Freitas J, Santos R M, Figueiredo V, Teixeira E, Carvalho M, de Freitas A F
Centro de Estudos da Função Autonómica, Hospital de S. João, Faculdade de Medicina do Porto, Portugal.
Rev Port Cardiol. 2000 Dec;19(12):1241-74.
Autonomic control of hemodynamics is crucial to maintaining cardiovascular homeostasis after orthostasis. Our goal was to assess the effect of passive orthostatic stress on cardiovascular hemodynamics regulation by analysis of the autonomic nervous system (ANS) and gender influence on the variables. We used a passive 70 degrees tilt test as an orthostatic maneuver. For SNA measurements we used FFT for HRV and SBPV, temporal sequences and alpha index to calculate baroreceptor gain. Hemodynamic data was calculated non-invasively by modelflow. Orthostatic stress induces a rise in heart rate (+15%), total peripheral resistance (+28%), sympathetic tonus (LF_nu: +32%; LF_pas: +64%) and a reduction in cardiac output (-28%), systolic volume (-43%), and vagal activity both tonic (HF_nu:-115%) and reflex (BRG:-103%). Females had higher vagal activity regardless of position. We concluded that the autonomic nervous system plays a crucial role in cardiovascular hemodynamics control to maintain homeostasis after orthostatic stress.
自主神经对血流动力学的控制对于维持体位性低血压后的心血管稳态至关重要。我们的目标是通过分析自主神经系统（ANS）以及性别对变量的影响，来评估被动体位性应激对心血管血流动力学调节的作用。我们采用70度被动倾斜试验作为体位性操作。对于交感神经活动（SNA）测量，我们使用快速傅里叶变换（FFT）来分析心率变异性（HRV）和收缩压变异性（SBPV），利用时间序列和α指数来计算压力感受器增益。血流动力学数据通过模型流无创计算得出。体位性应激会导致心率升高（+15%）、总外周阻力升高（+28%）、交感神经张力升高（低频功率：+32%；低频压力：+64%），以及心输出量降低（-28%）、收缩期容积降低（-43%），并且静息迷走神经活动（高频功率：-115%）和反射性迷走神经活动（压力感受器增益：-103%）均降低。无论处于何种体位，女性的迷走神经活动都更高。我们得出结论，自主神经系统在体位性应激后维持心血管血流动力学稳态的控制中起着关键作用。
