A device is disclosed for determining an access flow rate of a patient when connected to a blood treatment machine. The device performs a measurement phase in which the blood treatment machine is caused to operate in first and second operating states, where the second operating state at least differs from the first operating state by a change of flow direction of blood or treatment fluid through a dialyzer of the blood treatment machine. Based on sensor values representing a fluid property of the treatment fluid in the first and second operating states, the device computes a measurement value of comparison parameter (e.g. a ratio or a difference) that compares treatment efficiency in the first operating state to treatment efficiency in the second operating state, and determines, based on the measurement value, an estimated value of the access flow rate.

A blood purification apparatus that includes a blood circuit including an arterial blood circuit provided with an arterial puncture needle and a venous blood circuit provided with a venous puncture needle with which an access vessel is puncturable, the blood circuit allowing blood of the patient to extracorporeally circulate; a blood purifier connected to the arterial blood circuit and to the venous blood circuit and that purifies the blood flowing through the blood circuit; a blood pump provided to the arterial blood circuit; a recirculating-blood-detecting unit capable of detecting recirculating blood when the blood of the patient is caused to extracorporeally circulate through the blood circuit by activating the blood pump, the recirculating blood being blood once returned to the patient from the venous blood circuit and reintroduced into the arterial blood circuit; and a recirculation-rate-calculating unit capable of calculating recirculation rate, the recirculation rate being a proportion of the recirculating blood in the blood flowing in the arterial blood circuit. The blood purification apparatus includes a control unit capable of executing a treatment mode in which blood purification treatment is performed with the blood purifier while the blood of the patient is caused to extracorporeally circulate through the blood circuit by activating the blood pump in a state of normal connection where an upstream part of the access vessel is punctured with the puncture needle at a distal end of the arterial blood circuit and a downstream part of the access vessel is punctured with the puncture needle at a distal end of the venous blood circuit; and a measurement mode in which the detection of recirculating blood by the recirculating-blood-detecting unit and the calculation of recirculation rate by the recirculation-rate-calculating unit are performed while the blood of the patient is caused to extracorporeally circulate through the blood circuit by activating the blood pump in a state of reverse connection where the downstream part of the access vessel is punctured with the puncture needle at the distal end of the arterial blood circuit and the upstream part of the access vessel is punctured with the puncture needle at the distal end of the venous blood circuit, the calculated recirculation rate being used in calculating blood flow rate in the access vessel that is calculable in the measurement mode.

A method automatically characterizes a vascular access of a dialysis patient who is or was connected to a dialysis machine, the vascular access being characterized dependent on a recirculation rate.

An apparatus for measuring recirculation using thermodilution during extracorporeal blood treatment including a temperature varying unit arranged to cyclically heat and/or cool blood in a venous tube segment of the blood tube system for a quasi-continuous recirculation measurement; and a detecting device configured to measure a variation of a physical parameter resulting from the heating and/or cooling. The detecting device is arranged to detect, in a case free from recirculation, a first physical parameter and to detect, in a case afflicted with recirculation, a physical parameter varied by the cooling and/or heating of the blood by the temperature varying unit as a second physical parameter in the blood tube system. A method for measuring recirculation carries out appropriate steps.

The invention relates to a process for monitoring the supply of substitution fluid upstream or downstream of a dialyzer or filter arranged in an extracorporeal blood stream. One embodiment provides, for the detection of predilution or postdilution, for measuring the pressure in the blood stream downstream of the dialyzer or filter, predilution or postdilution being recognized on the basis of the change in pressure following the shutting off and/or starting up of the substituate pump provided for conveying the substitution fluid. Another embodiment provides for recognizing predilution or postdilution on the basis of the comparison of the oscillating pressure signal attributable to the substituate pump to a characteristic reference signal. The characteristic reference signal to which the pressure signal of the substituate pump is compared is preferably the oscillating pressure signal of a blood pump arranged in the blood stream for conveying the blood upstream of the dialyzer or filter. In addition, the invention relates to an extracorporeal blood treatment device with a facility for detecting predilution or postdilution, which device operates according to the processes detailed above.

A device and method for detecting recirculation for an extracorporeal blood treatment apparatus and an apparatus with a device for detecting recirculation are based on targeted haemodilution by administration of a substituate bolus, causing a pressure change in venous and arterial branches of the extracorporeal circuit due to a viscosity change of flowing fluid. Recirculation is detected based on detection of the pressure change. The device includes a control unit cooperating with a device for conveying blood and a device for supplying substituate. The control unit provides an operating mode for detecting recirculation, in which blood flow rate is reduced during administration of a substituate bolus. With simultaneous substituate bolus administration and reduction of blood flow rate, the composition of fluid flow is optimized for detection of recirculation, so that fairly large pressure changes result in venous and arterial branches, thereby improving sensitivity and reliability of the measurement method.

A blood treatment machine, module device and recirculation determination method feature a dialyser. A sensor is connected downstream of the dialyser and connected to a control unit that determines recirculation without blood-side bolus administration. The control unit: acquires the signal of a variable of consumed dialysis liquid measured by the sensor; switches the machine from a base mode into an interim mode, in which a dialysis liquid amount is confined in the dialyser on the dialysis liquid membrane side while blood flows in the blood circuit; changes into the base mode to supply the previously confined dialysis liquid amount as a first or second dialysis liquid bolus to the sensor to measure a signal change relative to a base signal as a corresponding first or second bolus signal; and deduces a recirculation from a deviation of the second bolus signal compared to the first bolus signal.

A method and a device for determining a recirculation during a dialysis on the basis of the response of the dialysis system to an alteration of a system-related operating value are described. Recirculation may be determined by establishing, at the side of the dialysis liquid, a reference parameter that represents the concentration of uremic toxins from the extracorporeal circulation, and calculating a target parameter for a system-related target operational value from the reference parameter, presetting the system-related target operational value and establishing an actual parameter related to the system-related target operational value, determining an actual comparative value from the actual parameter and the reference parameter related to the system-related target operational value and comparing the actual comparative value with a system-specific target comparative value related to the system-related target operational value, and converting the comparison result into a recirculation degree.

An example medical system includes a hemodialysis device configured to receive blood from vasculature of a patient via an arterial line and to deliver blood to the vasculature of the patient via a venous line. The medical system includes a hematocrit sensor configured to generate a signal indicative of a hematocrit level of blood in at least one of the arterial line or the venous line. The medical system also includes processing circuitry configured to determine a change in blood volume of the patient over time based on the signal indicative of the hematocrit level, determine a threshold blood volume reduction over time for the patient, compare the change in the blood volume of the patient over time to the threshold blood volume reduction over time, and based on the comparison, generate an indication of vascular access recirculation.

An example medical system includes a hemodialysis device configured to receive blood from vasculature of a patient via an arterial line and to deliver blood to the vasculature of the patient via a venous line. The medical system includes a hematocrit sensor configured to generate a signal indicative of a hematocrit level of blood in at least one of the arterial line or the venous line. The medical system also includes processing circuitry configured to determine a change in blood volume of the patient over time based on the signal indicative of the hematocrit level, determine a threshold blood volume reduction over time for the patient, compare the change in the blood volume of the patient over time to the threshold blood volume reduction over time, and based on the comparison, generate an indication of vascular access recirculation.