Effects of lower body negative pressure in upright seated position on circulation of human cerebral blood vessel

    HAN Wenª²Qiang, HU Wenª²Dong, MA Jin, MA Ruiª²Shan

    1Aerospace Medicine Engineering Laboratory£¬2Department of Aerospace Physiology, School of Aerospace Medicine, Fourth Military Medical University, Xi¡¯an 710033, China

    ¡¾Abstract¡¿ AIM: To investigate the effects of lower body negative pressure (LBNP) in the upright seated position on the circulation of humancerebral blood vessel. METHODS: Pulsatility index (PI), resistive index (RI), blood flow velocity in middle cerebrum (vMCA) were measured in 15 healthy young men. Subjective symptoms and objective physical signs were measured at 0.5, 1, 2, 3 and 4, 5 min during Uª²LBNP and 1, 3 and 5 min after -4.00 kPa (-30 mmHg) and -6.67 kPa (-50 mmHg) Uª²LBNP, respectively in upright seated position. At five minutes before the experiments, the subjects were tested and the data recorded were used as controls. RESULTS: Under -4.00 kPa Uª²LBNP, vMCA slowed down at 4 and 5 min during Uª²LBNP (P<0.05) and there were no significant changes in PI and RI. Under -6.67 kPa Uª²LBNP, PI and RI increased at 4 and 5 min during Uª²LBNP (P<0.05), vMCA began to slow down at 2 and 3 min during Uª²LBNP (P<0.05), and at 4 and 5 min, vMCA decelerated significantly during Uª²LBNP (P<0.01). At 1 min after the release of Uª²LBNP, vMCA did not recover (P<0.05), after which, it recovered to the control level. Subjective symptoms increased and objective physical signs were obvious. CONCLUSION: LBNP can cause blood pooling in lower body, and as a result, PI and RI increase while vMCA decreases, which may decrease the brain blood volume and weaken the function of cerebral circulation. ......