虚血脳における安静時酸素摂取率とPaCO2血管反応性の検討

OXYGEN EXTRACTION FRACTION AND CEREBROVASCULAR REACTIVITY TO PaCO2 CHANGE IN ISCHEMIC BRAIN MEASURED BY POSITRON EMISSION TOMOGRAPHY

　抄録　¹⁵0標識ガス定常吸入法とH₂¹⁵O瞬時静注法を用いたポジトロンエミッショントモグラフィ（PET）により，安静時酸素摂取率（OEF）とCO₂吸入または過呼吸負荷時の血管反応性（VRCO₂）を測定した。虚血範囲が広い症例ほど，局所間のOEFとVRCO₂間に相関を示す頻度が高くhypercapniaに対して負相関，hypocapniaに対して正相関が見られた。また，灌流圧低下に伴い抵抗血管が最大拡張に至った状態でのOEF値は0.54であると求められた。

Interrelations between oxygen extraction (OEF) and cerebrovascular reactivitity to PaCO₂ change (VRCO₂) in ischemic brain were measured by the ¹⁵O gases steady state method and the H₂¹⁵O au-toradiographic method using a positron emission tomography. OEF at rest and VRCO₂ for hyper-capnia and hypocapnia were assessed successively in five cross sections of 10 mm image resolution. With each study correlation coefficients between OEF and VRCO₂ were calculated using 30 to 40 regions of interest. In hypercapnic measurements those which had a larger ischemic region result-ed in a higher incident of a negative correlation. Fifteen of 19 studies (79%) showed the negative correlation. From the regression lines which show-ed significant correlation a mean OEF at VRCO₂=0 was 0.54±0.09, which might indicate the point at the maximal dilatation of the resistance vessels. On the other hand, in hypocapnic studies only five of 18 (28%) showed apositive correlation, and the other measurements showed diffusely negative VRCO₂ over the whole regions in the brain.