GENDER & AGE EFFECTS ON ORTHOSTATIC TOLERANCE AFTER SHORT TERM BED REST

先前的研究表明，卧床休息或太空飞行后，血管张力的调节会发生改变。有证据表明，卧床休息导致的心血管降压会导致体位性低血压，而这种情况仅在卧床休息4-6小时后就会发生。本研究的主要目的是确定短期（6小时）头向下倾斜卧床休息对直立期间心血管功能的影响，并研究年龄（20-40岁和40-60岁）和性别对这些观察结果的影响。我们正在监测血压、心电图、多普勒（用于测量主动脉卒中容量、脑血流量和股动脉血流量）、小腿围、呼吸频率。二氧化碳含量与腓神经肌肉交感神经组（微神经造影）。受试者首先头部向上倾斜70度20分钟，然后头部向下倾斜6度6小时，最后进行第二次头部向上倾斜测试。

Previous studies have shown that regulation of blood vessel tone is altered by bed rest or following space flight. Evidence suggests that cardiovascular deconditioning with bed rest results in orthostatic hypotension and that this can develop after only 4-6 hours of bed rest. The key objectives of this study are to determine the effect of short term (6 hour) head down tilt bed rest on cardiovascular function during orthostasis and to study the effect of age (20-40 and 40-60 years) and gender on these observations. We are monitoring blood pressure, ECG, Doppler (for measurement of aortic stroke volume, cerebral blood flow and femoral artery blood flow), calf circumference, respiratory rate. CO2 content and peroneal nerve muscle sympathetic tome (microneurography). The subject will be initially tilted 70 degrees head-up for 20 minutes followed by a 6 degree head down tilt for 6 hours and finally a second head-up tilt test.