Negative pressure breathing (NPB) is respiration during which different devices are used to generate a mean pressure level in airways over breathing cycle less than pressure the thorax is exposed to. One of the options is NPB on the phase of inspiration (NPBin). In 1990s, NPB and NPBin were proposed as a method to prevent the undesirable body liquids shifting towards to cranium in piloted space flights. In clinical practice, NPBin is used for resuscitation and central hemodynamics management after severe hemorrhage. The paper discusses the significance of body positioning for the NPBin physiological effects and compares with the results of NPBin application during dry immersion (DI). The investigation was focused on NPBin-induced changes of central hemodynamics and redistribution of the body liquids in different parts of the body. It was found that NPBin raises amplitudes of the physiological parameters oscillations synchronous with breathing, and that DI and body positioning influence the reactions to NPBin by altering these amplitudes primarily. These observations permit extrapolations of the results of NPBin tests with supine subjects on a broad variety of experimental conditions.

The research is a complex experiment that had a double-blind randomized placebo-controlled study. An effective measurement of the parameters of the human body was examined on eight apparently healthy subjects during an exposure of 8 h in altered magnetic conditions. The results of the experiment did not reveal significant risks for the functional state of the human body with a decrease in the multiplicity of about 1000 times.

This article summarizes the experience of managing patients with COVID-19-associated pneumonia treated in one of the intensive care units of a multidisciplinary hospital with and without a heated oxygen–helium mixture. It has been shown that the use of a heated oxygen–helium mixture in the complex therapy of pneumonia caused by SARS-CoV-2 is effective. A comparative analysis of the clinical manifestations of the disease and the results of laboratory tests in the main and control groups of patients confirm with a high degree of reliability the improvement of blood oxygenation, the normalization of the acid–base balance and the positive dynamics of the main parameters, which ultimately increases the efficacy and reduces the time of treatment.

The aim of our study was to investigate the effects of inspiratory negative pressure breathing (NPBin) via impedance threshold device on breathing pattern and body fluid distribution in cosmonauts during spaceflight. The lung function (volumes and flows, breath-hold time) was estimated in details before NPBin exposure as well. The 16 cosmonauts participated in study on ISS board: they were examined before, during spaceflight and after landing. All cosmonauts included in the study were well trained for providing the experimental procedure by themselves. The mask with impedance threshold (-20 cm H2O on inhale) was used. Breathing rate, intramask pressure and electrical impedance of head, body and limbs have been monitoring before (5 min) and during NPBin (20 min). The obtained data has shown no significant differences in lung volumes and flows in comparison of preflight and spaceflight values. Generally, NPBin led to significant decrease of breathing rate. No statistically significant changes in electrical impedance of body and head at NPBin compared with tidal breathing were found. The effectiveness of NPBin as a preventing means for fluid shifts in cosmonauts (astronauts) during spaceflight is discussed and needs the further studies.

In this study we demonstrate what kind of relative alterations can be expected in average perfusion and blood flow oscillations during postural changes being measured in the skin of limbs and on the brow of the forehead by wearable laser Doppler flowmetry (LDF) sensors. The aims of the study were to evaluate the dynamics of cutaneous blood perfusion and the regulatory mechanisms of blood microcirculation in the areas of interest, and evaluate the possible significance of those effects for the diagnostics based on blood perfusion monitoring. The study involved 10 conditionally healthy volunteers (44 ± 12 years). Wearable laser Doppler flowmetry monitors were fixed at six points on the body: two devices were fixed on the forehead, on the brow; two were on the distal thirds of the right and left forearms; and two were on the distal thirds of the right and left lower legs. The protocol was used to record three body positions on the tilt table for orthostatic test for each volunteer in the following sequence: (a) supine body position; (b) upright body position (+75°); (c) tilted with the feet elevated above the head and the inclination of body axis of 15° (−15°, Trendelenburg position). Skin blood perfusion was recorded for 10 min in each body position, followed by the amplitude–frequency analysis of the registered signals using wavelet decomposition. The measurements were supplemented with the blood pressure and heart rate for every body position analysed. The results identified a statistically significant transformation in microcirculation parameters of the average level of skin blood perfusion and oscillations of amplitudes of neurogenic, myogenic and cardiac sensors caused by the postural changes. In paper, we present the analysis of microcirculation in the skin of the forehead, which for the first time was carried out in various positions of the body. The area is supplied by the internal carotid artery system and can be of particular interest for evaluation of the sufficiency of blood supply for the brain.

