Descending Aortic Flow Contribution to Intrathoracic Impedance—development and Preliminary Testing of a Dual Impedance Model

Objective. Impedance measurement of cardiac output has struggled to become established partly because there have been only a few attempts to establish a sound theoretical basis for this measurement. Our objective is to demonstrate that there is valuable aortic flow information available from an intrathoracic impedance signal which may eventually be useful in the measurement of cardiac output by impedance technology. Methods. A model, using dual impedance measurement electrodes and the change in impedance when blood flows, has been developed based on an intrathoracic impedance model of the descending aorta and esophagus. Using this model as the basis for measurement by an esophageal probe, we provide solutions to the velocity of blood flow in the descending aorta. Results. Five patients were studied. Only three patients had suitable signals for analysis but the aortic flow profiles from these three patients were consistent and realistic. Conclusion. Aortic blood flow information may be obtained from the intrathoracic impedance signal using this dual impedance method.