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

A Study on critical closing pressure in factors influencing changes of cerebral blood flow at cerebrovascular reaction to CO_2

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。

Objective To investigate the factors imquencing cerebral blood flow at cerebrovascular reaction to CO2 .Methods Cerebral blood flow of middle cerebral artery, radial blood pressure and end-tidal CO2 （ ET- CO2 ） were simultaneously monitored in 65 healthy volunteers during normocapnia, hyper-and hypocapnia re- spectively. 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 deceased, 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 imquence were 29.1%, 26.6 % and 44.3 % respectively at hypercapnia and 42.8 %, 33.4 % and 23.8 % at hypoapnia. Conclusions The shift of cerebral blood flow is affected by arterial blood pressure, CCP and R at cerebrovascular reaction to CO2, and the regulation of CPP by arterial blood pressure and CCP is important.