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首页> 外文期刊>American Journal of Physiology >Hemodynamics of orthostatic intolerance: implications for gender differences.
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Hemodynamics of orthostatic intolerance: implications for gender differences.

机译：体位不耐受的血流动力学：对性别差异的影响。

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Women have a greater incidence of orthostatic intolerance than men. We hypothesized that this difference is related to hemodynamic effects on regulation of cardiac filling rather than to reduced responsiveness of vascular resistance during orthostatic stress. We constructed Frank-Starling curves from pulmonary capillary wedge pressure (PCWP), stroke volume (SV), and stroke index (SI) during lower body negative pressure (LBNP) and saline infusion in 10 healthy young women and 13 men. Orthostatic tolerance was determined by progressive LBNP to presyncope. LBNP tolerance was significantly lower in women than in men (626.8 +/- 55.0 vs. 927.7 +/- 53.0 mmHg x min, P < 0.01). Women had steeper maximal slopes of Starling curves than men whether expressed as SV (12.5 +/- 2.0 vs. 7.1 +/- 1.5 ml/mmHg, P < 0.05) or normalized as SI (6.31 +/- 0.8 vs. 4.29 +/- 0.6 ml.m-2.mmHg-1, P < 0.05). During progressive LBNP, PCWP dropped quickly at low levels, and reached a plateau at high levels of LBNP near presyncope in allsubjects. SV was 35% and SI was 29% lower in women at presyncope (both P < 0.05). Coincident with the smaller SV, women had higher heart rates but similar mean arterial pressures compared with men at presyncope. Vascular resistance and plasma norepinephrine concentration were similar between genders. We conclude that lower orthostatic tolerance in women is associated with decreased cardiac filling rather than reduced responsiveness of vascular resistance during orthostatic challenges. Thus cardiac mechanics and Frank-Starling relationship may be important mechanisms underlying the gender difference in orthostatic tolerance.
机译：女性比男性的直立性不耐受发生率更高。我们假设这种差异与血液动力学对心脏充盈调节的影响有关，而不是与体位性应激过程中血管阻力的反应性降低有关。我们在10名健康的年轻女性和13名男性的下半身负压（LBNP）和生理盐水注入期间，通过肺毛细血管楔压（PCWP），中风量（SV）和中风指数（SI）构建了Frank-Starling曲线。体位耐受性是通过渐进性LBNP来确定的。女性的LBNP耐受性显着低于男性（626.8 +/- 55.0 vs. 927.7 +/- 53.0 mmHg x min，P <0.01）。无论是用SV（12.5 +/- 2.0 vs. 7.1 +/- 1.5 ml / mmHg，P <0.05）表示或以SI标准化（6.31 +/- 0.8 vs. 4.29 + / -0.6 ml.m-2.mmHg-1，P <0.05）。在进行性LBNP期间，所有受试者的PCWP在低晕前迅速下降，并在晕厥前接近LBNP的高水平。晕厥前女性的SV降低35％，SI降低29％（均P <0.05）。与较小的SV巧合的是，女性在晕厥前的心率较高，但平均动脉压与男性相似。性别之间的血管阻力和血浆去甲肾上腺素浓度相似。我们得出的结论是，女性体位耐受性降低与体位充盈降低而不是体位挑战中血管阻力反应性降低相关。因此，心脏力学和弗兰克-史达琳的关系可能是体位耐受性性别差异背后的重要机制。

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