Jana Kolarova

EEG biofeedback

EEG biofeedback is an up to date therapeutic system able to cure low concentration ability, attention deficit hyperactivity disorder (ADHD), learning disability or depressions. Biofeedback systems based on EDG, ECG, EMG or EEG are used in numerous rehabilitation and therapeutic centers. Designed EEG biofeedback acquires EEG signal with a use of BIOPAC Acquisition unit. The signal is amplified, filtered and digitized. The software part of the system is designed in LabVIEW; it handles system control, data processing and data and feedback visualization. Two simple graphical games are included. The games are designed to increase the patients efficiency of mind concentration or body and mind relaxation.

Breath Analysis Using a Time-of-Flight Camera and Pressure Belts.

The proper way of breathing is important for everyone. Healthy people often do not follow respiration until breathing problems start-during stress or during sport activity in physiological cases. More serious cases are stroke, injury, or surgery of the chest and others. So, learning to breathe correctly and/or breathing diagnosis is considerable for many reasons. Two novel methods of breath analysis suitable for diagnostics and rehabilitation are presented. The first technique utilizes pressure belts fastened to the patients belly and chest, and the second method relies on a SwissRanger SR-4000 time-of-flight camera. The measurement principles are described together with the advantages and disadvantages of the applied techniques. The SwissRanger camera depth calibration is proposed to facilitate better results during the breath analysis. The methods are tested on a group of students to provide a comparison of their individual performances. As it was demonstrated, presented methods proved to work reliably. The method based on time-of-flight camera seems to be more suitable for diagnosis, while the method based on pressure belts is more suitable for rehabilitation and biofeedback applications.

Classification of ventricular premature and ischemic beats in animal electrograms

Many approaches have been proposed for automatic classification of different pathological events in ECG signals. Present study is focused on analysis and classification of non-ischemic, moderate and severe ischemic, and VPB segments in data obtained in rabbit isolated hearts. It is shown, that use of low number of morphological parameters calculated from electrograms combined with even simple classification method allows achieving of accurate results (with overall accuracy up to 0.99) for four types of the segments.

Continuous Monitoring of Respiration during Rehabilitation

Continuous monitoring of respiratory rehabilitation is important for evaluation of the respiratory function and its improvement. Respiratory rehabilitation can be applied in many of neuromuscular diseases or after chest surgery. We have proposed a simple method for monitoring breathing in the chest and in the abdomen by measuring with two pressure cuffs placed in the chest and abdomen area. The measurement is relative, but sufficient for the purposes of respiration exercises or for on-line therapeutic games based on breath control. Another proposed method uses Time-of-Flight camera. This type of measurement is absolute and suitable for both diagnosis and continuous monitoring of therapy.

Use of EEG for validation of flicker-fusion test

There are many different methods for evaluation of alertness level of a person. The commonly used questionnaires and some physiological test such as flicker-fusion (FF) test are not objective. Other objective methods based on the analysis of biological signals can be used for validation of these tests. The present study is focused on analysis of spectral features of EEG measured in sleep deprived subjects during experiment containing FF test performing. The results of the study show that FF test does not affect electrical brain activity dramatically and, thus, can be used for alertness level evaluation. It is also shown that subjective determination of state using questionnaires can differ from those obtained by objective method based on the analysis of EEG. These results can be useful for correct interpretation of FF test results.

Effect of increased left ventricle mass on ischemia assessment in electrocardiographic signals: rabbit isolated heart study

BackgroundDetailed quantitative analysis of the effect of left ventricle (LV) hypertrophy on myocardial ischemia manifestation in ECG is still missing. The associations between both phenomena can be studied in animal models. In this study, rabbit isolated hearts with spontaneously increased LV mass were used to evaluate the effect of such LV alteration on ischemia detection criteria and performance.MethodsElectrophysiological effects of increased LV mass were evaluated on sixteen New Zealand rabbit isolated hearts under non-ischemic and ischemic conditions by analysis of various electrogram (EG) parameters. To reveal hearts with increased LV mass, LV weight/heart weight ratio was proposed. Standard paired and unpaired statistical tests and receiver operating characteristics analysis were used to compare data derived from different groups of animals, monitor EG parameters during global ischemia and evaluate their ability to discriminate between unchanged and increased LV as well as non-ischemic and ischemic state.ResultsSuccessful evaluation of both increased LV mass and ischemia is lead-dependent. Particularly, maximal deviation of QRS and area under QRS associated with anterolateral heart wall respond significantly to even early phase (the 1st-3rd min) of ischemia. Besides ischemia, these parameters reflect increased LV mass as well (with sensitivity reaching approx. 80%). However, the sensitivity of the parameters to both phenomena may lead to misinterpretations, when inappropriate criteria for ischemia detection are selected. Particularly, use of cut-off-based criteria defined from control group for ischemia detection in hearts with increased LV mass may result in dramatic reduction (approx. 15%) of detection specificity due to increased number of false positives. Nevertheless, criteria adjusted to particular experimental group allow achieving ischemia detection sensitivity of 89–100% and specificity of 94–100%, respectively.ConclusionsIt was shown that response of the heart to myocardial ischemia can be successfully evaluated only when taking into account heart-related factors (such as LV mass) and other methodological aspects (such as recording electrodes position, selected EG parameters, cut-off criteria, etc.). Results of this study might be helpful for developing new clinical diagnostic strategies in order to improve myocardial ischemia detection in patients with LV hypertrophy.

