Uninterrupted chest compressions can improve the likelihood of a good outcome after cardiac arrest compared with standard CPR, a meta-analysis has shown.

The delivery of rescue breaths during CPR is time-consuming particularly for lay bystanders and prevents the maintenance of a continuous uninterrupted coronary perfusion pressure. The notion that rescue breaths may be detrimental to the success of adult CPR is not a new one and a recent meta-analysis published in The Lancet explored the current evidence.

The authors reviewed studies published over the past 25 years comparing chest compression only bystander CPR with standard CPR with ventilations for adults with prehospital cardiac arrest.

Two meta-analyses were performed. A primary analysis of three RCTs that randomised patients to receive one of the two CPR techniques according to dispatcher instructions and a secondary analysis looking at data from seven cohort studies of chest compression only prehospital CPR.

The primary analysis results showed that chest compression only CPR improved the chance of survival compared with standard CPR (14% vs. 12%; risk ratio 1.22), with an absolute increase in survival of 2.4%.

However, the secondary analysis of observational cohort studies found no difference in survival with the two CPR techniques, 8% for both.

The authors explain this dichotomy by the fact that none of the observational studies examined dispatcher-assisted CPR. The bystander rescuers decided to abandon ventilations on their own.

The authors therefore conclude that there is good evidence to support dispatcher-assisted compression only CPR.

It must be remembered that there are also several prospective cohort studies which support the use of standard CPR in cases of cardiac arrest caused by drowning, trauma, or asphyxia. There is not enough data on treating children with prehospital cardiac arrest but logic dictates that many of these arrests will be non-cardiac in origin and therefore rescue breaths are likely to have a role.

The takehome message is that emergency medical services dispatchers should instruct bystanders to focus on chest compression only CPR in adults with prehospital cardiac arrest. However, the situation for unassisted lay bystander CPR is unclear.

I was also interested to read that the American Heart Association is telling the public to remember CAB (Compressions Airway Breathing) rather than ABC.

Dr Peter Savill