This paper summarizes current knowledge about electrical impedance tomography (EIT) and its present and possible applications in clinical practice in pediatric respiratory medicine. EIT is a relatively new technique based on real-time monitoring of bioimpedance. Its possible application in clinical practice related to ventilation and perfusion monitoring in children has gaine increasing attention in recent years. Most of the currently published data is based on studies performed on small and heterogenous groups of patients. Thus the results need to be corroborated in future well-designed clinical trials. Firstly a short theoretical overview summarizing physical principles and main advantages and disadvantages is provided. It is followed by a review of the current data regarding EIT application in ventilation distribution monitoring in healthy individuals. Finally the most important studies utilizing EIT in ventilation and perfusion monitoring in critically ill newborns and children are outlined. 1. Introduction Electrical impedance tomography (EIT) is a relatively new, noninvasive monitoring technique. Its usefulness in lung function monitoring in adults has been examined in numerous studies. The increasing number of publications in pediatric population in recent years shows a wide range of clinical applications of this method. Unlike conventional radiography or computed tomography (CT), EIT is radiation-free and enables continuous real-time monitoring of the lung function. The current knowledge about the application of EIT in clinical practice in children will be reviewed in this paper. 2. Physical Principles The theoretical aspects of electrical impedance tomography were described over 30 years ago [1]. The physical principle is based on the measurement of intrathoracic bioimpedance distribution. Standard electrodes are placed circumferentially on the surface of the patient’s chest. High-frequency, low-amplitude electrical current is applied sequentially to the chest by the consecutive pairs of electrodes. The surface potential is measured by the remaining pairs of electrodes. Most currently available systems are equipped with 16 electrodes. One complete rotation creates a voltage profile, or a frame which is used for reconstruction of a cross-sectional tomographic image of the chest. The reconstruction is based on the Sheffield backprojection reconstruction algorithm. The picture represents distribution of impedance in different regions of the lungs. However this provides very little information about changes of impedance in time. Following the first
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