A.R. Kotovskaya, M.I. Koloteva, V.Yu. Lukjanuk, A.M. Nosovsky

The major goal of this study was to determine a possibility of forecasting of individual changes of cardiac activity of cosmonauts (according to electrocardiogram) during normal descent from orbit after space missions (SM) of various duration on the basis of preflight ECG analysis. The analysis of individual changes of cardiac activity according to electrocardiogram at 29 cosmonauts in 33 short-term missions (from 8 to 30 days), performed at 1982 - 2006 and at 25 cosmonauts in 30 long missions (from 73 to 197 days), performed at 1995 - 2007 was carried out at dynamic su-pervision at cosmonauts from medical selection till their return to the Earth. In ground-based researches an electro-cardiogram was registered: at rest and at cycle ergometry - in 12 standard leads, at centrifuge test - in 3 Neb leads and chest leads V1 and V5. In space flights during launch to an orbit and descent to the Earth an electrocardiogram in DS (equivalent of 1 standard) lead was registered. The maximal accelerations during descent, on average, did not ex-ceed 4.26±0.3 g in short-term missions and 4.0 ± 0.1 g in long missions. The technique of numerical score of ECG changes, which allow to reveal quantitative changes on ECG at dynamic supervision from medical selection of cosmo-nauts to the end of the missions was developed for the first time. Statistical processing of changes of cardiac activity (on ECG) of cosmonauts was performed with the use of multifactor dispersive analysis. In 60.6 % of cases (short-term SM, n = 20) and in 70 % of cases (long SM, n = 21) there were no considerable changes on ECG at cosmonauts before SM and no negative trends of ECG parameters during launch and descent from orbit. In 27.3 % of cases (n = 9, short-term SM) and in 20 % of cases (n = 6, long SM), when different combinations of symptoms of ECG deviations were found before SM, they became more expressed during reentry. In 12.1 % of cases (n = 4, short-term SM) and in 10 % of cases (n = 3, long SM): before SM - EKG was within norm, but during reentry in SM expressed cardiac abnormalities on EKG have appeared. For the first time on the basis of preflight ECG data (according to numerical score of ECG changes) the opportunity of forecasting of ECG changes of cosmonauts during descent from orbit in 87.9 % of cases (n = 29 from 33) in short-term SM and in 90 % of cases (n = 27 from 30) in long SM has been established. The prospect of these researches is the preliminary, before SM, forecast of possible unfavorable changes on ECG during the final stage of the mission - reentry. This can give us an opportunity to in advance use of special preventive, cure or other necessary countermeasures. The present work is the beginning of the important direction of researches for definition of admissible medical risks for development and perfection of the requirements to medical selection of space crews regarding an admission to SM of persons with partial insufficiency of health.