加速度(+Gz)負荷時における脳内酸素飽和度の変化について

Abstract

The effect of +Gz acceleration on cerebral tissue oxygenation and/or cerebral hemoglobin was studied on 14 volunteer subjects. Subjects were exposed to a 0.1 G/sec onset rate profile until grayout. NIRO-300G (Hamamatsu Photonics K. K., Hamamatsu, Japan) and INVOS 3100 (Somanetics Corp., Troy, MI, USA) were used to measure cerebral oxygen saturation indices; Total Oxygenation Index (TOI) for NIRO-300G, and regional cerebral hemoglobin oxygen saturation (rSHbO2) for INVOS 3100. The concentration changes in the cerebral oxygenated hemoglobin (O2Hb), reduced hemoglobin (HHb) and total hemoglobin (cHb) were also monitored using NIRO-300G. Five and nine subjects were monitored using NIRO-300G and INVOS 3100, respectively. Continuous changes of cerebral oxygen status were clearly demonstrated using these instruments, the changes included reductions in TOI, O2Hb, cHb and rSHbO2 with increased +Gz. The rSHbO2, however, reached the lowest level several seconds after the maximum +Gz. Baseline levels (pre-exposure levels) of TOI ranged from 68.0 to 74.8 percent, and those of rSHbO2 ranged from 70.0 to 87.5 percent. During +Gz acceleration, TOI showed increase with anti-G straining maneuver. In G induced loss of consciousness cases, lowest levels of TOI (60.0 percent) and rSHbO2(25.0 percent) were observed. These results demonstrated that NIRO-300G provides a reliable and sensitive method for the monitoring of cerebral oxygen status during +Gz acceleration.

脳内酸素飽和度および/または脳内ヘモグロビンに対する+Gz加速度負荷の効果を14名の有志被験者について研究した。被験者は0.1G/秒の上昇率でグレイアウトするまで負荷を行った。NIRO-300G(浜松ホトニクス社製)とINVOS-3100(Samanetics社製)を脳内酸素飽和度の測定に使用した;NIRO-300Gでは全酸素指標(TOI)、INVOS-3100では局部脳内ヘモグロビン酸素飽和度(rSHbO2)。脳内酸素化ヘモグロビン(O2Hb)、脱酸素化ヘモグロビン(HHb)および全ヘモグロビン(cHb)もNIRO-300Gを使って測定した。5人の被験者がNIRO-300Gを、9人の被験者がINVOS-3100を使ってそれぞれ測定した。脳内酸素状態の連続的変化はこれらの装置によりはっきりと示され、+Gzの増加に伴いTOI、O2Hb、cHbおよびrSHbO2は減少した。しかしrSHbO2は最大+Gz後数秒で最低水準に達した。TOIの基底水準(負荷前水準)は68.0?74.8%の範囲で、rSHbO2では70.0?87.5%の範囲であった。+Gz加速中にTOIは反G緊張動作を伴った増加を示した。意識の喪失を起こすGのケースではTOI(60%)およびrSHbO2(25.0%)の最低水準を認めた。この結果は、NIRO-300Gが+Gz加速中の脳内酸素状態のモニターに対する信頼性と感度の高い方法を提供することを示した。