[EXPERIMENTAL AND THEORETICAL STUDIES OF HUMAN HYPERCAPNIC VENTILATORY RESPONSE WITH THE USE OF MATHEMATICAL GAS EXCHANGE MODELING].

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.

[Dynamics of duration of tracheal forced expiratory noises during long-term isolation in the "Mars-500" experiment].

Dynamics of duration of tracheal forced expiratory noises in a group of volunteers was studied before, during and after 520-days confinement. The duration did not change in most volunteers. Two volunteers demonstrated significant changes of tracheal sounds duration and some spirometric parameters. Increase in duration of tracheal forced expiratory noises and decrease in spirometric parameters reveal ventilatory impairment of obstructive type. Analysis of duration of tracheal forced expiratory noises dynamics during prolonged confinement proves to be a sensitive technique to test ventilatory function changes.

[Estimation of the forced expiration tracheal sounds intensity].

The investigation of tracheal sounds of forced expiration is realized on the basis of the mathematical model of forced expiration. It is demonstrated that a separation flow in the region of a dynamical contraction trachea during forced expiration may to cause tracheal sounds generation.

[Influence of changed gas media on acoustic parameters of human forced exhalation].

In previous study it was shown that duration of tracheal forced expiratory noises is promising to reveal negative changes of lung function after dive. The objective is a study of parameters of tracheal forced expiratory noises in changed gas media. The first experiment involved 25 volunteers (22-60 years), performed forced exhalation under normal pressure with air, oxygen-helium and oxygen-krypton mixtures. The second experiment in the chamber involved 6 volunteers (25-46 years), which performed forced exhalation with air under normal pressure (0.1 MPa), and under elevated pressure 0.263 MPa with air and oxygen-helium mixture. In the first experiment the direct linear dependence on gas density was found for forced expiratory noises common duration in the band of 200-2000 Hz and for its durations in narrow 200-Hz bands, excluding high frequency range 1400-2000 Hz. In the second experiment a significant reversed dependence of high frequency durations and spectral energies in 200-Hz bands (1600-2000 Hz) on adiabatic gas compressibility. Individual dynamics of common duration of tracheal forced expiratory noises under model dive of 16.3 m (0.263 MPa) is more then the diagnostic threshold of this parameter for lung function decrease, previously obtained for divers under normal pressure.

[Characteristics of negative pressure inspiration effect on the cardiorespiratory system of humans in the conditions of 5-day dry immersion].

Changes in external respiration and central hemodynamics induced by negative (relative to atmospheric) inspiration pressure were studied in supine subjects before and on day-4 of a dry immersion (DI) experiment. Changes in the cardiorespiratory system as a result of negative inspiration pressure included rise of the amplitude of breathing motions and reduction of their frequency, and distinct breathing-related HR fluctuations. Combination 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 can be useful for developing pressure-gradient methods of counteracting the adverse effects of blood redistribution toward the cranial-end.

[Biomechanics and regulation of the external respiration in the conditions of 5-day dry immersion].

The work was concerned with evaluation of the external respiration function and regulation in healthy human subjects participating in simulation of the microgravity effects by dry immersion (DI). In the baseline data collection period, in DI (days 2 and 4) and after DI completion pulmonary volumes were registered, the ratio of thoracic and abdominal components of quiet breathing and respiratory maneuvers calculated, and parameters of respiration regulation, i.e. length of breath-holding and ability to voluntary control breathing motions, were determined. It was shown that breathing pattern did not undergo gross changes in immersion as compared with pre-DI test data; however, inspiratory reserve volume grew (p < 0.05) and expiratory RV reduced (p < 0.01). DI did not alter the ventilation function of lungs; yet, most of the subjects trended to increase the abdominal component of quiet breathing and displayed a statistically significant increase of the parameter during the maneuver made to determine the vital capacity of lungs. Maximum breath-holding, equally in the course of inspiration and expiration in DI, did not differ from baseline values. Accuracy of voluntary breathing control was better in immersion. We believe that similar to microgravity, exposure in DI produces regular alterations of pulmonary RV (partly because of changed body position), thoracic-abdominal ratio in breathing motions, and shifts in voluntary respiration regulation.

[Acoustic and spirometric indices of forced expiration noise in the conditions of 5-day dry immersion].

Dynamic studies of forced expiration (FE) indices involved 7 normal males aged 21 to 25 participating in a 5-d experiment with dry immersion (DI). FE spirometry was conducted simultaneously with registration of tracheal noise with the help of a microphone. Indices included acoustic duration of tracheal noise (Ta), forced lung capacity (FLC), FE volume per a second (FEV1), peak expiratory rate (PER) and time to reach (T(PER)) before DI, on DI days 1 and 4, and next day after completion. PER showed a significant decrease by 8.4% on DI day-1 and rose by 8.9% on DI day-4, though remaining below pre-DI values. Throughout the experiment, FLC and FEV1 did not change on the average. There was a noticeable increase of Ta by 17 % after DI which may suggest strengthening of respiratory resistance and invites further investigation. A moderate negative correlation was stated between TA and the Gensler index (r = -0.63), whereas correlation with the other spirometric indices was weak or absent.

