Method and apparatus for determining hemodialysis parameters

A method for determining blood access flow rate using a dialysis system including a dialyzer having a semipermeable membrane delimiting a first chamber through which blood circulates and a second chamber through which dialysis solution circulates and an arterial line and a venous line connected to an inlet and an outlet of a dialyzer, respectively, comprising:

• (a) positioning said arterial line and said venous line in a first orientation, wherein said arterial line carries blood from an upstream portion of a patient's fistula and said venous line carries blood toward a downstream portion of said fistula;
• (b) determining a first dialysance value for dialysis conditions in which said arterial and venous line are in said first orientation;
• (c) reconfiguring said arterial and venous lines to a second orientation, wherein said arterial line carries blood from a downstream portion of said fistula and said venous line carries blood toward an upstream portion of said fistula;
• (d) determining a second dialysance value for dialysis conditions in which said arterial and venous line are in said second orientation;
• and
• (e) calculating from said first and second dialysance values, a hemodialysis parameter, wherein said step of determining a first and second dialysance value each include making a measurement of the concentration of a substance in a dialysis solution downstream of said second chamber, and wherein said step of calculating includes calculating blood access flow rate according to the formula:
• Qa = ( Dc ) ⁢ ( Dc ′ ) Dc - Dc ′
• where
• Qa=blood access flow rate;
• Dc=the dialysance value determine when said arterial and venous line are in said first orientation;
• and
• Dc′=the dialysance value determine when said arterial and venous line are in said second orientation.

A method for determining recirculation using a dialysis system including a dialyzer having a semipermeable membrane delimiting a first chamber through which blood circulates and a second chamber through which dialysis solution circulates and an arterial line and a venous line connected to an inlet and an outlet of the dialyzer, respectively, comprising:

• (a) positioning said arterial line and said venous line in a first orientation, wherein said arterial line carries blood from an upstream portion of a patient's fistula and said venous line carries blood toward a downstream portion of said fistula;
• (b) determining a first dialysance value for dialysis conditions in which said arterial and venous line are in said first orientation;
• (c) reconfiguring said arterial and venous lines to a second orientation, wherein said arterial line carries blood from a downstream portion of said fistula and said venous line carries blood toward an upstream portion of said fistula;
• (d) determining a second dialysance value for dialysis conditions in which said arterial and venous lines are in said second orientation;
• and
• (e) calculating from said first and second dialysance values, a hemodialysis parameter, wherein said step of calculating includes calculating recirculation according to the formula:
• R=Qbi(1/Dc′−1/DC)
• where
• R=recirculation;
• Qbi=dialyzer blood inlet flow rate;
• Dc=the dialysance value determined when said arterial and venous line are in said first orientation;
• and
• Dc′=the dialysance value determine when said arterial and venous line are in said second orientation.

A method of determining recirculation using a dialysis system including a dialyzer having a semipermeable membrane delimiting a first chamber through which blood circulates and a second chamber through which dialysis solution circulates and an arterial line and a venous line connected to an inlet and an outlet of the dialyzer, respectively, comprising:

• (a) positioning said arterial line and said venous line in first orientation, wherein said arterial line carries blood from an upstream portion of a patient's fistula and said venous line carries blood toward a downstream portion of said fistula;
• (b) determining a first dialysance value for dialysis conditions in which said arterial and venous line are in said first orientation;
• (c) reconfiguring said arterial and venous lines to a second orientation, wherein said arterial line carries blood from a downstream portion of said fistula;
• (d) determining a second dialysance value for dialysis conditions in which said arterial and venous line are in said second orientation;
• and
• (e) calculating from said first and second dialysance values, a hemodialysis parameter, wherein said step of determining a first and second dialysance value each include making a measurement of the concentration of a substance in a dialysis solution downstream of said second chamber, and wherein said step of calculating includes calculating recirculation according to the formula:
• R=Qbi(1/Dc′−1/Dc)
• where
• R=recirculation
• Qbi=dialyzer blood inlet flow rate;
• Dc=the dialysance value determined when said arterial and venous line are in said first orientation;
• and
• Dc′=the dialysance value determined when said arterial and venous line are in said second orientation.

