When someone has a cardiac arrest, the actions of people nearby can make the difference between life and death. For years, the message has been clear: start cardiopulmonary resuscitation (CPR) as quickly as possible, even if you’ve never been trained.

That advice remains essential. But growing evidence suggests that how CPR is performed could also influence someone’s chances of survival.

Cardiac arrest happens when the heart suddenly stops pumping blood around the body, depriving the brain and other vital organs of oxygen. CPR involves pressing repeatedly on the chest to keep some blood circulating until emergency help arrives.

Starting CPR promptly can double or even triple someone’s chances of survival. Yet survival remains low. In England in 2024, only 9.5% of people survived for 30 days following an out-of-hospital cardiac arrest in which ambulance crews attempted resuscitation.

Survival depends on several factors, including how quickly CPR begins, whether the cardiac arrest is witnessed and whether a defibrillator is available. But researchers are increasingly interested in another question: how effectively are members of the public performing CPR before paramedics arrive?

A 2026 Australian study examined 17,715 out-of-hospital cardiac arrests in New South Wales between 2021 and 2024. Researchers found that patients who received CPR judged by paramedics to be good quality had substantially higher odds of surviving for 30 days than those who received no CPR.

CPR judged to be of a poor quality was not........

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