the filtration section comprises a first separator and a second separator, wherein the first separator is movably sealed over the tubular housing and separates the first tubular housing volume over the clean side, and the second separator is movably sealed over the tubular housing and separates the second tubular housing volume over the clean side.

Thus, the filtration section may be provided which can be moved within the tubular housing, and a clean side may be provided between the first and second separator. In particular, a filter material may be provided between the first and the second separator, so as to provide a raw side of the filter and a clean side of the filter, as well as the separating filter medium between the first separator and the second separator, so that the entire filter arrangement including the first and second separator may be moved as a unit within the tubular housing. According to an exemplary embodiment, the first separator comprises the first communication and the second separator comprises the second communication, wherein the first separator and the second separator are fixedly mounted with respect to each other, and the filter medium extends between the first separator and the second separator.

Thus, the filtration section with the first and second separator and the filter medium in-between may be provided as a geometrically defined arrangement. The first separator and the second separator may be fixed with respect to each other. The fixation may be realized by, for example, a central post, which also may be a structure which may be used for moving the filtration section, like for example a piston rod. Alternatively, the first separator and the second separator may be fixedly mounted with respect to each other by a plurality of rods or structures, in particular, if it is desired to keep the central portion of the filtration section free of stabilizing structures. It should be noted that the filter medium may be a hollow fiber filter medium or a flat filter medium. It should be noted that between the first separator and the second separator, also mounting structures for the filter medium may be provided as well as sealing structures for the filter medium and the respective volumes in order to separate the raw side of the filtration section from the clean side. It should be noted that as an alternative the separators may also be movable with respect to each other, which allows an adaption of the first and second variable volumes and the clean side volume. When the plasma/serum displaces the air on the clean side, the separators may be moved away from each other for compensating the displacement. At the same time the sum of the blood filled first and second variable volume may decrease as the plasma/serum was removed which leads to a reduction of the blood volume on the raw side and the first and second variable volume. In this case the filter medium may be a flexible hollow fibre, preferably helically wound to compensate the length variation.

According to an exemplary embodiment, the first tubular housing volume has a feeding opening for feeding blood to be filtered to the first variable tubular housing volume.

Thus, the blood filtering device may be used for gaining blood from a patient, for example when coupling a needle to the feeding opening, so as to directly deliver the blood from the patient into the first tubular housing volume. This may avoid a decanting process, as the blood is directly delivered from the patient into the blood filtering device.

According to an exemplary embodiment, the feeding opening comprises a luer-lock connector.

Thus, a standardized coupling may be provided, in particular for coupling supply lines to the feeding opening. It should be noted that instead of a luer-lock connector, also a luer-connector may be used as well as a standard cone for coupling a cannula or needle. According to an exemplary embodiment, the feeding opening comprises a one-way valve allowing a flow only in a feeding direction.

Thus, it is possible to avoid a flow-out of the gained blood, in particular when operating the blood filtering device and generating a positive pressure in the first tubular housing volume in order to force the blood to be filtered to the filtration section. Although the opening may also be covered by a plug or cap, a valve provides an automatic closing without further manual action. According to an exemplary embodiment, the blood filtering device further comprises a third separator, wherein the third separator separates the second tubular housing volume over an environment, wherein the third separator is movable along the tubular extension of the tubular housing and is adapted to receive a terminal fixed sealing position with respect to the tubular housing.

Thus, the blood filtering device may be used for gaining the blood directly from the patient, wherein the entire volume within the tubular housing may be increased when gaining the blood, but for the filtration process may be kept in a defined position. In other words, when gaining the blood from the patient, the blood filtering device will be used, and the filtration section moves together with the third separator in a distal direction, in order to increase the entire volume, which entire volume may be defined by the first variable tubular housing volume, the second variable tubular housing volume, and the filtration section. The second tubular housing volume during the gaining process is kept small, as the third separator may directly abut the second separator when gaining the blood, wherein the third separator may be fixed in a distal position, when the gaining process is terminated, so that the filtration section can be moved in the opposite direction, so that the second tubular housing volume increases. When moving the filtration section into the proximal direction, the blood in the first tubular housing section will be forced to the filtering section and the remaining blood components will leave the filtering section to enter the second tubular housing section. When moving the filtration section to the distal direction again, the blood in the second tubular housing volume will be forced to the filtration section and will leave the filtration section to enter the first tubular housing volume, so that the process of filtering, i.e. the movement of the filtration section within the tubular housing may be repeated.

