Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1998-07-31
2001-12-18
Kim, John (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S650000, C210S739000, C210S929000
Reexamination Certificate
active
06331252
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to hemodialysis (artificial kidney) apparatus and related methods. More specifically, the invention pertains to such apparatus and methods as used for controlling ultrafiltration of fluid from a patient.
BACKGROUND OF THE INVENTION
Practical hemodialysis made its debut in the early 1960s with the essentially simultaneous advent of hemodialysis apparatus capable of producing dialysate on line and of hemodialyzers exhibiting an acceptable reliability. Since then, great developments have occurred in hemodialyzers and in hemodialysis apparatus.
Nephrology clinicians have long appreciated the need for hemodialysis to remove not only toxic metabolic solutes from the blood but also excess fluid. Removal of fluid across the semipermeable hemodialysis membrane is termed “ultrafiltration”.
The ongoing development of improved hemodialysis membranes has been driven in part by the clinical need to perform ultrafiltration (along with hemodialysis) of a patient in a manner that alleviates patient morbidity as much as possible. With respect to ongoing improvements in hemodialysis membranes, the general trend has been to produce membranes having increased “flux” by which is meant water permeability. Such membranes achieve a more rapid ultrafiltration of water from the blood at a lower transmembrane pressure (TMP). The overarching requirements of safety and well-being for the patient being treated with such membranes have driven the development of hemodialysis apparatus that provide excellent control of ultrafiltration. Such development has been the subject of intensive research by individuals and corporate entities working in the hemodialysis field.
A notable example of a hemodialysis apparatus that provides control of ultrafiltration is disclosed in U.S. Pat. No. 5,247,434 to Peterson et al., which is incorporated herein by reference.
Another trend in hemodialysis has been various approaches to achieving more rapid dialysis (with ultrafiltration) without adversely affecting patient morbidity. According to some approaches, this is achieved by, inter alia, passing dialysate through the hemodialyzer at a higher flow rate than conventionally. In this regard, the conventional dialysate flow rate is 500 mL/min, and some modern dialysis apparatus can achieve a dialysate flow rate of about 1000 mL/min. However, some clinicians perceive a need for dialysate flow rates of 3000-4000 mL/min.
Such increased dialysate flow rates impose a need to achieve greater ultrafiltration rates than conventionally. For example, whereas conventional dialysis apparatus typically achieve an ultrafiltration rate up to about 4000 mL/hr, some clinicians perceive a need for ultrafiltration rates of up to 10 L/hr.
Despite great advances in the art of clinical ultrafiltration, especially ultrafiltration performed during a hemodialysis treatment, conventional apparatus are limited in their ability to satisfy the needs summarized above.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, hemodialysis apparatus are provided that prepare fresh dialysate and deliver the dialysate from a mix chamber to a hemodialyzer and return spent dialysate from the hemodialyzer to a drain. A preferred embodiment of such an apparatus comprises, in hydraulic order, a first positive-displacement pump, a first flowmeter, a second flowmeter, and a second positive displacement pump. The first positive-displacement pump has an inlet hydraulically connected to the mix chamber. The first flowmeter has an inlet hydraulically connected to an outlet of the first pump and an outlet hydraulically connectable to a dialysate inlet of a hemodialyzer. The first flowmeter produces a respective output having a characteristic that is a function of a volumetric pumping rate of the first pump. The second flowmeter has an inlet hydraulically connectable to a dialysate outlet of the hemodialyzer. The second positive-displacement pump has an inlet hydraulically connected to an outlet of the second flowmeter and an outlet hydraulically connected to a drain. The second flowmeter produces a respective output having a characteristic that is a function of a volumetric pumping rate of the second pump. The first and second pumps define therebetween a UF loop, wherein a difference in the volumetric pumping rate of the second pump relative to the volumetric pumping rate of the first pump generates a volumetric condition in the UF loop that urges a net ultrafiltration of fluid across a semipermeable membrane in the hemodialyzer. Preferably, the first and second pumps are gear pumps.
The respective outputs of the first and second flowmeters preferably comprise respective electrical signals. The electrical signals preferably exhibit a respective characteristic from which a difference in the respective signals can be determined, wherein the difference can be used to govern the relative pumping rates of the first and second pumps. To such end, the first and second pumps as well as the first and second flowmeters can be electrically connected to a suitable processor or computer that performs such determinations and provides feedback control signals to the first and second pumps so as to achieve, for example, a desired rate of ultrafiltrate removal from a blood compartment to a dialysate compartment of the hemodialyzer, or (if desired) a “zero-UF” operating condition resulting in zero net flow of liquid from the blood compartment to the dialysate compartment or from the dialysate compartment to the blood compartment.
With respect to achieving ultrafiltration from the blood compartment to the dialysate compartment, the volumetric pumping rate of the second pump is set greater than the volumetric pumping rate of the first pump. The resulting volumetric imbalance of dialysate entering the dialysate compartment versus dialysate exiting the dialysate compartment results in a net ultrafiltration of liquid from the blood compartment to the dialysate compartment.
A “reverse ultrafiltration” condition can be achieved by operating the first pump to have a volumetric pumping rate that is greater than the volumetric pumping rate of the second pump. The resulting volumetric imbalance causes a net ultrafiltration of liquid from the dialysate compartment to the blood compartment.
According to another aspect of the invention, methods are provided for performing ultrafiltration of a liquid passing through the blood compartment of a hemodialyzer. According to a preferred embodiment of such a method, a dialysate solution is provided. While passing the liquid through the blood compartment of the dialyzer, the dialysate solution is conducted through a first positive displacement pump, then through a first flowmeter, then to a dialysate inlet of a dialysate compartment of the hemodialyzer. The first pump delivers the dialysate to the dialysate inlet at a first volumetric pumping rate as measured by the first flowmeter. After passing the dialysate through the dialysate compartment, the dialysate is conducted from an outlet of the dialysate compartment through a second flowmeter, then through a second positive displacement pump. The second pump pumps the dialysate at a second volumetric pumping rate, as measured by the second flowmeter, that is greater than the pumping rate of the first pump. The resulting volumetric imbalance urges an ultrafiltrate liquid to pass from the blood compartment to the dialysate compartment.
To provide the dialysate, a dialysate concentrate can be added to a water stream at a proportioning ratio that is a function of the volumetric pumping rate of the first pump as measured by the first flowmeter.
According to another aspect of the invention, methods are provided for priming a blood compartment of a hemodialyzer. According to a preferred embodiment of such a method, first a liquid is provided. The liquid is conducted through a first positive displacement pump, then through a first flowmeter, then to a dialysate inlet of a dialysate compartment of the hemodialyzer. The first pump delivers the liquid to the dia
Casterline Cameron Scott
El Sayyid Waleed Mutasem
Barrett Robert M.
Baxter International Inc.
Kelly Paula J.
Kim John
Mattenson Charles R.
LandOfFree
Methods for priming a blood compartment of a hemodialyzer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for priming a blood compartment of a hemodialyzer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for priming a blood compartment of a hemodialyzer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2566619