Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA.
Department of Kinesiology, Iowa State University, Ames, Iowa, USA.
Exp Physiol. 2021 Jul;106(7):1643-1653. doi: 10.1113/EP089319. Epub 2021 May 25.
What is the central question of this study? Does cerebrovascular pulsatility respond differently to acute increases in arterial stiffness in middle-aged compared with young adults? What is the main finding and its importance? Compared with young adults, middle-aged adults exhibited similar changes in cerebral pulsatile damping despite attenuated changes in carotid diameter and cerebrovascular pulsatility during blood pressure-dependent, but not blood pressure-independent, increases in large artery stiffness.
Acute manipulation of arterial stiffness through interventions that increase sympathetic activity might provoke cerebral pulsatility and damping and reveal whether cerebrovascular haemodynamics respond differently to transient elevations in arterial stiffness in middle-aged compared with young adults. We compared cerebral pulsatility and damping in middle-aged versus young adults during two different sympathetic interventions [cold pressor test (CP) and lower-body negative pressure (LBNP)] that increase arterial stiffness acutely. Cerebrovascular haemodynamics were assessed in 15 middle-aged (54 ± 7 years old; 11 female) and 15 sex-matched young adults (25 ± 4 years old) at rest and during the CP test (4 min, 6.4 ± 0.8°C) and LBNP (6 min, -20 mmHg). Mean blood pressure was measured continuously via finger photoplethysmography. Carotid-femoral pulse wave velocity (cfPWV) and carotid stiffness were measured via tonometry and ultrasound. Blood velocity pulsatility index (PI) was measured at the middle cerebral (MCA) and common carotid artery (CCA) using Doppler, with pulsatile damping calculated as CCA PI divided by MCA PI. Increases in cfPWV were driven by changes in mean pressure during CP but not during LBNP in both groups (P < 0.05). Pulsatile damping decreased in both groups (P < 0.05) despite reductions in MCA PI and greater carotid dilatation during CP in young compared with middle-aged adults (P < 0.05). Pressure-independent increases in cfPWV during LBNP did not alter pulsatile damping but decreased MCA PI in both young and middle-aged adults (P < 0.05). These data suggest that changes in carotid diameter and cerebrovascular pulsatility differ between young and middle-aged adults despite similar changes in cerebral pulsatile damping during blood pressure-dependent, but not blood pressure-independent, increases in large artery stiffness.
本研究的核心问题是什么？与年轻人相比，中年人的脑血管搏动在急性动脉僵硬增加时是否会有不同的反应？主要发现及其重要性是什么？与年轻人相比，中年人的大脑搏动阻尼尽管在血压依赖性而非血压独立性的大动脉僵硬增加期间颈动脉直径和脑血管搏动发生了减弱的变化，但在血压依赖性而非血压独立性的大动脉僵硬增加期间，大脑搏动阻尼的变化相似。
通过增加交感神经活性的干预措施来急性操纵动脉僵硬可能会引起大脑搏动和阻尼，并揭示与年轻人相比，中老年人的脑血管血液动力学是否对动脉僵硬的短暂升高有不同的反应。我们比较了中年人与年轻人在两种不同的交感神经干预期间（冷加压试验（CP）和下体负压（LBNP））的大脑搏动和阻尼，这些干预措施会急性增加动脉僵硬。在休息时以及 CP 试验（4 分钟，6.4 ± 0.8°C）和 LBNP（6 分钟，-20mmHg）期间，对 15 名中年（54 ± 7 岁；11 名女性）和 15 名年龄匹配的年轻人进行了脑血管血液动力学评估。连续通过手指光容积描记法测量平均血压。通过张力测量和超声测量颈股脉搏波速度（cfPWV）和颈动脉僵硬度。使用多普勒测量大脑中动脉（MCA）和颈总动脉（CCA）的血流搏动指数（PI），并通过 CCA PI 除以 MCA PI 计算搏动阻尼。CP 期间 cfPWV 的增加是由平均压力的变化驱动的，但在两组中 LBNP 期间都不是（P<0.05）。两组的搏动阻尼均降低（P<0.05），尽管与年轻人相比，中年人在 CP 期间 MCA PI 降低，颈动脉扩张更大（P<0.05）。在 LBNP 期间，cfPWV 的压力独立增加不会改变搏动阻尼，但会降低年轻人和中年人的 MCA PI（P<0.05）。这些数据表明，尽管在血压依赖性而非血压独立性的大动脉僵硬增加期间，颈动脉直径和脑血管搏动的变化在年轻人和中年人之间存在差异，但大脑搏动阻尼的变化相似。
