Abstract

Impedance cardiography (ICG) is a simple and cheap method for acquiring hemodynamic parameters. Unfortunately, not all physiological influences on the ICG signal have yet been identified. In this work, the influence of heart and lung dynamics is analyzed using a simplified model of the human thorax with high temporal resolution. Simulations are conducted using the finite integration technique (FIT) with temporal resolution of 103 Hz. It is shown that changes in heart volume as well as conductivity changes of the lung have a high impact on the ICG signal, if analyzed separately. Considering the sum signal of both physiological sources, it can be shown that they compensate each other and thus do not contribute to the signal. This finding supports Kubicek’s model.

Highlights

  • One of the most common causes of death in Western Europe is chronic heart failure (CHF)

  • This task will be accomplished by simulations using finite integration technique (FIT) and an anatomical data set of a male human as a basis for a simplified dynamic model

  • The sum of the dynamic impedance measured at 100 kHz and including the volume change of the aorta has been compared to measured data of a male human and the results show excellent agreement (r = 0.94) using a correction factor [12]

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Summary

Introduction

One of the most common causes of death in Western Europe is chronic heart failure (CHF). Measures of the severity of this cardiovascular disease are hemodynamic parameters such as stroke volume (SV). The gold standard for measuring these parameters has been the thermodilution technique, which utilizes a pulmonary artery catheter. An alternative method for assessing hemodynamic parameters non-invasively and cost-effectively is ICG. ICG is not commonly used as a diagnostic method, because it is not considered to be valid [1]. One reason is the inaccuracy of the technology itself concerning SV calculations. Another possible reason for this is that processes in the human body during ICG measurements are widely unknown. One way to analyze where the current paths run and which tissue contributes significantly to the measurement result is to use computer simulations employing FIT. Other researchers have already examined multiple sources of the ICG signal, using various approaches: some works are based on simple geometries [2], others on real anatomical data, such as MRI data [3]

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