急性正加速度暴露后飞行员脑血流动态调节功能的评估

Assessment of dynamic cerebral autoregulation in pilots after acute positive acceleration exposure

目的应用经颅多普勒超声联合逐波血压监测探讨飞行员急性正加速度(+Gz)暴露后脑血流动态调节能力的变化。方法前瞻性纳入2022年6-10月于空军军医大学空军特色医学中心接受离心机+8Gz高载荷耐力测试的男性飞行员26例。于试验前静息状态和离心后5 min内分别监测血压、心率,并使用经颅多普勒超声联合无创连续血压监测仪监测双侧大脑中动脉血流速度和无创逐波血压,应用传递函数分析计算得出双侧0.02~0.50 Hz各频段内的脑血流动态调节参数,并计算相位差、增益和一致性。比较静息状态与离心后上述参数的差异。结果与静息状态相比,26例飞行员在+8Gz急性高载荷暴露后收缩压、舒张压、心率显著升高(均P<0.001);在超低频段(0.02~0.07 Hz)相位差显著升高,增益显著降低(均P<0.05);而在低频段(0.07~0.20 Hz)和高频段(0.20~0.50 Hz)静息状态与离心后相位差和增益差异无统计学意义(均P>0.05)。结论经颅多普勒超声联合逐波血压监测可用于检测高载荷急性+Gz暴露后脑血流动态调节变化。传递函数分析超低频段参数适用于此类评估。

Objective To explore the changes of dynamic cerebral autoregulation ability in pilots exposed to acute positive acceleration(+Gz)by transcranial Doppler combined with beat-to-beat blood pressure.Methods A total of 26 pilots enrolled in the+8Gz manned centrifuge trial at the Air Force Medical Center,Air Force Medical University from June to October 2022 were prospectively included.Blood pressure and heart rate were monitored in the resting state before the trial and within 5 min after centrifugation.Transcranial Doppler combined with noninvasive continuous beat-to-beat blood pressure monitor were used to detect bilateral middle cerebral artery blood flow velocity and beat-to-beat pulse pressure respectively.The transfer function analysis was applied to derive the parameters of cerebral blood flow autoregulation in each frequency band from 0.02 to 0.50 Hz,and the phase,gain and coherence were calculated.The above parameters were compared between resting state and after acute+8Gz positive acceleration exposure.Results Compared with the resting state,in all of the 26 pilots after acute+8Gz positive acceleration exposure,the systolic and diastolic blood pressure and heart rate increased significantly(P<0.001),the phase significantly increased and the gain significantly decreased in the ultra-low frequency band(0.02-0.07 Hz)(P<0.05);whereas there were no statistical differences of gain and phase in the low frequency band(0.07-0.20 Hz)and the high frequency band(0.20-0.50 Hz)(all P>0.05).Conclusions Transcranial Doppler combined with beat-to-beat pulse pressure can be used for the assessment of changes in immediate dynamic cerebral autoregulation after acute+Gz exposure,and transfer function analysis of ultra-low frequency band parameters is suitable for this type of evaluation.