Asymmetry of Characteristics of the Right-Left Hemodynamic Balance of Microcirculation in the Temporal Skin Areas of the Head in Young Male and Female Subjects.

The indices of asymmetry of microcirculation in the skin of the temporal areas of the head in young male and female subjects were studied. In 20 healthy volunteers (10 men and 10 women, age 18-19 years), synchronous measurements of the microcirculation of the skin of the symmetrical temporal areas of the head were carried out by laser Doppler flowmetry. The coefficients of asymmetry of regression relationships between perfusion changes in each side and initial perfusion values in both the same and opposite sides, the distribution function of perfusion asymmetry coefficients, and variability of perfusion in the studied areas were analyzed. The sex differences of the measured characteristics of asymmetry were revealed. In men, the distribution functions of perfusion asymmetry are pointed, with positive excesses, and in women they were flat, with negative excesses. In female subjects, the contribution of the right microcirculatory bed to the right-left hemodynamic balance was higher. These findings support the hypothesis on greater plasticity of the female brain in comparison with the male brain.

Comparative Analysis of Indicators of Microcirculation Stability in the Temporal Regions of the Head in Young Men and Women.

Indicators (markers) of microcirculation stability of the temporal regions of the head in young male and female subjects were studied. In 20 healthy volunteers aged 18-19 years (10 men and 10 women), synchronous measurements of the microcirculation of symmetrical temporal regions of the head were performed by laser Doppler flowmetry. Numerical values of stability markers (T1, T2, ζ) and parameters a1, a2, b1, b2 of the differential equation system describing oscillatory processes in the microcirculation system of the studied regions were obtained using the computational and experimental methodology developed by us earlier. It is shown that the right-left hemodynamic balance of microcirculation in men is maintained at the expense of the balance between the change in blood flow on the right and the initial value of blood flow on the left (coefficient b1) and in women, by the balance between the change in blood flow on the left and the initial value of blood flow on the right (coefficient a2). In women, the contribution of the right channel of the microcirculation to the right-left hemodynamic is significantly higher than in men. In general, the quantitative indicators (markers) of the stability of the microcirculation of the temporal regions of the head in women were higher than in men, which attests to higher stress resistance of the female organism in comparison with the male.

A Method for Assessing Stability of Regional Blood Circulation in Humans.

A new non-invasive method for assessing stability of functioning of the human regional circulatory system was developed. The method includes synchronous measurements of the level of cutaneous blood microcirculation of symmetrical areas of paired human organs by laser Doppler flowmetry and subsequent mathematical analysis of Dopplerograms using an original computational and experimental technique based on a mathematical model developed by us in the form of a system of differential equations describing experimental patterns of left-right asymmetry of oscillatory processes in the human regional circulatory system. The proposed method allows evaluating the reserve capabilities of the regional circulatory system in a patient and increases informative value of studies. This non-invasive method can be used in clinical practice to perform a personalized assessment of the stability of regional blood circulation and predict the risks of vascular pathologies.

Sex-Related Features of the Reactions of Microcirculation Parameters in Symmetrical Areas of the Human Head to Hypoxic Exposure.

We studied sex-related features of the microcirculation response of symmetrical areas of the human head to hypoxic loads. In 20 healthy volunteers (10 male and 10 female), short-term hypoxia was modeled using the ReOxy Cardio device (S. A. Aimediq). Microcirculation parameters were synchronously measured by laser Doppler flowmetry in the initial state and immediately after short-term hypoxic exposure. 3D graphs were constructed and regression equations were formulated that describe the relationships between changes in microcirculation on both sides of the measurement. Using a new method of geometric zoning, it was shown that the direction of reactions to hypoxia of the left microcirculatory bed is opposite in subjects of different sexes. In 80% male subjects, hypoxia led to an increase in perfusion on the left, in 20% - to a decrease. In female subjects, the picture was opposite: perfusion decreased in 90% and increased in 10% subjects. It can be assumed that these differences in the reactions of microcirculation to hypoxia in men and women are an additional confirmation of different structural and functional organization of the male and female brain, which leads to different resistance of males and females to external disturbing influences. The results of the study can be used in medical practice to develop methods for personalized assessments of circulatory disorders and differentiated approaches to the treatment of men and women with cardiovascular diseases.

