Flow rate dependent blood leak detection systems and methods

An extracorporeal blood treatment system comprising:

• a filtration unit comprising a primary chamber and a secondary chamber separated by a semi-permeable membrane;
• a blood withdrawal line connected to an inlet of the primary chamber and a blood return line connected to an outlet of the primary chamber, the blood withdrawal line and the blood return line being configured for connection to a patient cardiovascular system;
• a blood pump configured to control the flow of blood through the primary chamber;
• an effluent line connected to an outlet of the secondary chamber, wherein the effluent line is configured to remove effluent liquid from the secondary chamber;
• an optical source configured to emit light along an optical path;
• an optical detector configured to receive the light emitted by the optical source;
• a tube retainer configured to retain a tube such that the optical path passes through a liquid passing through the tube positioned in the tube retainer, wherein the effluent line comprises the tube positioned in the tube retainer;
• and
• a controller operably connected to the optical detector, the controller configured to:
• receive a flow rate signal representative of a flow rate of liquid passing through the tube in the tube retainer;
• receive a detection signal from the optical detector, the detection signal being indicative of a percent transmission of the light emitted by the optical source along the optical path that is received by the optical detector, the detection signal representative of an amount of blood in liquid passing through the tube in the tube retainer;
• when the flow rate signal indicates that the flow rate is below a selected flow rate, determine existence of a blood leak when the percent transmission of the light emitted by the optical source along the optical path that is received by the optical detector as indicated by the detection signal from the optical detector is below a first value;
• and
• when the flow rate signal indicates that the flow rate is above the selected flow rate after the flow rate signal indicates that the flow rate is below the selected flow rate, determine existence of a blood leak when the percent transmission of the light emitted by the optical source along the optical path that is received by the optical detector as indicated by the detection signal from the optical detector is below a second value, wherein the second value is greater than the first value;
• wherein the first value comprises a constant value when the flow rate is below the elected flow rate.