The estimation of microcirculation state in cerebrovascular disorders by data of laser Doppler flowmetry and hemorheological parameters

The study was aimed to evaluate microvascular blood flow and theological blood properties in healthy volunteers (n = 27) and patients with cerebral accident (n = 30). To study cutaneous blood flow we used the multifunctional laser analyzer of blood microcirculation LAKK (LAZMA, Moscow) with spectrophotometric channel and wavelet analysis of blood flow oscillations. Viscosity of the whole blood, plasma, RBC aggregability and deformability were assessed. Results: microcirculation index was by 25% (p < 0.05) lower in patients compared to the control group. Computing amplitude-frequency range of blood flow oscillations revealed notable changes in the blood flow regulation mechanisms under cerebrovascular accident: the amplitudes of all active rhythms (endothelial, neurogenic and myogenic ones) were increased. In spite of such activization of regulatory mechanisms, aimed to keep essential blood supply to tissue, index of specific oxygen consumption by tissue was decreased by 21% (p < 0.05) under cerebrovascular disorders. Blood rheological properties in patients group were impaired compared to the healthy group: blood viscosity was increased because of elevated plasma viscosity, increased RBS aggreagation and decreased erythrocyte deformability. Thus, our results demonstrated the decrease of tissue perfusion, activization of vasodilating mechanisms, impaired blood rheology and the decrease of oxygen supply to tissue in patients with cerebrovascular accident. Statistical analysis revealed a number of significant correlations between the hemorheological parameters and passive rhythms of microcirculation in norm. In patients blood viscosity correlated to the amplitude of active regulatory rhythms (endothelial, neurogenic and myogenic oscillations). Close interralations between rheological and microcirculation parameters testified the important role of hemorheological factors in maintenance of microvascular blood flow and oxygen delivery to tissue.     

Age-dependent characteristics of the skin peripheral blood flow oscillations by nonlinear dynamics methods in humans

Study of peripheral microhaemodynamics was carried out with laser Doppler flowmetry in healthy volunteers of different age groups. The ageing changes in the state of the skin peripheral blood flow, in the functioning of separate links and regulatory systems ofmicrovascular bed have been estimated in terms of relative entropy and fractal dimension values. The revealed significant age-dependent decrease of relative entropy values in the respiratory rhythm ranges, the neurogenic and myogenic activities yielded some evidence concerning the reduction of the microcirculation system chaotic changes within these frequency ranges during the ageing. The significant increase of fractal dimension values in the ranges of cardio-rhythm and the endothelial activity in the oldest group with the mean age of 77 years indicated that the structural complexity of the oscillations in these frequency ranges increased during ageing.     

Assessment of the changes in regulatory systems of human's skin blood flow during local heating

The mechanisms of thermal regulation of skin blood flow during local heating to 35, 40 and 45 'C have been studied by the method of laser Doppler flowmetry in healthy volunteers. To estimate the state of microvascular bed the continuous wavelet-transform spectral analysis has been used. The amplitudes of fluxmotions in the range of blood flow active modulation significantly increase during local heating to 35 degrees C. The amplitudes of blood flow oscillations in the ranges of cardiorhythm and respiratory rhythm increase during local heating to 40 degrees C. The high amplitude oscillations in the range of myogenic activity are maintained. The amplitude of oscillations in the range of endothelial activity distinctly decreases and the oscillations in the range of neurogenic activity are inhibited. Local heating to 45 degrees C results in a significant decreasing of the oscillation amplitudes in the range of myogenic activity, and the amplitudes of cardio- and respiratory spectral components amount to their peak values among the temperatures of local heating under study.     

