Cancellation of respiratory artifact in impedance cardiography.

Impedance cardiography is a noninvasive technique for monitoring stroke volume, based on sensing variation in the thoracic impedance, z(t), due to blood flow. In this technique, first derivative of impedance, dz/dt, is used to calculate two parameters: ventricular ejection time and (-dz/dt)<inf>max.</inf>Respiration and motion artifacts cause base line drift in the sensed impedance waveform, mainly during exercise, and this drift results in errors in the estimation of the two parameters. Ensemble averaging of z(t) signal suppresses motion artifacts but it introduces distortion in the signal. In this study, simultaneously acquired respiratory signal is used for cancellation of corrupting respiratory artifact from the recorded z(t) signal, using adaptive noise cancellation technique.