Cardiac output measured by electrical impedance tomography: Applications and limitations

Cardiac output is one of the most determining parameters to assess cardiac function and manage hemodynamically unstable patients. Its continuous and non-invasive estimation, however, remains a technical challenge. In that context, electrical impedance tomography (EIT), an emerging modality for a new class of safe and portable hemodynamic monitors, appears as an appealing candidate for the continuous monitoring of cardiac output. However, the interpretation of EIT signals requires a feasibility study to be carried out. In the context of the Nano-Tera ObeSense project, we thus proposed a model and numerical simulations to evaluate the impact of myocardial motion in the estimation of cardiac output by EIT. It was found that 64% of the cardiac EIT signal originates from the mechanical interaction of the heart muscle with its surrounding tissues. However, because these movements are correlated with ventricular blood volume, the EIT-based estimation of cardiac output is not compromised. In parallel, regarding the technical aspect of EIT, we proposed innovative solutions for its measurement setup where the wiring complexity is drastically reduced, thus opening the way towards portable EIT systems.