Apparatus and method for controlling ultrafiltration during hemodialysis

An apparatus for controlling ultrafiltration during hemodialysis having below mean dialyzer blood pressure and above atmospheric pressure sections, said below mean dialyzer blood pressure section comprising:

• a fresh dialysate supply line and a first portion of a spent dialysate removal line;
• a pair of matched positive displacement units each including valves and interrelated switching means, the first of said units being interconnected to said supply line by a mix point and pressure reducing means;
• and
• a hemodialyzer for the dialysis and ultrafiltration of blood including inlet and outlet blood ports, an inlet dialysate port for the entry of fresh dialysate and an outlet dialysate port for the exit of spent dialysate;
• said above atmospheric pressure section comprising:
• a second portion of the spent dialysate removal line interconnected to said first portion of said spent dialysate removal line by pressure increasing means;
• the second of said positive displacement units being in fluid communication with the second portion of said spent dialysate removal line;
• a dialysate drain line in fluid communication with the second portion of said dialysate removal line;
• and
• ultrafiltrate removal means connected between the second portion of said spent dialysate line and said drain line adapted to withdraw dialysate from said removal line and transfer same to said drain line;
• said valves and switching means adapted to cause concurrently one of said units to fill with fresh dialysate as fresh dialysate is supplied to said dialyzer while the other unit fills with spent dialysate as spent dialysate is drained and to alternate functions after said valves are reversed.