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Biomedical subjects

V E Vorob'ev

Publications and source records attributed to V E Vorob'ev.

16 recordsLinked to original sources
PubMed2003

[Dynamics of local oxygen consumption an extraction under the condition of altered oxygen turnover in humans during head-down bed rest].

Invasive and non-invasive measurements were used to evaluate methods of correcting oxygen consumption and extraction within the local circulation in bedrested human subjects. For the first time demonstrated was the vanity of attempts to improve O2 supply to the human peripheral tissues by re-establishment of the circulating blood volume and increasing oxygen content in the affluent blood. The reason can be that HD bed rest impacts the ability of peripheral tissues to augment consumption of the surplus oxygen. The experiment showed that preliminary infusion of an antihypoxant (gamma-hydroxibutyric acid) recovers this ability even in case of abundant oxygen. Based on results of the investigation, oxygen supply correction can be considered as a way to improve (when necessary) oxygen supply to the human peripheral tissues during HD bed rest.

Adult↗
PubMedDate not supplied

[Changes in oxygen supply and utilization in head-down tilted humans].

Generalized data on the oxygen transport function of blood in human subjects during head-down tilt (HDT) collected with invasive and non-invasive methods point it that oxygen utilization by the systemic blood circulation does not reflect O2 utilization by the local one. After a week in HDT, local O2 utilization was found increased. A largely normal O2 content and pressure in arterial blood, significant decreases of these parameters in peripheral venous blood, and a concurrent slight growth of lactate are indicative of local circulatory hypoxia in blood flowing out of the arms of HDT subjects. Findings of the microgravity simulation studies bring up the necessity to control local oxygen supply in humans who for some reasons lack standard countermeasures during space flight.

Adult↗
PubMedDate not supplied

[The effect of hypothermia and oxygenation on the cardiorespiratory system in man exposed to experimental weightlessness].

It has been established that hypothermia in experimental weightlessness, as compared to normal conditions, was characterized by a considerably smaller deficit of erythrocytes in the energy balance and reduced gas exchange level, despite unidirectional changes in hemodynamic parameters. Unlike in hypothermia, an increase in oxygen concentration in the inhaled gas mixture had no noticeable effect on the parameters of the cardiorespiratory system studied.

Adult↗
PubMedDate not supplied

[Metabolic changes in simulated weightlessness].

8 healthy subjects participated in 2 series of experiments on the comparative studies of two techniques of respiratory therapy employing multicomponent anesthesia during controlled lung ventilation in normal conditions and in experimental weightlessness. It has been established that experimental weightlessness, as compared to normal conditions of controlled lung ventilation, was more favourable for the maintenance of effective energy exchange in erythrocytes and tissue O2 consumption. Both techniques of respiratory therapy during controlled lung ventilation are recommended in these conditions.

Adult↗
PubMedDate not supplied

[Changes in regional pulmonary hemodynamics and levels of vasoactive substances in man in a state of antiorthostatic hypokinesia].

A comparative evaluation of rheographic changes in regional pulmonary hemodynamics and renin-angiotensin and kinin-kallikrein activities was carried out on 9 volunteers exposed to antiorthostatic hypokinesia (-8 degrees) for 14 days. It was found that pulmonary circulation shifted in the apical direction due to increase in arterial tonicity and phasic variations of venous lumen. During the study blood renin increased significantly (P less than 0.05) whereas prekallikrein and kallikrein inhibitor varied insignificantly. It was concluded that the renin-angiotensin system played and important role in the changes of functional topography of pulmonary circulation in simulated microgravity conditions.

Aprotinin↗
PubMedDate not supplied

[Sensitivity of the respiratory regulatory apparatus to CO2 under simulated space flight conditions].

Using the rebreathing method, CO2 sensitivity of the respiration regulation system was investigated during a year-long enclosure study and head-down tilt tests of varying duration (up to 120 days). During the exposures CO2 and H+ were built up in the body. In the course of the enclosure study CO2 sensitivity was reduced. During bed rest experiments this parameter changed differently: it increased on day 7 and significantly decreased on days 55 to 100. These findings show that respiration regulation may vary markedly and indicate that it is worthwhile to carry out similar investigations in an actual space flight.

Adult↗
PubMedDate not supplied

[Clinico-physiological aspects of the tissue oxygen supply of the human body during head-down tilt hypokinesia].

In three antiorthostatic hypokinesia studies of varying duration gas exchange, central and regional hemodynamics were investigated. The hypokinetic effect on oxygen changes in the human body was evaluated by comparing the above results with biochemical data. It is concluded that bed rested subjects developed hypoxic changes of mixed circulatory-respiratory type. When oxygen supply changes drastically under the conditions that were simulated in our study, it is recommended to use oxygen therapy.

