Background

Supplemental oxygen therapy is commonly required for respiratory failure requiring mechanical ventilation in the ICU. However, hyperoxaemia may be injurious and may increase mortality. We evaluated the relationship amongst the degree of hyperoxaemia and changes in fraction of inspired oxygen (Fio₂) in response to hyperoxaemia, as well as associations with mortality in mechanically ventilated ICU patients.

Methods

We retrospectively identified all invasively mechanically ventilated patients admitted to five ICUs, and retrieved all oxygen tension (Pao₂) and Fio₂ data. We assessed the time between arterial blood gas (ABG) samples, proportions of patients with hyperoxaemia, and changes in Fio₂ when hyperoxaemia was present. The primary outcome was the association between Pao₂ (assessed by mechanically ventilated exposure-time-divided area under the curve [AUC]) and mortality (in-ICU and post-ICU discharge) using a multistate illness–death model with transition intensities estimated by Cox proportional hazards models.

Results

We assessed 177 769 ABG analyses obtained from 4998 patients between January 2012 and June 2016. The median time between ABGs was 3 h (inter-quartile range: 2–4 h); the median Pao₂ was 11.3 kPa (9.8–13.6 kPa), and Fio₂ was 0.40 (0.35–0.50). Hyperoxaemia (Pao₂ >13.7 kPa) was present in 23.9% of the ABGs, and hyperoxaemia seemed to be disregarded when Fio₂ was <0.40, as >50% of these Fio₂ values were not subsequently reduced. AUC Pao₂ >16.0 kPa was associated with increased ICU mortality (adjusted hazard ratio: 1.75; 95% confidence interval: 1.28–2.40).

Conclusions

In mechanically ventilated ICU patients, hyperoxaemia was common. Although oxygen supplementation was often reduced when hyperoxaemia was observed, several patients remained hyperoxaemic. Hyperoxaemia was associated with increased ICU mortality in these patients.

中文翻译：

---

机械通气ICU患者的动脉血氧张力和死亡率：一项回顾性，多中心，观察性队列研究。

背景

对于需要在ICU中进行机械通气的呼吸衰竭，通常需要补充氧气治疗。但是，高氧血症可能有害，并可能增加死亡率。我们评估了高氧血症程度与对高氧血症的反应中吸入氧分数（F io ₂）的变化之间的关系，以及机械通气ICU患者的死亡率。

方法

我们回顾性地确定了接受了5个ICU的所有有创机械通气患者，并检索了所有的氧气张力（P a o ₂）和F io ₂数据。我们评估了动脉血气（ABG）样本之间的时间，高氧血症患者的比例以及高氧血症存在时F io _2的变化。主要结局是使用多状态疾病-死亡模型（包括过渡期），P a o ₂（通过曲线[AUC]下的机械通气暴露时间划分面积评估）与死亡率（ICU内和ICU后出院）之间的关联。强度由考克斯比例风险模型估算。

结果

我们评估了2012年1月至2016年6月从4998例患者中获得的177 769次ABG分析。两次ABG之间的中位时间为3小时（四分位间距：2-4小时）；中位数P a o ₂为11.3 kPa（9.8-13.6 kPa），F io ₂为0.40（0.35-0.50）。在23.9％的ABG中存在高氧血症（P a o ₂ > 13.7 kPa），并且当F io ₂ <0.40时高氧血症似乎被忽略，因为这些F io ₂值中的> 50％随后没有降低。AUC P a o ₂ > 16.0 kPa与ICU死亡率增加相关（调整后的危险比：1.75； 95％置信区间：1.28-2.40）。

结论

在机械通气的ICU患者中，高氧血症很常见。尽管在观察到高氧血症时经常减少氧气的补充，但仍有几例患者发生高氧血症。高氧血症与这些患者的ICU死亡率增加有关。