According to an exemplary embodiment, the blood filtering device further comprises a rod extending through and along the tubular housing volume, wherein the rod with a first end is fixed to the filtration section, wherein the third separator has an opening through which a second end of the rod extends, wherein the rod is sealed over and movable through the opening of the third separator, so that the filtration section may be moved within the tubular housing volume by the rod.

Thus, it is possible to operate the filtration section within the tubular housing by the rod extending through the opening of the third separator, so that the second end of the rod may be reached by a user to operate the rod and thus the filtration section. It should be noted that the rod may further extend through the entire filtration section, so as to couple both, the first separator and the second separator to the rod, to provide a stable filtration section geometry in combination with the rod.

According to an exemplary embodiment, the first end is fixed to the second separator of the filtration section, so that the filtration section may be moved within the tubular housing volume by the rod.

According to an exemplary embodiment, the blood filtering device further comprises a resilient element functionally coupled between the rod and the tubular housing, so as to provide a force to move the filtration section in a direction toward the second tubular housing volume.

Thus, for moving the filtration section through and along the tubular housing in both directions, the user has for example to push the rod to move the filtration section into the first direction, i.e. the proximal direction, whereas the movement in the second direction, i.e. the distal direction, will be conducted by the resilient element, so that the user has only to conduct a push operation and the opposite movement is conducted by the resilient element. It should be noted that also a resilient element may be provided so as to support a movement in the opposite direction, so that the user may only conduct a pulling operation, and the opposite movement is conducted by the resilient element.

According to an exemplary embodiment, the rod on the second end comprises a push button, wherein the resilient element is a coiled spring between the push button and third separator.

Thus, the user may use the push button to operate the rod and thus the filtration section to move the filtration section to the proximal direction, wherein the coiled spring will force the rod and thus the filtration section into the distal direction without further action by the user.

According to an exemplary embodiment, the clean side is defined by a volume bounded by the filter medium, a respective inner side of the first separator and the second separator and an inner wall of the tubular housing volume between the first separator and the second separator.

Thus, it is possible to provide an open filtration section, which may be monitored through a transparent housing. In particular, the result of the filtration process may be supervised.

According to an exemplary embodiment, the blood filtering device further comprises a plasma/serum outlet in the side wall of the tubular housing, wherein the plasma/ serum outlet connects to the clean side of the filtration section.

Thus, it is possible to gain the plasma/serum through a defined outlet. In particular when providing a so-called open filtration section, which means that the filtration section is also defined by an inner wall of the tubular housing volume, it is possible to provide the plasma/serum outlet to provide a connection to the filtration section, in particular to the clean side of the filtration section.

According to an exemplary embodiment, the movement of the filtration section is adapted so that the filtration section permanently overlaps the plasma/serum outlet. Thus, it is possible to keep unfiltered blood away from the plasma/serum outlet, so that no contamination of the gained plasma/serum by unfiltered blood can be expected.

According to an exemplary embodiment, the plasma/serum outlet is covered by a piercable septum.

