[Prevention of altitude decompression sickness during simulation of egress from the cabin of space vehicle with hypobaric artificial atmosphere]. / Profilaktika vysotnoi dekompressionnoi bolezni pri imitatsii vykhodov iz kabiny kosmicheskogo korablia s gipobaricheskoi iskusstvennoi gazovoi atmosferoi.

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%.

[The assessment of the risk of altitude decompression sickness during simulation of repeated (with 12 hour interval) exits into open space]. / Otsenka riska vysotnoi dekompressionnoi bolezni pri imitatsii povtornykh (s 12-chasovym intervalom) vykhodov v otkrytyi kosmos]

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.

[Quantification of combined effect of physical-chemical factors by the parameters of human external breathing]. / Kolichestvennaia otsenka kombinirovannogo vliianiia fiziko-khimicheskikh faktorov po pokazateliam vneshnego dykhaniia cheloveka.

Quantitative evaluation of the combined effect of physical-chemical factors, i.e. hypodynamia, ionizing radiation at small doses, noise, vibration, and altered gas composition of the atmosphere was accomplished during 3- and 15-day experiments with exposure of 11 volunteers (factually 16 subjects) to specified environment in hyperbaric chamber by the parameters of external breathing. Established was an integral parameter of quantitative assessment, functional strain index, variations of which are fully consistent with the alterations in external breathing parameters. Symptoms of a summed effect can be deduced from shifts in external breathing as a result of combined action of a set of diverse factors.

[Hypobaric atmosphere and decompression safety of outer space explorations on the first days of flight]. / Gipobaricheskaia atmosfera i dekompressionnaia bezopasnost vykhodov v otkrytyi kosmos v pervye sutki polëta.

54 subjects aged 21-47 participated in 8 series of experiments (298 altitude investigations) aimed at selecting decompression-safe protocols for transition from hypobaric normoxic environment to reduced pressure. Experimental data is discussed and some protocols for safe transition to reduced pressure are recommended. The experiments allowed to display in diagram form the ratio of permissible magnitudes of residual pressure (the working pressure in the extravehicular suit) to the duration of a preliminary exposure in normoxic hypobaric conditions.

[Changes in the maximum permissible supersaturation coefficient in altitude decompression]. / Izmenenie maksimal'no dopustimogo koeffitsienta perenasyshcennia pri vysotnoi dekompressii.

This paper presents experimental data obtained during 383 altitude chambers tests in which 70 subjects participated. The purpose of the tests was to verify experimentally the safety of altitude decompression regimens that simulated transition from the orbital station atmosphere at a normal barometric pressure to the space suit oxygen atmosphere at a lowered pressure. The results help better understand correlations between the maximal allowable super-saturation coefficient and total postdecompression pressure.

[Comparative study of decompression-induced formation of gas bubbles using ultrasonic equipment and the development of altitude-decompression disorders]. / Sravnitel'noe izuchenie dekompressionnogo obrazovaniia gazovykh puzyr'kov s pomoshch'iu ul'trazvukovoi apparatury i vozniknoveniia vysotho-dekompressionnykh rasstroistv.

442 altitude experiments on 40 volunteers were performed. Gas bubbles in venous blood were detected using an ultrasonic Doppler system functioning in a continuous mode at a frequency of 5 MHz. The threshold of bubble formation was identified in 31 test subjects and that of emergency of altitude-decompression disorders, in 28 test subjects. Individual resistance to decompression-induced bubbles was revealed. It was shown that the thresholds may vary with time, in the head-down position and in the head-down position combined with exercises. A correlation was established between the rate of intravascular bubble formation and the frequency of altitude-decompression disorders.

[Sensitivity of the respiratory regulatory apparatus to CO2 under simulated space flight conditions]. / Chuvstvitel'nost' apparata reguliatsii dykhaniia k CO2 v modeliruemykh usloviiakh kosmicheskogo poleta.

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.

[Analysis of clinical symptoms of cases of human decompression disease in altitude chamber studies]. / Analiz klinicheskoi simptomatiki sluchaev vysotno-dekompressionnoi bolezni cheloveka pri barokamernykh issledovaniiakh.

Over 2400 altitude chamber ascents in which 130 volunteers participated were performed using different decompression tables. The cases of decompression disease were classified in terms of its types and severity. It is stressed that the experiments involved in decompression studies have to be extremely careful because the disease may have various and sudden manifestations.

[Relation between the probability of development of altitude-decompression disorders and the duration of pre-exposure to a hypobaric atmosphere]. / Veroiatnost' razvitiia vysotno-dekompressionnnykh rasstroistv v zavisimosti ot prodolzhitel'nosti predvaritel'nogo prebyvaniia v gipobaricheskoi atmosfere.

Healthy volunteers, aged 21-47 years, were kept in an altitude chamber. Before decompression to a residual pressure of 293.3 GPa the test subjects were consecutively exposed to 1120 GPa for 2 hrs and then to 733.3 GPa for 24, 18 or 12 hrs. At 293.3 GPa the test subjects performed a moderate workload for 6 hrs. It has been concluded that prior to the use of a space suit with the working pressure 0.3 kgf/cm2 (293.3 GPa) the time of exposure to a hypobaric normoxic (29-30% O2) atmosphere with the total barometric pressure 733.3 GPa should not be less than 18 hrs and it should preferably be 24 hrs. In this situation decompression safety of 6-hr extravehicular activity can be predicted with a high probability.

[Effect of a nitrogen admixture in the inhaled oxygen on the effectiveness of 2-hour desaturation before decompression from 760 to 220 mm Hg]. / Vliianie primesi azota vo vdykhaemom kislorode na éffektivnost' dvukhchasovoi desaturatsii pered dekompressiei ot 760 k 220 mm rt. st.

The ground-based experimental study of denitrogenation by oxygen breathing showed that two-hour denitrogenation was inadequate if the breathing gas contained about 10% nitrogen or if the process included 3-10 min of air breathing. The reduction of the nitrogen content in the breathing gas to 0.4-5% eliminated severe forms of the decompression disease and decreased significantly the incidence of its mild forms to 3.2%. This allowed work of moderate load at the ambient pressure 220 mm Hg after two-hour breathing of oxygen with nitrogen admixture of no more than 5%.

[Probability of altitude decompression sickness following a drop in pressure from 840 to 308 mm Hg]. / Veroiatnost' vysotnoi dekompressionnoi bolezni posle perepada davlenii ot 840 do 308 mm rt. st.

The decompression from the hyperbaric air atmosphere with the pressure 840+/-5 mm Hg and subsequent 40 min exposure to the hypobaric atmosphere 308+/-1 mm Hg containing 40 to 95% O2 cause a decompression disease in 5-40% cases. The probability of the disease depends on the duration of nitrogen saturation at an increased pressure, physical fitness and individual susceptibility to decompression sickness.