Spencer Matthew D, Tyndall Amanda V, Davenport Margie H, Argourd Laurie, Anderson Todd J, Eskes Gail A, Friedenreich Christine M, Hogan David B, Leigh Richard, Meshi Bernard, Smith Eric E, Wilson Ben J, Wilton Stephen B, Poulin Marc J
Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
PLoS One. 2015 Nov 23;10(11):e0143059. doi: 10.1371/journal.pone.0143059. eCollection 2015.
The primary purpose of this Brain in Motion (BIM) sub-study was to determine the 6-month stability of resting blood flow velocity and cerebrovascular responsiveness to a euoxic hypercapnic challenge in a group of physically inactive community dwelling men and men aged ≥55 yrs (range 55-92 yrs). At baseline and 6 months later 88 women (65±6 yr) and 78 men (67±7 yr) completed a hypercapnic challenge (step changes from resting end-tidal PCO2 ((PETCO2) to +1, +5 and +8 mmHg above rest) while cerebral blood flow velocity was assessed using transcranial Doppler ultrasound. Peak velocity of the middle cerebral artery (MCAv) was increased (p<0.05) at the second visit during rest (51±2 vs. 52±4); however, these differences were abolished (p>0.05) when MCAv was normalized to PETCO2. During hypercapnia, MCAv tended to be increased at follow-up, but this finding was absent when MCAv/PETCO2 was compared across time. Cerebrovascular reactivity (i.e., ΔMCAv/ΔPETCO2) was similar (p>0.05) between testing occasions regardless of the approach taken (i.e., considering only the lower step [from +1 to +5 mmHg]; the upper step [+5 to +8 mmHg]; or the complete test taken together). In conclusion, this study has shown that cerebral blood flow and cerebrovascular responsiveness to acute euoxic hypercapnia are stable in older, healthy adults over a 6-month period. Modest changes in MCAv over time must be viewed in the context of underlying differences in PETCO2, an important finding with implications for future studies considering cerebral blood flow velocity.
这项“运动中的大脑”（BIM）子研究的主要目的是确定一组身体不活跃的社区居住男性以及年龄≥55岁（范围为55 - 92岁）的男性静息血流速度和脑血管对低氧高碳酸血症激发试验的反应在6个月内的稳定性。在基线期和6个月后，88名女性（65±6岁）和78名男性（67±7岁）完成了高碳酸血症激发试验（从静息呼气末二氧化碳分压（PETCO2）逐步变化至比静息值高+1、+5和+8 mmHg），同时使用经颅多普勒超声评估脑血流速度。在第二次就诊时，静息状态下大脑中动脉的峰值速度（MCAv）有所增加（p<0.05）（51±2 vs. 52±4）；然而，当MCAv根据PETCO2进行标准化后，这些差异消失了（p>0.05）。在高碳酸血症期间，随访时MCAv有增加的趋势，但当比较不同时间的MCAv/PETCO2时，这一发现并不明显。无论采用何种方法（即仅考虑较低的步长[从+1至+5 mmHg]；较高的步长[+5至+8 mmHg]；或一起考虑整个测试），测试期间的脑血管反应性（即ΔMCAv/ΔPETCO2）相似（p>0.05）。总之，本研究表明，在6个月的时间里，老年健康成年人的脑血流和脑血管对急性低氧高碳酸血症的反应是稳定的。随着时间推移MCAv的适度变化必须结合PETCO2的潜在差异来看待，这一重要发现对未来考虑脑血流速度的研究具有启示意义。
