Before the ICU: does emergency room hyperoxia affect outcome?

Excerpt

There is now ample evidence that hyperox(em)ia—that is, increased inspired oxygen concentrations (F_IO₂) and the subsequent rise in arterial oxygen tensions (PaO₂)—coincides with aggravated mortality [1]. Most of the data originate from retrospective analyses, but a single-center trial showed that “conservative” PaO₂ (70–100 mmHg) halved mortality when compared to “conventional” targets (≤ 150 mmHg) [2]. The available studies mostly refer to data from intensive care unit (ICU) patients, but despite its frequent use in daily practice, the impact of hyperox(em)ia remains much less clear for patients in the emergency department (ED) and/or even prior to hospital admission. Hyperox(em)ia is often present after initiation of mechanical ventilation, most likely for fear of hypoxemia when blood gas analyses are not readily available. However, supplemental O₂ can also yield hyperoxemic PaO₂ levels without mechanical ventilation: in the aforementioned clinical trial demonstrating the beneficial effect of targeting “conservative” PaO ₂ levels in the ICU, upon admission into the study only 2/3 of the patients investigated were mechanically ventilated [2]. However, the duration of mechanical ventilation per se is directly related to adverse outcome in ED patients. …