Self-contained self-rescue (SCSR) breathing devices are the only option for providing breathable air if hazardous components cannot be removed from external air after underground accidents. In this study, we developed a mathematical model of human breathing with an SCSR apparatus. The model describes the gas-content dynamics in the three system compartments: the lungs, body tissues and a SCSR apparatus. The results of simulations agreed well with experimental data obtained from a volunteer breathing through the apparatus.

A comparative study of differentiation of CD3+CD4+ peripheral blood lymphocytes of healthy volunteers (n=30) and patients with irritable bowel syndrome (IBS, n=22) was conducted using multicolored flow cytometry. In patients with IBS, The level of T-helpers of Central memory (CM), CD45RA-CD62L+ in patients with IBS significantly exceeded the values of the control group. Among the General population of CCR6+ CM Th17 there were significant increases in the percentage of DN Th17 (from 2.58% (1.55; 3.15) to 3.14% (2.53; 4.09) at p=0.011) and Th17.1 (from 9.42% (7,594 10.52) to 10.08% (10.33; 14,48) at p=0,002) when compared with the control. Moreover, IBS showed a change in the subpopulation composition of follicular T-helper cells (Tfh). Thus, in patients with IBS the relative content of Tfh2 cells and not yet described in detail Tfh with phenotype CXCR3+CCR6-CCR4+ decreased, while the level of two populations of Tfh with properties of Th17 (DN Tfh17 and Tfh17.1) significantly increased. The detected changes in the composition of Tfh suggest the presence of changes in the functioning of a specific humoral immune response in this disease. Consideration of the participation of these cells in the pathogenesis of IBS stimulation and differentiation in lymphocytes - the subject of further research. The revealed features of the subpopulation composition of T - lymphocytes complement the existing understanding of the mechanisms of occurrence of this disease and should be taken into account in the diagnosis, therapy and prevention of complications of this disease.

Introduction: Apart from inflammation and endothelial dysfunction, other key components in the development of atherogenesis include prothrombogenesis and oxidative stress. The effects of long-term confinement and isolation, exposure to radiation and different gravity forces during space travel could potentially increase the long-term risk of atherosclerosis. To the best of our knowledge, this is the first study determining the status of prothrombogenesis and oxidative stress in six cosmonauts subjected to the longest duration of confined isolation period of 520 days in preparation for prospective undetermined manned space travel to Mars. Materials and Methods: This collaborative research between the National Space Agency (ANGKASA), Universiti Teknologi MARA, Malaysia and Institute of Biomedical Problems (IBMP), Russia was conducted at the Russian Academy of Sciences IBMP, Moscow, Russia. Six multi-national cosmonauts were assigned to live in a ground-based confined module for 520 days. Standard exercise and diet regime were instituted throughout the isolation phase. Six age, ethnic and gender-matched healthy, free-living ground controls were recruited in parallel. Serial serum and whole blood were analysed for biomarkers of prothrombogenesis [plasminogen activator inhibitor-1 (PAI-1) and homocysteine] and oxidative stress [oxidised low-density lipoprotein (ox-LDL) and malondialdehyde (MDA)]. Results: There were significantly lower concentrations of PAI-1 and homocysteine in cosmonauts during confinement compared to the controls. There were no significant differences seen in the concentrations of biomarkers of oxidative stress during confinement but there was a significant percentage change increment for serum MDA in cosmonauts. Conclusion: Long-term confinement decreased the risk of prothrombogenesis and this could be attributed to the exercise and diet regime which includes omega-3 fatty acids supplementation given to the crew members during their confinement period. However, oxidative damage could not be excluded and may be attributed to the influence of psychological stress during this prolonged confinement.

