Known dialyzers usually include four ports by which they are connected, on the one hand, to a line system of a dialysis machine and, on the other hand, to an extracorporeal blood system connected to a patient. Said ports are split into two ports for connection to the extracorporeal blood system via which blood to be purified is supplied to the dialyzer and drained from the dialyzer hereinafter also referred to as blood ports, and two ports for connection to the dialysis machine via which the dialysis fluid is supplied to the dialyzer and drained from the dialyzer, hereinafter also referred to as dialysis fluid ports (see schematic of FIG. 1).
Before the start of a blood treatment method it is necessary to fill and flush the extracorporeal blood circuit including the dialyzer filter so as to remove the air present in the extracorporeal circuit and possible residues in the dialyzer. As a rule, flushing is performed with a common saline solution. For this purpose, a pre-filled bag including common saline solution is used which is manually connected to the arterial blood hose end. The blood pump of the dialysis machine then conveys the fluid through the extracorporeal circuit. The common saline solution finally exits the venous end of the blood hose into a waste bag. After circulating sufficient fluid the extracorporeal circuit is flushed and filled and thus prepared for the blood treatment.
In order to prevent impurities from penetrating the dialyzer and fluid possibly present in the same from leaking as well as to protect the ports from damage the ports of the dialyzer are initially covered and closed.
For the afore-described flushing operation the caps closing the blood ports of the dialyzer have to be removed. They are then usually attached to the dialysis fluid ports. After flushing, the caps are removed from the dialysis fluid ports so that the feed and respective drain lines of the dialysis fluid hose system can be attached thereto.