Lenka Chladekova

Plasma agents in bio-decontamination by dc discharges in atmospheric air

Bio-decontamination of water and surfaces contaminated by bacteria (Salmonella typhimurium) was investigated in two types of positive dc discharges in atmospheric pressure air, in needle-to-plane geometry: the streamer corona and its transition to a novel regime called transient spark with short high current pulses of limited energy. Both generate a cold non-equilibrium plasma. Electro-spraying of treated water through a needle electrode was applied for the first time and resulted in fast bio-decontamination. Experiments providing separation of various biocidal plasma agents, along with the emission spectra and coupled with oxidation stress measurements in the cell membranes helped to better understand the mechanisms of microbial inactivation. The indirect exposure of contaminated surfaces to neutral active species was almost as efficient as the direct exposure to the plasma, whereas applying only UV radiation from the plasma had no biocidal effects. Radicals and reactive oxygen species were identified as dominant biocidal agents. (Some figures in this article are in colour only in the electronic version)

Multiscale time irreversibility of heart rate and blood pressure variability during orthostasis

Time irreversibility is a characteristic feature of non-equilibrium, complex systems such as the cardiovascular control mediated by the autonomic nervous system (ANS). Time irreversibility analysis of heart rate variability (HRV) and blood pressure variability (BPV) represents a new approach to assess cardiovascular regulatory mechanisms. The aim of this paper was to assess the changes in HRV and BPV irreversibility during the active orthostatic test (a balance of ANS shifted towards sympathetic predominance) in 28 healthy young subjects. We used three different time irreversibility indices-Portas, Guziks and Ehlers indices (P%, G% and E, respectively) derived from data segments containing 1000 beat-to-beat intervals on four timescales. We observed an increase in the HRV and a decrease in the BPV irreversibility during standing compared to the supine position. The postural change in irreversibility was confirmed by surrogate data analysis. The differences were more evident in G% and E than P% and for higher scale factors. Statistical analysis showed a close relationship between G% and E. Contrary to this, the association between P% and G% and P% and E was not proven. We conclude that time irreversibility of beat-to-beat HRV and BPV is significantly altered during orthostasis, implicating involvement of the autonomous nervous system in its generation.

Time Irreversibility of Heart Rate Oscillations During Orthostasis

Time Irreversibility of Heart Rate Oscillations During Orthostasis Introduction: Time irreversibility is a characteristic feature of non-equilibrium, complex systems involving cardiovascular control mediated by autonomic nervous system. Its analysis in heart rate variability (HRV) signal represents a new approach to assess cardiovascular regulatory mechanisms. The purpose of this paper was to assess the changes in various time irreversibility indices during the orthostatic test (a balance of autonomic nervous system shifted towards sympathetic predominance). In addition, we tested the behaviour of the selected irreversibility indices in relation to different lengths of analysed data and their mutual dependence. Methods: We examined the irreversibility of HRV time series obtained from 28 healthy young subjects recorded during 20 minutes in the supine position followed by 15 minutes in the standing position. We used three different time irreversibility indices - Portas, Guziks and Costas indices (P%, G% and A, respectively). The proposed irreversibility indices were derived from data segments containing 300, 600 and 1000 beat-to-beat intervals. Results: Two of three time irreversibility indices (P% and A) were sensitive to the shift in sympathovagal balance during the orthostatic challenge even when calculated from the shortest data length. Indices were relatively insensitive to data length - there were no significant differences in relation to data length. Despite the difference in algorithms for the calculation of indices P% and A, these are closely mathematically related and do not provide mutually independent information. Conclusion: We conclude that heart rate irreversibility indices are sensitive to the changes in autonomic tone after the orthostatic challenge even when derived from the 300 interbeat intervals. Portas index seems to be more sensitive to autonomic nervous balance shift compared to Guziks index. Costas index is closely related to P% and do not provide any additional information compared to other indices.