Estimation of the microcirculation state in cerebrovascular disorders using laser doppler flowmetry data and hemorheological parameters

The microcirculation state was assessed in the group of patients with ischemic stroke (n = 30) and the control group of healthy individuals (n = 27) using laser Doppler flowmetry and the wavelet analysis of the amplitude-frequency range of microvascular blood flow oscillations combined with absorption spectroscopy. The hemorheological parameters (blood and plasma viscosity, the degree of red blood cell aggregability and deformability) were assessed in both groups, as were their correlations with the microcirculation parameters. Decreased tissue perfusion (by 25%) and specific oxygen consumption (by 21%) were revealed in a cerebrovascular accident. Changes in the tone-forming regulatory mechanisms of microcirculation of vasodilating nature (decreased microvascular tone, activation of the secretory function of endothelium) may be regarded as a compensatory reaction aimed at maintaining the blood supply of organs and tissues in stroke. The blood viscosity increase in patients due to the plasma viscosity increase and increased red blood cell aggregability and their decreased deformability cause the blood flow to slow down and the wall shear stress to increase, which activates the endothelial secretory function and vasodilation of microvessels. Correlation between the rheological parameters and the passive (respiratory and cardiac) rhythm amplitudes was observed in the control group. In patients, the hemorheological parameters were correlated with the characteristics of the active factors of microvascular blood flow modulation (endothelial, neurogenic, and myogenic), which confirms the role of changed blood properties and regulatory tone-forming mechanisms in the maintenance of tissue perfusion in cerbrovascular accidents.     

Phase synchronization of skin blood flow oscillations in humans under asymmetric local heating

The hypothesis is proposed that an external local stimulus may cause a change in the phase relationships of oscillations in the peripheral skin blood flow of contralateral extremities. To test this assumption, the wavelet phase coherence of skin blood flow oscillations of the left and right forearms of 18 healthy volunteers of both sexes at rest and in response to unilateral local heating was investigated. An area of the skin of the left forearm was exposed to heat and the native blood perfusion in an area of the skin of the right forearm was recorded simultaneously. It was shown that an asymmetric local change of skin perfusion led to a significant change in the phase relationships of the blood flow oscillations in all the analyzed frequency ranges. A significant reduction of phase synchronization of oscillations of skin blood flow in the range of endothelial, neurogenic, and myogenic activity, as well as in the range of respiratory rhythm was revealed. In contrast, in the range of the cardiac rhythm, a significant increase in phase synchronization of the oscillations of the blood flow of contralateral skin areas of the forearm was detected.     

Age-related differences in the dynamics of the skin blood flow oscillations during postocclusive reactive hyperemia

Age-related changes in peripheral microcirculation were studied using laser Doppler flowmetry in 60 apparently healthy subjects. The response of microcirculation to short-term ischemia was studied using the occlusion test. Changes in the amplitude of the peripheral blood flow oscillations were determined using time-amplitude analysis based on continuous adaptive wavelet filtration. The oscillation amplitude in the frequency range of the heart rate was found to reach the maximum with a delay after the removal of the occlusion, whereas in the range of the respiratory rhythm, no delay was observed. The hyperemic response to short-term ischemia is assumed to develop under the predominant influence of the arterial-arteriolar component, whereas the dynamics of amplitude oscillations in the range of the respiratory rhythm is a result of the devastation of the venular component after removal of occlusion. In response to short-term ischemia, the maximum oscillation amplitudes of myogenic, neurogenic, and endothelial rhythms decreased with age, which demonstrates the restriction of the regulatory control of the peripheral blood flow by the corresponding systems.     

Blood flow oscillations at a frequency of about 0.1 Hz in skin microvessels do not reflect the sympathetic regulation of their tone

