下体负压下VMCA ERP的改变及不同刺激模式的比较

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,-6.67 kPa条件下,分别测试负压前、下体负压暴露0.5,1,2,3,4,5 min和卸压后1,3,5 min的大脑中动脉血流速度,P300波幅,P300潜时. 结果: 在-4.00 kPa下体负压作用4,5 min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-6.67 kPa下体负压作用2,3 min时,脑血流速度减慢(P＜0.05),在4,5 min时显著减慢(P＜0.01),卸压后1 min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.

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

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 (V_ MCA) was measured at 0.5, 1, 2, 3, 4, 5 min 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. P_ 300 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, V_ MCA slowed down at 4, 5 min during LBNP (P<0.05), P_ 300 amplitude, latency, RT and TrE had no significant differences between pre- and post-LBNP. Under -6.67 kPa LBNP, V_ MCA 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, V_ MCA did not recover(P<0.05), then gradually recovered to the control level;P_ 300 amplitude decreased (P<0.01);P_ 300 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 V_ MCA and brain blood volume decrease, thus leading to loss of consciousness. The experiment provides experimental data for diagnosis of flight syncope and orthostatic intolerance.