THE SPECTRAL ANALYSIS OF HEART RATE VARIABILITY IN FORECASTING OF POST-FLIGHT ORTHOSTATIC INTOLERANCE AFTER LONG-TIME SPACE FLIGHTS

摘要

The problems of orthostatic stability estimation and forecasting of cosmonauts after a long stay in weightlessness continue to keep the urgency. Results of scientific experiments Pulse and Pneumocard which are carried out on ISS since 2003 have allowed to receive the new data in this direction The heart rate variability (HRV) analysis was carried out at 25 Russian cosmonauts who had made 5-6 monthly flights on ISS. The preflight data were compared to the results of post-flight orthostatic tests. On post-flight values of a heart rate in standing position during active ten-minute stand test all cosmonauts have been divided into three groups: with high, average and low orthostatic tolerances. Comparison of preflight values of HRV parameters with different orthostatic stability has shown, that in conditions of rest before the flight value of the relative power respiratory waves in percentage significantly higher, while the ratio absolute values of the capacity of LF/HF was significantly lower in the group cosmonauts with low and middle level of orthostatic stability to orthostatic stress (1.19 and 1.28) compared with the cosmonauts with good orthostatic stability (2.64). The decrease of LF/HF, which characterizes the autonomic balance, points to the relative weakening of the sympathetic level of regulation. Potentially it could be the reason for insufficiency of the mobilization mechanisms of functional reserve, which is manifested in the post-flight period. As a method of forecasting the potential reductions in orthostatic tolerance of the load after a long-term space flight we suggest to use the spectral analysis of HRV at rest in the supine position. In this case the low values of LF/HF should be considered as an unfavorable prognostic sign.