Jana Kolářová

Sleep scoring using artificial neural networks

Rapid development of computer technologies leads to the intensive automation of many different processes traditionally performed by human experts. One of the spheres characterized by the introduction of new high intelligence technologies substituting analysis performed by humans is sleep scoring. This refers to the classification task and can be solved - next to other classification methods - by use of artificial neural networks (ANN). ANNs are parallel adaptive systems suitable for solving of non-linear problems. Using ANN for automatic sleep scoring is especially promising because of new ANN learning algorithms allowing faster classification without decreasing the performance. Both appropriate preparation of training data as well as selection of the ANN model make it possible to perform effective and correct recognizing of relevant sleep stages. Such an approach is highly topical, taking into consideration the fact that there is no automatic scorer utilizing ANN technology available at present.

A Wavelet Based Detection of Abnormal Intra-QRS Potentials

This study aims to analyse abnormal intra-QRS potentials recorded during myocardial ischemia in experiments with guinea pig hearts and to prove relation between intra-QRS potentials and ischemia. Intra-QRS potentials manifest as low-level high frequency notches within QRS complexes. An efficient tools for detection of the potentials is continuous wavelet transform. Detailed analysis of CWT of QRS complexes from control period, ischemia period and reperfusion resulted in designing a potential detector based on selection of a suitable CWT subband. Results proved close connection of intra QRS potential manifestation and early state of myocardinal ischemia.

Frequency domain HRV analysis of ischemia manifestation at isolated rabbit hearts

The ischemia manifestation was analyzed using heart rate variability (HRV) parameters in frequency domain. Assessment of HRV was based on analysis of consecutive normal R-R intervals during 5 minutes interval in seven section of measured ECG: control period, ischemia I-III periods and reperfusion I-III periods. Seven rabbits were used for experiment.

Influence of ischemia on left ventricular depolarization in isolated rabbit hearts perfused according to Langendorff

The aim of this study was to search for relation between electrical activity recorded from whole isolated heart and simultaneously from one cell. The QRS complex of electrogram (ECG) corresponds to the depolarization of the ventricles. The depolarization propagation is shown by monophasic action potential (MAP) recorded at appointed place during experiment. Electrogram changes observed during ischemia should be accounted for changes on cellular level. MAPs and ECG were recorded simultaneously. The activation time (AP), defined as distance from the earliest QRS deflection to MAP upstroke, changes with duration of ischemia. The excitement propagation and conduction in ischemic heart takes longer time in comparison to non-ischemic myocardium.