Thus, the clean side of the filtration section, i.e. the section where the plasma/serum is collected, may be hermetically sealed over the environment. However, it should be noted that the piercable septum may be a membrane which is capable of letting pass an overpressure in the clean side, so that an overpressure in the clean side of the filtration section may be avoided. It should be noted that instead of a septum, a collecting volume may be provided, which may be coupled to the plasma/serum outlet in order to collect the plasma/serum. It should be noted that the external volume may be designed so as to collect the plasma/serum during the filtration process. The coupled volume may be decoupled from the blood filtering device to separate the blood filtering device from the external plasma/serum volume. The separate volume for collecting the plasma/serum may be a plunger or syringe arrangement or alternatively may be a blister. It should be noted that the external volume may be designed to be separated from the filtering device in such a way, that the conduit between the filtration section, in particular the clean side of the filtration section, and the separate volume for plasma/serum collection will be automatically closed when separating the external volume from the blood filtering device.

The simple and compact construction of the blood filtering device allows a handshaking of the filter housing for effecting a mixing of the blood sample to keep the suspension well-mixed and the avoid settling of the solid components. Further, when having including pre-treatment components, a stabilizing process may be obtained, for example when mixing the whole blood with heparin. The closed and sealed filtering device can be disposed completely at the end, when the critical materials are treated. No opening of the device is required. When applying a transparent material, a direct observation of the filtration process is possible. It should be noted that the above features may also be combined. The combination of the above features may also lead to synergetic effects, even if not explicitly described in detail. These and other aspects of the invention will be become apparent from and be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described in the following with reference to the following drawings.

Fig. 1 illustrates a blood filtering device according to an exemplary embodiment in a first state before filling in blood to be filtered.

Fig. 2 illustrates the blood filtering device of Fig. 1 in a second condition with blood to be filtered filled in.

Fig. 3 illustrates a cross-sectional view of the blood filtering device according to an exemplary embodiment of the invention.

Fig. 4 illustrates an exemplary embodiment of the blood filtering device before filling in the blood to be filtered.

Fig. 5 illustrates the blood filtering device according to Fig. 4 during a filling process. Fig. 6 illustrates the blood filtering device of Fig. 4 after having conducted the first filtering iteration.

Fig. 7 illustrates an exemplary embodiment of the blood filtering device after the filtering process when extracting the gained plasma/serum.

Fig. 8 illustrates an exemplary embodiment of the blood filtering device and its operation during use.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Fig. 1 illustrates a blood filtering device according to an exemplary embodiment of the invention. The blood filtering device 1 comprises a tubular housing 10, defining a tubular housing volume 1 1 . Within the tubular housing volume 1 1 , there is provided a variable first tubular housing volume 14 and a second variable tubular housing volume 15. Between the first tubular housing volume 14 and the second tubular housing volume 15, there is provided a filtration section 20. The filtration section 20 comprises a first separator 26 for separating the filtration section 20 over the variable first tubular housing volume 14, and a second separator 27 for separating the variable second tubular housing volume 1 5 over the filtration section 20. Between the first separator 26 and the second separator 27, there is provided a filter medium 23, wherein the filter medium separates a clean side 22 from a raw side 21 . Although not illustrated in Fig. 1 , the separator 26 comprises a communication to connect the variable first tubular housing volume 14 with the raw side 21 of the filtration section 20. The separator 27 comprises a communication to connect the variable second tubular housing volume 1 5 with the raw side 21 of the filtration section 20. The blood filtering device 1 is provided with a feeding opening 1 2, wherein to the feeding opening 1 2, for example a needle can be coupled to gain the blood from a patient. The filtration section is coupled to a rod 40 so as to operate and move forward and backward the filtration section 20 within the tubular housing volume 1 1 . There is also provided a third separator 30, which third separator will be described in the following. The blood filtering device 1 further comprises a plasma/serum outlet 16 to extract the gained plasma. The plasma/serum outlet 1 6 is in communication with the clean side 22 of the filtration section 20. It should be noted that the filter housing and the device may be produced of material which may be sterilized. It should be noted that several portions of the filtration device may be coated with heparin, so that the blood condition may be kept sufficient for a filtration process. It should further be noted that the blood filtering device may have clutches or other elements to eliminate an overpressure or a too strong force applied to the respective variable filter volume. It should be noted that instead of a manual operation, also an electric or mechanic operation may be conducted, for example when including the filtering device into an automated drive. It should also be noted that the filtration section or one of the variable blood reservoir volumes or the communications may be used as a reservoir for additives to improve the filtration process.