Analysis of Changes in Microcirculation Parameters of Symmetrical Areas of the Human Head under Conditions of Hypoxic Influences.

The reactions of microcirculation parameters of symmetrical areas of the human head to hypoxic loads were studied. The study was conducted in 10 healthy male volunteers aged 18-19 years. Short-term hypoxia was modeled using a ReOxy Cardio normobaric device (S. A. Aimediq). Synchronous measurements of microcirculation parameters in symmetrical temporal regions of the head at the basal state and immediately after short-term hypoxic exposure were carried out by the method of laser Doppler flowmetry. We evaluated statistical characteristics of perfusion of both sides, as well as regression characteristics of the relationship between changes in the microcirculation parameters and the initial values of these parameters. It was shown that the reaction of the microcirculation parameters in symmetrical regions of the head to hypoxia depends on the initial microcirculation parameters in ipsi- and contralateral sides. 3D graphs were constructed and regression equations describing these relationships were formulated. A new method of geometric sensing is proposed, which allows predicting the direction of reactions to hypoxic effects. The obtained data illustrate the specificity of regulation of microcirculation of paired organs determined by the presence of functional asymmetry. A new method of geometric zoning is proposed, which allows solving the problems of personalized assessments of the state of the microcirculation system in patients.

Correlation-and-Spectral Analysis of Time Series for Microcirculatory Parameters in Vessels of Symmetrical Organs.

The correlation relationships between microcirculatory parameters were studied in vessels of symmetrical organs in humans. Parameters of microcirculation in healthy volunteers were measured by the method of laser Doppler flowmetry (LDF). LDF-signal transducers were placed symmetrically on the lower parts of the right and left shoulders (3 cm above the elbow bend). Correlations between various components of the amplitude-frequency spectrum for blood flow fluctuations (myogenic, neurogenic, respiratory, and cardiac) were evaluated on symmetrical sides. A significant correlation was found for the mean value of vascular perfusion on the right side with the neurogenic, myogenic, respiratory, and cardiac components on the same side. However, the mean value of vascular perfusion on the light side was interrelated only with the cardiac component. A positive correlation was revealed between the neurogenic and myogenic components on the left side. However, the neurogenic component on the right side was positively related to the myogenic component on the opposite side. Asymmetry of correlation relationships was also observed for the respiratory and cardiac components of study spectrum. Our results illustrate the specific regulation of microcirculatory blood flow in paired organs, which is associated with the existence of functional asymmetry. The physiological mechanisms for this asymmetry require further experimental and clinical studies.

[Analysis for the Persistence of Various Regimens of Heart Rate Dynamics by Computer Modeling].

A computer modeling revealed the following three regimens of heart rate dynamics: linear dynamics, "1st degree chaos", and "2nd degree chaos". This work was designed to study the persistence of these regimens by the method of Hurst. Our investigation showed that the Hurst index is highest for "2nd degree chaos" (H = 0,671 ± 0,028). The Hurst index for the "1st degree chaos" regimen was lower than that for "2nd degree chaos" (H = 0,473 ± 0,015). An increased persistence of cardiac rhythmogenesis in the "2nd degree chaos" regimen illustrates the non-stationarity and prognostic instability of these processes, which contributes to a high risk of heart diseases.

Correlation and spectral analysis of vascular tone regulator mechanisms in paired formations during postnatal ontogenesis in rats.

