A noninvasive alternative for tracking hemodynamic status, thoracic electrical bioimpedance monitoring, also known as impedance cardiography, provides information about a patient’s cardiac index, preload, afterload, contractibility, cardiac output, and blood flow. In this procedure, electrodes are placed on the patient’s thorax. The electrodes have two purposes: to send harmless low-level electricity through the patient’s body and to detect return electrical signals. These signals, which are interruptions in the electrical flow, come from changes in the volume and velocity of blood as it flows through the aorta. The bioimpedance monitor interprets the signals as a waveform. Cardiac output is then computed from this waveform and the electrocardiogram (ECG).

Thoracic electrical bioimpedance monitoring eliminates the risk of infection, bleeding, pneumothorax, emboli, and arrhythmias associated with traditional invasive monitoring. The accuracy of results obtained by this method proves comparable to that obtained by thermodilution; the bioimpedance monitor also automatically updates information every second to tenth heartbeat.¹