[Oxygen consumption by resting humans at different Elbrus altitudes].

The purpose of the work was to test experimentally the "hypoxic paradox" of growing or constant oxygen consumption by normal humans exposed to O2-deficient environments. The objective was to perform thorough statistical analysis of O2 consumption at two altitudes above sea level under the conditions of close to basic metabolism, and to develop an analytical expression for adequate description of O2 consumption dependence on altitude above seal level. The investigation was fulfilled in August, 2009 at the altitudes of 2224 and 4200 m on Elbrus flanks with participation of 4 volunteers. It was shown that O2 consumption by resting humans decreases with altitude, i.e. the "hypoxic paradox" is invalid. An analytical expression was proposed to describe change in O2 consumption in the interval of altitudes from 0 to 4200 m above sea level.

[Investigation of the physiological effect of heated heliox on the human external respiration parameters].

The investigation was aimed at studying and comparison of the physiological effects of heated heliox and air on the human breathing function. Tests involved eight human subjects aged 24 +/- 4 who breathed gas mixtures and air heated to 58 +/- 5 degrees C for 21 minutes. Effects were evaluated by spontaneous pneometry and forced expiration using equipment Master Screen VIASYS. Heated heliox and air equally caused phase-by-phase growth of external breathing parameters. Conduction of the trachea and main bronchial tubes appear to increase considerably due to heated heliox rather than air.

[Survival of laboratory animals in argon-containing hypoxic gaseous environments]. / Vyzhivaemost' laboratornykh zhivotnykh v argon-soderzhashchikh gipoksicheskikh gazovykh sredakh.

Present paper is aimed at assessing the effect of hypoxic gaseous mixtures intended for the use as the fire suppression agents within closed volumes on the basis of argon with addition of carbonic acid on the body of mammalia. Three experiments were performed on the male white laboratory Wistar rats. It is indicated that argon adding to the hypoxic mixtures containing 4-5% volume increases animal survivability as compared to analogous nitrogen-based mixtures. An addition of 4-8% volume of carbonic acid impairs the of animal condition and reduces the survival rate. There noted a pronounced negative effect of the increased temperature on the survival time in the hypoxic media. One can draw inference about the principal possibility of using argon for formation of the hypoxic gaseous mixtures possessing fire suppression properties.

[The incidence of detecting hepatitis C viral antibodies in different age groups of the population in northeastern Ukraine]. / Chastota obnaruzheniia antitel k virusu gepatita C v razlichnykh vozrastnykh gruppakh naseleniia severo-vostochnoi Ukrainy.

Examinations for the presence of antibodies to hepatitis C virus (anti-C100-3) were carried out in 1143 human subjects, residents of the town of Sumy, Ukraine (681 blood donors, 176 school children, 286 subjects hospitalized for abortions and for treatment of acute traumas). Anti-HCV were determined by enzyme immunoassay using a commercial test system "Abbott" of the first generation, with confirmation of the positive findings by neutralization test. Anti-HCV were found in 2.3% free-giving blood donors and in 1.2% career donors, and in 0.8% of schoolchildren aged from 6 to 14 years. In older age groups anti-HCV findings were more frequent (in subjects of 40-49 years 4.0%, 50-59 years 5.26%, 60 years and over 6.25%).

[Analysis of the accuracy of respiratory impedance: measurements on tubes and humans]. / Analiz tochnosti opredeleniia dykhatel'nogo impedansa: izmereniia na trubkakh u cheloveka.

The accuracy of respiratory impedance measurements by a previously described device is estimated. A theory for calculation of tube impedance is considered. The standard deviations of real, imaginary parts and module of tubal impedance are about 0.1 hPa/(l/s). The mean experimental values are in the range of theoretical curves for this kind of tube. Thus, the measurements are in a good agreement with theoretical calculations. When the impedance of the human respiratory system is measured, the mean individual standard deviations of real and imaginary parts of impedance are about 0.5 hPa/(l/s), which is equal to 20% of the real impedance. Causes of measurement deviations and ways of their decrease are also analyzed.

[A device for studying respiratory mechanics by the forced oscillation technique]. / Pribor dlia issledovaniia mekhaniki dykhaniia metodom vynuzhdennykh kolebanii.

A new compact device for measuring respiratory impedance is designed. Input respiratory impedance, an impedance of upper airways and respiratory impedance corrected for upper airways shunt can be measured in 2 minutes. The space-condition requirements are complied by integrating an oscillation generator, sensors, a mouthpiece with a screen and a reference resistor in the measuring head. The oscillation generator produces small-amplitude forced oscillations (with a tidal volume of about 1 ml) at frequencies f = 7, 10, 13, 16, and 19 Hz. Algorithms of calibration and measurement provide impedance calculation. For 55 different external impedances, complex transmission factors are measured for each of the five frequencies. The standard deviation of amount and phase of complex transmission factors are less than 5% and 0.06, respectively.