Wavelet analysis of blood flow oscillations recorded with laser Doppler flowmetry in finger glabrous skin microvessels was carried out in 82 subjects with different variations in the syndromes of hand and foot sympathectomy and denervation. As distinct from the 0.02–0.046-Hz (about 0.03–0.04 Hz) blood flow oscillations in skin microvessels of sympathetic thermoregulatory origin, no relationship was found between the presence of 0.07–0.015 Hz (about 0.1 Hz) vasomotions in the wavelet spectrum and intactness of sympathetic innervation in the tissue region. The use of the myogenic band oscillation parameters, in particular, the amplitudes of vasomotions, for assessing the state of sympathetic thermoregulatory innervation determining the neurogenic tone of skin microvessels is not physiologically correct. The influence of local environmental factors on the vasomotion parameters confirms their local origin. The local perfusion pressure value significantly influenced the amplitude but not the frequency of vasomotions. The amplitude dominance of vasomotions was observed upon a decrease in perfusion pressure, whereas a marked increase in perfusion pressure or venous congestion resulted in a sharp depression of their amplitudes. Under the sympathectomy conditions, the oscillatory dynamic component of the arteriolar myogenic tone in the glabrous skin of the extremity acral zones is involved in the blood flow’s autoregulation. The presence of fine sensory fibers is necessary to carry out the dynamic autoregulation of the blood flow. Sensory nonmyelinated fibers and the trophic neuropeptides secreted by them not only initiate independent oscillations in the low-frequency (0.047–0.069 Hz) myogenic band, but also contribute to the normalized amplitudes of vasomotions being increased. At the same time, no appreciable influence of the sympathetic vasomotor activity and the corresponding influence of catecholamines on the amplitude and frequency of vasomotions was observed.     

Study of endothelium-dependent blood oscillations in the human skin microcirculatory bed

Cutaneous microcirculation parameters were studied with laser Doppler flowmetry in healthy volunteers. To investigate endothelial-dependent peripheral blood flow oscillations the iontophoresis of 1% acetylcholine solution was carried out. To estimate the contribution of rhythmical components in blood flow signal the continuous wavelet-transform spectral analysis was used. To reveal correlation between microcirculation parameters under study the correlation analysis was used. The microcirculation index was shown to be the factor producing cross-correlation dependences. The only positive significant correlation between the blood flow oscillation amplitude in the range of endothelial activity normalized to mean microcirculation index at rest and maximal microcirculation index during the iontophoresis of acetylcholine was revealed.     

Oscillatory processes in lymph microcirculation in the human skin

This study was the first to use laser Doppler flowmetry followed by wavelet analysis in order to estimate oscillations in lymph microcirculation in 30 subjects with (n = 13) or without (n = 17) edema of the distal part of the upper limb. Lymph flow in the human skin exhibited clear dominance of pacemaker phase oscillations in the frequency ranges of 0.021–0.042 and 0.016–0.035 Hz in the skin of the palm surface of the finger nail bone and in the skin of the forearm, respectively. Edema was associated with an increase in the peak frequencies and normalized maximum amplitudes (Al/Ml, where Al is the mean value of the maximum amplitude of phase oscillations, and Ml is the value of the averaged lymph flow expressed in perfusion units). Low-amplitude oscillations were recorded rarer in the myogenic, endothelial, and respiratory ranges. We did not find any cardiac pulse rhythm in the wavelet spectrum of the lymph flow. We did not find any interaction between the Al/Ml value and the skin temperature. In the group of subjects without edema, under physiological conditions only, we found a negative correlation between the Al/Ml value and the amplitudes of myogenous proper blood flow oscillations, which reflected the number of functional capillaries and activity of oxidative metabolism in the tissue. In the group with edema, we did not find any correlations between the indices of lymph flow and blood flow. The values of normalized amplitude and frequency of phase oscillations may be used as efficient diagnostic tools in the studies on lymph microcirculation.     

Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation

Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K _p indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (ΔBRS with ΔMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow (K-index with ΔMPPG; r _s=−0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect. An erratum to this article can be found at     

Seasonal variations in the myocardial infarction incidence and possible effects of geomagnetic micropulsations on the cardiovascular system in humans

