TY - JOUR
T1 - Functional changes in autonomic nervous system and baroreceptor reflex induced by 14 days of 6° head-down bed rest
AU - Hirayanagi, Kaname
AU - Iwase, Satoshi
AU - Kamiya, Atsunori
AU - Sasaki, Tsuyoshi
AU - Mano, Tadaaki
AU - Yajima, Kazuyoshi
N1 - Funding Information:
Acknowledgements We acknowledge the support of the Man– Vehicle Laboratory of the Massachusetts Institute of Technology, through the National Space Biomedical Research Institute (NASA Grant NCC 9-58), in the preparation of the manuscript. We would like to express our appreciation to Dr. Y. Watanabe, to the nurses and staff at the Faculty of Health Science at Nagoya University, and to the 16 subjects in this study. This study was carried out as a part of the ‘‘Ground Research Announcement for Space Utilization’’ promoted by the Japan Space Forum.
PY - 2004/6
Y1 - 2004/6
N2 - We studied the effects of 14 days of 6° head-down bed rest (HDBR) in 16 healthy male subjects to examine the functional changes in the autonomic nervous system and cardiac baroreceptor reflex response with an emphasis on dynamic changes during HDBR. Beat-by-beat RR intervals (RRIs) and systolic arterial pressures (SAPs) were measured non-invasively from simultaneous, continuous recordings of ECG and arterial pressure waves in supine resting postures. A power spectrum analysis by the fast Fourier transform was applied to a data set composed of interpolated 512 RRIs and 512 SAPs (256 s in duration). Three indices of cardiac baroreceptor reflex sensitivity (BRS) were obtained by applying a sequence technique and a cross-spectrum analysis technique to the spontaneous RRIs and SAPs. The high-frequency band power of RRI variability (HFRRI) decreased significantly in the latter part of HDBR and persisted until the initial stage of the post-HDBR period (POST). The low-frequency band power of SAP variability decreased significantly only during the mid-part of HDBR. The BRSsequence obtained by the sequence technique showed a significant increase temporarily on the initial day of HDBR. The BRSsequence and the estimate of BRS obtained by the cross-spectrum analysis handling the high-frequency band were both significantly decreased on the initial day of POST. Each of the BRS estimates correlated negatively with heart rate and positively with HFRRI during HDBR and POST. These results suggest the following: (1) cardiac spontaneous baroreceptor reflex sensitivity might be transiently increased at the initial stage of HDBR, (2) the reduction in vagal modulation on the sinus node occurs from the latter part of HDBR to the initial stage of POST, (3) sympathetic vasomotor control is probably slightly inhibited during the mid-part of HDBR, and (4) the enhancement in cardiac sympathetic modulation and the impairment in cardiac spontaneous baroreceptor reflex sensitivity may occur in the initial stage of POST.
AB - We studied the effects of 14 days of 6° head-down bed rest (HDBR) in 16 healthy male subjects to examine the functional changes in the autonomic nervous system and cardiac baroreceptor reflex response with an emphasis on dynamic changes during HDBR. Beat-by-beat RR intervals (RRIs) and systolic arterial pressures (SAPs) were measured non-invasively from simultaneous, continuous recordings of ECG and arterial pressure waves in supine resting postures. A power spectrum analysis by the fast Fourier transform was applied to a data set composed of interpolated 512 RRIs and 512 SAPs (256 s in duration). Three indices of cardiac baroreceptor reflex sensitivity (BRS) were obtained by applying a sequence technique and a cross-spectrum analysis technique to the spontaneous RRIs and SAPs. The high-frequency band power of RRI variability (HFRRI) decreased significantly in the latter part of HDBR and persisted until the initial stage of the post-HDBR period (POST). The low-frequency band power of SAP variability decreased significantly only during the mid-part of HDBR. The BRSsequence obtained by the sequence technique showed a significant increase temporarily on the initial day of HDBR. The BRSsequence and the estimate of BRS obtained by the cross-spectrum analysis handling the high-frequency band were both significantly decreased on the initial day of POST. Each of the BRS estimates correlated negatively with heart rate and positively with HFRRI during HDBR and POST. These results suggest the following: (1) cardiac spontaneous baroreceptor reflex sensitivity might be transiently increased at the initial stage of HDBR, (2) the reduction in vagal modulation on the sinus node occurs from the latter part of HDBR to the initial stage of POST, (3) sympathetic vasomotor control is probably slightly inhibited during the mid-part of HDBR, and (4) the enhancement in cardiac sympathetic modulation and the impairment in cardiac spontaneous baroreceptor reflex sensitivity may occur in the initial stage of POST.
KW - Arterial pressure variability
KW - Autonomic nervous function
KW - Baroreceptor function
KW - Head-down bed rest
KW - Heart rate variability
UR - http://www.scopus.com/inward/record.url?scp=3042814724&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=3042814724&partnerID=8YFLogxK
U2 - 10.1007/s00421-004-1067-8
DO - 10.1007/s00421-004-1067-8
M3 - Article
C2 - 15042373
AN - SCOPUS:3042814724
SN - 1439-6319
VL - 92
SP - 160
EP - 167
JO - European Journal of Applied Physiology
JF - European Journal of Applied Physiology
IS - 1-2
ER -