Voltage sensitive dye di-4-ANNEPS prolongs impulse conduction through ventricles, but not through AV node in isolated rabbit heart

Voltage sensitive dyes are widely used for recording of action potential in various cardiac studies. The elementary condition for its application is the fact that measured electrophysiological parameters would not be affected by the measuring procedure itself. The RR interval prolongation in the presence of the most frequently used voltage sensitive dye di-4-ANEPPS has been reported, but its exact mechanism is not known. In this study, the impact of di-4-ANEPPS on impulse conduction through the atrioventricular (AV) node and through cardiac ventricles in isolated rabbit heart was examined. The impulse conduction through AV node in the presence of di-4-ANEPPS was prolonged only during dye loading in the 14th, 16th and 17th minute. Only sporadic AV blocks were observed. In comparison, the prolongation of impulse conduction through cardiac ventricles was observed from the 13th minute of loading and persisted to the end of this phase as well as over the whole wash out phase.

The effect of voltage sensitive dye di-4-ANEPPS on the RT/RR coupling in rabbit isolated heart

Voltage sensitive dye (VSD) di-4-ANEPPS is ordinary used for optical measurement of action potential in experimental cardiology. In this work, the effect of the dye on the RT/RR coupling measured in electrograms (EG) recorded on rabbit isolated hearts was studied. The results were compared with the control experiments without VSD administration. The comparison was performed in preparation stage of the experiment that consisted of three phases: stabilization (S), VSD loading (L), and washout (W). The median and interquartile range (Q0.75-Q0.25) of the difference in RR, QT and RT/RR between the beginning and the end of the phases were computed and compared between the both groups. Δ(RT/RR), in S, L and W, was -0.095, 0.061; -0.093, 0.043; -0.027, 0.039 in di-4-ANEPPS-treated group and -0.127, 0.071; 0.006, 0.016; -0.001, 0.025 in control group. The significant difference (P<;0.01) was found between two groups in L phase. Additionally, there was the significant difference in ΔRR [ms] which was 120.9, 74.8 in di-4-ANEPPS-treated group and 6.94, 19.28 in control group in the same phase. The significant difference in Δ(RT/RR) between both groups shows a possible effect of di-4-ANEPPS on the RT/RR coupling which is mainly caused by the prolongation of RR interval during loading with the dye.

The frequency changes in electrograms during ischemia experiments - analysis by Matching Pursuit decomposition

The aim of this study was to analyse frequency components in electrograms (EGs) recorded from surface of isolated guinea pig hearts perfused according to Langendorff. Time-frequency analysis is based on algorithms Matching Pursuit and Wigner-Ville Distribution and its combination showing the energy density of the signal. The presented algorithms were tested on a set of electrograms, recorded during ischemia followed by reperfusion. The frequency components changed markedly during global ischemia experiments.

The effect of heart orientation on high frequency QRS components in multiple bandwidths

Reduced power of high frequency (HF) oscillations inside the QRS complex reflects ischemic pathology in the heart. In order to show spatial and frequency dependencies, we examined the effect of heart orientation on power of high frequency components under normal and ischemia condition within various frequency bands. Root mean square (RMS) of the signal in QRS region within frequency bands from 150 Hz to 550 Hz and heart rotation around longitudinal axes (360°) were computed from four rabbit isolated hearts. Experimental protocol included control, ischemic and reperfusion phases. This pilot study shows that RMS level of HF signal in non-ischemic heart differs within lead orientation and its maximum lies in a region around specific angle. Relative decrease in RMS value also depends on lead position. When depicted in spatial-frequency plane with polar coordinates, these relative changes contributes to specific patterns under both normal and ischemic conditions, which should be further examined.