坐位下体负压对人体大脑中动脉血流速度及血氧饱和度的影响

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0.5,1,2,3,4,5 min和卸压后1,3,5 min的VMCA和SaO2.结果在-4.00kPa U-LBNP作用4,5min时,VMCA减慢(P＜0.05);SaO2无明显改变.在-6.67 kPa U-LBNP作用2,3 min时,VMCA减慢(P＜0.05),在4min和5min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;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.

Effect of lower body negative pressure in upright sitting position on the flow velocity of middle cerebral artery and the oxygen saturation of hemoglobin in human body

BACKGROUND: The prevention and monitor of unconsciousness induced by high over load is one of the important topics in present medical research of aeronautics and aerospace.OBJECTIVE: To discuss the effect of lower body negative pressure in upright sitting position(U-LBNP) on the flow velocity of middle cerebral artery (VMCA) and the oxygen saturation of blood(SaO2) in human body.DESIGN: A non-randomized auto-control experimental study.SETTING AND SUBJECTS: The brain function laboratory of our department was used as the experimental place with fifteen healthy young male experimental subjects chosen from the students of Grade Two in our university. Main intervention: every subject was treated with a lower body negative pressure at both - 4.00 kPa and - 6. 67 kPa, respectively.MAIN OUTCOME MEASURES: Both VMCA and SaO2 were tested respectively before negative pressure treatment and half one, one, two, three, four,five minutes after negative pressure treatment and one, three, five minutes after the unload of negative pressure treatment, with the pressure at both 4.00 and - 6. 67 kPa. Results: after four-minute or five-minute - 4.00 kPa U-LBNP treatment, VMCA was slow down(P ＜ 0.05), while no obvious change was detected in SaO2. VMCA was slow down after two-minute or three-minute -6.67 kPa U-LBNP treatment, and significantly slow down after four-minute or five-minute - 6.67 kPa U-LBNP treatment. The reduction did not improve until one minute after the removement of negative pressure treatment. Subsequently, it recovered back to the control level. SaO2decreased obviously after five-minute - 6.67 kPa U-LBNP treatment.CONCLUSION: U-LBNP leaded to the congestion of lower extremities and the deceleration of VMCA, which subsequently induced the reduction of cerebral blood supply, which offered the human experimental evidence for the medical identification of presyncope and orthostatic intderance.