Human vagal baroreflex mechanisms in space
Human vagal baroreflex mechanisms in space
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DOI：
10.1113/jphysiol.2009.186650
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发表时间：
2010-04-01
影响因子：
5.5
通讯作者：
Goble, Ross
中科院分区：
文献类型：
--
作者：
Eckberg, Dwain L.;Halliwill, John R.;Goble, Ross
虽然宇航员在太空中的心血管功能是正常的，但许多人在返回地球后对站立的血液动力学反应发生了改变，包括过度的心动过速，直立性低血压和罕见的晕厥。模拟微重力损害迷走神经压力感受器-心脏反射功能并引起直立性低血压。然而，实际的微重力已被证明增加或不改变迷走神经压力反射增益。在这项研究中，我们测试了空假设，太空飞行不会损害人类压力感受器反射机制。我们研究了11名美国和两名德国宇航员之前，期间（飞行第2-8天），两个，9-和10天的航天飞机任务后，分级颈部压力和吸力，引起乙状结肠，迷走神经介导的颈动脉压力感受性反射R-R间期反应。太空中的基线收缩压往往高于地球（P = 0.015，重复测量方差分析），基线R-R间期往往较低（P = 0.049）。压力感受器-心脏反射关系在空间上沿R-R间期轴向下移位。在飞行第8天，R-R间期对颈部压力变化的反应的平均范围从飞行前水平下降了37%（P = 0.051），最大R-R间期下降了14%（P = 0.003），迷走神经压力反射增加了9%（P = 0.009）。这些测量在宇航员返回地球后7-10天恢复到飞行前的水平。本研究记录了空间中动脉压的显著升高和迷走神经压力反射功能的损害。这些结果和早些时候发表的结果表明，微重力暴露增强了交感神经，减少了迷走神经对心血管的影响。
Although astronauts' cardiovascular function is normal while they are in space, many have altered haemodynamic responses to standing after they return to Earth, including inordinate tachycardia, orthostatic hypotension, and uncommonly, syncope. Simulated microgravity impairs vagal baroreceptor-cardiac reflex function and causes orthostatic hypotension. Actual microgravity, however, has been shown to either increase, or not change vagal baroreflex gain. In this study, we tested the null hypothesis that spaceflight does not impair human baroreflex mechanisms. We studied 11 American and two German astronauts before, during (flight days 2-8), and after two, 9- and 10-day space shuttle missions, with graded neck pressure and suction, to elicit sigmoid, vagally mediated carotid baroreflex R-R interval responses. Baseline systolic pressures tended to be higher in space than on Earth (P = 0.015, repeated measures analysis of variance), and baseline R-R intervals tended to be lower (P = 0.049). Baroreceptor-cardiac reflex relations were displaced downward on the R-R interval axis in space. The average range of R-R interval responses to neck pressure changes declined from preflight levels by 37% on flight day 8 (P = 0.051), maximum R-R intervals declined by 14% (P = 0.003), and vagal baroreflex gain by 9% (P = 0.009). These measures returned to preflight levels by 7-10 days after astronauts returned to Earth. This study documents significant increases of arterial pressure and impairment of vagal baroreflex function in space. These results and results published earlier indicate that microgravity exposure augments sympathetic, and diminishes vagal cardiovascular influences.