Bed Rest↗
PubMedDate not supplied

[Energy metabolism in the erythrocytes of humans exposed to anti-orthostatic hypokinesia].

Energy metabolism in red blood cells of men exposed to antiorthostatic hypokinesia (-8 degrees) was investigated. It was found that during this exposure erythrocytes synthesized organic phosphates such as diphosphoglyceric acid (2,3-DPG), ATP and ADP that were similar in terms of their effect on hemoglobin affinity for oxygen. On hypokinesia day 6, when the oxygen concentration in the erythrocyte environment increased, the content of the above phosphates also grew. It can therefore be concluded that glucose metabolism in erythrocytes of test subjects exposed to antiorthostatic hypokinesia is implemented via enhanced interaction between glycolytic and pentose-phosphate pathways.

2,3-Diphosphoglycerate↗
PubMedDate not supplied

[Status of metabolism and peripheral circulation in man during antiorthostatic hypokinesia].

Metabolism and peripheral circulation were investigated in head-down tilt tests of varying duration. The greatest changes were seen on test day 30 when the subjects showed venous hyperoxia, lower oxygen arterio-venous difference and a significant (p less than 0.05) decrease of oxygen tension in arterial blood and oxygen utilization in tissues (p less than 0.05). At the same time the subjects exhibited an increase in Pi and lactate and a maximum growth of 2,3-diphosphoglyceric acid (p less than 0.05). This exposure seems to produce a discrepancy between oxygen supply and oxygen requirements in tissues which gives rise to secondary tissue hypoxia. It is believed that the basic cause of these changes is disordered oxygen transport from blood to tissues.

2,3-Diphosphoglycerate↗
PubMedDate not supplied

[Changes in regional hemodynamics and gas exchange in healthy males after moderate blood loss and blood reinfusion in response to antiorthostatic hypokinesia].

Nine healthy male test subjects were exposed for 7 days to head-down tilting. Within 2 hours after exposure 500 ml of blood were withdrawn. This reduced pulse blood filling of all lung compartments, particularly upper (P less than 0.05) compartments, and decreased slightly finger circulation. The blood losses were then substituted but 2 hours after blood reinfusion the rheographic parameters of pulmonary circulation were still lower than before blood losses. In arterial blood pCO2 remained lower (P less than 0.05) and the deficiency of bases increased (P less than 0.05). It can be concluded that in the above situation blood reinfusion in the amount exceeding blood losses should be viewed adequate. On the basis of the results obtained increased blood content of the lungs in the course of head-down tilt can be interpreted as a reflex mechanism of blood pooling in the body.

Blood Transfusion, Autologous↗
PubMedDate not supplied

[Effect of 120-day antiorthostatic hypokinesia on gas exchange and pulmonary circulation in humans].

Parameters of gas exchange and pulmonary circulation were measured in five healthy test subjects during 120-day head-down tilt test and early recovery. During the first half of the bed rest study CO2 tension in arterial blood increased significantly. During the second half of the study oxygen and carbon dioxide tension decreased significantly. The mechanisms of these changes are discussed.

Carbon Dioxide↗
PubMedDate not supplied

[Effect of head-down-tilt hypokinesia on pulmonary blood flow and gas exchange].

The purpose of the study was to investigate gas exchange and lung perfusion during 14-day head-down tilt and immediately thereafter. During head-down tilting pulmonary circulation increased, as suggested by zonal rheography of the lungs and by ECG (increase in the PII-III amplitude and width by 1-2 mm and 0.01-0.02 s, respectively). A significant decrease in O2 tension and a slight increase in CO2 tension of the arterial blood were detected. Immediately post-test pulmonary circulation declined and metabolic acidosis developed simultaneously. Our findings suggest that drugs reducing pulmonary hypertension can be recommended for emergency medical aid in space flight.

Acid-Base Equilibrium↗
PubMedDate not supplied

[Human external respiratory function and blood acid-base balance during prolonged antiorthostatic hypokinesia and during the recovery period].

The study of external respiration and acid-base equilibrium of blood of 35 test subjects exposed to 49-day head-down (-4 degrees) tilting and of 6 test subjects exposed to 182-day head-down (-4 degrees) tilting demonstrated a trend for a decrease in the respiration rate, lung ventilation, oxygen consumption, and a relative increase in the exhalation time. With respect to the arterialized blood gases, a significant decrease in PaO2, an increase in PaCO2 and in the O2 alveolar-arterial difference were seen during the 49-day head-down tilting. During the 182-day head-down tilting a further increase in the CO2 arterio-alveolar difference was noted. These changes suggest shifts of the ventilation-perfusion ration in the lungs and, probably, disturbances of central regulation of respiration induced by head-down tilting. During the recovery period the above changes diminished gradually and disappeared by the 14th and 30th day after the 49- and 182-day head-down tilting, respectively.

Acid-Base Equilibrium↗