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The paper considers key methodical, logistics and tactical aspects of enhancing cosmonaut's medical monitoring to ensure crew safety in long-duration space mission. Activities toward extension of the diagnostic capabilities included hardware development, choice of examination procedures and defining the content of physiological information that would be necessary and sufficient for evaluation, including in real-time, of the cardiovascular system function and capacity, planning functional tests procedures as close as possible to the generally accepted clinical protocols used in selection of candidates for cosmonauts, and pre- and post-flight examination; refining the objective criteria of test tolerance and termination, and end-of-mission LBNP training tolerance and effectiveness; constructing a fundamentally new structure for medical telemetry data acquisition and processing at the Moscow Mission Control Center (MCC-M).

This was the first study of age-related differences of the cardiovascular system functioning and reactions to the LBNP test in career cosmonauts. Results of 174 LBNP tests performed within the standard medical monitoring program using Gamma-01 (orbital station Mir) and Gamma-lM (ISS) were subjected to comparative analysis. Thirty eight cosmonauts--members of 25 long-duration Mir and ISS missions were divided into two age groups, i.e. 30-39 y.o. (mean 36 & 0.7, 39% of all subjects) and 40-55 y.o. (mean 46 & 0.8, 61% of all subjects). The testing was performed before launch and in flight (typically on FD-120). Age-specifc changes in the hemodynamic status were recorded in resting cosmonauts pre-flight and in spaceflight microgravity; relative dynamics of the CV parameters in response to standing posture imitation was on one and the same patterns and yet demonstrated unequal intensity before and in flight. Test results implicate that analysis and interpretation of cosmonauts' medical monitoring data should take into account individual age, which is of particular practical importance when dealing with the LBNP test data obtained in different periods of space flight.

To put into service the diagnostic and prognostic capabilities of the lower body negative pressure test (LBNP) during extended space flights, cardiovascular reactions associated with various levels of test tolerance were analyzed and compared. The article gives account of 60 tests performed by 44 cosmonauts 33 to 53 years of age during 59- to 415-d flights. In 36 tests tolerance was good and in 24 - satisfactory. Medical evaluation was fulfilled using GaMMa-1M, an onboard multifunctional medical monitoring system. Dynamics of ECG, blood pressure, stroke and minute volumes, pulse filling, and vertebral-basilar tone exhibited some specific traits that mirrored LBNP tolerance. Established were diagnostically implicative values in the course of pressure drop. Evidence was obtained that during the test and ensuing data analysis consideration should be given as to the span of changes of each parameter, so the time of their initiation, and dynamics.

The paper deals with the results of electrocardiographic investigations of relatively resting 59 cosmonauts at the age of 30 to 52 during long-term space missions. Heart rate (HR), T-wave amplitude and an electric systole interval were analyzed. During their missions, the cosmonauts consistently combined HR rises with aggravated repolarization manifested by a relative elongation of the phase and T-depression. All alterations were statistically significant (p < 0.05); however, no pathology was detected in the myocardial bioelectrical activity. With this dynamics, values of the parameters under study did not, as a rule, leave the boundaries of the physiological norm.

Analyzed were data of investigation of a group of cosmonauts who participated in long-term Mir missions (125 to 438 days). The scope of investigations made in resting cosmonauts (279 before and 234 in flight) allowed classification of the cardiovascular system functioning in three types depending on the cardiac index. Correlation between circulation type and genetic factors, age and conditions of investigations (at rest or prior to a functional test) has been established. In flight, most often the cosmonauts pointed to intensification of the chronotropic function of the heart, increase in minute volume, rises in the end-systolic blood pressure (BPes) and systolic pressure in the pulmonary artery, hyperkinetic circulation, particularly before functional testing. However, values of the parameters under study did not leave the borderlines of the physiological and, as a rule, age norms. An in-depth analysis revealed three types of reaction to microgravity. Increase in minute volume due to the stroke volume and heart rate was concurrent with the BPes rise. Diminution of the volumes of hemocirculation and development of eukinetic circulation were not found to significantly alter BPes. There were several cosmonauts who did not display any proved shifts in the parameters.

Medical results of inflight cardiovascular measurements made in the 6th prime crew at rest and during provocative graded bicycle exercises and LBNP tests are presented. The methods of electrocardiography, tetrapolar rheography, kinetocardiography, arteriovenous pulsography and tacho-oscillography have been used to examine the cosmonauts. Together with regular cardiovascular changes typical of microgravity effect the individual peculiarities of developing the control mechanisms are noted. Thus in one of the cosmonauts a number of symptoms responsible for a decreased venous return. As a whole the functional state of the cardiovascular system on all flight stages was characterized by a sufficiently high physiological level.

The dynamics of pulse blood filling and regional vascular tone was studied in the crewmembers of 96- and 140-day flights aboard the station Salyut-6--Soyuz. Measurements were taken before, during and after flights, using a specially designed tetrapolar rheograph. Rheograms of the torso, forearms, legs, and rheoencephalograms of the right and left hemispheres in the frontal-mastoidal lead were recorded. The results showed that in zero-g the cosmonauts developed typical hemodynamic changes indicative of cephalad blood shifts. Thus, the hypothesis advanced and theoretically substantiated previously has found further support.

