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Biomedical subjects

V P Katuntsev

Publications and source records attributed to V P Katuntsev.

At least 19 recordsLinked to original sources
PubMed2004

The main results of EVA medical support on the Mir Space Station.

The aim of this paper is to review the main results of medical support of 78 two-person extravehicular activities (EVAs) which have been conducted in the Mir Space Program. Thirty-six male crewmembers participated in these EVAs. Maximum length of a space walk was equal to 7 h 14 min. The total duration of all space walks reached 717.1 man-hours. The maximum frequency of EVA's execution was 10 per year. Most of the EVAs (67) have been performed at mission elapsed time ranging from 31 to 180 days. The oxygen atmosphere of the Orlan space suit with a pressure of 40 kPa in combination with the normobaric cabin environment and a short (30 min) oxygen prebreathe protocol have minimized the risk of decompression sickness (DCS). There has been no incidence of DCS during performed EVAs. At the peak activity, metabolic rates and heart rates increased up to 9.9-13 kcal/min and 150-174 min-1, respectively. The medical problems have centred on feeling of moderate overcooling during a rest period in a shadow after the high physical loads, episodes with tachycardia accompanied by cardiac rhythm disorders at the moments of emotional stress, pains in the muscles and general fatigue after the end of a hard EVA. All of the EVAs have been completed safely.

Aerospace Medicine↗
PubMed2001

[The assessment of the risk of altitude decompression sickness during simulation of repeated (with 12 hour interval) exits into open space].

Purpose of the investigation was to assess contribution of repeated (with a 12-hr interval) decompression to the risk of altitude decompression sickness (ADS) by simulation of 6-hr extravehicular activities (EVA) of space crewmembers in altitude chamber. The protocol included "ascents" of 6 essentially healthy male subjects at the age of 24 to 51 to the altitude of 7,600 m (37 kPa) following 30-min prebreathing (elimination of nitrogen from the body by breathing pure oxygen through a mask at the ambient pressure of 73 kPa = 2,600 m). Each subject participated in 2 experimental exposures: first initial and then repeated decompression. None of 24 "ascents" produced clinical signs of ADS. Comparison of the data concerning frequency and time points of detection by ultrasonic Doppler equipment of gas bubbles (GB) in the venous bed during decompression with initial, maximal and mean values of US signal intensity failed to state a significant difference between them. Data of the investigation were confronted with anticipated length of GB dispersion in body tissues.

Adult↗
PubMed2001

[Prevention of altitude decompression sickness during simulation of egress from the cabin of space vehicle with hypobaric artificial atmosphere].

Based on the proposed semiempiric nomograms, the study was aimed at selection and investigation of normoxic N2-O2 hypobaric atmosphere (HA) at 93-73 kPa, and evaluation of effectiveness of the gas mixture against the altitude decompression sickness (ADS) during 6-hr simulation of extravehicular activities at 37 kPa without prebreathing. Subjects were 22 healthy males from 20 to 50 yr. old. In all, 115 experiments were performed. Twenty-four hours in HA at 93 kPa and subsequent transition to 37 kPa led up to development of ADS symptoms by one subject in one of 27 experiments (3.7%), and emergence of venous gas bubbles (USI) with the intensity of 2, 70, and 19 points by the Spenser scale in 9 experiments (33.3%). Lower HA pressures (86 kPa, 80 kPa and 73 kPa) did not give rise to ADS though the occurrence of venous GB distinctly tended downward (30.6%, 14.3% and 11.8%) and so did the intensity of their entry into the pulmonary circulation (2, 40, 18 points; 1, 80, 19 points, and 2, 00, 15 points, respectively). Minimal ADS risk was observed in HA at 80 kPa and 73 kPa and did not reach 4% at the confidence level of 95%.

Adult↗
PubMed2000

[Classification of altitude decompression sickness].

The article is devoted to the discussion of principles of and approaches to classification of altitude decompression sickness (DCS), one of the most methodically formidable aspects of the problem. Based on his own multiyear experience in altitude DCS investigations and critical review of literature, the author reasons his concept of clinical classification of altitude DCS. The author's concept places emphasis on obligatory consideration of three stages in DCS development: A--pre-disease (the premorbid syndrome), B--uncomplicated (light) and C--complicated (severe) forms. The objective sign of the premorbid state is "silent" gas bubbles in organism detectable by ultrasonic devices. Signs of uncomplicated altitude DCS are musculoarticular pains, local edema and skin itching. Complicated altitude DCS is diagnosed by systemic (respiratory, neurological and cardiovascular) disorders.

Altitude Sickness↗
PubMed1999

[The monitoring of gas bubbles with a pulsed Doppler ultrasonic locator in humans working in a space suit].