Purpose: Sleep deprivation is present not only in sleep disorders but also in numerous high demanding jobs and negatively affects cognition, performance and health. We developed a study design to distinguish the effects and need for recovery of two short-term disturbances - intermittent sleep fragmentation and partial sleep restriction. Methods: The randomized within-subjects design contained two weeks each with a baseline night, an intervention night of either sleep deprivation (5 h) or sleep fragmentation (light on every hour) and two undisturbed recovery nights. Twenty healthy male participants (mean age: 39.9 +/- 7.4 years, mean BMI: 25.5 +/- 2.2 kg/m(2)) underwent polysomnography, a psychomotor vigilance task (PVT), and subjective questions on well-being and sleep efficiency. Results: Percentage-wise, the restriction night had significant less wake times, less light sleep (stage 1), less REM sleep, but more deep sleep (stage 3) than the fragmentation night. The restriction week displayed a significant recovery effect regarding these sleep stages. The sleep fragmentation week presented a significant recovery effect regarding sleep onset times. PVT performance showed only a slight recovery effect after sleep restriction. Subjective sleep quality was reduced after both interventions with a significant recovery effect during restriction week only. Conclusions: Short-term sleep restriction presented as a stronger sleep disturbance than short-term intermittent sleep fragmentation, including a stronger need for recovery. Already a one night sleep deprivation had an effect beyond two recovery days. The PVT was not sensitive enough to reveal significant changes. Next, autonomic parameters as possible biomarkers will be investigated.

Many mentally and physically high demanding jobs (e.g., shift-workers, astronauts) cause sleep fragmentation and deprivation. Impaired sleep can lead to an impaired autonomic nervous system, associated with stress, and increased morbidity and mortality. We investigate the effects of short-term sleep fragmentation and sleep restriction on the autonomic tone. We hypothesized (1) that autonomic parameters mirror effects of sleep restriction and fragmentation and (2) that sleep fragmentation has stronger negative effects on the autonomic tone than sleep restriction. A randomized cross-over design with 20 healthy male participants (mean age: 39.9 ± 7.4 years, mean BMI: 25.5±2.2 kg/m²) was used. Each participant underwent 2 x 4 nights, experiencing both interventions separated by a wash-out phase of one week. The protocol included one baseline night, one intervention night of either sleep deprivation (5 hours) or sleep fragmentation (light on every hour) and two recovery nights of undisturbed sleep. Full laboratory-based polysomnography was conducted. Additionally, electrocardiography and continuous blood pressure were recorded under paced breathing at 12/min before falling asleep (evenings) and after waking up (mornings). Parameters of the autonomic tone - parameter of the heart rate variability (standard deviation of normal to normal R-R intervals - SDNN). SDNN increased each night and was higher in the mornings compared to the evenings before. During sleep restriction, the change in SDNN (morning - evening) significantly increased from baseline to intervention (2.2±17.8ms to 22.0±26.7ms; p<0.05). During sleep fragmentation, the change in SDNN did not differ significantly and showed a small decrease from baseline to intervention (16.2±33.1ms to 10.8±24.3ms; n.s.). Comparing both interventions, the overall SDNN difference became significant (intervention night - baseline night: restriction 19.8ms vs. fragmentation -5.8ms; p<0.05). Sleep restriction had a stronger but more positive effect on the autonomic nervous system than sleep fragmentation. However all effects remained to be small due to limited sample size and just one night intervention The project was funded by the German Aerospace Center e.V (Deutsches Zentrum für Luft- und Raumfahrt e.V. - DLR, #50 WB 1532)

The aim of the study was to assessment the effects of normobaric oxygenation (NBO) with 100 % oxygen for 60 minutes on the state of central and peripheral hemodynamics of a humans. Material and methods. The method of laser Doppler flowmetry and capillaroscopy was used in 10 healthy men (27.3±4) initially, at 5-15, 45-55 minutes of the NBU and during the recovery period. Results. Individual differences between the testers, depending on the state of the autonomic nervous system, assessed using the Kerdo index (IR), are revealed. The testers with IR 0 showed a two-phase reaction. Conclusions. The physiological response to hourly breathing with pure oxygen can be different and depends on the state of the tone of the autonomic nervous system.

