Changes of cerebral blood flow velocity and event related potential and comparison of different stimulus paradigms under lower body negative pressure

    HAN Wenª²Qiang1, HU Wenª²Dong1£¬WEN Zhiª²Hong1£¬MA Ruiª²Shan2, TIAN Ruiª²Feng3

    1Department of Aerospace Medical Equipment£¬2Department of Aerospace Physiology, School of Aerospace Medicine, 3District Retired Cadres Entertainment Center, Fourth Military Medical University, Xi¬ðan 710033, China

    ¡¾Abstract¡¿ AIM£ºTo investigate the changes of cerebral blood supply and event related potential and ergonomics indexes in human subjects under lower body negative pressure in an upright seated position (Uª²LBNP). METHODS: Fifteen young men were selected as subjects. Every subject was exposed to LBNP of -4.00 kPa and -6.67 kPa£¬ respectively. Middle cerebral blood flow velocity (VMCA) was measured at 0.5, 1, 2, 3, 4£¬ 5 min during Uª²LBNP and 1, 3, 5 min after -4.00 kPa and -6.67 kPa Uª²LBNP respectively in an upright seated position. Each measurement lasted 5 min and the results would be compared with the ones measured at the control level 5 min before the experiments. P300 amplitude and latency, reaction time (RT), tracking error (TrE) were measured during LBNP of -4.00 kPa and -6.67 kPa in an upright seated position. RESULTS: Under -4.00 kPa LBNP, VMCA slowed down at 4, 5 min during LBNP (P<0.05), P300 amplitude, latency, RT and TrE had no significant differences between preª² and postª²LBNP. Under -6.67 kPa LBNP, VMCA became slow at 2, 3 min during LBNP (P<0.05), and obviously at 4 and 5 min during LBNP (P<0.01). At 1 min after release of LBNP, VMCA did not recover(P<0.05), then gradually recovered to the control level£»P300 amplitude decreased (P<0.01)£»P300 latency and RT were delayed (P<0.01, P<0.05)£»TrE increased (P<0.05). Event related potential was sensitive to brain anoxemia and anoxia under Uª²LBNP working in the Sternberg model MEST=1. CONCLUSION: LBNP can cause blood pooling in lower body so that VMCA and brain blood volume decrease, thus leading to loss of consciousness. The experiment provides experimental data for diagnosis of flight syncope and orthostatic intolerance. ......