Patent ID: 6746415
Filing Date: 2004-06-08
Classification: A61M

Abstract:
A noninvasive method of measuring cardiac output in a dialysis system having arterial and venous tubing lines using a first extracorporeal cuvette located at an input to a dialyzer in said dialysis system and a second extracorporeal cuvette located at an output of said dialyzer, each extracorporeal cuvette having an inlet, an outlet, and a conduit in fluid communication therebetween, said conduit having first and second opposed walls allowing electromagnetic radiation therethrough with inner surfaces thereof having a first predetermined separation therebetween, outer surfaces and said inner surfaces of said first and second opposed walls being planar, said inner surface of said first wall including a pedestal emanating outwardly toward the inner surface of said second wall, said pedestal having a planar end surface defining a second predetermined separation from said second wall, said first predetermined separation being greater than said second predetermined separation so that a shorter radiation path length is created across said second predetermined separation, said method comprising the steps of:injecting a first saline bolus into the arterial tubing; injecting a second saline bolus into the venous tubing; determining the blood flow rate through at least one of said extracorporeal cuvettes in the dialysis system; selecting the first saline bolus as a reference bolus and the second saline bolus as a measuring bolus; determining a first ratio of the measuring bolus to the reference bolus; determining the change of hematocrit over time for the reference bolus by comparing an output of said first extracorporeal cuvette with an output of said second extracorporeal cuvette; determining the change of hematocrit over time for the measuring bolus by comparing an output of said first extracorporeal cuvette with an output of said second extracorporeal cuvette; determining a second ratio of the reference bolus over time to the measuring bolus over time; and calculating the product of the first ratio, the second ratio and the blood flow rate.