1-78 Fresenius Medical Care 4008 4/08.03 (TM)
1.2 Functional description of the modules
1.2.1 Blood pump (arterial)
The blood pump ensures a sufficient blood flow in the extracorporeal blood circuit. It is absolutely
necessary that sterility is maintained and that the blood is prevented from becoming contaminat-
ed.
The blood pump is designed as roller pump provided in an exchangeable plug-in module
integrated in the hemodialysis machine. The blood line is installed between a stator, which, with
its rolling surface bent in a circle, represents a thrust bearing, and a rotor, which is provided with
rollers and pivoted in the stator. The pressure of the rollers causes the development of a narrow
or seal. If the rollers are moving in the direction of delivery, the blood is pushed in this direction.
A microprocessor controls the stepper motor with quartz accuracy, depending on the selected
delivery rate, the set line diameter, and the monitor signals.
The pressure measuring equipment comprises a piezo-resistive pressure transducer. The pres-
sure-proportional voltage is indicated on the monitor on a quasi-analog LED scale.
Functions of the blood pump:
– RAM and CRC test after turning power on,
– control and monitoring of the function by a dual processor system,
– emergency switchoff in case of an alarm: stop recognition (15 or 30 sec),
– setting of the speed to 180 ml/min during priming,
– measurement of the arterial pressure or the single needle pressure (depending on the model
concerned),
– semi-automatic loading and unloading of the line segment.
Error messages:
E.01 Line diameter outside the permissible range
E.02 Undefined hex switch position
E.03 Uncalibrated arterial pressure transducer
E.04 Run-time monitoring error during SN operation
E.05 SN stroke volume outside the permissible range
E.06 SN pressure thresholds outside the range of values of the A-D converter
E.08 Stop alarm
E.09 Error during A-D conversion
E.12 Rotary monitoring error (Hall sensor)
E.13 Monitoring error with regard to current sensing resistors
E.14 Monitoring error with regard to current sensing resistors
E.15 Speed monitoring error
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