The study focused on the changes of microcirculation indices and components of the vascular tone of endothelial, neural, and myogenic nature in symmetrical skin sites of temples, forehead, auricles, scapulae, and groin during postnatal ontogeny. Initially, microcirculation indices in the symmetrical regions decreased to postnatal day 10, thereafter they surpassed the initial level at the age of 30 days. The endothelial, neural, and myogenic indices of vascular tone changed differently in the symmetrical left and right sites. On the right side, all indices increased by the postnatal day 21 ("redundancy" phase), and by postnatal day 30 surpassed the initial level by two times. On the left side, the redundancy phase manifested in the endothelial component on postnatal day 10, but to postnatal day 30 all three indices dropped below the initial level.

[Studying the Persistence of Blood Flow Oscillations in Rat Kidneys].

This work was designed to study the nonlinear dynamics of fluctuations in renal blood flow of rats under basal conditions and in the perturbed state. An intramuscular injection of aspirin in 0.9% physiological saline (0.5 mg per 100 g body weight) served as a perturbation factor. Capillary blood flow in the right kidney of a rat was measured by the method of laser Doppler flowmetry. The persistence of these time series was estimated by the Hurst method. Our study revealed the persistence of time series under basal conditions (Hurst index H = 0.817 ± 0.041). Statistical parameters of the perturbed series were shown to differ significantly from those observed in the initial state. However, the perturbed series remained persistent. The Hurst index for these series was H = 0.677 ± 0.057. A decrease in this index was insignificant (as compared to that for the baseline index).

[Computer modeling of parametric stability of heart rate dynamics during atrial fibrillation].

Parametric stability of heart rate dynamics during atrial fibrillation was estimated in relation to the change in the parameter of the curvature of delay function in the atrioventricular node. The study was conducted by the method of computer modeling. We investigated the dependence of characteristics of stability of heart rate dynamics from the number of independent ectopic sources in the atrium during fibrillation. The results show that the stability of heart rate dynamics decreases as the number of independent ectopic sources in the atrium and the parameter of the curvature of delay function in the atrioventricular node increase.

Nociceptive thresholds of the response to lipopolysaccharide injection into the limbic structures of the brain in rats.

Microinjections of LPS into the limbic structures of rat brain (dorsal hippocampus and caudal compartment of the cingulate fascicle) caused opposite effects on the nociceptive thresholds: injection into the dorsal hippocampus enhanced perception and reduced the emotional affective perception of pain, while injection into the cingulate fascicle reduced the perceptual and enhanced the emotional components of the nociceptive reaction. These results indicated specific involvement of these limbic structures in nociception modulation during induction of the immune response in CNS.

Mathematical modeling of atrial fibrillation.

Electrical activity of the heart during ventricular fibrillation was modeled as a sum of N independent pulse streams with various amplitude-frequency and phase characteristics. The data of computational experiments were compared with the results of actual physiological experiments on dogs. Identification of the model was performed using the least square method. The proposed technique provides the computer simulation for studies of the internal structure of irregularities of atrial fibrillation.

[Mathematical modeling of ventricular disturbances following atrial fibrillation].

The present study presents the results of mathematical and computer modeling of atrial fibrillation and ventricular disturbances following atrial fibrillation. The model is based on the assumption, that electric impulsation arriving on the atrioventricular node during atrial fibrillation is sum N of independent pulse streams with various amplitude-frequency and phase characteristics. With this model it becomes possible to investigate the dependence of nonlinear dynamics of PP and RR intervals on amplitude-frequency and phase characteristics pulse streams. Results of computer experiments are compared with real physiological experiments on rabbits. Identification of model was carried out by means of least-squares procedure.

[Computer modeling of ventricular fibrillation].

Electrical activity of a heart in ventricular fibrillation was modeled as a sum of independent pulse streams with various amplitude-frequency and phase characteristics. Results of computer experiments were compared with those of real physiological experiments on rabbits. Identification of the model was carried out by means of the least-squares procedure. The offered technique allows a computer model investigation of internal structure of irregularities of ventricular fibrillation.

[Analysis of the nonlinear heart rate dynamics by two-contour mathematical model].

