Shankhwar Vishwajeet, Urvec Janez, Steuber Bianca, Schmid Zalaudek Karin, Bergauer Andrej, Alsuwaidi Hanan, Du Plessis Stefan, Alsheikh-Ali Alawi, Kellett Catherine, Bayoumi Riad, Blaber Andrew Phillip, Goswami Nandu
College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates.
Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, Slovenia.
Front Cardiovasc Med. 2023 Aug 31;10:1211774. doi: 10.3389/fcvm.2023.1211774. eCollection 2023.
Lower body negative pressure (LBNP) eliminates the impact of weight-bearing muscles on venous return, as well as the vestibular component of cardiovascular and autonomic responses. We evaluated the hemodynamic and autonomic responses to central hypovolemia, induced by LBNP in both males and females.
A total of 44 participants recruited in the study. However, 9 participants did not complete the study protocol. Data from the remaining 35 participants were analysed, 18 males (25.28 ± 3.61 years, 181.50 ± 7.43 cm height, 74.22 ± 9.16 kg weight) and 17 females (22.41 ± 2.73 years, 167.41 ± 6.29 cm height, 59.06 ± 6.91 kg weight). During the experimental protocol, participants underwent three phases, which included 30 min of supine rest, four 4 min intervals of stepwise increases in LBNP from -10 mmHg to -40 mmHg, and 5 min of supine recovery. Throughout the protocol, hemodynamic variables such as blood pressure, heart rate, stroke index, cardiac index, and total peripheral resistance index were continuously monitored. Autonomic variables were calculated from heart rate variability measures, using low and high-frequency spectra, as indicators of sympathetic and parasympathetic activity, respectively.
At rest, males exhibited higher systolic (118.56 ± 9.59 mmHg and 110.03 ± 10.88 mmHg, < 0.05) and mean arterial (89.70 ± 6.86 and 82.65 ± 9.78, < 0.05) blood pressure as compared to females. Different levels of LBNP altered hemodynamic variables in both males and females: heart rate [F(1,16) = 677.46, < 0.001], [F(1,16) = 550.87, < 0.001]; systolic blood pressures [F(1,14) = 3,186.77, < 0.001], [F(1,17) = 1,345.61, < 0.001]; diastolic blood pressure [F(1,16) = 1,669.458, < 0.001], [F(1,16) = 1,127.656, < 0.001]; mean arterial pressures [F(1,16) = 2,330.44, < 0.001], [F(1,16) = 1,815.68, < 0.001], respectively. The increment in heart rates during LBNP was significantly different between both males and females ( = 0.025). The low and high-frequency powers were significantly different for males and females ( = 0.002 and = 0.001, respectively), with the females having a higher increase in low-frequency spectral power.
Cardiovascular activity and autonomic function at rest are influenced by gender. During LBNP application, hemodynamic and autonomic responses differed between genders. These gender-based differences in responses during central hypovolemia could potentially be attributed to the lower sympathetic activity in females. With an increasing number of female crew members in space missions, it is important to understand the role sex-steroid hormones play in the regulation of cardiovascular and autonomic activity, at rest and during LBNP.
下体负压（LBNP）消除了负重肌肉对静脉回流的影响，以及心血管和自主神经反应中的前庭成分。我们评估了男性和女性在LBNP诱导下对中枢性血容量不足的血流动力学和自主神经反应。
本研究共招募了44名参与者。然而，9名参与者未完成研究方案。对其余35名参与者的数据进行了分析，其中18名男性（年龄25.28±3.61岁，身高181.50±7.43厘米，体重74.22±9.16千克）和17名女性（年龄22.41±2.73岁，身高167.41±6.29厘米，体重59.06±6.91千克）。在实验方案中，参与者经历三个阶段，包括30分钟的仰卧休息、四个4分钟的LBNP从-10mmHg逐步增加到-40mmHg的间隔，以及5分钟的仰卧恢复。在整个方案过程中，持续监测血压、心率、每搏指数、心指数和总外周阻力指数等血流动力学变量。自主神经变量通过心率变异性测量计算得出，分别使用低频和高频频谱作为交感神经和副交感神经活动的指标。
静息时，男性的收缩压（分别为118.56±9.59mmHg和110.03±10.88mmHg，P<0.05）和平均动脉压（分别为89.70±6.86和82.65±9.78，P<0.05）高于女性。不同水平的LBNP改变了男性和女性的血流动力学变量：心率[F(1,16)=677.46，P<0.001]，[F(1,16)=550.87，P<0.001]；收缩压[F(1,14)=3186.77，P<0.001]，[F(1,17)=1345.61，P<0.001]；舒张压[F(1,16)=1669.458，P<0.001]，[F(1,16)=1127.656，P<0.001]；平均动脉压[F(1,16)=2330.44，P<0.001]，[F(1,16)=1815.68，P<0.001]。LBNP期间心率的增加在男性和女性之间有显著差异（P=0.025）。男性和女性的低频和高频功率有显著差异（分别为P=0.002和P=0.001），女性的低频频谱功率增加更高。
静息时的心血管活动和自主神经功能受性别影响。在应用LBNP期间，血流动力学和自主神经反应在性别之间存在差异。中枢性血容量不足期间这些基于性别的反应差异可能归因于女性较低的交感神经活动。随着太空任务中女性机组人员数量的增加，了解性甾体激素在静息和LBNP期间对心血管和自主神经活动调节中的作用很重要。
