目的探讨坐位下体负压对人体大脑中动脉血流速度、心率和血氧饱和度的影响。方法 15名健康青年男性在坐位下体负压 - 4.0 0kPa、 - 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、心率和血氧饱和度。结果在 - 4.0kPa下体负压作用 4、5min时 ,脑血流速度减慢 (P <0 .0 5 ) ;负压作用 3、4、5min时心率增快 (P <0 .0 5 ) ;血氧饱和度无明显改变。在 - 6.67kPa下体负压作用 2、3min时 ,脑血流速度减慢 (P <0 .0 5 ) ,在 4min和 5min时显著减慢 (P <0 .0 1) ,卸压后 1min尚未恢复 (P <0 .0 5 ) ,随后恢复至对照水平 ;负压作用后各时间点心率均显著增快 (P <0 .0 1) ;血氧饱和度在负压暴露 5min时显著下降 (P <0 .0 5 )。结论坐位下体负压造成血液在下肢淤积 ,大脑中动脉血流速度减慢 ,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 Objective To investigate the effect of lower body negative pressure on blood flow velocity, heart rate and oxygen saturation of human middle cerebral artery. Methods Fifteen healthy young men were exposed to negative pressure in the lower body at 4.0 0 kPa and - 6.67 kPa for 0, 5, 1, 2, 3, 4 and 5 minutes before and after exposure to the negative pressure. 3,5 min middle cerebral artery blood flow velocity, heart rate and oxygen saturation. Results At 4 and 5 min of -4.0 kPa, the cerebral blood flow velocity was slowed down (P <0.05), and the heart rate was increased at 3, 4 and 5 min of negative pressure (P <0.05). No significant change in oxygen saturation. The cerebral blood flow velocity slowed down (P <0. 05) at -2, 6 min under negative pressure of 6.67 kPa, significantly slowed down at 4 and 5 min (P <0. (P <0.05), then recovered to the control level. Heart rate was significantly increased at each time point after negative pressure (P <0.01); oxygen saturation decreased significantly at 5 min after negative pressure exposure P <0. 05). Conclusions The negative pressure in sitting position leads to the accumulation of blood in the lower extremity. The blood flow velocity in the middle cerebral artery slows down, 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