Hyperbilirubinemia and phototherapy in newborns: Effects on cardiac autonomic control

BACKGROUND Neonatal jaundice and its phototherapeutic treatment can lead to several side effects involving activation of autonomic control mechanisms. AIM The aims of this study are to investigate the autonomic nervous system changes in icteric neonates using heart rate variability (HRV) and to assess the effect of phototherapy on short-term heart rate dynamics as an indicator of autonomic nervous control of cardiovascular system. METHODS HRV recordings from 20 icteric full-term neonates before, during and after phototherapy and from 20 healthy controls were analyzed. In addition to traditional time and frequency domain measures, heart rate complexity parameters including normalized complexity index (NCI), normalized unpredictability index (NUPI), pattern classification indices (0V%, 1V%, 2LV%, 2UV%) and irreversibility index (P%) on four time scales were evaluated. All measures were derived from data segments of 1000 RR intervals. RESULTS The analysis revealed higher values of 1V%, 2LV%, and lower P% in neonates with hyperbilirubinemia compared to controls. While HRV magnitude did not change, mean heart rate increased during and after the phototherapy. Nonlinear analysis showed a decrease of complexity, unpredictability and pattern classification measures 2LV% and 2UV%. In contrast, 0V% and irreversibility index P% were increased during and at least 30min after phototherapy. CONCLUSION The results suggest a shifted autonomic balance in icteric neonates compared to the controls and its further alterations during phototherapy. As the nonlinear HRV parameters are independent of the linear methods, they can provide new information about the cardiac regulatory mechanisms and their changes in neonates.

Cardiovascular control during orthostatic and mental stress: Conditional entropy based analysis

The aim of this study was to characterize the changes in cardiovascular dynamics as a result of orthostatic and mental stress and their combination by linear and information domain analysis of heart rate and blood pressure oscillations. We recorded beat-to-beat RR intervals and systolic blood pressure values in 16 volunteers during mental arithmetics task and head-up tilt test and their simultaneous administration. The analysis included spectral measures and quantification of cardiovascular signals complexity and their mutual causal coupling. Our results demonstrated that orthostatic and mental stress challenges - despite similar heart rate and blood pressure changes - evoked different effects on cardiovascular control system. The novel conditional entropy based measures were sensitive to detect differences in heart rate and blood pressure dynamics responses evoked by mental stress in different body positions.

Time irreversibility of heart rate oscillations in newborns – Does it reflect system nonlinearity?

Abstract The aim of our research was to find out if the time irreversibility as a sign of specific class of nonlinear dynamics is present even in the newborns heart rate oscillations. Multiscale irreversibility indices (Portas index P %, Guzik index G % and Ehlers index E ) of the heart rate signals were computed in 20 healthy neonates. The presence of system nonlinearity was assessed by surrogate data analysis. The results of our analysis revealed asymmetrical nature of heart rate oscillations present in the majority of neonatal heart rate recordings. Moreover, time irreversibility index P % was able to detect shift of sympathovagal balance toward sympathetic dominance in newborns. Our findings support the concept of nonlinearity as a universal feature of the biological control system even in the early stage of the system maturation. This finding supports the application of nonlinear methods to heart rate variability analysis.

Quantification of Nonlinear Features in Cardiovascular Signals

Quantification of Nonlinear Features in Cardiovascular Signals The analysis of spontaneous heart rate and blood pressure oscillations under standardized conditions is a rapid, sensitive, noninvasive and reproducible tool for the assessment of cardiovascular autonomic dysfunction. Since the heart and vessels are controlled by a nonlinear deterministic system, measures derived from nonlinear systems theory are increasingly used in cardiovascular variability analysis. New nonlinear methods with applicability to real biological signals are continuously developed to quantify new aspects of cardiovascular signals with the potential to reveal subtle changes in the cardiovascular control system. Nonlinear measures provide complementary information about qualitative features of the analyzed signal. Since the analysis of variability magnitude and signal nonlinear characteristics (complexity, recurrences, time irreversibility, etc.) can provide independent information on cardiovascular system control, we suggest that simultaneous use of both groups of measures can increase the information value and thus improve the sensitivity and reliability of the detection and monitoring of the cardiovascular system dysregulation during various pathological conditions.