The analysis of the ambulance calls in Moscow, related to myocardial infarction (85.000 events), sudden death (71.700 events), and hypertension crises (165.500 events) over the period of 1979-1981 demonstrated their clear seasonal variations with a profound summer minimum and a winter maximum. The same results were obtained in the analysis of statistical monthly data on sudden death from infarction in Bulgaria over the period of 15 years (1970-1985). However, there are a great number of clinical and statistical studies confirming the rises in the incidence of myocardial infarction, hypertension crise, and sudden death during geomagnetic disturbances, which have maximum occurrence near equinox, not in winter. In order to explain this contradiction, we suggested that one of critical factors that affect the human cardiovascular system is geomagnetic micropulsations Pc1 having the frequency comparable with the frequency of heart rate beatings and winter maximum in their occurrence. The results of a comparative analysis of data of ambulance calls in Moscow related to myocardial infarction and sudden death and the catalog of Pc1 observations at the geophysical observatory "Borok" (Yaroslavl region) are presented. It is shown that in approximately 70% of days with an anomalously large number of ambulance calls related to myocardial infarction, Pc1 micropulsations have been registered. The probability of simultaneous occurrence of myocardial infarction and Pc1 in the winter season was 1.5 times greater than their accidental coincidence. Moreover, it was found that in winter the effects of magnetic storms and Pc1 IM(A) were much higher than in summer. We suggested that one of possible reasons for the seasonal variations in the occurrence of myocardial infarction is an increase in the production of the pineal hormone melatonin in winter which leads to an unstable state of the human organism and an increase in its sensitivity to the effect of geomagnetic pulsations.     

The influence of the sympathetic innervation on the skin microvascular tone and blood flow oscillations

The influence of the sympathetic innervation on the tone of resistive vessels and blood flow oscillations was studied using laser Doppler flowmetry and skin thermography in 18 healthy subjects (before and after reflex cold and heat tests and local thermal testing), 42 patients with denervation syndromes caused by median nerve damage, and 10 patients with an acute stage of aseptic inflammation after radius fracture. The blood flow oscillations in the range of neurogenic sympathetic influences (0.02–0.052 Hz) supported by low-frequency sympathetic rhythms are an essential component of neurovascular interrelations. The importance of these oscillations is determined by their contribution to an increase in tissue perfusion owing to a decrease in the peripheral resistance and also by the leveling of drastic changes in blood flow and stabilization of microhemodynamics upon pronounced changes in the stationary tone. The high-and low-frequency (tonic and oscillatory, respectively) sympathetic rhythmic activities are expressed in two ways: (1) a synchronous increase or decrease in their amplitudes and (2) frequency dominance. The reactivity of the vessel smooth muscles is an important factor in maintaining the blood flow oscillations. Denervation decreases the oscillation amplitude in the neurogenic range. Under the conditions of local “inflammatory sympatholysis,” reflex tonic effects, rather than oscillatory ones, of the sympathetic impulses are mainly suppressed. An isolated evaluation of the blood flow oscillations in the neurogenic sympathetic range cannot be a measure of sympathetic activity. In studies on its functional state and evaluation of the neurogenic tone (NT) of resistive vessels, it is necessary to take into account the parameters of both stationary and oscillatory components of the NT.     

Influence of sensory peptidergic innervation on human skin blood flow oscillations in the range 0.047–0.069 Hz

Thirty-six healthy subjects and 65 patients with neurogenic inflammation (complex regional pain syndrome of the hand) or denervation syndromes (after median and ulnar nerve injuries or transplantation of denervated vascularized musculocutaneous autografts), as well as after thoracoscopic sympathectomy, underwent laser Doppler flowmetry with spectral wavelet analysis of the blood flow oscillations in cutaneous microvessels and thermography. It was shown that, along with maintenance of the blood flow oscillations of endothelial genesis, peptidergic sensory nerve fibers (SPFs) are involved in activating independent, including high-amplitude, oscillations in the myogenic range 0.047–0.069 Hz (an average of three to four oscillations per minute). The above-mentioned oscillations were recorded against the background of neurogenic inflammation and nociceptive activation of C afferents after nerve injuries, as well as in the course of functional tests in healthy subjects (the forearm skin electrostimulation test, capsaicin application). Sympathectomy and hyposympathicotonia contributed to their manifestation; they were not detected under the conditions of severe sensory-trophic skin denervation. The appearance of high-amplitude blood flow oscillations in human skin microvessels at a frequency of 0.047–0.069 Hz may serve as an objective criterion of SPF activation.     

