脑血管对二氧化碳反应中脑血流变化影响因素的临界关闭压研究

目的探讨脑血管对二氧化碳(CO2)反应中脑血流变化的影响因素及其程度。方法同步监测65例健康志愿者正常呼吸、屏气和过度通气时的脑血流、动脉血压、呼出气体CO2分压,并计算临界关闭压(CCP)、脑循环阻力(R)和脑循环灌注压(CPP)。结果屏气时平均动脉压(MABP)和CPP升高,CCP和R降低(P<0.05);过度通气则恰好相反(均P<0.05)。平均血流速度(Vm)的变化受MABP、CCP和R 3种因素的影响,其影响程度在屏气和过度通气中各为29.1%、26.6%、44.3%和42.8%、33.4%、23.8%。结论脑血管对CO2反应的脑血流变化受动脉血压、CCP和R 3种因素的影响,其中动脉血压和CCP对脑灌注压的调控非常重要。

A Study on critical closing pressure in factors influencing changes of cerebral blood flow at cerebrovascular reaction to CO2

Objective To investigate the factors influencing cerebral blood flow at cerebrovascular reaction to CO_2.Methods Cerebral blood flow of middle cerebral artery,radial blood pressure and endtidal CO_2(ETCO_2) were simultaneously monitored in 65 healthy volunteers during normocapnia,hyper-and hypocapnia respectively.Critical closing pressure(CCP),resistance of cerebral circulation(R) and cerebral perfusion pressure(CPP) were determined.Results Mean arterial blood pressure(MABP) and CPP increased,while CCP and R decreased at hypercapnia(P<0.05).At hypocapnia,MABP and CPP decreased,while CCP and R increased(P<0.05).The shift of mean blood flow velocity(Vm) was affected by MABP,CCP and R.Their extents of influence were(29.1%),26.6% and 44.3% respectively at hypercapnia and 42.8%,33.4% and 23.8% at hypocapnia.Conclusions The shift of cerebral blood flow is affected by arterial blood pressure,CCP and R at cerebrovascular reaction to CO_2,and the regulation of CPP by arterial blood pressure and CCP is important.