Publications by authors named "Jan Hejda"

5 Publications

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Evaluation of Postural Stability Differences in the Elderly Through Recurrent Analysis.

Stud Health Technol Inform 2020 Sep;273:197-202

Faculty of Physical Culture, Palacky University Olomouc, trida Miru 117, Olomouc, Czech Republic.

Measuring the center of pressure (CoP) for a subject positioned on a force plate is one of the most commonly used tools to investigate balance. Several studies have proven a significant degradation of the body's stability after the age of 60. The conclusions, however, are based on a limited number of indicators and without systematic nonlinear analysis methods being used to evaluate the progression of CoP parameter values. Neither the change in CoP movement in subjects over 60 years of age nor the considerations of their body mass index (BMI) has been systematically evaluated by nonlinear methods so far. This study is based on one of the frequent methods for nonlinear evaluation - the Recurrent Quantification analysis. This article discusses the applicability of this method with regards to the evaluation of changes in postural stability of subjects over 60 years of age. Postural stability changes were evaluated using CoP motion and tested by the nonlinear method. For this research purpose, a group of 103 elderly women were selected and divided into age-respective groups of 60-69 years and 70-79 years old. Each age group was further divided into a subgroup of normal and overweight subjects according to their BMI. The following recurrent analysis parameters were employed in the evaluation of CoP motion in medial-lateral and anterior-posterior directions: determinism (DET), laminarity (LAM) and trapping time (TT). The results of the Wilcoxon test revealed a statistically significant difference between the values in parameters for the different age groups of overweight subjects almost in all the cases. Conversely, statistically significant differences between age groups rarely occurred in a subgroup of subjects with a normal BMI.
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http://dx.doi.org/10.3233/SHTI200639DOI Listing
September 2020

Automatic Telerehabilitation System in a Home Environment Using Computer Vision.

Stud Health Technol Inform 2020 Sep;273:142-148

Czech Technical University in Prague, Prague, Czech Republic.

In this paper, we follow up on research dealing with body tracking and motor rehabilitation. We describe the current situation in telerehabilitation in the home environment. Existing solutions do not allow wide adoption due to hardware requirements and complicated setup. We come with the possibility of telerehabilitation using only laptop or mobile web camera. Together with physiotherapists, we have compiled a set of complex motor exercises to show that the system can be practically used.
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http://dx.doi.org/10.3233/SHTI200629DOI Listing
September 2020

Control System of a Lower-Extremity Exoskeleton Based on the Artificial Neural Network.

Stud Health Technol Inform 2020 Sep;273:91-96

Faculty of Biomedical Engineering, Czech Technical University in Prague, Sitna sq. 3105 Kladno, Czech Republic.

A lower-extremity exoskeleton can facilitate the lower limbs' rehabilitation by providing additional structural support and strength. This article discusses the design and implementation of a functional prototype of lower extremity brace actuation and its wireless communication control system. The design provides supportive torque and increases the range of motion after complications reducing muscular strength. The control system prototype facilitates elevating a leg, gradually followed by standing and slow walking. The main control modalities are based on an Artificial Neural Network (ANN). The prototype's functionality was tested by time-angle graphs. The final prototype demonstrates the potential application of the ANN in the control system of exoskeletons for joint impairment therapy.
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http://dx.doi.org/10.3233/SHTI200620DOI Listing
September 2020

Influence of Artificially Generated Interocular Blur Difference on Fusion Stability Under Vergence Stress.

J Eye Mov Res 2019 Sep 11;12(4). Epub 2019 Sep 11.

Masaryk University, Faculty of Medicine, Dept. Pediatric Ophthalmology, Brno, Czech Republic.

The stability of fusion was evaluated by its breakage when interocular blur differences were presented under vergence demand to healthy subjects. We presumed that these blur differences cause suppression of the more blurred image (interocular blur suppression, IOBS), disrupt binocular fusion and suppressed eye leaves its forced vergent position. During dichoptic presentation of static grayscale images of natural scenes, the luminance contrast (mode B) or higher-spatial frequency content (mode C) or luminance contrast plus higher-spatial frequency content (mode A) were stepwise reduced in the image presented to the non-dominant eye. We studied the effect of these types of blur on fusion stability at various levels of the vergence demand. During the divergence demand, the fusion was disrupted with approximately half blur than during convergence. Various modes of blur influenced fusion differently. The mode C (isolated reduction of higher-spatial frequency content) violated fusion under the lowest vergence demand significantly more than either isolated or combined reduction of luminance contrast (mode B and A). According to our results, the imageĀ“s details (i.e. higher-spatial frequency content) protects binocular fusion from disruption by the lowest vergence demand.
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http://dx.doi.org/10.16910/jemr.12.4.4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7880136PMC
September 2019

Multi-lead vs single-lead T -T interval measurements for prediction of reperfusion ventricular tachyarrhythmias.

J Cardiovasc Electrophysiol 2019 10 21;30(10):2090-2097. Epub 2019 Aug 21.

Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia.

Introduction: Electrocardiographic T -T interval (Tp-Te) is a promising marker for the prediction of ventricular tachycardia and/or ventricular fibrillation (VT/VF). The study was aimed to compare single-lead vs multilead Tp-Te variables as VT/VF predictors in experimental ischemia/reperfusion model.

Methods And Results: Computer simulations were done using the ECGSIM model with an ischemic region set in anterior left ventricular apex. In 18 anesthetized cats, myocardial ischemia was induced by 30-minute ligation of left anterior descending coronary artery followed by reperfusion. Body surface ECGs in limb leads and modified precordial leads were recorded. Tp-Te was detected automatically in individual leads with a custom-designed parametric algorithm. Tp-Te dispersion and total Tp-Te were calculated as a difference between the maximal and minimal value of individual Tp-Te(s) and an interval between the earliest Tpeak and the latest Tend throughout all leads, respectively. Simulations showed that the increase of local, but not total, dispersion of repolarization characteristic for ischemic damage led to nonuniform shortening of T-peak times across 12 standard leads, which in turn resulted in the increase of single-lead Tp-Te(s), total Tp-Te and Tp-Te dispersion. Animals experienced VT/VF showed increased Tp-Te dispersion and total Tp-Te during reperfusion. In univariate logistic regression analysis, only the Tp-Te dispersion at the beginning of reperfusion was associated with the VT/VF incidence. According to ROC curve analysis, the optimal cut-off value of the Tp-Te dispersion was 17 ms (sensitivity 0.71, specificity 0.80).

Conclusions: The reperfusion VT/VFs were independently predicted by increased Tp-Te dispersion, which suggests the importance of multi-lead evaluation of Tp-Te intervals.
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http://dx.doi.org/10.1111/jce.14105DOI Listing
October 2019