Abstract: A patient monitoring system comprising: at least two pairs of electrodes in contact with the patient, a controller and a patient measurement system. At least one pair of electrodes passes a known current through a patient's chest. The voltage difference at another position on the patient induced by the known current is detected by a second at least one pair of electrodes and measured by a voltage measuring unit. From the voltage differences measured between the at least one second pair of the electrodes, the controller determines at least one biological parameter in at least one portion of the patient's chest. The patient measurement system ensures correct placement of the pairs of electrodes on the patient's chest, such that the electrodes are consistently placeable in the same positions on the patient's chest.