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Baroreflex function in children and adolescents with overweight and obesity.
Comenius University Martin
Department of Physiology, Comenius University
Andrea Calkovska, Prof. MD PhD
Michal Javorka, Assoc.Prof. MD PhD
Type of Research Project
- Clinical Project with Laboratory work
What is the background of the project?
Abnormalities of cardiovascular regulation in obesity are associated with higher risk of cardiovascular morbidity and mortality in adulthood. Currently, there is only limited information about cardiovascular system dysregulation in children and adolescents evaluated from noninvasive recording of biological signals. Therefore, the multidisciplinary and complex approach can contribute to explanation of cardiovascular dysregulation pathomechanisms and to early diagnosis and prevention of complications.
The heart rate oscillates spontaneously and the analysis of these oscillations could provide an important information about the cardiovascular control system involved in their generation.
Mature physiological control system is composed of the network of nervous and humoral feedback loops (with time delay) resulting in complex, apparently irregular and unpredictable system output - in our case we focus on heart rate variability - that can be recorded and analysed. In contrast, the loss of irregularity and complexity of the signal indicates maladaptation of organism.
Nonlinear analysis can be powerful tool for description of biosignal characteristics and - in this way - for characterization of systems involved in their generation. In contrast to conventional methods quantifying the magnitude of variability, methods based on nonlinear dynamics are focused on qualitative properies of time series (e.g. complexity) and can provide supplementary information independent of linear methods. In addition, several epidemiological studies have proved higher prognostic value of various nonlinear parameters compared to conventional methods. In biosignal analysis, no single analytical tool can describe all signal and system properties ? there is an effort to analyse various aspects of signal by battery of parameters - including linear ones. The aim of the project: The heart rate oscillates spontaneously and the analysis of these oscillations could provide an important information about the cardiovascular control system involved in their generation.
What is the aim of the project?
The main objective of this project is to detect and study early abnormalities of cardiovascular dysregulation in obese children and adolescents by heart rate variability analysis, to apply novel nonlinear mathematical methods for the early diagnosis and quantification of cardiovascular dysregulation, and to evaluate the effectiveness of nonpharmacological therapy.
What techniques and methods are used?
Used Techniques: The project is focused on the application of biosignal analysis methods to heart rate time series. The following parameters will be used in our proposed project: 1. Sample entropy (SampEn) - a measure of regularity and quantifies unpredictability of fluctuations in given time series and complexity of dynamical system output. Lower entropy values are a sign of increased autonomy of subsystems involved in parameter control. In contrast, SampEn is increased with increasing number and strength of subsystems connections. SampEn can be regarded as a measure of isolation and feedback interconnections within various complex systems. Empirical observations confirmed that low values of entropy are associated with aging and diseases, and that normal physiological system manifests itself with increased complexity. 2. Multiscale entropy (MSE) - for the analysis of meaningful complexity of oscillation on various time scales (from one to several tens of heart beats). This method was shown to be the most sensitive method for detection of early heart rate and blood pressure dysregulation in young patients with Type 1 diabetes mellitus. 3. Symbolic dynamics parameters - to assess dynamical changes of physiological parameters by analysis of simplified (coarse grained) time series. These parameters are based on transformation of time series into symbolic sequences using several symbols from given alphabet. Coarse grained signal can provide useful information about dynamical system generating it. Most frequently, its subsequent analysis is performed by various parameters derived from information theory (Shannon and Renyi entropies, Lempel-Ziv complexity, etc.). Usually, resulting parameters describe the complexity of underlying dynamical system. 4. Recurrence plot measures - recurrence plot method is based on analysis of reccurences (basic feature of nonlinear deterministic systems - the state closely approaches previous state of the system after several time steps). Recurrence plot can be analysed by recurrence quantitative analysis with parameters as percetage of recurrence, determinism, laminarity, etc. Basic infrastructure for study of cardiovascular parameters oscillations is concentrated in the 'Centre for diagnosis of functional disorders in children and adolescents' - common laboratory of Institute of Physiology and Clinic of Children and Adolescents. Presently, laboratory is equipped with devices for R-R intervals (ECG) recording for HRV analysis (VarCor PF6 and NihonKohden Cardiofax ECG-9620), for continuous blood pressure recording (Finometer device and sufficiently fast computers for sophisticated mathematical analysis.
What is the role of the student?
What are the tasks expected to be accomplished by the student?
will to work in a laboratory
Will there be any theoretical teaching provided (preliminary readings, lectures, courses, seminars etc)
What is expected from the student at the end of the research exchange? What will be the general outcome of the student?
- No specific outcome is expected
What skills are required of the student? Is there any special knowledge or a certain level of studies needed?
- creativity - basic knowledge on cardiovascular physiology focused mostly on cardiovascular system control - mathematical skills on the high school level
Are there any legal limitations in the student’s involvement
Type of students accepted
This project accepts: - Medical students
- Reduced short-term complexity of heart rate and blood pressure dynamics in patients with diabetes mellitus type 1: multiscale entropy analysis. Trunkvalterova Z; Javorka M; Tonhajzerova I; Javorkova J; Lazarova Z; Javorka K; Baumert M. Physiol Meas. 2008 Jul;29(7):817-28.
- Cardio-respiratory interaction and autonomic dysfunction in obesity. Tonhajzerova I; Javorka M; Trunkvalterova Z; Chroma O; Javorkova J; Lazarova Z; Ciljakova M; Javorka K. J Physiol Pharmacol. 2008 Dec;59 Suppl 6:709-18.
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