Only two signals are required for analysis in the Impedance Cardiography (IMP) analysis application – ECG and Zo. The third signal used in analysis, dZ/dt, is the inverted first derivative of the Zo signal and can be derived in hardware and sampled during acqusition or derived in software post-acquisition. The hardware-derivation is done on a continuous basis and typically has better feature clarity than the software-derived alternative.
You can enable software-derived dZ/dt by navigating to the Impedance Calibration Settings tab and selecting “Derive from Zo” as your dZ/dt source.
If you only mapped a Zo channel, this source will be selected automatically.
Hardware Measured dZ/dt
Many devices (including all MindWare impedance cardiographs) will derive dZ/dt from Zo in hardware during data collection. In these cases, you can map a dZ/dt channel and use it directly. You can ensure you are using the hardware-derived dZ/dt measurement by changing the dZ/dt Source to “Measured”