摘要
Abstract
BACKGROUND: Lower body negative pressure(LBNP) is one of the effective methods to simulate the influence of gravito-inertial force on human circulation. It can simulate the effects of positive accelerate on human body to a certain extent.OBJECTIVE: To explore the changes of compensation of cardiovascular system with lower body negative pressure in upright seated position (U-LBNP) . To provide physiological parameters for the prevention and monitoring of G-induced loss of conciousness (G-LOC).DESIGN: Randomized self-controlled trial.SETTING and PARTICIPANTS: Setting: the Laboratory of Brain Function in the Department of Aerospace of the Fourth Military Medical University of Chinese PLA. Participants: Fifteen voluntary healthy young men were chosen who were the students of Grade Two in this university.INTERVENTIONS: U-LBNP - 4.00 kPa and - 6. 67 kPa were acted on every participant by using U-LBNP cabin.MAIN OUTCOME MEASURES: Heart rate(HR), blood pressure(BP),subjective symptom, objective physical sign, etc. were measured before LBNP, LBNP under -4.00 kPa and -6.67 kPa in 0.5, 1, 2, 3, 4, 5 minutes and after recovery in 1, 3, 5 minutes.RESULTS: There was no significant difference in diastolic pressure and systolic pressure before and under - 4.00 kPa. U-LBNP under - 4.00 kPa in 3,4 and 5 minutes, HR speeded up(0. 028 1, P ＜ 0.05) and there were no significant changes comparing BP with the control level. Under -6.67 kPa U-LBNP, HR increased significantly at each time point during U-LBNP comparing with that before U-LBNP(0. 000 7, P ＜ 0.01); diastolic pressure increased significantly(0. 019 7, P ＜ 0.05), but there were no significant changes in systolic pressure comparing with that before U-LBNP.CONCLUSION: LBNP can cause blood accumulation in lower body and blood supply decrease in brain. Meanwhile, the cardiovascular compensation enhances, which does not cause the presyncopal symptoms(PSS) in most of participants. With the increase in LBNP and the prolongation of time, the organism shows a decompensational phenomenon, which causes the PSS. The physiological data are provided for the prevention and monitoring of G-LOC.关键词
下身负压/血压/心率/意识丧失分类
医药卫生
