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目的为飞行员脑功能鉴定及防护提供试验方法和依据。方法采用经颅多普勒超声连续观察45名飞行员(平均年龄27.5±2.6岁)在完成5 h 连续心算和连续操作任务期间的脑平均血流速度(Vm),同步分析大脑前动脉(ACA)、中动脉(MCA)、后动脉(PCA)的 Vm、神经行为能力指数(NAI),并对脑疲劳诱发的嗜睡倾向进行斯坦福嗜睡量表(SSS)评定。结果在完成连续心算任务的第2 h,大脑 ACA 的 Vm 增快,第4 h 以后减慢,MCA、PCA 的 Vm 无显著变化。完成连续操作任务的第4 h 以后,PCA 的 Vm 先于 MCA 的 Vm 减慢,ACA、MCA 和 PCA 的 Vm 直至第5 h才明显减慢。反映连续操作能力的 NAI 指数在第2 h 上升,第4 h 以后下降。反映心算能力下降的错误反应率和反映脑功能状态的 SSS 评分在第4 h 以后显著上升,表明脑功能出现显著抑制。结论不同认知活动对大脑 Vm 的影响存在差异。5 h 连续心算任务没有诱发 Vm 的显著变化,但5 h连续操作任务诱发 MCA 的 Vm 大幅度降低,有可能是晕厥前症状或立位耐力降低的诱发因素之一。
Objective To provide experimental methods and basis for pilots’ brain function identification and protection. Methods The mean cerebral blood flow velocity (Vm) of 45 pilots (mean age 27.5 ± 2.6 years) during the 5-hour continuous mental arithmetic and continuous operation tasks was continuously observed by transcranial Doppler ultrasound. The anterior cerebral artery (ACA) Vm and NAI of the MCA and PCA were measured. The Stanford Sleepiness Scale (SSS) was used to evaluate the sleep-deprivation tendency induced by cerebral fatigue. Results The Vm of cerebral ACA increased at the 2nd hour after completing the continuous mental arithmetic task, and slowed down after the 4th hour, while the Vm of MCA and PCA did not change significantly. After the first 4 h of continuous operation, the Vm of PCA slowed down before the Vm of MCA. The Vm of ACA, MCA and PCA did not slow down significantly until 5 h. The NAI index, which reflects the continuous operation ability, increased at the 2h and decreased after 4h. The false response rate, which reflects the decline in mental arithmetic ability, and the SSS score, which reflects the state of brain function, increased significantly after 4 h, indicating a significant inhibition of brain function. Conclusion Different cognitive activities have different effects on Vm of the brain. 5-h continuous cardiac arithmetic did not induce significant changes in Vm, but 5-h continuous operation task induced a significant decrease in Vm of MCA, which may be one of the predisposing factors for the pre-syncope symptoms or standing tolerance.