Abstract:

Electrical Impedance Tomography (EIT) is a relatively new imaging and monitoring method to monitor pulmonary health at the bedside.The EIT has been successfully applied for monitoring of the ventilation and is thought to have clinical potential, since this method is non-invasive, inexpensive, long-term able and allows live monitoring at the patients bed.The analysis of pulmonary perfusion by means of EIT is still matter of research, which is the missing information beside the ventilation to analyse pulmonary gas exchange efficiency. During the research for this thesis, the influence of the pulmonary artery pressure (PAP) on the EIT signal is observed in order to investigate the perfusion information in EIT measurements. The analyses have been carried out on six pigs of an experimental study during respiratory hold phases.In the first part of the thesis a method was established automatically detecting these respiratory hold sequences, the PEEP, which influences the blood pressure and flow, and un-physiological segments of the pulmonary artery pressure (PAP) measured during the study. The latter was performed in order to gain a reliable PAP signal, which served as hemodynamic comparison parameter. During the second part of this work the EIT segments at the time of respiratory hold phases were analysed. At first, the components were segmented into intervals of one heartbeat (from R-peak of the electrocardiogram to the succeeding R-peak) via detecting the R-peaks of the regarding electrocardiogram (ECG) signal. The approach of examining whether the EIT can be used for quantifying blood flow, was adopted from the paper Non-invasive monitoring of pulmonary artery pressure from timing information by EIT: experimental evaluation during induced hypoxia by Martin Proença et al, which based on a human study. It implied the calculation of the time between the respective R-peak and the start of the next EIT slope, which was called pulse arrival time (PTT). This parameter was assumed to represent the time between the ejection of blood out of the ventricle and the arrival at the respective point in the lung. The PTT was approximated to anti-correlate to the PAP and so give EIT-based information about the hemodynamic in the lung. In order to approve this thesis, two approaches to gain EIT timing information, namely the template and correlation approach, were implemented and applied in this work. All in all, the high correlation between the PAP and the time shift of the cardiac pulsatility component in EIT signals of the paper could not be found in this thesis. In which way the methods were implemented and possible reasons for the different results compared to the Proença paper are introduced and discussed.