Device and method for monitoring an access to a patient, in particular a vascular access in extracorporeal blood treatment

A monitoring device for monitoring an access to a patient, comprising:

• a first tubular conduit comprising a first patient connector configured to withdraw a fluid from said patient;
• a second tubular conduit comprising a second patient connector configured to return the fluid to said patient;
• an AC voltage signal generator comprising a signal output with a first output connector and second output connector;
• a capacitive injection device configured for capacitive injection of the AC voltage signal, said capacitive injection device enclosing a first portion of one of the first tubular conduit or the second tubular conduit;
• a capacitive output device configured for capacitive output of the AC voltage signal, said capacitive output device enclosing a second portion of the other of the first tubular conduit or the second tubular conduit;
• an AC voltage signal measuring device comprising a signal input with a first input connector and second input connector;
• a first electrical connection between the first output connector of the signal output and the device for capacitive injection of the AC voltage signal, and a second electrical connection between the second output connector and a ground potential;
• a third electrical connection between the fluid in the first tubular conduit and the second tubular conduit and the ground potential;
• and
• an AC voltage signal evaluating device, said evaluating device configured to interact with the AC voltage signal measuring device such that a characteristic change of the amplitude of the measured AC voltage signal points to an incorrect vascular access,
• wherein the first input connector is electrically connected to the capacitive output device, and the second input connector is electrically connected to the ground potential.