OBJECTIVE:Cranial electrotherapy stimulation (CES) is considered to be a potential treatment for insomnia. Women are more likely to suffer from insomnia than men. Therefore we studied the effect of CES on sleep efficiency in young healthy women. METHODS:A randomized, controlled clinical study was conducted on 40 women (age 18-35 years) without sleep disorders. Each subject underwent two nights of polysomnography in a sleep center. During the second night, we applied CES with a commercial device (Alpha-Stim 100) using either active or sham stimulation (double-blinded). Sleep was evaluated with respect to differences between the active and sham modes. Sleep electroencephalogram (EEG) analysis was applied to determine frequency changes. RESULTS:In our study we found no evidence of any direct influence of the Alpha-Stim 100 on sleep. After application of CES, we determined no significant differences between the active group and the control group (sham). Using EEG spectral analysis there was evidence of a frequency-lowering influence on the low-α frequency band (8-10 Hz). CONCLUSIONS:At most we may assume a reproducible effect on the α frequency measured in the EEG for application of CES with current levels  >100 µA and presumably also with frequencies  >0.5 Hz, with application directly at the cranium. We found no influence on sleep parameters. The effect on the low-α band evidenced in quantitative EEG analysis would require further investigation in a study with sufficient effect size. SIGNIFICANCE:This is the first study to investigate the effects of CES with polysomnography during and after therapy. Our study contributes to the few controlled trials that have been conducted to study CES and its effects on the EEG α band. Highlights • This is the first study to investigate the effects of the Alpha-Stim in polysomnography during and subsequent to therapy. • In a quantitative electroencephalogram analysis we studied the data obtained for systematic changes. • To minimize placebo effects in patients with sleep disorders, we conducted the tests on subjects without such disorders.

Peripheral hemodynamics was studied in the upper extremities of human subjects during a 5-day exposure in microgravity modeled by “dry” immersion (DI). The object of investigation was skin adjacent to the nail bed of the fourth finger and forearm skin. Microcirculation was measured using laser Doppler flowmetry (LDF) and computer capillaroscopy (CCS). In addition, peripheral hemodynamics was assessed in subjects donned in a Penguin axial-loading suit (PLS). The subjects were divided into two groups: with (G-2) and without (G-1) PLS. The results are the following: PLS leveled down all changes in the microcirculatory bloodstream (MCB) of the upper extremities. By the end of DI, some subjects in G-1 were found to have a more intensive tissue perfusion and increased number of capillaries, and exaggerated activity of passive mechanism of blood flow modulation Ас (one-way ANOVA, p < 0.05).

The paper presents basic concepts of toxicological problems under human containment in a closed hermetic hyperbaric volume basing on the literature data and our own long-term scientific and practical experience aimed at diving and diving medicine, development and testing of the decompression chambers. The paper describes the following essentials of the problem: gaseous atmospheric composition in closed hermetic volumes, evolution of exogenous gases in human organism under lowering in the chamber, evolving hazardous gaseous substances (HGS) in the closed volume, design average daily rate of HGS evolving, effect of conditions on HGS evolving, their maximum permissible concentrations, methods of СО2 and HGS removal in the chambers, and regulatory requirements. It is shown that the most of the modern existing chambers do not meet the regulatory requirements that may result in negative effects on human health. The ways to except the cases of human intoxication in the decompression chambers and systems are offered in the paper.

A mathematical model of biotechnical system integrating the human cardiorespiratory system with hard- and software was designed to investigate breathing control. The model describes dynamics of carbon dioxide and oxygen in 3 biotechnical system compartments in the course of rebreathing tests. The tests do not require tanks with compressed gas and, therefore, can be performed in space flights. Results of simulated modeling of the ventilation response in 2 breath tests, i.e. to hypercapnia due to rebreathing of a hyperoxic gas mixture and to hypercapnia combined with hypoxia due to air rebreathing, are presented. Model validity was verified by comparison of the modeling and experimental data. The mathematical model made it evident that CO2 partial pressures in tissues, lungs and the breathing circuit equalize very fast when initial carbon dioxide concentration in the respiration circuit is equal to the end-tidal CO2 concentrations in man at rest.

Changes in external respiration and central hemodynamics induced by negative (relative to atmospheric) inspiration pressure were studied in supine subjects before and on the fourth day of a dry immersion (DI) experiment. Changes in the cardiorespiratory system as a result of negative inspiration pressure included an increase in the amplitude of breathing motions and reduction of their frequency, and distinct breathing-related HR fluctuations. Combinations of immersion and altered pressure in the mask caused breathing-related variations of systolic pressure and plethysmogram signal, and improved arterial blood oxygenation. These results could be useful for developing pressure-gradient methods of counteracting adverse effects of blood redistribution toward the cranial end.