A brain oxygen level below 46% during CPR marks a physiological point of no return where resuscitation is no longer possible.
April 23, 2026
Original Paper
Regional Cerebral Oxygen Saturation as an Adjunctive Tool for Termination-of-Resuscitation Decisions in Out-of-Hospital Cardiac Arrest: A Prospective Observational Study
SSRN · 6621594
The Takeaway
Medical teams currently struggle with the agonizing decision of when to stop trying to revive a heart attack victim. Measuring regional cerebral oxygen saturation provides a real time window into whether the brain is still viable. A prospective study found that no patient falling below this specific threshold ever regained a pulse or consciousness. This tool gives doctors the data they need to stop chest compressions with near certainty when there is no longer any hope.
From the abstract
Background: Widely accepted in-hospital termination-of-resuscitation (TOR) rules are currently lacking, and existing approaches do not incorporate real-time physiological monitoring. Regional cerebral oxygen saturation (rSO₂) has been associated with return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR), but its role in TOR assessment remains unclear. Methods: In this prospective observational study, adult patients with out-of-hospital cardiac arrest who underwent r