Strnad V, Grebmeier J, Riepl M, Kirschner M, Sauer R
Klinik und Poliklinik für Strahlentherapie, Universität Erlangen-Nürnberg.
Strahlenther Onkol. 1994 Oct;170(10):571-80.
Chronic hypoxia in tumors is generally accepted to be one of the most important factors concerning sensibility to irradiation. The principle of hypoxyradiotherapy is to achieve a limited (maximal 30 min) radioresistance of the healthy (actually euoxic) tissue by acute aerogen hypoxia, without protecting effects in the average chronic hypoxic tissue of the tumor. This study investigates changes in selected physiological parameters in vivo during acute aerogen hypoxia.
In 31 persons (group A) we documented changes in blood-gas-analysis, ECG-parameters, blood pressure and pulse during acute hypoxia lasting 5 minutes. During 30 minutes of acute hypoxia we determined in another 10 persons (group B) the relations between different phosphoryl-metabolites by means of 31-phosphorus magnetic resonance spectroscopy (31P-MRS). The 31P-MRS of the Musculus triceps surae was performed on our 1.5 T imaging system (Magnetom, Siemens) using a 8 cm diameter surface coil. To achieve the hypoxic condition in the persons tested, a gas-mixture with 8.2% O2 was used.
In group A the acute hypoxia led to significant changes in O2-pressure, the blood O2-saturation and pulse frequency. The pO2-values drop in the 5th minute to about 50% of the initial value. Concerning group B the relations of the phosphoryl metabolites show no significant changes during acute hypoxia.
The results show an excellent tolerability of breathing of the hypoxic gas-mixture, and confirm that this mixture containing 8.2% of O2 ensures a decrease in the pO2-levels of more than 50%. This is necessary to achieve a dose modifying factor (DMF) of at least 1.15 to 1.2. The changes in relations of phosphoryl metabolites seem to reflect the ability of healthy tissue to adapt to hypoxic conditions starting after 10 minutes and leading to the loss of the radioprotective effect after 30 minutes.
肿瘤中的慢性缺氧通常被认为是影响辐射敏感性的最重要因素之一。低氧放疗的原理是通过急性气体性缺氧使健康（实际上为常氧）组织产生有限（最长30分钟）的放射抗性，而对肿瘤的平均慢性缺氧组织没有保护作用。本研究调查急性气体性缺氧期间体内选定生理参数的变化。
在31人（A组）中，我们记录了持续5分钟的急性缺氧期间血气分析、心电图参数、血压和脉搏的变化。在另外10人（B组）中，在30分钟的急性缺氧期间，我们通过31磷磁共振波谱（31P-MRS）测定了不同磷酸化代谢物之间的关系。使用直径8厘米的表面线圈在我们的1.5T成像系统（西门子Magnetom）上对腓肠肌进行31P-MRS检查。为了在受试人员中实现缺氧状态，使用了含8.2%氧气的混合气体。
在A组中，急性缺氧导致氧分压、血氧饱和度和脉搏频率发生显著变化。第5分钟时，pO2值降至初始值的约50%。关于B组，急性缺氧期间磷酸化代谢物的关系没有显著变化。
结果表明低氧混合气体呼吸具有良好的耐受性，并证实这种含8.2%氧气的混合气体可确保pO2水平降低超过50%。这对于实现至少1.15至1.2的剂量修正因子（DMF）是必要的。磷酸化代谢物关系的变化似乎反映了健康组织在10分钟后开始适应缺氧条件并在30分钟后导致放射保护作用丧失的能力。