Evaluation of the parameters of total,nutritive, and shunt blood flows in the skin microvasculature using laser Doppler flowmetry

Examination of 28 healthy subjects and 66 patients was performed using laser Doppler flowmetry (LDF) of the skin of fingers in the red and infrared ranges and wavelet analysis of microvascular blood flow oscillations. Formulas were suggested for the total (TF), nutritive (NF), and shunt (SF) local blood flows. TF = MI × A_c × A_n /(P_m × ), where MI is the microcirculation index in perfusion units (PU), A_n and A_c are the averaged maximum amplitudes of the neurogenic and cardiac rhythms (in PU), P_m is the mean arterial pressure (in mm Hg), and is the mean square deviation of the amplitude of blood flow oscillations (in PU). NF = TF/SP, where SP is the shunting parameter. SP = A_n/A_m, where A_m is the averaged maximum amplitude of the myogenic rhythm (in PU). SF = TF - NF. Significant positive relationships between the skin oxygenation and NF (red), temperature and TF (red), and blood flow measured by hydrogen clearance and TF (infrared) were revealed by comparison of the LDF parameters with polarographic and thermographic data. The advantages of the LDF parameters compared with the MI were shown, especially in skin denervation syndromes. The TF decreased in the case of complete anatomic rupture of the median nerve and increased in reflex sympathetic dystrophy, with both cases being accompanied by a deficit of the NF (red).Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 114–119.Original Russian Text Copyright © 2005 by Krupatkin.     

Dynamic oscillatory circuit of regulation of capillary hemodynamics

We used laser Doppler flowmetry with wavelet analysis of blood flow oscillations, computer capillaroscopy, and thermometry of the nail bed in 30 subjects to show an important role of the oscillatory circuit in the regulation of capillary hemodynamics, number of functioning capillaries, and linear and volumetric velocity of blood flow. The number of functioning capillaries is regulated by oscillations of myogenic and sensory peptidergic origin. The appearance of sensory oscillations, especially high-amplitude oscillations, is an adaptive neurotrophic mechanism that significantly increases the number of functioning capillaries and intensity of blood flow from arterioles to capillaries. The linear velocity of blood flow depends on both the tone of microvessels and changes in the dynamic component of blood pressure. Under conditions of skin hypoperfusion, the mean linear velocity of capillary blood flow may be inversely related to the extracapillary perfusion, including the amplitude of heart rate (A _h) and oscillations of the tone of precapillary sphincters, whereas under conditions of vasodilation and increased skin perfusion, it may be inversely related to the amplitude of arteriolar oscillations of endothelial or neurogenic sympathetic origin (A _maxe + n) and the shunting index. The A _h affects the linear velocity of blood flow in the arterial part of capillaries, whereas the A _maxe + n influences the same factor in the venous part. The contribution of oscillations to the regulation of the linear velocity varies depending on the perfusion and skin temperature. The resultant tone of distributing microvessels is determined by the competition between the stationary and oscillatory components. In addition to changes in the amplitude, the frequency of vasomotions may also be important. The regulatory importance of the oscillatory circuit is increased with a decrease in the skin blood flow.     

Estimation of age-related changes in the regulation of peripheral blood flow in humans

The age-dependent features in the state of skin microvascular bed has been studied with laser Doppler flowmetry in healthy volunteers of different age groups. To reveal the reaction of skin blood flow in response to short-term ischemia, the occlusive test has been carried out. To estimate the contribution of rhythmic components to blood flow signal, continuous wavelet-transform spectral analysis was used. Age-dependent increase of pulse-wave amplitude and decrease of respiratory wave amplitude reflecting age-dependent changes in functioning of arteriolar and venular links of microvascular bed have been observed at rest. In response to short-term ischemia the age-dependent reduction of reserve resources has been revealed in functioning of arteriolar link of microvascular bed. The reduction of activity of myogenic, neurogenic and endothelial regulation systems have been shown at rest in ageing.     

