下体负压耐受性的性别差异。

Gender differences in tolerance to lower body negative pressure.

作者信息

Gotshall R W

机构信息

Colorado State University, Department of Health and Exercise Science, Fort Collins 80523-1582, USA.

出版信息

Aviat Space Environ Med. 2000 Nov;71(11):1104-10.

PMID:11086663

Abstract

BACKGROUND

Previous studies suggest that women have lower tolerance than men do to lower body negative pressure (LBNP). The mechanism(s) responsible has not been determined.

HYPOTHESES

Women would be less tolerant to presyncopal LBNP than men as determined by several indices of LBNP tolerance. Additionally, men and women, regardless of LBNP tolerance, would have similar cardiovascular responses to LBNP as presyncope was reached.

METHODS

The subjects were 18 men and 18 women (average age 25) of similar fitness levels who volunteered for the study. A step-wise LBNP protocol to presyncope was employed. HR, stroke volume (SV), cardiac output (Q), BP, and systemic vascular resistance (SVR) were measured before and throughout the LBNP stress. Data from women were compared with those from all men, and to men with similar and higher LBNP tolerance.

RESULTS

Women had significantly less LBNP tolerance than men regardless of index used: 30% less by duration of LBNP, 21% less by maximal LBNP tolerated, 44% less by a cumulative stress index, and 27% less by a linear tolerance index. Cardiovascular responses to LBNP were similar for women and men as presyncope was approached, whether the men were low-tolerant (LT) or high-tolerant (HT). In the 2 min pre-presyncope, HR increased by 80 +/- 6% in women, 72 +/- 7% in LT men and 96 +/- 14% in HT men; Q decreased by 47 +/- 3% in women, 52 +/- 6% in LT men and 55 +/- 2% in HT men. Similar comparisons occurred for the decline in BP and the rise in SVR.

CONCLUSION

Women have lower LBNP tolerance than do men, although there is considerable gender overlap in tolerances. The cardiovascular response to LBNP is similar regardless of gender or tolerance level as presyncope is approached. Understanding the gender differences in LBNP tolerance may lie in determining how the LBNP stress is translated into a "trigger" for cardiovascular decompensation.

摘要

背景

先前的研究表明，女性对下体负压（LBNP）的耐受性低于男性。其相关机制尚未确定。

假设

根据LBNP耐受性的多项指标，女性对晕厥前期LBNP的耐受性低于男性。此外，无论LBNP耐受性如何，男性和女性在接近晕厥前期时对LBNP的心血管反应相似。

方法

研究对象为18名男性和18名女性（平均年龄25岁），他们身体健康状况相似且自愿参与该研究。采用逐步增加LBNP直至晕厥前期的方案。在LBNP应激前及整个过程中测量心率（HR）、每搏输出量（SV）、心输出量（Q）、血压（BP）和全身血管阻力（SVR）。将女性的数据与所有男性的数据进行比较，并与LBNP耐受性相似及更高的男性进行比较。

结果

无论使用何种指标，女性的LBNP耐受性均显著低于男性：LBNP持续时间少30%，最大耐受LBNP少21%，累积应激指数少44%，线性耐受性指数少27%。接近晕厥前期时，无论男性的耐受性是低（LT）还是高（HT），女性和男性对LBNP的心血管反应相似。在晕厥前期前2分钟，女性的HR增加80±6%，LT男性增加72±7%，HT男性增加96±14%；女性的Q减少47±3%，LT男性减少52±6%，HT男性减少55±2%。血压下降和SVR升高也有类似的比较结果。