Compression-only CPR describes the performance of uninterrupted chest compressions without rescue breathing. In many adults who suffer a cardiac arrest, the heart stops abruptly; breathing will have been normal (or nearly normal), so the blood should be well oxygenated. In this situation, compression-only CPR may be effective for the first few minutes after the heart stops. This may provide time for the emergency services to arrive or an AED to be collected. Ultimately the oxygen will be used up and rescue breaths are required to give the victim the best chance of resuscitation.
Where a cardiac arrest is caused by lack of oxygen (as in drowning and most arrests that occur in children) compression-only CPR will be much less effective.
Chest compression alternating with rescue breaths is the ideal first aid procedure, but for untrained bystanders or those unwilling to give rescue breaths, compression-only CPR (hands only) is a useful alternative.