Surcom Minnesota 304B Impedance Cardiograph

The Surcom Minnesota Impedance Cardiograph Model 304B is a noninvasive hemodynamic monitor that measures changes in thoracic impedance to assess cardiac function. It injects a 4 mA alternating current at 100 kHz across the thorax using a tetrapolar band electrode configuration and records both the baseline thoracic impedance Z0 and the first derivative of impedance (dZ/dt) in synchrony with an ECG input. Widely cited in research, the 304B is described as a commercially available impedance cardiograph that has been used for continuous hemodynamic measurements and for estimating cardiac output and stroke volume when paired with established analysis methods. The model is produced by Surcom, Inc., based in Minneapolis, Minnesota, and has been referenced in clinical research literature as the Minnesota Impedance Cardiograph Model 304B.