Dual-stage filtration cartridge

In a blood dialysis system including a source of substitution fluid, a blood dialysis machine, and a hemodiafiltration cartridge, the cartridge comprising:

• a housing including a blood inlet which receives blood, a blood outlet which discharges diafiltered blood, a dialysate inlet for receiving a dialysate fluid and a dialysate outlet for discharging the dialysate fluid;
• a member for dividing the housing into a first hemodiafiltration stage and a second hemodiafiltration stage, wherein the member permits the blood inlet to be in fluid communication only with the first stage while fluid communication is prevented between the blood inlet and the second stage, the blood outlet being in fluid communication only with the second stage;
• a first filtering element associated with the first stage;
• a second filtering element associated with the second stage;
• and
• an inter-stage section for providing fluid communication between the first and second stages, the inter-stage section including an inlet for receiving the substitution fluid, wherein blood entering the blood inlet is partially diafiltered in the first stage before being discharged into the inter-stage section where it is mixed with the substitution fluid to form a blood/substitution mixture which then flows within the second stage where further diafiltration occurs prior to the diafiltered blood being discharged through the blood outlet.

A dual-stage hemodiafiltration cartridge, the cartridge comprising:

• a housing having a dialysate inlet and dialysate outlet;
• a member dividing the housing into a first hemodiafiltration stage which receives blood through a blood inlet and a second hemodiafiltration stage, the member preventing the blood entering the blood inlet from fluidly communicating with the second stage;
• an inter-stage section for providing fluid communication between the first and second stages, the inter-stage section including an inlet for receiving the substitution fluid, wherein blood entering the inter-stage section from the first stage has a first concentration of toxins, the blood being mixed in the inter-stage section with the substitution fluid to form a blood/substitution mixture which then flows within the second stage, the second stage having a blood outlet through which blood having a second concentration of toxins is discharged, the first concentration of toxins being greater than the second concentration of toxins;
• and
• wherein dialysate fluid flow is counter-current to blood flow in the first stage and co-current to blood flow in the second stage.

A dual-stage filtration cartridge comprising:

• a housing having a first sterilization stage including first semi-permeable filtering elements and a second sterilization stage including second semi-permeable filtering elements, the housing having a first end and a second end with the first end including a fluid inlet port and a fluid outlet port and a member that divides the housing into the first sterilization stage and the second sterilization stage, first ends of the semi-permeable filtering elements being proximate to the first end of the housing, second ends of the semi-permeable filtering elements being proximate to the second end of the housing, the fluid inlet port being in fluid communication only with the first sterilization stage, while the fluid outlet port is in fluid communication only with the second sterilization stage, wherein the first and second semi-permeable filtering elements are sealed at the second end of the housing so as to cause the fluid entering the fluid inlet port to flow within lumen sections of the first semi-permeable filtering elements and then be filtered by being conducted across the first semi-permeable filtering elements and then subsequently being filtered again by being conducted across the second semi-permeable filtering elements and into the lumen sections of the second semi-permeable filtering elements prior to being discharged through the fluid outlet port.

A method of hemodiafiltration comprising the steps of:

• receiving a blood inflow;
• diafiltering said blood inflow in a first stage to provide a partially diafiltered blood outflow;
• mixing said partially diafiltered blood outflow with a substitution fluid to provide a blood/substitution fluid mixture;
• and
• diafiltering said blood/substitution fluid mixture in a second stage, wherein both the first and second stages are included in a single cartridge housing.

A method of hemodiafiltration comprising the steps of:

• receiving a blood inflow;
• diafiltering said blood inflow in a first stage to provide a blood outflow having a first concentration of toxins;
• mixing said partially diafiltered blood outflow with a substitution fluid at an inter-stage section to provide a blood/substitution fluid mixture;
• and
• diafiltering said blood/substitution fluid mixture in a second stage to produce blood having a second concentration of toxins, the first concentration being greater than the second concentration, wherein dialysate fluid is common to both the first and second stages.

A method for filtering a fluid, comprising:

• receiving a fluid at an inlet port of a dual-stage filtration cartridge;
• passing the fluid through a lumen section of a first filtering element;
• conducting the fluid across the first filtering element into an inner cavity of the housing;
• conducting the fluid across a second filtering element and into a lumen section thereof;
• and
• passing the fluid through the lumen section of the second filtering element to an outlet port through which the fluid is discharged, wherein the inlet and outlet ports are at the same end of the dual-stage cartridge and the first and second filtering elements each includes an open end and a closed end, the closed ends being at the same end of the dual-stage cartridge.