School of Kinesiology and Health Science, York University, 355 Bethune College, 4700 Keele St, Toronto, ON, M3J 1P3, Canada.
Muscle Health Research Centre, York University, Toronto, ON, Canada.
Sci Rep. 2021 Jan 25;11(1):2162. doi: 10.1038/s41598-021-81837-w.
Head-down bed rest (HDBR) has previously been shown to alter cerebrovascular and autonomic control. Previous work found that sustained HDBR (≥ 20 days) attenuates the hypercapnic ventilatory response (HCVR); however, little is known about shorter-term effects of HDBR nor the influence of HDBR on the hypoxic ventilatory response (HVR). We investigated the effect of 4-h HDBR on HCVR and HVR and hypothesized attenuated ventilatory responses due to greater carotid and brain blood flow. Cardiorespiratory responses of young men (n = 11) and women (n = 3) to 5% CO or 10% O before and after 4-h HDBR were examined. HDBR resulted in lower HR, lower cardiac output index, lower common carotid artery flow, higher SpO, and higher pulse wave velocity. After HDBR, tidal volume and ventilation responses to 5% CO were enhanced (all P < 0.05), yet no other changes in cardiorespiratory variables were evident. There was no influence of HDBR on the cardiorespiratory responses to hypoxia (all P > 0.05). Short-duration HDBR does not alter the HVR, yet enhances the HCVR, which we hypothesize is a consequence of cephalic CO accumulation from cerebral congestion.
头低位卧床休息（HDBR）先前已被证明会改变脑血管和自主控制。先前的工作发现，持续的 HDBR（≥20 天）会减弱高碳酸血症通气反应（HCVR）；然而，对于 HDBR 的短期影响以及 HDBR 对低氧通气反应（HVR）的影响知之甚少。我们研究了 4 小时 HDBR 对 HCVR 和 HVR 的影响，并假设由于颈动脉和脑血流量增加，通气反应会减弱。在 HDBR 前后，我们检查了年轻男性（n=11）和女性（n=3）对 5% CO 或 10% O 的心肺呼吸反应。HDBR 导致 HR 降低、心输出量指数降低、颈总动脉血流量降低、SpO 升高和脉搏波速度升高。HDBR 后，潮气量和对 5% CO 的通气反应增强（均 P<0.05），但其他心肺变量没有明显变化。HDBR 对缺氧时的心肺反应没有影响（均 P>0.05）。短时间 HDBR 不会改变 HVR，但会增强 HCVR，我们假设这是由于头部充血导致的颅内 CO 积聚的结果。
