Short term spaceflights influence autonomic cardiovascular control

Paper number

IAC-06-A1.7.-A2.7.04

Author

Dr. Frank Beckers, Laboratory of Experimental Cardiology, Belgium

Coauthor

Mr. Bart Verheyden, K.U. Leuven, Belgium

Coauthor

Mr. Kurt Couckuyt, K.U. Leuven, Belgium

Coauthor

Mr. Jiexin Liu, K.U. Leuven, Belgium

Coauthor

Prof. André Aubert, Belgium

Year

2006

Abstract

Introduction: Space flight causes changes in the cardiovascular system. These changes contribute to the occurrence of orthostatic intolerance after space flight. Heart rate variability (HRV) and blood pressure variability (BPV) provide a non-invasive means to study the autonomic modulation of the cardiovascular system. Spectral analysis of heart rate tachograms and blood pressure systograms enables us to distinguish sympathetic and vagal cardiovascular modulation. Low frequency (LF: 0.04-0.15 Hz) oscillations in heart rate and blood pressure provide information about sympathetic modulation and the baroreflex mechanism, high frequency (HF: 0.15-0.4 Hz) modulation of heart rate is an index of vagal modulation. 
Methods: ECG and continuous blood pressure was measured for at least 10 minutes in supine and standing position 30 days before launch; and at 1, 4, 9 and 25 days after return to Earth. In space, the same measurements were performed at day 5 and at day 8. These measurements were performed in 5 cosmonauts during short term space missions (10 days). HRV and BPV indices were calculated in time and frequency domain. 
Results: During spaceflight heart rate was significantly lower compared to the pre- and post-flight measurements in standing position (p<0.05). This was accompanied by a tendency to increase the proportion of HF power during spaceflight. Blood pressure and BPV indices remained the same as preflight. After flight measurements in supine position did not show as high differences as the measurements in standing position. After spaceflight especially HF was extremely depressed compared to the preflight conditions (standing: p<0.05). This was accompanied by a higher heart rate (p<0.05 up to R+25). The recovery of the HF power was not completed at day 25. BPV showed a tendency to increasing values up to 25 days after landing.  The baroreflex mechanism was also depressed the first day after return to Earth (p<0.06 compared to preflight values; p<0.05 compared to inflight values) but showed a significant increase up to R+25.
Conclusion: During spaceflight autonomic modulation is characterised by a vagal predominance, while after return to Earth especially the vagal autonomic modulation is extremely depressed. This also affects the baroreflex feedback. The recovery of the autonomic nervous system takes several weeks and is not fully completed 25 days after return to Earth. The recovery period is characterised by a strong sympathetic dominance. 

Abstract document

IAC-06-A1.7.-A2.7.04.pdf

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