Impedance cardiography and circulatory response to stress

The authors have used impedance cardiography as a monitor in many investigations. In one study, cardiac output measurements indicated that cardiopulmonary reflexes were critical in human adjustment to the upright posture. However, a sudden increase in transthoracic Z/sub 0/ during prolonged head-up tilt was found to be an immediate prelude to fainting, suggesting that a rapid shift in blood volume triggered the fainting reaction. In other experiments, the authors developed ensemble-averaging methods which permit online monitoring of blood pressure, cardiac output and thoracic blood volume in postoperative patients. They believe impedance cardiography to be a valuable tool for clinical monitoring of circulatory events.<>