Access disconnection systems and methods

An extracorporeal blood system comprising:

• an extracorporeal blood machine;
• an extracorporeal blood circuit coupled operably to the machine, the extracorporeal blood circuit including first and second blood lines, the blood lines configured to be in blood flow communication with a patient;
• an electrical loop including first and second electrodes placed in contact with blood flowing through the first and second blood lines, respectively;
• a device configured to inject an electrical signal into the blood circuit via the loop;
• a third electrode placed in contact with blood flowing through the extracorporeal blood circuit, the third electrode configured to enable a change in an electrical value to be measured so that an access disconnection of the extracorporeal blood circuit from the patient can be measured;
• and
• a conductive path between the first and second contacts, forming part of the electrical loop, the conductive path not directly connected to a signal source or a measuring device for providing and measuring the electrical value, respectively.