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Publication AbstractsParasympathetic Activity during Parabolic Flight, Effect of LBNP during MicrogravityA. Capderou, M.D., Ph.D., O. Bailliart, M.D., Ph.D., P. Maison-Blanche, M.D., A. W. Kedra, M.D., Ph.D, O. Atkov, M.D., Ph.D., P. Techoueyres, M.S., J-L. Lachaud, M.S., and P. Vaïda, M.D.Aviat Space Environ Med 2001; 72:361-7 AbstractBackground/Hypothesis: During parabolic flight, in the standing position, changes are partly due to an acute shift in fluid between the lower extremities, the head and the thorax (Vaïda P, et al. J Appl Physiol 1997; 82:1091-7; and Bailliart O, et al. J Appl Physiol 1998; 85:2100-5). We hypothesized that modifications of parasympathetic activity associated with changes in hydrostatic pressure gradients induced by changes in gravity could be detected by analysis of short time periods. Methods: We assessed heart rate variability (HRV) in 11 healthy volunteers by indices of temporal analysis (NN, SDNN, RMSSD) and normalized indices such as coefficients of variation CV-SDNN and CV-RMSSD and ratio SDNN/RMSSD. A lower body negative pressure (LBNP) at -50 mm Hg was randomly applied during the microgravity phase (0 Gz) to counteract the lack of hydrostatic pressure in the lower part of the body. Results: NN, CV-SDNN and CV-RMSSD decreased during hypergravity phases and increased during microgravity and during early normogravity (1 Gz) period at the end of parabolas. With LBNP changes are less pronounced at 0 Gz and in the 1 Gz post parabolic period. Conclusion: We concluded that parasympathetic nervous activity is recordable by temporal analysis of HRV during short periods of time. LBNP applied during 0 Gz phase reduced the parasympathetic activation at 0 Gz and post parabolic 1 Gz.Keywords: humans, heart rate variability, weightlessness, autonomous nervous system, standing. Information on subscribing, and on obtaining copies of an article or of an entire issue. Table of Contents for Volume 72, Number 4 of the ASME journal.
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