Cardiac output (CO) is a key variable when describing and treating the cardiovascular system. The ideal cardiac output (CO) monitor would be safe, non-invasive, low-cost, painless, easy to interpret and would allow for the continuous, hands-free acquisition of accurate data. Electrical cardiometry (EC), a more recent version of impedance cardiography (ICG), meets many of the criteria for an ideal monitor and previously published research suggests that EC successfully trends CO1-3, but its accuracy in measuring absolute values of stroke volume (SV) has been inconsistent in published research4-8. Electrical cardiometry works by sending an insensible high frequency alternating current through the thorax and measures changes in thoracic impedance that are attributed to systolic blood flow acceleration over the cardiac cycle. Using fiducial points in the tracing of the first derivative of impedance, EC calculates left ventricular ejection time (LVET) and mean velocity of blood during systole. By further estimating a patient constant that is primarily based on body mass ('volume of electrically participating tissue' (VEPT)), stroke volume is estimated in the following way: