Hypercapnic hypoxia as a rehabilitation method for patients after ischemic stroke

INTRODUCTION

Experimental studies on animals have demonstrated a higher neuroprotective efficacy of hypercapnic hypoxia compared to normocapnic hypoxia. Respiratory training with hypercapnic hypoxia has shown a positive impact on the functional state of the nervous system in children with cerebral palsy (CP). It can be presumed that the combined effect of moderate hypercapnia and hypoxia will be promising for clinical application within the context of early rehabilitation after ischemic stroke.

METHODS

A randomized triple-blind placebo-controlled study was conducted on 102 patients with ischemic stroke, aged 63.07 ± 12.1 years. All patients were diagnosed with ischemic stroke based on neuroimaging criteria and/or clinical criteria within the 48-72 hour timeframe. The experimental group (n = 50) underwent daily respiratory training with hypercapnic hypoxia (FetCO2 5-6%, FetO2 15-16%) using the 'Carbonic' device for 7-11 sessions of 20 minutes each day during the treatment process. The control group (placebo, n = 52) underwent training on a similar device modified for breathing atmospheric air. Neurological examinations were conducted on all patients before the study and on the day after completing the training course.

RESULTS

The standard treatment demonstrated effectiveness in terms of neurological status scales in both groups. Intermittent exposure to hypercapnic hypoxia proved more effective in improving neurological function indicators in patients compared to the placebo group: NIHSS scale scores were 40% lower than in the placebo group (p < 0.001); mRS scale scores were 35% lower (p < 0.001); B-ADL-I and RMI indices were higher by 26% (p < 0.01) and 36% (p < 0.001), respectively; MoCA scale results were 13% higher (p < 0.05); HADS and BDI-II scale scores were lower by 35% (p < 0.05) and 25% (p < 0.05), respectively. The increase in MMSE scale scores in the intervention group was 54% higher (p < 0.001), and MoCA scale scores increased by 25% (p < 0.001).

CONCLUSION

Respiratory training with hypercapnic hypoxia improves the functional state of the nervous system in patients with ischemic stroke. After conducting further clarifying studies, hypercapnic hypoxia can be considered as an effective method of neurorehabilitation, which can be used as early as 48-72 hours after the onset of stroke.

Molecular Mechanisms of Neuroprotection after the Intermittent Exposures of Hypercapnic Hypoxia

The review introduces the stages of formation and experimental confirmation of the hypothesis regarding the mutual potentiation of neuroprotective effects of hypoxia and hypercapnia during their combined influence (hypercapnic hypoxia). The main focus is on the mechanisms and signaling pathways involved in the formation of ischemic tolerance in the brain during intermittent hypercapnic hypoxia. Importantly, the combined effect of hypoxia and hypercapnia exerts a more pronounced neuroprotective effect compared to their separate application. Some signaling systems are associated with the predominance of the hypoxic stimulus (HIF-1α, A1 receptors), while others (NF-κB, antioxidant activity, inhibition of apoptosis, maintenance of selective blood-brain barrier permeability) are mainly modulated by hypercapnia. Most of the molecular and cellular mechanisms involved in the formation of brain tolerance to ischemia are due to the contribution of both excess carbon dioxide and oxygen deficiency (ATP-dependent potassium channels, chaperones, endoplasmic reticulum stress, mitochondrial metabolism reprogramming). Overall, experimental studies indicate the dominance of hypercapnia in the neuroprotective effect of its combined action with hypoxia. Recent clinical studies have demonstrated the effectiveness of hypercapnic-hypoxic training in the treatment of childhood cerebral palsy and diabetic polyneuropathy in children. Combining hypercapnic hypoxia with pharmacological modulators of neuro/cardio/cytoprotection signaling pathways is likely to be promising for translating experimental research into clinical medicine.

[Positional deformity of the subclavian artery as a possible cause of subclavian steal syndrome]

Using the method of duplex scanning, we examined a total of 123 patients presenting with a deformity of the subclavian artery (SCA). We assessed the Doppler spectrum of blood flow in the zone of the SCA deformity, as well as in V2 and V4 segments of the ipsilateral vertebral artery (VA) at rest and in breath holding on inspiration. Deformity of the SCA was observed on the right in 91% of cases, on the left in 5%, and on both sides in 4%. Haemodynamic disorders in the ipsilateral VA as a change of the shape of the Doppler spectrum according to the type of steal syndrome were noted in 10.8% of cases, with a more pronounced impairment of blood flow at the intracranial level - in 78.6% of cases. It was determined that a deformity of the SCA was characterised by a decrease in angulation (up to complete straightening) and a reduction of the peak systolic velocity on deep inspiration, thus reflecting its positional nature. Patients with initial impairment of the Doppler spectrum in the VA demonstrated normalization of the spectrum on an intake of breath. Hence, the index of the peak systolic velocity of blood flow in the zone of the SCA deformity in combination with assessment of the Doppler spectrum in the ipsilateral VA on inhalation may be used for determining the haemodynamic significance of a deformity of the SCA.

Inhibition of Apoptosis is a Potential Way to Improving Ischemic Brain Tolerance in Combined Exposure to Hypercapnia and Hypoxia

We compared the intensity of apoptosis in the peri-infarction area of the brain after isolated and combined exposure to hypoxia and hypercapnia prior to focal ischemic stroke modeling. Hypoxia and hypercapnia reduced the number of TUNEL-positive cells in the peri-infarction area, and their combination was most effective in comparison with effects of isolated exposures. The maximum neuroprotective effect of combined exposure to hypoxia and hypercapnia in comparison with isolated exposures was determined by inhibition of apoptosis in the peri-infarction zone.

Stress of the Endoplasmic Reticulum of Neurons in Stroke Can Be Maximally Limited by Combined Exposure to Hypercapnia and Hypoxia

We studied the expression of chaperone GRP-78 and transcription factor NF-kB during the development of ischemic tolerance of the brain after combined and isolated exposure to hypoxia and hypercapnia. Combined exposure to hypoxia and hypercapnia maximally increased the expression of chaperone GRP-78 and transcription factor NF-kB, while the formation of ischemia-induced tolerance under conditions of hypercapnic hypoxia can be associated with activation of adaptive stress mechanisms in the endoplasmic reticulum. Under these conditions, hypercapnia in combination with hypoxia is a priority factor for activation of GRP-78 and transcription factor NF-kB.

[Hypercapnia--alternative hypoxia signal incentives to increase HIF-1α and erythropoietin in the brain]

Investigated the role of hypercapnic component in the mechanism of activation of HIF-1α and increase the synthesis of erythropoietin in the combined and the isolated impact of hypoxia and hypercapnia. It was found that the content of proteins of interest significantly increases both in isolated hypoxia and hypercapnia, and at their combined effect. Moreover, the hypercapnic hypoxia causes maximum activation of the synthesis and accumulation of erythropoietin HIF-1α, and permissive hypercapnia enhances their content more than hypoxic exposure.

[OPTIMAL HYPERCAPNIC HYPOXIA CONDITIONS FOR INCREASING RESISTANCE TO ACUTE HYPOXIA]

The study was focused on finding an optimal length of hypercapnia-hypoxia sessions of training resistance to acute hypoxia and looking for benefits from reoxygenation intervals and intermittent training over daytime. It turned out that 3 days of a 5-minute hypercapnia-hypoxia session per day improved resistance to acute hypoxia explicitly and that a 30-minute session increased resistance to the highest rate. Two training sessions per day are no better than one session. Hypercapnia-hypoxia training with reoxygenation intervals are the least effective in comparison to the other modes of training.

Deformity of subclavian artery as a cause of formation of vertebral subclavian steal syndrome

Presented herein are 3 clinical case reports concerning formation of vertebral subclavian steal syndrome in deformities of subclavian arteries. By means of duplex scanning, angiography and multispiral computed tomography it was shown that deformities of subclavian arteries in the first segment (proximal to the origin of the vertebral artery) with septal stenosing are accompanied by a typical dopplerographic picture_pattern of steal syndrome.

[The role of adenosine Al receptors and mitochondrial K+ATP channels in the mechanism of increasing the resistance to acute hypoxia in the combined effects of hypoxia and hypercapnia]

We studied the role of the role of mitoK+ATp channels and Al-adenosine receptor in the mechanism of increasing the resistance to acute hypoxia after hypoxic, hypercapnic and hypercapnic-hypoxic preconditioning. It is shown that mitochondrial ATP-sensitive potassium channels and Al-adenosine receptors, an important mechanism of preconditioning have a high value to increase the resistance to acute hypoxia/ischemia in the combined effect of hypoxia and hypercapnia. However, with regard to the adenosine receptor, this mechanism is realized without the participation hypercapnic component, which apparently starts neuroprotection without activation of the adenosine Al receptors.

