下体负压对21天头低位卧床模拟失重心功能及脑血流量的影响

Effect of lower body negative pressure on cardiac function and cerebral blood flow during 21 d head-down tilt bed rest

目的 观察下体负压 (lower body negative pressure,L BNP)锻炼对 2 1d头低位卧床模拟失重心功能及脑血流的影响 ,探讨 L BNP提高立位耐力的机制 .方法 健康男性志愿者 12名 ,随机分为对照组和 L BNP组 ,每组 6人 ,进行头低位倾斜卧床 .对照组在卧床期间不做任何处理 ,L BNP组在卧床后 1wk和最后 1wk,每天进行 1h,- 4.0 k Pa的下体负压锻炼 .利用 KYD- 30 0心功能检查仪测量卧床前坐位、卧位及卧床 1,3,7,10 ,14及 2 1d的心脏泵血及收缩功能 .利用KYENG- 导纳式双侧脑血流自动检测仪测量卧床前坐位及卧位、卧床 3,10及 2 1d的脑血流量 .结果 与卧床前 (卧位 )相比 ,对照组心输出量 (CO)及每搏输出量 (SV)在 3d,10d,每搏功指数 (SWI)在 1,3,7,10 ,14d,左室射血时间在 7d,右侧大脑流入速度在 3,10 ,2 1d显著降低 (P<0 .0 5 ) .L B-NP组右侧脑血流主峰高度和流入速度在 3,10 ,2 1d显著降低 (P<0 .0 5 ) .两组间比较 ,L BNP组左室射血时间 (L VET)在卧床 3,7,14d,主峰高度在 3,2 1d较对照组显著升高 (P<0 .0 5 ) .结论 2 1d头低位卧床可引起心脏泵血及收缩功能降低 ,脑血管阻力增加 ,脑血流量减少 ;在卧床 1wk及最后 1wk进行下体负压 (- 4.0 k Pa,1h· d- 1 )锻炼 ,可部分对抗头低位卧床引起的心脏功?

AIM To investigate the effect of lower body negative pressure (LBNP) on cardiac function and cerebral blood flow (CBF) during 21 d head down tilt (HDT) bed rest in humans. METHODS Twelve healthy male subjects were randomly divided into control and LBNP groups, with 6 in each group. They were exposed to -6° HDT for 21 d. LBNP group received -4.0 kPa LBNP training for 1 h·d -1 in the first and the last week of HDT. Cardiac function were measured before HDT and on d 1, 3, 10, 14 and 21 of HDT. CBF and cerebral vascular resistance were measured by rheoencephalogram before HDT and on d 3, 10 and 21 of HDT. RESULTS In control group, the cardiac output (CO) and stroke volume (SV) were decreased significantly ( P < 0.05) on d 3, 7, as compared with pre HDT (Lain). A significant decrease in stroke work index (SWI) on d 1, 3, 7, 10, 14, left ventricular ejection time (LVET) on d 7 and inrush velocity of right brain on d 3, 10, 21 were observed in control group. The ΔGy wave crest height and inrush velocity of right brain were decreased significantly ( P <0.05) on d 3, 10, 21 in LBNP group. Between the two groups, LVET and ΔGy wave crest height of the LBNP group were lower on d 3, 7, 14 or d 3, 21 than those in control group ( P <0.05). CONCLUSION LBNP training for 1 h·d -1 in the first and last week of HDT may prevent the reduction of cardiac function and cerebral blood flow induced by 21 d HDT bed rest.