Presented are results of gas bubbles monitoring in decompressed humans with the use of an ultrasonic pulse-Doppler locator (PDL). Unlike the classic Doppler bubbles detectors with continuous US emission, PDL is adjusted for reception of echo from a chosen volume of the right ventricle cavity; thus, the clutter due to cardiac beats and human locomotion is successfully rejected. During simulation of Russian EVAs, venous gas bubbles were detected in 3 out of 5 experiments with test-subjects clothed in everyday wear and in 2 out of 3 experiments with suited test-subjects.

Adult↗
PubMed1998

[Analysis of decompression safety during extravehicular activity of astronauts in the light of probability theory].

Objectives of the study were comparative assessment of the risk of decompression sickness (DCS) in human subjects during shirt-sleeve simulation of extravehicular activity (EVA) following Russian and U.S. protocols, and analysis of causes of the difference between real and simulated EVA decompression safety. To this end, DCS risk during exposure to a sing-step decompression was estimated with an original method. According to the method, DCS incidence is determined by distribution of nucleation efficacy index (z) in the worst body tissues and its critical values (zm) as a function of initial nitrogen tension in these tissues and final ambient pressure post decompression. Gaussian distribution of z values was calculated basing on results of the DCS risk evaluation on the U.S. EVA protocol in an unsuited chamber test with various pre-breath procedures (Conkin et al., 1987). Half-time of nitrogen washout from the worst tissues was presumed to be 480 min. Calculated DCS risk during short-sleeve EVA simulation by the Russian and U.S. protocols with identical physical loading made up 19.2% and 23.4%, respectively. Effects of the working spacesuit pressure, spacesuit rigidity, metabolic rates during operations in EVA space suit, transcutaneous nitrogen exchange in the oxygen atmosphere of space suit, microgravity, analgesics, short compression due to spacesuit leak tests on the eye of EVA are discussed. Data of the study illustrate and advocate for high decompression safety of current Russian and U.S. EVA protocols.

Astronauts↗
PubMed1998

[Fatty acid composition of the lipids in human blood plasma and erythrocyte membranes during simulation of extravehicular activities of cosmonauts].

Dynamics of the lipoacidic content of total plasma lipids and erythtocyte membranes was studied in 32 experiments with ten apparently healthy male subjects aged 27 to 41 years who were exposed to repeated decompression from the normal ground down to 40-35 kPa. For two hours of exposure to lowered pressure the subjects were breathing pure oxygen in mask and performing incremental physical work mimicking loading of the upper extremities of cosmonauts doing extravehicular activities (EVA) at the energy cost of 3 kcal/min. Decompression sessions were repeated with intervals from 3 to 5 days. In seven experiments, the subjects developed symptoms of the decompression sickness (DCS). Penetration of gas bubbles (GB) into the pulmonary artery was registered in 27 cases (84.4%). In 24 cases maximal intensity of the US signals from GB reached 3 to 4 Spencer's points. No changes in the lipidoacidic content of blood plasma or erythrocyte membranes were determined following the first exposure to decompression. BY the onset of repeated decompression, total number of lipids in erythrocyte membranes decreased from 54.6 to 40.4 mg% in the group of subjects who had not displayed DCS symptoms (n = 5) and from 51.2 to 35.2 mg% (p < 0.05) in the group of subjects with DCS symptoms (n = 5). In the subjects with DCS, polyunsaturated linoleic acid (18:2) tended to decrease against the upward trend of saturated fatty acids (16:0, 18:0). In these subjects, arachidonic acid in erythrocyte membranes (20:4) decreased following each decompression exposure and significantly increased (p < 0.05) in-between. In both groups, blood plasma showed slight fluctuations in the lipoacidic contents. These data suggest that exposure to the variety of the EVA-simulating factors may entail quite distinct but reversible modifications in the lipid metabolism in blood and the structural/functional state of erythrocyte membranes. The most marked alterations were observed in the subjects with the DCS symptoms during high intensity of US signals from GB in the venous blood flow.

Adult↗
PubMed1998

[Decompression sickness-one of the vital problems of aerospace medicine].

The author reviews the literature on decompression sickness (DCS) constituting one of the major problems of aerospace medicine. He speculates on the terms describing this health condition and offers the retrospective of hypothesised causes for DCS development. The paper outlines main DCS symptoms and reports statistics on the DCS incidence rate in flying personnel when piloting aircraft and training in altitude chambers, and in volunteered test-subjects during physiological experiments with simulated ascents in order to mimic the extravehicular activities of cosmonauts and to test the altitude gear. Underlined is the value of publications by many Russian and foreign investigators who contributed significantly to development of the scientific and applied aspects of this problem. The currently available and theoretically possible countermeasures against DCS in cosmonauts during EVA are considered.

