Patent ID: 7780620

Claim:
A method for determining at least one of hematocrit and blood volume during an extracorporeal blood treatment with an extracorporeal blood circuit, comprising the steps of: taking blood from a patient with a blood pump via an arterial cannula and an arterial line; providing the blood back to the patient via a venous line and a venous cannula; measuring an arterial pressure; and determining a hematocrit value and/or blood volume value from the arterial pressure by: selecting a relationship for a given cannula diameter and a given blood flow from a plurality of relationships between hematocrit HKT or blood volume RBV and pressure P in the extracorporeal circuit that are stored for various cannula diameters and various blood-flow values; and determining the hematocrit and/or blood volume at the arterial pressure in accordance with the selected relationship.