Hirayanagi Kaname, Iwase Satoshi, Kamiya Atsunori, Sasaki Tsuyoshi, Mano Tadaaki, Yajima Kazuyoshi
Department of Hygiene and Space Medicine, Nihon University School of Medicine, Itabashi, 173-8610 Tokyo, Japan.
Eur J Appl Physiol. 2004 Jun;92(1-2):160-7. doi: 10.1007/s00421-004-1067-8. Epub 2004 Mar 20.
We studied the effects of 14 days of 6 degrees 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 (HF(RRI)) 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 BRS(sequence) obtained by the sequence technique showed a significant increase temporarily on the initial day of HDBR. The BRS(sequence) 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 HF(RRI) 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.
我们研究了16名健康男性受试者进行14天6°头低位卧床休息（HDBR）的影响，以检查自主神经系统的功能变化和心脏压力感受器反射反应，重点关注HDBR期间的动态变化。在仰卧休息姿势下，通过同步连续记录心电图和动脉压力波，无创测量逐搏RR间期（RRIs）和收缩期动脉压（SAPs）。将快速傅里叶变换的功率谱分析应用于由512个插值RRIs和512个SAPs（持续时间256秒）组成的数据集。通过对自发RRIs和SAPs应用序列技术和互谱分析技术，获得了三个心脏压力感受器反射敏感性（BRS）指标。RRIs变异性的高频带功率（HF(RRI)）在HDBR后期显著降低，并持续到HDBR后时期（POST）的初始阶段。SAP变异性的低频带功率仅在HDBR中期显著降低。通过序列技术获得的BRS(序列)在HDBR初始日暂时显著增加。通过处理高频带的互谱分析获得的BRS(序列)和BRS估计值在POST初始日均显著降低。在HDBR和POST期间，每个BRS估计值与心率呈负相关，与HF(RRI)呈正相关。这些结果表明：（1）心脏自发压力感受器反射敏感性可能在HDBR初始阶段短暂增加；（2）从HDBR后期到POST初始阶段，窦房结的迷走神经调制减弱；（3）在HDBR中期，交感血管运动控制可能略有抑制；（4）在POST初始阶段，心脏交感神经调制增强，心脏自发压力感受器反射敏感性受损。
