下体负压下V_(MCA)ERP的改变及不同刺激模式的比较

Changes of cerebral blood flow velocity and event related potential and comparison of different stimulus paradigms under lower body negative pressure

目的:探讨坐位下体负压下人体大脑中动脉血流速度、人体事件相关电位的改变及不同刺激模式的比较.方法:15名健康青年男性在坐位下体负压-4.00,-6.67kPa条件下,分别测试负压前、下体负压暴露0.5,1,2,3,4,5min和卸压后1,3,5min的大脑中动脉血流速度,P300波幅,P300潜时.结果:在-4.00kPa下体负压作用4,5min时,脑血流速度减慢(P<0.05);P300波幅,P300潜时,反应时,跟踪误差与负压前对照无明显差别;在-6.67kPa下体负压作用2,3min时,脑血流速度减慢(P<0.05),在4,5min时显著减慢(P<0.01),卸压后1min尚未恢复(P<0.05),随后恢复至对照水平;P300波幅显著降低,P300潜时显著延长;反应时延长,跟踪误差增大.Sternberg模式MEST=1诱发的事件相关电位对负压所致的脑缺血缺氧敏感.结论:坐位下体负压造成血液在下肢淤积,大脑中动脉血液速度减慢,引起大脑血供减少,为空中晕厥和立位耐力不良的医学鉴定提供了人体实验依据.

AIM： To investigate the changes of cerebral blood supply and event related potential and ergonomics indexes in human subjects under lower body negative pressure in an upright seated position （ U-LBNP ）. METHODS ： Fifteen young men were selected as subjects. Every subject was exposed to LBNP of - 4.00 kPa and - 6.67 kPa, respectively. Middle cerebral blood flow velocity （VMCA） was measured at 0.5, 1, 2, 3, 4, 5 rain during U-LBNP and 1, 3, 5 min after - 4.00 kPa and - 6.67 kPa U-LBNP respectively in an upright seated position. Each measurement lasted 5 min and the results would be compared with the ones measured at the control level 5 min before the experiments. P300 amplitude and latency, reaction time （RT）, tracking error （ TrE ） were measured during LBNP of - 4.00 kPa and -6.67 kPa in an upright seated position. RESULTS： Under -4.00 kPa LBNP, VMCA slowed down at 4, 5 min during LBNP （ P 〈 0.05 ）, P300 amplitude, latency, RT and TrE had no significant differences between pre- and post-LBNP. Under - 6.67 kPa LBNP, VMCA became slow at 2, 3 min during LBNP （P 〈0.05 ） , and obviously at 4 and 5 min during LBNP （ P 〈 0.01 ）. At 1 min after release of LBNP, VMCA did not recover （ P 〈 0.05 ） , then gradually recovered to the control level; P300 amplitude decreased （P〈0.01） ;P300 latency and RT were delayed （P 〈0.01, P 〈 0.05 ） ; TrE increased （ P 〈 0.05 ）. Event related potential was sensitive to brain anoxemia and anoxia under U-LBNP working in the Sternberg model MEST = 1. CONCLUSION： LBNP can cause blood pooling in lower body so that VMCA and brain blood volume decrease, thus leading to loss of consciousness. The experiment provides experimental data for diagnosis of flight syncope and orthostatic intolerance.