Länne T, Olsen H
Department of Vascular and Renal Diseases, Malmö University Hospital, Lund University, Sweden.
Acta Physiol Scand. 1997 Dec;161(4):503-7. doi: 10.1046/j.1365-201X.1997.00243.x.
The cardiovascular regulation in humans depends to a major extent on sympathetic reflexes originating from volume receptors in the arterial as well as the cardiopulmonary region. With experimental approaches, such as lower body negative pressure (LBNP) and tilting, signs of reduced efficiency with ageing have been shown. However, a confounding factor may be an age-related decline in venous capacitance response of the lower limbs, reducing the decrease in central blood volume and thus the deactivation of baro/cardiopulmonary receptors. This potential error was addressed in the present study. Central hypovolaemic stress was produced by LBNP 60 cmH2O in 10 young (mean age 23, range 20-25 years) and 10 old males (mean age 65, range 61-70 years). Changes in tissue volume of the calf were studied by strain gauge volumetric technique. Transmission of negative pressure to the calf muscle was studied in two young and two old volunteers. The haemodynamic response to hypovolaemic circulatory stress was attenuated in the old as compared with the young subjects, with a less marked increase in heart rate and peripheral resistance. Further, in the old subjects, the decrease in systolic blood pressure, pulse pressure and forearm blood flow was attenuated. Transmission of negative pressure to the calf was equal in both groups. The capacitance response was reduced with age from 2.27 +/- 0.14 to 1.64 +/- 0.13 mL 100 mL-1 (P < 0.005). However, the net capillary fluid filtration was unchanged. The reduced capacitance function might partly explain the declining reflex responses with age in humans, and thus seems to be of considerable importance when studying cardiovascular sympathetic reflex responses in ageing.
人类的心血管调节在很大程度上依赖于源自动脉以及心肺区域容量感受器的交感反射。通过诸如下体负压（LBNP）和倾斜等实验方法，已显示出随着年龄增长效率降低的迹象。然而，一个混杂因素可能是下肢静脉容量反应随年龄的下降，这减少了中心血容量的减少，从而减少了压力/心肺感受器的失活。本研究解决了这一潜在误差。对10名年轻男性（平均年龄23岁，范围20 - 25岁）和10名老年男性（平均年龄65岁，范围61 - 70岁）施加60 cmH2O的下体负压以产生中心低血容量应激。通过应变片容积技术研究小腿组织体积的变化。在两名年轻和两名老年志愿者中研究了负压向小腿肌肉的传导。与年轻受试者相比，老年受试者对低血容量循环应激的血流动力学反应减弱，心率和外周阻力的增加不太明显。此外，在老年受试者中，收缩压、脉压和前臂血流量的下降减弱。两组中负压向小腿的传导相等。随着年龄增长，容量反应从2.27±0.14降至1.64±0.13 mL 100 mL-1（P < 0.005）。然而，净毛细血管滤过液未改变。容量功能的降低可能部分解释了人类随年龄增长反射反应的下降，因此在研究衰老过程中的心血管交感反射反应时似乎具有相当重要的意义。
