A study on methods for impedance cardiography

Impedance Cardiography (ICG) has been developed to measure non-invasively cardiac functions, such as stroke volume (SV) and ventricular ejection time (VET) by the use of maximum change of the first derivative of impedance wave /spl Delta/Z(dZ/dt). A series of conventional signal processing methods were first described briefly, then, a new time-frequency analysis method was introduced in detail. Their advantages and disadvantages were studied and compared. The results showed that the latest method has more advantages in reducing ventilation artifacts and motion noise, resulting in greater accuracy. Moreover, the time-frequency analysis method can extract detail information on the transient impedance signal, which is more precise for the practical case. This method may also be powerful in revealing the insight of signal because of its ability to disclose the intimate relationship between time and frequency by the three dimensional display.