Ambient oxygen enrichment during cardiopulmonary resuscitation: an overestimated risk? - Insights from a manikin study.

BACKGROUND/ AIM: To reduce the risk of fire, the ERC resuscitation guidelines recommend removing all oxygen-delivery devices at least 1 m away from the patient's chest prior to defibrillation. This recommendation is based on the assumption of relevant local oxygen accumulation. The presented study aimed to characterise ambient oxygen concentrations during cardiopulmonary resuscitation (CPR) and to assess the effect of removing oxygen-delivery devices.

METHODS

In a controlled mannequin-based simulation study, 20 resuscitation scenarios were performed under standardised conditions, varying oxygen delivery, airway management, ventilation mode, environment (room vs. ambulance), and distance of oxygen sources. Oxygen concentrations were continuously measured and recorded at 10-second intervals at three locations corresponding to typical defibrillation sites. Linear mixed-effects models were used to analyse predictors of oxygen fraction.

RESULTS

A total of 6,555 oxygen measurements were recorded. Median oxygen concentration was 21.6% (IQR 21.3-22.1%). Removing oxygen delivery devices to > 1 m did not result in lower oxygen concentrations compared with leaving them in proximity of the mannequin's head. Endotracheal intubation compared to an open airway and the use of an OxyDemand valve compared to a reservoir with 15 L/min oxygen flow were associated with slightly lower oxygen fractions, whereas other factors (handling of upper garments, site, use of mechanical CPR) showed no clinically relevant effects.

CONCLUSION

Clinically relevant oxygen accumulation at defibrillation sites was not observed. Likewise, removing oxygen-delivery devices did not result in a reduction in oxygen concentrations. Under the tested conditions, these findings do not support clinically relevant oxygen enrichment during CPR, questioning the risk of oxygen-enriched atmospheres during CPR as well as the role of routine removal of oxygen sources prior to defibrillation.