Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
1999-07-08
2001-08-28
Kim, John (Department: 1723)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S085000, C210S087000, C210S090000, C210S096200, C210S097000, C210S103000, C210S137000, C210S143000, C210S321690, C210S321720, C210S410000, C210S646000, C073S040000
Reexamination Certificate
active
06280632
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for producing a substitution fluid for use during hemodiafiltration or hemofiltration in a hemodialysis machine or for use as filling and rinsing fluid during preparation of a hemodialysis machine.
BACKGROUND OF THE INVENTION
A hemodialysis treatment is used for treating patients who have acute or chronic renal insufficiency. Blood is taken from the patient in an extracorporeal blood circuit and passes through a dialyser which removes uremic toxins in the blood and reconstitutes the blood by balancing electrolytes, such as sodium, potassium, calcium and magnesium, and adding necessary substances, such as bicarbonate. Moreover, a certain amount of fluid is removed from the blood , called ultrafiltrate, since the patient cannot expel superfluous fluids in the normal manner. Hemodialysis primarily uses diffusion through a semipermeable membrane in order to perform this treatment.
Another treatment procedure which has been used more often recently is hemofiltration, whereby the blood is filtered in a hemofilter and the filtrate is discarded. Substitution fluid is then added, either before or after the filtration, for replacing the discarded ultrafiltration fluid. Hemofiltration primarily uses convection for removing the uremic toxins, and the substitution fluid comprises the necessary electrolytes for balancing and fluid addition purpose. A smaller amount of substitution fluid is added compared to the amount of ultrafiltrate fluid which is removed, in order to remove the necessary amount of fluid from the patient.
Another treatment procedure utilized is a combination of hemodialysis and hemofiltration, and is called hemodiafiltration. This procedure is essentially a combination of these two treatment procedures, and uses a hemodiafilter.
These treatment methods are described in numerous text books and it is not necessary to describe them in more detail in the present specification. One description is in the chapter: “Hemodialysis Machines and Monitors” by Polaschegg H D, Levin N W in “Replacement of renal function by dialysis”, by Jacobs C, Kjellstrand C M, Koch K M, Winchester J F, 4th ed. Kluwer academic publishers, 1996:333-79.
The above-mentioned substitution fluid can be prepared as a pharmaceutical solution. However, doing so is expensive. Therefore, it is preferred to produce the substitution solution on-line in connection with the dialysis machine, by filtration of the dialysis fluid. However, a preparation method must be devised and adapted for preparing a substitution fluid that is sterile and can be used for infusion purpose.
Thus, a dialysis machine which is adapted for hemofiltration and hemodiafiltration also includes a device for preparing the substitution fluid on-line. This device usually comprises two filters for producing the substitution fluid and for securing the sterility of the prepared fluid.
Some patent specifications describing devices of interest for accomplishing these goals are U.S. Pat. No. 4,209,391, assigned to Cordis Dow; European Patent No. 189,561, assigned to Fresenius; German Patent No. 3,448,262, assigned to Fresenius; U.S. Pat. No. 4,834,888, assigned to Fresenius; European Patent No. 407,737, assigned to Fresenius; German Patent No. 4,240,681, assigned to Fresenius; European Patent No. 692,268, assigned to Fresenius; European Patent No. 165,519, assigned to Gambro; European Patent No. 694,312, assigned to Hospal; and European Patent No. 745,213, assigned to Gambro.
Previous dialysis machines for producing on-line substitution solutions comprise a peristaltic pump arranged upstream of the dialysis machine for propelling the substitution fluid. A peristaltic pump comprises several rollers interacting with a plastic tube pump segment and occluding the pump segment. By moving the roller along the tube while occluding the tube, the fluid is pumped. The substitution fluid flow rate is thus approximately proportional to the rotational speed of the peristaltic pump.
The peristaltic pump is used since it can easily be placed on the front of the machine, and because it cooperates with a tube portion that can be produced as a sterile article. However, the tube portion so utilized has a limited life time. Thus, the pump segment and the second filter must be replaced, for example after one month, which creates comparatively high costs. Also, the peristaltic pump involves added costs, and uses a relatively large additional space on the front of the machine. The peristaltic pump is thus placed on the front since the pump segment must be replaced regularly. All this makes preparation for the treatment complicated.
If the peristaltic pump is used with a disposable tube system and a disposable second filter, the disposable tube system must comprise a pump segment and the second filter. Thus, such a disposable tube system is comparatively expensive and bulky.
The object of the present invention is therefore to provide a method and apparatus which obviates the drawbacks of the prior art dialysis machines.
Another object of the present invention is to provide a dialysis machine for producing substitution fluid on-line, in which the peristaltic pump previously used is dispensed with.
SUMMARY OF THE INVENTION
In accordance with the present invention, these and other objects have now been realized by the invention of apparatus for providing a sterile substitution solution from a dialysis fluid used in connection with the treatment of a patient's blood in an extracorporeal circuit, the apparatus comprising balancing means for comparing a flow of fresh dialysis fluid prior to the treatment of the patient's blood and a flow of spent dialysis fluid after the treatment of the patient's blood, a fresh dialysis circuit for handling the fresh dialysis fluid, a throttle dividing the fresh dialysis circuit into a positive pressure portion and a negative pressure portion, at least one sterile filter including a membrane in the fresh dialysis circuit, the at least one sterile filter being disposed in the positive pressure portion of the fresh dialysis circuit, pressure control means for controlling the pressure in the positive pressure portion in order to pass a predetermined amount of the fresh dialysis fluid through the membrane in the at least one sterile filter in order to provide a predetermined amount of the sterile substitution solution for addition to the extracorporeal circuit. In a preferred embodiment, the apparatus includes a dialyser for treatment of the patient's blood. Preferably, the dialyser is a hemodialysis device, a hemofiltration device or a hemodiafiltration device.
In accordance with one embodiment of the apparatus of the present invention, the fresh dialysis circuit comprises a first conduit disposed between the balancing means and the dialyser, the throttle being disposed in the first conduit, and the apparatus including a second conduit connected to the first circuit at a predetermined location between the balancing means and the throttle, the at least one sterile filter being disposed in the second conduit, and the second conduit being connected to the extracorporeal circuit. In a preferred embodiment, the dialyser is a hemodialysis device, a hemofiltration device or a hemodiafiltration device.
In accordance with a preferred embodiment of the apparatus of the present invention, the apparatus includes a flow meter associated with the first conduit between the predetermined location and the dialyser for measuring the flow of the fresh dialysis fluid to the dialyser, whereby the throttle can be controlled by measurement of the flow by the flow meter and a predetermined flow of the sterile substitution solution can be obtained in the second conduit, the predetermined flow comprising the difference between the flow of the fresh dialysis fluid obtained by the balancing means and the flow of the fresh dialysis fluid through the throttle. Preferably, the throttle comprises an adjustable throttle valve, and adjustable three-way valve, a constant pressure valve,
Gambro Lundia AB
Kim John
Lerner David Littenberg Krumholz & Mentlik LLP
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