Doctors need to measure blood conductivity to calculate the internal pump volume of the heart and the blood circulation rate. However, when patients receive additional fluids - for example, water, drips or drugs during surgery - the conductivity can fluctuate. The new system is able to measure these changing conductance levels in real time.

The device works by inserting a catheter (a flexible tube) containing a series of electrodes into the main pump chamber of the heart. By applying a small constant current to the electrodes and measuring the potential difference between each pair of electrodes, it is possible to calculate the conductivity using a simple formula. The first tests of the technique are now being carried out at the Cleveland Clinic Foundation.