Kurazumi Takuya, Ogawa Yojiro, Yanagida Ryo, Morisaki Hiroshi, Iwasaki Ken-Ichi
Aerosp Med Hum Perform. 2017 Sep 1;88(9):819-826. doi: 10.3357/AMHP.4870.2017.
Mild hypercapnia combined with a cephalad fluid shift [e.g., that occurring during spaceflight or laparoscopic surgery with head-down tilt (HDT)] might affect cerebral autoregulation. However, no reports have described the effects of the combination on dynamic cerebral autoregulation. Therefore, we tested the hypothesis that the combination of mild hypercapnia and a cephalad fluid shift would attenuate dynamic cerebral autoregulation.
There were 15 healthy male volunteers who were exposed to 4 10-min protocols in which they received air in the supine position (Placebo/Supine), 3% carbon dioxide (CO2) in the supine position (CO2/Supine), air with -10° HDT (Placebo/HDT) and 3% CO2 with -10° HDT (CO2/HDT). Dynamic cerebral autoregulation was evaluated using a transfer function analysis of the beat-to-beat variability in mean arterial blood pressure (ABP) and mean cerebral blood flow (CBF) velocity.
The phase in the low-frequency range was significantly lower during CO2/HDT than all other protocols, where CO2/HDT was -25% lower than Placebo/Supine (CO2/HDT, 0.49 ± 0.21; Placebo/Supine, 0.65 ± 0.16 radians). The transfer function gain in the low-frequency range was significantly higher during CO2/HDT than all other protocols, where CO2/HDT was 26% higher than Placebo/Supine (CO2/HDT, 1.08 ± 0.34; Placebo/Supine, 0.86 ± 0.28 cm · s-1 · mmHg-1). However, neither the CO2/Supine nor Placebo/HDT showed significant differences compared with the Placebo/Supine.
Even short-term exposure to 3% CO2 plus HDT increased synchrony and the magnitude of transmission between ABP and CBF in the low-frequency range. Thus, the combination of mild hypercapnia and a cephalad fluid shift attenuated dynamic cerebral autoregulation.Kurazumi T, Ogawa Y, Yanagida R, Morisaki H, Iwasaki K. Dynamic cerebral autoregulation during the combination of mild hypercapnia and cephalad fluid shift. Aerosp Med Hum Perform. 2017; 88(9):819-826.
轻度高碳酸血症合并头向体液转移（例如在太空飞行或头低脚高位（HDT）腹腔镜手术期间发生的情况）可能会影响脑自动调节。然而，尚无报告描述这种组合对动态脑自动调节的影响。因此，我们检验了以下假设：轻度高碳酸血症与头向体液转移的组合会减弱动态脑自动调节。
15名健康男性志愿者接受了4个10分钟的方案，分别为仰卧位吸入空气（安慰剂/仰卧位）、仰卧位吸入3%二氧化碳（CO2/仰卧位）、-10°HDT时吸入空气（安慰剂/HDT）和-10°HDT时吸入3%CO2（CO2/HDT）。使用逐搏平均动脉血压（ABP）和平均脑血流（CBF）速度变化的传递函数分析来评估动态脑自动调节。
CO2/HDT期间低频范围内的相位显著低于所有其他方案，其中CO2/HDT比安慰剂/仰卧位低25%（CO2/HDT，0.49±0.21；安慰剂/仰卧位，0.65±0.16弧度）。CO2/HDT期间低频范围内的传递函数增益显著高于所有其他方案，其中CO2/HDT比安慰剂/仰卧位高26%（CO2/HDT，1.08±0.34；安慰剂/仰卧位，0.86±0.28 cm·s-1·mmHg-1）。然而，CO2/仰卧位和安慰剂/HDT与安慰剂/仰卧位相比均未显示出显著差异。
即使短期暴露于3%CO2加HDT也会增加低频范围内ABP和CBF之间的同步性和传输幅度。因此，轻度高碳酸血症与头向体液转移的组合会减弱动态脑自动调节。
仓桥 彻、小川 洋、柳田 瑠璃、森崎 浩、岩崎 健。轻度高碳酸血症与头向体液转移组合期间的动态脑自动调节。航空航天医学与人类表现。2017；88（9）：819 - 826。
