Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia.
Department of Engineering, University of Palermo, Palermo, Italy.
J Appl Physiol (1985). 2020 May 1;128(5):1310-1320. doi: 10.1152/japplphysiol.00512.2019. Epub 2020 Mar 26.
Baroreflex response consists of cardiac chronotropic (effect on heart rate), cardiac inotropic (on contractility), venous (on venous return) and vascular (on vascular resistance) arms. Because of the simplicity of its measurement, the cardiac chronotropic arm is most often analyzed. The aim was to introduce a method to assess the vascular baroreflex arm and to characterize its changes during stress. We evaluated the effect of orthostasis and mental arithmetics (MA) in 39 (22 women, 17 men; median age: 18.7 yr) and 36 (21 women, 15 men; 19.2 yr) healthy volunteers, respectively. We recorded systolic (SBP) and mean (MBP) blood pressure by volume-clamp method and R-R interval (RR) by ECG. Cardiac output (CO) was recorded by impedance cardiography. From MBP and CO, peripheral vascular resistance (PVR) was calculated. The directional spectral coupling and gain of cardiac chronotropic (SBP to RR) and vascular (SBP to PVR) arms were quantified. The strength of the causal coupling from SBP to PVR was significantly higher than that of SBP to RR coupling over the whole protocol ( < 0.001). Along both arms, the coupling was higher during orthostasis compared with the supine position ( < 0.001 and = 0.006); no MA effect was observed. No significant changes in the spectral gain (ratio of RR or PVR change to a unit SBP change) across all phases were found (0.111 ≤ ≤ 0.907). We conclude that changes in PVR are tightly coupled with SBP oscillations via the baroreflex, providing an approach for baroreflex vascular arm analysis with the potential to reveal new aspects of blood pressure dysregulation. Baroreflex response consists of several arms, but the cardiac chronotropic arm (blood pressure changes evoking heart rate response) is usually analyzed. This study introduces a method to assess the vascular baroreflex arm with the continuous noninvasive measurement of peripheral vascular resistance as an output considering causality in the interaction between oscillations and slower dynamics of vascular tone changes. We conclude that although vascular baroreflex arm involvement becomes dominant during orthostasis, gain of this interaction is relatively stable.
压力反射由心脏变时（对心率的影响）、心脏变力（对收缩力的影响）、静脉（对静脉回流的影响）和血管（对血管阻力的影响）组成。由于其测量方法简单，因此通常分析心脏变时臂。目的是引入一种评估血管压力反射臂的方法，并描述其在应激期间的变化。我们分别评估了直立位和心算（MA）对 39 名（22 名女性，17 名男性；中位年龄：18.7 岁）和 36 名（21 名女性，15 名男性；19.2 岁）健康志愿者的影响。我们通过容积钳法记录收缩压（SBP）和平均血压（MBP）和心电图记录 R-R 间隔（RR）。通过阻抗心动图记录心输出量（CO）。从 MBP 和 CO 计算外周血管阻力（PVR）。量化了心脏变时（SBP 至 RR）和血管（SBP 至 PVR）臂的方向谱耦合和增益。SBP 至 PVR 的因果耦合强度明显高于整个方案中的 SBP 至 RR 耦合强度（<0.001）。在整个方案中，两条臂上的耦合在直立位时都高于仰卧位（<0.001 和=0.006）；未观察到 MA 效应。在所有阶段，谱增益（RR 或 PVR 变化与单位 SBP 变化的比值）都没有明显变化（0.111 ≤ ≤0.907）。我们的结论是，通过压力反射，PVR 的变化与 SBP 振荡紧密耦合，为分析压力反射血管臂提供了一种方法，该方法有可能揭示血压调节的新方面。压力反射由几个臂组成，但通常分析心脏变时臂（血压变化引起心率反应）。本研究引入了一种方法，通过连续无创测量外周血管阻力作为输出，同时考虑到血管张力变化的振荡和较慢动力学之间相互作用的因果关系，来评估血管压力反射臂。我们的结论是，尽管在直立位时血管压力反射臂的作用变得占主导地位，但这种相互作用的增益相对稳定。