[Cerebral blood flow and damage markers during ischemia/reperfusion of brain against a background of modulation of the kinin system's activity]

Cerebral hemodynamics' status under condition of experimental ischemia and following reperfusion of brain against a background of pharmacological modulation of kinins' formation, the kinin system's inhibition and depression of kinins' disruption was investigated by the method of hydrogenous clearance. The brain damage intensity during hypoperfusion of reperfusion period was measured by analyzing its damage markers. It was determined that the activation of kinins' formation by tripsin has a detrimental effect during ischemia/reperfusion of brain, producing an early development of hypoperfusion in reperfusion period, aggravating a brain damage. The depression of kinins' disruption by ACE-inhibitors leads to superfluous decreasing of local cerebral blood flow during hypoperfusion of reperfusion period. The inhibition of kinins' formation by contrykal improves the flow of reperfusion period, preventing the appearance of hypoperfusion and decreasing the brain damage intensity in comparison with a control group. On the whole an activation of the kinin system during ischemia/reperfusion of brain plays mostly pathogenetic role making worse the flow of reperfusion period and aggravating a brain damage.

[The role of VEGF, HSP-70 and protein S-100B in the potentiation effect of the neuroprotective effect of hypercapnic hypoxia]

Studied the role of VEGF, HSP-70 and S-100B in potentiating hypercapnia neuroprotective effect of hypoxia. Demonstrated that neuroprotective effects when exposed hypercapnic hypoxia-mediated protein synthesis increased S-100B, mainly due to the action of carbon dioxide, and not oxygen deficiency. Neuroprotective effects of HSP-70 due to hypoxia, but the combined effect of hypoxia and hypercapnia gives a significant increase in the synthesis of HSP-70 in comparison with the isolated effect of hypoxia. Vascularization activated equally as hypoxia and hypercapnia, without adding significant effects in combination. This suggests dominant effect hypercapnia, hypoxia compared in neuroprotection mechanisms related to protein S-100B, but not the protein VEGF, hypercapnia and potentiate the neuroprotective efficacy of hypoxia-related protein HSP-70.

[Comparative efficacy of hypoxia, hypercapnia and hypercapnic hypoxia increases body resistance to acute hypoxia in rats]

The relative efficiency of trainings with isolated hypoxia, hypercapnia and hypoxia in aggregate with hypercapnia in order to enhance the resistance of organism to the effect of an extreme hypoxia was studied. The combined effect of the hypoxia and hypercapnia was shown to influence more greatly in comparison with the effect of an isolated hypoxia. This effect was supported with an increase in the time of the loss position and the time of the animal's life under the condition of an extreme hypoxia. Also it is shown that the hypercapnia in a combination to a hypoxia makes dominating impact on formation of nonspecific resistance as the isolated hypercapnia enlarges indicators of nonspecific resistance, than the isolated hypoxia more effectively.

[Increased resistance to hypoxia under the effect of the mixture of herbs from the Altai]

We investigated the antihypoxic effect of herb mixture <<Vasofit>> from the Altai in an experiment with rats. This mixture of herbs contains bioflavonoids. Also, it has antioxidant, anti-inflammatory, antispasmodic, angioprotective and antiplatelet properties. The animals received decoction of herbs into the stomach through a tube. Courses lasted 3, 7, 14 and 21 days. Resistance to acute hypobaric hypoxia evaluated by time of animal life in modeling rise to a height of 11,500 meters above sea level. In result, a significant antihypoxic effect was observed in rats treated with decoction of herbs for 21 days. Shorter courses of treatment were not effective.

[Helical (spiral or swirling) blood flow in cardiovascular system]

In article covers theoretical preconditions for the hypothesis about helical (spiral or swirling) blood flow in cardiovascular system followed by its experimental corroboration. The role of the modern blood flow visualization methods--such as Color Doppler ultrasound and magnetic-resonance angiography--in registration and investigation of the regularities of the given phenomenon is described. The data describing the known parameters of helical blood flow--such as direction of the rotation and its quantitative parameters in large arteries--are given. The main hypotheses for flow screw mechanisms are considered from the point of view of cardiovascular system structural organization. Biological role of helical blood flow is discussed, in respect of which there are diametrically opposed points of view, which consider it as a physiological phenomenon on one side, and as a patogenetic factor of atherosclerosis development on the other.

