Brain and central haemodynamics and oxygenation during maximal exercise in humans
Brain and central haemodynamics and oxygenation during maximal exercise in humans
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DOI：
10.1113/jphysiol.2004.060574
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发表时间：
2004-05-15
影响因子：
5.5
通讯作者：
Secher, NH
中科院分区：
文献类型：
--
作者：
González-Alonso, J;Dalsgaard, MK;Secher, NH
在人类进行最大程度的运动时，疲劳之前会出现全身肌肉和骨骼肌血流量、O-2 输送和吸收的减少。在这里，我们检查了人脑对 O-2 和底物的摄取是否受到损害，以及全身 O-2 输送下降引起的心脏每搏输出量下降是否与静脉回流下降有关。我们测量了健康男性（2 项研究中 n = 13）的大脑和中枢血流动力学和氧合情况，这些男性在高（H）或正常（对照，C）体温下进行剧烈自行车运动（360 +/- 10 W；平均值 +/- s.e.m.）直至精疲力尽。尽管心率达到相似的最大值，但 H 组的力竭时间比 C 组短（5.8 +/- 0.2 与 7.5 +/- 0.4 分钟，P < 0.05）。在两项试验的前 90 秒内，额叶皮层组织氧合以及 O-2 和葡萄糖的动脉-颈内静脉差异 (a-v diff) 没有变化，而大脑中动脉平均流速 (MCA V-mean) 和心输出量分别增加了约 22% 和约 115%。此后，脑提取的 O-2、葡萄糖和乳酸分别增加了约 45、约 55 和约 95%，而额皮质组织氧合、MCA V 平均值和心输出量分别下降约 40、约 15 和约 10%。在这两项试验中，在力竭时，全身摄氧量下降，每搏输出量和中心静脉压也有类似下降。然而大脑对O-2、葡萄糖和乳酸的摄取增加了。总之，每搏输出量的减少是力竭前全身 O-2 输送和吸收下降的基础，部分与心脏静脉回流减少有关。此外，在健康人中，无论有或没有热应激，最大运动期间的疲劳与O-2和底物的大脑摄取增强而不是受损相关。
During maximal exercise in humans, fatigue is preceded by reductions in systemic and skeletal muscle blood flow, O-2 delivery and uptake. Here, we examined whether the uptake Of O-2 and substrates by the human brain is compromised and whether the fall in stroke volume of the heart underlying the decline in systemic O-2 delivery is related to declining venous return. We measured brain and central haemodynamics and oxygenation in healthy males (n = 13 in 2 studies) performing intense cycling exercise (360 +/- 10 W; mean +/- s.e.m.) to exhaustion starting with either high (H) or normal (control, C) body temperature. Time to exhaustion was shorter in H than in C (5.8 +/- 0.2 versus 7.5 +/- 0.4 min, P < 0.05), despite heart rate reaching similar maximal values. During the first 90 s of both trials, frontal cortex tissue oxygenation and the arterial-internal jugular venous differences (a-v diff) for O-2 and glucose did not change, whereas middle cerebral artery mean flow velocity (MCA V-mean) and cardiac output increased by similar to22 and similar to115%, respectively. Thereafter, brain extraction Of O-2, glucose and lactate increased by similar to45,similar to55 and similar to95%, respectively, while frontal cortex tissue oxygenation, MCA V-mean and cardiac output declined similar to40, similar to15 and similar to10%, respectively. At exhaustion in both trials, systemic V-O2 declined in parallel with a similar fall in stroke volume and central venous pressure; yet the brain uptake Of O-2, glucose and lactate increased. In conclusion, the reduction in stroke volume, which underlies the fall in systemic O-2 delivery and uptake before exhaustion, is partly related to reductions in venous return to the heart. Furthermore, fatigue during maximal exercise, with or without heat stress, in healthy humans is associated with an enhanced rather than impaired brain uptake Of O-2 and substrates.