Design of bioimpedance monitor and its application to atrioventricular delay optimization

We introduce our conception of a two-channel bioimpedance monitor for the impedance cardiography. We are describing the design of a homemade device which is based on a direct digital synthesizer and a digital down converter. This solution enables us to obtain a high-quality bioimpedance signal, which can be used for computing the cardiac output beat per beat. Our device allows simultaneous measuring of the complex impedance in two arbitrary directions on a human/animal body without any interference between the channels. We tested our device during a study of measuring the cardiac output at patients with implanted pacemakers. The cardiac output is measured with respect to the atrio-ventricular delay. We have scored the maximum relative cardiac output for each patient. The result of the study of 26 patients is presented in this paper.