[The response of cerebral blood flow and systemic arterial blood pressure to hypercapnia and hypocapnia in humans]

In 11 healthy volunteers 21 +/- 3.7 years old was monitored cerebral blood flow (CBF) by transcranial Doppler (TCD) of middle cerebral artery and mean hemodynamic arterial blood pressure (MAP) by continuous non-invasive measurement "beat-to-beat" at normocapnia, hypercapnia and hypocapnia. Hypercapnia was creating by rebreathing, hypocapnia was creating by spontaneous hyperventilation. The partial pressure of CO2 in alveolar air (PetCO2) was monitored by capnograph, embedded in the TCD-analyzer. During hypercapnia the velocity of CBF and PetCO2 were significantly increased already at 10 s, which was considerably earlier than the increase in the MAP (30 s). During hypocapnia velocity CBF and PetCO2 were significantly decreased at 10 s, and MAP was not changed. We have installed the threshold PetCO2 42 (41; 44) mm Hg, below which amplification CBF occurs at a constant MAP and reflects the true cerebrovascular reactivity to CO2.

[The mutation of genes of hemostasis system in patients with venous cerebral angiodystonia against the background of connective tissue dysplasia]

The examination was applied to sampling of 238 patients of younger age with neurologic symptomatology under connective tissue dysplasia and 46 healthy persons. The venous cerebral angiodystonia was diagnosed in 153 (64.3%) patients with connective tissue dysplasia. The results are confirmed by duplex analysis of cerebral and vertebral vessels. The mutations of genes of blood coagulation system (FV Leiden, FII, MTHFR, FVII and PAI-1) are established. They include combined (61.4%) and independent (23.5%) groups of mutation. Alongside with it, in 23 (19.6%) patients disorders of hemostasis are presented as von Willebrand factor deficiency and in 105 (89.7%) patients as decrease of aggregation function of thrombocytes and disorders of final coagulation stage of blood coagulation. The results of study indicate the equally frequent risk of thrombotic and hemorrhagic complications in patients with connective tissue dysplasia.

[Ultrasonographic assessment of carotid stenoses: methods, possibilities and limitation]

The results of a multicenter study have shown that the degree of carotid stenosis makes it possible to forecast cerebral ischaemia and is a principle index for choosing between conservative and surgical treatment. Many centres perform carotid revascularization based only on the data of duplex scanning. Presented in the review are methods of ultrasonographic assessment of the stenosis degree, their comparative characteristics and factors influencing the accuracy of assessing the stenosis degree. Also considered herein are possibilities of standardization of carrying out studies and formations of conclusions.

[The use of hypoxically hypercapnic training for children with the attention deficit syndrome and hyperactivity for the correction of school disadaptation problems]

The problem of rehabilitation of children with the attention deficit syndrome and hyperactivity remains unresolved despite a large number of relevant investigations. The comprehensive rehabilitation of such children requires the use of both medicamental and-non-medicamental factors. The objective of the present study was to address the problem of school disadaptation based on the improvement of memory and attention in children presenting with the attention deficit syndrome and hyperactivity by means of inclusion of hypoxically hypercapnic training in the program of comprehensive rehabilitation with the use ofa Karbonik respiratory training system. A method is described developed for the practical realization of this program and the results of its implementation are presented.

[Formation of vertebral-subclavian steal syndrome in abnormal origin of the left vertebral artery from the aortic ark]

Presented herein is a clinical case report concerning the formation of vertebral-subclavian steal syndrome combined with occlusion of the left subclavian artery and an abnormal origin of the left vertebral artery from the aortic arch. Duplex scanning data and angiography findings showed that the collateral compensation of haemocirculation in the upper extremity took place through the subclavian-vertebral collateral net. Doppler ultrasonography signs of the latent steal syndrome were revealed in the intracranial segment of the left vertebral artery and were confirmed by the findings of the reactive hyperthermia test. Balloon angioplasty with stenting of the 1st portion of the left subclavian artery resulted in normalization of the Doppler spectrum in the intracranial segment of the left vertebral artery.

[Treatment of chronic erosive gastroduodenitis in children with hypercapnic hypoxia]

Investigation of quality of life in pediatric patients--a simple, reliable and efficient way to assess the status of the child, which complements the clinical, laboratory and instrumental examination, which in turn helps to improve treatment outcomes. Given that the gastro-intestinal tract, the prevalence of the 2nd place among all the diseases of childhood, the definition of quality of life and its improvement in such patients is an integral part of treatment.