Fig. 2 illustrates the blood filtering device of Fig. 1 during the filling process, i.e. if the needle is pierced into the skin 2 of a patient to gain the blood. This can be achieved by pulling the rod 40 into the distal direction, so that the filtration section 20 will be moved into the distal direction. The negative pressure in the variable first tubular housing volume 14 will suck the blood through the needle and the feeding opening 1 2 into the variable first tubular housing volume 14. It should be noted that in the feeding opening 1 2, there may be provided a check valve 1 3 to avoid exit of the gained blood 3, in particular when applying a positive pressure to the variable first tubular housing volume 14. When the intended amount of blood 3 is gained into the variable first tubular housing volume 14, the filtration section 20 arrives at a maxi mum distal direction, as well as the abutting third separator 30. The third separator 30 will now snap into a fixation, so as to define the variable second tubular housing volume 1 5 between the second separator 27 and the third separator 30. Now, the blood filtering device 1 may be removed from the skin 2 and the filtration section 20 may be moved into the opposite, i.e. proximal direction by pushing the rod 40. Now, the blood 3 will be forced through the communications in the first separator 26 to the raw side of the filtration section 20, so that the plasma/serum may transit the filter medium and the remaining blood may exit the raw side through the communications in the second separator 27 to enter the variable second tubular housing volume 1 5. This will be described in further detail in the following.

Fig. 3 illustrates a cross-sectional view of the blood filtering device. The blood filtering device 1 comprises the tubular housing 1 0, defining the tubular housing volume 1 1 . Within the tubular housing volume 1 1 , there is provided the variable first tubular housing volume 14, the variable second tubular housing volume 1 5, and the filtration section 20. The filtration section 20 may be moved alternately from the proxi mal end to the distal end, and vice versa. The movement of the filtration section 20 may be conducted by the rod 40, which rod 40 may be connected to the filtration section 20, at its first end 41 . At the second end 42 of the rod 40, there may be provided a push button 43 for operating the blood filtering device by a user. When pulling the filtration section 20 the first time, the third separator 30, abutting the second separator 27, will be moved to the distal direction and will snap into a fixed position in order to remain in this position, even if the filtration section 20 is moved back into the proximal direction. The filtration section 20 comprises the first separator 26 and the second separator 27. Between the first and the second separator, there is provided a filter medium 23, which may be provided in form of a hollow fiber. It should be noted that also any other filter material may be used, e.g. a flat sheet medium. The filter medium 23 separates the volume between the first separator and the second separator 26, 27 into a raw side 21 and a clean side 22. The raw side 21 , here within the hollow fiber, is in communication with the variable first tubular housing volume 14 and the variable second tubular housing volume 15. For this purpose, in the first separator 26 there is provided a first communication arrangement 24, and in the second separator 27 there is provided a second communication arrangement 25. These communications 24 and 25 connect the variable first tubular housing volume 14 with the raw side 21 of filtration section, as well as the variable second tubular housing volume 15 with the raw side 21 . When moving the filtration section 20 within the tubular housing volume 1 1 , the variable second tubular housing volume 15 successively decreases and increases the pressure, so that blood within the second tubular housing volume 15 is forced into the communication 25 so as to arrive at the raw side 21 . Owing to the pressure, the blood within the raw side 21 will be separated into the serum/plasma transiting the filter medium so as to arrive at the clean side 22, wherein the remaining blood exits the filtration section through the first communication 24 in the first separator 26 to arrive at the first tubular housing volume 14. When the filtration section 20 arrives at the maximum distal position, the process will be reverted so that the blood in the variable first tubular housing volume 14 again enters the raw side 21 . The blood will be filtered and the remaining blood will exit the filtration section through the second communication 25 in the second separator 27, so as to arrive at the second tubular housing volume again, until the filtra- tion section 20 has arrived at the maximum proximal position. To extract the gained plasma/serum from the clean side 22 of the filtration section 20, the serum/plasma may exit the blood filtering device through the plasma/serum outlet 16, being provided in the wall of the housing, which plasma/serum outlet 16 may be covered by piercable septum 18. It should be noted that the filtration section may be kept open, this means that no additional wall may be provided between the first and second separators 26, 27, so that a direct communication between the clean side 22 and the plasma/serum outlet 16 is possible. This means, that the clean side 22 is defined by the inner walls of the separators 26, 27, the filter material or filter medium 23, and the inner wall 17 of the housing 10.

