Impedance cardiography

Impedance Cardiography (ICG) measurements were performed using the BioZ Dx device (SonoSite CardioDynamics, San Diego, CA) with subjects lying in supine position after at least 5 minutes of rest. Briefly, a pair of sensors placed on either side of the neck and a second pair of sensors placed on either side on the mid‐axillary line at the level of the xiphoid process are used to transmit a high frequency, low amplitude alternating current. The BioZ Dx calculates stroke volume based on detected change in impedance across the thoracic cavity over multiple cardiac cycles. This calculation includes adjustments to correct for differences in thoracic volume derived from sex, height and body weight, as well as changes in volume caused by respiration.