[Differential diagnosis of spasm and hypoplasia of the vertebral artery with ultrasound methods]

The aim of the study was to establish ultrasound criteria of the differentiation between functional and morphological vasoconstriction of the vertebral artery (VA) using hypercapnia test in patients with signs of vertebral-basilar insufficiency. The inclusion criteria were the presence of clinical symptoms of vertebral-basilar disturbances of circulation and small diameter of VA (< or =2.9 mm). Fifty patients, aged from 17 to 57 years, were studied. Based on the form of Doppler 's spectrum of the blood flow in the small VA, patients were stratified into three groups: normal (N spectrum), peak-like split (PS spectrum) and high-resistance low-speed (HL spectrum). The increment of diameter by 0.2 mm and more, i.e. the functional vasoconstriction (spasm) during hypercapnia, was characteristic of patients with PS and N spectrum. The ROC-analysis revealed that the absence of VA increment during hypercapnia is a highly specific (90.9%) predictor of morphological vasoconstriction of VA. Quantitative criteria of VA hypoplasia were specified as well. Ultrasound angioscanning in the combination with hypercapnia test allows differentiation with a high probability between functional (spasm) and morphological (hypoplasia) vasoconstriction of VA.

Dynamics of clinical semiotics in children with pathological tortuosity of internal carotid arteries in remote period after surgical management

The present study enrolling a total of eighty-eight 4-to-16-year-old children and adolescents was aimed at detailed elaboration and formalization of clinical signs of the internal carotid artery pathological kinking syndrome. To achieve these objectives, the authors carried out a comparative analysis of clinical manifestations of the disease in the surgically treated subjects (constituting the Surgery Group comprising 43 children and adolescents) and non-operated patients (making up the Comparison Group consisting of 45 age- and gender-matched subjects). There were no baseline differences in the incidence rate of clinical syndromes and symptoms between the groups of the would-be operated and conservatively treated patients. Also studied were the remote outcomes (1-to-12-year follow up) of surgical correction for pathological tortuosity of the internal carotid artery. The incidence rate of regression of neurological symptomatology along different clinical signs after surgery was shown to vary within a wide range from 11.6% to 96.3%. Resection of the proximal portion of the internal carotid artery with re-implantation into the old ostium turned out to be clinically effective in 90.0% of cases, with the haemodynamic efficacy amounting to 83.3%. Arteriolysis of the internal carotid artery rendered a clinical effect in 75% of cases, with a haemodynamical effect thereof equalling 25.0%. The decision as to the type of a surgical intervention to perform was primarily made based on the findings of angiography of the internal carotid artery. The operation of arteriolysis did not lead to deterioration of the child's condition.

Importance of the arterial pressure value for doppler assessment of carotid stenoses

Many centres appear to perform carotid endarterectomy solely based on the findings of duplex scanning. There are two fundamental methods aimed at assessing the stenosis degree during an altrasonographic study, i. e., planimetric examination and Doppler altrasonography. Doppler ultrasonographic criteria have an independentsignificance when the assessment of the stenosis degree in the ultruasonographic B-mode is complicated. However, the currently available guidelines on haemodynamic assessment of the stenosis degree are solely based on the parameters of local blood flow without taking into consideration the state of central haemodynamics. The present study has shown that blood flow in the region ofstenosis of the internal carotid arteries (ICAs) depends not only on the stenosis degree but on the value of systemic arterial pressure (AP) at examination. Based on the obtained findings, we worked out Doppler ultrasonographic criteria for ICA stenosis degree "by the area" corrected for the value of systemic AP. It was determined that using pulse AP increases their prognostic eficiency.

Cerebral hemodynamic reactions to low-intensity physical exercise

Cerebral hemodynamic reactions to light physical exercise increasing stepwise on a bicycle ergometer were studied in healthy young male subjects. Hemodynamic parameters were measured by transcranial Doppler ultrasonography from the middle cerebral artery (MCA) before the start of the study and during the last few seconds of each exercise step. Cerebral hemodynamic reactions to physical exercise were characterized by a significant increase in systolic blood flow rate in the middle cerebral artery only at exercise levels of about 0.25 W/kg body weight (90 rpm at 0 W/kg) with no further increase in the blood flow rate with increases in loading to 0.5 W/kg body weight. The mechanism stabilizing blood flow rate in the cerebral arteries as physical exercise increased and, thus, the mechanism of cerebral circulatory autoregulation consisted of a arterial pressure-dependent increase in regional cerebral vascular resistance. The threshold at which the cerebral blood flow rate autoregulatory mechanism was triggered in normal subjects corresponded to a loading of about 0.25 W/kg and a systolic arterial pressure of about 140-145 mmHg.

