Abstract:
Device for haemodiafiltration, which comprises a first circuit for a dialysis solution and a second circuit for blood, so that the toxic substances from the blood flow pass into the dialysis liquid within a haemofilter ( 11 ), a liquid pump ( 20 ) located upstream of the haemofilter ( 11 ) in the first dialysis liquid circuit, is adapted for injecting replacement liquid into the dialysis solution flow after a blood pump ( 15 ) finishes pumping blood to the interior of the haemofilter ( 11 ).

Description:
PURPOSE OF THE INVENTION 
       [0001]    This invention refers to a method and device for performing haemodiafiltration, which is a renal dialysis method that combines haemodialysis and haemofiltration, in order to achieve a high removal of substances with a high and low molecular weight. 
       STATUS OF THE TECHNIQUE 
       [0002]    From patent EP0516152B1, a device is known for performing haemodiafiltration, namely, an extra-renal purification technique that combines two mechanisms: dialysis or diffusion and ultrafiltration or convection. 
         [0003]    The aforementioned device comprises two circuits; a dialysis liquid is connected to a first circuit through the external chamber of a haemofilter against the direction of the blood flow, which is connected to a second circuit to maximize the difference in concentration of the substances that one wishes to remove, in all areas of the filter. 
         [0004]    Therefore, a dialysis liquid is infused into the haemofilter against the flow, which will be removed with the ultra-filtering. 
         [0005]    Consequently, a path of solutes with low molecular weight takes place from the blood to the dialysis liquid due to the difference in concentration, in addition to a high clearance of water and solutes by the pressure gradient. In other words, it filters blood, extracts liquid from the internal media, dialyses and purifies solutes from the body. 
         [0006]    The first circuit of the dialysis solution is regulated by a set of pumps located upstream and downstream of the haemofilter, respectively. 
         [0007]    Analogously, the second circuit of the blood is also regulated by a set of pumps located upstream and downstream of the haemofilter, respectively. 
         [0008]    The replacement liquid can be infused in the arterial line, upstream of the haemofilter, pre-dilution, and in the vein line that exits from the haemofilter, post-dilution. 
         [0009]    Generally, the method most used is post-dilution. However, this method has some disadvantages, such as the blood in the haemofilter becoming very concentrated when a high amount of liquid is extracted. 
         [0010]    A consequence of the above is that the performance of ultra-filtering decreases and an increase occurs in the resistance to the path of the blood flow, which may lead to a poor flow and the clotting of the second blood circuit; since the rate of haemofiltration rises, the blood becomes concentrated in the haemofilter, its viscosity increases and the hydraulic resistance and risk of clotting of the same increases. 
         [0011]    A consequence of the above is that the service life of the haemofilter is reduced. 
       CHARACTERIZATION OF THE INVENTION 
       [0012]    This invention seeks to resolve and reduce one or more of the problems stated above, through a haemodiafiltration device as is claimed in claim  1 . Embodiments of the invention are established in the subsequent claims. 
         [0013]    A purpose of this invention is to extend the service life of the haemofilter and avoid the decreased performance of the same during its effective lifetime. 
         [0014]    Another purpose of this invention is to decrease the risk of blood clotting in the second blood circuit of the haemodiafiltration device. 
         [0015]    Yet another purpose of this invention is to decrease the risk of obstruction of the filtering media, the semipermeable membrane, which separates the two flows that enter and leave the haemofilter. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0016]    Now the devices that make up the invention will be described, as an example only, referring to the attached drawings, in which: 
           [0017]      FIG. 1  shows in a flow chart a haemodiafiltration device according to the invention, 
           [0018]      FIG. 2  shows when a blood pump of the haemodiafiltration device is empty according to the invention, 
           [0019]      FIG. 3  shows when a liquid pump of the haemodiafiltration device injects the fill liquid into the dialysis liquid circuit according to the invention, and 
           [0020]      FIG. 4  shows the blood pump of the haemodiafiltration device full according to the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0021]    In reference to  FIG. 1 , below there is a flow chart schematically illustrated of a device used to perform haemodiafiltration, which comprises a first circuit of the dialysis solution regulated by the action of a first set of valves  18 ,  19 ,  21  and a pump  20  just like a syringe tube pump  20 , which is located upstream of the first dialysis circuit, i.e. before a haemofilter  11 . 
         [0022]    A second regulated blood circuit, also regulated by the action of a second set of valves  14 ,  16 ,  17  and a pump  15 , just like a tube pump  15 , which is located on the upstream side, i.e. the arterial side of the second blood circuit before the haemofilter  11 . 
         [0023]    Both the first and second circuit come into contact at the haemofilter  11 , which comprises a semipermeable membrane. 
         [0024]    As has been mentioned previously, each circuit comprises at least three valves  18 ,  19 ,  21 ,  14 ,  16  and  17 , respectively, distributed upstream and downstream of haemofilter  11 . 
