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.