Bystander CPR more than doubles the chance of survival for victims of sudden cardiac arrest. Chest compressions are thought to be the most important component of CPR, but they are physically demanding.

The 'Heartstart Schools' training programme, developed by the British Heart Foundation, introduces chest compression at age 11, but the age at which children can perform effective chest compressions is not known.

So researchers in Cardiff, Wales investigated when children can provide effective chest compressions.

Children in three school year groups (ages 9-14) were taught basic life support as part of the Heartstart programme. The effectiveness of chest compressions was assessed during three minute's continuous chest compression on a manikin.

No year 5 pupil (age 9-10) was able to compress the manikin's chest to the depth recommended in guidelines - one and a half to two inches (38-51mm). Nineteen per cent of pupils in year 7 (age 11-12) and 45 per cent in year 9 (age 13-14) achieved adequate compression depth.

Only the 13-14 year olds performed chest compression as well as adults in other studies.

Although the younger children were not strong enough to compress the chest sufficiently, they learned the theory of the technique (correct hand position and correct rate of compressions) just as well as the older children.

This suggests that chest compressions can be introduced early in school CPR training programmes, say the authors.-BMJ-British Medical Journal