Conservative oxygen therapy in mechanically ventilated patients following cardiac arrest: A retrospective nested cohort study

Background: In mechanically ventilated (MV) cardiac arrest (CA) survivors admitted to the intensive care unit (ICU) avoidance of hypoxia is considered crucial. However, avoidance of hyperoxia may also be important. A conservative approach to oxygen therapy may reduce exposure to both. Methods: We evaluated the introduction of conservative oxygen therapy (target SpO₂ 88-92% using the lowest FiO₂) during MV for resuscitated CA patients admitted to the ICU. Results: We studied 912 arterial blood gas (ABG) datasets: 448 ABGs from 50 'conventional' and 464 ABGs from 50 'conservative' oxygen therapy patients. Compared to the conventional group, conservative group patients had significantly lower PaO₂ values and FiO₂ exposure (p < 0.001, respectively); more received MV in a spontaneous ventilation mode (18% vs 2%; p = 0.001) and more were exposed to a FiO₂ of 0.21 (19 vs 0 patients, p = 0.001). Additionally, according to mean PaO₂, more conservative group patients were classified as normoxaemic (36 vs 16 patients, p < 0.01) and fewer as hyperoxaemic (14 vs 33 patients, p < 0.01). Finally, ICU length of stay was significantly shorter for conservative group patients (p = 0.04). There was no difference in the proportion of survivors discharged from hospital with good neurological outcome (14/23 vs 12/22 patients, p = 0.67). Conclusions: Our findings provide preliminary support for the feasibility and physiological safety of conservative oxygen therapy in patients admitted to ICU for MV support after cardiac arrest (Trial registration, NCT01684124).