Groothuis Jan T, van Dijk Nynke, Ter Woerds Walter, Wieling Wouter, Hopman Maria T E
Department of Physiology, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Clin Sci (Lond). 2007 Feb;112(3):193-201. doi: 10.1042/CS20060241.
In patients with orthostatic intolerance, the mechanisms to maintain BP (blood pressure) fail. A physical counter-manoeuvre to postpone or even prevent orthostatic intolerance in these patients is leg crossing combined with muscle tensing. Although the central haemodynamic effects of physical counter-manoeuvres are well documented, not much is known about the peripheral haemodynamic events. Therefore the purpose of the present study was to examine the peripheral haemodynamic effects of leg crossing combined with muscle tensing during 70 degrees head-up tilt. Healthy subjects (n=13) were monitored for 10 min in the supine position followed by 10 min in 70 degrees head-up tilt and, finally, for 2 min of leg crossing with muscle tensing in 70 degrees head-up tilt. MAP (mean arterial BP), heart rate, stroke volume, cardiac output and total peripheral resistance were measured continuously by Portapres. Leg blood flow was measured using Doppler ultrasound. Leg vascular conductance was calculated as leg blood flow/MAP. A significant increase in MAP (13 mmHg), stroke volume (27%) and cardiac output (18%), a significant decrease in heart rate (-5 beats/min) and no change in total peripheral resistance during the physical counter-manoeuvre were observed when compared with baseline 70 degrees head-up tilt. A significant increase in leg blood flow (325 ml/min) and leg vascular conductance (2.9 arbitrary units) were seen during the physical counter-manoeuvre when compared with baseline 70 degrees head-up tilt. In conclusion, the present study indicates that the physical counter-manoeuvre of leg crossing combined with muscle tensing clearly enhances leg blood flow and, at the same time, elevates MAP.
在体位性不耐受患者中，维持血压（BP）的机制失效。一种推迟甚至预防这些患者体位性不耐受的身体应对策略是双腿交叉并伴有肌肉紧张。尽管身体应对策略对中心血流动力学的影响已有充分记录，但对周围血流动力学事件却知之甚少。因此，本研究的目的是检查在70度头高位倾斜期间双腿交叉并伴有肌肉紧张对周围血流动力学的影响。对健康受试者（n = 13）先在仰卧位监测10分钟，然后在70度头高位倾斜位监测10分钟，最后在70度头高位倾斜位进行2分钟的双腿交叉并伴有肌肉紧张。通过Portapres连续测量平均动脉压（MAP）、心率、每搏输出量、心输出量和总外周阻力。使用多普勒超声测量腿部血流。腿部血管传导率计算为腿部血流/MAP。与70度头高位倾斜基线相比，在身体应对策略期间观察到MAP显著增加（13 mmHg）、每搏输出量显著增加（27%）和心输出量显著增加（18%）；心率显著降低（-5次/分钟），总外周阻力无变化。与70度头高位倾斜基线相比，在身体应对策略期间观察到腿部血流显著增加（325 ml/min）和腿部血管传导率显著增加（2.9任意单位）。总之，本研究表明，双腿交叉并伴有肌肉紧张的身体应对策略明显增强了腿部血流，同时提高了MAP。