Characteristic features of microvascular responses of healthy humans to simulated emotional stress

Characteristic features of microvascular responses of healthy humans to simulated emotional stress (ES) were studied using computer-aided laser Doppler flowmetry. It was shown that, in ES, responses of individual regions of the microvasculature are relatively autonomous and different. In the nail bed, where the arteriolar and the arteriolovenular shunt tone depends on the neurogenic sympathoadrenal regulation, the responses are more pronounced than in the lower arm microvessels. The rearrangements of the nail bed and lower arm microvasculature in response to a simulated situation of ES are different, which is likely to be determined by both their different vascular architecture and other factors (the pressure gradient, metabolic requirements of tissues, etc.). It was established that the ES level determines an increase in the contributions of the neurogenic, myogenic, respiratory, and cardiac components to the modulation of the intensity of microcirculation, increasing the shunt value and the blood flow in microvessels.     

The Effects of Space and Terrestrial Weather Factors on Arterial Stiffness and Endothelial Function in Humans

A differential evolution algorithm was used to detect the biotropic influence of geomagnetic activity on several parameters of human vascular tone. Studies of the characteristics of vascular tone in healthy volunteers showed that arterial stiffness and endothelial function, as well as blood pressure and heart rate, depend on the geomagnetic and, in most cases, weather conditions. The pulse wave velocity (PWV) was measured to characterize the arterial stiffness and was found to be the most sensitive to the effects of space weather parameters. The strength of the effect of geomagnetic activity was for the first time observed to depend on the configuration of terrestrial weather parameters. A linear correlation between the K index of geomagnetic activity and PWV was estimated at r =–0.44 (p = 0.0003), although the relationship was detectable exclusively in the case of certain terrestrial weather parameters. Endothelial dysfunction and the pulse-rate response to variations in geomagnetic activity implicated nitrogen monoxide in body adaptation to variations in geomagnetic activity.

     

Seasonal variations in myocardial infarctions and the possible biotropic influence of short-period geomagnetic pulsations on the human cardiovascular system

Analysis of ambulance calls in Moscow during 1979–1981 reporting myocardial infarction (85 700 events), sudden death (71 700 events), and hypertension crises (165 500 events) shows the presence of clear seasonal variations with a deep summer minimum and a winter maximum. The same trend was upon analysis of monthly data on infarction mortality in Bulgaria over 15 years (1970–1985). One of the biotropic factors influencing the human cardiovascular system can be geomagnetic pulsations Pc1, agreeing in frequency with cardiac rhythms. In the seasonal trend, Pc1 have maximum intensity in winter. The comparison of data on ambulance calls in Moscow with the Pc1 observation data catalog revealed that, on ～70% of days, an abnormally large number of myocardial infarction calls was accompanied by the presence of Pc1; their concurrence was half again the chance expectation. Besides, it was determined that the biotropic influence of magnetic storms in winter was much higher than in summer. One of the plausible reasons of the winter infarction maximum could be seasonal variations in the production of the pineal hormone melatonin, which destabilized the organism and increased its sensitivity to geomagnetic disturbances attended by Pc1.     

Parameters of Microcirculation in Both Sexes at Different Ages

We have used laser Doppler flowmetry with wavelet analysis of the amplitude–frequency spectrum of blood flow oscillations to investigate the microcirculation and the mechanisms of its control in both sexes at different ages: junior school age, adolescence, and preadult age. It was shown that adolescents (both boys and girls) had more intense tissue perfusion and root-mean-square deviation of microcirculation as compared with junior school age. We observed an increase in the basal indexes of microcirculation in adolescents, which is caused by the activation of regulatory processes. In preadult girls, the microcirculatory flow index (MFI) was lower compared to adolescent girls; in preadult boys, MFI is higher compared to adolescent boys. It probably results from redistribution of influence between regulatory mechanisms. The analysis of the amplitude–frequency spectrum of preadults shows a decrease in oscillation amplitudes in all active and passive oscillation ranges compared to adolescents. Thus, we have detected the differences in microcirculation parameters and in the effects of active and passive regulatory factors of microcirculation. The findings are indicative of certain age-related changes in the microcirculation system.