P01-359 - Heart rate variability in adolescent major depression

Introduction Impaired cardiac autonomic regulation is likely important contributor to a potential cardiac complications in major depression. The knowledge regarding the depression effect on cardiac regulation in adolescent age is limited. Aim was to study short-term heart rate variability (HRV) as an index of cardiac autonomic control in never-treated major depressive disorder (MDD) adolescent patients using linear and nonlinear methods related to depressive symptoms severity. Methods We have examined 20 MDD girls and 20 healthy age-matched girls at the age from 15 to 18 years. The ECG was recorded in three positions: supine - orthostasis - supine. The HRV was analyzed using linear (time and frequency analysis) and novel nonlinear (symbolic dynamics, time assymetry) methods. The severity of depressive symptoms was evaluated using the scales Montgomery-Asberg Depression Rating Scale (MADRS) and Children’s Depression Inventory (CDI). Results Several HRV linear and nonlinear parameters were significantly reduced in MDD group compared to controls in supine rest and during orthostasis. The HRV nonlinear analysis indices significantly correlated with depressive symptoms severity. Conclusions Linear and nonlinear analyses revealed reduced magnitude and complexity of the HRV indicating impaired neurocardiac regulation in adolescent major depression. In addition, new approach of HRV analysis using nonlinear methods provided important information about depressive symptoms severity and cardiac autonomic regulation relations.

Is the time irreversibility of heart rate present even in newborns

The aim of our research was to verify if the time irreversibility of heart rate oscillations exists even in the newborns. Multiscale irreversibility indices (Portas index P%, Guzik index G% and Ehlers index E) of the heart rate signals were computed in 20 healthy neonates. The presence of irreversibility and its origin in system nonlinearity was assessed by surrogate data analysis. The results were compared to irreversibility analysis of young adult heart rate signals. Surrogate data analysis revealed asymmetrical nature of the series present already in the neonatal age. Moreover Portas irreversibility index P% was significantly higher in newborns compared to adults indicating a shift in the sympatho-vagal balance in newborns towards sympathetic activity. The results of surrogate data analysis suggest an existence of the cardiovascular control system related time irreversibility in the majority of the recordings in both neonatal and adult groups.

PS-201a Hyperbilirubinemia And Phototherapy In Newborns Affect Cardiovascular Autonomic Control

Background Neonatal jaundice and its phototherapeutic treatment can lead to side effects involving activation of autonomic control mechanisms. Aim To investigate the autonomic nervous system changes in icteric neonates using heart rate variability (HRV) and to assess the effect of phototherapy on HRV as an indicator of autonomic nervous control of cardiovascular system. Methods HRV recordings of 20 icteric full-term neonates before, during and after the phototherapy and of 20 healthy controls were analysed. Besides traditional time and frequency domain measures, HRV complexity parameters including normalised complexity index (NCI), normalised unpredictability index (NUPI), pattern classification (0V%, 1V%, 2LV%, 2UV%) and multiscale irreversibility indices (P%, G%, E) were evaluated. All measures were derived from data segments of 1000 RR intervals. Results The analysis revealed higher values of 1V% and 2LV%, lower P% and reduced percentage of irreversible HRV recordings in the group of neonates with hyperbilirubinemia. While mean heart rate was increased during and after the phototherapy, HRV magnitude was not changed. Nonlinear analysis showed a decrease of complexity, unpredictability and pattern classification measures 2LV% and 2UV%. In contrast, 0V%, P% and the percentage of irreversible recordings were increased during and after the phototherapy. Conclusion The results suggest a shifted autonomic balance in icteric neonates compared to the controls and its further alterations during phototherapy. As the nonlinear HRV parameters are independent of the linear methods, they can provide new information about the cardiac regulatory mechanisms and their changes in neonates. Supported by grants VEGA N. 1/0223/12, 1/0059/13 and APVV-0235–12.