The historical evolution of bioimpedance

Thoracic electrical bioimpedance is a technology that converts changes in thoracic impedance to changes in volume over time. In this manner, it is used to track volumetric changes such as those occurring during the cardiac cycle. These measurements, which are gathered noninvasively and continuously, have become more sophisticated and more accurate with the development of data signal processing and improved mathematical algorithms. This technology, first used in the 1960s, has benefited from the advent of the microprocessor and the better understanding of the cardiac cycle, thanks to technology such as echocardiography and magnetic resonance imaging. Today, noninvasive methods of measuring of cardiac output are coming into clinical use on a larger scale than ever before and are compared with other methods such as thermodilution and the direct and indirect Fick methods.