Extracorporeal blood treatment apparatus and method

A dialyzer comprising:

• (a) a casing;
• (b) a bundle of hollow-fiber semipermeable membranes disposed in the casing, each hollow-fiber membrane having a lumen;
• (c) a first inlet and a first outlet attached to the casing, the first inlet and outlet being connected to the fibers so as to conduct a first liquid in parallel through the lumina of the hollow-fiber membranes from the first inlet to the first outlet;
• (d) a second inlet and a second outlet attached to the casing so as to conduct a second liquid though the casing from the second inlet to the second outlet, the second liquid exhibiting a pressure profile on the membranes during conduction of the second liquid from the second inlet to the second outlet;
• and
• (e) flow-restricting means situated between the second inlet and the second outlet for imparting a restriction to flow of the second liquid through the casing sufficiently to cause the pressure profile to be non-linear from the second inlet to the second outlet.

A dialyzer comprising:

• (a) a casing defining a dialyzer volume, and including a partition dividing the dialyzer volume into first and second portions, the partition defining at least one opening allowing liquid to flow therethrough from the first portion to the second portion;
• (b) first and second groups of hollow-fiber semipermeable membranes, the first group extending through the first portion and the second group extending through the second portion, each of the fibers of each said group having a lumen;
• (c) a blood inlet and a blood outlet attached to the casing so as to conduct extracorporeal blood from the blood inlet to the blood outlet through the lumina of the fibers of the first and second group;
• (d) a dialysate inlet and a dialysate outlet attached to the casing so as to conduct dialysate from the dialysate inlet to the first portion, through the opening to the second portion, then to the dialysate outlet, the dialysate exhibiting a pressure profile on the membranes as the dialysate is conducted from the dialysate inlet to the dialysate outlet;
• and
• (e) the opening serving to restrict dialysate flow therethrough from the first portion to the second portion so as to increase dialysate pressure in the first region compared to the second region sufficiently to cause the pressure profile to be non-linear from the dialysate inlet to the dialysate outlet.

A dialyzer comprising:

• (a) a casing with a blood inlet, a blood outlet, a dialysate inlet and a dialysate outlet;
• (b) first and second groups of hollow-fiber semipermeable membranes, the first group representing a first region in the casing and the second group representing a second region in the casing, each of the fibers of the first and second groups having a lumen, the first and second groups connected to the blood inlet and the blood outlet so as to conduct extracorporeal blood from the blood inlet through the lumina of the fibers of the first and second groups to the blood outlet while dialysate is conducted though the casing, the dialysate flow exhibiting a pressure profile on the first and second groups from the first region to the second region;
• and
• (c) the dialyzer including a pressure barrier between the first region and the second region, the pressure barrier serving to restrict dialysate flow through the casing in the first region compared to the second region, the restriction to dialysate flow in the first region serving to increase dialysate pressure on the membrane in the first region compared to the second region sufficiently to cause the pressure profile through the casing from the dialysate inlet to the dialysate outlet to be non-linear.