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背景:高过载致空中意识丧失的预防和监控,是当前航空航天医学研究的重要课题之一。目的:探讨坐位下体负压(U-LBNP)对人体大脑中动脉血流速度(VMCA)和血氧饱和度(SaO2)的影响。设计:非随机自身对照实验研究。地点和对象:实验地点在本系脑功能实验室,实验对象为15名健康青年男性,均系本校大学二年级学员。干预:每名被试者均受到-4.00,-6.67kPa下体负压的作用。主要观察指标:分别测试负压前、下体负压暴露于-4.00,-6.67kPa的0.5,1,2,3,4,5min和卸压后1,3,5min的VMCA和SaO2。结果:在-4.00kPaU-LBNP作用4,5min时,VMCA减慢(P<0.05);SaO2无明显改变。在-6.67kPaU-LBNP作用2,3min时,VMCA减慢(P<0.05),在4min和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;SaO2在负压暴露5min时显著下降(P<0.05)。结论:坐位下体负压造成血液在下肢淤积,VMCA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。
Background: Prevention and monitoring of loss of consciousness in high overload conditions is one of the most important topics in current medical research in aerospace. Objective: To investigate the effect of sitting lower body negative pressure (U-LBNP) on blood flow velocity (VMCA) and oxygen saturation (SaO2) in human middle cerebral artery. Design: Non-randomized self-controlled experimental study. Venue and Subject: The experimental site is located in our Department of Brain Functional Laboratory. The experimental subjects are 15 healthy young men, all of whom are sophomores at our university. Intervention: Each participant was subjected to a negative pressure of -4.00 and -6.67 kPa. MAIN OUTCOME MEASURES: VMCA and SaO2 were tested before and after negative pressure exposure to 0.5, 1, 2, 3, 4 and 5 min of -4.00 and -6.67 kPa and 1, 3 and 5 min of depressurization respectively. Results: VMCA slowed down (P <0.05) at -4.00 kPaU-LBNP for 4 and 5 min; SaO2 did not change significantly. After 6 and 6kPaU-LBNP treatment for 2 and 3 minutes, VMCA was slowed down (P <0.05), significantly decreased at 4 and 5 minutes (P <0.01), not recovered at 1 minute after pressure relief SaO2 decreased significantly at 5 min after negative pressure exposure (P <0.05). Conclusion: The negative pressure in the sitting position causes the deposition of blood in the lower extremities and the slowdown of VMCA, which leads to the reduction of cerebral blood supply. It provides human experimental basis for the medical identification of aerial syncope and standing endurance failure.