Haruna Y, Suzuki Y, Kawakubo K, Gunji A
Department of Health Administration, Faculty of Medicine, University of Tokyo, Japan.
Acta Physiol Scand Suppl. 1994;616:71-81.
To determine the critical factor that induces tachycardia during orthostasis after bed rest, we tested some autonomous nervous functions and the reaction to lower body negative pressure before and after 20 days horizontal bed rest. Subjects were 5 young healthy males and one female. Carotid vagal baroreflex sensitivity was evaluated by cardiac response to a gradual increase in carotid distending pressure of 150 mmHg within 10 s by neck suction after neck positive pressure. Combined effects of cardiopulmonary and aortic baroreflexes were assessed by the cardiovascular responses during Valsalva manoeuvre. Sympathetic reactivity was evaluated by a cold pressor test. The carotid vagal baroreflex tended to be diminished after bed rest in supine rest, but unchanged in seated position. Cardiac responses to Valsalva manoeuvre did not change after bed rest, although blood pressures decreased more during the manoeuvre after bed rest. Cold pressor response did not change after bed rest. Heart rate response during lower body negative pressure was increased after bed rest. In conclusion, combining our results from several autonomous nervous functions suggested that the exaggerated orthostatic tachycardia after bed rest could not be explained by the changes in sensitivity of carotid, aortic, and cardiopulmonary reflexes and sympathetic reactivity to cold stress.
为了确定卧床休息后立位时诱发心动过速的关键因素，我们在20天的水平卧床休息前后测试了一些自主神经功能以及对下体负压的反应。受试者为5名年轻健康男性和1名女性。通过颈部正压后颈部抽吸在10秒内使颈动脉扩张压逐渐升高150 mmHg时的心脏反应来评估颈动脉迷走压力反射敏感性。通过瓦尔萨尔瓦动作期间的心血管反应评估心肺和主动脉压力反射的联合作用。通过冷加压试验评估交感神经反应性。仰卧休息时卧床休息后颈动脉迷走压力反射趋于减弱，但坐位时不变。卧床休息后，尽管瓦尔萨尔瓦动作期间血压下降更多，但对该动作的心脏反应并未改变。卧床休息后冷加压反应未改变。卧床休息后下体负压期间的心率反应增加。总之，综合我们从几种自主神经功能获得的结果表明，卧床休息后出现的过度直立性心动过速不能用颈动脉、主动脉和心肺反射敏感性以及交感神经对冷应激的反应性变化来解释。
