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Dvoukanálový, komplexní, bioimpedanční signál pro vyhodnocení hemodynamiky
Halámek, Josef ; Vondra, Vlastimil ; Jurák, Pavel ; Verner, Petr
The complex bioimpedance signals measured in the aortal and pulmonary artery directions simultaneously are discussed with respect to the information about the heart activity. All four signals carry some information about the blood flow, this information is partly equivalent (only SNR improvement and some artefact minimizations may be achieved by processing all signals) and partly non-equivalent (different behaviour according to excitation of the cardiovascular system). The more detailed analysis of time evolution of signal parameters according to the used excitation may contribute to new information about the hemodynamic system.
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Evaluation of cognitive ERP, ERD/ERS from intracerebral electrodes during the testing of executive functions, the time – frequency analysis
Chládek, Jan ; Bočková, M. ; Halámek, Josef ; Jurák, Pavel ; Nestrašil, I. ; Rektor, I.
In the present paper we describe the procedure of evaluation repeated EEG signals obtained from deep brain structures. Data are processed using the time-frequency analysis, which helps to determine individual frequency (IF) bands and afterwards are processed using complex demodulation technique to assess power envelope of IF band. We analysed phase-locked (Event-Related Potentials) and non-phase-locked (Event Related De/Synchronisation) signals obtained during different task conditions. Because of low signal to noise ratio, statistical tests of credibility and significance were used.
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Scatter plot and confidence interval
Halámek, Josef ; Holík, M. ; Jurák, Pavel
The exact definitions and standardisation are mostly missing in the area of biosignal measurement and processing. That in why the choice of the optimal method must be based on multidimensional statistical analysis. In this case the scatter plot with confidence ellipses can be used successfully.This graphical method is very simple and comprehensive. According to analysed parameters the method is two-dimensional, according to analysed groups multidimensional.
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Baroreflex sensitivity and heart rate
Halámek, Josef ; Jurák, Pavel ; Swenne, C. A. ; Kára, T. ; Souček, M. ; Eisenberg, M. ; Nykodým, J.
The correlation between baroreflex sensitivity (BRS) and heart rate (HR) is discussed. According to theoretical model, where the constant blood flow is supposed, the BRS given in [ms/mmHg] must correlate with HR and BRS in [mHz/mmHg] should not correlate with HR. This assumption was confirmed by the measurement on healthy young subjects, but it is not valid for old healthy subjects and for patients.
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Baroreflex sensitivity and signal processing
Halámek, Josef ; Jurák, Pavel ; Kára, T. ; Davies, L. C. ; Francis, D.
Baroreflex sensitivity (BRS) represents one of the most promising non-invasive markers of the cardiac disease. The measurement and computing of BRS are described but the significance of many different types of measurements and computing algorithms of BRS is neglected. This is one reason why the clinical applications of BRS suffer from poor reproducibility and sensitivity. The comparison of the short-term reproducibility and success rate of four different methods of assesing BRS is presented. The authors concerned themselves before all with a different type of measurement. Our aim is to test the coherency of BRS when the same data are analyzed using different algorithms.
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