动脉二氧化碳分压对健康志愿者脑循环临界关闭压、有效脑灌注压的影响

目的:探讨动脉二氧化碳分压(pCO2)变化对健康志愿者脑循环临界关闭压(pCC)和有效脑灌注压(pCP)的影响.方法:用经颅超声多普勒仪、无创血压监测仪持续记录16位健康志愿者正常呼吸、低碳酸血症和高碳酸血症时的大脑中动脉血流流速和桡动脉血压,用潮气末二氧化碳监测仪持续监测呼出气体的二氧化碳分压.低碳酸血症由过度换气实现,高碳酸血症通过吸入混合气体(体积分数5%CO2、21%O2和74%N2)实现.用傅立叶变换法分别计算3个阶段的pCC和有效pCP.结果:与正常呼吸时比较,低碳酸血症时,大脑中动脉血流流速和平均动脉压下降,pCC升高,有效pCP降低;高碳酸血症时大脑中动脉血流流速和平均动脉压增加,pCC降低,而有效pCP升高,差异均有统计学意义(P＜0.05).结论:动脉 CO2分压可以反映pCC和有效pCP的生理性变化.

Effect of partial pressure of carbon dioxide on critical closing pressure and effective cerebral perfusion pressure in heathy volunteers

Aim:To investigate the effects of partial pressure of carbon dioxide(pCO2)on the critical closing pressure(pCC)and effective cerebral perfusion pressure(pCP)of healthy subjects.Methods:Sixteen healthy people volunteered to be detected continuously the velocities of middle cerebral artery and blood pressure in radial artery,end-tidal CO2 in different situation.Hypocapnia was induced by voluntary hyperventilation,hypercapnia was gained by breathing a gas mixture of 5%CO2,21%O2,74% N2.pCC and effective pCP were calculated by Fourier transform method in three phrases.Results:Compared with those during baseline breath,during hypocapnia,the velocities of middle cerebral artery and mean arterial blood pressure decreased,pCCwas higher and effective pCPwas lower(P<0.05);during hypercapnia,the velocities of middle cerebral artery and mean arterial blood pressure was higher,pCCwas lower and effective pCPwas higher(P<0.05).Conclusion:Physiological changes of pCC and effective pCPcan be expected from variation of CO2 by Fourier transform method.