Hlatky Roman, Valadka Alex B, Gopinath Shankar P, Robertson Claudia S
Baylor College of Medicine, Houston, Texas 77030, USA.
J Neurosurg. 2008 Jan;108(1):53-8. doi: 10.3171/JNS/2008/108/01/0053.
Increasing PaO2 can increase brain tissue PO2 (PbtO2). Nevertheless, the small increase in arterial O2 content induced by hyperoxia does not increase O2 delivery much, especially when cerebral blood flow (CBF) is low, and the effectiveness of hyperoxia as a therapeutic intervention remains controversial. The purpose of this study was to examine the role of regional (r)CBF at the site of the PO2 probe in determining the response of PbtO2 to induced hyperoxia.
The authors measured PaO2 and PbtO2 at baseline normoxic conditions and after increasing inspired O2 concentration to 100% on 111 occasions in 83 patients with severe traumatic brain injury in whom a stable xenon-enhanced computed tomography measurement of CBF was available. The O2 reactivity was calculated as the change in PbtO2 x 100/change in PaO2.
The O2 reactivity was significantly different (p < 0.001) at the 5 levels of rCBF (<10, 11-15, 16-20, 21-40, and > 40 ml/100 g/min). When rCBF was < 20 ml/100 g/min, the increase in PbtO2 induced by hyperoxia was very small compared with the increase that occurred when rCBF was > 20 ml/100 g/min.
Although the level of CBF is probably only one of the factors that determines the PbtO2 response to hyperoxia, it is apparent from these results that the areas of the brain that would most likely benefit from improved oxygenation are the areas that are the least likely to have increased PbtO2.
提高动脉血氧分压（PaO₂）可增加脑组织氧分压（PbtO₂）。然而，高氧引起的动脉血氧含量小幅增加并不会显著增加氧输送，尤其是在脑血流量（CBF）较低时，高氧作为一种治疗干预措施的有效性仍存在争议。本研究的目的是探讨PO₂探头所在部位的局部脑血流量（rCBF）在决定PbtO₂对诱导性高氧反应中的作用。
作者在83例重度创伤性脑损伤患者中，于基线常氧条件下以及将吸入氧浓度提高到100%后，测量了111次PaO₂和PbtO₂，这些患者可进行稳定的氙增强计算机断层扫描脑血流量测量。氧反应性计算为PbtO₂的变化×100/PaO₂的变化。
在rCBF的5个水平（<10、11 - 15、16 - 20、21 - 40和>40 ml/100 g/min）下，氧反应性有显著差异（p < 0.001）。当rCBF < 20 ml/100 g/min时，与rCBF > 20 ml/100 g/min时相比，高氧诱导的PbtO₂增加非常小。
虽然脑血流量水平可能只是决定PbtO₂对高氧反应的因素之一，但从这些结果可以明显看出，最有可能从改善氧合中获益的脑区是PbtO₂最不可能增加的区域。