Kinin formation in the plasma and cerebral blood flow in under conditions of cerebral ischemia/reperfusion in rats during modulation of kinin system activity

Suppression of kininogenesis is an adaptive phenomenon in cerebral ischemia/reperfusion in rats aimed at elimination of the no-reflow phenomenon. Hyperkininogenesis and suppression of kinin destruction are pathogenetically significant, because they augment the manifestations of no-reflow phenomenon during reperfusion following ischemia.

[Arterial and venous brain reactivity in the acute period of brain concussion]

Arterial and venous brain reactivity has been studied in 38 patients in the acute period of brain concussion (BC) and 32 healthy volunteers using transcranial color duplex scanning of brain vessels. The assessment of arterial inflow was conducted for the medial brain artery (MBA) and that of venous outflow - for the basal vein (BV) of Rosenthal. Hyperkinetic and orthostatic probes were used for assessment of cerebrovascular reactivity. BC was not accompanied by marked changes of cerebral resting hemodynamic parameters. The increase of peak blood flow velocity in MBA in the acute period which is characteristic of the brain hyperinfusion was found in 20% of patients and that in BA compensating the disturbed outflow along the surface brain system - in 25% of patients. In normalcy, the brain venous reactivity to hypercapnia was higher than arterial one and that to orthostasis corresponded to the intensity of arterial changes. The lack of quantitative differences in the reaction of arterial and venous blood flow to hypercapnia and the predominance of venous reactivity value in orthostasis in patients with BC suggest the disturbance of venous tone regulation in these patients.

[Basic laws of blood screw motion in human common carotid arteries]

The basic laws of blood screw motion in common carotid arteries in people were determined by means of modern ultrasound techniques for the first time. 92 healthy adults, aged 18-30, were examined. The blood flow in the middle one-third of common carotid arteries was registered by means of Color Doppler Imaging and impulse Doppler with the help of ultrasound Medison 8000EX scanner by linear transducer of 5-9 MHz. The steady registration of blood screw motion in both common carotid arteries in Color Doppler Imaging regimen was observed in 54.3 % of cases. The direction of screw stream rotation in most cases (54%) was multi-directed: in the right common carotid artery it was right, in the left common carotid artery--left (48%), and in 6% of cases it was reverse. For 46% of cases blood rotation in both common carotid arteries was one-directed (26%--right, 20%--left). The velocity parameters of rotation component of blood motion were determined, maximum velocity being 19.68 +/- 5.84 cm/sec, minimum--4.57 +/- 2.89 cm/sec, average--7.48 +/- 2.49 cm/sec, angular--10.7 +/- 2.49 sec(-1). The rated velocity of blood cells motion in screw motion with regard of screw current lines to the vessel vertical axis makes up from 158.67 +/- 32.79 to 224.39 +/- 46.37 cm/sec.

[Cerebral hemodynamics response to low intensity physical exercise]

The aim of this research was to study the cerebral hemodynamics reaction to step increase of physical exercises intensity during bicycle ergometer test in young healthy male subjects. Hemodynamics parameters were registered with the transcranial Doppler ultrasonography of middle cerebral artery (MCA) prior to the study and during the last seconds of every step of physical exercise. Cerebral hemodynamics response to physical exercise was characterized by a significant increase of peak systolic blood velocity in the MCA up to 0.25 W/kg of the body weight (90 rpm with regard to 0 W/kg) without further increase of blood velocity in the same physical exercise becoming more intensive up to 0.5 W/kg of the body weight. The stabilization mechanism of blood velocity in cerebral arteries in case of physical exercise increase and, hence, the autoregulation mechanism of cerebral circulation means that the increase of regional cerebral vascular resistance depends on the value of arterial pressure. The autoregulation mechanism of cerebral circulation starts working with he exercise intensity of 0.25 W/kg and the value of systolic blood pressure about 140-145 mm Hg.

[Cerebral haemodynamics in long-term adaptation to hypercapnic hypoxia]

The intervals in hypercapnic hypoxia were accompanied by increase of the cerebral vascular resistance, by decline of the reactivity of cerebral vessels to hypercapnia, by increase of collector reserve and speed of self-verification of cerebral blood circulation. These changes are an important component of the increasing mechanism of the brain resisten to the cerebral ischemic under the influence of drills with hypercapnion hypoxia.