Using a two-contour mathematical model, changes in the degree of heart rate variability induced by an increased extracardial impulsation in the sinoatrial node have been studied. The model is based on quantitative characteristics of impulse conduction in the cardiac conduction system. A mathematical and computer modeling revealed the following three regimes of heart rate variability: linear dynamics, the 1st-degree chaos, and the 2nd-degree chaos. Transitions between these regimes have been studied. A comparative analysis of the one- and two-contour models of heart rate regulation has been performed.

[Computer modeling of nonlinear heart rate dynamics during train extracardial impulsation in the sinoatrial node].

A computer model of excitation conduction in the heart has been employed to study the nonlinear heart rate dynamics under stress loads. The modeling was aimed to test the hypothesis explaining changes in the heart rate dynamics during nociceptive stress loads by the occurrence of train extracardial impulsation arriving at the sinoatrial node. The computer simulation shows that, with a particular set of parameters, the model imitates the dynamics of RR intervals observed in experiments. The present model provides a unified theoretical basis for further simulation of various types of ventricular disturbances under external extreme loads.

[The analysis of heart rate stability at stressor loads by method of mathematical modeling].

This study presents a mathematical model that enables to investigate the stability of heart rate dynamics at stressor loads. The model is based on quantitative characteristics of impulse conduction in the heart conducting system. Stressor load is modeled by fast neuronal imputation arriving on sinoatrial node. The model describes the phenomena observed at gradual increase of stressor intensity. Existence of a critical point of transition of heart rate dynamics from a stable (linear) to an unstable (chaotic) mode was demonstrated. The present model provides a unified platform for investigating stability of heart rate dynamics.

[Analysis of changes in heart rate variability during fast extracardial impulsation in the sinoatrial node].

It is known that fast extracardial impulsation in the sinoatrial node modifies the degree of heart rare variability. The present study presents theoretical and experimental investigation of this effect. Theoretical investigation is based on the mathematical modelling of impulse conduction in the cardiac conduction system. Experimental investigation on dogs revealed quantitative correlations between the frequency of extracardial impulsation in the sinoatrial node and changes of heart rate variability. Computer simulation shows that the mathematical model can account for most principal properties of the heart rate disturbances during fast extracardial impulsation in the sinoatrial node: transitions between different regimens of heart rate dynamics; increase in the delay of atrio-ventricular conduction; Wenkebach's periodicity.

[Mathematical model of heart rate variability].

The study presents a mathematical model of non-linear dynamics of the heart rate variability (HRV). The model is based on quantitative characteristics of pulse conduction in the heart conducting system: the delays of sinoatrial (SA) and atrioventricular (AV) pulse conduction and refractors periods of the SA and AV nodes. The model predicts heart rate disturbances in fast electric activity of the atria, increase in the delay of the AV conduction, the critical value of atrial period where transition to non-linear dynamics of the heart rate variability starts. The correlation between indexes of HRV and period of stimulation of atria for 1-contour cardiac control model has been demonstrated.

[Analysis of ECG in ventricular fibrillation in man and animals based on chaos theory]. / Analiz EKG pri fibrilliatsii zheludochkov u cheloveka i zhivotnykh na osnove teorii khaosa.

The methods of the chaos theory were used to estimate the degree of irregularity of ventricular fibrillation in human and experimental animals. To verify the hypothesis that the degree of chaos depends on the species of the living organisms, the parameters characterizing the degrees of irregularity of ventricular fibrillation were estimated and compared. The comparative analysis was performed using 32 fragments of electrocardiographic records from five patients with sudden ventricular fibrillation bouts and 215 episodes of induced fibrillation in 17 animals. It was shown that fibrillation in human and animals has a different degree of regularity and different values of the chaotic component. The highest values of chaos were recorded in dogs, the lowest degree of chaos was observed in human. Rabbits and rats are intermediate, between dogs and humans. The fractuality of the structure-function organization of myocardium is discussed.