Department of Physiology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
Crit Care. 2011;15(3):305. doi: 10.1186/cc10229. Epub 2011 Jun 30.
Supplementary oxygen is routinely administered to patients, even those with adequate oxygen saturations, in the belief that it increases oxygen delivery. But oxygen delivery depends not just on arterial oxygen content but also on perfusion. It is not widely recognized that hyperoxia causes vasoconstriction, either directly or through hyperoxia-induced hypocapnia. If perfusion decreases more than arterial oxygen content increases during hyperoxia, then regional oxygen delivery decreases. This mechanism, and not (just) that attributed to reactive oxygen species, is likely to contribute to the worse outcomes in patients given high-concentration oxygen in the treatment of myocardial infarction, in postcardiac arrest, in stroke, in neonatal resuscitation and in the critically ill. The mechanism may also contribute to the increased risk of mortality in acute exacerbations of chronic obstructive pulmonary disease, in which worsening respiratory failure plays a predominant role. To avoid these effects, hyperoxia and hypocapnia should be avoided, with oxygen administered only to patients with evidence of hypoxemia and at a dose that relieves hypoxemia without causing hyperoxia.
常规为患者补充氧气，即使患者的氧饱和度充足，因为人们认为这可以增加氧输送。但氧输送不仅取决于动脉血氧含量，还取决于灌注。人们还没有广泛认识到，高氧会直接或通过高氧诱导的低碳酸血症引起血管收缩。如果在高氧期间，灌注减少的程度超过动脉血氧含量增加的程度，那么局部氧输送就会减少。这种机制（而不仅仅是归因于活性氧的机制）可能导致接受高浓度氧气治疗心肌梗死、心脏骤停后、中风、新生儿复苏和重症患者的患者预后更差。该机制也可能导致慢性阻塞性肺疾病急性加重患者的死亡率增加，在这种情况下，呼吸衰竭恶化起主要作用。为了避免这些影响，应避免高氧和低碳酸血症，仅对有低氧血症证据的患者给予氧气，并给予缓解低氧血症而不引起高氧血症的剂量。