This paper presents the results of measuring central and regional (head, forearm, calf) hemodynamics at rest and during provocative tests by the method of tetrapolar rheography in the course of Salyut-6-Soyuz and Salyut-7-Soyuz missions. The measurements were carried out during short-term (19 man-flights of 7 days in duration) and long-term (21 man-flights of 65-237 days in duration) manned missions. At rest, stroke volume (SV) and cardiac output (CO) as well as heart rate (HR) decreased insignificantly (in short-term flights) or remained essentially unchanged (in long-term flights). In prolonged flights CO increased significantly in response to exercise tests due to an increase in HR and the lack of changes in SV. After exercise tests SV and CO decreased as compared to the preflight level. During lower body negative pressure (LBNP) tests HR and CO were slightly higher than preflight. Changes in regional hemodynamics included a distinct decrease of pulse blood filling (PBF) of the calf, a reduction of the tone of large vessels of the calf and small vessels of the forearm. Head examination (in the region of the internal carotid artery) showed a decrease of PBF of the left hemisphere (during flight months 2-8) and a distinct decline of the tone of small vessels, mainly, in the right hemisphere. During LBNP tests the tone of pre- and postcapillary vessels of the brain returned to normal while PBF of the right and left hemisphere vessels declined. It has been shown that regional circulation variations depend on the area examined and are induced by a rearrangement of total hemodynamics of the human body in microgravity. This paper reviews the data concerning changes in central and regional circulation of men in space flights of different duration.

This paper discusses regional hemodynamics and vascular regulation during and after space flights of over 3 months in duration. Mechanisms of cardiovascular adaptation to weightlessness are described. The postflight differences in the recovery of regional hemodynamics seem to depend on the individual characteristics, age-related changes of the cardiovascular system, as well as the countermeasures and rehabilitation measures performed during and after flight.

Experiments were carried out to explore the possible use of tetrapolar rheography in the assessment of pulse blood supply to a certain area and quantitative characteristics of cardiac output and blood flow in the limbs. Sixty five subjects were examined: fifty subjects had congenital diseases of the heart and the major vessels and 15 subjects were healthy. The volume-pulse blood supply was measured by means of a tetrapolar rheograph. Calculations were based on the Kedrov formula. Control measurements of cardiac output were made by the dye-dilution method (Evans blue). The correlation coefficient was 0.96. This gives evidence that the above instrument can be used to determine cardiac output. Studies of the pulse blood supply to the limbs show that the measurements may reflect not only marked pathology but also changes due to functional vascular shifts.

The two members of the 140-day permanent Salyut-6 space flight were exposed to 5 LBNP tests at -25 and -35 mm Hg for 2 and 3 min, respectively. Circulation responses to the LBNP tests were measured with respect to the heart rate, arterial pressure, chronocardiogram and cardiac output. As compared to the preflight data, inflight responses were characterized by a greater tachycardia, preload insufficiency, and vascular tone in the absence of orthostatic intolerance. Possible mechanisms of the changes in the circulation responses are discussed.

This paper presents the results of studying central and regional hemodynamics in short-term (7 days) and long-term (65-237 days) space mission onboard Salyut-6--Soyuz and Salyut-7--Soyuz using the method of tetrapolar rheography. During space flights circulation changes were observed: variations in pulse blood filling and tone of regional vessels (head, forearm, leg) and insignificant changes of stroke volume and cardiac output. In response to exercise tests the contribution of stroke volume to cardiac output decreased and that of the chronotropic function of the heart increased. These changes were induced by variations in the hemodynamic status of the human body and were, to a certain extent, dependent on flight duration and position of the vascular area relative to the heart. The changes suggested that the circulation system retained its adaptive capabilities in flights of 237 days in duration.

Postflight rheographic examinations carried out at rest and during postural tests showed noticeable changes in the vascular regulation and significant blood redistribution. On the recovery day there were no signs of the intracranical venous congestion to weightlessness. The tone of cerebral vessels, however, increased to prevent the development of cerebral venous congestions during the antiorthostatic test. This may be a result of weightlessness adaptation. These cerebral hemodynamic reactions were more pronounced in the crewmembers who made an 8-day flight than in those who made a two-day flight, i. e. in the cosmonauts who returned to Earth after weightlessness adaptation.

During the 140-day flight of the orbital station Salyut-6 two primary crewmembers performed 5 exercise tests on a bicycle ergometer at a load of 750 kgm/min for 5 min. During tests heart rate, and before and after tests arterial pressure, left ventricular chronograms and cardiac output (rheographically) were recorded. In comparison to the preflight tests, the flight tests were characterized by less expressed changes in phasic parameters, moderate increase in cardiac output and, occasionally, insufficient decrease in peripheral resistance. These changes can be attributed to the weightlessness-associated deficiency of the circulating blood volume.