[Venous haemodynamics response to hypercapnia]

The authors' aim was to evaluate the response of the intracranial venous system to application of functional tests. In 46 healthy volunteers, the basal veins were examined using venous transcranial color-coded duplex sonography. We evaluated angle-corrected venous peak-systolic flow velocities (V(vb)) in response to hypercapnia (I group: 29 subjects) and the orthostatic test (II group: 17 subjects). We have found that hypercapnia inducesa significant increase of the flow velocities in the basal veins, on average 60 +/- 22.7% (p < 0.00001). The reaction prevents venous hyperaemia, i. e., significant increase of the cerebral blood flow volume and the drainage of the brain. In contrast to hypercapnia, the orthostatic test led to decrease in the flow velocities in the basal veins. The percentage of velocity decrease ranged from 16to 32% (p < 0.001). Posturally induced reduction of the venous flow volume prevents excessive drainage from the brain. Thus, we have shown that both tests can be used for evaluation of reactivity of the intracranial venous system and they can complement each other.

[Cerebral hemodynamic reaction to physical exercise of moderate intensity]

The aim of this research was to study the cerebral hemodynamic reaction to stepped increase of physical exercises during the bicycle ergometer test in 12 young healthy male patients. The starting value of exercise was 0.25 W/kg of the body weight, with the 0.25 W/kg increase at every subsequent step up to the value of 1.75 W/kg of the body weight. Hemodynamic parameters were registered with the Doppler ultrasonography of middle cerebral artery before the study, during the last 10 seconds of every step, and during the 3 minutes of restorative period with a 1-minute interval. The peak systolic blood flow increase in the middle cerebral artery was observed only as the result of low intensity exercises (0.25 W/kg of the body weight). The blood pressure (BP) restoration occurred by the end of the third minute of the rest, while the cerebral hemodynamic indices became normal during the first minute. The research revealed a correlation between increases of vascular resistance caused by physical exercises and the BP, and no correlation between increases of peak systolic blood flow and BP, which displays the phenomenon of cerebral circulation autoregulation.

[Assessment of therapeutic efficacy in thromboses of the inferior vena cava by means of colour duplex scanning]

A total of two hundred and twenty-eight 18-to-83-year-old patients diagnosed with thrombotic occlusion of the lower-limb deep veins were examined in order to evaluate the possibilities of colour duplex angioscanning as a method aimed at monitoring both the course of and efficacy of treatment for acute venous thrombosis, as well as at preventing thromboembolic complications. Studied were the localization, incidence rate, and complications of the course of various types of venous thrombosis. It was demonstrated that an uncomplicated course the disease was observed in more than 80% of cases. At the same time, using dynamic ultrasonic monitoring made it possible to promptly detect progression of the pathological process in 3.5% of cases, and to introduce due amendments in the treatment policy being carried out. Also shown were the possibilities of the colour duplex scanning (CDS) technique in assessing the outcomes of the endovascular prevention of pulmonary thromboembolism (PTE) by means of implantation of the cava filter. The CDS turned out efficient in diagnosing the development of such complications as dislocation of the cava-filter and thrombus formation in the area of the cava filter. It was determined that the terms of fixation of the embolus-hazardous (floating) thrombus varied from 6 days to 6 months, which is of great importance in selecting the optimal period for temporary endovascular prevention of PTE.

[Peculiarities of atherosclerotic injury of carotid arteries in patients with coronary artery disease with hyperhomocysteinemia]

Peculiarities of atherosclerotic injury of carotid arteries were studied in 47 patients with coronary artery disease in dependence of blood concentration of homocysteine. The patients were divided in 2 groups -- with homocysteine concentration more and less than 10 mmol/l, and in 4 groups, corresponding to quartiles of distribution of homocysteine in blood. Ultrasound method was used for assessment of carotid artery intima-media thickness (IMT), detection of presence and character of atherosclerotic plaques and estimation of degree of carotid artery narrowing. It was established that elevation of blood homocysteine concentration was accompanied with increase of IMT, number of atherosclerotic plaques, and. Positive correlation was found between homocysteine level and IMT (r=0.38, p<0.05), degree of narrowing of carotid arteries (r=0.47, p<0.05), character of atherosclerotic plaques (r=0.43, p<0.05).

