Towards automation of single needle vascular access

In the past, SN devices have not always fulfilled the expectations of clinicians, but adequate extracorporeal blood flows can only be expected from adequate intravascular flows, which of course applies to any SN method. In some instances, problems may have been caused by poor equipment design, but poor understanding and handling of devices may equally have at fault. Improvement of presently available SN equipment therefore seemed necessary. A fully automatic, second generation cross-over SN control device has been designed which is simple to operate and has the following advantages: Operation is restricted to the speed control setting of the blood pump in the host machine. The CO-SN system automatically responds to changes of fistula flow by modulating the stroke volumes. Recirculation can be kept below 10%. The blood pump rate can be adjusted to the maximum flow rate of the cannulated vessel. Obligatory ultrafiltration is eliminated. Blood compartment pressure is constant. The Munich prototype cross-over SN module was designed as an auxiliary SN equipment which may substitute the Unipuncture machine.