The use of 100% compared to 50% oxygen during ineffective experimental cardiopulmonary resuscitation improves brain oxygenation

Introduction: Perfusion pressure and chest compression quality are generally considered key determinants of brain oxygenation during cardiopulmonary resuscitation (CPR) and the impact of oxygen administration is less clear. We compared ventilation with 100% and 50% oxygen during ineffective manual chest compressions and hypothesized that 100% oxygen would improve brain oxygenation.

Methods: Ventricular fibrillation (VF) was induced electrically in anaesthetized pigs and left untreated for 5 minutes, followed by randomization to ineffective manual CPR with ventilation of 50% or 100% oxygen. The first defibrillation was performed 10 minutes after induction of VF, and CPR continued with mechanical chest compressions (LUCAS2™) and defibrillation every 2 minutes until 36 minutes or return of spontaneous circulation (ROSC). Brain oxygenation was measured with near-infrared spectroscopy (rSO₂) and invasive brain tissue oxygen (PbtO₂) with a probe (NEUROVENT-PTO, RAUMEDIC) inserted into frontal brain tissue. Cerebral oxygenation was compared between groups with Mann-Whitney U tests and linear mixed models.

Results: Twenty-eight pigs were included in the study: 14 subjects in each group. During ineffective chest compressions relative PbtO₂ was higher in the group ventilated with 100% compared to 50% oxygen (5.2 mmHg [1.4-20.5] vs 2.2 [0.8-6.8], p = 0.001), but there was no difference in rSO₂ (22% [16-28] vs 18 [15-25], p = 0.090). The use of 50% or 100% oxygen showed no difference in relative PbtO₂ (p = 1.00) and rSO₂ (p = 0.206) during mechanical CPR.

Conclusions: The use of 100% compared to 50% oxygen during ineffective manual CPR improved brain oxygenation measured invasively in brain tissue, but there was no difference in rSO₂.