Zhang Qingguang, Evans Joyce M, Stenger Michael B, Moore Fritz B, Knapp Charles F
Aerosp Med Hum Perform. 2017 Sep 1;88(9):827-833. doi: 10.3357/AMHP.4811.2017.
Intermittent artificial gravity (AG) training over days and weeks has been shown to improve the human orthostatic tolerance limit (OTL) and improve cardiovascular regulation in response to orthostatic stress. Effects of a single AG exposure are currently unknown.
We tested cardiovascular responses to orthostatic stress in 16 hypovolemic subjects (9 men and 7 women), once following a single, short (∼90 min) bout of AG and once following a similar period of head-down bed rest (HDBR). Hypovolemia was produced by intravenous furosemide infusion (20 mg) and orthostatic stress was produced by combined 70° head-up tilt (HUT) and progressively increasing lower body negative pressure until symptoms of presyncope developed. To assess reflex-induced changes in cardiovascular regulation, heart rate and blood pressure variability were analyzed by spectral analysis and baroreflex activity was evaluated by transfer function analysis.
Compared to HDBR, a short AG exposure increased men's low frequency (0.04-0.15 Hz) power of systolic blood pressure (SBPLF), but did not change women's SBPLF responses to orthostatic stress. In response to 70° HUT, compared to supine, low frequency phase delay (PhaseLF) between systolic blood pressure and RR intervals increased by ∼20% following HDBR, but did not change following AG, reflecting improved baroreflex activity at a milder level of orthostatic stress after AG.
These results indicate that a short bout of AG increased both sympathetic and baroreflex responsiveness to orthostatic stress in hypovolemia-induced, cardiovascular-deconditioned men and women, which may contribute to the AG-induced improvement of OTL shown in our previous reports.Zhang Q, Evans JM, Stenger MB, Moore FB, Knapp CF. Autonomic cardiovascular responses to orthostatic stress after a short artificial gravity exposure. Aerosp Med Hum Perform. 2017; 88(9):827-833.
数天至数周的间歇性人工重力（AG）训练已被证明可提高人体的立位耐力极限（OTL），并改善心血管系统对直立位应激的调节。目前尚不清楚单次AG暴露的影响。
我们测试了16名血容量不足的受试者（9名男性和7名女性）对直立位应激的心血管反应，一次是在单次短暂（约90分钟）的AG暴露后，另一次是在类似时长的头低位卧床休息（HDBR）后。通过静脉输注速尿（20毫克）造成血容量不足，通过70°头高位倾斜（HUT）并逐渐增加下体负压直至出现前驱晕厥症状来产生直立位应激。为了评估反射引起的心血管调节变化，通过频谱分析分析心率和血压变异性，并通过传递函数分析评估压力反射活动。
与HDBR相比，短暂的AG暴露增加了男性收缩压的低频（0.04 - 0.15赫兹）功率（SBPLF），但没有改变女性对直立位应激的SBPLF反应。在70°HUT时，与仰卧位相比，HDBR后收缩压与RR间期之间的低频相位延迟（PhaseLF）增加了约20%，但AG后未发生变化，这反映出AG后在较轻程度的直立位应激下压力反射活动得到改善。
这些结果表明，在血容量不足引起的心血管功能失调的男性和女性中，单次短暂的AG暴露增加了对直立位应激的交感神经和压力反射反应性，这可能有助于我们之前报道中AG诱导的OTL改善。张Q、埃文斯JM、斯滕格MB、摩尔FB、克纳普CF。短暂人工重力暴露后对直立位应激的自主心血管反应。航空航天医学与人类表现。2017；88（9）：827 - 833。