Fig. 4 illustrates the blood filtering device in a first situation, where no blood is within the filtering device. In this situation, the filtration section 20 is in the proximal position, and the third separator 30 abuts the second separator. Fig. 4 additionally illustrates a resilient element, here in form of a spring 45, so that during operation the user has only to conduct a push movement, wherein the opposite moving will be conducted by the resilient member. The blood filtering device will now be pierced with a needle into the skin 2 of the patient, as described in Fig. 5. The needle may not be part of the blood filtering device as such and may be separable. Now, the user may pull the rod 40 by the push button 43 so as to pull the filtration section 20 from the proximal position into the distal position, so that blood enters the first tubular housing volume 14. When the maxi mum amount of blood 3 has entered the first tubular housing volume 14, the filtration section 20 is in the maxi mum distal position, and the third se- parator 30 clicks into a fixed position. Now, the blood filtering device may be removed from the patient, as will be described with respect to Fig. 6. When having removed the device from the patient, which however is not mandatory, but will easy the handling, the user may push the rod 40 by means of the push button 43, so that the filtration section 20 will be pushed into the proxi mal direction. The blood 3 from the first volume 14 will be forced into the filtration section 20 and the remaining blood will exit into the second tubular housing volume 1 5. It should be noted that the third separator 30 remains in the fixed position, so that the second tubular housing volume 1 5 now is increased by pushing the filtration section back into the proximal direction, and at the same ti me the first tubular housing volume 14 is decreased. When the user now releases the push button 43, the resilient member in form of a spring 45 will push back the push button 43, so that the filtration section 20 will again move into the distal direction and force the blood through the filtration section from the second tubular housing volume into the first tubular housing volume. This process of cross-flow filtration can be repeated according to need, until a sufficient amount of plasma/ serum is collected in the clean side 22 of the filtration section 20, and can be extracted from the plasma/serum outlet opening 1 6. A check valve 1 3 may avoid unintended exit of blood 3 out of the variable first tubular housing volume 14. It should be noted that also a different closing mechanism may be used, for example a permanent closing when removing for example the needle from the blood filtering device.

Fig. 7 now illustrates the process of extracting the plasma. When having terminated the entire filtering process by repeated movement of the filtration section 20 within the tubular housing volume 1 1 , the gained plasma in the clean side 22 of the filtration section 20 may be extracted by way of a plasma/serum reservoir or a syringe or a container 53. It should be noted that the plasma/serum reservoir, or syringe or in general container may be implemented into the blood filtering device, so that the piercable septum may be avoided, however, in this case it seems to be reasonable to provide a connection which reliably closes the openings when removing the plasma/ serum reservoir 53 from the blood filtering device.

For the filtering process, the needle 51 may be removed and the opening may be closed by a cap 52, as can be seen in Fig. 8.

Fig. 8 also illustrates the handling by a user, so that a user can push and pull the rod 40 to operate the filtering process. It should be noted that also a collar 46 may be provided, which may easy the process of pushing when the user pushes the push button 43.

It should be noted that the term "comprising" does not exclude other elements or steps, and that the indefinite article "a" or "an" does not exclude a plurality. Also elements described in association with the different embodiments may be combined. It should be noted that the reference signs in the claims shall not be construed as limiting the scope of the claims.