Impedance cardiography overview
instrumentation: The impedance cardiograph provides an excitation current and a means of recording associated fluctuations in electrical impedance in the upper thorax.There are a number of commercially available impedance cardiographs, but the Minnesota Impedance Cardiograph Model 304B has been used most widely in research application.This model uses a 4-mA constant current source with a 100-kHz oscillator frequency and includes an LED display of basal thoracic impedance kubicek,Karriegis ,Patterson, Witsoe, and Mattson (1996) first describe a tetrapolar band electrode configuration which has since been adopred in most studies using the impedance techinque for monitoring cardiovascular function.Two current electrodes introduce the high -frequency excitation current with the impedance is measured across an inner two-voltageelectrode. Band electrodes are avilable commercially and typically consist of disposable strips of aluminum-coated Mylar forming the electrode along the center of the tape.
The usual placement of the four band electrodes is illustrated in Figure 2. The upper and lower voltage electrodes are placed around the base of the neck and around the thorax at the level if the xiphisternal junction.The outer current electrodes are placed