Aerospace Medicine↗
PubMed1976

[Influence of prolonged hypokinesia on the water and fat composition of the human body].

A study was made of a combined action of prolonged hypokinesia (period - up to 30-49 days) and of different position of persons under trial (healthy men) to the gravitation vector on the body composition. Changes in total water content in the organism largely depended not on the limited mobility, but on the body position in space. In antiorthostatic position of persons under trial water "elimination" occurred chiefly during the first several days. The "lean mass of the body" decreased as a result of prolonged hypokinesia, and water content fell in it; but water content was rapidly restored with the restoration of the motor activity.

Body Water↗
PubMedDate not supplied

Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity.

Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p<0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.

Adult↗
PubMedDate not supplied

[The ultrasonic location of gas bubbles in the human bloodstream during work in a spacesuit].

The results of testing a procedure of ultrasonic location of the gas bubbles (GB) in man during space suit operations to simulate an extravehicular activity (EVA) are presented. Doppler echotachocardiograph "Rhythm" operating at ultrasonic frequency of 1.76 mHz was used as a GB detector. The device "Rhythm" integrated with a special flat transducer of 23 mm in diameter and 4 mm in width was positioned on the subject chest above the pulmonary artery projection. During 4-6 hour human operations while wearing pressurized (276-290 mm Hg) space suit, in 7 of 12 tests performed a stable and qualitative signal of the arterial blood flow in the lungs was recorded. In case of an unstable signal, in order that its quality be improved the posture of test subject was changed and the signal was recorded during a short-term expired breath-holding. Cardiac GB formation was noted during 6 tests in 2 subjects. The first GBs appeared at the 30th, 33rd, 70th, 111th, 114th and 180th minute after producing an operating reduced pressure in space suit. The time of GB detection on the average was 89.7 min. The maximum intensity of GB signal was 3-4 scores on Spencer's scale, but altitude decompression sickness symptoms did not develop in the test subjects. The risk of developing the altitude decompression sickness as opposed to the results of control experiments without use of space suit is discussed.

Adult↗
PubMedDate not supplied

[Central and general hemodynamics in healthy persons during simulated weightlessness].

The pumping and contractile functions of the left ventricle were investigated during combined exposure to water immersion and head-down tilt (at -6 degrees) that simulated microgravity. This 7-day exposure caused noticeable changes in central and systemic circulation which developed as a function of time. It is assumed that the deficiency of venous blood return seen on test days 1-3 was a compensatory response to initial blood displacement which was induced by a reduction of the circulating blood volume. The reduction was in turn a result of responses from volumoreceptors of the heart and intrathoracic vessels to "excessive" intrathoracic blood volume.

Adult↗
PubMedDate not supplied

[Comparison of direct and indirect methods of determining cardiac output].

In anesthetized dogs cardiac output was measured directly (by the method of Fick and by electromagnetic flowmetry) and indirectly (by the method of Bremser-Ranke and by rheography). The measurements were carried out before and after drug tests. The absolute values of cardiac output at rest differed depending on the method used. After the drug test all the methods revealed distinctly changes in cardiac output. A good correlation between flowmetric and rheographic methods was demonstrated. In view of this, they can be recommended to be used in rapidly changing hemodynamic situations. The method of Bremser-Ranke proved more suitable for the processes developing within 30-40 sec.

Animals↗
PubMedDate not supplied

[Detection of gas bubbles in the pulmonary artery and aorta of dogs by ultrasonic echography after intravenous infusion of air].

The transducer and receiving amplifier of a standard ultrasonic echocardiograph were modified to develop a device for detecting unmasked echocardiographic images of gas bubbles in blood vessels. This device was employed to detect gas bubbles passing from the venous to the arterial bed via lungs in anesthesized and thoracotomized dogs during air intravenous infusion. Gas bubbles entered the aorta when the dose of infused airw as 12-15 ml. It is postulated that gas bubbles formed in the animal and human body during decompression may pass from the venous into the arterial bed not only through shunts but also through lung capillaries.

Air↗
PubMedDate not supplied

[Ultrasonic echolocation of soft tissues in dogs during decompression].

Ultrasonic location of femoral soft tissues of anesthetized dogs was performed using a modified unit UZKAP-3. The animals were exposed to 0.5 mPa for 2 hours and then to decompression to sea level pressure. The concomitant echographic changes pointed to the formation of extra- and intravascular gas bubbles in the above tissues. The bubbles could be identified visually in the nearest echographic band because the instrumentation used made it possible to eliminate the background image of structural inhomogeneities of the tissue layer.

Animals↗