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首页> 外文期刊>American Journal of Physiology >Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude.
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Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude.

机译：在适应海拔高度的低地车上，血浆容量的增加不会增加最大心输出量或VO2 max。

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摘要

With altitude acclimatization, blood hemoglobin concentration increases while plasma volume (PV) and maximal cardiac output (Qmax) decrease. This investigation aimed to determine whether reduction of Qmax at altitude is due to low circulating blood volume (BV). Eight Danish lowlanders (3 females, 5 males: age 24.0 +/- 0.6 yr; mean +/- SE) performed submaximal and maximal exercise on a cycle ergometer after 9 wk at 5,260 m altitude (Mt. Chacaltaya, Bolivia). This was done first with BV resulting from acclimatization (BV = 5.40 +/- 0.39 liters) and again 2-4 days later, 1 h after PV expansion with 1 liter of 6% dextran 70 (BV = 6.32 +/- 0.34 liters). PV expansion had no effect on Qmax, maximal O2 consumption (VO2), and exercise capacity. Despite maximal systemic O2 transport being reduced 19% due to hemodilution after PV expansion, whole body VO2 was maintained by greater systemic O2 extraction (P < 0.05). Leg blood flow was elevated (P < 0.05) in hypervolemic conditions, which compensated for hemodilution resulting in similar leg O2 delivery and leg VO2 during exercise regardless of PV. Pulmonary ventilation, gas exchange, and acid-base balance were essentially unaffected by PV expansion. Sea level Qmax and exercise capacity were restored with hyperoxia at altitude independently of BV. Low BV is not a primary cause for reduction of Qmax at altitude when acclimatized. Furthermore, hemodilution caused by PV expansion at altitude is compensated for by increased systemic O2 extraction with similar peak muscular O2 delivery, such that maximal exercise capacity is unaffected.
机译：随着海拔高度适应，血液中的血红蛋白浓度增加，而血浆容量（PV）和最大心输出量（Qmax）降低。这项研究旨在确定海拔高度Qmax的降低是否是由于低循环血容量（BV）引起的。八名丹麦低地居民（3名女性，5名男性：24.0 +/- 0.6岁;平均+/- SE）在海拔5260 m（玻利维亚，查卡尔塔亚山）上9周后在自行车测功机上进行了次最大和最大运动。首先用适应环境的BV（BV = 5.40 +/- 0.39升）进行此操作，然后再2-4天后，用1升6％的葡聚糖70进行PV膨胀后1小时（BV = 6.32 +/- 0.34升） 。 PV膨胀对Qmax，最大O2消耗量（VO2）和运动能力没有影响。尽管由于PV扩张后的血液稀释，最大的全身性O2转运减少了19％，但全身性的O2仍通过更大程度的全身性O2提取得以维持（P <0.05）。在高血容量的情况下，腿部血流升高（P <0.05），这补偿了血液稀释，从而导致运动期间无论PV如何，腿部O2的输送和腿部VO2的相似性。肺部通气，气体交换和酸碱平衡基本上不受PV膨胀的影响。高氧使海拔Qmax和运动能力得到恢复，而与BV无关。适应时，低BV并不是海拔Qmax降低的主要原因。此外，由高海拔PV扩张引起的血液稀释可通过增加全身O2提取量（具有相似的峰值肌肉O2输送量）来补偿，因此最大运动能力不会受到影响。

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