subsubsub0307The invention relates to a method for determining at least a first volumetric flow (Q) in a blood treatment apparatus (1000) which has: a primary circuit (100) for conveying the blood that is to be treated； a secondary circuit (200) for conveying a fluid that is used for the blood treatment； a blood treatment module (300) as a section of the primary circuit (100) and/or secondary circuit (200) which module is provided for the exchange of fluids and/or substances between the primary circuit (100) and secondary circuit (200)； and an optionally provided fluid connection (5) between the primary circuit (100) and the secondary circuit (200) provided for introducing the first volumetric flow (Q) from the secondary circuit (200) into the primary circuit (100)； wherein the method comprises determining the first volumetric flow (Q) of the secondary circuit (200) by taking into consideration a first pressure value or pressure measurement value (S) and a second pressure value or pressure measurement value (S) in the secondary circuit (200). The invention further relates to a computing device and to a blood treatment apparatus.