         [0025]    Replacement liquid is injected through syringe pump  20 , the reinfusion process, of a solution that can be similar to the dialysis solution in the blood through haemofilter  11  to re-establish to its original volume. 
         [0026]    To carry out reinfusion, the pulsating characteristics of the tubular pump  15  are used, which cause the trans-membrane pressure in the membrane of haemofilter  11  during haemofiltration to not be constant, and may become quite absent at any moment. 
         [0027]    The aforementioned pressure is highest during the systole of blood pump  15  and practically zero during the diastole of the same. 
         [0028]    By taking advantage of this circumstance, one can carry out the reinfusion process of the replacement liquid by using the pressure gradient that is generated in the very membrane of the haemofilter. In other words, during this time period, the flow through the same is inverted, and if in this time period the reinfusion liquid is added to the dialysis solution, said reinfusion liquid passes into the blood flow, since the flow through the membrane is inverted, i.e. a liquid path from the dialysis solution to the blood flow takes place. 
         [0029]    Based on  FIGS. 1 to 4 , we can explain the replacement liquid path process to the blood flow through the haemofilter  11  membrane. 
         [0030]    The starting situation is when the blood pump  15  is completely full, the second outlet valve  16  is open and the third blood stop valve  17  after haemofilter  11  is closed. 
         [0031]    Simultaneously, the liquid perfusion pump  20  is completely empty and the second outlet valve  19  is closed, with the first replacement liquid stop valve  21  being open. 
         [0032]    Under these conditions, the impulse of the blood pump  15  takes place. The volume moved by the aforementioned pump  15  enters the blood chamber of haemofilter  11  and an equivalent volume of plasma seeps through the membrane of the same and exits the liquid outlet of the haemofilter through the third valve  18 . 
         [0033]    This plasma outlet causes the blood contained in haemofilter  11  to become concentrated as a function of the relationship that exists between the ejection volume of blood pump  15  and the blood chamber volume of haemofilter  11 . See  FIG. 2 . 
         [0034]    During the impulse process of blood pump  15 , the replacement liquid pump  20  has been filled with replacement liquid. 
         [0035]    At that time, the blood inlet valve  16  and outlet valve  17  of the filter are closed and the replacement liquid inlet valve  19  and outlet valve  18  of the haemofilter are open, with the impulse of liquid pump  20  starting, which at this first moment is used to wash the dirty liquid that was just filtered. See  FIG. 3 . 
         [0036]    Once a pre-determined volume of liquid has passed from the scheduled wash, the third replacement liquid outlet valve  18  is closed and the third blood outlet valve  17  of the haemofilter opens. 
         [0037]    The remaining volume of liquid moved by liquid pump  20 , upon finding itself with the closed first liquid stop valve  21  and the third replacement liquid outlet valve  18 , seeps towards the blood flow through the membrane in the reverse direction. 
         [0038]    If the volume that is injected with liquid pump  20  is substantially similar to the volume of plasma that has been previously ultra-filtered, the blood will recover its original haematocrit within the same haemofilter  11  and at the same time, an equivalent volume of blood will be replaced for the patient. See  FIG. 4 . 
         [0039]    Some advantages of the system are that the blood does not increase its haematocrit within the capillary of haemofilter  11 , and therefore the hydraulic resistance of the same is lower. 
         [0040]    As the haematocrit does not increase in the capillary of the haemofilter  11  membrane, the risk of clotting is minimized. 
         [0041]    Filtration at the haemofilter  11  membrane is done in the direction of the blood flow towards the dialysis liquid and vice versa, i.e. in both directions of the membrane, whereby it hinders the depositing of platelets and erythrocytes in the pores of the capillary, and therefore the obstruction of the same. 
         [0042]    In this device, the direction of filtration at the membrane is inverted in each cycle, with which the depositing of cells is reduced, as is the obstruction of the membrane pores. 
         [0043]    The coordinated operation of both pumps  15 ,  20  and of the six valves  15  to  19  and  21  is controlled and regulated by a control unit that receives information from a set of receivers distributed over pumps  15 ,  20  and the six valves  15  to  19  and  21 . 
         [0044]    Said control unit is adapted to perform a variation calculated at the flow of each of the pumps  15  and  20  respectively, in such a way that it allows the opening and closing time of each of the valves to be regulated so that the liquid added to the dialysis solution passes into the blood flow. 
         [0045]    The embodiments and examples stated in this report are presented as the best explanation of this invention and its practical application, and thus allow the experts in the technique to put into practice and utilise the invention. However, the experts in the technique will recognise that the description and the above examples have been presented for the purpose of illustration and as an example only. The description as explained is not intended to be exhaustive or to limit the invention to the exact described form. Many modifications and variations are possible in light of the above instruction without going beyond the intent and scope of the following claims.