[Response of cerebral hemodynamics to combined stress impacts]

Changes in cerebral hemodynamics (CH) was assessed with transcranial color duplex scanning in the middle cerebral artery (MSA) of 15 healthy male volunteers aged 20-23 years in response to psychoemotional stress (PES). The latter was induced by calculations, mild exercise (Martine's test), hypercapnia in inspiration of 6% CO2 and their various combinations. The results showed that a combined action of the stressors differs quantitatively and qualitatively from their isolated action. As a rule, in combination the stressors potentiated each other. The response of CH to a combined action of the stressors, PES and hypercapnia, in particular, may be also characterized by a prevalent effect of one of the stressors, in this case by a stronger action of hypercapnia.

Ultrasound criteria for embologenicity of venous thrombosis

Altogether 136 patients aged 17 to 79 years with a diagnosis of acute and subacute thrombosis of lower limb deep veins were examined by duplex scanning in order to derive the ultrasound criteria for embologenicity of inferior vena cava thrombosis. The authors evaluated thrombosis standing (from the emergence of the first clinical signs to its diagnosis), the length and site of the floating portion, the area of the transverse section of the thrombus, the character of the external contour, and the degree of thrombotic mass mobility. It has been established that: along with the generally accepted criteria for floating thrombi there is a number of the echographic characteristics which exert a significant effect on the probability of embolic complications; the degree of thrombotic mass mobility has a material effect on the incidence of thromboembolic complications and may be classified as insignificant, moderate and pronounced while embolic complications are largely present when the mobility of thrombotic masses is moderate or pronounced; the incidence of thromboembolic complications is significantly higher in the presence of a floating thrombus having uneven hypo- and isoechogenic contour and heterogeneous structure. The even hyperechogenic contour and homogeneous structure are common to the "organized thrombi", with the threat of their detachment being appreciably less. The differences have been demonstrated in the times of the fixation of the "non-organized" floating thrombi (heterogeneous, marked by the uneven external contour with the predominance of hypo- and isoechogenic areas) as compared to the cases when the thrombi were more "organized".

[The effect of different motor regimens modulating spontaneous activity on rat behavior]

A method was developed of non-stressful modulation of spontaneous motor activity of rats. Restraint of mobility was found to inhibit spontaneous activity. Physiological stimulation of muscle activity by means of complication of food-procuring behaviour was accompanied by increase of spontaneous activity. Physiological stimulation of motor activity was characterized by stability of orienting-exploratory behaviour, emotional reactivity, expression of "freedom response", the best learning and working abilities of the animals. Regimes with imposing or restriction of muscle activity favoured the inhibition of spontaneous activity and the decrease of efficiency of adaptive behaviour. Motor regimes accompanied by increase of spontaneous activity were found to be optimal for adaptive behaviour.

[Adaptability of patients to freely selected and forced physical exercise after myocardial infarction]

In 45 patients with myocardial infarction in the rehabilitative period in health resort centers, bicycle ergometric tests with forced routine continuously gradually increasing exercise or without forced graded exercise in accordance with the "free option" motor motivation test were performed at the beginning and at the end of treatment. The work performed at the beginning and at the end of treatment. The work performed with free option is characterized by substantial differences in its volume, duration, intensity, and rate. Free option exercise is submaximal, close to tolerant, but simultaneously shows lower values in heart rates, systolic blood pressure, "double product" and cost-effective index. The free option exercise test is a more sensitive indicator of alterations in the status of a patient with myocardial infarction during health resort rehabilitation.

[Neuroendocrine regulation under maximal and subjectively optimal physical loads]

The responses of neuroendocrine system to maximum and subjective-optimum physical loading were found to be similar in young men and characterized by activation of adrenocortical, somatotropic and thyroid functions, particularly under maximum loading. The subjective-optimum loading was dosed out by the subjects themselves, differentiated individually and averaged 62% of the maximum oxygen consumption. The parameters of subjective-optimum physical loading were close to the threshold level necessary to stimulate neuroendocrine system and ensure an increase of somatotropine, cortisole, thyroxine and aldosterone concentration in the blood.

[The effect of locomotor regimens of moderate intensity on spontaneous motor activity and resistance to acute hypoxic hypoxia in rats]

Long-term locomotive regimens of moderate intensity change the spontaneous locomotive activity (SLA). Hypokinesia leads to the SLA reduction whereas additional physical loads cause its increment, changing hypophyseal-adrenal system reactivity, too. Tolerance to hypoxic hypoxia under locomotive hypokinesia tends to lower.