Apparatus and method for controlling ultrafiltration during hemodialysis

• US 4,715,959 A
• Filed: 05/03/1984
• Issued: 12/29/1987
• Est. Priority Date: 08/31/1982
• Status: Expired due to Fees

• Current Assignee: CD Medical Incorporated (Baxter International Inc.)
• Original Assignee: CD Medical Incorporated (Baxter International Inc.)
• Inventors: Burton, Richard J., Allan, Jonathan M., Jurock, Volker
• Primary Examiner(s): SPEAR JR, FRANK
• Application Number:
  US06/606,505
• Time in Patent Office: 1,335 Days
• Field of Search: 210/646, 210/87, 210/321.3, 210/929, 210/637
• US Class Current: 210/637
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/1605 Physical characteristics of the dialysate fluid
• CPC Class Codes: A61M 1/1641 linked by pistons
• CPC Class Codes: A61M 1/1662 with heat exchange between fresh and used dialysate
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/3344 Measuring or controlling pressure at the body treatment site
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: Y10S 210/929 Hemoultrafiltrate volume measurement or control processes

Abstract

Hemodialysis ultrafiltration apparatus comprises a dialyzer. A closed circuit is provided for supplying fresh dialysate to and for removing spent dialysate from the dialyzer. Blood is supplied to and removed from the dialyzer. The closed circuit for supplying fresh dialysate and removing spent dialysate is apportioned into below mean dialyzer blood pressure and above atmospheric pressure sections, with the dialyzer being positioned in the below mean dialyzer blood pressure section. A mechanism is provided for controlling the pressure of fresh dialysate introduced into the below mean dialyzer blood pressure section to substantially match the pressure on the dialysate side of the dialyzer. A mechanism is provided for controlling the above atmospheric pressure portion of the spent dialysate circuit. A pump removes spent dialysate of equivalent ultrafiltrate volume from the closed circuit to control the rate of ultrafiltrate removal from blood in the dialyzer, thus affecting the pressure on the dialysate side of the dialyzer required to sustain that rate.

A method of hemodialytic ultrafiltration is carried out substantially in accordance with the above-described apparatus.

Claims

1. Hemodialysis ultrafiltration apparatus comprising:

hemodialysis means having a dialysate side including an input and an output;

a source of fresh dialysate fluid;

first positive displacement means for supplying fresh dialysate fluid from the source of fresh dialysate fluid to the input of the hemodialysis means;

second positive displacement means for removing spent dialysate fluid from the output of the hemodialysis means to a dialyzer output circuit;

ultrafiltration means for removing additional spent dialysate at a controlled rate from the output of the hemodialysis means to the dialyzer output circuit so as to effect removal of ultrafiltrate from blood in the hemodialysis means; and

means for minimizing transients in dialysate pressure within the hemodialysis means caused by operation of the first positive displacement means and for reducing ultrafiltration error caused by system compliance, said means including pressure reducing and regulating means disposed between the source of fresh dialysate and the first positive displacement means for reducing the pressure of the fresh dialysate entering the first positive displacement means to below atmospheric pressure and for regulating the pressure of said fresh dialysate entering the first positive displacement means to substantially match the pressure on the dialysate side of the hemodialysis means.

2. The apparatus of claim 1 which further comprises pressure increasing means disposed between the output of the hemodialysis means and the second positive displacement means for increasing the pressure of the spent dialysate fluid entering the second positive displacement means, whereby the hemodialysis means is further isolated from dialysate pressure transients caused by operation of the positive displacement means, with a consequent further reduction in ultrafiltration error caused by system compliance.

3. A method of hemodialytic ultrafiltration using a semipermeable membrane device having a blood chamber and a dialysate chamber that minimizes pressure transients in the dialysate chamber of the semipermeable membrane device and thereby reduces ultrafiltration error caused by system compliance comprising the steps:

providing fresh dialysate fluid;

reducing and regulating the pressure of said fresh dialysate fluid to substantially match the pressure in the dialysate chamber of the semipermeable membrane device;

introducing said reduced pressure fluid to an input of a first positive displacement device;

conveying said reduced pressure fluid from an output of the positive displacement device to the input of the semipermeable membrane device;

withdrawing said reduced pressure fluid from an output of the semipermeable membrane device;

increasing the pressure of said withdrawn fluid; and

introducing said increased pressure withdrawn fluid to an input of a second positive displacement device and to an input of an ultrafiltrate withdrawal device.