A method for determining a hemodialysis parameter in a dialysis system including a dialyzer having a semipermeable membrane delimiting a first chamber through which blood is circulated by a dialysis blood pump and a second chamber through which dialysis solution circulates and an arterial and venous line connected to an inlet and outlet of said first chamber, respectively, comprising:

• (a) determining urea dialysance and effective urea dialysance;
• and
• (b) calculating a hemodialysis parameter from said urea dialysance and said effective urea dialysance, wherein said step of determining urea dialysance and effective urea dialysance comprises:
• (i) reconfiguring said arterial line and venous line from a first orientation, wherein said arterial line carries blood from an upstream portion of a patient's fistula and said venous line carries blood to a downstream portion in said fistula, to a second orientation, wherein said arterial line carries blood from a downstream portion of a patient's fistula and said venous line carries blood to an upstream portion in said fistula;
• (ii) determining a concentration of urea at said first chamber inlet (CbiU), a concentration of urea at said first chamber outlet (CboU), and a concentration of urea downstream of said second chamber (CboU);
• and
• (iii) determining a systemic urea concentration (CsU);
• and wherein said step of determining urea dialysance and effective urea dialysance further comprises:
• (x) calculating a value for urea dialysance according to the formula:
• Du = ( CbiU - CboU ) CbiU ⁢ Qbi ;
• and
• (y) calculating a value for effective urea dialysance according to the formula:
• DeU = ( CbiU ) CsU ⁢ Du
• where
• Du=urea dialysance;
• DeU=effective urea dialysance;
• CbiU=concentration of urea at said dialyzer blood inlet;
• CboU=concentration of urea at said dialyzer blood outlet;
• CsU=concentration of systemic urea;
• and
• Qbi=dialyzer blood inlet flow rate.

A method for determining a hemodialysis parameter in a dialysis system including a dialyzer having a semipermeable membrane delimiting a first chamber through which blood is circulated by a dialysis blood pump and a second chamber through which dialysis solution circulates and an arterial and venous line connected to an inlet and outlet of said first chamber, respectively, comprising:

• (a) determining urea dialysance and effective urea dialysance;
• and
• (b) calculating a hemodialysis parameter form said urea dialysance and said effective urea dialysance, wherein said step of determining urea dialysance and effective urea dialysance comprises:
• (i) reconfiguring said arterial line and venous line from a first orientation, wherein said arterial line carries blood from an upstream portion of a patient's fistula and said venous line carries blood to a downstream portion in said fistula, to a second orientation, wherein said arterial line carries blood from a downstream portion of a patient's fistula and said venous line carries blood to an upstream portion in said fistula;
• (ii) determining a concentration of urea at said first chamber inlet (CbiU), a concentration of urea at first chamber outlet (CboU), and a concentration of urea downstream of said second chamber (CdoU);
• and
• (iii) determining a systemic urea concentration (CsU), and wherein said step of determining urea dialysance and effective urea dialysance further includes:
• (x) calculating a value for urea dialysance according to the formula:
• Du = ( CbiU - CboU ) CbiU ⁢ Qbi ;
• ⁢ and
• (y) calculating a value for effective urea dialysance according to the formula:
• DeU = CbiU CsU ⁢ Du
• where
• Du=urea clearance dialysance;
• DeU=effective urea dialysance;
• CbiU=concentration of urea at said dialyzer blood inlet;
• CboU=concentration of urea at said dialyzer blood outlet;
• CsU=concentration of systemic urea;
• and
• Qbi=dialyzer blood inlet flow rate.

A method for determining recirculation in a dialysis system including a dialyzer having a semipermeable membrane delimiting a first camber through which blood is circulated by a dialysis blood pump and a second chamber through which dialysis solution circulates and an arterial and venous line connected to an inlet and outlet of said first chamber, respectively, comprising:

• (a) determining urea dialysance and effective urea dialysance;
• and
• (b) calculating a hemodialysis parameter from said urea dialysance and said effective urea dialysance, wherein said step of calculating includes calculating recirculation according to the equation:
• R=Qbi(1/DeU−1/Du)
• where
• R=recirculation;
• Qbi=dialyzer blood inlet flow rate;
• DeU=effective urea dialysance;
• and
• Du=urea clearance dialysance.